--- /srv/rebuilderd/tmp/rebuilderdpULp7J/inputs/erlang-doc_29.0~rc3+dfsg-1_all.deb
+++ /srv/rebuilderd/tmp/rebuilderdpULp7J/out/erlang-doc_29.0~rc3+dfsg-1_all.deb
├── file list
│ @@ -1,3 +1,3 @@
│  -rw-r--r--   0        0        0        4 2026-04-15 18:59:02.000000 debian-binary
│ --rw-r--r--   0        0        0    61052 2026-04-15 18:59:02.000000 control.tar.xz
│ --rw-r--r--   0        0        0 24936576 2026-04-15 18:59:02.000000 data.tar.xz
│ +-rw-r--r--   0        0        0    61056 2026-04-15 18:59:02.000000 control.tar.xz
│ +-rw-r--r--   0        0        0 24936212 2026-04-15 18:59:02.000000 data.tar.xz
├── control.tar.xz
│ ├── control.tar
│ │ ├── ./md5sums
│ │ │ ├── ./md5sums
│ │ │ │┄ Files differ
│ │ │ ├── line order
│ │ │ │ @@ -814,15 +814,15 @@
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ │ -usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/search_data-4CDEAB42.js
│ │ │ │ +usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/search_data-311DD30B.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/sidebar_items-2D7BEBEB.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/ftp.epub
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/ftp.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/ftp_client.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/index.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/introduction.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/notes.html
│ │ │ │ @@ -1244,15 +1244,15 @@
│ │ │ │  usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ │ -usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/search_data-62376163.js
│ │ │ │ +usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/search_data-A2F66A60.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/sidebar_items-C4781606.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/index.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/megaco.epub
│ │ │ │  usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/megaco.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/megaco_architecture.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/megaco_codec_meas.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/megaco_codec_mstone1.html
│ │ │ │ @@ -1581,15 +1581,15 @@
│ │ │ │  usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ │ -usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/search_data-D13A7ABE.js
│ │ │ │ +usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/search_data-AA86FF31.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/sidebar_items-77A3D458.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dtrace.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dyntrace.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/index.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/instrument.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/lttng.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/msacc.html
│ │ │ │ @@ -1770,15 +1770,15 @@
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ │ -usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/search_data-118FFFFC.js
│ │ │ │ +usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/search_data-E0CE4C2F.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/sidebar_items-93509C6F.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/hardening.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/index.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/introduction.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/notes.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/search.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/ssh.epub
│ │ │ │ @@ -1875,15 +1875,15 @@
│ │ │ │  usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ │ -usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/search_data-7E77D3EA.js
│ │ │ │ +usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/search_data-16FF2648.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/sidebar_items-F80C2F06.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/edlin.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/edlin_expand.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/epp.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/erl_anno.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/erl_error.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/erl_eval.html
├── data.tar.xz
│ ├── data.tar
│ │ ├── file list
│ │ │ @@ -141,15 +141,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)      287 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/doc/ssh.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      288 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/doc/ssl.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      290 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/doc/stdlib.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      296 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/doc/syntax_tools.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/doc/system/
│ │ │  -rw-r--r--   0 root         (0) root         (0)     2392 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/doc/system/.build
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5648 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/doc/system/404.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)   805598 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/doc/system/Erlang System Documentation.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   805612 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/doc/system/Erlang System Documentation.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)    53684 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/doc/system/applications.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    97565 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/doc/system/appup_cookbook.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/doc/system/assets/
│ │ │  -rw-r--r--   0 root         (0) root         (0)     7982 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/doc/system/assets/ballpoint-pen.svg
│ │ │  -rw-r--r--   0 root         (0) root         (0)     2284 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/doc/system/assets/dist1.gif
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5214 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/doc/system/assets/dist2.gif
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5007 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/doc/system/assets/dist3.gif
│ │ │ @@ -411,15 +411,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)    11077 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.31/doc/html/api-reference.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.31/doc/html/assets/
│ │ │  -rw-r--r--   0 root         (0) root         (0)     4963 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.31/doc/html/assets/config.gif
│ │ │  -rw-r--r--   0 root         (0) root         (0)    10726 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.31/doc/html/assets/html_logs.gif
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5837 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.31/doc/html/assets/logo.png
│ │ │  -rw-r--r--   0 root         (0) root         (0)     9561 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.31/doc/html/assets/tc_execution.gif
│ │ │  -rw-r--r--   0 root         (0) root         (0)    21789 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.31/doc/html/basics_chapter.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)   411864 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.31/doc/html/common_test.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   411848 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.31/doc/html/common_test.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)     7496 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.31/doc/html/common_test_app.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    59620 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.31/doc/html/config_file_chapter.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    25535 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.31/doc/html/cover_chapter.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   182313 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.31/doc/html/ct.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    12266 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.31/doc/html/ct_cover.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    48059 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.31/doc/html/ct_doctest.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    33479 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.31/doc/html/ct_ftp.html
│ │ │ @@ -481,15 +481,15 @@
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-10.0/doc/html/assets/
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5837 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-10.0/doc/html/assets/logo.png
│ │ │  -rw-r--r--   0 root         (0) root         (0)    24217 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-10.0/doc/html/beam_ssa.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   472387 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-10.0/doc/html/cerl.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    28678 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-10.0/doc/html/cerl_clauses.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    28900 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-10.0/doc/html/cerl_trees.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    92536 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-10.0/doc/html/compile.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)   203383 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-10.0/doc/html/compiler.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   203380 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-10.0/doc/html/compiler.epub
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-10.0/doc/html/dist/
│ │ │  -rw-r--r--   0 root         (0) root         (0)    20933 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-10.0/doc/html/dist/handlebars.runtime-CFQAK6SD.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    33580 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-10.0/doc/html/dist/handlebars.templates-K7URE6B4.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    70589 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-10.0/doc/html/dist/html-55NP3CS6.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    67213 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-10.0/doc/html/dist/html-erlang-WGRVP7UZ.css
│ │ │  -rw-r--r--   0 root         (0) root         (0)    17732 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-10.0/doc/html/dist/inconsolata-latin-400-normal-OXLHDACS.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    17976 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-10.0/doc/html/dist/inconsolata-latin-700-normal-S55P5GAG.woff2
│ │ │ @@ -515,15 +515,15 @@
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.9/doc/html/
│ │ │  -rw-r--r--   0 root         (0) root         (0)      978 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.9/doc/html/.build
│ │ │  -rw-r--r--   0 root         (0) root         (0)     6010 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.9/doc/html/404.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    36793 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.9/doc/html/algorithm_details.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     6662 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.9/doc/html/api-reference.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.9/doc/html/assets/
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5837 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.9/doc/html/assets/logo.png
│ │ │ --rw-r--r--   0 root         (0) root         (0)   140721 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.9/doc/html/crypto.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   140720 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.9/doc/html/crypto.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)   357300 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.9/doc/html/crypto.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    11222 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.9/doc/html/crypto_app.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.9/doc/html/dist/
│ │ │  -rw-r--r--   0 root         (0) root         (0)    20933 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.9/doc/html/dist/handlebars.runtime-CFQAK6SD.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    33580 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.9/doc/html/dist/handlebars.templates-K7URE6B4.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    70589 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.9/doc/html/dist/html-55NP3CS6.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    67213 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.9/doc/html/dist/html-erlang-WGRVP7UZ.css
│ │ │ @@ -560,15 +560,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)    21770 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/debugger-7.0/doc/html/assets/cond_break_dialog.jpg
│ │ │  -rw-r--r--   0 root         (0) root         (0)    13532 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/debugger-7.0/doc/html/assets/function_break_dialog.jpg
│ │ │  -rw-r--r--   0 root         (0) root         (0)    28924 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/debugger-7.0/doc/html/assets/interpret.jpg
│ │ │  -rw-r--r--   0 root         (0) root         (0)    14414 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/debugger-7.0/doc/html/assets/line_break_dialog.jpg
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5837 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/debugger-7.0/doc/html/assets/logo.png
│ │ │  -rw-r--r--   0 root         (0) root         (0)    40742 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/debugger-7.0/doc/html/assets/monitor.jpg
│ │ │  -rw-r--r--   0 root         (0) root         (0)    34504 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/debugger-7.0/doc/html/assets/view.jpg
│ │ │ --rw-r--r--   0 root         (0) root         (0)   222108 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/debugger-7.0/doc/html/debugger.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   222104 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/debugger-7.0/doc/html/debugger.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)    13075 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/debugger-7.0/doc/html/debugger.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    52058 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/debugger-7.0/doc/html/debugger_chapter.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/debugger-7.0/doc/html/dist/
│ │ │  -rw-r--r--   0 root         (0) root         (0)    20933 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/debugger-7.0/doc/html/dist/handlebars.runtime-CFQAK6SD.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    33580 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/debugger-7.0/doc/html/dist/handlebars.templates-K7URE6B4.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    70589 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/debugger-7.0/doc/html/dist/html-55NP3CS6.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    67213 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/debugger-7.0/doc/html/dist/html-erlang-WGRVP7UZ.css
│ │ │ @@ -597,15 +597,15 @@
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/dialyzer-6.0/doc/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/dialyzer-6.0/doc/html/
│ │ │  -rw-r--r--   0 root         (0) root         (0)      921 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/dialyzer-6.0/doc/html/.build
│ │ │  -rw-r--r--   0 root         (0) root         (0)     6022 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/dialyzer-6.0/doc/html/404.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     6786 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/dialyzer-6.0/doc/html/api-reference.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/dialyzer-6.0/doc/html/assets/
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5837 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/dialyzer-6.0/doc/html/assets/logo.png
│ │ │ --rw-r--r--   0 root         (0) root         (0)    69052 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/dialyzer-6.0/doc/html/dialyzer.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)    69057 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/dialyzer-6.0/doc/html/dialyzer.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)    53565 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/dialyzer-6.0/doc/html/dialyzer.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    25892 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/dialyzer-6.0/doc/html/dialyzer_chapter.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/dialyzer-6.0/doc/html/dist/
│ │ │  -rw-r--r--   0 root         (0) root         (0)    20933 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/dialyzer-6.0/doc/html/dist/handlebars.runtime-CFQAK6SD.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    33580 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/dialyzer-6.0/doc/html/dist/handlebars.templates-K7URE6B4.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    70589 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/dialyzer-6.0/doc/html/dist/html-55NP3CS6.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    67213 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/dialyzer-6.0/doc/html/dist/html-erlang-WGRVP7UZ.css
│ │ │ @@ -650,15 +650,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)     2379 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/diameter-2.7/doc/examples/dict/rfc4740_sip.dia.gz
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/diameter-2.7/doc/html/
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1143 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/diameter-2.7/doc/html/.build
│ │ │  -rw-r--r--   0 root         (0) root         (0)     6022 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/diameter-2.7/doc/html/404.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     8206 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/diameter-2.7/doc/html/api-reference.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/diameter-2.7/doc/html/assets/
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5837 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/diameter-2.7/doc/html/assets/logo.png
│ │ │ --rw-r--r--   0 root         (0) root         (0)   149019 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/diameter-2.7/doc/html/diameter.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   149015 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/diameter-2.7/doc/html/diameter.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)   253460 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/diameter-2.7/doc/html/diameter.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    57499 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/diameter-2.7/doc/html/diameter_app.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    27922 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/diameter-2.7/doc/html/diameter_codec.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    34940 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/diameter-2.7/doc/html/diameter_dict.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     6772 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/diameter-2.7/doc/html/diameter_examples.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     9512 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/diameter-2.7/doc/html/diameter_intro.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23265 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/diameter-2.7/doc/html/diameter_make.html
│ │ │ @@ -784,15 +784,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23040 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eldap-1.3/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5624 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eldap-1.3/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5472 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eldap-1.3/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5368 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eldap-1.3/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1956 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eldap-1.3/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    26583 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eldap-1.3/doc/html/dist/search_data-E0177CFA.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)     6179 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eldap-1.3/doc/html/dist/sidebar_items-14671279.js
│ │ │ --rw-r--r--   0 root         (0) root         (0)    33489 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eldap-1.3/doc/html/eldap.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)    33486 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eldap-1.3/doc/html/eldap.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)    94377 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eldap-1.3/doc/html/eldap.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      261 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eldap-1.3/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    28399 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eldap-1.3/doc/html/notes.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5920 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eldap-1.3/doc/html/search.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/erl_interface-5.7/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/erl_interface-5.7/doc/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/erl_interface-5.7/doc/html/
│ │ │ @@ -821,15 +821,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)   199647 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/erl_interface-5.7/doc/html/dist/search_data-1374700A.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    16288 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/erl_interface-5.7/doc/html/dist/sidebar_items-5DE9DFF9.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    73718 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/erl_interface-5.7/doc/html/ei.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    72769 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/erl_interface-5.7/doc/html/ei_connect.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    11729 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/erl_interface-5.7/doc/html/ei_global.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    26962 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/erl_interface-5.7/doc/html/ei_users_guide.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    22654 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/erl_interface-5.7/doc/html/erl_call_cmd.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)    86613 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/erl_interface-5.7/doc/html/erl_interface.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)    86617 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/erl_interface-5.7/doc/html/erl_interface.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)      270 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/erl_interface-5.7/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   119876 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/erl_interface-5.7/doc/html/notes.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5559 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/erl_interface-5.7/doc/html/search.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/examples/
│ │ │  -rw-r--r--   0 root         (0) root         (0)    15431 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/examples/et_demo.erl
│ │ │ @@ -868,15 +868,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23040 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5624 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5472 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5368 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1956 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    83801 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/html/dist/search_data-12B7FA19.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)     9353 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/html/dist/sidebar_items-952B1C2C.js
│ │ │ --rw-r--r--   0 root         (0) root         (0)   303465 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/html/et.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   303477 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/html/et.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)    22745 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/html/et.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    56797 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/html/et_collector.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    52810 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/html/et_desc.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   100660 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/html/et_examples.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     9902 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/html/et_intro.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    20249 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/html/et_selector.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    45772 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/et-1.8/doc/html/et_tutorial.html
│ │ │ @@ -912,15 +912,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23040 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eunit-2.11/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5624 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eunit-2.11/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5472 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eunit-2.11/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5368 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eunit-2.11/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1956 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eunit-2.11/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    85206 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eunit-2.11/doc/html/dist/search_data-A1AE6A4D.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)     3265 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eunit-2.11/doc/html/dist/sidebar_items-F9DCA965.js
│ │ │ --rw-r--r--   0 root         (0) root         (0)    49115 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eunit-2.11/doc/html/eunit.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)    49116 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eunit-2.11/doc/html/eunit.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)    13555 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eunit-2.11/doc/html/eunit.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     6630 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eunit-2.11/doc/html/eunit_surefire.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      262 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eunit-2.11/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    50523 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eunit-2.11/doc/html/notes.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5923 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/eunit-2.11/doc/html/search.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/
│ │ │ @@ -944,15 +944,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23236 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23580 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23040 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5624 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5472 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5368 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1956 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ --rw-r--r--   0 root         (0) root         (0)    30562 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/search_data-4CDEAB42.js
│ │ │ +-rw-r--r--   0 root         (0) root         (0)    30562 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/search_data-311DD30B.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5312 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/dist/sidebar_items-2D7BEBEB.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    36914 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/ftp.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)   100195 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/ftp.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    12856 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/ftp_client.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      261 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     7162 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/introduction.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    24184 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ftp-1.2.5/doc/html/notes.html
│ │ │ @@ -1117,15 +1117,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)    11377 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/inets-9.7/doc/html/http_uri.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    92071 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/inets-9.7/doc/html/httpc.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   119541 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/inets-9.7/doc/html/httpd.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    12076 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/inets-9.7/doc/html/httpd_custom_api.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    13391 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/inets-9.7/doc/html/httpd_socket.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    44888 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/inets-9.7/doc/html/httpd_util.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      261 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/inets-9.7/doc/html/index.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)   161058 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/inets-9.7/doc/html/inets.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   161056 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/inets-9.7/doc/html/inets.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)    25609 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/inets-9.7/doc/html/inets.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     8647 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/inets-9.7/doc/html/inets_services.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     7454 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/inets-9.7/doc/html/introduction.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    21176 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/inets-9.7/doc/html/mod_alias.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    82372 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/inets-9.7/doc/html/mod_auth.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    21842 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/inets-9.7/doc/html/mod_esi.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    36914 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/inets-9.7/doc/html/mod_security.html
│ │ │ @@ -1363,15 +1363,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)    57052 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/kernel-11.0/doc/html/global.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    37162 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/kernel-11.0/doc/html/global_group.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    24939 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/kernel-11.0/doc/html/heart.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      263 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/kernel-11.0/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   183978 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/kernel-11.0/doc/html/inet.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    94509 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/kernel-11.0/doc/html/inet_res.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     7721 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/kernel-11.0/doc/html/introduction_chapter.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)   847813 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/kernel-11.0/doc/html/kernel.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   847820 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/kernel-11.0/doc/html/kernel.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)    43555 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/kernel-11.0/doc/html/kernel_app.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   187933 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/kernel-11.0/doc/html/logger.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   110886 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/kernel-11.0/doc/html/logger_chapter.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    70805 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/kernel-11.0/doc/html/logger_cookbook.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    15633 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/kernel-11.0/doc/html/logger_disk_log_h.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    25604 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/kernel-11.0/doc/html/logger_filters.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    34063 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/kernel-11.0/doc/html/logger_formatter.html
│ │ │ @@ -1428,15 +1428,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23236 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23580 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23040 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5624 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5472 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5368 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1956 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ --rw-r--r--   0 root         (0) root         (0)   213955 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/search_data-62376163.js
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   213955 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/search_data-A2F66A60.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    33651 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/dist/sidebar_items-C4781606.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)      262 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   147235 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/megaco.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)   198731 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/megaco.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    17696 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/megaco_architecture.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     9834 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/megaco_codec_meas.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    26192 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/megaco-4.9/doc/html/megaco_codec_mstone1.html
│ │ │ @@ -1511,15 +1511,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5624 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/mnesia-4.26/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5472 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/mnesia-4.26/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5368 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/mnesia-4.26/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1956 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/mnesia-4.26/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)   388686 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/mnesia-4.26/doc/html/dist/search_data-2D33460F.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    25859 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/mnesia-4.26/doc/html/dist/sidebar_items-B6E0F975.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)      263 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/mnesia-4.26/doc/html/index.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)   227766 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/mnesia-4.26/doc/html/mnesia.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   227776 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/mnesia-4.26/doc/html/mnesia.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)   342526 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/mnesia-4.26/doc/html/mnesia.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    45462 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/mnesia-4.26/doc/html/mnesia_app_a.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    90426 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/mnesia-4.26/doc/html/mnesia_app_b.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    46054 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/mnesia-4.26/doc/html/mnesia_app_c.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     9863 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/mnesia-4.26/doc/html/mnesia_chap1.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   109242 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/mnesia-4.26/doc/html/mnesia_chap2.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    51388 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/mnesia-4.26/doc/html/mnesia_chap3.html
│ │ │ @@ -1567,15 +1567,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)   150971 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/observer-2.19/doc/html/dist/search_data-1305868C.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    12965 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/observer-2.19/doc/html/dist/sidebar_items-58F82598.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    17922 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/observer-2.19/doc/html/etop.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    15742 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/observer-2.19/doc/html/etop_ug.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      265 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/observer-2.19/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     7350 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/observer-2.19/doc/html/introduction_ug.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    77604 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/observer-2.19/doc/html/notes.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)   118781 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/observer-2.19/doc/html/observer.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   118783 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/observer-2.19/doc/html/observer.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)    13881 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/observer-2.19/doc/html/observer.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     7238 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/observer-2.19/doc/html/observer_app.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23444 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/observer-2.19/doc/html/observer_ug.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5941 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/observer-2.19/doc/html/search.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   111527 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/observer-2.19/doc/html/ttb.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   165958 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/observer-2.19/doc/html/ttb_ug.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/odbc-2.17/
│ │ │ @@ -1609,15 +1609,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)    80050 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/odbc-2.17/doc/html/dist/search_data-8D6ABF37.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)     7442 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/odbc-2.17/doc/html/dist/sidebar_items-322DE651.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    13859 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/odbc-2.17/doc/html/error_handling.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    51373 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/odbc-2.17/doc/html/getting_started.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      261 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/odbc-2.17/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     8466 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/odbc-2.17/doc/html/introduction.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    62027 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/odbc-2.17/doc/html/notes.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)    70076 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/odbc-2.17/doc/html/odbc.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)    70074 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/odbc-2.17/doc/html/odbc.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)    87515 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/odbc-2.17/doc/html/odbc.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5917 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/odbc-2.17/doc/html/search.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/os_mon-2.12/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/os_mon-2.12/doc/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/os_mon-2.12/doc/html/
│ │ │  -rw-r--r--   0 root         (0) root         (0)      952 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/os_mon-2.12/doc/html/.build
│ │ │  -rw-r--r--   0 root         (0) root         (0)     6013 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/os_mon-2.12/doc/html/404.html
│ │ │ @@ -1681,15 +1681,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5368 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/parsetools-2.8/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1956 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/parsetools-2.8/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    59376 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/parsetools-2.8/doc/html/dist/search_data-F5FAE48C.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5788 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/parsetools-2.8/doc/html/dist/sidebar_items-4228A8DE.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)      266 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/parsetools-2.8/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    55377 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/parsetools-2.8/doc/html/leex.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    45293 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/parsetools-2.8/doc/html/notes.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)    46411 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/parsetools-2.8/doc/html/parsetools.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)    46404 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/parsetools-2.8/doc/html/parsetools.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5950 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/parsetools-2.8/doc/html/search.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    67783 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/parsetools-2.8/doc/html/yecc.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/html/
│ │ │  -rw-r--r--   0 root         (0) root         (0)      952 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/html/.build
│ │ │  -rw-r--r--   0 root         (0) root         (0)     6037 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/html/404.html
│ │ │ @@ -1714,15 +1714,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5472 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5368 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1956 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)   159405 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/html/dist/search_data-6689052C.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    17735 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/html/dist/sidebar_items-3F271350.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)      267 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   106876 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/html/notes.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)   106038 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/html/public_key.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   106035 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/html/public_key.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)   214724 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/html/public_key.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    10613 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/html/public_key_app.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    74413 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/html/public_key_records.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5953 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/html/search.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   131319 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/public_key-1.21/doc/html/using_public_key.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/reltool-1.1/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/reltool-1.1/doc/
│ │ │ @@ -1753,15 +1753,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5472 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/reltool-1.1/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5368 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/reltool-1.1/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1956 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/reltool-1.1/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    94042 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/reltool-1.1/doc/html/dist/search_data-E3ED7B7B.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)     8980 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/reltool-1.1/doc/html/dist/sidebar_items-B51BD5DF.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)      263 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/reltool-1.1/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    51499 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/reltool-1.1/doc/html/notes.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)    64542 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/reltool-1.1/doc/html/reltool.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)    64547 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/reltool-1.1/doc/html/reltool.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)   100508 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/reltool-1.1/doc/html/reltool.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   200344 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/reltool-1.1/doc/html/reltool_examples.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     9362 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/reltool-1.1/doc/html/reltool_intro.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23132 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/reltool-1.1/doc/html/reltool_usage.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5932 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/reltool-1.1/doc/html/search.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/
│ │ │ @@ -1810,24 +1810,24 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23236 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23580 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23040 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5624 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5472 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5368 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1956 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ --rw-r--r--   0 root         (0) root         (0)   195211 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/search_data-D13A7ABE.js
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   195211 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/search_data-AA86FF31.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    18805 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dist/sidebar_items-77A3D458.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)     9768 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dtrace.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    47608 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/dyntrace.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      269 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    50748 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/instrument.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    64733 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/lttng.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    49987 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/msacc.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    90165 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/notes.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)   136500 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/runtime_tools.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   136493 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/runtime_tools.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)     7578 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/runtime_tools_app.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    29007 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/scheduler.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5968 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/search.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    12883 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/system_information.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    10216 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/runtime_tools-2.4/doc/html/systemtap.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/sasl-4.4/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/sasl-4.4/doc/
│ │ │ @@ -1868,15 +1868,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)    34632 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/sasl-4.4/doc/html/error_logging.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      260 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/sasl-4.4/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    77807 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/sasl-4.4/doc/html/notes.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    42342 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/sasl-4.4/doc/html/rb.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    12206 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/sasl-4.4/doc/html/rel.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    80220 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/sasl-4.4/doc/html/release_handler.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     9567 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/sasl-4.4/doc/html/relup.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)    94197 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/sasl-4.4/doc/html/sasl.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)    94192 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/sasl-4.4/doc/html/sasl.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)    17143 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/sasl-4.4/doc/html/sasl_app.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     7693 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/sasl-4.4/doc/html/sasl_intro.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    17239 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/sasl-4.4/doc/html/script.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5914 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/sasl-4.4/doc/html/search.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    40261 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/sasl-4.4/doc/html/systools.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/doc/
│ │ │ @@ -1937,15 +1937,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5368 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1956 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)   559580 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/doc/html/dist/search_data-B3816D8C.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    89974 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/doc/html/dist/sidebar_items-A1C37470.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)      263 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    74993 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/doc/html/notes.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5923 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/doc/html/search.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)   451466 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/doc/html/snmp.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   451500 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/doc/html/snmp.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)   147483 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/doc/html/snmp.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    39983 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/doc/html/snmp_advanced_agent.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    62877 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/doc/html/snmp_agent_config_files.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    51341 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/doc/html/snmp_agent_funct_descr.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    18119 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/doc/html/snmp_agent_netif.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    66597 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/doc/html/snmp_app.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     8609 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/snmp-5.20.3/doc/html/snmp_app_a.html
│ │ │ @@ -2020,22 +2020,22 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23236 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23580 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23040 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5624 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5472 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5368 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1956 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ --rw-r--r--   0 root         (0) root         (0)   408275 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/search_data-118FFFFC.js
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   408275 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/search_data-E0CE4C2F.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    48336 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/dist/sidebar_items-93509C6F.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    52039 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/hardening.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      259 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    14405 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/introduction.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   269599 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/notes.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5908 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/search.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)   259259 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/ssh.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   259248 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/ssh.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)   266133 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/ssh.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    24735 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/ssh_agent.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    25836 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/ssh_app.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    44535 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/ssh_client_channel.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23183 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/ssh_client_key_api.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    78519 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/ssh_connection.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    50564 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssh-6.0/doc/html/ssh_file.html
│ │ │ @@ -2092,15 +2092,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5368 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssl-11.6/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1956 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssl-11.6/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)   510294 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssl-11.6/doc/html/dist/search_data-976A26A2.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    28303 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssl-11.6/doc/html/dist/sidebar_items-2CDF1A40.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)      260 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssl-11.6/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   287679 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssl-11.6/doc/html/notes.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5911 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssl-11.6/doc/html/search.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)   220346 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssl-11.6/doc/html/ssl.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   220338 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssl-11.6/doc/html/ssl.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)   331440 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssl-11.6/doc/html/ssl.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    17335 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssl-11.6/doc/html/ssl_app.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    12854 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssl-11.6/doc/html/ssl_crl_cache.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    21688 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssl-11.6/doc/html/ssl_crl_cache_api.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    29623 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssl-11.6/doc/html/ssl_distribution.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    14198 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssl-11.6/doc/html/ssl_protocol.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    25827 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/ssl-11.6/doc/html/ssl_session_cache_api.html
│ │ │ @@ -2145,15 +2145,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23236 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23580 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23040 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5624 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5472 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5368 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1956 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ --rw-r--r--   0 root         (0) root         (0)  2209626 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/search_data-7E77D3EA.js
│ │ │ +-rw-r--r--   0 root         (0) root         (0)  2209626 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/search_data-16FF2648.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)   276640 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/dist/sidebar_items-F80C2F06.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    18671 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/edlin.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    15220 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/edlin_expand.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    52673 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/epp.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    42699 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/erl_anno.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    33744 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/erl_error.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    57418 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/erl_eval.html
│ │ │ @@ -2207,15 +2207,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5926 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/search.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   110942 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/sets.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   110236 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/shell.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    10133 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/shell_default.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    49860 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/shell_docs.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    33169 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/slave.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   503109 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/sofs.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)  1743015 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/stdlib.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)  1742975 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/stdlib.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)    16124 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/stdlib_app.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   191936 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/string.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   100472 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/supervisor.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    20517 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/supervisor_bridge.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   106837 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/sys.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    34820 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/terminal_interface.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    81120 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/stdlib-8.0/doc/html/timer.html
│ │ │ @@ -2299,15 +2299,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)    31548 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tftp-1.3/doc/html/dist/search_data-4456E8EA.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)     3329 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tftp-1.3/doc/html/dist/sidebar_items-65ADE05C.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    10545 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tftp-1.3/doc/html/getting_started.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      260 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tftp-1.3/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     8806 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tftp-1.3/doc/html/introduction.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23156 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tftp-1.3/doc/html/notes.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5914 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tftp-1.3/doc/html/search.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)    31995 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tftp-1.3/doc/html/tftp.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)    31994 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tftp-1.3/doc/html/tftp.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)    45783 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tftp-1.3/doc/html/tftp.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    11721 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tftp-1.3/doc/html/tftp_logger.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tools-4.2/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tools-4.2/doc/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tools-4.2/doc/examples/
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1447 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tools-4.2/doc/examples/xref_examples.erl
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tools-4.2/doc/html/
│ │ │ @@ -2350,15 +2350,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)      261 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tools-4.2/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    66036 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tools-4.2/doc/html/lcnt.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    53457 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tools-4.2/doc/html/lcnt_chapter.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    18377 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tools-4.2/doc/html/make.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   116266 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tools-4.2/doc/html/notes.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5920 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tools-4.2/doc/html/search.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    28511 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tools-4.2/doc/html/tags.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)   242436 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tools-4.2/doc/html/tools.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   242451 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tools-4.2/doc/html/tools.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)   173622 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tools-4.2/doc/html/tprof.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   192203 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tools-4.2/doc/html/xref.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    39571 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/tools-4.2/doc/html/xref_chapter.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/examples/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/examples/demo/
│ │ │ @@ -2451,15 +2451,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)  1672717 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/html/dist/search_data-A7576480.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)   578947 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/html/dist/sidebar_items-631B9BA1.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)  1720063 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/html/gl.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    77248 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/html/glu.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      258 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/html/index.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    69962 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/html/notes.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5902 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/html/search.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)  1609738 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/html/wx.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)  1609740 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/html/wx.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)    53710 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/html/wx.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    19399 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/html/wxAcceleratorEntry.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    15114 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/html/wxAcceleratorTable.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    12357 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/html/wxActivateEvent.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    19080 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/html/wxArtProvider.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    17602 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/html/wxAuiDockArt.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    62907 2026-04-15 18:59:02.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.6/doc/html/wxAuiManager.html
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/Erlang System Documentation.epub
│ │ │ ├── zipinfo {}
│ │ │ │ @@ -1,99 +1,99 @@
│ │ │ │ -Zip file size: 805598 bytes, number of entries: 97
│ │ │ │ -?rw-r--r--  6.1 unx       20 bx stor 26-Apr-15 20:07 mimetype
│ │ │ │ -?rw-r--r--  6.1 unx    14643 bx defN 26-Apr-15 20:07 OEBPS/vulnerabilities.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    17925 bx defN 26-Apr-15 20:07 OEBPS/versions.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     4673 bx defN 26-Apr-15 20:07 OEBPS/upgrade.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    54465 bx defN 26-Apr-15 20:07 OEBPS/typespec.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     2166 bx defN 26-Apr-15 20:07 OEBPS/tutorial.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx      764 bx defN 26-Apr-15 20:07 OEBPS/title.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    46257 bx defN 26-Apr-15 20:07 OEBPS/tablesdatabases.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    12439 bx defN 26-Apr-15 20:07 OEBPS/system_principles.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     7481 bx defN 26-Apr-15 20:07 OEBPS/system_limits.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    63519 bx defN 26-Apr-15 20:07 OEBPS/sup_princ.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx   254168 bx defN 26-Apr-15 20:07 OEBPS/statem.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx   111649 bx defN 26-Apr-15 20:07 OEBPS/spec_proc.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx   252881 bx defN 26-Apr-15 20:07 OEBPS/seq_prog.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx   163061 bx defN 26-Apr-15 20:07 OEBPS/secure_coding.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    15505 bx defN 26-Apr-15 20:07 OEBPS/sbom.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    70567 bx defN 26-Apr-15 20:07 OEBPS/robustness.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    20877 bx defN 26-Apr-15 20:07 OEBPS/release_structure.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    59979 bx defN 26-Apr-15 20:07 OEBPS/release_handling.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     4595 bx defN 26-Apr-15 20:07 OEBPS/reference_manual.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    19454 bx defN 26-Apr-15 20:07 OEBPS/ref_man_records.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    54417 bx defN 26-Apr-15 20:07 OEBPS/ref_man_processes.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    14474 bx defN 26-Apr-15 20:07 OEBPS/ref_man_functions.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    49208 bx defN 26-Apr-15 20:07 OEBPS/records_macros.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     2357 bx defN 26-Apr-15 20:07 OEBPS/readme.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx      785 bx defN 26-Apr-15 20:07 OEBPS/programming_examples.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    40219 bx defN 26-Apr-15 20:07 OEBPS/prog_ex_records.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    15192 bx defN 26-Apr-15 20:07 OEBPS/profiling.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     8499 bx defN 26-Apr-15 20:07 OEBPS/ports.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     3852 bx defN 26-Apr-15 20:07 OEBPS/patterns.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    13419 bx defN 26-Apr-15 20:07 OEBPS/overview.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     8959 bx defN 26-Apr-15 20:07 OEBPS/otp-patch-apply.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    10050 bx defN 26-Apr-15 20:07 OEBPS/opaques.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    15633 bx defN 26-Apr-15 20:07 OEBPS/nominals.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    14148 bx defN 26-Apr-15 20:07 OEBPS/nif.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     6852 bx defN 26-Apr-15 20:07 OEBPS/nav.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    25870 bx defN 26-Apr-15 20:07 OEBPS/modules.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     7018 bx defN 26-Apr-15 20:07 OEBPS/misc.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     5477 bx defN 26-Apr-15 20:07 OEBPS/memory.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    53379 bx defN 26-Apr-15 20:07 OEBPS/maps.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    39594 bx defN 26-Apr-15 20:07 OEBPS/macros.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    31440 bx defN 26-Apr-15 20:07 OEBPS/listhandling.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    53789 bx defN 26-Apr-15 20:07 OEBPS/list_comprehensions.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     2211 bx defN 26-Apr-15 20:07 OEBPS/installation_guide.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    57455 bx defN 26-Apr-15 20:07 OEBPS/install.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    28229 bx defN 26-Apr-15 20:07 OEBPS/install-win32.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    35715 bx defN 26-Apr-15 20:07 OEBPS/install-cross.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    21439 bx defN 26-Apr-15 20:07 OEBPS/included_applications.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     3222 bx defN 26-Apr-15 20:07 OEBPS/howto_debug.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     2353 bx defN 26-Apr-15 20:07 OEBPS/getting_started.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    31366 bx defN 26-Apr-15 20:07 OEBPS/gen_server_concepts.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx   119139 bx defN 26-Apr-15 20:07 OEBPS/funs.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     8680 bx defN 26-Apr-15 20:07 OEBPS/features.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx   268117 bx defN 26-Apr-15 20:07 OEBPS/expressions.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     2365 bx defN 26-Apr-15 20:07 OEBPS/example.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    26770 bx defN 26-Apr-15 20:07 OEBPS/events.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    16719 bx defN 26-Apr-15 20:07 OEBPS/errors.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     4519 bx defN 26-Apr-15 20:07 OEBPS/error_logging.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    42616 bx defN 26-Apr-15 20:07 OEBPS/erl_interface.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    18220 bx defN 26-Apr-15 20:07 OEBPS/embedded.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     2085 bx defN 26-Apr-15 20:07 OEBPS/efficiency_guide.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    46685 bx defN 26-Apr-15 20:07 OEBPS/eff_guide_processes.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    21210 bx defN 26-Apr-15 20:07 OEBPS/eff_guide_functions.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     9338 bx defN 26-Apr-15 20:07 OEBPS/drivers.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    47780 bx defN 26-Apr-15 20:07 OEBPS/documentation.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    14895 bx defN 26-Apr-15 20:07 OEBPS/distributed_applications.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    24447 bx defN 26-Apr-15 20:07 OEBPS/distributed.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    14562 bx defN 26-Apr-15 20:07 OEBPS/dist/epub-erlang-ESPT6BQV.css
│ │ │ │ -?rw-r--r--  6.1 unx      499 bx defN 26-Apr-15 20:07 OEBPS/dist/epub-LSJCIYTM.js
│ │ │ │ -?rw-r--r--  6.1 unx    36776 bx defN 26-Apr-15 20:07 OEBPS/design_principles.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    15003 bx defN 26-Apr-15 20:07 OEBPS/debugging.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    78764 bx defN 26-Apr-15 20:07 OEBPS/data_types.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx   116619 bx defN 26-Apr-15 20:07 OEBPS/create_target.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    14028 bx defN 26-Apr-15 20:07 OEBPS/content.opf
│ │ │ │ -?rw-r--r--  6.1 unx   129434 bx defN 26-Apr-15 20:07 OEBPS/conc_prog.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    35528 bx defN 26-Apr-15 20:07 OEBPS/commoncaveats.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    11940 bx defN 26-Apr-15 20:07 OEBPS/code_loading.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx      803 bx defN 26-Apr-15 20:07 OEBPS/cnode.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     5151 bx defN 26-Apr-15 20:07 OEBPS/character_set.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    40799 bx defN 26-Apr-15 20:07 OEBPS/c_portdriver.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    35602 bx defN 26-Apr-15 20:07 OEBPS/c_port.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    34851 bx defN 26-Apr-15 20:07 OEBPS/bit_syntax.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    53327 bx defN 26-Apr-15 20:07 OEBPS/binaryhandling.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx     7596 bx defN 26-Apr-15 20:07 OEBPS/benchmarking.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    88568 bx defN 26-Apr-15 20:07 OEBPS/assets/prio-msg-recv.png
│ │ │ │ -?rw-r--r--  6.1 unx     5837 bx defN 26-Apr-15 20:07 OEBPS/assets/logo.png
│ │ │ │ -?rw-r--r--  6.1 unx     5837 bx defN 26-Apr-15 20:07 OEBPS/assets/erlang-logo.png
│ │ │ │ -?rw-r--r--  6.1 unx     7044 bx stor 26-Apr-15 20:07 OEBPS/assets/dist5.gif
│ │ │ │ -?rw-r--r--  6.1 unx     2939 bx stor 26-Apr-15 20:07 OEBPS/assets/dist4.gif
│ │ │ │ -?rw-r--r--  6.1 unx     5007 bx stor 26-Apr-15 20:07 OEBPS/assets/dist3.gif
│ │ │ │ -?rw-r--r--  6.1 unx     5214 bx stor 26-Apr-15 20:07 OEBPS/assets/dist2.gif
│ │ │ │ -?rw-r--r--  6.1 unx     2284 bx stor 26-Apr-15 20:07 OEBPS/assets/dist1.gif
│ │ │ │ -?rw-r--r--  6.1 unx     7982 bx stor 26-Apr-15 20:07 OEBPS/assets/ballpoint-pen.svg
│ │ │ │ -?rw-r--r--  6.1 unx    91824 bx defN 26-Apr-15 20:07 OEBPS/appup_cookbook.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    47930 bx defN 26-Apr-15 20:07 OEBPS/applications.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx      252 bx defN 26-Apr-15 20:07 META-INF/container.xml
│ │ │ │ -?rw-r--r--  6.1 unx      162 bx defN 26-Apr-15 20:07 META-INF/com.apple.ibooks.display-options.xml
│ │ │ │ -97 files, 3429456 bytes uncompressed, 788616 bytes compressed:  77.0%
│ │ │ │ +Zip file size: 805612 bytes, number of entries: 97
│ │ │ │ +?rw-r--r--  6.1 unx       20 bx stor 26-Apr-21 04:13 mimetype
│ │ │ │ +?rw-r--r--  6.1 unx    14643 bx defN 26-Apr-21 04:13 OEBPS/vulnerabilities.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    17925 bx defN 26-Apr-21 04:13 OEBPS/versions.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     4673 bx defN 26-Apr-21 04:13 OEBPS/upgrade.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    54465 bx defN 26-Apr-21 04:13 OEBPS/typespec.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     2166 bx defN 26-Apr-21 04:13 OEBPS/tutorial.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx      764 bx defN 26-Apr-21 04:13 OEBPS/title.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    46257 bx defN 26-Apr-21 04:13 OEBPS/tablesdatabases.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    12439 bx defN 26-Apr-21 04:13 OEBPS/system_principles.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     7481 bx defN 26-Apr-21 04:13 OEBPS/system_limits.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    63519 bx defN 26-Apr-21 04:13 OEBPS/sup_princ.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx   254168 bx defN 26-Apr-21 04:13 OEBPS/statem.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx   111649 bx defN 26-Apr-21 04:13 OEBPS/spec_proc.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx   252881 bx defN 26-Apr-21 04:13 OEBPS/seq_prog.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx   163061 bx defN 26-Apr-21 04:13 OEBPS/secure_coding.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    15505 bx defN 26-Apr-21 04:13 OEBPS/sbom.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    70567 bx defN 26-Apr-21 04:13 OEBPS/robustness.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    20877 bx defN 26-Apr-21 04:13 OEBPS/release_structure.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    59979 bx defN 26-Apr-21 04:13 OEBPS/release_handling.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     4595 bx defN 26-Apr-21 04:13 OEBPS/reference_manual.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    19454 bx defN 26-Apr-21 04:13 OEBPS/ref_man_records.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    54417 bx defN 26-Apr-21 04:13 OEBPS/ref_man_processes.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    14474 bx defN 26-Apr-21 04:13 OEBPS/ref_man_functions.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    49208 bx defN 26-Apr-21 04:13 OEBPS/records_macros.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     2357 bx defN 26-Apr-21 04:13 OEBPS/readme.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx      785 bx defN 26-Apr-21 04:13 OEBPS/programming_examples.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    40219 bx defN 26-Apr-21 04:13 OEBPS/prog_ex_records.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    15192 bx defN 26-Apr-21 04:13 OEBPS/profiling.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     8499 bx defN 26-Apr-21 04:13 OEBPS/ports.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     3852 bx defN 26-Apr-21 04:13 OEBPS/patterns.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    13419 bx defN 26-Apr-21 04:13 OEBPS/overview.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     8959 bx defN 26-Apr-21 04:13 OEBPS/otp-patch-apply.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    10050 bx defN 26-Apr-21 04:13 OEBPS/opaques.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    15633 bx defN 26-Apr-21 04:13 OEBPS/nominals.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    14148 bx defN 26-Apr-21 04:13 OEBPS/nif.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     6852 bx defN 26-Apr-21 04:13 OEBPS/nav.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    25870 bx defN 26-Apr-21 04:13 OEBPS/modules.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     7018 bx defN 26-Apr-21 04:13 OEBPS/misc.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     5477 bx defN 26-Apr-21 04:13 OEBPS/memory.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    53379 bx defN 26-Apr-21 04:13 OEBPS/maps.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    39594 bx defN 26-Apr-21 04:13 OEBPS/macros.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    31440 bx defN 26-Apr-21 04:13 OEBPS/listhandling.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    53789 bx defN 26-Apr-21 04:13 OEBPS/list_comprehensions.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     2211 bx defN 26-Apr-21 04:13 OEBPS/installation_guide.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    57455 bx defN 26-Apr-21 04:13 OEBPS/install.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    28229 bx defN 26-Apr-21 04:13 OEBPS/install-win32.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    35715 bx defN 26-Apr-21 04:13 OEBPS/install-cross.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    21439 bx defN 26-Apr-21 04:13 OEBPS/included_applications.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     3222 bx defN 26-Apr-21 04:13 OEBPS/howto_debug.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     2353 bx defN 26-Apr-21 04:13 OEBPS/getting_started.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    31366 bx defN 26-Apr-21 04:13 OEBPS/gen_server_concepts.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx   119139 bx defN 26-Apr-21 04:13 OEBPS/funs.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     8680 bx defN 26-Apr-21 04:13 OEBPS/features.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx   268117 bx defN 26-Apr-21 04:13 OEBPS/expressions.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     2365 bx defN 26-Apr-21 04:13 OEBPS/example.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    26770 bx defN 26-Apr-21 04:13 OEBPS/events.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    16719 bx defN 26-Apr-21 04:13 OEBPS/errors.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     4519 bx defN 26-Apr-21 04:13 OEBPS/error_logging.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    42616 bx defN 26-Apr-21 04:13 OEBPS/erl_interface.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    18220 bx defN 26-Apr-21 04:13 OEBPS/embedded.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     2085 bx defN 26-Apr-21 04:13 OEBPS/efficiency_guide.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    46685 bx defN 26-Apr-21 04:13 OEBPS/eff_guide_processes.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    21210 bx defN 26-Apr-21 04:13 OEBPS/eff_guide_functions.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     9338 bx defN 26-Apr-21 04:13 OEBPS/drivers.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    47780 bx defN 26-Apr-21 04:13 OEBPS/documentation.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    14895 bx defN 26-Apr-21 04:13 OEBPS/distributed_applications.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    24447 bx defN 26-Apr-21 04:13 OEBPS/distributed.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    14562 bx defN 26-Apr-21 04:13 OEBPS/dist/epub-erlang-ESPT6BQV.css
│ │ │ │ +?rw-r--r--  6.1 unx      499 bx defN 26-Apr-21 04:13 OEBPS/dist/epub-LSJCIYTM.js
│ │ │ │ +?rw-r--r--  6.1 unx    36776 bx defN 26-Apr-21 04:13 OEBPS/design_principles.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    15003 bx defN 26-Apr-21 04:13 OEBPS/debugging.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    78764 bx defN 26-Apr-21 04:13 OEBPS/data_types.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx   116619 bx defN 26-Apr-21 04:13 OEBPS/create_target.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    14028 bx defN 26-Apr-21 04:13 OEBPS/content.opf
│ │ │ │ +?rw-r--r--  6.1 unx   129434 bx defN 26-Apr-21 04:13 OEBPS/conc_prog.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    35528 bx defN 26-Apr-21 04:13 OEBPS/commoncaveats.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    11940 bx defN 26-Apr-21 04:13 OEBPS/code_loading.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx      803 bx defN 26-Apr-21 04:13 OEBPS/cnode.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     5151 bx defN 26-Apr-21 04:13 OEBPS/character_set.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    40799 bx defN 26-Apr-21 04:13 OEBPS/c_portdriver.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    35602 bx defN 26-Apr-21 04:13 OEBPS/c_port.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    34851 bx defN 26-Apr-21 04:13 OEBPS/bit_syntax.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    53327 bx defN 26-Apr-21 04:13 OEBPS/binaryhandling.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     7596 bx defN 26-Apr-21 04:13 OEBPS/benchmarking.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    88568 bx defN 26-Apr-21 04:13 OEBPS/assets/prio-msg-recv.png
│ │ │ │ +?rw-r--r--  6.1 unx     5837 bx defN 26-Apr-21 04:13 OEBPS/assets/logo.png
│ │ │ │ +?rw-r--r--  6.1 unx     5837 bx defN 26-Apr-21 04:13 OEBPS/assets/erlang-logo.png
│ │ │ │ +?rw-r--r--  6.1 unx     7044 bx stor 26-Apr-21 04:13 OEBPS/assets/dist5.gif
│ │ │ │ +?rw-r--r--  6.1 unx     2939 bx stor 26-Apr-21 04:13 OEBPS/assets/dist4.gif
│ │ │ │ +?rw-r--r--  6.1 unx     5007 bx stor 26-Apr-21 04:13 OEBPS/assets/dist3.gif
│ │ │ │ +?rw-r--r--  6.1 unx     5214 bx stor 26-Apr-21 04:13 OEBPS/assets/dist2.gif
│ │ │ │ +?rw-r--r--  6.1 unx     2284 bx stor 26-Apr-21 04:13 OEBPS/assets/dist1.gif
│ │ │ │ +?rw-r--r--  6.1 unx     7982 bx stor 26-Apr-21 04:13 OEBPS/assets/ballpoint-pen.svg
│ │ │ │ +?rw-r--r--  6.1 unx    91824 bx defN 26-Apr-21 04:13 OEBPS/appup_cookbook.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    47930 bx defN 26-Apr-21 04:13 OEBPS/applications.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx      252 bx defN 26-Apr-21 04:13 META-INF/container.xml
│ │ │ │ +?rw-r--r--  6.1 unx      162 bx defN 26-Apr-21 04:13 META-INF/com.apple.ibooks.display-options.xml
│ │ │ │ +97 files, 3429456 bytes uncompressed, 788630 bytes compressed:  77.0%
│ │ │ ├── zipdetails --redact --walk --utc {}
│ │ │ │ @@ -1,29 +1,29 @@
│ │ │ │  
│ │ │ │  00000 LOCAL HEADER #1       04034B50 (67324752)
│ │ │ │  00004 Extract Zip Spec      0A (10) '1.0'
│ │ │ │  00005 Extract OS            00 (0) 'MS-DOS'
│ │ │ │  00006 General Purpose Flag  0000 (0)
│ │ │ │  00008 Compression Method    0000 (0) 'Stored'
│ │ │ │ -0000A Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ +0000A Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │  0000E CRC                   2CAB616F (749429103)
│ │ │ │  00012 Compressed Size       00000014 (20)
│ │ │ │  00016 Uncompressed Size     00000014 (20)
│ │ │ │  0001A Filename Length       0008 (8)
│ │ │ │  0001C Extra Length          001C (28)
│ │ │ │  0001E Filename              'XXXXXXXX'
│ │ │ │  #
│ │ │ │  # WARNING: Offset 0x1E: Filename 'XXXXXXXX'
│ │ │ │  #          Zero length filename
│ │ │ │  #
│ │ │ │  00026 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │  00028   Length              0009 (9)
│ │ │ │  0002A   Flags               03 (3) 'Modification Access'
│ │ │ │ -0002B   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -0002F   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ +0002B   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +0002F   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │  00033 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │  00035   Length              000B (11)
│ │ │ │  00037   Version             01 (1)
│ │ │ │  00038   UID Size            04 (4)
│ │ │ │  00039   UID                 00000000 (0)
│ │ │ │  0003D   GID Size            04 (4)
│ │ │ │  0003E   GID                 00000000 (0)
│ │ │ │ @@ -31,6663 +31,6663 @@
│ │ │ │  
│ │ │ │  00056 LOCAL HEADER #2       04034B50 (67324752)
│ │ │ │  0005A Extract Zip Spec      14 (20) '2.0'
│ │ │ │  0005B Extract OS            00 (0) 'MS-DOS'
│ │ │ │  0005C General Purpose Flag  0000 (0)
│ │ │ │        [Bits 1-2]            0 'Normal Compression'
│ │ │ │  0005E Compression Method    0008 (8) 'Deflated'
│ │ │ │ -00060 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -00064 CRC                   29F05690 (703616656)
│ │ │ │ -00068 Compressed Size       00000D24 (3364)
│ │ │ │ +00060 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +00064 CRC                   53A58720 (1403356960)
│ │ │ │ +00068 Compressed Size       00000D22 (3362)
│ │ │ │  0006C Uncompressed Size     00003933 (14643)
│ │ │ │  00070 Filename Length       001B (27)
│ │ │ │  00072 Extra Length          001C (28)
│ │ │ │  00074 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │  #
│ │ │ │  # WARNING: Offset 0x74: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │  #          Zero length filename
│ │ │ │  #
│ │ │ │  0008F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │  00091   Length              0009 (9)
│ │ │ │  00093   Flags               03 (3) 'Modification Access'
│ │ │ │ -00094   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -00098   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ +00094   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +00098   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │  0009C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │  0009E   Length              000B (11)
│ │ │ │  000A0   Version             01 (1)
│ │ │ │  000A1   UID Size            04 (4)
│ │ │ │  000A2   UID                 00000000 (0)
│ │ │ │  000A6   GID Size            04 (4)
│ │ │ │  000A7   GID                 00000000 (0)
│ │ │ │  000AB PAYLOAD
│ │ │ │  
│ │ │ │ -00DCF LOCAL HEADER #3       04034B50 (67324752)
│ │ │ │ -00DD3 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -00DD4 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -00DD5 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -00DD7 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -00DD9 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -00DDD CRC                   546A35FD (1416246781)
│ │ │ │ -00DE1 Compressed Size       000015B1 (5553)
│ │ │ │ -00DE5 Uncompressed Size     00004605 (17925)
│ │ │ │ -00DE9 Filename Length       0014 (20)
│ │ │ │ -00DEB Extra Length          001C (28)
│ │ │ │ -00DED Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xDED: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -00E01 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -00E03   Length              0009 (9)
│ │ │ │ -00E05   Flags               03 (3) 'Modification Access'
│ │ │ │ -00E06   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -00E0A   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -00E0E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -00E10   Length              000B (11)
│ │ │ │ -00E12   Version             01 (1)
│ │ │ │ -00E13   UID Size            04 (4)
│ │ │ │ -00E14   UID                 00000000 (0)
│ │ │ │ -00E18   GID Size            04 (4)
│ │ │ │ -00E19   GID                 00000000 (0)
│ │ │ │ -00E1D PAYLOAD
│ │ │ │ -
│ │ │ │ -023CE LOCAL HEADER #4       04034B50 (67324752)
│ │ │ │ -023D2 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -023D3 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -023D4 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -023D6 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -023D8 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -023DC CRC                   03A4A46E (61121646)
│ │ │ │ -023E0 Compressed Size       000006D4 (1748)
│ │ │ │ -023E4 Uncompressed Size     00001241 (4673)
│ │ │ │ -023E8 Filename Length       0013 (19)
│ │ │ │ -023EA Extra Length          001C (28)
│ │ │ │ -023EC Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x23EC: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -023FF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -02401   Length              0009 (9)
│ │ │ │ -02403   Flags               03 (3) 'Modification Access'
│ │ │ │ -02404   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -02408   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -0240C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -0240E   Length              000B (11)
│ │ │ │ -02410   Version             01 (1)
│ │ │ │ -02411   UID Size            04 (4)
│ │ │ │ -02412   UID                 00000000 (0)
│ │ │ │ -02416   GID Size            04 (4)
│ │ │ │ -02417   GID                 00000000 (0)
│ │ │ │ -0241B PAYLOAD
│ │ │ │ -
│ │ │ │ -02AEF LOCAL HEADER #5       04034B50 (67324752)
│ │ │ │ -02AF3 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -02AF4 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -02AF5 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -02AF7 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -02AF9 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -02AFD CRC                   404477C9 (1078228937)
│ │ │ │ -02B01 Compressed Size       00002E75 (11893)
│ │ │ │ -02B05 Uncompressed Size     0000D4C1 (54465)
│ │ │ │ -02B09 Filename Length       0014 (20)
│ │ │ │ -02B0B Extra Length          001C (28)
│ │ │ │ -02B0D Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x2B0D: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -02B21 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -02B23   Length              0009 (9)
│ │ │ │ -02B25   Flags               03 (3) 'Modification Access'
│ │ │ │ -02B26   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -02B2A   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -02B2E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -02B30   Length              000B (11)
│ │ │ │ -02B32   Version             01 (1)
│ │ │ │ -02B33   UID Size            04 (4)
│ │ │ │ -02B34   UID                 00000000 (0)
│ │ │ │ -02B38   GID Size            04 (4)
│ │ │ │ -02B39   GID                 00000000 (0)
│ │ │ │ -02B3D PAYLOAD
│ │ │ │ -
│ │ │ │ -059B2 LOCAL HEADER #6       04034B50 (67324752)
│ │ │ │ -059B6 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -059B7 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -059B8 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -059BA Compression Method    0008 (8) 'Deflated'
│ │ │ │ -059BC Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -059C0 CRC                   272DD323 (657314595)
│ │ │ │ -059C4 Compressed Size       000003EF (1007)
│ │ │ │ -059C8 Uncompressed Size     00000876 (2166)
│ │ │ │ -059CC Filename Length       0014 (20)
│ │ │ │ -059CE Extra Length          001C (28)
│ │ │ │ -059D0 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x59D0: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -059E4 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -059E6   Length              0009 (9)
│ │ │ │ -059E8   Flags               03 (3) 'Modification Access'
│ │ │ │ -059E9   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -059ED   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -059F1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -059F3   Length              000B (11)
│ │ │ │ -059F5   Version             01 (1)
│ │ │ │ -059F6   UID Size            04 (4)
│ │ │ │ -059F7   UID                 00000000 (0)
│ │ │ │ -059FB   GID Size            04 (4)
│ │ │ │ -059FC   GID                 00000000 (0)
│ │ │ │ -05A00 PAYLOAD
│ │ │ │ -
│ │ │ │ -05DEF LOCAL HEADER #7       04034B50 (67324752)
│ │ │ │ -05DF3 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -05DF4 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -05DF5 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -05DF7 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -05DF9 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -05DFD CRC                   2F07766F (789018223)
│ │ │ │ -05E01 Compressed Size       000001AD (429)
│ │ │ │ -05E05 Uncompressed Size     000002FC (764)
│ │ │ │ -05E09 Filename Length       0011 (17)
│ │ │ │ -05E0B Extra Length          001C (28)
│ │ │ │ -05E0D Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x5E0D: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -05E1E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -05E20   Length              0009 (9)
│ │ │ │ -05E22   Flags               03 (3) 'Modification Access'
│ │ │ │ -05E23   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -05E27   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -05E2B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -05E2D   Length              000B (11)
│ │ │ │ -05E2F   Version             01 (1)
│ │ │ │ -05E30   UID Size            04 (4)
│ │ │ │ -05E31   UID                 00000000 (0)
│ │ │ │ -05E35   GID Size            04 (4)
│ │ │ │ -05E36   GID                 00000000 (0)
│ │ │ │ -05E3A PAYLOAD
│ │ │ │ -
│ │ │ │ -05FE7 LOCAL HEADER #8       04034B50 (67324752)
│ │ │ │ -05FEB Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -05FEC Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -05FED General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -05FEF Compression Method    0008 (8) 'Deflated'
│ │ │ │ -05FF1 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -05FF5 CRC                   AD55D2AE (2908082862)
│ │ │ │ -05FF9 Compressed Size       000020BE (8382)
│ │ │ │ -05FFD Uncompressed Size     0000B4B1 (46257)
│ │ │ │ -06001 Filename Length       001B (27)
│ │ │ │ -06003 Extra Length          001C (28)
│ │ │ │ -06005 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x6005: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -06020 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -06022   Length              0009 (9)
│ │ │ │ -06024   Flags               03 (3) 'Modification Access'
│ │ │ │ -06025   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -06029   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -0602D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -0602F   Length              000B (11)
│ │ │ │ -06031   Version             01 (1)
│ │ │ │ -06032   UID Size            04 (4)
│ │ │ │ -06033   UID                 00000000 (0)
│ │ │ │ -06037   GID Size            04 (4)
│ │ │ │ -06038   GID                 00000000 (0)
│ │ │ │ -0603C PAYLOAD
│ │ │ │ -
│ │ │ │ -080FA LOCAL HEADER #9       04034B50 (67324752)
│ │ │ │ -080FE Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -080FF Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -08100 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -08102 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -08104 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -08108 CRC                   4E72FA06 (1316157958)
│ │ │ │ -0810C Compressed Size       00000E68 (3688)
│ │ │ │ -08110 Uncompressed Size     00003097 (12439)
│ │ │ │ -08114 Filename Length       001D (29)
│ │ │ │ -08116 Extra Length          001C (28)
│ │ │ │ -08118 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x8118: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -08135 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -08137   Length              0009 (9)
│ │ │ │ -08139   Flags               03 (3) 'Modification Access'
│ │ │ │ -0813A   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -0813E   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -08142 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -08144   Length              000B (11)
│ │ │ │ -08146   Version             01 (1)
│ │ │ │ -08147   UID Size            04 (4)
│ │ │ │ -08148   UID                 00000000 (0)
│ │ │ │ -0814C   GID Size            04 (4)
│ │ │ │ -0814D   GID                 00000000 (0)
│ │ │ │ -08151 PAYLOAD
│ │ │ │ -
│ │ │ │ -08FB9 LOCAL HEADER #10      04034B50 (67324752)
│ │ │ │ -08FBD Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -08FBE Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -08FBF General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -08FC1 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -08FC3 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -08FC7 CRC                   F138337A (4046992250)
│ │ │ │ -08FCB Compressed Size       0000098E (2446)
│ │ │ │ -08FCF Uncompressed Size     00001D39 (7481)
│ │ │ │ -08FD3 Filename Length       0019 (25)
│ │ │ │ -08FD5 Extra Length          001C (28)
│ │ │ │ -08FD7 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x8FD7: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -08FF0 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -08FF2   Length              0009 (9)
│ │ │ │ -08FF4   Flags               03 (3) 'Modification Access'
│ │ │ │ -08FF5   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -08FF9   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -08FFD Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -08FFF   Length              000B (11)
│ │ │ │ -09001   Version             01 (1)
│ │ │ │ -09002   UID Size            04 (4)
│ │ │ │ -09003   UID                 00000000 (0)
│ │ │ │ -09007   GID Size            04 (4)
│ │ │ │ -09008   GID                 00000000 (0)
│ │ │ │ -0900C PAYLOAD
│ │ │ │ -
│ │ │ │ -0999A LOCAL HEADER #11      04034B50 (67324752)
│ │ │ │ -0999E Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -0999F Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -099A0 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -099A2 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -099A4 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -099A8 CRC                   FC4F496F (4233054575)
│ │ │ │ -099AC Compressed Size       00003883 (14467)
│ │ │ │ -099B0 Uncompressed Size     0000F81F (63519)
│ │ │ │ -099B4 Filename Length       0015 (21)
│ │ │ │ -099B6 Extra Length          001C (28)
│ │ │ │ -099B8 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x99B8: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -099CD Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -099CF   Length              0009 (9)
│ │ │ │ -099D1   Flags               03 (3) 'Modification Access'
│ │ │ │ -099D2   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -099D6   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -099DA Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -099DC   Length              000B (11)
│ │ │ │ -099DE   Version             01 (1)
│ │ │ │ -099DF   UID Size            04 (4)
│ │ │ │ -099E0   UID                 00000000 (0)
│ │ │ │ -099E4   GID Size            04 (4)
│ │ │ │ -099E5   GID                 00000000 (0)
│ │ │ │ -099E9 PAYLOAD
│ │ │ │ -
│ │ │ │ -0D26C LOCAL HEADER #12      04034B50 (67324752)
│ │ │ │ -0D270 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -0D271 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -0D272 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -0D274 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -0D276 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -0D27A CRC                   0BB598F2 (196450546)
│ │ │ │ -0D27E Compressed Size       0000AAFA (43770)
│ │ │ │ -0D282 Uncompressed Size     0003E0D8 (254168)
│ │ │ │ -0D286 Filename Length       0012 (18)
│ │ │ │ -0D288 Extra Length          001C (28)
│ │ │ │ -0D28A Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xD28A: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -0D29C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -0D29E   Length              0009 (9)
│ │ │ │ -0D2A0   Flags               03 (3) 'Modification Access'
│ │ │ │ -0D2A1   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -0D2A5   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -0D2A9 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -0D2AB   Length              000B (11)
│ │ │ │ -0D2AD   Version             01 (1)
│ │ │ │ -0D2AE   UID Size            04 (4)
│ │ │ │ -0D2AF   UID                 00000000 (0)
│ │ │ │ -0D2B3   GID Size            04 (4)
│ │ │ │ -0D2B4   GID                 00000000 (0)
│ │ │ │ -0D2B8 PAYLOAD
│ │ │ │ -
│ │ │ │ -17DB2 LOCAL HEADER #13      04034B50 (67324752)
│ │ │ │ -17DB6 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -17DB7 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -17DB8 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -17DBA Compression Method    0008 (8) 'Deflated'
│ │ │ │ -17DBC Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -17DC0 CRC                   C50A848B (3305800843)
│ │ │ │ -17DC4 Compressed Size       00003AF8 (15096)
│ │ │ │ -17DC8 Uncompressed Size     0001B421 (111649)
│ │ │ │ -17DCC Filename Length       0015 (21)
│ │ │ │ -17DCE Extra Length          001C (28)
│ │ │ │ -17DD0 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x17DD0: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -17DE5 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -17DE7   Length              0009 (9)
│ │ │ │ -17DE9   Flags               03 (3) 'Modification Access'
│ │ │ │ -17DEA   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -17DEE   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -17DF2 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -17DF4   Length              000B (11)
│ │ │ │ -17DF6   Version             01 (1)
│ │ │ │ -17DF7   UID Size            04 (4)
│ │ │ │ -17DF8   UID                 00000000 (0)
│ │ │ │ -17DFC   GID Size            04 (4)
│ │ │ │ -17DFD   GID                 00000000 (0)
│ │ │ │ -17E01 PAYLOAD
│ │ │ │ -
│ │ │ │ -1B8F9 LOCAL HEADER #14      04034B50 (67324752)
│ │ │ │ -1B8FD Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -1B8FE Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -1B8FF General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -1B901 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -1B903 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -1B907 CRC                   B6C2DA9C (3066223260)
│ │ │ │ -1B90B Compressed Size       000091C5 (37317)
│ │ │ │ -1B90F Uncompressed Size     0003DBD1 (252881)
│ │ │ │ -1B913 Filename Length       0014 (20)
│ │ │ │ -1B915 Extra Length          001C (28)
│ │ │ │ -1B917 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x1B917: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -1B92B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -1B92D   Length              0009 (9)
│ │ │ │ -1B92F   Flags               03 (3) 'Modification Access'
│ │ │ │ -1B930   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -1B934   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -1B938 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -1B93A   Length              000B (11)
│ │ │ │ -1B93C   Version             01 (1)
│ │ │ │ -1B93D   UID Size            04 (4)
│ │ │ │ -1B93E   UID                 00000000 (0)
│ │ │ │ -1B942   GID Size            04 (4)
│ │ │ │ -1B943   GID                 00000000 (0)
│ │ │ │ -1B947 PAYLOAD
│ │ │ │ -
│ │ │ │ -24B0C LOCAL HEADER #15      04034B50 (67324752)
│ │ │ │ -24B10 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -24B11 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -24B12 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -24B14 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -24B16 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -24B1A CRC                   6E4D0A9B (1850542747)
│ │ │ │ -24B1E Compressed Size       00009BA8 (39848)
│ │ │ │ -24B22 Uncompressed Size     00027CF5 (163061)
│ │ │ │ -24B26 Filename Length       0019 (25)
│ │ │ │ -24B28 Extra Length          001C (28)
│ │ │ │ -24B2A Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x24B2A: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -24B43 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -24B45   Length              0009 (9)
│ │ │ │ -24B47   Flags               03 (3) 'Modification Access'
│ │ │ │ -24B48   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -24B4C   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -24B50 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -24B52   Length              000B (11)
│ │ │ │ -24B54   Version             01 (1)
│ │ │ │ -24B55   UID Size            04 (4)
│ │ │ │ -24B56   UID                 00000000 (0)
│ │ │ │ -24B5A   GID Size            04 (4)
│ │ │ │ -24B5B   GID                 00000000 (0)
│ │ │ │ -24B5F PAYLOAD
│ │ │ │ -
│ │ │ │ -2E707 LOCAL HEADER #16      04034B50 (67324752)
│ │ │ │ -2E70B Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -2E70C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -2E70D General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -2E70F Compression Method    0008 (8) 'Deflated'
│ │ │ │ -2E711 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -2E715 CRC                   36D4AE72 (919907954)
│ │ │ │ -2E719 Compressed Size       00001219 (4633)
│ │ │ │ -2E71D Uncompressed Size     00003C91 (15505)
│ │ │ │ -2E721 Filename Length       0010 (16)
│ │ │ │ -2E723 Extra Length          001C (28)
│ │ │ │ -2E725 Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x2E725: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -2E735 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -2E737   Length              0009 (9)
│ │ │ │ -2E739   Flags               03 (3) 'Modification Access'
│ │ │ │ -2E73A   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -2E73E   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -2E742 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -2E744   Length              000B (11)
│ │ │ │ -2E746   Version             01 (1)
│ │ │ │ -2E747   UID Size            04 (4)
│ │ │ │ -2E748   UID                 00000000 (0)
│ │ │ │ -2E74C   GID Size            04 (4)
│ │ │ │ -2E74D   GID                 00000000 (0)
│ │ │ │ -2E751 PAYLOAD
│ │ │ │ -
│ │ │ │ -2F96A LOCAL HEADER #17      04034B50 (67324752)
│ │ │ │ -2F96E Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -2F96F Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -2F970 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -2F972 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -2F974 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -2F978 CRC                   0BA4F9CD (195361229)
│ │ │ │ -2F97C Compressed Size       00002A5F (10847)
│ │ │ │ -2F980 Uncompressed Size     000113A7 (70567)
│ │ │ │ -2F984 Filename Length       0016 (22)
│ │ │ │ -2F986 Extra Length          001C (28)
│ │ │ │ -2F988 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x2F988: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -2F99E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -2F9A0   Length              0009 (9)
│ │ │ │ -2F9A2   Flags               03 (3) 'Modification Access'
│ │ │ │ -2F9A3   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -2F9A7   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -2F9AB Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -2F9AD   Length              000B (11)
│ │ │ │ -2F9AF   Version             01 (1)
│ │ │ │ -2F9B0   UID Size            04 (4)
│ │ │ │ -2F9B1   UID                 00000000 (0)
│ │ │ │ -2F9B5   GID Size            04 (4)
│ │ │ │ -2F9B6   GID                 00000000 (0)
│ │ │ │ -2F9BA PAYLOAD
│ │ │ │ -
│ │ │ │ -32419 LOCAL HEADER #18      04034B50 (67324752)
│ │ │ │ -3241D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -3241E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -3241F General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -32421 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -32423 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -32427 CRC                   AF0A8C6F (2936704111)
│ │ │ │ -3242B Compressed Size       000014D9 (5337)
│ │ │ │ -3242F Uncompressed Size     0000518D (20877)
│ │ │ │ -32433 Filename Length       001D (29)
│ │ │ │ -32435 Extra Length          001C (28)
│ │ │ │ -32437 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x32437: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -32454 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -32456   Length              0009 (9)
│ │ │ │ -32458   Flags               03 (3) 'Modification Access'
│ │ │ │ -32459   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -3245D   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -32461 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -32463   Length              000B (11)
│ │ │ │ -32465   Version             01 (1)
│ │ │ │ -32466   UID Size            04 (4)
│ │ │ │ -32467   UID                 00000000 (0)
│ │ │ │ -3246B   GID Size            04 (4)
│ │ │ │ -3246C   GID                 00000000 (0)
│ │ │ │ -32470 PAYLOAD
│ │ │ │ -
│ │ │ │ -33949 LOCAL HEADER #19      04034B50 (67324752)
│ │ │ │ -3394D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -3394E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -3394F General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -33951 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -33953 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -33957 CRC                   0B59709A (190410906)
│ │ │ │ -3395B Compressed Size       000037FF (14335)
│ │ │ │ -3395F Uncompressed Size     0000EA4B (59979)
│ │ │ │ -33963 Filename Length       001C (28)
│ │ │ │ -33965 Extra Length          001C (28)
│ │ │ │ -33967 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x33967: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -33983 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -33985   Length              0009 (9)
│ │ │ │ -33987   Flags               03 (3) 'Modification Access'
│ │ │ │ -33988   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -3398C   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -33990 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -33992   Length              000B (11)
│ │ │ │ -33994   Version             01 (1)
│ │ │ │ -33995   UID Size            04 (4)
│ │ │ │ -33996   UID                 00000000 (0)
│ │ │ │ -3399A   GID Size            04 (4)
│ │ │ │ -3399B   GID                 00000000 (0)
│ │ │ │ -3399F PAYLOAD
│ │ │ │ -
│ │ │ │ -3719E LOCAL HEADER #20      04034B50 (67324752)
│ │ │ │ -371A2 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -371A3 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -371A4 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -371A6 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -371A8 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -371AC CRC                   958EC234 (2509161012)
│ │ │ │ -371B0 Compressed Size       0000069E (1694)
│ │ │ │ -371B4 Uncompressed Size     000011F3 (4595)
│ │ │ │ -371B8 Filename Length       001C (28)
│ │ │ │ -371BA Extra Length          001C (28)
│ │ │ │ -371BC Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x371BC: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -371D8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -371DA   Length              0009 (9)
│ │ │ │ -371DC   Flags               03 (3) 'Modification Access'
│ │ │ │ -371DD   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -371E1   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -371E5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -371E7   Length              000B (11)
│ │ │ │ -371E9   Version             01 (1)
│ │ │ │ -371EA   UID Size            04 (4)
│ │ │ │ -371EB   UID                 00000000 (0)
│ │ │ │ -371EF   GID Size            04 (4)
│ │ │ │ -371F0   GID                 00000000 (0)
│ │ │ │ -371F4 PAYLOAD
│ │ │ │ -
│ │ │ │ -37892 LOCAL HEADER #21      04034B50 (67324752)
│ │ │ │ -37896 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -37897 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -37898 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -3789A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -3789C Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -378A0 CRC                   42501F7E (1112547198)
│ │ │ │ -378A4 Compressed Size       0000107D (4221)
│ │ │ │ -378A8 Uncompressed Size     00004BFE (19454)
│ │ │ │ -378AC Filename Length       001B (27)
│ │ │ │ -378AE Extra Length          001C (28)
│ │ │ │ -378B0 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x378B0: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -378CB Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -378CD   Length              0009 (9)
│ │ │ │ -378CF   Flags               03 (3) 'Modification Access'
│ │ │ │ -378D0   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -378D4   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -378D8 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -378DA   Length              000B (11)
│ │ │ │ -378DC   Version             01 (1)
│ │ │ │ -378DD   UID Size            04 (4)
│ │ │ │ -378DE   UID                 00000000 (0)
│ │ │ │ -378E2   GID Size            04 (4)
│ │ │ │ -378E3   GID                 00000000 (0)
│ │ │ │ -378E7 PAYLOAD
│ │ │ │ -
│ │ │ │ -38964 LOCAL HEADER #22      04034B50 (67324752)
│ │ │ │ -38968 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -38969 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -3896A General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -3896C Compression Method    0008 (8) 'Deflated'
│ │ │ │ -3896E Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -38972 CRC                   3D4A57FE (1028282366)
│ │ │ │ -38976 Compressed Size       00003B3B (15163)
│ │ │ │ -3897A Uncompressed Size     0000D491 (54417)
│ │ │ │ -3897E Filename Length       001D (29)
│ │ │ │ -38980 Extra Length          001C (28)
│ │ │ │ -38982 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x38982: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -3899F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -389A1   Length              0009 (9)
│ │ │ │ -389A3   Flags               03 (3) 'Modification Access'
│ │ │ │ -389A4   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -389A8   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -389AC Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -389AE   Length              000B (11)
│ │ │ │ -389B0   Version             01 (1)
│ │ │ │ -389B1   UID Size            04 (4)
│ │ │ │ -389B2   UID                 00000000 (0)
│ │ │ │ -389B6   GID Size            04 (4)
│ │ │ │ -389B7   GID                 00000000 (0)
│ │ │ │ -389BB PAYLOAD
│ │ │ │ -
│ │ │ │ -3C4F6 LOCAL HEADER #23      04034B50 (67324752)
│ │ │ │ -3C4FA Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -3C4FB Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -3C4FC General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -3C4FE Compression Method    0008 (8) 'Deflated'
│ │ │ │ -3C500 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -3C504 CRC                   76464E51 (1984319057)
│ │ │ │ -3C508 Compressed Size       00000D6B (3435)
│ │ │ │ -3C50C Uncompressed Size     0000388A (14474)
│ │ │ │ -3C510 Filename Length       001D (29)
│ │ │ │ -3C512 Extra Length          001C (28)
│ │ │ │ -3C514 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x3C514: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -3C531 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -3C533   Length              0009 (9)
│ │ │ │ -3C535   Flags               03 (3) 'Modification Access'
│ │ │ │ -3C536   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -3C53A   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -3C53E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -3C540   Length              000B (11)
│ │ │ │ -3C542   Version             01 (1)
│ │ │ │ -3C543   UID Size            04 (4)
│ │ │ │ -3C544   UID                 00000000 (0)
│ │ │ │ -3C548   GID Size            04 (4)
│ │ │ │ -3C549   GID                 00000000 (0)
│ │ │ │ -3C54D PAYLOAD
│ │ │ │ -
│ │ │ │ -3D2B8 LOCAL HEADER #24      04034B50 (67324752)
│ │ │ │ -3D2BC Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -3D2BD Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -3D2BE General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -3D2C0 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -3D2C2 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -3D2C6 CRC                   50EF047D (1357841533)
│ │ │ │ -3D2CA Compressed Size       00001C86 (7302)
│ │ │ │ -3D2CE Uncompressed Size     0000C038 (49208)
│ │ │ │ -3D2D2 Filename Length       001A (26)
│ │ │ │ -3D2D4 Extra Length          001C (28)
│ │ │ │ -3D2D6 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x3D2D6: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -3D2F0 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -3D2F2   Length              0009 (9)
│ │ │ │ -3D2F4   Flags               03 (3) 'Modification Access'
│ │ │ │ -3D2F5   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -3D2F9   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -3D2FD Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -3D2FF   Length              000B (11)
│ │ │ │ -3D301   Version             01 (1)
│ │ │ │ -3D302   UID Size            04 (4)
│ │ │ │ -3D303   UID                 00000000 (0)
│ │ │ │ -3D307   GID Size            04 (4)
│ │ │ │ -3D308   GID                 00000000 (0)
│ │ │ │ -3D30C PAYLOAD
│ │ │ │ -
│ │ │ │ -3EF92 LOCAL HEADER #25      04034B50 (67324752)
│ │ │ │ -3EF96 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -3EF97 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -3EF98 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -3EF9A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -3EF9C Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -3EFA0 CRC                   478B6B96 (1200319382)
│ │ │ │ -3EFA4 Compressed Size       000003DF (991)
│ │ │ │ -3EFA8 Uncompressed Size     00000935 (2357)
│ │ │ │ -3EFAC Filename Length       0012 (18)
│ │ │ │ -3EFAE Extra Length          001C (28)
│ │ │ │ -3EFB0 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x3EFB0: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -3EFC2 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -3EFC4   Length              0009 (9)
│ │ │ │ -3EFC6   Flags               03 (3) 'Modification Access'
│ │ │ │ -3EFC7   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -3EFCB   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -3EFCF Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -3EFD1   Length              000B (11)
│ │ │ │ -3EFD3   Version             01 (1)
│ │ │ │ -3EFD4   UID Size            04 (4)
│ │ │ │ -3EFD5   UID                 00000000 (0)
│ │ │ │ -3EFD9   GID Size            04 (4)
│ │ │ │ -3EFDA   GID                 00000000 (0)
│ │ │ │ -3EFDE PAYLOAD
│ │ │ │ -
│ │ │ │ -3F3BD LOCAL HEADER #26      04034B50 (67324752)
│ │ │ │ -3F3C1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -3F3C2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -3F3C3 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -3F3C5 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -3F3C7 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -3F3CB CRC                   E79489F0 (3885271536)
│ │ │ │ -3F3CF Compressed Size       000001D3 (467)
│ │ │ │ -3F3D3 Uncompressed Size     00000311 (785)
│ │ │ │ -3F3D7 Filename Length       0020 (32)
│ │ │ │ -3F3D9 Extra Length          001C (28)
│ │ │ │ -3F3DB Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x3F3DB: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -3F3FB Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -3F3FD   Length              0009 (9)
│ │ │ │ -3F3FF   Flags               03 (3) 'Modification Access'
│ │ │ │ -3F400   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -3F404   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -3F408 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -3F40A   Length              000B (11)
│ │ │ │ -3F40C   Version             01 (1)
│ │ │ │ -3F40D   UID Size            04 (4)
│ │ │ │ -3F40E   UID                 00000000 (0)
│ │ │ │ -3F412   GID Size            04 (4)
│ │ │ │ -3F413   GID                 00000000 (0)
│ │ │ │ -3F417 PAYLOAD
│ │ │ │ -
│ │ │ │ -3F5EA LOCAL HEADER #27      04034B50 (67324752)
│ │ │ │ -3F5EE Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -3F5EF Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -3F5F0 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -3F5F2 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -3F5F4 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -3F5F8 CRC                   BB37392E (3140958510)
│ │ │ │ -3F5FC Compressed Size       000017AE (6062)
│ │ │ │ -3F600 Uncompressed Size     00009D1B (40219)
│ │ │ │ -3F604 Filename Length       001B (27)
│ │ │ │ -3F606 Extra Length          001C (28)
│ │ │ │ -3F608 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x3F608: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -3F623 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -3F625   Length              0009 (9)
│ │ │ │ -3F627   Flags               03 (3) 'Modification Access'
│ │ │ │ -3F628   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -3F62C   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -3F630 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -3F632   Length              000B (11)
│ │ │ │ -3F634   Version             01 (1)
│ │ │ │ -3F635   UID Size            04 (4)
│ │ │ │ -3F636   UID                 00000000 (0)
│ │ │ │ -3F63A   GID Size            04 (4)
│ │ │ │ -3F63B   GID                 00000000 (0)
│ │ │ │ -3F63F PAYLOAD
│ │ │ │ -
│ │ │ │ -40DED LOCAL HEADER #28      04034B50 (67324752)
│ │ │ │ -40DF1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -40DF2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -40DF3 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -40DF5 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -40DF7 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -40DFB CRC                   09EB9A96 (166435478)
│ │ │ │ -40DFF Compressed Size       0000136D (4973)
│ │ │ │ -40E03 Uncompressed Size     00003B58 (15192)
│ │ │ │ -40E07 Filename Length       0015 (21)
│ │ │ │ -40E09 Extra Length          001C (28)
│ │ │ │ -40E0B Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x40E0B: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -40E20 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -40E22   Length              0009 (9)
│ │ │ │ -40E24   Flags               03 (3) 'Modification Access'
│ │ │ │ -40E25   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -40E29   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -40E2D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -40E2F   Length              000B (11)
│ │ │ │ -40E31   Version             01 (1)
│ │ │ │ -40E32   UID Size            04 (4)
│ │ │ │ -40E33   UID                 00000000 (0)
│ │ │ │ -40E37   GID Size            04 (4)
│ │ │ │ -40E38   GID                 00000000 (0)
│ │ │ │ -40E3C PAYLOAD
│ │ │ │ -
│ │ │ │ -421A9 LOCAL HEADER #29      04034B50 (67324752)
│ │ │ │ -421AD Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -421AE Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -421AF General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -421B1 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -421B3 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -421B7 CRC                   F9EDEEDB (4193119963)
│ │ │ │ -421BB Compressed Size       00000AC9 (2761)
│ │ │ │ -421BF Uncompressed Size     00002133 (8499)
│ │ │ │ -421C3 Filename Length       0011 (17)
│ │ │ │ -421C5 Extra Length          001C (28)
│ │ │ │ -421C7 Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x421C7: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -421D8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -421DA   Length              0009 (9)
│ │ │ │ -421DC   Flags               03 (3) 'Modification Access'
│ │ │ │ -421DD   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -421E1   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -421E5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -421E7   Length              000B (11)
│ │ │ │ -421E9   Version             01 (1)
│ │ │ │ -421EA   UID Size            04 (4)
│ │ │ │ -421EB   UID                 00000000 (0)
│ │ │ │ -421EF   GID Size            04 (4)
│ │ │ │ -421F0   GID                 00000000 (0)
│ │ │ │ -421F4 PAYLOAD
│ │ │ │ -
│ │ │ │ -42CBD LOCAL HEADER #30      04034B50 (67324752)
│ │ │ │ -42CC1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -42CC2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -42CC3 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -42CC5 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -42CC7 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -42CCB CRC                   061A4CFE (102386942)
│ │ │ │ -42CCF Compressed Size       000003FD (1021)
│ │ │ │ -42CD3 Uncompressed Size     00000F0C (3852)
│ │ │ │ -42CD7 Filename Length       0014 (20)
│ │ │ │ -42CD9 Extra Length          001C (28)
│ │ │ │ -42CDB Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x42CDB: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -42CEF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -42CF1   Length              0009 (9)
│ │ │ │ -42CF3   Flags               03 (3) 'Modification Access'
│ │ │ │ -42CF4   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -42CF8   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -42CFC Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -42CFE   Length              000B (11)
│ │ │ │ -42D00   Version             01 (1)
│ │ │ │ -42D01   UID Size            04 (4)
│ │ │ │ -42D02   UID                 00000000 (0)
│ │ │ │ -42D06   GID Size            04 (4)
│ │ │ │ -42D07   GID                 00000000 (0)
│ │ │ │ -42D0B PAYLOAD
│ │ │ │ -
│ │ │ │ -43108 LOCAL HEADER #31      04034B50 (67324752)
│ │ │ │ -4310C Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -4310D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -4310E General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -43110 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -43112 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -43116 CRC                   3F5B0F93 (1062932371)
│ │ │ │ -4311A Compressed Size       00001260 (4704)
│ │ │ │ -4311E Uncompressed Size     0000346B (13419)
│ │ │ │ -43122 Filename Length       0014 (20)
│ │ │ │ -43124 Extra Length          001C (28)
│ │ │ │ -43126 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x43126: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -4313A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -4313C   Length              0009 (9)
│ │ │ │ -4313E   Flags               03 (3) 'Modification Access'
│ │ │ │ -4313F   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -43143   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -43147 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -43149   Length              000B (11)
│ │ │ │ -4314B   Version             01 (1)
│ │ │ │ -4314C   UID Size            04 (4)
│ │ │ │ -4314D   UID                 00000000 (0)
│ │ │ │ -43151   GID Size            04 (4)
│ │ │ │ -43152   GID                 00000000 (0)
│ │ │ │ -43156 PAYLOAD
│ │ │ │ -
│ │ │ │ -443B6 LOCAL HEADER #32      04034B50 (67324752)
│ │ │ │ -443BA Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -443BB Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -443BC General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -443BE Compression Method    0008 (8) 'Deflated'
│ │ │ │ -443C0 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -443C4 CRC                   41B13910 (1102133520)
│ │ │ │ -443C8 Compressed Size       00000ACC (2764)
│ │ │ │ -443CC Uncompressed Size     000022FF (8959)
│ │ │ │ -443D0 Filename Length       001B (27)
│ │ │ │ -443D2 Extra Length          001C (28)
│ │ │ │ -443D4 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x443D4: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -443EF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -443F1   Length              0009 (9)
│ │ │ │ -443F3   Flags               03 (3) 'Modification Access'
│ │ │ │ -443F4   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -443F8   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -443FC Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -443FE   Length              000B (11)
│ │ │ │ -44400   Version             01 (1)
│ │ │ │ -44401   UID Size            04 (4)
│ │ │ │ -44402   UID                 00000000 (0)
│ │ │ │ -44406   GID Size            04 (4)
│ │ │ │ -44407   GID                 00000000 (0)
│ │ │ │ -4440B PAYLOAD
│ │ │ │ -
│ │ │ │ -44ED7 LOCAL HEADER #33      04034B50 (67324752)
│ │ │ │ -44EDB Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -44EDC Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -44EDD General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -44EDF Compression Method    0008 (8) 'Deflated'
│ │ │ │ -44EE1 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -44EE5 CRC                   DB2E23B4 (3677234100)
│ │ │ │ -44EE9 Compressed Size       00000C51 (3153)
│ │ │ │ -44EED Uncompressed Size     00002742 (10050)
│ │ │ │ -44EF1 Filename Length       0013 (19)
│ │ │ │ -44EF3 Extra Length          001C (28)
│ │ │ │ -44EF5 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x44EF5: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -44F08 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -44F0A   Length              0009 (9)
│ │ │ │ -44F0C   Flags               03 (3) 'Modification Access'
│ │ │ │ -44F0D   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -44F11   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -44F15 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -44F17   Length              000B (11)
│ │ │ │ -44F19   Version             01 (1)
│ │ │ │ -44F1A   UID Size            04 (4)
│ │ │ │ -44F1B   UID                 00000000 (0)
│ │ │ │ -44F1F   GID Size            04 (4)
│ │ │ │ -44F20   GID                 00000000 (0)
│ │ │ │ -44F24 PAYLOAD
│ │ │ │ -
│ │ │ │ -45B75 LOCAL HEADER #34      04034B50 (67324752)
│ │ │ │ -45B79 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -45B7A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -45B7B General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -45B7D Compression Method    0008 (8) 'Deflated'
│ │ │ │ -45B7F Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -45B83 CRC                   0705BEAC (117817004)
│ │ │ │ -45B87 Compressed Size       00000C95 (3221)
│ │ │ │ -45B8B Uncompressed Size     00003D11 (15633)
│ │ │ │ -45B8F Filename Length       0014 (20)
│ │ │ │ -45B91 Extra Length          001C (28)
│ │ │ │ -45B93 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x45B93: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -45BA7 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -45BA9   Length              0009 (9)
│ │ │ │ -45BAB   Flags               03 (3) 'Modification Access'
│ │ │ │ -45BAC   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -45BB0   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -45BB4 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -45BB6   Length              000B (11)
│ │ │ │ -45BB8   Version             01 (1)
│ │ │ │ -45BB9   UID Size            04 (4)
│ │ │ │ -45BBA   UID                 00000000 (0)
│ │ │ │ -45BBE   GID Size            04 (4)
│ │ │ │ -45BBF   GID                 00000000 (0)
│ │ │ │ -45BC3 PAYLOAD
│ │ │ │ -
│ │ │ │ -46858 LOCAL HEADER #35      04034B50 (67324752)
│ │ │ │ -4685C Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -4685D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -4685E General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -46860 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -46862 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -46866 CRC                   356E7AD6 (896432854)
│ │ │ │ -4686A Compressed Size       00000F43 (3907)
│ │ │ │ -4686E Uncompressed Size     00003744 (14148)
│ │ │ │ -46872 Filename Length       000F (15)
│ │ │ │ -46874 Extra Length          001C (28)
│ │ │ │ -46876 Filename              'XXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x46876: Filename 'XXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -46885 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -46887   Length              0009 (9)
│ │ │ │ -46889   Flags               03 (3) 'Modification Access'
│ │ │ │ -4688A   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -4688E   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -46892 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -46894   Length              000B (11)
│ │ │ │ -46896   Version             01 (1)
│ │ │ │ -46897   UID Size            04 (4)
│ │ │ │ -46898   UID                 00000000 (0)
│ │ │ │ -4689C   GID Size            04 (4)
│ │ │ │ -4689D   GID                 00000000 (0)
│ │ │ │ -468A1 PAYLOAD
│ │ │ │ -
│ │ │ │ -477E4 LOCAL HEADER #36      04034B50 (67324752)
│ │ │ │ -477E8 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -477E9 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -477EA General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -477EC Compression Method    0008 (8) 'Deflated'
│ │ │ │ -477EE Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -477F2 CRC                   AD08D6E7 (2903037671)
│ │ │ │ -477F6 Compressed Size       000006CE (1742)
│ │ │ │ -477FA Uncompressed Size     00001AC4 (6852)
│ │ │ │ -477FE Filename Length       000F (15)
│ │ │ │ -47800 Extra Length          001C (28)
│ │ │ │ -47802 Filename              'XXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x47802: Filename 'XXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -47811 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -47813   Length              0009 (9)
│ │ │ │ -47815   Flags               03 (3) 'Modification Access'
│ │ │ │ -47816   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -4781A   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -4781E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -47820   Length              000B (11)
│ │ │ │ -47822   Version             01 (1)
│ │ │ │ -47823   UID Size            04 (4)
│ │ │ │ -47824   UID                 00000000 (0)
│ │ │ │ -47828   GID Size            04 (4)
│ │ │ │ -47829   GID                 00000000 (0)
│ │ │ │ -4782D PAYLOAD
│ │ │ │ -
│ │ │ │ -47EFB LOCAL HEADER #37      04034B50 (67324752)
│ │ │ │ -47EFF Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -47F00 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -47F01 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -47F03 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -47F05 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -47F09 CRC                   27AAA5BB (665494971)
│ │ │ │ -47F0D Compressed Size       00001A4F (6735)
│ │ │ │ -47F11 Uncompressed Size     0000650E (25870)
│ │ │ │ -47F15 Filename Length       0013 (19)
│ │ │ │ -47F17 Extra Length          001C (28)
│ │ │ │ -47F19 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x47F19: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -47F2C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -47F2E   Length              0009 (9)
│ │ │ │ -47F30   Flags               03 (3) 'Modification Access'
│ │ │ │ -47F31   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -47F35   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -47F39 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -47F3B   Length              000B (11)
│ │ │ │ -47F3D   Version             01 (1)
│ │ │ │ -47F3E   UID Size            04 (4)
│ │ │ │ -47F3F   UID                 00000000 (0)
│ │ │ │ -47F43   GID Size            04 (4)
│ │ │ │ -47F44   GID                 00000000 (0)
│ │ │ │ -47F48 PAYLOAD
│ │ │ │ -
│ │ │ │ -49997 LOCAL HEADER #38      04034B50 (67324752)
│ │ │ │ -4999B Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -4999C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -4999D General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -4999F Compression Method    0008 (8) 'Deflated'
│ │ │ │ -499A1 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -499A5 CRC                   90967BFA (2425781242)
│ │ │ │ -499A9 Compressed Size       000009A6 (2470)
│ │ │ │ -499AD Uncompressed Size     00001B6A (7018)
│ │ │ │ -499B1 Filename Length       0010 (16)
│ │ │ │ -499B3 Extra Length          001C (28)
│ │ │ │ -499B5 Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x499B5: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -499C5 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -499C7   Length              0009 (9)
│ │ │ │ -499C9   Flags               03 (3) 'Modification Access'
│ │ │ │ -499CA   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -499CE   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -499D2 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -499D4   Length              000B (11)
│ │ │ │ -499D6   Version             01 (1)
│ │ │ │ -499D7   UID Size            04 (4)
│ │ │ │ -499D8   UID                 00000000 (0)
│ │ │ │ -499DC   GID Size            04 (4)
│ │ │ │ -499DD   GID                 00000000 (0)
│ │ │ │ -499E1 PAYLOAD
│ │ │ │ -
│ │ │ │ -4A387 LOCAL HEADER #39      04034B50 (67324752)
│ │ │ │ -4A38B Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -4A38C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -4A38D General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -4A38F Compression Method    0008 (8) 'Deflated'
│ │ │ │ -4A391 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -4A395 CRC                   D37ED789 (3548305289)
│ │ │ │ -4A399 Compressed Size       000006B6 (1718)
│ │ │ │ -4A39D Uncompressed Size     00001565 (5477)
│ │ │ │ -4A3A1 Filename Length       0012 (18)
│ │ │ │ -4A3A3 Extra Length          001C (28)
│ │ │ │ -4A3A5 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x4A3A5: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -4A3B7 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -4A3B9   Length              0009 (9)
│ │ │ │ -4A3BB   Flags               03 (3) 'Modification Access'
│ │ │ │ -4A3BC   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -4A3C0   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -4A3C4 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -4A3C6   Length              000B (11)
│ │ │ │ -4A3C8   Version             01 (1)
│ │ │ │ -4A3C9   UID Size            04 (4)
│ │ │ │ -4A3CA   UID                 00000000 (0)
│ │ │ │ -4A3CE   GID Size            04 (4)
│ │ │ │ -4A3CF   GID                 00000000 (0)
│ │ │ │ -4A3D3 PAYLOAD
│ │ │ │ -
│ │ │ │ -4AA89 LOCAL HEADER #40      04034B50 (67324752)
│ │ │ │ -4AA8D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -4AA8E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -4AA8F General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -4AA91 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -4AA93 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -4AA97 CRC                   92D091A2 (2463142306)
│ │ │ │ -4AA9B Compressed Size       00002D59 (11609)
│ │ │ │ -4AA9F Uncompressed Size     0000D083 (53379)
│ │ │ │ -4AAA3 Filename Length       0010 (16)
│ │ │ │ -4AAA5 Extra Length          001C (28)
│ │ │ │ -4AAA7 Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x4AAA7: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -4AAB7 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -4AAB9   Length              0009 (9)
│ │ │ │ -4AABB   Flags               03 (3) 'Modification Access'
│ │ │ │ -4AABC   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -4AAC0   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -4AAC4 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -4AAC6   Length              000B (11)
│ │ │ │ -4AAC8   Version             01 (1)
│ │ │ │ -4AAC9   UID Size            04 (4)
│ │ │ │ -4AACA   UID                 00000000 (0)
│ │ │ │ -4AACE   GID Size            04 (4)
│ │ │ │ -4AACF   GID                 00000000 (0)
│ │ │ │ -4AAD3 PAYLOAD
│ │ │ │ -
│ │ │ │ -4D82C LOCAL HEADER #41      04034B50 (67324752)
│ │ │ │ -4D830 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -4D831 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -4D832 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -4D834 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -4D836 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -4D83A CRC                   608FA1E3 (1620025827)
│ │ │ │ -4D83E Compressed Size       00001E84 (7812)
│ │ │ │ -4D842 Uncompressed Size     00009AAA (39594)
│ │ │ │ -4D846 Filename Length       0012 (18)
│ │ │ │ -4D848 Extra Length          001C (28)
│ │ │ │ -4D84A Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x4D84A: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -4D85C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -4D85E   Length              0009 (9)
│ │ │ │ -4D860   Flags               03 (3) 'Modification Access'
│ │ │ │ -4D861   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -4D865   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -4D869 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -4D86B   Length              000B (11)
│ │ │ │ -4D86D   Version             01 (1)
│ │ │ │ -4D86E   UID Size            04 (4)
│ │ │ │ -4D86F   UID                 00000000 (0)
│ │ │ │ -4D873   GID Size            04 (4)
│ │ │ │ -4D874   GID                 00000000 (0)
│ │ │ │ -4D878 PAYLOAD
│ │ │ │ -
│ │ │ │ -4F6FC LOCAL HEADER #42      04034B50 (67324752)
│ │ │ │ -4F700 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -4F701 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -4F702 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -4F704 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -4F706 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -4F70A CRC                   69109545 (1762694469)
│ │ │ │ -4F70E Compressed Size       00001471 (5233)
│ │ │ │ -4F712 Uncompressed Size     00007AD0 (31440)
│ │ │ │ -4F716 Filename Length       0018 (24)
│ │ │ │ -4F718 Extra Length          001C (28)
│ │ │ │ -4F71A Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x4F71A: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -4F732 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -4F734   Length              0009 (9)
│ │ │ │ -4F736   Flags               03 (3) 'Modification Access'
│ │ │ │ -4F737   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -4F73B   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -4F73F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -4F741   Length              000B (11)
│ │ │ │ -4F743   Version             01 (1)
│ │ │ │ -4F744   UID Size            04 (4)
│ │ │ │ -4F745   UID                 00000000 (0)
│ │ │ │ -4F749   GID Size            04 (4)
│ │ │ │ -4F74A   GID                 00000000 (0)
│ │ │ │ -4F74E PAYLOAD
│ │ │ │ -
│ │ │ │ -50BBF LOCAL HEADER #43      04034B50 (67324752)
│ │ │ │ -50BC3 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -50BC4 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -50BC5 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -50BC7 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -50BC9 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -50BCD CRC                   274FF23B (659550779)
│ │ │ │ -50BD1 Compressed Size       000021DB (8667)
│ │ │ │ -50BD5 Uncompressed Size     0000D21D (53789)
│ │ │ │ -50BD9 Filename Length       001F (31)
│ │ │ │ -50BDB Extra Length          001C (28)
│ │ │ │ -50BDD Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x50BDD: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -50BFC Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -50BFE   Length              0009 (9)
│ │ │ │ -50C00   Flags               03 (3) 'Modification Access'
│ │ │ │ -50C01   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -50C05   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -50C09 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -50C0B   Length              000B (11)
│ │ │ │ -50C0D   Version             01 (1)
│ │ │ │ -50C0E   UID Size            04 (4)
│ │ │ │ -50C0F   UID                 00000000 (0)
│ │ │ │ -50C13   GID Size            04 (4)
│ │ │ │ -50C14   GID                 00000000 (0)
│ │ │ │ -50C18 PAYLOAD
│ │ │ │ -
│ │ │ │ -52DF3 LOCAL HEADER #44      04034B50 (67324752)
│ │ │ │ -52DF7 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -52DF8 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -52DF9 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -52DFB Compression Method    0008 (8) 'Deflated'
│ │ │ │ -52DFD Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -52E01 CRC                   585AC976 (1482344822)
│ │ │ │ -52E05 Compressed Size       000003F7 (1015)
│ │ │ │ -52E09 Uncompressed Size     000008A3 (2211)
│ │ │ │ -52E0D Filename Length       001E (30)
│ │ │ │ -52E0F Extra Length          001C (28)
│ │ │ │ -52E11 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x52E11: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -52E2F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -52E31   Length              0009 (9)
│ │ │ │ -52E33   Flags               03 (3) 'Modification Access'
│ │ │ │ -52E34   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -52E38   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -52E3C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -52E3E   Length              000B (11)
│ │ │ │ -52E40   Version             01 (1)
│ │ │ │ -52E41   UID Size            04 (4)
│ │ │ │ -52E42   UID                 00000000 (0)
│ │ │ │ -52E46   GID Size            04 (4)
│ │ │ │ -52E47   GID                 00000000 (0)
│ │ │ │ -52E4B PAYLOAD
│ │ │ │ -
│ │ │ │ -53242 LOCAL HEADER #45      04034B50 (67324752)
│ │ │ │ -53246 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -53247 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -53248 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -5324A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -5324C Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -53250 CRC                   16308EDA (372281050)
│ │ │ │ -53254 Compressed Size       00004361 (17249)
│ │ │ │ -53258 Uncompressed Size     0000E06F (57455)
│ │ │ │ -5325C Filename Length       0013 (19)
│ │ │ │ -5325E Extra Length          001C (28)
│ │ │ │ -53260 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x53260: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -53273 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -53275   Length              0009 (9)
│ │ │ │ -53277   Flags               03 (3) 'Modification Access'
│ │ │ │ -53278   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -5327C   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -53280 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -53282   Length              000B (11)
│ │ │ │ -53284   Version             01 (1)
│ │ │ │ -53285   UID Size            04 (4)
│ │ │ │ -53286   UID                 00000000 (0)
│ │ │ │ -5328A   GID Size            04 (4)
│ │ │ │ -5328B   GID                 00000000 (0)
│ │ │ │ -5328F PAYLOAD
│ │ │ │ -
│ │ │ │ -575F0 LOCAL HEADER #46      04034B50 (67324752)
│ │ │ │ -575F4 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -575F5 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -575F6 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -575F8 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -575FA Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -575FE CRC                   741EF03C (1948184636)
│ │ │ │ -57602 Compressed Size       000026C3 (9923)
│ │ │ │ -57606 Uncompressed Size     00006E45 (28229)
│ │ │ │ -5760A Filename Length       0019 (25)
│ │ │ │ -5760C Extra Length          001C (28)
│ │ │ │ -5760E Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x5760E: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -57627 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -57629   Length              0009 (9)
│ │ │ │ -5762B   Flags               03 (3) 'Modification Access'
│ │ │ │ -5762C   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -57630   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -57634 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -57636   Length              000B (11)
│ │ │ │ -57638   Version             01 (1)
│ │ │ │ -57639   UID Size            04 (4)
│ │ │ │ -5763A   UID                 00000000 (0)
│ │ │ │ -5763E   GID Size            04 (4)
│ │ │ │ -5763F   GID                 00000000 (0)
│ │ │ │ -57643 PAYLOAD
│ │ │ │ -
│ │ │ │ -59D06 LOCAL HEADER #47      04034B50 (67324752)
│ │ │ │ -59D0A Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -59D0B Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -59D0C General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -59D0E Compression Method    0008 (8) 'Deflated'
│ │ │ │ -59D10 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -59D14 CRC                   F8618863 (4167141475)
│ │ │ │ -59D18 Compressed Size       00002738 (10040)
│ │ │ │ -59D1C Uncompressed Size     00008B83 (35715)
│ │ │ │ -59D20 Filename Length       0019 (25)
│ │ │ │ -59D22 Extra Length          001C (28)
│ │ │ │ -59D24 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x59D24: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -59D3D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -59D3F   Length              0009 (9)
│ │ │ │ -59D41   Flags               03 (3) 'Modification Access'
│ │ │ │ -59D42   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -59D46   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -59D4A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -59D4C   Length              000B (11)
│ │ │ │ -59D4E   Version             01 (1)
│ │ │ │ -59D4F   UID Size            04 (4)
│ │ │ │ -59D50   UID                 00000000 (0)
│ │ │ │ -59D54   GID Size            04 (4)
│ │ │ │ -59D55   GID                 00000000 (0)
│ │ │ │ -59D59 PAYLOAD
│ │ │ │ -
│ │ │ │ -5C491 LOCAL HEADER #48      04034B50 (67324752)
│ │ │ │ -5C495 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -5C496 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -5C497 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -5C499 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -5C49B Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -5C49F CRC                   50018C09 (1342278665)
│ │ │ │ -5C4A3 Compressed Size       00000ECF (3791)
│ │ │ │ -5C4A7 Uncompressed Size     000053BF (21439)
│ │ │ │ -5C4AB Filename Length       0021 (33)
│ │ │ │ -5C4AD Extra Length          001C (28)
│ │ │ │ -5C4AF Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x5C4AF: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -5C4D0 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -5C4D2   Length              0009 (9)
│ │ │ │ -5C4D4   Flags               03 (3) 'Modification Access'
│ │ │ │ -5C4D5   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -5C4D9   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -5C4DD Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -5C4DF   Length              000B (11)
│ │ │ │ -5C4E1   Version             01 (1)
│ │ │ │ -5C4E2   UID Size            04 (4)
│ │ │ │ -5C4E3   UID                 00000000 (0)
│ │ │ │ -5C4E7   GID Size            04 (4)
│ │ │ │ -5C4E8   GID                 00000000 (0)
│ │ │ │ -5C4EC PAYLOAD
│ │ │ │ -
│ │ │ │ -5D3BB LOCAL HEADER #49      04034B50 (67324752)
│ │ │ │ -5D3BF Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -5D3C0 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -5D3C1 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -5D3C3 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -5D3C5 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -5D3C9 CRC                   D1EC3113 (3521917203)
│ │ │ │ -5D3CD Compressed Size       00000535 (1333)
│ │ │ │ -5D3D1 Uncompressed Size     00000C96 (3222)
│ │ │ │ -5D3D5 Filename Length       0017 (23)
│ │ │ │ -5D3D7 Extra Length          001C (28)
│ │ │ │ -5D3D9 Filename              'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x5D3D9: Filename 'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -5D3F0 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -5D3F2   Length              0009 (9)
│ │ │ │ -5D3F4   Flags               03 (3) 'Modification Access'
│ │ │ │ -5D3F5   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -5D3F9   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -5D3FD Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -5D3FF   Length              000B (11)
│ │ │ │ -5D401   Version             01 (1)
│ │ │ │ -5D402   UID Size            04 (4)
│ │ │ │ -5D403   UID                 00000000 (0)
│ │ │ │ -5D407   GID Size            04 (4)
│ │ │ │ -5D408   GID                 00000000 (0)
│ │ │ │ -5D40C PAYLOAD
│ │ │ │ -
│ │ │ │ -5D941 LOCAL HEADER #50      04034B50 (67324752)
│ │ │ │ -5D945 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -5D946 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -5D947 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -5D949 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -5D94B Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -5D94F CRC                   9ED6F2D9 (2664887001)
│ │ │ │ -5D953 Compressed Size       00000467 (1127)
│ │ │ │ -5D957 Uncompressed Size     00000931 (2353)
│ │ │ │ -5D95B Filename Length       001B (27)
│ │ │ │ -5D95D Extra Length          001C (28)
│ │ │ │ -5D95F Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x5D95F: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -5D97A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -5D97C   Length              0009 (9)
│ │ │ │ -5D97E   Flags               03 (3) 'Modification Access'
│ │ │ │ -5D97F   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -5D983   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -5D987 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -5D989   Length              000B (11)
│ │ │ │ -5D98B   Version             01 (1)
│ │ │ │ -5D98C   UID Size            04 (4)
│ │ │ │ -5D98D   UID                 00000000 (0)
│ │ │ │ -5D991   GID Size            04 (4)
│ │ │ │ -5D992   GID                 00000000 (0)
│ │ │ │ -5D996 PAYLOAD
│ │ │ │ -
│ │ │ │ -5DDFD LOCAL HEADER #51      04034B50 (67324752)
│ │ │ │ -5DE01 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -5DE02 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -5DE03 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -5DE05 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -5DE07 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -5DE0B CRC                   BA8B93BA (3129709498)
│ │ │ │ -5DE0F Compressed Size       000016F5 (5877)
│ │ │ │ -5DE13 Uncompressed Size     00007A86 (31366)
│ │ │ │ -5DE17 Filename Length       001F (31)
│ │ │ │ -5DE19 Extra Length          001C (28)
│ │ │ │ -5DE1B Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x5DE1B: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -5DE3A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -5DE3C   Length              0009 (9)
│ │ │ │ -5DE3E   Flags               03 (3) 'Modification Access'
│ │ │ │ -5DE3F   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -5DE43   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -5DE47 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -5DE49   Length              000B (11)
│ │ │ │ -5DE4B   Version             01 (1)
│ │ │ │ -5DE4C   UID Size            04 (4)
│ │ │ │ -5DE4D   UID                 00000000 (0)
│ │ │ │ -5DE51   GID Size            04 (4)
│ │ │ │ -5DE52   GID                 00000000 (0)
│ │ │ │ -5DE56 PAYLOAD
│ │ │ │ -
│ │ │ │ -5F54B LOCAL HEADER #52      04034B50 (67324752)
│ │ │ │ -5F54F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -5F550 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -5F551 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -5F553 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -5F555 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -5F559 CRC                   7113BB88 (1897118600)
│ │ │ │ -5F55D Compressed Size       00004171 (16753)
│ │ │ │ -5F561 Uncompressed Size     0001D163 (119139)
│ │ │ │ -5F565 Filename Length       0010 (16)
│ │ │ │ -5F567 Extra Length          001C (28)
│ │ │ │ -5F569 Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x5F569: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -5F579 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -5F57B   Length              0009 (9)
│ │ │ │ -5F57D   Flags               03 (3) 'Modification Access'
│ │ │ │ -5F57E   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -5F582   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -5F586 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -5F588   Length              000B (11)
│ │ │ │ -5F58A   Version             01 (1)
│ │ │ │ -5F58B   UID Size            04 (4)
│ │ │ │ -5F58C   UID                 00000000 (0)
│ │ │ │ -5F590   GID Size            04 (4)
│ │ │ │ -5F591   GID                 00000000 (0)
│ │ │ │ -5F595 PAYLOAD
│ │ │ │ -
│ │ │ │ -63706 LOCAL HEADER #53      04034B50 (67324752)
│ │ │ │ -6370A Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -6370B Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -6370C General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -6370E Compression Method    0008 (8) 'Deflated'
│ │ │ │ -63710 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -63714 CRC                   C55EF92D (3311335725)
│ │ │ │ -63718 Compressed Size       00000AE8 (2792)
│ │ │ │ -6371C Uncompressed Size     000021E8 (8680)
│ │ │ │ -63720 Filename Length       0014 (20)
│ │ │ │ -63722 Extra Length          001C (28)
│ │ │ │ -63724 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x63724: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -63738 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -6373A   Length              0009 (9)
│ │ │ │ -6373C   Flags               03 (3) 'Modification Access'
│ │ │ │ -6373D   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -63741   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -63745 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -63747   Length              000B (11)
│ │ │ │ -63749   Version             01 (1)
│ │ │ │ -6374A   UID Size            04 (4)
│ │ │ │ -6374B   UID                 00000000 (0)
│ │ │ │ -6374F   GID Size            04 (4)
│ │ │ │ -63750   GID                 00000000 (0)
│ │ │ │ -63754 PAYLOAD
│ │ │ │ -
│ │ │ │ -6423C LOCAL HEADER #54      04034B50 (67324752)
│ │ │ │ -64240 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -64241 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -64242 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -64244 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -64246 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -6424A CRC                   B3826829 (3011668009)
│ │ │ │ -6424E Compressed Size       0000B524 (46372)
│ │ │ │ -64252 Uncompressed Size     00041755 (268117)
│ │ │ │ -64256 Filename Length       0017 (23)
│ │ │ │ -64258 Extra Length          001C (28)
│ │ │ │ -6425A Filename              'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x6425A: Filename 'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -64271 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -64273   Length              0009 (9)
│ │ │ │ -64275   Flags               03 (3) 'Modification Access'
│ │ │ │ -64276   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -6427A   Access Time         69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -6427E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -64280   Length              000B (11)
│ │ │ │ -64282   Version             01 (1)
│ │ │ │ -64283   UID Size            04 (4)
│ │ │ │ -64284   UID                 00000000 (0)
│ │ │ │ -64288   GID Size            04 (4)
│ │ │ │ -64289   GID                 00000000 (0)
│ │ │ │ -6428D PAYLOAD
│ │ │ │ -
│ │ │ │ -6F7B1 LOCAL HEADER #55      04034B50 (67324752)
│ │ │ │ -6F7B5 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -6F7B6 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -6F7B7 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -6F7B9 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -6F7BB Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -6F7BF CRC                   A49E0590 (2761819536)
│ │ │ │ -6F7C3 Compressed Size       000003FE (1022)
│ │ │ │ -6F7C7 Uncompressed Size     0000093D (2365)
│ │ │ │ -6F7CB Filename Length       0013 (19)
│ │ │ │ -6F7CD Extra Length          001C (28)
│ │ │ │ -6F7CF Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x6F7CF: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -6F7E2 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -6F7E4   Length              0009 (9)
│ │ │ │ -6F7E6   Flags               03 (3) 'Modification Access'
│ │ │ │ -6F7E7   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -6F7EB   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -6F7EF Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -6F7F1   Length              000B (11)
│ │ │ │ -6F7F3   Version             01 (1)
│ │ │ │ -6F7F4   UID Size            04 (4)
│ │ │ │ -6F7F5   UID                 00000000 (0)
│ │ │ │ -6F7F9   GID Size            04 (4)
│ │ │ │ -6F7FA   GID                 00000000 (0)
│ │ │ │ -6F7FE PAYLOAD
│ │ │ │ -
│ │ │ │ -6FBFC LOCAL HEADER #56      04034B50 (67324752)
│ │ │ │ -6FC00 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -6FC01 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -6FC02 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -6FC04 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -6FC06 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -6FC0A CRC                   1FD7FA48 (534248008)
│ │ │ │ -6FC0E Compressed Size       000014D8 (5336)
│ │ │ │ -6FC12 Uncompressed Size     00006892 (26770)
│ │ │ │ -6FC16 Filename Length       0012 (18)
│ │ │ │ -6FC18 Extra Length          001C (28)
│ │ │ │ -6FC1A Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x6FC1A: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -6FC2C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -6FC2E   Length              0009 (9)
│ │ │ │ -6FC30   Flags               03 (3) 'Modification Access'
│ │ │ │ -6FC31   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -6FC35   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -6FC39 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -6FC3B   Length              000B (11)
│ │ │ │ -6FC3D   Version             01 (1)
│ │ │ │ -6FC3E   UID Size            04 (4)
│ │ │ │ -6FC3F   UID                 00000000 (0)
│ │ │ │ -6FC43   GID Size            04 (4)
│ │ │ │ -6FC44   GID                 00000000 (0)
│ │ │ │ -6FC48 PAYLOAD
│ │ │ │ -
│ │ │ │ -71120 LOCAL HEADER #57      04034B50 (67324752)
│ │ │ │ -71124 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -71125 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -71126 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -71128 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -7112A Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7112E CRC                   7167272B (1902585643)
│ │ │ │ -71132 Compressed Size       00001205 (4613)
│ │ │ │ -71136 Uncompressed Size     0000414F (16719)
│ │ │ │ -7113A Filename Length       0012 (18)
│ │ │ │ -7113C Extra Length          001C (28)
│ │ │ │ -7113E Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x7113E: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -71150 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -71152   Length              0009 (9)
│ │ │ │ -71154   Flags               03 (3) 'Modification Access'
│ │ │ │ -71155   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -71159   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7115D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -7115F   Length              000B (11)
│ │ │ │ -71161   Version             01 (1)
│ │ │ │ -71162   UID Size            04 (4)
│ │ │ │ -71163   UID                 00000000 (0)
│ │ │ │ -71167   GID Size            04 (4)
│ │ │ │ -71168   GID                 00000000 (0)
│ │ │ │ -7116C PAYLOAD
│ │ │ │ -
│ │ │ │ -72371 LOCAL HEADER #58      04034B50 (67324752)
│ │ │ │ -72375 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -72376 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -72377 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -72379 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -7237B Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7237F CRC                   5C8A4BDC (1552567260)
│ │ │ │ -72383 Compressed Size       00000704 (1796)
│ │ │ │ -72387 Uncompressed Size     000011A7 (4519)
│ │ │ │ -7238B Filename Length       0019 (25)
│ │ │ │ -7238D Extra Length          001C (28)
│ │ │ │ -7238F Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x7238F: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -723A8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -723AA   Length              0009 (9)
│ │ │ │ -723AC   Flags               03 (3) 'Modification Access'
│ │ │ │ -723AD   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -723B1   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -723B5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -723B7   Length              000B (11)
│ │ │ │ -723B9   Version             01 (1)
│ │ │ │ -723BA   UID Size            04 (4)
│ │ │ │ -723BB   UID                 00000000 (0)
│ │ │ │ -723BF   GID Size            04 (4)
│ │ │ │ -723C0   GID                 00000000 (0)
│ │ │ │ -723C4 PAYLOAD
│ │ │ │ -
│ │ │ │ -72AC8 LOCAL HEADER #59      04034B50 (67324752)
│ │ │ │ -72ACC Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -72ACD Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -72ACE General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -72AD0 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -72AD2 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -72AD6 CRC                   337967C1 (863594433)
│ │ │ │ -72ADA Compressed Size       000018B8 (6328)
│ │ │ │ -72ADE Uncompressed Size     0000A678 (42616)
│ │ │ │ -72AE2 Filename Length       0019 (25)
│ │ │ │ -72AE4 Extra Length          001C (28)
│ │ │ │ -72AE6 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x72AE6: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -72AFF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -72B01   Length              0009 (9)
│ │ │ │ -72B03   Flags               03 (3) 'Modification Access'
│ │ │ │ -72B04   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -72B08   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -72B0C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -72B0E   Length              000B (11)
│ │ │ │ -72B10   Version             01 (1)
│ │ │ │ -72B11   UID Size            04 (4)
│ │ │ │ -72B12   UID                 00000000 (0)
│ │ │ │ -72B16   GID Size            04 (4)
│ │ │ │ -72B17   GID                 00000000 (0)
│ │ │ │ -72B1B PAYLOAD
│ │ │ │ -
│ │ │ │ -743D3 LOCAL HEADER #60      04034B50 (67324752)
│ │ │ │ -743D7 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -743D8 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -743D9 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -743DB Compression Method    0008 (8) 'Deflated'
│ │ │ │ -743DD Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -743E1 CRC                   4D1409E6 (1293158886)
│ │ │ │ -743E5 Compressed Size       0000177C (6012)
│ │ │ │ -743E9 Uncompressed Size     0000472C (18220)
│ │ │ │ -743ED Filename Length       0014 (20)
│ │ │ │ -743EF Extra Length          001C (28)
│ │ │ │ -743F1 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x743F1: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -74405 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -74407   Length              0009 (9)
│ │ │ │ -74409   Flags               03 (3) 'Modification Access'
│ │ │ │ -7440A   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7440E   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -74412 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -74414   Length              000B (11)
│ │ │ │ -74416   Version             01 (1)
│ │ │ │ -74417   UID Size            04 (4)
│ │ │ │ -74418   UID                 00000000 (0)
│ │ │ │ -7441C   GID Size            04 (4)
│ │ │ │ -7441D   GID                 00000000 (0)
│ │ │ │ -74421 PAYLOAD
│ │ │ │ -
│ │ │ │ -75B9D LOCAL HEADER #61      04034B50 (67324752)
│ │ │ │ -75BA1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -75BA2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -75BA3 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -75BA5 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -75BA7 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -75BAB CRC                   2F723DFF (796016127)
│ │ │ │ -75BAF Compressed Size       00000409 (1033)
│ │ │ │ -75BB3 Uncompressed Size     00000825 (2085)
│ │ │ │ -75BB7 Filename Length       001C (28)
│ │ │ │ -75BB9 Extra Length          001C (28)
│ │ │ │ -75BBB Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x75BBB: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -75BD7 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -75BD9   Length              0009 (9)
│ │ │ │ -75BDB   Flags               03 (3) 'Modification Access'
│ │ │ │ -75BDC   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -75BE0   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -75BE4 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -75BE6   Length              000B (11)
│ │ │ │ -75BE8   Version             01 (1)
│ │ │ │ -75BE9   UID Size            04 (4)
│ │ │ │ -75BEA   UID                 00000000 (0)
│ │ │ │ -75BEE   GID Size            04 (4)
│ │ │ │ -75BEF   GID                 00000000 (0)
│ │ │ │ -75BF3 PAYLOAD
│ │ │ │ -
│ │ │ │ -75FFC LOCAL HEADER #62      04034B50 (67324752)
│ │ │ │ -76000 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -76001 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -76002 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -76004 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -76006 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7600A CRC                   CCD906B0 (3436775088)
│ │ │ │ -7600E Compressed Size       000024C6 (9414)
│ │ │ │ -76012 Uncompressed Size     0000B65D (46685)
│ │ │ │ -76016 Filename Length       001F (31)
│ │ │ │ -76018 Extra Length          001C (28)
│ │ │ │ -7601A Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x7601A: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -76039 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -7603B   Length              0009 (9)
│ │ │ │ -7603D   Flags               03 (3) 'Modification Access'
│ │ │ │ -7603E   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -76042   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -76046 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -76048   Length              000B (11)
│ │ │ │ -7604A   Version             01 (1)
│ │ │ │ -7604B   UID Size            04 (4)
│ │ │ │ -7604C   UID                 00000000 (0)
│ │ │ │ -76050   GID Size            04 (4)
│ │ │ │ -76051   GID                 00000000 (0)
│ │ │ │ -76055 PAYLOAD
│ │ │ │ -
│ │ │ │ -7851B LOCAL HEADER #63      04034B50 (67324752)
│ │ │ │ -7851F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -78520 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -78521 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -78523 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -78525 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -78529 CRC                   E78CD1A8 (3884765608)
│ │ │ │ -7852D Compressed Size       00000E7C (3708)
│ │ │ │ -78531 Uncompressed Size     000052DA (21210)
│ │ │ │ -78535 Filename Length       001F (31)
│ │ │ │ -78537 Extra Length          001C (28)
│ │ │ │ -78539 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x78539: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -78558 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -7855A   Length              0009 (9)
│ │ │ │ -7855C   Flags               03 (3) 'Modification Access'
│ │ │ │ -7855D   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -78561   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -78565 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -78567   Length              000B (11)
│ │ │ │ -78569   Version             01 (1)
│ │ │ │ -7856A   UID Size            04 (4)
│ │ │ │ -7856B   UID                 00000000 (0)
│ │ │ │ -7856F   GID Size            04 (4)
│ │ │ │ -78570   GID                 00000000 (0)
│ │ │ │ -78574 PAYLOAD
│ │ │ │ -
│ │ │ │ -793F0 LOCAL HEADER #64      04034B50 (67324752)
│ │ │ │ -793F4 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -793F5 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -793F6 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -793F8 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -793FA Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -793FE CRC                   E196989B (3784743067)
│ │ │ │ -79402 Compressed Size       00000A44 (2628)
│ │ │ │ -79406 Uncompressed Size     0000247A (9338)
│ │ │ │ -7940A Filename Length       0013 (19)
│ │ │ │ -7940C Extra Length          001C (28)
│ │ │ │ -7940E Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x7940E: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -79421 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -79423   Length              0009 (9)
│ │ │ │ -79425   Flags               03 (3) 'Modification Access'
│ │ │ │ -79426   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7942A   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7942E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -79430   Length              000B (11)
│ │ │ │ -79432   Version             01 (1)
│ │ │ │ -79433   UID Size            04 (4)
│ │ │ │ -79434   UID                 00000000 (0)
│ │ │ │ -79438   GID Size            04 (4)
│ │ │ │ -79439   GID                 00000000 (0)
│ │ │ │ -7943D PAYLOAD
│ │ │ │ -
│ │ │ │ -79E81 LOCAL HEADER #65      04034B50 (67324752)
│ │ │ │ -79E85 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -79E86 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -79E87 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -79E89 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -79E8B Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -79E8F CRC                   34AC5B41 (883710785)
│ │ │ │ -79E93 Compressed Size       00002591 (9617)
│ │ │ │ -79E97 Uncompressed Size     0000BAA4 (47780)
│ │ │ │ -79E9B Filename Length       0019 (25)
│ │ │ │ -79E9D Extra Length          001C (28)
│ │ │ │ -79E9F Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x79E9F: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -79EB8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -79EBA   Length              0009 (9)
│ │ │ │ -79EBC   Flags               03 (3) 'Modification Access'
│ │ │ │ -79EBD   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -79EC1   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -79EC5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -79EC7   Length              000B (11)
│ │ │ │ -79EC9   Version             01 (1)
│ │ │ │ -79ECA   UID Size            04 (4)
│ │ │ │ -79ECB   UID                 00000000 (0)
│ │ │ │ -79ECF   GID Size            04 (4)
│ │ │ │ -79ED0   GID                 00000000 (0)
│ │ │ │ -79ED4 PAYLOAD
│ │ │ │ -
│ │ │ │ -7C465 LOCAL HEADER #66      04034B50 (67324752)
│ │ │ │ -7C469 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -7C46A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -7C46B General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -7C46D Compression Method    0008 (8) 'Deflated'
│ │ │ │ -7C46F Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7C473 CRC                   97E60E7F (2548436607)
│ │ │ │ -7C477 Compressed Size       00000EFD (3837)
│ │ │ │ -7C47B Uncompressed Size     00003A2F (14895)
│ │ │ │ -7C47F Filename Length       0024 (36)
│ │ │ │ -7C481 Extra Length          001C (28)
│ │ │ │ -7C483 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x7C483: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -7C4A7 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -7C4A9   Length              0009 (9)
│ │ │ │ -7C4AB   Flags               03 (3) 'Modification Access'
│ │ │ │ -7C4AC   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7C4B0   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7C4B4 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -7C4B6   Length              000B (11)
│ │ │ │ -7C4B8   Version             01 (1)
│ │ │ │ -7C4B9   UID Size            04 (4)
│ │ │ │ -7C4BA   UID                 00000000 (0)
│ │ │ │ -7C4BE   GID Size            04 (4)
│ │ │ │ -7C4BF   GID                 00000000 (0)
│ │ │ │ -7C4C3 PAYLOAD
│ │ │ │ -
│ │ │ │ -7D3C0 LOCAL HEADER #67      04034B50 (67324752)
│ │ │ │ -7D3C4 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -7D3C5 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -7D3C6 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -7D3C8 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -7D3CA Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7D3CE CRC                   247F076B (612304747)
│ │ │ │ -7D3D2 Compressed Size       00001AEA (6890)
│ │ │ │ -7D3D6 Uncompressed Size     00005F7F (24447)
│ │ │ │ -7D3DA Filename Length       0017 (23)
│ │ │ │ -7D3DC Extra Length          001C (28)
│ │ │ │ -7D3DE Filename              'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x7D3DE: Filename 'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -7D3F5 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -7D3F7   Length              0009 (9)
│ │ │ │ -7D3F9   Flags               03 (3) 'Modification Access'
│ │ │ │ -7D3FA   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7D3FE   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7D402 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -7D404   Length              000B (11)
│ │ │ │ -7D406   Version             01 (1)
│ │ │ │ -7D407   UID Size            04 (4)
│ │ │ │ -7D408   UID                 00000000 (0)
│ │ │ │ -7D40C   GID Size            04 (4)
│ │ │ │ -7D40D   GID                 00000000 (0)
│ │ │ │ -7D411 PAYLOAD
│ │ │ │ -
│ │ │ │ -7EEFB LOCAL HEADER #68      04034B50 (67324752)
│ │ │ │ -7EEFF Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -7EF00 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -7EF01 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -7EF03 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -7EF05 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7EF09 CRC                   11E32AF1 (300100337)
│ │ │ │ -7EF0D Compressed Size       00000ED3 (3795)
│ │ │ │ -7EF11 Uncompressed Size     000038E2 (14562)
│ │ │ │ -7EF15 Filename Length       0023 (35)
│ │ │ │ -7EF17 Extra Length          001C (28)
│ │ │ │ -7EF19 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x7EF19: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -7EF3C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -7EF3E   Length              0009 (9)
│ │ │ │ -7EF40   Flags               03 (3) 'Modification Access'
│ │ │ │ -7EF41   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7EF45   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7EF49 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -7EF4B   Length              000B (11)
│ │ │ │ -7EF4D   Version             01 (1)
│ │ │ │ -7EF4E   UID Size            04 (4)
│ │ │ │ -7EF4F   UID                 00000000 (0)
│ │ │ │ -7EF53   GID Size            04 (4)
│ │ │ │ -7EF54   GID                 00000000 (0)
│ │ │ │ -7EF58 PAYLOAD
│ │ │ │ -
│ │ │ │ -7FE2B LOCAL HEADER #69      04034B50 (67324752)
│ │ │ │ -7FE2F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -7FE30 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -7FE31 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -7FE33 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -7FE35 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7FE39 CRC                   2DB7929F (767005343)
│ │ │ │ -7FE3D Compressed Size       00000113 (275)
│ │ │ │ -7FE41 Uncompressed Size     000001F3 (499)
│ │ │ │ -7FE45 Filename Length       001B (27)
│ │ │ │ -7FE47 Extra Length          001C (28)
│ │ │ │ -7FE49 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x7FE49: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -7FE64 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -7FE66   Length              0009 (9)
│ │ │ │ -7FE68   Flags               03 (3) 'Modification Access'
│ │ │ │ -7FE69   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7FE6D   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7FE71 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -7FE73   Length              000B (11)
│ │ │ │ -7FE75   Version             01 (1)
│ │ │ │ -7FE76   UID Size            04 (4)
│ │ │ │ -7FE77   UID                 00000000 (0)
│ │ │ │ -7FE7B   GID Size            04 (4)
│ │ │ │ -7FE7C   GID                 00000000 (0)
│ │ │ │ -7FE80 PAYLOAD
│ │ │ │ -
│ │ │ │ -7FF93 LOCAL HEADER #70      04034B50 (67324752)
│ │ │ │ -7FF97 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -7FF98 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -7FF99 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -7FF9B Compression Method    0008 (8) 'Deflated'
│ │ │ │ -7FF9D Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7FFA1 CRC                   3E2ED2F5 (1043256053)
│ │ │ │ -7FFA5 Compressed Size       0000188D (6285)
│ │ │ │ -7FFA9 Uncompressed Size     00008FA8 (36776)
│ │ │ │ -7FFAD Filename Length       001D (29)
│ │ │ │ -7FFAF Extra Length          001C (28)
│ │ │ │ -7FFB1 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x7FFB1: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -7FFCE Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -7FFD0   Length              0009 (9)
│ │ │ │ -7FFD2   Flags               03 (3) 'Modification Access'
│ │ │ │ -7FFD3   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7FFD7   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -7FFDB Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -7FFDD   Length              000B (11)
│ │ │ │ -7FFDF   Version             01 (1)
│ │ │ │ -7FFE0   UID Size            04 (4)
│ │ │ │ -7FFE1   UID                 00000000 (0)
│ │ │ │ -7FFE5   GID Size            04 (4)
│ │ │ │ -7FFE6   GID                 00000000 (0)
│ │ │ │ -7FFEA PAYLOAD
│ │ │ │ -
│ │ │ │ -81877 LOCAL HEADER #71      04034B50 (67324752)
│ │ │ │ -8187B Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -8187C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -8187D General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -8187F Compression Method    0008 (8) 'Deflated'
│ │ │ │ -81881 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -81885 CRC                   13F8A234 (335061556)
│ │ │ │ -81889 Compressed Size       0000164C (5708)
│ │ │ │ -8188D Uncompressed Size     00003A9B (15003)
│ │ │ │ -81891 Filename Length       0015 (21)
│ │ │ │ -81893 Extra Length          001C (28)
│ │ │ │ -81895 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x81895: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -818AA Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -818AC   Length              0009 (9)
│ │ │ │ -818AE   Flags               03 (3) 'Modification Access'
│ │ │ │ -818AF   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -818B3   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -818B7 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -818B9   Length              000B (11)
│ │ │ │ -818BB   Version             01 (1)
│ │ │ │ -818BC   UID Size            04 (4)
│ │ │ │ -818BD   UID                 00000000 (0)
│ │ │ │ -818C1   GID Size            04 (4)
│ │ │ │ -818C2   GID                 00000000 (0)
│ │ │ │ -818C6 PAYLOAD
│ │ │ │ -
│ │ │ │ -82F12 LOCAL HEADER #72      04034B50 (67324752)
│ │ │ │ -82F16 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -82F17 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -82F18 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -82F1A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -82F1C Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -82F20 CRC                   945176DD (2488366813)
│ │ │ │ -82F24 Compressed Size       000040CE (16590)
│ │ │ │ -82F28 Uncompressed Size     000133AC (78764)
│ │ │ │ -82F2C Filename Length       0016 (22)
│ │ │ │ -82F2E Extra Length          001C (28)
│ │ │ │ -82F30 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x82F30: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -82F46 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -82F48   Length              0009 (9)
│ │ │ │ -82F4A   Flags               03 (3) 'Modification Access'
│ │ │ │ -82F4B   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -82F4F   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -82F53 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -82F55   Length              000B (11)
│ │ │ │ -82F57   Version             01 (1)
│ │ │ │ -82F58   UID Size            04 (4)
│ │ │ │ -82F59   UID                 00000000 (0)
│ │ │ │ -82F5D   GID Size            04 (4)
│ │ │ │ -82F5E   GID                 00000000 (0)
│ │ │ │ -82F62 PAYLOAD
│ │ │ │ +00DCD LOCAL HEADER #3       04034B50 (67324752)
│ │ │ │ +00DD1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +00DD2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +00DD3 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +00DD5 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +00DD7 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +00DDB CRC                   546A35FD (1416246781)
│ │ │ │ +00DDF Compressed Size       000015B1 (5553)
│ │ │ │ +00DE3 Uncompressed Size     00004605 (17925)
│ │ │ │ +00DE7 Filename Length       0014 (20)
│ │ │ │ +00DE9 Extra Length          001C (28)
│ │ │ │ +00DEB Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xDEB: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +00DFF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +00E01   Length              0009 (9)
│ │ │ │ +00E03   Flags               03 (3) 'Modification Access'
│ │ │ │ +00E04   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +00E08   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +00E0C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +00E0E   Length              000B (11)
│ │ │ │ +00E10   Version             01 (1)
│ │ │ │ +00E11   UID Size            04 (4)
│ │ │ │ +00E12   UID                 00000000 (0)
│ │ │ │ +00E16   GID Size            04 (4)
│ │ │ │ +00E17   GID                 00000000 (0)
│ │ │ │ +00E1B PAYLOAD
│ │ │ │ +
│ │ │ │ +023CC LOCAL HEADER #4       04034B50 (67324752)
│ │ │ │ +023D0 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +023D1 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +023D2 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +023D4 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +023D6 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +023DA CRC                   03A4A46E (61121646)
│ │ │ │ +023DE Compressed Size       000006D4 (1748)
│ │ │ │ +023E2 Uncompressed Size     00001241 (4673)
│ │ │ │ +023E6 Filename Length       0013 (19)
│ │ │ │ +023E8 Extra Length          001C (28)
│ │ │ │ +023EA Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x23EA: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +023FD Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +023FF   Length              0009 (9)
│ │ │ │ +02401   Flags               03 (3) 'Modification Access'
│ │ │ │ +02402   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +02406   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +0240A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +0240C   Length              000B (11)
│ │ │ │ +0240E   Version             01 (1)
│ │ │ │ +0240F   UID Size            04 (4)
│ │ │ │ +02410   UID                 00000000 (0)
│ │ │ │ +02414   GID Size            04 (4)
│ │ │ │ +02415   GID                 00000000 (0)
│ │ │ │ +02419 PAYLOAD
│ │ │ │ +
│ │ │ │ +02AED LOCAL HEADER #5       04034B50 (67324752)
│ │ │ │ +02AF1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +02AF2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +02AF3 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +02AF5 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +02AF7 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +02AFB CRC                   69D3269E (1775445662)
│ │ │ │ +02AFF Compressed Size       00002E70 (11888)
│ │ │ │ +02B03 Uncompressed Size     0000D4C1 (54465)
│ │ │ │ +02B07 Filename Length       0014 (20)
│ │ │ │ +02B09 Extra Length          001C (28)
│ │ │ │ +02B0B Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x2B0B: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +02B1F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +02B21   Length              0009 (9)
│ │ │ │ +02B23   Flags               03 (3) 'Modification Access'
│ │ │ │ +02B24   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +02B28   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +02B2C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +02B2E   Length              000B (11)
│ │ │ │ +02B30   Version             01 (1)
│ │ │ │ +02B31   UID Size            04 (4)
│ │ │ │ +02B32   UID                 00000000 (0)
│ │ │ │ +02B36   GID Size            04 (4)
│ │ │ │ +02B37   GID                 00000000 (0)
│ │ │ │ +02B3B PAYLOAD
│ │ │ │ +
│ │ │ │ +059AB LOCAL HEADER #6       04034B50 (67324752)
│ │ │ │ +059AF Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +059B0 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +059B1 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +059B3 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +059B5 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +059B9 CRC                   272DD323 (657314595)
│ │ │ │ +059BD Compressed Size       000003EF (1007)
│ │ │ │ +059C1 Uncompressed Size     00000876 (2166)
│ │ │ │ +059C5 Filename Length       0014 (20)
│ │ │ │ +059C7 Extra Length          001C (28)
│ │ │ │ +059C9 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x59C9: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +059DD Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +059DF   Length              0009 (9)
│ │ │ │ +059E1   Flags               03 (3) 'Modification Access'
│ │ │ │ +059E2   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +059E6   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +059EA Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +059EC   Length              000B (11)
│ │ │ │ +059EE   Version             01 (1)
│ │ │ │ +059EF   UID Size            04 (4)
│ │ │ │ +059F0   UID                 00000000 (0)
│ │ │ │ +059F4   GID Size            04 (4)
│ │ │ │ +059F5   GID                 00000000 (0)
│ │ │ │ +059F9 PAYLOAD
│ │ │ │ +
│ │ │ │ +05DE8 LOCAL HEADER #7       04034B50 (67324752)
│ │ │ │ +05DEC Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +05DED Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +05DEE General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +05DF0 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +05DF2 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +05DF6 CRC                   2F07766F (789018223)
│ │ │ │ +05DFA Compressed Size       000001AD (429)
│ │ │ │ +05DFE Uncompressed Size     000002FC (764)
│ │ │ │ +05E02 Filename Length       0011 (17)
│ │ │ │ +05E04 Extra Length          001C (28)
│ │ │ │ +05E06 Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x5E06: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +05E17 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +05E19   Length              0009 (9)
│ │ │ │ +05E1B   Flags               03 (3) 'Modification Access'
│ │ │ │ +05E1C   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +05E20   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +05E24 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +05E26   Length              000B (11)
│ │ │ │ +05E28   Version             01 (1)
│ │ │ │ +05E29   UID Size            04 (4)
│ │ │ │ +05E2A   UID                 00000000 (0)
│ │ │ │ +05E2E   GID Size            04 (4)
│ │ │ │ +05E2F   GID                 00000000 (0)
│ │ │ │ +05E33 PAYLOAD
│ │ │ │ +
│ │ │ │ +05FE0 LOCAL HEADER #8       04034B50 (67324752)
│ │ │ │ +05FE4 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +05FE5 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +05FE6 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +05FE8 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +05FEA Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +05FEE CRC                   2E830899 (780339353)
│ │ │ │ +05FF2 Compressed Size       000020BD (8381)
│ │ │ │ +05FF6 Uncompressed Size     0000B4B1 (46257)
│ │ │ │ +05FFA Filename Length       001B (27)
│ │ │ │ +05FFC Extra Length          001C (28)
│ │ │ │ +05FFE Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x5FFE: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +06019 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +0601B   Length              0009 (9)
│ │ │ │ +0601D   Flags               03 (3) 'Modification Access'
│ │ │ │ +0601E   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +06022   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +06026 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +06028   Length              000B (11)
│ │ │ │ +0602A   Version             01 (1)
│ │ │ │ +0602B   UID Size            04 (4)
│ │ │ │ +0602C   UID                 00000000 (0)
│ │ │ │ +06030   GID Size            04 (4)
│ │ │ │ +06031   GID                 00000000 (0)
│ │ │ │ +06035 PAYLOAD
│ │ │ │ +
│ │ │ │ +080F2 LOCAL HEADER #9       04034B50 (67324752)
│ │ │ │ +080F6 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +080F7 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +080F8 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +080FA Compression Method    0008 (8) 'Deflated'
│ │ │ │ +080FC Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +08100 CRC                   4E72FA06 (1316157958)
│ │ │ │ +08104 Compressed Size       00000E68 (3688)
│ │ │ │ +08108 Uncompressed Size     00003097 (12439)
│ │ │ │ +0810C Filename Length       001D (29)
│ │ │ │ +0810E Extra Length          001C (28)
│ │ │ │ +08110 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x8110: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +0812D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +0812F   Length              0009 (9)
│ │ │ │ +08131   Flags               03 (3) 'Modification Access'
│ │ │ │ +08132   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +08136   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +0813A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +0813C   Length              000B (11)
│ │ │ │ +0813E   Version             01 (1)
│ │ │ │ +0813F   UID Size            04 (4)
│ │ │ │ +08140   UID                 00000000 (0)
│ │ │ │ +08144   GID Size            04 (4)
│ │ │ │ +08145   GID                 00000000 (0)
│ │ │ │ +08149 PAYLOAD
│ │ │ │ +
│ │ │ │ +08FB1 LOCAL HEADER #10      04034B50 (67324752)
│ │ │ │ +08FB5 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +08FB6 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +08FB7 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +08FB9 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +08FBB Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +08FBF CRC                   F138337A (4046992250)
│ │ │ │ +08FC3 Compressed Size       0000098E (2446)
│ │ │ │ +08FC7 Uncompressed Size     00001D39 (7481)
│ │ │ │ +08FCB Filename Length       0019 (25)
│ │ │ │ +08FCD Extra Length          001C (28)
│ │ │ │ +08FCF Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x8FCF: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +08FE8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +08FEA   Length              0009 (9)
│ │ │ │ +08FEC   Flags               03 (3) 'Modification Access'
│ │ │ │ +08FED   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +08FF1   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +08FF5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +08FF7   Length              000B (11)
│ │ │ │ +08FF9   Version             01 (1)
│ │ │ │ +08FFA   UID Size            04 (4)
│ │ │ │ +08FFB   UID                 00000000 (0)
│ │ │ │ +08FFF   GID Size            04 (4)
│ │ │ │ +09000   GID                 00000000 (0)
│ │ │ │ +09004 PAYLOAD
│ │ │ │ +
│ │ │ │ +09992 LOCAL HEADER #11      04034B50 (67324752)
│ │ │ │ +09996 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +09997 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +09998 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +0999A Compression Method    0008 (8) 'Deflated'
│ │ │ │ +0999C Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +099A0 CRC                   42AE2C47 (1118710855)
│ │ │ │ +099A4 Compressed Size       00003887 (14471)
│ │ │ │ +099A8 Uncompressed Size     0000F81F (63519)
│ │ │ │ +099AC Filename Length       0015 (21)
│ │ │ │ +099AE Extra Length          001C (28)
│ │ │ │ +099B0 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x99B0: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +099C5 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +099C7   Length              0009 (9)
│ │ │ │ +099C9   Flags               03 (3) 'Modification Access'
│ │ │ │ +099CA   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +099CE   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +099D2 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +099D4   Length              000B (11)
│ │ │ │ +099D6   Version             01 (1)
│ │ │ │ +099D7   UID Size            04 (4)
│ │ │ │ +099D8   UID                 00000000 (0)
│ │ │ │ +099DC   GID Size            04 (4)
│ │ │ │ +099DD   GID                 00000000 (0)
│ │ │ │ +099E1 PAYLOAD
│ │ │ │ +
│ │ │ │ +0D268 LOCAL HEADER #12      04034B50 (67324752)
│ │ │ │ +0D26C Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +0D26D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +0D26E General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +0D270 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +0D272 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +0D276 CRC                   BCFA2578 (3170510200)
│ │ │ │ +0D27A Compressed Size       0000AB01 (43777)
│ │ │ │ +0D27E Uncompressed Size     0003E0D8 (254168)
│ │ │ │ +0D282 Filename Length       0012 (18)
│ │ │ │ +0D284 Extra Length          001C (28)
│ │ │ │ +0D286 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xD286: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +0D298 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +0D29A   Length              0009 (9)
│ │ │ │ +0D29C   Flags               03 (3) 'Modification Access'
│ │ │ │ +0D29D   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +0D2A1   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +0D2A5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +0D2A7   Length              000B (11)
│ │ │ │ +0D2A9   Version             01 (1)
│ │ │ │ +0D2AA   UID Size            04 (4)
│ │ │ │ +0D2AB   UID                 00000000 (0)
│ │ │ │ +0D2AF   GID Size            04 (4)
│ │ │ │ +0D2B0   GID                 00000000 (0)
│ │ │ │ +0D2B4 PAYLOAD
│ │ │ │ +
│ │ │ │ +17DB5 LOCAL HEADER #13      04034B50 (67324752)
│ │ │ │ +17DB9 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +17DBA Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +17DBB General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +17DBD Compression Method    0008 (8) 'Deflated'
│ │ │ │ +17DBF Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +17DC3 CRC                   52E3F286 (1390670470)
│ │ │ │ +17DC7 Compressed Size       00003AF8 (15096)
│ │ │ │ +17DCB Uncompressed Size     0001B421 (111649)
│ │ │ │ +17DCF Filename Length       0015 (21)
│ │ │ │ +17DD1 Extra Length          001C (28)
│ │ │ │ +17DD3 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x17DD3: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +17DE8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +17DEA   Length              0009 (9)
│ │ │ │ +17DEC   Flags               03 (3) 'Modification Access'
│ │ │ │ +17DED   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +17DF1   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +17DF5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +17DF7   Length              000B (11)
│ │ │ │ +17DF9   Version             01 (1)
│ │ │ │ +17DFA   UID Size            04 (4)
│ │ │ │ +17DFB   UID                 00000000 (0)
│ │ │ │ +17DFF   GID Size            04 (4)
│ │ │ │ +17E00   GID                 00000000 (0)
│ │ │ │ +17E04 PAYLOAD
│ │ │ │ +
│ │ │ │ +1B8FC LOCAL HEADER #14      04034B50 (67324752)
│ │ │ │ +1B900 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +1B901 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +1B902 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +1B904 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +1B906 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +1B90A CRC                   DBC5E740 (3687180096)
│ │ │ │ +1B90E Compressed Size       000091CA (37322)
│ │ │ │ +1B912 Uncompressed Size     0003DBD1 (252881)
│ │ │ │ +1B916 Filename Length       0014 (20)
│ │ │ │ +1B918 Extra Length          001C (28)
│ │ │ │ +1B91A Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x1B91A: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +1B92E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +1B930   Length              0009 (9)
│ │ │ │ +1B932   Flags               03 (3) 'Modification Access'
│ │ │ │ +1B933   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +1B937   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +1B93B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +1B93D   Length              000B (11)
│ │ │ │ +1B93F   Version             01 (1)
│ │ │ │ +1B940   UID Size            04 (4)
│ │ │ │ +1B941   UID                 00000000 (0)
│ │ │ │ +1B945   GID Size            04 (4)
│ │ │ │ +1B946   GID                 00000000 (0)
│ │ │ │ +1B94A PAYLOAD
│ │ │ │ +
│ │ │ │ +24B14 LOCAL HEADER #15      04034B50 (67324752)
│ │ │ │ +24B18 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +24B19 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +24B1A General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +24B1C Compression Method    0008 (8) 'Deflated'
│ │ │ │ +24B1E Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +24B22 CRC                   953AA54E (2503648590)
│ │ │ │ +24B26 Compressed Size       00009BA8 (39848)
│ │ │ │ +24B2A Uncompressed Size     00027CF5 (163061)
│ │ │ │ +24B2E Filename Length       0019 (25)
│ │ │ │ +24B30 Extra Length          001C (28)
│ │ │ │ +24B32 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x24B32: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +24B4B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +24B4D   Length              0009 (9)
│ │ │ │ +24B4F   Flags               03 (3) 'Modification Access'
│ │ │ │ +24B50   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +24B54   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +24B58 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +24B5A   Length              000B (11)
│ │ │ │ +24B5C   Version             01 (1)
│ │ │ │ +24B5D   UID Size            04 (4)
│ │ │ │ +24B5E   UID                 00000000 (0)
│ │ │ │ +24B62   GID Size            04 (4)
│ │ │ │ +24B63   GID                 00000000 (0)
│ │ │ │ +24B67 PAYLOAD
│ │ │ │ +
│ │ │ │ +2E70F LOCAL HEADER #16      04034B50 (67324752)
│ │ │ │ +2E713 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +2E714 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +2E715 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +2E717 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +2E719 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +2E71D CRC                   36D4AE72 (919907954)
│ │ │ │ +2E721 Compressed Size       00001219 (4633)
│ │ │ │ +2E725 Uncompressed Size     00003C91 (15505)
│ │ │ │ +2E729 Filename Length       0010 (16)
│ │ │ │ +2E72B Extra Length          001C (28)
│ │ │ │ +2E72D Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x2E72D: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +2E73D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +2E73F   Length              0009 (9)
│ │ │ │ +2E741   Flags               03 (3) 'Modification Access'
│ │ │ │ +2E742   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +2E746   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +2E74A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +2E74C   Length              000B (11)
│ │ │ │ +2E74E   Version             01 (1)
│ │ │ │ +2E74F   UID Size            04 (4)
│ │ │ │ +2E750   UID                 00000000 (0)
│ │ │ │ +2E754   GID Size            04 (4)
│ │ │ │ +2E755   GID                 00000000 (0)
│ │ │ │ +2E759 PAYLOAD
│ │ │ │ +
│ │ │ │ +2F972 LOCAL HEADER #17      04034B50 (67324752)
│ │ │ │ +2F976 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +2F977 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +2F978 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +2F97A Compression Method    0008 (8) 'Deflated'
│ │ │ │ +2F97C Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +2F980 CRC                   6E6B7F3A (1852538682)
│ │ │ │ +2F984 Compressed Size       00002A60 (10848)
│ │ │ │ +2F988 Uncompressed Size     000113A7 (70567)
│ │ │ │ +2F98C Filename Length       0016 (22)
│ │ │ │ +2F98E Extra Length          001C (28)
│ │ │ │ +2F990 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x2F990: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +2F9A6 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +2F9A8   Length              0009 (9)
│ │ │ │ +2F9AA   Flags               03 (3) 'Modification Access'
│ │ │ │ +2F9AB   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +2F9AF   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +2F9B3 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +2F9B5   Length              000B (11)
│ │ │ │ +2F9B7   Version             01 (1)
│ │ │ │ +2F9B8   UID Size            04 (4)
│ │ │ │ +2F9B9   UID                 00000000 (0)
│ │ │ │ +2F9BD   GID Size            04 (4)
│ │ │ │ +2F9BE   GID                 00000000 (0)
│ │ │ │ +2F9C2 PAYLOAD
│ │ │ │ +
│ │ │ │ +32422 LOCAL HEADER #18      04034B50 (67324752)
│ │ │ │ +32426 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +32427 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +32428 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +3242A Compression Method    0008 (8) 'Deflated'
│ │ │ │ +3242C Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +32430 CRC                   EC084A66 (3959966310)
│ │ │ │ +32434 Compressed Size       000014D8 (5336)
│ │ │ │ +32438 Uncompressed Size     0000518D (20877)
│ │ │ │ +3243C Filename Length       001D (29)
│ │ │ │ +3243E Extra Length          001C (28)
│ │ │ │ +32440 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x32440: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +3245D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +3245F   Length              0009 (9)
│ │ │ │ +32461   Flags               03 (3) 'Modification Access'
│ │ │ │ +32462   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +32466   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +3246A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +3246C   Length              000B (11)
│ │ │ │ +3246E   Version             01 (1)
│ │ │ │ +3246F   UID Size            04 (4)
│ │ │ │ +32470   UID                 00000000 (0)
│ │ │ │ +32474   GID Size            04 (4)
│ │ │ │ +32475   GID                 00000000 (0)
│ │ │ │ +32479 PAYLOAD
│ │ │ │ +
│ │ │ │ +33951 LOCAL HEADER #19      04034B50 (67324752)
│ │ │ │ +33955 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +33956 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +33957 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +33959 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +3395B Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +3395F CRC                   C2410B8F (3259042703)
│ │ │ │ +33963 Compressed Size       00003805 (14341)
│ │ │ │ +33967 Uncompressed Size     0000EA4B (59979)
│ │ │ │ +3396B Filename Length       001C (28)
│ │ │ │ +3396D Extra Length          001C (28)
│ │ │ │ +3396F Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x3396F: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +3398B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +3398D   Length              0009 (9)
│ │ │ │ +3398F   Flags               03 (3) 'Modification Access'
│ │ │ │ +33990   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +33994   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +33998 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +3399A   Length              000B (11)
│ │ │ │ +3399C   Version             01 (1)
│ │ │ │ +3399D   UID Size            04 (4)
│ │ │ │ +3399E   UID                 00000000 (0)
│ │ │ │ +339A2   GID Size            04 (4)
│ │ │ │ +339A3   GID                 00000000 (0)
│ │ │ │ +339A7 PAYLOAD
│ │ │ │ +
│ │ │ │ +371AC LOCAL HEADER #20      04034B50 (67324752)
│ │ │ │ +371B0 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +371B1 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +371B2 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +371B4 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +371B6 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +371BA CRC                   958EC234 (2509161012)
│ │ │ │ +371BE Compressed Size       0000069E (1694)
│ │ │ │ +371C2 Uncompressed Size     000011F3 (4595)
│ │ │ │ +371C6 Filename Length       001C (28)
│ │ │ │ +371C8 Extra Length          001C (28)
│ │ │ │ +371CA Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x371CA: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +371E6 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +371E8   Length              0009 (9)
│ │ │ │ +371EA   Flags               03 (3) 'Modification Access'
│ │ │ │ +371EB   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +371EF   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +371F3 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +371F5   Length              000B (11)
│ │ │ │ +371F7   Version             01 (1)
│ │ │ │ +371F8   UID Size            04 (4)
│ │ │ │ +371F9   UID                 00000000 (0)
│ │ │ │ +371FD   GID Size            04 (4)
│ │ │ │ +371FE   GID                 00000000 (0)
│ │ │ │ +37202 PAYLOAD
│ │ │ │ +
│ │ │ │ +378A0 LOCAL HEADER #21      04034B50 (67324752)
│ │ │ │ +378A4 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +378A5 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +378A6 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +378A8 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +378AA Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +378AE CRC                   EE3DA990 (3997018512)
│ │ │ │ +378B2 Compressed Size       0000107C (4220)
│ │ │ │ +378B6 Uncompressed Size     00004BFE (19454)
│ │ │ │ +378BA Filename Length       001B (27)
│ │ │ │ +378BC Extra Length          001C (28)
│ │ │ │ +378BE Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x378BE: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +378D9 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +378DB   Length              0009 (9)
│ │ │ │ +378DD   Flags               03 (3) 'Modification Access'
│ │ │ │ +378DE   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +378E2   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +378E6 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +378E8   Length              000B (11)
│ │ │ │ +378EA   Version             01 (1)
│ │ │ │ +378EB   UID Size            04 (4)
│ │ │ │ +378EC   UID                 00000000 (0)
│ │ │ │ +378F0   GID Size            04 (4)
│ │ │ │ +378F1   GID                 00000000 (0)
│ │ │ │ +378F5 PAYLOAD
│ │ │ │ +
│ │ │ │ +38971 LOCAL HEADER #22      04034B50 (67324752)
│ │ │ │ +38975 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +38976 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +38977 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +38979 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +3897B Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +3897F CRC                   045E51FF (73290239)
│ │ │ │ +38983 Compressed Size       00003B3B (15163)
│ │ │ │ +38987 Uncompressed Size     0000D491 (54417)
│ │ │ │ +3898B Filename Length       001D (29)
│ │ │ │ +3898D Extra Length          001C (28)
│ │ │ │ +3898F Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x3898F: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +389AC Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +389AE   Length              0009 (9)
│ │ │ │ +389B0   Flags               03 (3) 'Modification Access'
│ │ │ │ +389B1   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +389B5   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +389B9 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +389BB   Length              000B (11)
│ │ │ │ +389BD   Version             01 (1)
│ │ │ │ +389BE   UID Size            04 (4)
│ │ │ │ +389BF   UID                 00000000 (0)
│ │ │ │ +389C3   GID Size            04 (4)
│ │ │ │ +389C4   GID                 00000000 (0)
│ │ │ │ +389C8 PAYLOAD
│ │ │ │ +
│ │ │ │ +3C503 LOCAL HEADER #23      04034B50 (67324752)
│ │ │ │ +3C507 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +3C508 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +3C509 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +3C50B Compression Method    0008 (8) 'Deflated'
│ │ │ │ +3C50D Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +3C511 CRC                   C52CC238 (3308044856)
│ │ │ │ +3C515 Compressed Size       00000D6A (3434)
│ │ │ │ +3C519 Uncompressed Size     0000388A (14474)
│ │ │ │ +3C51D Filename Length       001D (29)
│ │ │ │ +3C51F Extra Length          001C (28)
│ │ │ │ +3C521 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x3C521: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +3C53E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +3C540   Length              0009 (9)
│ │ │ │ +3C542   Flags               03 (3) 'Modification Access'
│ │ │ │ +3C543   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +3C547   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +3C54B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +3C54D   Length              000B (11)
│ │ │ │ +3C54F   Version             01 (1)
│ │ │ │ +3C550   UID Size            04 (4)
│ │ │ │ +3C551   UID                 00000000 (0)
│ │ │ │ +3C555   GID Size            04 (4)
│ │ │ │ +3C556   GID                 00000000 (0)
│ │ │ │ +3C55A PAYLOAD
│ │ │ │ +
│ │ │ │ +3D2C4 LOCAL HEADER #24      04034B50 (67324752)
│ │ │ │ +3D2C8 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +3D2C9 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +3D2CA General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +3D2CC Compression Method    0008 (8) 'Deflated'
│ │ │ │ +3D2CE Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +3D2D2 CRC                   0BFFA3F1 (201303025)
│ │ │ │ +3D2D6 Compressed Size       00001C89 (7305)
│ │ │ │ +3D2DA Uncompressed Size     0000C038 (49208)
│ │ │ │ +3D2DE Filename Length       001A (26)
│ │ │ │ +3D2E0 Extra Length          001C (28)
│ │ │ │ +3D2E2 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x3D2E2: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +3D2FC Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +3D2FE   Length              0009 (9)
│ │ │ │ +3D300   Flags               03 (3) 'Modification Access'
│ │ │ │ +3D301   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +3D305   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +3D309 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +3D30B   Length              000B (11)
│ │ │ │ +3D30D   Version             01 (1)
│ │ │ │ +3D30E   UID Size            04 (4)
│ │ │ │ +3D30F   UID                 00000000 (0)
│ │ │ │ +3D313   GID Size            04 (4)
│ │ │ │ +3D314   GID                 00000000 (0)
│ │ │ │ +3D318 PAYLOAD
│ │ │ │ +
│ │ │ │ +3EFA1 LOCAL HEADER #25      04034B50 (67324752)
│ │ │ │ +3EFA5 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +3EFA6 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +3EFA7 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +3EFA9 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +3EFAB Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +3EFAF CRC                   478B6B96 (1200319382)
│ │ │ │ +3EFB3 Compressed Size       000003DF (991)
│ │ │ │ +3EFB7 Uncompressed Size     00000935 (2357)
│ │ │ │ +3EFBB Filename Length       0012 (18)
│ │ │ │ +3EFBD Extra Length          001C (28)
│ │ │ │ +3EFBF Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x3EFBF: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +3EFD1 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +3EFD3   Length              0009 (9)
│ │ │ │ +3EFD5   Flags               03 (3) 'Modification Access'
│ │ │ │ +3EFD6   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +3EFDA   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +3EFDE Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +3EFE0   Length              000B (11)
│ │ │ │ +3EFE2   Version             01 (1)
│ │ │ │ +3EFE3   UID Size            04 (4)
│ │ │ │ +3EFE4   UID                 00000000 (0)
│ │ │ │ +3EFE8   GID Size            04 (4)
│ │ │ │ +3EFE9   GID                 00000000 (0)
│ │ │ │ +3EFED PAYLOAD
│ │ │ │ +
│ │ │ │ +3F3CC LOCAL HEADER #26      04034B50 (67324752)
│ │ │ │ +3F3D0 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +3F3D1 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +3F3D2 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +3F3D4 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +3F3D6 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +3F3DA CRC                   E79489F0 (3885271536)
│ │ │ │ +3F3DE Compressed Size       000001D3 (467)
│ │ │ │ +3F3E2 Uncompressed Size     00000311 (785)
│ │ │ │ +3F3E6 Filename Length       0020 (32)
│ │ │ │ +3F3E8 Extra Length          001C (28)
│ │ │ │ +3F3EA Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x3F3EA: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +3F40A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +3F40C   Length              0009 (9)
│ │ │ │ +3F40E   Flags               03 (3) 'Modification Access'
│ │ │ │ +3F40F   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +3F413   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +3F417 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +3F419   Length              000B (11)
│ │ │ │ +3F41B   Version             01 (1)
│ │ │ │ +3F41C   UID Size            04 (4)
│ │ │ │ +3F41D   UID                 00000000 (0)
│ │ │ │ +3F421   GID Size            04 (4)
│ │ │ │ +3F422   GID                 00000000 (0)
│ │ │ │ +3F426 PAYLOAD
│ │ │ │ +
│ │ │ │ +3F5F9 LOCAL HEADER #27      04034B50 (67324752)
│ │ │ │ +3F5FD Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +3F5FE Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +3F5FF General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +3F601 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +3F603 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +3F607 CRC                   73552FFE (1934962686)
│ │ │ │ +3F60B Compressed Size       000017AB (6059)
│ │ │ │ +3F60F Uncompressed Size     00009D1B (40219)
│ │ │ │ +3F613 Filename Length       001B (27)
│ │ │ │ +3F615 Extra Length          001C (28)
│ │ │ │ +3F617 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x3F617: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +3F632 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +3F634   Length              0009 (9)
│ │ │ │ +3F636   Flags               03 (3) 'Modification Access'
│ │ │ │ +3F637   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +3F63B   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +3F63F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +3F641   Length              000B (11)
│ │ │ │ +3F643   Version             01 (1)
│ │ │ │ +3F644   UID Size            04 (4)
│ │ │ │ +3F645   UID                 00000000 (0)
│ │ │ │ +3F649   GID Size            04 (4)
│ │ │ │ +3F64A   GID                 00000000 (0)
│ │ │ │ +3F64E PAYLOAD
│ │ │ │ +
│ │ │ │ +40DF9 LOCAL HEADER #28      04034B50 (67324752)
│ │ │ │ +40DFD Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +40DFE Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +40DFF General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +40E01 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +40E03 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +40E07 CRC                   09EB9A96 (166435478)
│ │ │ │ +40E0B Compressed Size       0000136D (4973)
│ │ │ │ +40E0F Uncompressed Size     00003B58 (15192)
│ │ │ │ +40E13 Filename Length       0015 (21)
│ │ │ │ +40E15 Extra Length          001C (28)
│ │ │ │ +40E17 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x40E17: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +40E2C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +40E2E   Length              0009 (9)
│ │ │ │ +40E30   Flags               03 (3) 'Modification Access'
│ │ │ │ +40E31   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +40E35   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +40E39 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +40E3B   Length              000B (11)
│ │ │ │ +40E3D   Version             01 (1)
│ │ │ │ +40E3E   UID Size            04 (4)
│ │ │ │ +40E3F   UID                 00000000 (0)
│ │ │ │ +40E43   GID Size            04 (4)
│ │ │ │ +40E44   GID                 00000000 (0)
│ │ │ │ +40E48 PAYLOAD
│ │ │ │ +
│ │ │ │ +421B5 LOCAL HEADER #29      04034B50 (67324752)
│ │ │ │ +421B9 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +421BA Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +421BB General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +421BD Compression Method    0008 (8) 'Deflated'
│ │ │ │ +421BF Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +421C3 CRC                   F9EDEEDB (4193119963)
│ │ │ │ +421C7 Compressed Size       00000AC9 (2761)
│ │ │ │ +421CB Uncompressed Size     00002133 (8499)
│ │ │ │ +421CF Filename Length       0011 (17)
│ │ │ │ +421D1 Extra Length          001C (28)
│ │ │ │ +421D3 Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x421D3: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +421E4 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +421E6   Length              0009 (9)
│ │ │ │ +421E8   Flags               03 (3) 'Modification Access'
│ │ │ │ +421E9   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +421ED   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +421F1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +421F3   Length              000B (11)
│ │ │ │ +421F5   Version             01 (1)
│ │ │ │ +421F6   UID Size            04 (4)
│ │ │ │ +421F7   UID                 00000000 (0)
│ │ │ │ +421FB   GID Size            04 (4)
│ │ │ │ +421FC   GID                 00000000 (0)
│ │ │ │ +42200 PAYLOAD
│ │ │ │ +
│ │ │ │ +42CC9 LOCAL HEADER #30      04034B50 (67324752)
│ │ │ │ +42CCD Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +42CCE Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +42CCF General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +42CD1 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +42CD3 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +42CD7 CRC                   78F661F4 (2029412852)
│ │ │ │ +42CDB Compressed Size       000003FE (1022)
│ │ │ │ +42CDF Uncompressed Size     00000F0C (3852)
│ │ │ │ +42CE3 Filename Length       0014 (20)
│ │ │ │ +42CE5 Extra Length          001C (28)
│ │ │ │ +42CE7 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x42CE7: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +42CFB Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +42CFD   Length              0009 (9)
│ │ │ │ +42CFF   Flags               03 (3) 'Modification Access'
│ │ │ │ +42D00   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +42D04   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +42D08 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +42D0A   Length              000B (11)
│ │ │ │ +42D0C   Version             01 (1)
│ │ │ │ +42D0D   UID Size            04 (4)
│ │ │ │ +42D0E   UID                 00000000 (0)
│ │ │ │ +42D12   GID Size            04 (4)
│ │ │ │ +42D13   GID                 00000000 (0)
│ │ │ │ +42D17 PAYLOAD
│ │ │ │ +
│ │ │ │ +43115 LOCAL HEADER #31      04034B50 (67324752)
│ │ │ │ +43119 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +4311A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +4311B General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +4311D Compression Method    0008 (8) 'Deflated'
│ │ │ │ +4311F Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +43123 CRC                   3F5B0F93 (1062932371)
│ │ │ │ +43127 Compressed Size       00001260 (4704)
│ │ │ │ +4312B Uncompressed Size     0000346B (13419)
│ │ │ │ +4312F Filename Length       0014 (20)
│ │ │ │ +43131 Extra Length          001C (28)
│ │ │ │ +43133 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x43133: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +43147 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +43149   Length              0009 (9)
│ │ │ │ +4314B   Flags               03 (3) 'Modification Access'
│ │ │ │ +4314C   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +43150   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +43154 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +43156   Length              000B (11)
│ │ │ │ +43158   Version             01 (1)
│ │ │ │ +43159   UID Size            04 (4)
│ │ │ │ +4315A   UID                 00000000 (0)
│ │ │ │ +4315E   GID Size            04 (4)
│ │ │ │ +4315F   GID                 00000000 (0)
│ │ │ │ +43163 PAYLOAD
│ │ │ │ +
│ │ │ │ +443C3 LOCAL HEADER #32      04034B50 (67324752)
│ │ │ │ +443C7 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +443C8 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +443C9 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +443CB Compression Method    0008 (8) 'Deflated'
│ │ │ │ +443CD Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +443D1 CRC                   06606451 (106980433)
│ │ │ │ +443D5 Compressed Size       00000ACF (2767)
│ │ │ │ +443D9 Uncompressed Size     000022FF (8959)
│ │ │ │ +443DD Filename Length       001B (27)
│ │ │ │ +443DF Extra Length          001C (28)
│ │ │ │ +443E1 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x443E1: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +443FC Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +443FE   Length              0009 (9)
│ │ │ │ +44400   Flags               03 (3) 'Modification Access'
│ │ │ │ +44401   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +44405   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +44409 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +4440B   Length              000B (11)
│ │ │ │ +4440D   Version             01 (1)
│ │ │ │ +4440E   UID Size            04 (4)
│ │ │ │ +4440F   UID                 00000000 (0)
│ │ │ │ +44413   GID Size            04 (4)
│ │ │ │ +44414   GID                 00000000 (0)
│ │ │ │ +44418 PAYLOAD
│ │ │ │ +
│ │ │ │ +44EE7 LOCAL HEADER #33      04034B50 (67324752)
│ │ │ │ +44EEB Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +44EEC Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +44EED General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +44EEF Compression Method    0008 (8) 'Deflated'
│ │ │ │ +44EF1 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +44EF5 CRC                   8B6CCC23 (2339163171)
│ │ │ │ +44EF9 Compressed Size       00000C53 (3155)
│ │ │ │ +44EFD Uncompressed Size     00002742 (10050)
│ │ │ │ +44F01 Filename Length       0013 (19)
│ │ │ │ +44F03 Extra Length          001C (28)
│ │ │ │ +44F05 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x44F05: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +44F18 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +44F1A   Length              0009 (9)
│ │ │ │ +44F1C   Flags               03 (3) 'Modification Access'
│ │ │ │ +44F1D   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +44F21   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +44F25 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +44F27   Length              000B (11)
│ │ │ │ +44F29   Version             01 (1)
│ │ │ │ +44F2A   UID Size            04 (4)
│ │ │ │ +44F2B   UID                 00000000 (0)
│ │ │ │ +44F2F   GID Size            04 (4)
│ │ │ │ +44F30   GID                 00000000 (0)
│ │ │ │ +44F34 PAYLOAD
│ │ │ │ +
│ │ │ │ +45B87 LOCAL HEADER #34      04034B50 (67324752)
│ │ │ │ +45B8B Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +45B8C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +45B8D General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +45B8F Compression Method    0008 (8) 'Deflated'
│ │ │ │ +45B91 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +45B95 CRC                   75D0E296 (1976623766)
│ │ │ │ +45B99 Compressed Size       00000C92 (3218)
│ │ │ │ +45B9D Uncompressed Size     00003D11 (15633)
│ │ │ │ +45BA1 Filename Length       0014 (20)
│ │ │ │ +45BA3 Extra Length          001C (28)
│ │ │ │ +45BA5 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x45BA5: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +45BB9 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +45BBB   Length              0009 (9)
│ │ │ │ +45BBD   Flags               03 (3) 'Modification Access'
│ │ │ │ +45BBE   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +45BC2   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +45BC6 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +45BC8   Length              000B (11)
│ │ │ │ +45BCA   Version             01 (1)
│ │ │ │ +45BCB   UID Size            04 (4)
│ │ │ │ +45BCC   UID                 00000000 (0)
│ │ │ │ +45BD0   GID Size            04 (4)
│ │ │ │ +45BD1   GID                 00000000 (0)
│ │ │ │ +45BD5 PAYLOAD
│ │ │ │ +
│ │ │ │ +46867 LOCAL HEADER #35      04034B50 (67324752)
│ │ │ │ +4686B Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +4686C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +4686D General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +4686F Compression Method    0008 (8) 'Deflated'
│ │ │ │ +46871 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +46875 CRC                   C3A581AC (3282403756)
│ │ │ │ +46879 Compressed Size       00000F45 (3909)
│ │ │ │ +4687D Uncompressed Size     00003744 (14148)
│ │ │ │ +46881 Filename Length       000F (15)
│ │ │ │ +46883 Extra Length          001C (28)
│ │ │ │ +46885 Filename              'XXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x46885: Filename 'XXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +46894 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +46896   Length              0009 (9)
│ │ │ │ +46898   Flags               03 (3) 'Modification Access'
│ │ │ │ +46899   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +4689D   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +468A1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +468A3   Length              000B (11)
│ │ │ │ +468A5   Version             01 (1)
│ │ │ │ +468A6   UID Size            04 (4)
│ │ │ │ +468A7   UID                 00000000 (0)
│ │ │ │ +468AB   GID Size            04 (4)
│ │ │ │ +468AC   GID                 00000000 (0)
│ │ │ │ +468B0 PAYLOAD
│ │ │ │ +
│ │ │ │ +477F5 LOCAL HEADER #36      04034B50 (67324752)
│ │ │ │ +477F9 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +477FA Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +477FB General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +477FD Compression Method    0008 (8) 'Deflated'
│ │ │ │ +477FF Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +47803 CRC                   AD08D6E7 (2903037671)
│ │ │ │ +47807 Compressed Size       000006CE (1742)
│ │ │ │ +4780B Uncompressed Size     00001AC4 (6852)
│ │ │ │ +4780F Filename Length       000F (15)
│ │ │ │ +47811 Extra Length          001C (28)
│ │ │ │ +47813 Filename              'XXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x47813: Filename 'XXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +47822 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +47824   Length              0009 (9)
│ │ │ │ +47826   Flags               03 (3) 'Modification Access'
│ │ │ │ +47827   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +4782B   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +4782F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +47831   Length              000B (11)
│ │ │ │ +47833   Version             01 (1)
│ │ │ │ +47834   UID Size            04 (4)
│ │ │ │ +47835   UID                 00000000 (0)
│ │ │ │ +47839   GID Size            04 (4)
│ │ │ │ +4783A   GID                 00000000 (0)
│ │ │ │ +4783E PAYLOAD
│ │ │ │ +
│ │ │ │ +47F0C LOCAL HEADER #37      04034B50 (67324752)
│ │ │ │ +47F10 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +47F11 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +47F12 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +47F14 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +47F16 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +47F1A CRC                   5583AB14 (1434692372)
│ │ │ │ +47F1E Compressed Size       00001A52 (6738)
│ │ │ │ +47F22 Uncompressed Size     0000650E (25870)
│ │ │ │ +47F26 Filename Length       0013 (19)
│ │ │ │ +47F28 Extra Length          001C (28)
│ │ │ │ +47F2A Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x47F2A: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +47F3D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +47F3F   Length              0009 (9)
│ │ │ │ +47F41   Flags               03 (3) 'Modification Access'
│ │ │ │ +47F42   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +47F46   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +47F4A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +47F4C   Length              000B (11)
│ │ │ │ +47F4E   Version             01 (1)
│ │ │ │ +47F4F   UID Size            04 (4)
│ │ │ │ +47F50   UID                 00000000 (0)
│ │ │ │ +47F54   GID Size            04 (4)
│ │ │ │ +47F55   GID                 00000000 (0)
│ │ │ │ +47F59 PAYLOAD
│ │ │ │ +
│ │ │ │ +499AB LOCAL HEADER #38      04034B50 (67324752)
│ │ │ │ +499AF Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +499B0 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +499B1 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +499B3 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +499B5 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +499B9 CRC                   90967BFA (2425781242)
│ │ │ │ +499BD Compressed Size       000009A6 (2470)
│ │ │ │ +499C1 Uncompressed Size     00001B6A (7018)
│ │ │ │ +499C5 Filename Length       0010 (16)
│ │ │ │ +499C7 Extra Length          001C (28)
│ │ │ │ +499C9 Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x499C9: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +499D9 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +499DB   Length              0009 (9)
│ │ │ │ +499DD   Flags               03 (3) 'Modification Access'
│ │ │ │ +499DE   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +499E2   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +499E6 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +499E8   Length              000B (11)
│ │ │ │ +499EA   Version             01 (1)
│ │ │ │ +499EB   UID Size            04 (4)
│ │ │ │ +499EC   UID                 00000000 (0)
│ │ │ │ +499F0   GID Size            04 (4)
│ │ │ │ +499F1   GID                 00000000 (0)
│ │ │ │ +499F5 PAYLOAD
│ │ │ │ +
│ │ │ │ +4A39B LOCAL HEADER #39      04034B50 (67324752)
│ │ │ │ +4A39F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +4A3A0 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +4A3A1 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +4A3A3 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +4A3A5 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +4A3A9 CRC                   D37ED789 (3548305289)
│ │ │ │ +4A3AD Compressed Size       000006B6 (1718)
│ │ │ │ +4A3B1 Uncompressed Size     00001565 (5477)
│ │ │ │ +4A3B5 Filename Length       0012 (18)
│ │ │ │ +4A3B7 Extra Length          001C (28)
│ │ │ │ +4A3B9 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x4A3B9: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +4A3CB Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +4A3CD   Length              0009 (9)
│ │ │ │ +4A3CF   Flags               03 (3) 'Modification Access'
│ │ │ │ +4A3D0   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +4A3D4   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +4A3D8 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +4A3DA   Length              000B (11)
│ │ │ │ +4A3DC   Version             01 (1)
│ │ │ │ +4A3DD   UID Size            04 (4)
│ │ │ │ +4A3DE   UID                 00000000 (0)
│ │ │ │ +4A3E2   GID Size            04 (4)
│ │ │ │ +4A3E3   GID                 00000000 (0)
│ │ │ │ +4A3E7 PAYLOAD
│ │ │ │ +
│ │ │ │ +4AA9D LOCAL HEADER #40      04034B50 (67324752)
│ │ │ │ +4AAA1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +4AAA2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +4AAA3 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +4AAA5 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +4AAA7 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +4AAAB CRC                   F24D9270 (4065170032)
│ │ │ │ +4AAAF Compressed Size       00002D56 (11606)
│ │ │ │ +4AAB3 Uncompressed Size     0000D083 (53379)
│ │ │ │ +4AAB7 Filename Length       0010 (16)
│ │ │ │ +4AAB9 Extra Length          001C (28)
│ │ │ │ +4AABB Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x4AABB: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +4AACB Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +4AACD   Length              0009 (9)
│ │ │ │ +4AACF   Flags               03 (3) 'Modification Access'
│ │ │ │ +4AAD0   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +4AAD4   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +4AAD8 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +4AADA   Length              000B (11)
│ │ │ │ +4AADC   Version             01 (1)
│ │ │ │ +4AADD   UID Size            04 (4)
│ │ │ │ +4AADE   UID                 00000000 (0)
│ │ │ │ +4AAE2   GID Size            04 (4)
│ │ │ │ +4AAE3   GID                 00000000 (0)
│ │ │ │ +4AAE7 PAYLOAD
│ │ │ │ +
│ │ │ │ +4D83D LOCAL HEADER #41      04034B50 (67324752)
│ │ │ │ +4D841 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +4D842 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +4D843 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +4D845 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +4D847 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +4D84B CRC                   6DD28D49 (1842515273)
│ │ │ │ +4D84F Compressed Size       00001E7F (7807)
│ │ │ │ +4D853 Uncompressed Size     00009AAA (39594)
│ │ │ │ +4D857 Filename Length       0012 (18)
│ │ │ │ +4D859 Extra Length          001C (28)
│ │ │ │ +4D85B Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x4D85B: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +4D86D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +4D86F   Length              0009 (9)
│ │ │ │ +4D871   Flags               03 (3) 'Modification Access'
│ │ │ │ +4D872   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +4D876   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +4D87A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +4D87C   Length              000B (11)
│ │ │ │ +4D87E   Version             01 (1)
│ │ │ │ +4D87F   UID Size            04 (4)
│ │ │ │ +4D880   UID                 00000000 (0)
│ │ │ │ +4D884   GID Size            04 (4)
│ │ │ │ +4D885   GID                 00000000 (0)
│ │ │ │ +4D889 PAYLOAD
│ │ │ │ +
│ │ │ │ +4F708 LOCAL HEADER #42      04034B50 (67324752)
│ │ │ │ +4F70C Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +4F70D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +4F70E General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +4F710 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +4F712 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +4F716 CRC                   68D3A344 (1758700356)
│ │ │ │ +4F71A Compressed Size       00001478 (5240)
│ │ │ │ +4F71E Uncompressed Size     00007AD0 (31440)
│ │ │ │ +4F722 Filename Length       0018 (24)
│ │ │ │ +4F724 Extra Length          001C (28)
│ │ │ │ +4F726 Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x4F726: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +4F73E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +4F740   Length              0009 (9)
│ │ │ │ +4F742   Flags               03 (3) 'Modification Access'
│ │ │ │ +4F743   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +4F747   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +4F74B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +4F74D   Length              000B (11)
│ │ │ │ +4F74F   Version             01 (1)
│ │ │ │ +4F750   UID Size            04 (4)
│ │ │ │ +4F751   UID                 00000000 (0)
│ │ │ │ +4F755   GID Size            04 (4)
│ │ │ │ +4F756   GID                 00000000 (0)
│ │ │ │ +4F75A PAYLOAD
│ │ │ │ +
│ │ │ │ +50BD2 LOCAL HEADER #43      04034B50 (67324752)
│ │ │ │ +50BD6 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +50BD7 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +50BD8 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +50BDA Compression Method    0008 (8) 'Deflated'
│ │ │ │ +50BDC Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +50BE0 CRC                   BE84805E (3196354654)
│ │ │ │ +50BE4 Compressed Size       000021E3 (8675)
│ │ │ │ +50BE8 Uncompressed Size     0000D21D (53789)
│ │ │ │ +50BEC Filename Length       001F (31)
│ │ │ │ +50BEE Extra Length          001C (28)
│ │ │ │ +50BF0 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x50BF0: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +50C0F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +50C11   Length              0009 (9)
│ │ │ │ +50C13   Flags               03 (3) 'Modification Access'
│ │ │ │ +50C14   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +50C18   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +50C1C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +50C1E   Length              000B (11)
│ │ │ │ +50C20   Version             01 (1)
│ │ │ │ +50C21   UID Size            04 (4)
│ │ │ │ +50C22   UID                 00000000 (0)
│ │ │ │ +50C26   GID Size            04 (4)
│ │ │ │ +50C27   GID                 00000000 (0)
│ │ │ │ +50C2B PAYLOAD
│ │ │ │ +
│ │ │ │ +52E0E LOCAL HEADER #44      04034B50 (67324752)
│ │ │ │ +52E12 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +52E13 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +52E14 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +52E16 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +52E18 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +52E1C CRC                   585AC976 (1482344822)
│ │ │ │ +52E20 Compressed Size       000003F7 (1015)
│ │ │ │ +52E24 Uncompressed Size     000008A3 (2211)
│ │ │ │ +52E28 Filename Length       001E (30)
│ │ │ │ +52E2A Extra Length          001C (28)
│ │ │ │ +52E2C Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x52E2C: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +52E4A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +52E4C   Length              0009 (9)
│ │ │ │ +52E4E   Flags               03 (3) 'Modification Access'
│ │ │ │ +52E4F   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +52E53   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +52E57 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +52E59   Length              000B (11)
│ │ │ │ +52E5B   Version             01 (1)
│ │ │ │ +52E5C   UID Size            04 (4)
│ │ │ │ +52E5D   UID                 00000000 (0)
│ │ │ │ +52E61   GID Size            04 (4)
│ │ │ │ +52E62   GID                 00000000 (0)
│ │ │ │ +52E66 PAYLOAD
│ │ │ │ +
│ │ │ │ +5325D LOCAL HEADER #45      04034B50 (67324752)
│ │ │ │ +53261 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +53262 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +53263 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +53265 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +53267 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +5326B CRC                   16308EDA (372281050)
│ │ │ │ +5326F Compressed Size       00004361 (17249)
│ │ │ │ +53273 Uncompressed Size     0000E06F (57455)
│ │ │ │ +53277 Filename Length       0013 (19)
│ │ │ │ +53279 Extra Length          001C (28)
│ │ │ │ +5327B Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x5327B: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +5328E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +53290   Length              0009 (9)
│ │ │ │ +53292   Flags               03 (3) 'Modification Access'
│ │ │ │ +53293   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +53297   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +5329B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +5329D   Length              000B (11)
│ │ │ │ +5329F   Version             01 (1)
│ │ │ │ +532A0   UID Size            04 (4)
│ │ │ │ +532A1   UID                 00000000 (0)
│ │ │ │ +532A5   GID Size            04 (4)
│ │ │ │ +532A6   GID                 00000000 (0)
│ │ │ │ +532AA PAYLOAD
│ │ │ │ +
│ │ │ │ +5760B LOCAL HEADER #46      04034B50 (67324752)
│ │ │ │ +5760F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +57610 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +57611 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +57613 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +57615 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +57619 CRC                   4B98C7C0 (1268303808)
│ │ │ │ +5761D Compressed Size       000026C3 (9923)
│ │ │ │ +57621 Uncompressed Size     00006E45 (28229)
│ │ │ │ +57625 Filename Length       0019 (25)
│ │ │ │ +57627 Extra Length          001C (28)
│ │ │ │ +57629 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x57629: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +57642 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +57644   Length              0009 (9)
│ │ │ │ +57646   Flags               03 (3) 'Modification Access'
│ │ │ │ +57647   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +5764B   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +5764F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +57651   Length              000B (11)
│ │ │ │ +57653   Version             01 (1)
│ │ │ │ +57654   UID Size            04 (4)
│ │ │ │ +57655   UID                 00000000 (0)
│ │ │ │ +57659   GID Size            04 (4)
│ │ │ │ +5765A   GID                 00000000 (0)
│ │ │ │ +5765E PAYLOAD
│ │ │ │ +
│ │ │ │ +59D21 LOCAL HEADER #47      04034B50 (67324752)
│ │ │ │ +59D25 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +59D26 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +59D27 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +59D29 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +59D2B Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +59D2F CRC                   F8618863 (4167141475)
│ │ │ │ +59D33 Compressed Size       00002738 (10040)
│ │ │ │ +59D37 Uncompressed Size     00008B83 (35715)
│ │ │ │ +59D3B Filename Length       0019 (25)
│ │ │ │ +59D3D Extra Length          001C (28)
│ │ │ │ +59D3F Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x59D3F: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +59D58 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +59D5A   Length              0009 (9)
│ │ │ │ +59D5C   Flags               03 (3) 'Modification Access'
│ │ │ │ +59D5D   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +59D61   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +59D65 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +59D67   Length              000B (11)
│ │ │ │ +59D69   Version             01 (1)
│ │ │ │ +59D6A   UID Size            04 (4)
│ │ │ │ +59D6B   UID                 00000000 (0)
│ │ │ │ +59D6F   GID Size            04 (4)
│ │ │ │ +59D70   GID                 00000000 (0)
│ │ │ │ +59D74 PAYLOAD
│ │ │ │ +
│ │ │ │ +5C4AC LOCAL HEADER #48      04034B50 (67324752)
│ │ │ │ +5C4B0 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +5C4B1 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +5C4B2 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +5C4B4 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +5C4B6 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +5C4BA CRC                   19093DDC (420036060)
│ │ │ │ +5C4BE Compressed Size       00000ECC (3788)
│ │ │ │ +5C4C2 Uncompressed Size     000053BF (21439)
│ │ │ │ +5C4C6 Filename Length       0021 (33)
│ │ │ │ +5C4C8 Extra Length          001C (28)
│ │ │ │ +5C4CA Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x5C4CA: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +5C4EB Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +5C4ED   Length              0009 (9)
│ │ │ │ +5C4EF   Flags               03 (3) 'Modification Access'
│ │ │ │ +5C4F0   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +5C4F4   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +5C4F8 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +5C4FA   Length              000B (11)
│ │ │ │ +5C4FC   Version             01 (1)
│ │ │ │ +5C4FD   UID Size            04 (4)
│ │ │ │ +5C4FE   UID                 00000000 (0)
│ │ │ │ +5C502   GID Size            04 (4)
│ │ │ │ +5C503   GID                 00000000 (0)
│ │ │ │ +5C507 PAYLOAD
│ │ │ │ +
│ │ │ │ +5D3D3 LOCAL HEADER #49      04034B50 (67324752)
│ │ │ │ +5D3D7 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +5D3D8 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +5D3D9 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +5D3DB Compression Method    0008 (8) 'Deflated'
│ │ │ │ +5D3DD Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +5D3E1 CRC                   D1EC3113 (3521917203)
│ │ │ │ +5D3E5 Compressed Size       00000535 (1333)
│ │ │ │ +5D3E9 Uncompressed Size     00000C96 (3222)
│ │ │ │ +5D3ED Filename Length       0017 (23)
│ │ │ │ +5D3EF Extra Length          001C (28)
│ │ │ │ +5D3F1 Filename              'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x5D3F1: Filename 'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +5D408 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +5D40A   Length              0009 (9)
│ │ │ │ +5D40C   Flags               03 (3) 'Modification Access'
│ │ │ │ +5D40D   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +5D411   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +5D415 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +5D417   Length              000B (11)
│ │ │ │ +5D419   Version             01 (1)
│ │ │ │ +5D41A   UID Size            04 (4)
│ │ │ │ +5D41B   UID                 00000000 (0)
│ │ │ │ +5D41F   GID Size            04 (4)
│ │ │ │ +5D420   GID                 00000000 (0)
│ │ │ │ +5D424 PAYLOAD
│ │ │ │ +
│ │ │ │ +5D959 LOCAL HEADER #50      04034B50 (67324752)
│ │ │ │ +5D95D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +5D95E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +5D95F General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +5D961 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +5D963 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +5D967 CRC                   9ED6F2D9 (2664887001)
│ │ │ │ +5D96B Compressed Size       00000467 (1127)
│ │ │ │ +5D96F Uncompressed Size     00000931 (2353)
│ │ │ │ +5D973 Filename Length       001B (27)
│ │ │ │ +5D975 Extra Length          001C (28)
│ │ │ │ +5D977 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x5D977: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +5D992 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +5D994   Length              0009 (9)
│ │ │ │ +5D996   Flags               03 (3) 'Modification Access'
│ │ │ │ +5D997   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +5D99B   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +5D99F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +5D9A1   Length              000B (11)
│ │ │ │ +5D9A3   Version             01 (1)
│ │ │ │ +5D9A4   UID Size            04 (4)
│ │ │ │ +5D9A5   UID                 00000000 (0)
│ │ │ │ +5D9A9   GID Size            04 (4)
│ │ │ │ +5D9AA   GID                 00000000 (0)
│ │ │ │ +5D9AE PAYLOAD
│ │ │ │ +
│ │ │ │ +5DE15 LOCAL HEADER #51      04034B50 (67324752)
│ │ │ │ +5DE19 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +5DE1A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +5DE1B General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +5DE1D Compression Method    0008 (8) 'Deflated'
│ │ │ │ +5DE1F Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +5DE23 CRC                   2606F569 (637990249)
│ │ │ │ +5DE27 Compressed Size       000016F6 (5878)
│ │ │ │ +5DE2B Uncompressed Size     00007A86 (31366)
│ │ │ │ +5DE2F Filename Length       001F (31)
│ │ │ │ +5DE31 Extra Length          001C (28)
│ │ │ │ +5DE33 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x5DE33: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +5DE52 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +5DE54   Length              0009 (9)
│ │ │ │ +5DE56   Flags               03 (3) 'Modification Access'
│ │ │ │ +5DE57   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +5DE5B   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +5DE5F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +5DE61   Length              000B (11)
│ │ │ │ +5DE63   Version             01 (1)
│ │ │ │ +5DE64   UID Size            04 (4)
│ │ │ │ +5DE65   UID                 00000000 (0)
│ │ │ │ +5DE69   GID Size            04 (4)
│ │ │ │ +5DE6A   GID                 00000000 (0)
│ │ │ │ +5DE6E PAYLOAD
│ │ │ │ +
│ │ │ │ +5F564 LOCAL HEADER #52      04034B50 (67324752)
│ │ │ │ +5F568 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +5F569 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +5F56A General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +5F56C Compression Method    0008 (8) 'Deflated'
│ │ │ │ +5F56E Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +5F572 CRC                   758BB33D (1972089661)
│ │ │ │ +5F576 Compressed Size       00004168 (16744)
│ │ │ │ +5F57A Uncompressed Size     0001D163 (119139)
│ │ │ │ +5F57E Filename Length       0010 (16)
│ │ │ │ +5F580 Extra Length          001C (28)
│ │ │ │ +5F582 Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x5F582: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +5F592 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +5F594   Length              0009 (9)
│ │ │ │ +5F596   Flags               03 (3) 'Modification Access'
│ │ │ │ +5F597   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +5F59B   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +5F59F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +5F5A1   Length              000B (11)
│ │ │ │ +5F5A3   Version             01 (1)
│ │ │ │ +5F5A4   UID Size            04 (4)
│ │ │ │ +5F5A5   UID                 00000000 (0)
│ │ │ │ +5F5A9   GID Size            04 (4)
│ │ │ │ +5F5AA   GID                 00000000 (0)
│ │ │ │ +5F5AE PAYLOAD
│ │ │ │ +
│ │ │ │ +63716 LOCAL HEADER #53      04034B50 (67324752)
│ │ │ │ +6371A Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +6371B Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +6371C General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +6371E Compression Method    0008 (8) 'Deflated'
│ │ │ │ +63720 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +63724 CRC                   C55EF92D (3311335725)
│ │ │ │ +63728 Compressed Size       00000AE8 (2792)
│ │ │ │ +6372C Uncompressed Size     000021E8 (8680)
│ │ │ │ +63730 Filename Length       0014 (20)
│ │ │ │ +63732 Extra Length          001C (28)
│ │ │ │ +63734 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x63734: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +63748 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +6374A   Length              0009 (9)
│ │ │ │ +6374C   Flags               03 (3) 'Modification Access'
│ │ │ │ +6374D   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +63751   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +63755 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +63757   Length              000B (11)
│ │ │ │ +63759   Version             01 (1)
│ │ │ │ +6375A   UID Size            04 (4)
│ │ │ │ +6375B   UID                 00000000 (0)
│ │ │ │ +6375F   GID Size            04 (4)
│ │ │ │ +63760   GID                 00000000 (0)
│ │ │ │ +63764 PAYLOAD
│ │ │ │ +
│ │ │ │ +6424C LOCAL HEADER #54      04034B50 (67324752)
│ │ │ │ +64250 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +64251 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +64252 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +64254 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +64256 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +6425A CRC                   32543857 (844380247)
│ │ │ │ +6425E Compressed Size       0000B523 (46371)
│ │ │ │ +64262 Uncompressed Size     00041755 (268117)
│ │ │ │ +64266 Filename Length       0017 (23)
│ │ │ │ +64268 Extra Length          001C (28)
│ │ │ │ +6426A Filename              'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x6426A: Filename 'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +64281 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +64283   Length              0009 (9)
│ │ │ │ +64285   Flags               03 (3) 'Modification Access'
│ │ │ │ +64286   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +6428A   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +6428E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +64290   Length              000B (11)
│ │ │ │ +64292   Version             01 (1)
│ │ │ │ +64293   UID Size            04 (4)
│ │ │ │ +64294   UID                 00000000 (0)
│ │ │ │ +64298   GID Size            04 (4)
│ │ │ │ +64299   GID                 00000000 (0)
│ │ │ │ +6429D PAYLOAD
│ │ │ │ +
│ │ │ │ +6F7C0 LOCAL HEADER #55      04034B50 (67324752)
│ │ │ │ +6F7C4 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +6F7C5 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +6F7C6 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +6F7C8 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +6F7CA Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +6F7CE CRC                   564036C9 (1447048905)
│ │ │ │ +6F7D2 Compressed Size       00000400 (1024)
│ │ │ │ +6F7D6 Uncompressed Size     0000093D (2365)
│ │ │ │ +6F7DA Filename Length       0013 (19)
│ │ │ │ +6F7DC Extra Length          001C (28)
│ │ │ │ +6F7DE Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x6F7DE: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +6F7F1 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +6F7F3   Length              0009 (9)
│ │ │ │ +6F7F5   Flags               03 (3) 'Modification Access'
│ │ │ │ +6F7F6   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +6F7FA   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +6F7FE Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +6F800   Length              000B (11)
│ │ │ │ +6F802   Version             01 (1)
│ │ │ │ +6F803   UID Size            04 (4)
│ │ │ │ +6F804   UID                 00000000 (0)
│ │ │ │ +6F808   GID Size            04 (4)
│ │ │ │ +6F809   GID                 00000000 (0)
│ │ │ │ +6F80D PAYLOAD
│ │ │ │ +
│ │ │ │ +6FC0D LOCAL HEADER #56      04034B50 (67324752)
│ │ │ │ +6FC11 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +6FC12 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +6FC13 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +6FC15 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +6FC17 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +6FC1B CRC                   4AD4846E (1255441518)
│ │ │ │ +6FC1F Compressed Size       000014D9 (5337)
│ │ │ │ +6FC23 Uncompressed Size     00006892 (26770)
│ │ │ │ +6FC27 Filename Length       0012 (18)
│ │ │ │ +6FC29 Extra Length          001C (28)
│ │ │ │ +6FC2B Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x6FC2B: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +6FC3D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +6FC3F   Length              0009 (9)
│ │ │ │ +6FC41   Flags               03 (3) 'Modification Access'
│ │ │ │ +6FC42   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +6FC46   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +6FC4A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +6FC4C   Length              000B (11)
│ │ │ │ +6FC4E   Version             01 (1)
│ │ │ │ +6FC4F   UID Size            04 (4)
│ │ │ │ +6FC50   UID                 00000000 (0)
│ │ │ │ +6FC54   GID Size            04 (4)
│ │ │ │ +6FC55   GID                 00000000 (0)
│ │ │ │ +6FC59 PAYLOAD
│ │ │ │ +
│ │ │ │ +71132 LOCAL HEADER #57      04034B50 (67324752)
│ │ │ │ +71136 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +71137 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +71138 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +7113A Compression Method    0008 (8) 'Deflated'
│ │ │ │ +7113C Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +71140 CRC                   AB6E6BBC (2876140476)
│ │ │ │ +71144 Compressed Size       00001205 (4613)
│ │ │ │ +71148 Uncompressed Size     0000414F (16719)
│ │ │ │ +7114C Filename Length       0012 (18)
│ │ │ │ +7114E Extra Length          001C (28)
│ │ │ │ +71150 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x71150: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +71162 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +71164   Length              0009 (9)
│ │ │ │ +71166   Flags               03 (3) 'Modification Access'
│ │ │ │ +71167   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +7116B   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +7116F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +71171   Length              000B (11)
│ │ │ │ +71173   Version             01 (1)
│ │ │ │ +71174   UID Size            04 (4)
│ │ │ │ +71175   UID                 00000000 (0)
│ │ │ │ +71179   GID Size            04 (4)
│ │ │ │ +7117A   GID                 00000000 (0)
│ │ │ │ +7117E PAYLOAD
│ │ │ │ +
│ │ │ │ +72383 LOCAL HEADER #58      04034B50 (67324752)
│ │ │ │ +72387 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +72388 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +72389 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +7238B Compression Method    0008 (8) 'Deflated'
│ │ │ │ +7238D Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +72391 CRC                   5C8A4BDC (1552567260)
│ │ │ │ +72395 Compressed Size       00000704 (1796)
│ │ │ │ +72399 Uncompressed Size     000011A7 (4519)
│ │ │ │ +7239D Filename Length       0019 (25)
│ │ │ │ +7239F Extra Length          001C (28)
│ │ │ │ +723A1 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x723A1: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +723BA Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +723BC   Length              0009 (9)
│ │ │ │ +723BE   Flags               03 (3) 'Modification Access'
│ │ │ │ +723BF   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +723C3   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +723C7 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +723C9   Length              000B (11)
│ │ │ │ +723CB   Version             01 (1)
│ │ │ │ +723CC   UID Size            04 (4)
│ │ │ │ +723CD   UID                 00000000 (0)
│ │ │ │ +723D1   GID Size            04 (4)
│ │ │ │ +723D2   GID                 00000000 (0)
│ │ │ │ +723D6 PAYLOAD
│ │ │ │ +
│ │ │ │ +72ADA LOCAL HEADER #59      04034B50 (67324752)
│ │ │ │ +72ADE Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +72ADF Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +72AE0 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +72AE2 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +72AE4 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +72AE8 CRC                   3381C721 (864143137)
│ │ │ │ +72AEC Compressed Size       000018B5 (6325)
│ │ │ │ +72AF0 Uncompressed Size     0000A678 (42616)
│ │ │ │ +72AF4 Filename Length       0019 (25)
│ │ │ │ +72AF6 Extra Length          001C (28)
│ │ │ │ +72AF8 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x72AF8: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +72B11 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +72B13   Length              0009 (9)
│ │ │ │ +72B15   Flags               03 (3) 'Modification Access'
│ │ │ │ +72B16   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +72B1A   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +72B1E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +72B20   Length              000B (11)
│ │ │ │ +72B22   Version             01 (1)
│ │ │ │ +72B23   UID Size            04 (4)
│ │ │ │ +72B24   UID                 00000000 (0)
│ │ │ │ +72B28   GID Size            04 (4)
│ │ │ │ +72B29   GID                 00000000 (0)
│ │ │ │ +72B2D PAYLOAD
│ │ │ │ +
│ │ │ │ +743E2 LOCAL HEADER #60      04034B50 (67324752)
│ │ │ │ +743E6 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +743E7 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +743E8 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +743EA Compression Method    0008 (8) 'Deflated'
│ │ │ │ +743EC Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +743F0 CRC                   4D1409E6 (1293158886)
│ │ │ │ +743F4 Compressed Size       0000177C (6012)
│ │ │ │ +743F8 Uncompressed Size     0000472C (18220)
│ │ │ │ +743FC Filename Length       0014 (20)
│ │ │ │ +743FE Extra Length          001C (28)
│ │ │ │ +74400 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x74400: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +74414 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +74416   Length              0009 (9)
│ │ │ │ +74418   Flags               03 (3) 'Modification Access'
│ │ │ │ +74419   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +7441D   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +74421 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +74423   Length              000B (11)
│ │ │ │ +74425   Version             01 (1)
│ │ │ │ +74426   UID Size            04 (4)
│ │ │ │ +74427   UID                 00000000 (0)
│ │ │ │ +7442B   GID Size            04 (4)
│ │ │ │ +7442C   GID                 00000000 (0)
│ │ │ │ +74430 PAYLOAD
│ │ │ │ +
│ │ │ │ +75BAC LOCAL HEADER #61      04034B50 (67324752)
│ │ │ │ +75BB0 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +75BB1 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +75BB2 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +75BB4 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +75BB6 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +75BBA CRC                   2F723DFF (796016127)
│ │ │ │ +75BBE Compressed Size       00000409 (1033)
│ │ │ │ +75BC2 Uncompressed Size     00000825 (2085)
│ │ │ │ +75BC6 Filename Length       001C (28)
│ │ │ │ +75BC8 Extra Length          001C (28)
│ │ │ │ +75BCA Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x75BCA: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +75BE6 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +75BE8   Length              0009 (9)
│ │ │ │ +75BEA   Flags               03 (3) 'Modification Access'
│ │ │ │ +75BEB   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +75BEF   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +75BF3 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +75BF5   Length              000B (11)
│ │ │ │ +75BF7   Version             01 (1)
│ │ │ │ +75BF8   UID Size            04 (4)
│ │ │ │ +75BF9   UID                 00000000 (0)
│ │ │ │ +75BFD   GID Size            04 (4)
│ │ │ │ +75BFE   GID                 00000000 (0)
│ │ │ │ +75C02 PAYLOAD
│ │ │ │ +
│ │ │ │ +7600B LOCAL HEADER #62      04034B50 (67324752)
│ │ │ │ +7600F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +76010 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +76011 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +76013 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +76015 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +76019 CRC                   AF61C4DB (2942420187)
│ │ │ │ +7601D Compressed Size       000024C3 (9411)
│ │ │ │ +76021 Uncompressed Size     0000B65D (46685)
│ │ │ │ +76025 Filename Length       001F (31)
│ │ │ │ +76027 Extra Length          001C (28)
│ │ │ │ +76029 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x76029: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +76048 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +7604A   Length              0009 (9)
│ │ │ │ +7604C   Flags               03 (3) 'Modification Access'
│ │ │ │ +7604D   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +76051   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +76055 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +76057   Length              000B (11)
│ │ │ │ +76059   Version             01 (1)
│ │ │ │ +7605A   UID Size            04 (4)
│ │ │ │ +7605B   UID                 00000000 (0)
│ │ │ │ +7605F   GID Size            04 (4)
│ │ │ │ +76060   GID                 00000000 (0)
│ │ │ │ +76064 PAYLOAD
│ │ │ │ +
│ │ │ │ +78527 LOCAL HEADER #63      04034B50 (67324752)
│ │ │ │ +7852B Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +7852C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +7852D General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +7852F Compression Method    0008 (8) 'Deflated'
│ │ │ │ +78531 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +78535 CRC                   BDFBBF8D (3187392397)
│ │ │ │ +78539 Compressed Size       00000E7A (3706)
│ │ │ │ +7853D Uncompressed Size     000052DA (21210)
│ │ │ │ +78541 Filename Length       001F (31)
│ │ │ │ +78543 Extra Length          001C (28)
│ │ │ │ +78545 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x78545: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +78564 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +78566   Length              0009 (9)
│ │ │ │ +78568   Flags               03 (3) 'Modification Access'
│ │ │ │ +78569   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +7856D   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +78571 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +78573   Length              000B (11)
│ │ │ │ +78575   Version             01 (1)
│ │ │ │ +78576   UID Size            04 (4)
│ │ │ │ +78577   UID                 00000000 (0)
│ │ │ │ +7857B   GID Size            04 (4)
│ │ │ │ +7857C   GID                 00000000 (0)
│ │ │ │ +78580 PAYLOAD
│ │ │ │ +
│ │ │ │ +793FA LOCAL HEADER #64      04034B50 (67324752)
│ │ │ │ +793FE Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +793FF Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +79400 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +79402 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +79404 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +79408 CRC                   720DE003 (1913511939)
│ │ │ │ +7940C Compressed Size       00000A45 (2629)
│ │ │ │ +79410 Uncompressed Size     0000247A (9338)
│ │ │ │ +79414 Filename Length       0013 (19)
│ │ │ │ +79416 Extra Length          001C (28)
│ │ │ │ +79418 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x79418: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +7942B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +7942D   Length              0009 (9)
│ │ │ │ +7942F   Flags               03 (3) 'Modification Access'
│ │ │ │ +79430   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +79434   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +79438 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +7943A   Length              000B (11)
│ │ │ │ +7943C   Version             01 (1)
│ │ │ │ +7943D   UID Size            04 (4)
│ │ │ │ +7943E   UID                 00000000 (0)
│ │ │ │ +79442   GID Size            04 (4)
│ │ │ │ +79443   GID                 00000000 (0)
│ │ │ │ +79447 PAYLOAD
│ │ │ │ +
│ │ │ │ +79E8C LOCAL HEADER #65      04034B50 (67324752)
│ │ │ │ +79E90 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +79E91 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +79E92 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +79E94 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +79E96 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +79E9A CRC                   2F406ADE (792750814)
│ │ │ │ +79E9E Compressed Size       0000258D (9613)
│ │ │ │ +79EA2 Uncompressed Size     0000BAA4 (47780)
│ │ │ │ +79EA6 Filename Length       0019 (25)
│ │ │ │ +79EA8 Extra Length          001C (28)
│ │ │ │ +79EAA Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x79EAA: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +79EC3 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +79EC5   Length              0009 (9)
│ │ │ │ +79EC7   Flags               03 (3) 'Modification Access'
│ │ │ │ +79EC8   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +79ECC   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +79ED0 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +79ED2   Length              000B (11)
│ │ │ │ +79ED4   Version             01 (1)
│ │ │ │ +79ED5   UID Size            04 (4)
│ │ │ │ +79ED6   UID                 00000000 (0)
│ │ │ │ +79EDA   GID Size            04 (4)
│ │ │ │ +79EDB   GID                 00000000 (0)
│ │ │ │ +79EDF PAYLOAD
│ │ │ │ +
│ │ │ │ +7C46C LOCAL HEADER #66      04034B50 (67324752)
│ │ │ │ +7C470 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +7C471 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +7C472 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +7C474 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +7C476 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +7C47A CRC                   E061E754 (3764512596)
│ │ │ │ +7C47E Compressed Size       00000EFD (3837)
│ │ │ │ +7C482 Uncompressed Size     00003A2F (14895)
│ │ │ │ +7C486 Filename Length       0024 (36)
│ │ │ │ +7C488 Extra Length          001C (28)
│ │ │ │ +7C48A Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x7C48A: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +7C4AE Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +7C4B0   Length              0009 (9)
│ │ │ │ +7C4B2   Flags               03 (3) 'Modification Access'
│ │ │ │ +7C4B3   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +7C4B7   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +7C4BB Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +7C4BD   Length              000B (11)
│ │ │ │ +7C4BF   Version             01 (1)
│ │ │ │ +7C4C0   UID Size            04 (4)
│ │ │ │ +7C4C1   UID                 00000000 (0)
│ │ │ │ +7C4C5   GID Size            04 (4)
│ │ │ │ +7C4C6   GID                 00000000 (0)
│ │ │ │ +7C4CA PAYLOAD
│ │ │ │ +
│ │ │ │ +7D3C7 LOCAL HEADER #67      04034B50 (67324752)
│ │ │ │ +7D3CB Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +7D3CC Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +7D3CD General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +7D3CF Compression Method    0008 (8) 'Deflated'
│ │ │ │ +7D3D1 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +7D3D5 CRC                   EC4F7E41 (3964632641)
│ │ │ │ +7D3D9 Compressed Size       00001AE9 (6889)
│ │ │ │ +7D3DD Uncompressed Size     00005F7F (24447)
│ │ │ │ +7D3E1 Filename Length       0017 (23)
│ │ │ │ +7D3E3 Extra Length          001C (28)
│ │ │ │ +7D3E5 Filename              'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x7D3E5: Filename 'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +7D3FC Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +7D3FE   Length              0009 (9)
│ │ │ │ +7D400   Flags               03 (3) 'Modification Access'
│ │ │ │ +7D401   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +7D405   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +7D409 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +7D40B   Length              000B (11)
│ │ │ │ +7D40D   Version             01 (1)
│ │ │ │ +7D40E   UID Size            04 (4)
│ │ │ │ +7D40F   UID                 00000000 (0)
│ │ │ │ +7D413   GID Size            04 (4)
│ │ │ │ +7D414   GID                 00000000 (0)
│ │ │ │ +7D418 PAYLOAD
│ │ │ │ +
│ │ │ │ +7EF01 LOCAL HEADER #68      04034B50 (67324752)
│ │ │ │ +7EF05 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +7EF06 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +7EF07 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +7EF09 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +7EF0B Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +7EF0F CRC                   11E32AF1 (300100337)
│ │ │ │ +7EF13 Compressed Size       00000ED3 (3795)
│ │ │ │ +7EF17 Uncompressed Size     000038E2 (14562)
│ │ │ │ +7EF1B Filename Length       0023 (35)
│ │ │ │ +7EF1D Extra Length          001C (28)
│ │ │ │ +7EF1F Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x7EF1F: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +7EF42 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +7EF44   Length              0009 (9)
│ │ │ │ +7EF46   Flags               03 (3) 'Modification Access'
│ │ │ │ +7EF47   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +7EF4B   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +7EF4F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +7EF51   Length              000B (11)
│ │ │ │ +7EF53   Version             01 (1)
│ │ │ │ +7EF54   UID Size            04 (4)
│ │ │ │ +7EF55   UID                 00000000 (0)
│ │ │ │ +7EF59   GID Size            04 (4)
│ │ │ │ +7EF5A   GID                 00000000 (0)
│ │ │ │ +7EF5E PAYLOAD
│ │ │ │ +
│ │ │ │ +7FE31 LOCAL HEADER #69      04034B50 (67324752)
│ │ │ │ +7FE35 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +7FE36 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +7FE37 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +7FE39 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +7FE3B Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +7FE3F CRC                   2DB7929F (767005343)
│ │ │ │ +7FE43 Compressed Size       00000113 (275)
│ │ │ │ +7FE47 Uncompressed Size     000001F3 (499)
│ │ │ │ +7FE4B Filename Length       001B (27)
│ │ │ │ +7FE4D Extra Length          001C (28)
│ │ │ │ +7FE4F Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x7FE4F: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +7FE6A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +7FE6C   Length              0009 (9)
│ │ │ │ +7FE6E   Flags               03 (3) 'Modification Access'
│ │ │ │ +7FE6F   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +7FE73   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +7FE77 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +7FE79   Length              000B (11)
│ │ │ │ +7FE7B   Version             01 (1)
│ │ │ │ +7FE7C   UID Size            04 (4)
│ │ │ │ +7FE7D   UID                 00000000 (0)
│ │ │ │ +7FE81   GID Size            04 (4)
│ │ │ │ +7FE82   GID                 00000000 (0)
│ │ │ │ +7FE86 PAYLOAD
│ │ │ │ +
│ │ │ │ +7FF99 LOCAL HEADER #70      04034B50 (67324752)
│ │ │ │ +7FF9D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +7FF9E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +7FF9F General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +7FFA1 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +7FFA3 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +7FFA7 CRC                   CA00EBE0 (3389058016)
│ │ │ │ +7FFAB Compressed Size       0000188D (6285)
│ │ │ │ +7FFAF Uncompressed Size     00008FA8 (36776)
│ │ │ │ +7FFB3 Filename Length       001D (29)
│ │ │ │ +7FFB5 Extra Length          001C (28)
│ │ │ │ +7FFB7 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x7FFB7: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +7FFD4 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +7FFD6   Length              0009 (9)
│ │ │ │ +7FFD8   Flags               03 (3) 'Modification Access'
│ │ │ │ +7FFD9   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +7FFDD   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +7FFE1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +7FFE3   Length              000B (11)
│ │ │ │ +7FFE5   Version             01 (1)
│ │ │ │ +7FFE6   UID Size            04 (4)
│ │ │ │ +7FFE7   UID                 00000000 (0)
│ │ │ │ +7FFEB   GID Size            04 (4)
│ │ │ │ +7FFEC   GID                 00000000 (0)
│ │ │ │ +7FFF0 PAYLOAD
│ │ │ │ +
│ │ │ │ +8187D LOCAL HEADER #71      04034B50 (67324752)
│ │ │ │ +81881 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +81882 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +81883 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +81885 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +81887 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +8188B CRC                   13F8A234 (335061556)
│ │ │ │ +8188F Compressed Size       0000164C (5708)
│ │ │ │ +81893 Uncompressed Size     00003A9B (15003)
│ │ │ │ +81897 Filename Length       0015 (21)
│ │ │ │ +81899 Extra Length          001C (28)
│ │ │ │ +8189B Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x8189B: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +818B0 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +818B2   Length              0009 (9)
│ │ │ │ +818B4   Flags               03 (3) 'Modification Access'
│ │ │ │ +818B5   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +818B9   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +818BD Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +818BF   Length              000B (11)
│ │ │ │ +818C1   Version             01 (1)
│ │ │ │ +818C2   UID Size            04 (4)
│ │ │ │ +818C3   UID                 00000000 (0)
│ │ │ │ +818C7   GID Size            04 (4)
│ │ │ │ +818C8   GID                 00000000 (0)
│ │ │ │ +818CC PAYLOAD
│ │ │ │ +
│ │ │ │ +82F18 LOCAL HEADER #72      04034B50 (67324752)
│ │ │ │ +82F1C Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +82F1D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +82F1E General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +82F20 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +82F22 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +82F26 CRC                   A6BC1ACF (2797345487)
│ │ │ │ +82F2A Compressed Size       000040C8 (16584)
│ │ │ │ +82F2E Uncompressed Size     000133AC (78764)
│ │ │ │ +82F32 Filename Length       0016 (22)
│ │ │ │ +82F34 Extra Length          001C (28)
│ │ │ │ +82F36 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x82F36: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +82F4C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +82F4E   Length              0009 (9)
│ │ │ │ +82F50   Flags               03 (3) 'Modification Access'
│ │ │ │ +82F51   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +82F55   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +82F59 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +82F5B   Length              000B (11)
│ │ │ │ +82F5D   Version             01 (1)
│ │ │ │ +82F5E   UID Size            04 (4)
│ │ │ │ +82F5F   UID                 00000000 (0)
│ │ │ │ +82F63   GID Size            04 (4)
│ │ │ │ +82F64   GID                 00000000 (0)
│ │ │ │ +82F68 PAYLOAD
│ │ │ │  
│ │ │ │  87030 LOCAL HEADER #73      04034B50 (67324752)
│ │ │ │  87034 Extract Zip Spec      14 (20) '2.0'
│ │ │ │  87035 Extract OS            00 (0) 'MS-DOS'
│ │ │ │  87036 General Purpose Flag  0000 (0)
│ │ │ │        [Bits 1-2]            0 'Normal Compression'
│ │ │ │  87038 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -8703A Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -8703E CRC                   FF953A42 (4287969858)
│ │ │ │ -87042 Compressed Size       00003EB3 (16051)
│ │ │ │ +8703A Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +8703E CRC                   3D47632B (1028088619)
│ │ │ │ +87042 Compressed Size       00003EB7 (16055)
│ │ │ │  87046 Uncompressed Size     0001C78B (116619)
│ │ │ │  8704A Filename Length       0019 (25)
│ │ │ │  8704C Extra Length          001C (28)
│ │ │ │  8704E Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │  #
│ │ │ │  # WARNING: Offset 0x8704E: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │  #          Zero length filename
│ │ │ │  #
│ │ │ │  87067 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │  87069   Length              0009 (9)
│ │ │ │  8706B   Flags               03 (3) 'Modification Access'
│ │ │ │ -8706C   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -87070   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ +8706C   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +87070   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │  87074 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │  87076   Length              000B (11)
│ │ │ │  87078   Version             01 (1)
│ │ │ │  87079   UID Size            04 (4)
│ │ │ │  8707A   UID                 00000000 (0)
│ │ │ │  8707E   GID Size            04 (4)
│ │ │ │  8707F   GID                 00000000 (0)
│ │ │ │  87083 PAYLOAD
│ │ │ │  
│ │ │ │ -8AF36 LOCAL HEADER #74      04034B50 (67324752)
│ │ │ │ -8AF3A Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -8AF3B Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -8AF3C General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -8AF3E Compression Method    0008 (8) 'Deflated'
│ │ │ │ -8AF40 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -8AF44 CRC                   D20AC80F (3523921935)
│ │ │ │ -8AF48 Compressed Size       0000089D (2205)
│ │ │ │ -8AF4C Uncompressed Size     000036CC (14028)
│ │ │ │ -8AF50 Filename Length       0011 (17)
│ │ │ │ -8AF52 Extra Length          001C (28)
│ │ │ │ -8AF54 Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x8AF54: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -8AF65 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -8AF67   Length              0009 (9)
│ │ │ │ -8AF69   Flags               03 (3) 'Modification Access'
│ │ │ │ -8AF6A   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -8AF6E   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -8AF72 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -8AF74   Length              000B (11)
│ │ │ │ -8AF76   Version             01 (1)
│ │ │ │ -8AF77   UID Size            04 (4)
│ │ │ │ -8AF78   UID                 00000000 (0)
│ │ │ │ -8AF7C   GID Size            04 (4)
│ │ │ │ -8AF7D   GID                 00000000 (0)
│ │ │ │ -8AF81 PAYLOAD
│ │ │ │ -
│ │ │ │ -8B81E LOCAL HEADER #75      04034B50 (67324752)
│ │ │ │ -8B822 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -8B823 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -8B824 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -8B826 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -8B828 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -8B82C CRC                   ACBCD47B (2898056315)
│ │ │ │ -8B830 Compressed Size       0000519E (20894)
│ │ │ │ -8B834 Uncompressed Size     0001F99A (129434)
│ │ │ │ -8B838 Filename Length       0015 (21)
│ │ │ │ -8B83A Extra Length          001C (28)
│ │ │ │ -8B83C Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x8B83C: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -8B851 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -8B853   Length              0009 (9)
│ │ │ │ -8B855   Flags               03 (3) 'Modification Access'
│ │ │ │ -8B856   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -8B85A   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -8B85E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -8B860   Length              000B (11)
│ │ │ │ -8B862   Version             01 (1)
│ │ │ │ -8B863   UID Size            04 (4)
│ │ │ │ -8B864   UID                 00000000 (0)
│ │ │ │ -8B868   GID Size            04 (4)
│ │ │ │ -8B869   GID                 00000000 (0)
│ │ │ │ -8B86D PAYLOAD
│ │ │ │ -
│ │ │ │ -90A0B LOCAL HEADER #76      04034B50 (67324752)
│ │ │ │ -90A0F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -90A10 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -90A11 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -90A13 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -90A15 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -90A19 CRC                   2CBD0730 (750585648)
│ │ │ │ -90A1D Compressed Size       00001C41 (7233)
│ │ │ │ -90A21 Uncompressed Size     00008AC8 (35528)
│ │ │ │ -90A25 Filename Length       0019 (25)
│ │ │ │ -90A27 Extra Length          001C (28)
│ │ │ │ -90A29 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x90A29: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -90A42 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -90A44   Length              0009 (9)
│ │ │ │ -90A46   Flags               03 (3) 'Modification Access'
│ │ │ │ -90A47   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -90A4B   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -90A4F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -90A51   Length              000B (11)
│ │ │ │ -90A53   Version             01 (1)
│ │ │ │ -90A54   UID Size            04 (4)
│ │ │ │ -90A55   UID                 00000000 (0)
│ │ │ │ -90A59   GID Size            04 (4)
│ │ │ │ -90A5A   GID                 00000000 (0)
│ │ │ │ -90A5E PAYLOAD
│ │ │ │ -
│ │ │ │ -9269F LOCAL HEADER #77      04034B50 (67324752)
│ │ │ │ -926A3 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -926A4 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -926A5 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -926A7 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -926A9 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -926AD CRC                   896CE926 (2305616166)
│ │ │ │ -926B1 Compressed Size       00000D91 (3473)
│ │ │ │ -926B5 Uncompressed Size     00002EA4 (11940)
│ │ │ │ -926B9 Filename Length       0018 (24)
│ │ │ │ -926BB Extra Length          001C (28)
│ │ │ │ -926BD Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x926BD: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -926D5 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -926D7   Length              0009 (9)
│ │ │ │ -926D9   Flags               03 (3) 'Modification Access'
│ │ │ │ -926DA   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -926DE   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -926E2 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -926E4   Length              000B (11)
│ │ │ │ -926E6   Version             01 (1)
│ │ │ │ -926E7   UID Size            04 (4)
│ │ │ │ -926E8   UID                 00000000 (0)
│ │ │ │ -926EC   GID Size            04 (4)
│ │ │ │ -926ED   GID                 00000000 (0)
│ │ │ │ -926F1 PAYLOAD
│ │ │ │ -
│ │ │ │ -93482 LOCAL HEADER #78      04034B50 (67324752)
│ │ │ │ -93486 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -93487 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -93488 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9348A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9348C Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -93490 CRC                   535B63FB (1398498299)
│ │ │ │ -93494 Compressed Size       000001DF (479)
│ │ │ │ -93498 Uncompressed Size     00000323 (803)
│ │ │ │ -9349C Filename Length       0011 (17)
│ │ │ │ -9349E Extra Length          001C (28)
│ │ │ │ -934A0 Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x934A0: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -934B1 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -934B3   Length              0009 (9)
│ │ │ │ -934B5   Flags               03 (3) 'Modification Access'
│ │ │ │ -934B6   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -934BA   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -934BE Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -934C0   Length              000B (11)
│ │ │ │ -934C2   Version             01 (1)
│ │ │ │ -934C3   UID Size            04 (4)
│ │ │ │ -934C4   UID                 00000000 (0)
│ │ │ │ -934C8   GID Size            04 (4)
│ │ │ │ -934C9   GID                 00000000 (0)
│ │ │ │ -934CD PAYLOAD
│ │ │ │ -
│ │ │ │ -936AC LOCAL HEADER #79      04034B50 (67324752)
│ │ │ │ -936B0 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -936B1 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -936B2 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -936B4 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -936B6 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -936BA CRC                   32CAD6D8 (852154072)
│ │ │ │ -936BE Compressed Size       000006BE (1726)
│ │ │ │ -936C2 Uncompressed Size     0000141F (5151)
│ │ │ │ -936C6 Filename Length       0019 (25)
│ │ │ │ -936C8 Extra Length          001C (28)
│ │ │ │ -936CA Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x936CA: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -936E3 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -936E5   Length              0009 (9)
│ │ │ │ -936E7   Flags               03 (3) 'Modification Access'
│ │ │ │ -936E8   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -936EC   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -936F0 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -936F2   Length              000B (11)
│ │ │ │ -936F4   Version             01 (1)
│ │ │ │ -936F5   UID Size            04 (4)
│ │ │ │ -936F6   UID                 00000000 (0)
│ │ │ │ -936FA   GID Size            04 (4)
│ │ │ │ -936FB   GID                 00000000 (0)
│ │ │ │ -936FF PAYLOAD
│ │ │ │ -
│ │ │ │ -93DBD LOCAL HEADER #80      04034B50 (67324752)
│ │ │ │ -93DC1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -93DC2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -93DC3 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -93DC5 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -93DC7 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -93DCB CRC                   FC6D6CD0 (4235029712)
│ │ │ │ -93DCF Compressed Size       00001B8D (7053)
│ │ │ │ -93DD3 Uncompressed Size     00009F5F (40799)
│ │ │ │ -93DD7 Filename Length       0018 (24)
│ │ │ │ -93DD9 Extra Length          001C (28)
│ │ │ │ -93DDB Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x93DDB: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -93DF3 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -93DF5   Length              0009 (9)
│ │ │ │ -93DF7   Flags               03 (3) 'Modification Access'
│ │ │ │ -93DF8   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -93DFC   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -93E00 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -93E02   Length              000B (11)
│ │ │ │ -93E04   Version             01 (1)
│ │ │ │ -93E05   UID Size            04 (4)
│ │ │ │ -93E06   UID                 00000000 (0)
│ │ │ │ -93E0A   GID Size            04 (4)
│ │ │ │ -93E0B   GID                 00000000 (0)
│ │ │ │ -93E0F PAYLOAD
│ │ │ │ -
│ │ │ │ -9599C LOCAL HEADER #81      04034B50 (67324752)
│ │ │ │ -959A0 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -959A1 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -959A2 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -959A4 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -959A6 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -959AA CRC                   11186130 (286810416)
│ │ │ │ -959AE Compressed Size       000016FF (5887)
│ │ │ │ -959B2 Uncompressed Size     00008B12 (35602)
│ │ │ │ -959B6 Filename Length       0012 (18)
│ │ │ │ -959B8 Extra Length          001C (28)
│ │ │ │ -959BA Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x959BA: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -959CC Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -959CE   Length              0009 (9)
│ │ │ │ -959D0   Flags               03 (3) 'Modification Access'
│ │ │ │ -959D1   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -959D5   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -959D9 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -959DB   Length              000B (11)
│ │ │ │ -959DD   Version             01 (1)
│ │ │ │ -959DE   UID Size            04 (4)
│ │ │ │ -959DF   UID                 00000000 (0)
│ │ │ │ -959E3   GID Size            04 (4)
│ │ │ │ -959E4   GID                 00000000 (0)
│ │ │ │ -959E8 PAYLOAD
│ │ │ │ -
│ │ │ │ -970E7 LOCAL HEADER #82      04034B50 (67324752)
│ │ │ │ -970EB Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -970EC Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -970ED General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -970EF Compression Method    0008 (8) 'Deflated'
│ │ │ │ -970F1 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -970F5 CRC                   0D2BB7BA (220968890)
│ │ │ │ -970F9 Compressed Size       00001E0B (7691)
│ │ │ │ -970FD Uncompressed Size     00008823 (34851)
│ │ │ │ -97101 Filename Length       0016 (22)
│ │ │ │ -97103 Extra Length          001C (28)
│ │ │ │ -97105 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x97105: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9711B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9711D   Length              0009 (9)
│ │ │ │ -9711F   Flags               03 (3) 'Modification Access'
│ │ │ │ -97120   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -97124   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -97128 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9712A   Length              000B (11)
│ │ │ │ -9712C   Version             01 (1)
│ │ │ │ -9712D   UID Size            04 (4)
│ │ │ │ -9712E   UID                 00000000 (0)
│ │ │ │ -97132   GID Size            04 (4)
│ │ │ │ -97133   GID                 00000000 (0)
│ │ │ │ -97137 PAYLOAD
│ │ │ │ -
│ │ │ │ -98F42 LOCAL HEADER #83      04034B50 (67324752)
│ │ │ │ -98F46 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -98F47 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -98F48 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -98F4A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -98F4C Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -98F50 CRC                   AA93B274 (2861806196)
│ │ │ │ -98F54 Compressed Size       000029A8 (10664)
│ │ │ │ -98F58 Uncompressed Size     0000D04F (53327)
│ │ │ │ -98F5C Filename Length       001A (26)
│ │ │ │ -98F5E Extra Length          001C (28)
│ │ │ │ -98F60 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x98F60: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -98F7A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -98F7C   Length              0009 (9)
│ │ │ │ -98F7E   Flags               03 (3) 'Modification Access'
│ │ │ │ -98F7F   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -98F83   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -98F87 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -98F89   Length              000B (11)
│ │ │ │ -98F8B   Version             01 (1)
│ │ │ │ -98F8C   UID Size            04 (4)
│ │ │ │ -98F8D   UID                 00000000 (0)
│ │ │ │ -98F91   GID Size            04 (4)
│ │ │ │ -98F92   GID                 00000000 (0)
│ │ │ │ -98F96 PAYLOAD
│ │ │ │ -
│ │ │ │ -9B93E LOCAL HEADER #84      04034B50 (67324752)
│ │ │ │ -9B942 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9B943 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9B944 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9B946 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9B948 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -9B94C CRC                   C898661A (3365430810)
│ │ │ │ -9B950 Compressed Size       000009AB (2475)
│ │ │ │ -9B954 Uncompressed Size     00001DAC (7596)
│ │ │ │ -9B958 Filename Length       0018 (24)
│ │ │ │ -9B95A Extra Length          001C (28)
│ │ │ │ -9B95C Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9B95C: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9B974 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9B976   Length              0009 (9)
│ │ │ │ -9B978   Flags               03 (3) 'Modification Access'
│ │ │ │ -9B979   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -9B97D   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -9B981 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9B983   Length              000B (11)
│ │ │ │ -9B985   Version             01 (1)
│ │ │ │ -9B986   UID Size            04 (4)
│ │ │ │ -9B987   UID                 00000000 (0)
│ │ │ │ -9B98B   GID Size            04 (4)
│ │ │ │ -9B98C   GID                 00000000 (0)
│ │ │ │ -9B990 PAYLOAD
│ │ │ │ -
│ │ │ │ -9C33B LOCAL HEADER #85      04034B50 (67324752)
│ │ │ │ -9C33F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9C340 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9C341 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9C343 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9C345 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -9C349 CRC                   F0556E9A (4032130714)
│ │ │ │ -9C34D Compressed Size       000152EE (86766)
│ │ │ │ -9C351 Uncompressed Size     000159F8 (88568)
│ │ │ │ -9C355 Filename Length       001E (30)
│ │ │ │ -9C357 Extra Length          001C (28)
│ │ │ │ -9C359 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9C359: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9C377 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9C379   Length              0009 (9)
│ │ │ │ -9C37B   Flags               03 (3) 'Modification Access'
│ │ │ │ -9C37C   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -9C380   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -9C384 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9C386   Length              000B (11)
│ │ │ │ -9C388   Version             01 (1)
│ │ │ │ -9C389   UID Size            04 (4)
│ │ │ │ -9C38A   UID                 00000000 (0)
│ │ │ │ -9C38E   GID Size            04 (4)
│ │ │ │ -9C38F   GID                 00000000 (0)
│ │ │ │ -9C393 PAYLOAD
│ │ │ │ -
│ │ │ │ -B1681 LOCAL HEADER #86      04034B50 (67324752)
│ │ │ │ -B1685 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -B1686 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -B1687 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -B1689 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -B168B Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B168F CRC                   F5E2129F (4125233823)
│ │ │ │ -B1693 Compressed Size       000016BC (5820)
│ │ │ │ -B1697 Uncompressed Size     000016CD (5837)
│ │ │ │ -B169B Filename Length       0015 (21)
│ │ │ │ -B169D Extra Length          001C (28)
│ │ │ │ -B169F Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xB169F: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -B16B4 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -B16B6   Length              0009 (9)
│ │ │ │ -B16B8   Flags               03 (3) 'Modification Access'
│ │ │ │ -B16B9   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B16BD   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B16C1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -B16C3   Length              000B (11)
│ │ │ │ -B16C5   Version             01 (1)
│ │ │ │ -B16C6   UID Size            04 (4)
│ │ │ │ -B16C7   UID                 00000000 (0)
│ │ │ │ -B16CB   GID Size            04 (4)
│ │ │ │ -B16CC   GID                 00000000 (0)
│ │ │ │ -B16D0 PAYLOAD
│ │ │ │ -
│ │ │ │ -B2D8C LOCAL HEADER #87      04034B50 (67324752)
│ │ │ │ -B2D90 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -B2D91 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -B2D92 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -B2D94 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -B2D96 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B2D9A CRC                   F5E2129F (4125233823)
│ │ │ │ -B2D9E Compressed Size       000016BC (5820)
│ │ │ │ -B2DA2 Uncompressed Size     000016CD (5837)
│ │ │ │ -B2DA6 Filename Length       001C (28)
│ │ │ │ -B2DA8 Extra Length          001C (28)
│ │ │ │ -B2DAA Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xB2DAA: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -B2DC6 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -B2DC8   Length              0009 (9)
│ │ │ │ -B2DCA   Flags               03 (3) 'Modification Access'
│ │ │ │ -B2DCB   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B2DCF   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B2DD3 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -B2DD5   Length              000B (11)
│ │ │ │ -B2DD7   Version             01 (1)
│ │ │ │ -B2DD8   UID Size            04 (4)
│ │ │ │ -B2DD9   UID                 00000000 (0)
│ │ │ │ -B2DDD   GID Size            04 (4)
│ │ │ │ -B2DDE   GID                 00000000 (0)
│ │ │ │ -B2DE2 PAYLOAD
│ │ │ │ -
│ │ │ │ -B449E LOCAL HEADER #88      04034B50 (67324752)
│ │ │ │ -B44A2 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -B44A3 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -B44A4 General Purpose Flag  0000 (0)
│ │ │ │ -B44A6 Compression Method    0000 (0) 'Stored'
│ │ │ │ -B44A8 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B44AC CRC                   FC95F24B (4237685323)
│ │ │ │ -B44B0 Compressed Size       00001B84 (7044)
│ │ │ │ -B44B4 Uncompressed Size     00001B84 (7044)
│ │ │ │ -B44B8 Filename Length       0016 (22)
│ │ │ │ -B44BA Extra Length          001C (28)
│ │ │ │ -B44BC Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xB44BC: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -B44D2 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -B44D4   Length              0009 (9)
│ │ │ │ -B44D6   Flags               03 (3) 'Modification Access'
│ │ │ │ -B44D7   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B44DB   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B44DF Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -B44E1   Length              000B (11)
│ │ │ │ -B44E3   Version             01 (1)
│ │ │ │ -B44E4   UID Size            04 (4)
│ │ │ │ -B44E5   UID                 00000000 (0)
│ │ │ │ -B44E9   GID Size            04 (4)
│ │ │ │ -B44EA   GID                 00000000 (0)
│ │ │ │ -B44EE PAYLOAD
│ │ │ │ -
│ │ │ │ -B6072 LOCAL HEADER #89      04034B50 (67324752)
│ │ │ │ -B6076 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -B6077 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -B6078 General Purpose Flag  0000 (0)
│ │ │ │ -B607A Compression Method    0000 (0) 'Stored'
│ │ │ │ -B607C Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B6080 CRC                   D0D71F86 (3503759238)
│ │ │ │ -B6084 Compressed Size       00000B7B (2939)
│ │ │ │ -B6088 Uncompressed Size     00000B7B (2939)
│ │ │ │ -B608C Filename Length       0016 (22)
│ │ │ │ -B608E Extra Length          001C (28)
│ │ │ │ -B6090 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xB6090: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -B60A6 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -B60A8   Length              0009 (9)
│ │ │ │ -B60AA   Flags               03 (3) 'Modification Access'
│ │ │ │ -B60AB   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B60AF   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B60B3 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -B60B5   Length              000B (11)
│ │ │ │ -B60B7   Version             01 (1)
│ │ │ │ -B60B8   UID Size            04 (4)
│ │ │ │ -B60B9   UID                 00000000 (0)
│ │ │ │ -B60BD   GID Size            04 (4)
│ │ │ │ -B60BE   GID                 00000000 (0)
│ │ │ │ -B60C2 PAYLOAD
│ │ │ │ -
│ │ │ │ -B6C3D LOCAL HEADER #90      04034B50 (67324752)
│ │ │ │ -B6C41 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -B6C42 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -B6C43 General Purpose Flag  0000 (0)
│ │ │ │ -B6C45 Compression Method    0000 (0) 'Stored'
│ │ │ │ -B6C47 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B6C4B CRC                   FFF9C4D2 (4294558930)
│ │ │ │ -B6C4F Compressed Size       0000138F (5007)
│ │ │ │ -B6C53 Uncompressed Size     0000138F (5007)
│ │ │ │ -B6C57 Filename Length       0016 (22)
│ │ │ │ -B6C59 Extra Length          001C (28)
│ │ │ │ -B6C5B Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xB6C5B: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -B6C71 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -B6C73   Length              0009 (9)
│ │ │ │ -B6C75   Flags               03 (3) 'Modification Access'
│ │ │ │ -B6C76   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B6C7A   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B6C7E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -B6C80   Length              000B (11)
│ │ │ │ -B6C82   Version             01 (1)
│ │ │ │ -B6C83   UID Size            04 (4)
│ │ │ │ -B6C84   UID                 00000000 (0)
│ │ │ │ -B6C88   GID Size            04 (4)
│ │ │ │ -B6C89   GID                 00000000 (0)
│ │ │ │ -B6C8D PAYLOAD
│ │ │ │ -
│ │ │ │ -B801C LOCAL HEADER #91      04034B50 (67324752)
│ │ │ │ -B8020 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -B8021 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -B8022 General Purpose Flag  0000 (0)
│ │ │ │ -B8024 Compression Method    0000 (0) 'Stored'
│ │ │ │ -B8026 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B802A CRC                   A1037E8E (2701360782)
│ │ │ │ -B802E Compressed Size       0000145E (5214)
│ │ │ │ -B8032 Uncompressed Size     0000145E (5214)
│ │ │ │ -B8036 Filename Length       0016 (22)
│ │ │ │ -B8038 Extra Length          001C (28)
│ │ │ │ -B803A Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xB803A: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -B8050 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -B8052   Length              0009 (9)
│ │ │ │ -B8054   Flags               03 (3) 'Modification Access'
│ │ │ │ -B8055   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B8059   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B805D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -B805F   Length              000B (11)
│ │ │ │ -B8061   Version             01 (1)
│ │ │ │ -B8062   UID Size            04 (4)
│ │ │ │ -B8063   UID                 00000000 (0)
│ │ │ │ -B8067   GID Size            04 (4)
│ │ │ │ -B8068   GID                 00000000 (0)
│ │ │ │ -B806C PAYLOAD
│ │ │ │ -
│ │ │ │ -B94CA LOCAL HEADER #92      04034B50 (67324752)
│ │ │ │ -B94CE Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -B94CF Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -B94D0 General Purpose Flag  0000 (0)
│ │ │ │ -B94D2 Compression Method    0000 (0) 'Stored'
│ │ │ │ -B94D4 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B94D8 CRC                   5E9E64F1 (1587438833)
│ │ │ │ -B94DC Compressed Size       000008EC (2284)
│ │ │ │ -B94E0 Uncompressed Size     000008EC (2284)
│ │ │ │ -B94E4 Filename Length       0016 (22)
│ │ │ │ -B94E6 Extra Length          001C (28)
│ │ │ │ -B94E8 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xB94E8: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -B94FE Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -B9500   Length              0009 (9)
│ │ │ │ -B9502   Flags               03 (3) 'Modification Access'
│ │ │ │ -B9503   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B9507   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B950B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -B950D   Length              000B (11)
│ │ │ │ -B950F   Version             01 (1)
│ │ │ │ -B9510   UID Size            04 (4)
│ │ │ │ -B9511   UID                 00000000 (0)
│ │ │ │ -B9515   GID Size            04 (4)
│ │ │ │ -B9516   GID                 00000000 (0)
│ │ │ │ -B951A PAYLOAD
│ │ │ │ -
│ │ │ │ -B9E06 LOCAL HEADER #93      04034B50 (67324752)
│ │ │ │ -B9E0A Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -B9E0B Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -B9E0C General Purpose Flag  0000 (0)
│ │ │ │ -B9E0E Compression Method    0000 (0) 'Stored'
│ │ │ │ -B9E10 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B9E14 CRC                   42E340AB (1122189483)
│ │ │ │ -B9E18 Compressed Size       00001F2E (7982)
│ │ │ │ -B9E1C Uncompressed Size     00001F2E (7982)
│ │ │ │ -B9E20 Filename Length       001E (30)
│ │ │ │ -B9E22 Extra Length          001C (28)
│ │ │ │ -B9E24 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xB9E24: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -B9E42 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -B9E44   Length              0009 (9)
│ │ │ │ -B9E46   Flags               03 (3) 'Modification Access'
│ │ │ │ -B9E47   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B9E4B   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -B9E4F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -B9E51   Length              000B (11)
│ │ │ │ -B9E53   Version             01 (1)
│ │ │ │ -B9E54   UID Size            04 (4)
│ │ │ │ -B9E55   UID                 00000000 (0)
│ │ │ │ -B9E59   GID Size            04 (4)
│ │ │ │ -B9E5A   GID                 00000000 (0)
│ │ │ │ -B9E5E PAYLOAD
│ │ │ │ -
│ │ │ │ -BBD8C LOCAL HEADER #94      04034B50 (67324752)
│ │ │ │ -BBD90 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -BBD91 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -BBD92 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -BBD94 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -BBD96 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -BBD9A CRC                   29EA8E7B (703237755)
│ │ │ │ -BBD9E Compressed Size       00003D82 (15746)
│ │ │ │ -BBDA2 Uncompressed Size     000166B0 (91824)
│ │ │ │ -BBDA6 Filename Length       001A (26)
│ │ │ │ -BBDA8 Extra Length          001C (28)
│ │ │ │ -BBDAA Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xBBDAA: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -BBDC4 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -BBDC6   Length              0009 (9)
│ │ │ │ -BBDC8   Flags               03 (3) 'Modification Access'
│ │ │ │ -BBDC9   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -BBDCD   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -BBDD1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -BBDD3   Length              000B (11)
│ │ │ │ -BBDD5   Version             01 (1)
│ │ │ │ -BBDD6   UID Size            04 (4)
│ │ │ │ -BBDD7   UID                 00000000 (0)
│ │ │ │ -BBDDB   GID Size            04 (4)
│ │ │ │ -BBDDC   GID                 00000000 (0)
│ │ │ │ -BBDE0 PAYLOAD
│ │ │ │ -
│ │ │ │ -BFB62 LOCAL HEADER #95      04034B50 (67324752)
│ │ │ │ -BFB66 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -BFB67 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -BFB68 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -BFB6A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -BFB6C Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -BFB70 CRC                   207E153D (545133885)
│ │ │ │ -BFB74 Compressed Size       000029D2 (10706)
│ │ │ │ -BFB78 Uncompressed Size     0000BB3A (47930)
│ │ │ │ -BFB7C Filename Length       0018 (24)
│ │ │ │ -BFB7E Extra Length          001C (28)
│ │ │ │ -BFB80 Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xBFB80: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -BFB98 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -BFB9A   Length              0009 (9)
│ │ │ │ -BFB9C   Flags               03 (3) 'Modification Access'
│ │ │ │ -BFB9D   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -BFBA1   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -BFBA5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -BFBA7   Length              000B (11)
│ │ │ │ -BFBA9   Version             01 (1)
│ │ │ │ -BFBAA   UID Size            04 (4)
│ │ │ │ -BFBAB   UID                 00000000 (0)
│ │ │ │ -BFBAF   GID Size            04 (4)
│ │ │ │ -BFBB0   GID                 00000000 (0)
│ │ │ │ -BFBB4 PAYLOAD
│ │ │ │ -
│ │ │ │ -C2586 LOCAL HEADER #96      04034B50 (67324752)
│ │ │ │ -C258A Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C258B Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C258C General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C258E Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2590 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C2594 CRC                   DCB3B516 (3702764822)
│ │ │ │ -C2598 Compressed Size       000000AE (174)
│ │ │ │ -C259C Uncompressed Size     000000FC (252)
│ │ │ │ -C25A0 Filename Length       0016 (22)
│ │ │ │ -C25A2 Extra Length          001C (28)
│ │ │ │ -C25A4 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC25A4: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C25BA Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C25BC   Length              0009 (9)
│ │ │ │ -C25BE   Flags               03 (3) 'Modification Access'
│ │ │ │ -C25BF   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C25C3   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C25C7 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C25C9   Length              000B (11)
│ │ │ │ -C25CB   Version             01 (1)
│ │ │ │ -C25CC   UID Size            04 (4)
│ │ │ │ -C25CD   UID                 00000000 (0)
│ │ │ │ -C25D1   GID Size            04 (4)
│ │ │ │ -C25D2   GID                 00000000 (0)
│ │ │ │ -C25D6 PAYLOAD               XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
│ │ │ │ +8AF3A LOCAL HEADER #74      04034B50 (67324752)
│ │ │ │ +8AF3E Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +8AF3F Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +8AF40 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +8AF42 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +8AF44 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +8AF48 CRC                   339E52AB (866013867)
│ │ │ │ +8AF4C Compressed Size       000008A3 (2211)
│ │ │ │ +8AF50 Uncompressed Size     000036CC (14028)
│ │ │ │ +8AF54 Filename Length       0011 (17)
│ │ │ │ +8AF56 Extra Length          001C (28)
│ │ │ │ +8AF58 Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x8AF58: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +8AF69 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +8AF6B   Length              0009 (9)
│ │ │ │ +8AF6D   Flags               03 (3) 'Modification Access'
│ │ │ │ +8AF6E   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +8AF72   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +8AF76 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +8AF78   Length              000B (11)
│ │ │ │ +8AF7A   Version             01 (1)
│ │ │ │ +8AF7B   UID Size            04 (4)
│ │ │ │ +8AF7C   UID                 00000000 (0)
│ │ │ │ +8AF80   GID Size            04 (4)
│ │ │ │ +8AF81   GID                 00000000 (0)
│ │ │ │ +8AF85 PAYLOAD
│ │ │ │ +
│ │ │ │ +8B828 LOCAL HEADER #75      04034B50 (67324752)
│ │ │ │ +8B82C Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +8B82D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +8B82E General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +8B830 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +8B832 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +8B836 CRC                   FFBD87B5 (4290611125)
│ │ │ │ +8B83A Compressed Size       000051A3 (20899)
│ │ │ │ +8B83E Uncompressed Size     0001F99A (129434)
│ │ │ │ +8B842 Filename Length       0015 (21)
│ │ │ │ +8B844 Extra Length          001C (28)
│ │ │ │ +8B846 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x8B846: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +8B85B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +8B85D   Length              0009 (9)
│ │ │ │ +8B85F   Flags               03 (3) 'Modification Access'
│ │ │ │ +8B860   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +8B864   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +8B868 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +8B86A   Length              000B (11)
│ │ │ │ +8B86C   Version             01 (1)
│ │ │ │ +8B86D   UID Size            04 (4)
│ │ │ │ +8B86E   UID                 00000000 (0)
│ │ │ │ +8B872   GID Size            04 (4)
│ │ │ │ +8B873   GID                 00000000 (0)
│ │ │ │ +8B877 PAYLOAD
│ │ │ │ +
│ │ │ │ +90A1A LOCAL HEADER #76      04034B50 (67324752)
│ │ │ │ +90A1E Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +90A1F Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +90A20 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +90A22 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +90A24 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +90A28 CRC                   1BAA9D20 (464166176)
│ │ │ │ +90A2C Compressed Size       00001C43 (7235)
│ │ │ │ +90A30 Uncompressed Size     00008AC8 (35528)
│ │ │ │ +90A34 Filename Length       0019 (25)
│ │ │ │ +90A36 Extra Length          001C (28)
│ │ │ │ +90A38 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x90A38: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +90A51 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +90A53   Length              0009 (9)
│ │ │ │ +90A55   Flags               03 (3) 'Modification Access'
│ │ │ │ +90A56   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +90A5A   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +90A5E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +90A60   Length              000B (11)
│ │ │ │ +90A62   Version             01 (1)
│ │ │ │ +90A63   UID Size            04 (4)
│ │ │ │ +90A64   UID                 00000000 (0)
│ │ │ │ +90A68   GID Size            04 (4)
│ │ │ │ +90A69   GID                 00000000 (0)
│ │ │ │ +90A6D PAYLOAD
│ │ │ │ +
│ │ │ │ +926B0 LOCAL HEADER #77      04034B50 (67324752)
│ │ │ │ +926B4 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +926B5 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +926B6 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +926B8 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +926BA Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +926BE CRC                   FAE8837D (4209542013)
│ │ │ │ +926C2 Compressed Size       00000D92 (3474)
│ │ │ │ +926C6 Uncompressed Size     00002EA4 (11940)
│ │ │ │ +926CA Filename Length       0018 (24)
│ │ │ │ +926CC Extra Length          001C (28)
│ │ │ │ +926CE Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x926CE: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +926E6 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +926E8   Length              0009 (9)
│ │ │ │ +926EA   Flags               03 (3) 'Modification Access'
│ │ │ │ +926EB   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +926EF   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +926F3 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +926F5   Length              000B (11)
│ │ │ │ +926F7   Version             01 (1)
│ │ │ │ +926F8   UID Size            04 (4)
│ │ │ │ +926F9   UID                 00000000 (0)
│ │ │ │ +926FD   GID Size            04 (4)
│ │ │ │ +926FE   GID                 00000000 (0)
│ │ │ │ +92702 PAYLOAD
│ │ │ │ +
│ │ │ │ +93494 LOCAL HEADER #78      04034B50 (67324752)
│ │ │ │ +93498 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +93499 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +9349A General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +9349C Compression Method    0008 (8) 'Deflated'
│ │ │ │ +9349E Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +934A2 CRC                   535B63FB (1398498299)
│ │ │ │ +934A6 Compressed Size       000001DF (479)
│ │ │ │ +934AA Uncompressed Size     00000323 (803)
│ │ │ │ +934AE Filename Length       0011 (17)
│ │ │ │ +934B0 Extra Length          001C (28)
│ │ │ │ +934B2 Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x934B2: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +934C3 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +934C5   Length              0009 (9)
│ │ │ │ +934C7   Flags               03 (3) 'Modification Access'
│ │ │ │ +934C8   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +934CC   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +934D0 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +934D2   Length              000B (11)
│ │ │ │ +934D4   Version             01 (1)
│ │ │ │ +934D5   UID Size            04 (4)
│ │ │ │ +934D6   UID                 00000000 (0)
│ │ │ │ +934DA   GID Size            04 (4)
│ │ │ │ +934DB   GID                 00000000 (0)
│ │ │ │ +934DF PAYLOAD
│ │ │ │ +
│ │ │ │ +936BE LOCAL HEADER #79      04034B50 (67324752)
│ │ │ │ +936C2 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +936C3 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +936C4 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +936C6 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +936C8 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +936CC CRC                   32CAD6D8 (852154072)
│ │ │ │ +936D0 Compressed Size       000006BE (1726)
│ │ │ │ +936D4 Uncompressed Size     0000141F (5151)
│ │ │ │ +936D8 Filename Length       0019 (25)
│ │ │ │ +936DA Extra Length          001C (28)
│ │ │ │ +936DC Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x936DC: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +936F5 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +936F7   Length              0009 (9)
│ │ │ │ +936F9   Flags               03 (3) 'Modification Access'
│ │ │ │ +936FA   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +936FE   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +93702 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +93704   Length              000B (11)
│ │ │ │ +93706   Version             01 (1)
│ │ │ │ +93707   UID Size            04 (4)
│ │ │ │ +93708   UID                 00000000 (0)
│ │ │ │ +9370C   GID Size            04 (4)
│ │ │ │ +9370D   GID                 00000000 (0)
│ │ │ │ +93711 PAYLOAD
│ │ │ │ +
│ │ │ │ +93DCF LOCAL HEADER #80      04034B50 (67324752)
│ │ │ │ +93DD3 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +93DD4 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +93DD5 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +93DD7 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +93DD9 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +93DDD CRC                   3082FD4D (813890893)
│ │ │ │ +93DE1 Compressed Size       00001B8B (7051)
│ │ │ │ +93DE5 Uncompressed Size     00009F5F (40799)
│ │ │ │ +93DE9 Filename Length       0018 (24)
│ │ │ │ +93DEB Extra Length          001C (28)
│ │ │ │ +93DED Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x93DED: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +93E05 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +93E07   Length              0009 (9)
│ │ │ │ +93E09   Flags               03 (3) 'Modification Access'
│ │ │ │ +93E0A   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +93E0E   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +93E12 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +93E14   Length              000B (11)
│ │ │ │ +93E16   Version             01 (1)
│ │ │ │ +93E17   UID Size            04 (4)
│ │ │ │ +93E18   UID                 00000000 (0)
│ │ │ │ +93E1C   GID Size            04 (4)
│ │ │ │ +93E1D   GID                 00000000 (0)
│ │ │ │ +93E21 PAYLOAD
│ │ │ │ +
│ │ │ │ +959AC LOCAL HEADER #81      04034B50 (67324752)
│ │ │ │ +959B0 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +959B1 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +959B2 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +959B4 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +959B6 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +959BA CRC                   1E04A61F (503621151)
│ │ │ │ +959BE Compressed Size       00001700 (5888)
│ │ │ │ +959C2 Uncompressed Size     00008B12 (35602)
│ │ │ │ +959C6 Filename Length       0012 (18)
│ │ │ │ +959C8 Extra Length          001C (28)
│ │ │ │ +959CA Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x959CA: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +959DC Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +959DE   Length              0009 (9)
│ │ │ │ +959E0   Flags               03 (3) 'Modification Access'
│ │ │ │ +959E1   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +959E5   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +959E9 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +959EB   Length              000B (11)
│ │ │ │ +959ED   Version             01 (1)
│ │ │ │ +959EE   UID Size            04 (4)
│ │ │ │ +959EF   UID                 00000000 (0)
│ │ │ │ +959F3   GID Size            04 (4)
│ │ │ │ +959F4   GID                 00000000 (0)
│ │ │ │ +959F8 PAYLOAD
│ │ │ │ +
│ │ │ │ +970F8 LOCAL HEADER #82      04034B50 (67324752)
│ │ │ │ +970FC Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +970FD Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +970FE General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +97100 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +97102 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +97106 CRC                   C9194D7F (3373878655)
│ │ │ │ +9710A Compressed Size       00001E0B (7691)
│ │ │ │ +9710E Uncompressed Size     00008823 (34851)
│ │ │ │ +97112 Filename Length       0016 (22)
│ │ │ │ +97114 Extra Length          001C (28)
│ │ │ │ +97116 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x97116: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +9712C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +9712E   Length              0009 (9)
│ │ │ │ +97130   Flags               03 (3) 'Modification Access'
│ │ │ │ +97131   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +97135   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +97139 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +9713B   Length              000B (11)
│ │ │ │ +9713D   Version             01 (1)
│ │ │ │ +9713E   UID Size            04 (4)
│ │ │ │ +9713F   UID                 00000000 (0)
│ │ │ │ +97143   GID Size            04 (4)
│ │ │ │ +97144   GID                 00000000 (0)
│ │ │ │ +97148 PAYLOAD
│ │ │ │ +
│ │ │ │ +98F53 LOCAL HEADER #83      04034B50 (67324752)
│ │ │ │ +98F57 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +98F58 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +98F59 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +98F5B Compression Method    0008 (8) 'Deflated'
│ │ │ │ +98F5D Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +98F61 CRC                   FC5E70B2 (4234047666)
│ │ │ │ +98F65 Compressed Size       000029A9 (10665)
│ │ │ │ +98F69 Uncompressed Size     0000D04F (53327)
│ │ │ │ +98F6D Filename Length       001A (26)
│ │ │ │ +98F6F Extra Length          001C (28)
│ │ │ │ +98F71 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x98F71: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +98F8B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +98F8D   Length              0009 (9)
│ │ │ │ +98F8F   Flags               03 (3) 'Modification Access'
│ │ │ │ +98F90   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +98F94   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +98F98 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +98F9A   Length              000B (11)
│ │ │ │ +98F9C   Version             01 (1)
│ │ │ │ +98F9D   UID Size            04 (4)
│ │ │ │ +98F9E   UID                 00000000 (0)
│ │ │ │ +98FA2   GID Size            04 (4)
│ │ │ │ +98FA3   GID                 00000000 (0)
│ │ │ │ +98FA7 PAYLOAD
│ │ │ │ +
│ │ │ │ +9B950 LOCAL HEADER #84      04034B50 (67324752)
│ │ │ │ +9B954 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +9B955 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +9B956 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +9B958 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +9B95A Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +9B95E CRC                   8529CAAD (2234108589)
│ │ │ │ +9B962 Compressed Size       000009AB (2475)
│ │ │ │ +9B966 Uncompressed Size     00001DAC (7596)
│ │ │ │ +9B96A Filename Length       0018 (24)
│ │ │ │ +9B96C Extra Length          001C (28)
│ │ │ │ +9B96E Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x9B96E: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +9B986 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +9B988   Length              0009 (9)
│ │ │ │ +9B98A   Flags               03 (3) 'Modification Access'
│ │ │ │ +9B98B   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +9B98F   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +9B993 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +9B995   Length              000B (11)
│ │ │ │ +9B997   Version             01 (1)
│ │ │ │ +9B998   UID Size            04 (4)
│ │ │ │ +9B999   UID                 00000000 (0)
│ │ │ │ +9B99D   GID Size            04 (4)
│ │ │ │ +9B99E   GID                 00000000 (0)
│ │ │ │ +9B9A2 PAYLOAD
│ │ │ │ +
│ │ │ │ +9C34D LOCAL HEADER #85      04034B50 (67324752)
│ │ │ │ +9C351 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +9C352 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +9C353 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +9C355 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +9C357 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +9C35B CRC                   F0556E9A (4032130714)
│ │ │ │ +9C35F Compressed Size       000152EE (86766)
│ │ │ │ +9C363 Uncompressed Size     000159F8 (88568)
│ │ │ │ +9C367 Filename Length       001E (30)
│ │ │ │ +9C369 Extra Length          001C (28)
│ │ │ │ +9C36B Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x9C36B: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +9C389 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +9C38B   Length              0009 (9)
│ │ │ │ +9C38D   Flags               03 (3) 'Modification Access'
│ │ │ │ +9C38E   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +9C392   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +9C396 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +9C398   Length              000B (11)
│ │ │ │ +9C39A   Version             01 (1)
│ │ │ │ +9C39B   UID Size            04 (4)
│ │ │ │ +9C39C   UID                 00000000 (0)
│ │ │ │ +9C3A0   GID Size            04 (4)
│ │ │ │ +9C3A1   GID                 00000000 (0)
│ │ │ │ +9C3A5 PAYLOAD
│ │ │ │ +
│ │ │ │ +B1693 LOCAL HEADER #86      04034B50 (67324752)
│ │ │ │ +B1697 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +B1698 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +B1699 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +B169B Compression Method    0008 (8) 'Deflated'
│ │ │ │ +B169D Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +B16A1 CRC                   F5E2129F (4125233823)
│ │ │ │ +B16A5 Compressed Size       000016BC (5820)
│ │ │ │ +B16A9 Uncompressed Size     000016CD (5837)
│ │ │ │ +B16AD Filename Length       0015 (21)
│ │ │ │ +B16AF Extra Length          001C (28)
│ │ │ │ +B16B1 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xB16B1: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +B16C6 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +B16C8   Length              0009 (9)
│ │ │ │ +B16CA   Flags               03 (3) 'Modification Access'
│ │ │ │ +B16CB   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +B16CF   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +B16D3 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +B16D5   Length              000B (11)
│ │ │ │ +B16D7   Version             01 (1)
│ │ │ │ +B16D8   UID Size            04 (4)
│ │ │ │ +B16D9   UID                 00000000 (0)
│ │ │ │ +B16DD   GID Size            04 (4)
│ │ │ │ +B16DE   GID                 00000000 (0)
│ │ │ │ +B16E2 PAYLOAD
│ │ │ │ +
│ │ │ │ +B2D9E LOCAL HEADER #87      04034B50 (67324752)
│ │ │ │ +B2DA2 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +B2DA3 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +B2DA4 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +B2DA6 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +B2DA8 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +B2DAC CRC                   F5E2129F (4125233823)
│ │ │ │ +B2DB0 Compressed Size       000016BC (5820)
│ │ │ │ +B2DB4 Uncompressed Size     000016CD (5837)
│ │ │ │ +B2DB8 Filename Length       001C (28)
│ │ │ │ +B2DBA Extra Length          001C (28)
│ │ │ │ +B2DBC Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xB2DBC: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +B2DD8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +B2DDA   Length              0009 (9)
│ │ │ │ +B2DDC   Flags               03 (3) 'Modification Access'
│ │ │ │ +B2DDD   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +B2DE1   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +B2DE5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +B2DE7   Length              000B (11)
│ │ │ │ +B2DE9   Version             01 (1)
│ │ │ │ +B2DEA   UID Size            04 (4)
│ │ │ │ +B2DEB   UID                 00000000 (0)
│ │ │ │ +B2DEF   GID Size            04 (4)
│ │ │ │ +B2DF0   GID                 00000000 (0)
│ │ │ │ +B2DF4 PAYLOAD
│ │ │ │ +
│ │ │ │ +B44B0 LOCAL HEADER #88      04034B50 (67324752)
│ │ │ │ +B44B4 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ +B44B5 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +B44B6 General Purpose Flag  0000 (0)
│ │ │ │ +B44B8 Compression Method    0000 (0) 'Stored'
│ │ │ │ +B44BA Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +B44BE CRC                   FC95F24B (4237685323)
│ │ │ │ +B44C2 Compressed Size       00001B84 (7044)
│ │ │ │ +B44C6 Uncompressed Size     00001B84 (7044)
│ │ │ │ +B44CA Filename Length       0016 (22)
│ │ │ │ +B44CC Extra Length          001C (28)
│ │ │ │ +B44CE Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xB44CE: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +B44E4 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +B44E6   Length              0009 (9)
│ │ │ │ +B44E8   Flags               03 (3) 'Modification Access'
│ │ │ │ +B44E9   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +B44ED   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +B44F1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +B44F3   Length              000B (11)
│ │ │ │ +B44F5   Version             01 (1)
│ │ │ │ +B44F6   UID Size            04 (4)
│ │ │ │ +B44F7   UID                 00000000 (0)
│ │ │ │ +B44FB   GID Size            04 (4)
│ │ │ │ +B44FC   GID                 00000000 (0)
│ │ │ │ +B4500 PAYLOAD
│ │ │ │ +
│ │ │ │ +B6084 LOCAL HEADER #89      04034B50 (67324752)
│ │ │ │ +B6088 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ +B6089 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +B608A General Purpose Flag  0000 (0)
│ │ │ │ +B608C Compression Method    0000 (0) 'Stored'
│ │ │ │ +B608E Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +B6092 CRC                   D0D71F86 (3503759238)
│ │ │ │ +B6096 Compressed Size       00000B7B (2939)
│ │ │ │ +B609A Uncompressed Size     00000B7B (2939)
│ │ │ │ +B609E Filename Length       0016 (22)
│ │ │ │ +B60A0 Extra Length          001C (28)
│ │ │ │ +B60A2 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xB60A2: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +B60B8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +B60BA   Length              0009 (9)
│ │ │ │ +B60BC   Flags               03 (3) 'Modification Access'
│ │ │ │ +B60BD   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +B60C1   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +B60C5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +B60C7   Length              000B (11)
│ │ │ │ +B60C9   Version             01 (1)
│ │ │ │ +B60CA   UID Size            04 (4)
│ │ │ │ +B60CB   UID                 00000000 (0)
│ │ │ │ +B60CF   GID Size            04 (4)
│ │ │ │ +B60D0   GID                 00000000 (0)
│ │ │ │ +B60D4 PAYLOAD
│ │ │ │ +
│ │ │ │ +B6C4F LOCAL HEADER #90      04034B50 (67324752)
│ │ │ │ +B6C53 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ +B6C54 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +B6C55 General Purpose Flag  0000 (0)
│ │ │ │ +B6C57 Compression Method    0000 (0) 'Stored'
│ │ │ │ +B6C59 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +B6C5D CRC                   FFF9C4D2 (4294558930)
│ │ │ │ +B6C61 Compressed Size       0000138F (5007)
│ │ │ │ +B6C65 Uncompressed Size     0000138F (5007)
│ │ │ │ +B6C69 Filename Length       0016 (22)
│ │ │ │ +B6C6B Extra Length          001C (28)
│ │ │ │ +B6C6D Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xB6C6D: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +B6C83 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +B6C85   Length              0009 (9)
│ │ │ │ +B6C87   Flags               03 (3) 'Modification Access'
│ │ │ │ +B6C88   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +B6C8C   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +B6C90 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +B6C92   Length              000B (11)
│ │ │ │ +B6C94   Version             01 (1)
│ │ │ │ +B6C95   UID Size            04 (4)
│ │ │ │ +B6C96   UID                 00000000 (0)
│ │ │ │ +B6C9A   GID Size            04 (4)
│ │ │ │ +B6C9B   GID                 00000000 (0)
│ │ │ │ +B6C9F PAYLOAD
│ │ │ │ +
│ │ │ │ +B802E LOCAL HEADER #91      04034B50 (67324752)
│ │ │ │ +B8032 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ +B8033 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +B8034 General Purpose Flag  0000 (0)
│ │ │ │ +B8036 Compression Method    0000 (0) 'Stored'
│ │ │ │ +B8038 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +B803C CRC                   A1037E8E (2701360782)
│ │ │ │ +B8040 Compressed Size       0000145E (5214)
│ │ │ │ +B8044 Uncompressed Size     0000145E (5214)
│ │ │ │ +B8048 Filename Length       0016 (22)
│ │ │ │ +B804A Extra Length          001C (28)
│ │ │ │ +B804C Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xB804C: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +B8062 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +B8064   Length              0009 (9)
│ │ │ │ +B8066   Flags               03 (3) 'Modification Access'
│ │ │ │ +B8067   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +B806B   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +B806F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +B8071   Length              000B (11)
│ │ │ │ +B8073   Version             01 (1)
│ │ │ │ +B8074   UID Size            04 (4)
│ │ │ │ +B8075   UID                 00000000 (0)
│ │ │ │ +B8079   GID Size            04 (4)
│ │ │ │ +B807A   GID                 00000000 (0)
│ │ │ │ +B807E PAYLOAD
│ │ │ │ +
│ │ │ │ +B94DC LOCAL HEADER #92      04034B50 (67324752)
│ │ │ │ +B94E0 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ +B94E1 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +B94E2 General Purpose Flag  0000 (0)
│ │ │ │ +B94E4 Compression Method    0000 (0) 'Stored'
│ │ │ │ +B94E6 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +B94EA CRC                   5E9E64F1 (1587438833)
│ │ │ │ +B94EE Compressed Size       000008EC (2284)
│ │ │ │ +B94F2 Uncompressed Size     000008EC (2284)
│ │ │ │ +B94F6 Filename Length       0016 (22)
│ │ │ │ +B94F8 Extra Length          001C (28)
│ │ │ │ +B94FA Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xB94FA: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +B9510 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +B9512   Length              0009 (9)
│ │ │ │ +B9514   Flags               03 (3) 'Modification Access'
│ │ │ │ +B9515   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +B9519   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +B951D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +B951F   Length              000B (11)
│ │ │ │ +B9521   Version             01 (1)
│ │ │ │ +B9522   UID Size            04 (4)
│ │ │ │ +B9523   UID                 00000000 (0)
│ │ │ │ +B9527   GID Size            04 (4)
│ │ │ │ +B9528   GID                 00000000 (0)
│ │ │ │ +B952C PAYLOAD
│ │ │ │ +
│ │ │ │ +B9E18 LOCAL HEADER #93      04034B50 (67324752)
│ │ │ │ +B9E1C Extract Zip Spec      0A (10) '1.0'
│ │ │ │ +B9E1D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +B9E1E General Purpose Flag  0000 (0)
│ │ │ │ +B9E20 Compression Method    0000 (0) 'Stored'
│ │ │ │ +B9E22 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +B9E26 CRC                   42E340AB (1122189483)
│ │ │ │ +B9E2A Compressed Size       00001F2E (7982)
│ │ │ │ +B9E2E Uncompressed Size     00001F2E (7982)
│ │ │ │ +B9E32 Filename Length       001E (30)
│ │ │ │ +B9E34 Extra Length          001C (28)
│ │ │ │ +B9E36 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xB9E36: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +B9E54 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +B9E56   Length              0009 (9)
│ │ │ │ +B9E58   Flags               03 (3) 'Modification Access'
│ │ │ │ +B9E59   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +B9E5D   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +B9E61 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +B9E63   Length              000B (11)
│ │ │ │ +B9E65   Version             01 (1)
│ │ │ │ +B9E66   UID Size            04 (4)
│ │ │ │ +B9E67   UID                 00000000 (0)
│ │ │ │ +B9E6B   GID Size            04 (4)
│ │ │ │ +B9E6C   GID                 00000000 (0)
│ │ │ │ +B9E70 PAYLOAD
│ │ │ │ +
│ │ │ │ +BBD9E LOCAL HEADER #94      04034B50 (67324752)
│ │ │ │ +BBDA2 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +BBDA3 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +BBDA4 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +BBDA6 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +BBDA8 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +BBDAC CRC                   28F7826D (687309421)
│ │ │ │ +BBDB0 Compressed Size       00003D80 (15744)
│ │ │ │ +BBDB4 Uncompressed Size     000166B0 (91824)
│ │ │ │ +BBDB8 Filename Length       001A (26)
│ │ │ │ +BBDBA Extra Length          001C (28)
│ │ │ │ +BBDBC Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xBBDBC: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +BBDD6 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +BBDD8   Length              0009 (9)
│ │ │ │ +BBDDA   Flags               03 (3) 'Modification Access'
│ │ │ │ +BBDDB   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +BBDDF   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +BBDE3 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +BBDE5   Length              000B (11)
│ │ │ │ +BBDE7   Version             01 (1)
│ │ │ │ +BBDE8   UID Size            04 (4)
│ │ │ │ +BBDE9   UID                 00000000 (0)
│ │ │ │ +BBDED   GID Size            04 (4)
│ │ │ │ +BBDEE   GID                 00000000 (0)
│ │ │ │ +BBDF2 PAYLOAD
│ │ │ │ +
│ │ │ │ +BFB72 LOCAL HEADER #95      04034B50 (67324752)
│ │ │ │ +BFB76 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +BFB77 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +BFB78 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +BFB7A Compression Method    0008 (8) 'Deflated'
│ │ │ │ +BFB7C Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +BFB80 CRC                   B0D0A5F7 (2966463991)
│ │ │ │ +BFB84 Compressed Size       000029D0 (10704)
│ │ │ │ +BFB88 Uncompressed Size     0000BB3A (47930)
│ │ │ │ +BFB8C Filename Length       0018 (24)
│ │ │ │ +BFB8E Extra Length          001C (28)
│ │ │ │ +BFB90 Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xBFB90: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +BFBA8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +BFBAA   Length              0009 (9)
│ │ │ │ +BFBAC   Flags               03 (3) 'Modification Access'
│ │ │ │ +BFBAD   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +BFBB1   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +BFBB5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +BFBB7   Length              000B (11)
│ │ │ │ +BFBB9   Version             01 (1)
│ │ │ │ +BFBBA   UID Size            04 (4)
│ │ │ │ +BFBBB   UID                 00000000 (0)
│ │ │ │ +BFBBF   GID Size            04 (4)
│ │ │ │ +BFBC0   GID                 00000000 (0)
│ │ │ │ +BFBC4 PAYLOAD
│ │ │ │ +
│ │ │ │ +C2594 LOCAL HEADER #96      04034B50 (67324752)
│ │ │ │ +C2598 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2599 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C259A General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C259C Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C259E Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C25A2 CRC                   DCB3B516 (3702764822)
│ │ │ │ +C25A6 Compressed Size       000000AE (174)
│ │ │ │ +C25AA Uncompressed Size     000000FC (252)
│ │ │ │ +C25AE Filename Length       0016 (22)
│ │ │ │ +C25B0 Extra Length          001C (28)
│ │ │ │ +C25B2 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC25B2: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C25C8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C25CA   Length              0009 (9)
│ │ │ │ +C25CC   Flags               03 (3) 'Modification Access'
│ │ │ │ +C25CD   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C25D1   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C25D5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C25D7   Length              000B (11)
│ │ │ │ +C25D9   Version             01 (1)
│ │ │ │ +C25DA   UID Size            04 (4)
│ │ │ │ +C25DB   UID                 00000000 (0)
│ │ │ │ +C25DF   GID Size            04 (4)
│ │ │ │ +C25E0   GID                 00000000 (0)
│ │ │ │ +C25E4 PAYLOAD               XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
│ │ │ │                              XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
│ │ │ │  
│ │ │ │ -C2684 LOCAL HEADER #97      04034B50 (67324752)
│ │ │ │ -C2688 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2689 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C268A General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C268C Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C268E Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C2692 CRC                   58439733 (1480824627)
│ │ │ │ -C2696 Compressed Size       00000077 (119)
│ │ │ │ -C269A Uncompressed Size     000000A2 (162)
│ │ │ │ -C269E Filename Length       002D (45)
│ │ │ │ -C26A0 Extra Length          001C (28)
│ │ │ │ -C26A2 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC26A2: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C26CF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C26D1   Length              0009 (9)
│ │ │ │ -C26D3   Flags               03 (3) 'Modification Access'
│ │ │ │ -C26D4   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C26D8   Access Time         69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C26DC Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C26DE   Length              000B (11)
│ │ │ │ -C26E0   Version             01 (1)
│ │ │ │ -C26E1   UID Size            04 (4)
│ │ │ │ -C26E2   UID                 00000000 (0)
│ │ │ │ -C26E6   GID Size            04 (4)
│ │ │ │ -C26E7   GID                 00000000 (0)
│ │ │ │ -C26EB PAYLOAD               XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
│ │ │ │ -
│ │ │ │ -C2762 CENTRAL HEADER #1     02014B50 (33639248)
│ │ │ │ -C2766 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2767 Created OS            03 (3) 'Unix'
│ │ │ │ -C2768 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -C2769 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C276A General Purpose Flag  0000 (0)
│ │ │ │ -C276C Compression Method    0000 (0) 'Stored'
│ │ │ │ -C276E Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2772 CRC                   2CAB616F (749429103)
│ │ │ │ -C2776 Compressed Size       00000014 (20)
│ │ │ │ -C277A Uncompressed Size     00000014 (20)
│ │ │ │ -C277E Filename Length       0008 (8)
│ │ │ │ -C2780 Extra Length          0018 (24)
│ │ │ │ -C2782 Comment Length        0000 (0)
│ │ │ │ -C2784 Disk Start            0000 (0)
│ │ │ │ -C2786 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2788 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C278C Local Header Offset   00000000 (0)
│ │ │ │ -C2790 Filename              'XXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2790: Filename 'XXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2798 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C279A   Length              0005 (5)
│ │ │ │ -C279C   Flags               01 (1) 'Modification'
│ │ │ │ -C279D   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C27A1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C27A3   Length              000B (11)
│ │ │ │ -C27A5   Version             01 (1)
│ │ │ │ -C27A6   UID Size            04 (4)
│ │ │ │ -C27A7   UID                 00000000 (0)
│ │ │ │ -C27AB   GID Size            04 (4)
│ │ │ │ -C27AC   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C27B0 CENTRAL HEADER #2     02014B50 (33639248)
│ │ │ │ -C27B4 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C27B5 Created OS            03 (3) 'Unix'
│ │ │ │ -C27B6 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C27B7 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C27B8 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C27BA Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C27BC Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C27C0 CRC                   29F05690 (703616656)
│ │ │ │ -C27C4 Compressed Size       00000D24 (3364)
│ │ │ │ -C27C8 Uncompressed Size     00003933 (14643)
│ │ │ │ -C27CC Filename Length       001B (27)
│ │ │ │ -C27CE Extra Length          0018 (24)
│ │ │ │ -C27D0 Comment Length        0000 (0)
│ │ │ │ -C27D2 Disk Start            0000 (0)
│ │ │ │ -C27D4 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C27D6 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C27DA Local Header Offset   00000056 (86)
│ │ │ │ -C27DE Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC27DE: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C27F9 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C27FB   Length              0005 (5)
│ │ │ │ -C27FD   Flags               01 (1) 'Modification'
│ │ │ │ -C27FE   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2802 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2804   Length              000B (11)
│ │ │ │ -C2806   Version             01 (1)
│ │ │ │ -C2807   UID Size            04 (4)
│ │ │ │ -C2808   UID                 00000000 (0)
│ │ │ │ -C280C   GID Size            04 (4)
│ │ │ │ -C280D   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2811 CENTRAL HEADER #3     02014B50 (33639248)
│ │ │ │ -C2815 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2816 Created OS            03 (3) 'Unix'
│ │ │ │ -C2817 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2818 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2819 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C281B Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C281D Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2821 CRC                   546A35FD (1416246781)
│ │ │ │ -C2825 Compressed Size       000015B1 (5553)
│ │ │ │ -C2829 Uncompressed Size     00004605 (17925)
│ │ │ │ -C282D Filename Length       0014 (20)
│ │ │ │ -C282F Extra Length          0018 (24)
│ │ │ │ -C2831 Comment Length        0000 (0)
│ │ │ │ -C2833 Disk Start            0000 (0)
│ │ │ │ -C2835 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2837 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C283B Local Header Offset   00000DCF (3535)
│ │ │ │ -C283F Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC283F: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2853 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2855   Length              0005 (5)
│ │ │ │ -C2857   Flags               01 (1) 'Modification'
│ │ │ │ -C2858   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C285C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C285E   Length              000B (11)
│ │ │ │ -C2860   Version             01 (1)
│ │ │ │ -C2861   UID Size            04 (4)
│ │ │ │ -C2862   UID                 00000000 (0)
│ │ │ │ -C2866   GID Size            04 (4)
│ │ │ │ -C2867   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C286B CENTRAL HEADER #4     02014B50 (33639248)
│ │ │ │ -C286F Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2870 Created OS            03 (3) 'Unix'
│ │ │ │ -C2871 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2872 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2873 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2875 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2877 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C287B CRC                   03A4A46E (61121646)
│ │ │ │ -C287F Compressed Size       000006D4 (1748)
│ │ │ │ -C2883 Uncompressed Size     00001241 (4673)
│ │ │ │ -C2887 Filename Length       0013 (19)
│ │ │ │ -C2889 Extra Length          0018 (24)
│ │ │ │ -C288B Comment Length        0000 (0)
│ │ │ │ -C288D Disk Start            0000 (0)
│ │ │ │ -C288F Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2891 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2895 Local Header Offset   000023CE (9166)
│ │ │ │ -C2899 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2899: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C28AC Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C28AE   Length              0005 (5)
│ │ │ │ -C28B0   Flags               01 (1) 'Modification'
│ │ │ │ -C28B1   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C28B5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C28B7   Length              000B (11)
│ │ │ │ -C28B9   Version             01 (1)
│ │ │ │ -C28BA   UID Size            04 (4)
│ │ │ │ -C28BB   UID                 00000000 (0)
│ │ │ │ -C28BF   GID Size            04 (4)
│ │ │ │ -C28C0   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C28C4 CENTRAL HEADER #5     02014B50 (33639248)
│ │ │ │ -C28C8 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C28C9 Created OS            03 (3) 'Unix'
│ │ │ │ -C28CA Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C28CB Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C28CC General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C28CE Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C28D0 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C28D4 CRC                   404477C9 (1078228937)
│ │ │ │ -C28D8 Compressed Size       00002E75 (11893)
│ │ │ │ -C28DC Uncompressed Size     0000D4C1 (54465)
│ │ │ │ -C28E0 Filename Length       0014 (20)
│ │ │ │ -C28E2 Extra Length          0018 (24)
│ │ │ │ -C28E4 Comment Length        0000 (0)
│ │ │ │ -C28E6 Disk Start            0000 (0)
│ │ │ │ -C28E8 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C28EA Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C28EE Local Header Offset   00002AEF (10991)
│ │ │ │ -C28F2 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC28F2: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2906 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2908   Length              0005 (5)
│ │ │ │ -C290A   Flags               01 (1) 'Modification'
│ │ │ │ -C290B   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C290F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2911   Length              000B (11)
│ │ │ │ -C2913   Version             01 (1)
│ │ │ │ -C2914   UID Size            04 (4)
│ │ │ │ -C2915   UID                 00000000 (0)
│ │ │ │ -C2919   GID Size            04 (4)
│ │ │ │ -C291A   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C291E CENTRAL HEADER #6     02014B50 (33639248)
│ │ │ │ -C2922 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2923 Created OS            03 (3) 'Unix'
│ │ │ │ -C2924 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2925 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2926 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2928 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C292A Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C292E CRC                   272DD323 (657314595)
│ │ │ │ -C2932 Compressed Size       000003EF (1007)
│ │ │ │ -C2936 Uncompressed Size     00000876 (2166)
│ │ │ │ -C293A Filename Length       0014 (20)
│ │ │ │ -C293C Extra Length          0018 (24)
│ │ │ │ -C293E Comment Length        0000 (0)
│ │ │ │ -C2940 Disk Start            0000 (0)
│ │ │ │ -C2942 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2944 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2948 Local Header Offset   000059B2 (22962)
│ │ │ │ -C294C Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC294C: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2960 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2962   Length              0005 (5)
│ │ │ │ -C2964   Flags               01 (1) 'Modification'
│ │ │ │ -C2965   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2969 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C296B   Length              000B (11)
│ │ │ │ -C296D   Version             01 (1)
│ │ │ │ -C296E   UID Size            04 (4)
│ │ │ │ -C296F   UID                 00000000 (0)
│ │ │ │ -C2973   GID Size            04 (4)
│ │ │ │ -C2974   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2978 CENTRAL HEADER #7     02014B50 (33639248)
│ │ │ │ -C297C Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C297D Created OS            03 (3) 'Unix'
│ │ │ │ -C297E Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C297F Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2980 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2982 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2984 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2988 CRC                   2F07766F (789018223)
│ │ │ │ -C298C Compressed Size       000001AD (429)
│ │ │ │ -C2990 Uncompressed Size     000002FC (764)
│ │ │ │ -C2994 Filename Length       0011 (17)
│ │ │ │ -C2996 Extra Length          0018 (24)
│ │ │ │ -C2998 Comment Length        0000 (0)
│ │ │ │ -C299A Disk Start            0000 (0)
│ │ │ │ -C299C Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C299E Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C29A2 Local Header Offset   00005DEF (24047)
│ │ │ │ -C29A6 Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC29A6: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C29B7 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C29B9   Length              0005 (5)
│ │ │ │ -C29BB   Flags               01 (1) 'Modification'
│ │ │ │ -C29BC   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C29C0 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C29C2   Length              000B (11)
│ │ │ │ -C29C4   Version             01 (1)
│ │ │ │ -C29C5   UID Size            04 (4)
│ │ │ │ -C29C6   UID                 00000000 (0)
│ │ │ │ -C29CA   GID Size            04 (4)
│ │ │ │ -C29CB   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C29CF CENTRAL HEADER #8     02014B50 (33639248)
│ │ │ │ -C29D3 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C29D4 Created OS            03 (3) 'Unix'
│ │ │ │ -C29D5 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C29D6 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C29D7 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C29D9 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C29DB Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C29DF CRC                   AD55D2AE (2908082862)
│ │ │ │ -C29E3 Compressed Size       000020BE (8382)
│ │ │ │ -C29E7 Uncompressed Size     0000B4B1 (46257)
│ │ │ │ -C29EB Filename Length       001B (27)
│ │ │ │ -C29ED Extra Length          0018 (24)
│ │ │ │ -C29EF Comment Length        0000 (0)
│ │ │ │ -C29F1 Disk Start            0000 (0)
│ │ │ │ -C29F3 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C29F5 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C29F9 Local Header Offset   00005FE7 (24551)
│ │ │ │ -C29FD Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC29FD: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2A18 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2A1A   Length              0005 (5)
│ │ │ │ -C2A1C   Flags               01 (1) 'Modification'
│ │ │ │ -C2A1D   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2A21 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2A23   Length              000B (11)
│ │ │ │ -C2A25   Version             01 (1)
│ │ │ │ -C2A26   UID Size            04 (4)
│ │ │ │ -C2A27   UID                 00000000 (0)
│ │ │ │ -C2A2B   GID Size            04 (4)
│ │ │ │ -C2A2C   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2A30 CENTRAL HEADER #9     02014B50 (33639248)
│ │ │ │ -C2A34 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2A35 Created OS            03 (3) 'Unix'
│ │ │ │ -C2A36 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2A37 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2A38 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2A3A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2A3C Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2A40 CRC                   4E72FA06 (1316157958)
│ │ │ │ -C2A44 Compressed Size       00000E68 (3688)
│ │ │ │ -C2A48 Uncompressed Size     00003097 (12439)
│ │ │ │ -C2A4C Filename Length       001D (29)
│ │ │ │ -C2A4E Extra Length          0018 (24)
│ │ │ │ -C2A50 Comment Length        0000 (0)
│ │ │ │ -C2A52 Disk Start            0000 (0)
│ │ │ │ -C2A54 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2A56 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2A5A Local Header Offset   000080FA (33018)
│ │ │ │ -C2A5E Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2A5E: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2A7B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2A7D   Length              0005 (5)
│ │ │ │ -C2A7F   Flags               01 (1) 'Modification'
│ │ │ │ -C2A80   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2A84 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2A86   Length              000B (11)
│ │ │ │ -C2A88   Version             01 (1)
│ │ │ │ -C2A89   UID Size            04 (4)
│ │ │ │ -C2A8A   UID                 00000000 (0)
│ │ │ │ -C2A8E   GID Size            04 (4)
│ │ │ │ -C2A8F   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2A93 CENTRAL HEADER #10    02014B50 (33639248)
│ │ │ │ -C2A97 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2A98 Created OS            03 (3) 'Unix'
│ │ │ │ -C2A99 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2A9A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2A9B General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2A9D Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2A9F Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2AA3 CRC                   F138337A (4046992250)
│ │ │ │ -C2AA7 Compressed Size       0000098E (2446)
│ │ │ │ -C2AAB Uncompressed Size     00001D39 (7481)
│ │ │ │ -C2AAF Filename Length       0019 (25)
│ │ │ │ -C2AB1 Extra Length          0018 (24)
│ │ │ │ -C2AB3 Comment Length        0000 (0)
│ │ │ │ -C2AB5 Disk Start            0000 (0)
│ │ │ │ -C2AB7 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2AB9 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2ABD Local Header Offset   00008FB9 (36793)
│ │ │ │ -C2AC1 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2AC1: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2ADA Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2ADC   Length              0005 (5)
│ │ │ │ -C2ADE   Flags               01 (1) 'Modification'
│ │ │ │ -C2ADF   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2AE3 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2AE5   Length              000B (11)
│ │ │ │ -C2AE7   Version             01 (1)
│ │ │ │ -C2AE8   UID Size            04 (4)
│ │ │ │ -C2AE9   UID                 00000000 (0)
│ │ │ │ -C2AED   GID Size            04 (4)
│ │ │ │ -C2AEE   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2AF2 CENTRAL HEADER #11    02014B50 (33639248)
│ │ │ │ -C2AF6 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2AF7 Created OS            03 (3) 'Unix'
│ │ │ │ -C2AF8 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2AF9 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2AFA General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2AFC Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2AFE Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2B02 CRC                   FC4F496F (4233054575)
│ │ │ │ -C2B06 Compressed Size       00003883 (14467)
│ │ │ │ -C2B0A Uncompressed Size     0000F81F (63519)
│ │ │ │ -C2B0E Filename Length       0015 (21)
│ │ │ │ -C2B10 Extra Length          0018 (24)
│ │ │ │ -C2B12 Comment Length        0000 (0)
│ │ │ │ -C2B14 Disk Start            0000 (0)
│ │ │ │ -C2B16 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2B18 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2B1C Local Header Offset   0000999A (39322)
│ │ │ │ -C2B20 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2B20: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2B35 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2B37   Length              0005 (5)
│ │ │ │ -C2B39   Flags               01 (1) 'Modification'
│ │ │ │ -C2B3A   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2B3E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2B40   Length              000B (11)
│ │ │ │ -C2B42   Version             01 (1)
│ │ │ │ -C2B43   UID Size            04 (4)
│ │ │ │ -C2B44   UID                 00000000 (0)
│ │ │ │ -C2B48   GID Size            04 (4)
│ │ │ │ -C2B49   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2B4D CENTRAL HEADER #12    02014B50 (33639248)
│ │ │ │ -C2B51 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2B52 Created OS            03 (3) 'Unix'
│ │ │ │ -C2B53 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2B54 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2B55 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2B57 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2B59 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2B5D CRC                   0BB598F2 (196450546)
│ │ │ │ -C2B61 Compressed Size       0000AAFA (43770)
│ │ │ │ -C2B65 Uncompressed Size     0003E0D8 (254168)
│ │ │ │ -C2B69 Filename Length       0012 (18)
│ │ │ │ -C2B6B Extra Length          0018 (24)
│ │ │ │ -C2B6D Comment Length        0000 (0)
│ │ │ │ -C2B6F Disk Start            0000 (0)
│ │ │ │ -C2B71 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2B73 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2B77 Local Header Offset   0000D26C (53868)
│ │ │ │ -C2B7B Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2B7B: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2B8D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2B8F   Length              0005 (5)
│ │ │ │ -C2B91   Flags               01 (1) 'Modification'
│ │ │ │ -C2B92   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2B96 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2B98   Length              000B (11)
│ │ │ │ -C2B9A   Version             01 (1)
│ │ │ │ -C2B9B   UID Size            04 (4)
│ │ │ │ -C2B9C   UID                 00000000 (0)
│ │ │ │ -C2BA0   GID Size            04 (4)
│ │ │ │ -C2BA1   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2BA5 CENTRAL HEADER #13    02014B50 (33639248)
│ │ │ │ -C2BA9 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2BAA Created OS            03 (3) 'Unix'
│ │ │ │ -C2BAB Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2BAC Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2BAD General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2BAF Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2BB1 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2BB5 CRC                   C50A848B (3305800843)
│ │ │ │ -C2BB9 Compressed Size       00003AF8 (15096)
│ │ │ │ -C2BBD Uncompressed Size     0001B421 (111649)
│ │ │ │ -C2BC1 Filename Length       0015 (21)
│ │ │ │ -C2BC3 Extra Length          0018 (24)
│ │ │ │ -C2BC5 Comment Length        0000 (0)
│ │ │ │ -C2BC7 Disk Start            0000 (0)
│ │ │ │ -C2BC9 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2BCB Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2BCF Local Header Offset   00017DB2 (97714)
│ │ │ │ -C2BD3 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2BD3: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2BE8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2BEA   Length              0005 (5)
│ │ │ │ -C2BEC   Flags               01 (1) 'Modification'
│ │ │ │ -C2BED   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2BF1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2BF3   Length              000B (11)
│ │ │ │ -C2BF5   Version             01 (1)
│ │ │ │ -C2BF6   UID Size            04 (4)
│ │ │ │ -C2BF7   UID                 00000000 (0)
│ │ │ │ -C2BFB   GID Size            04 (4)
│ │ │ │ -C2BFC   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2C00 CENTRAL HEADER #14    02014B50 (33639248)
│ │ │ │ -C2C04 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2C05 Created OS            03 (3) 'Unix'
│ │ │ │ -C2C06 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2C07 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2C08 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2C0A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2C0C Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2C10 CRC                   B6C2DA9C (3066223260)
│ │ │ │ -C2C14 Compressed Size       000091C5 (37317)
│ │ │ │ -C2C18 Uncompressed Size     0003DBD1 (252881)
│ │ │ │ -C2C1C Filename Length       0014 (20)
│ │ │ │ -C2C1E Extra Length          0018 (24)
│ │ │ │ -C2C20 Comment Length        0000 (0)
│ │ │ │ -C2C22 Disk Start            0000 (0)
│ │ │ │ -C2C24 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2C26 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2C2A Local Header Offset   0001B8F9 (112889)
│ │ │ │ -C2C2E Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2C2E: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2C42 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2C44   Length              0005 (5)
│ │ │ │ -C2C46   Flags               01 (1) 'Modification'
│ │ │ │ -C2C47   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2C4B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2C4D   Length              000B (11)
│ │ │ │ -C2C4F   Version             01 (1)
│ │ │ │ -C2C50   UID Size            04 (4)
│ │ │ │ -C2C51   UID                 00000000 (0)
│ │ │ │ -C2C55   GID Size            04 (4)
│ │ │ │ -C2C56   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2C5A CENTRAL HEADER #15    02014B50 (33639248)
│ │ │ │ -C2C5E Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2C5F Created OS            03 (3) 'Unix'
│ │ │ │ -C2C60 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2C61 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2C62 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2C64 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2C66 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2C6A CRC                   6E4D0A9B (1850542747)
│ │ │ │ -C2C6E Compressed Size       00009BA8 (39848)
│ │ │ │ -C2C72 Uncompressed Size     00027CF5 (163061)
│ │ │ │ -C2C76 Filename Length       0019 (25)
│ │ │ │ -C2C78 Extra Length          0018 (24)
│ │ │ │ -C2C7A Comment Length        0000 (0)
│ │ │ │ -C2C7C Disk Start            0000 (0)
│ │ │ │ -C2C7E Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2C80 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2C84 Local Header Offset   00024B0C (150284)
│ │ │ │ -C2C88 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2C88: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2CA1 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2CA3   Length              0005 (5)
│ │ │ │ -C2CA5   Flags               01 (1) 'Modification'
│ │ │ │ -C2CA6   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2CAA Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2CAC   Length              000B (11)
│ │ │ │ -C2CAE   Version             01 (1)
│ │ │ │ -C2CAF   UID Size            04 (4)
│ │ │ │ -C2CB0   UID                 00000000 (0)
│ │ │ │ -C2CB4   GID Size            04 (4)
│ │ │ │ -C2CB5   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2CB9 CENTRAL HEADER #16    02014B50 (33639248)
│ │ │ │ -C2CBD Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2CBE Created OS            03 (3) 'Unix'
│ │ │ │ -C2CBF Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2CC0 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2CC1 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2CC3 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2CC5 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2CC9 CRC                   36D4AE72 (919907954)
│ │ │ │ -C2CCD Compressed Size       00001219 (4633)
│ │ │ │ -C2CD1 Uncompressed Size     00003C91 (15505)
│ │ │ │ -C2CD5 Filename Length       0010 (16)
│ │ │ │ -C2CD7 Extra Length          0018 (24)
│ │ │ │ -C2CD9 Comment Length        0000 (0)
│ │ │ │ -C2CDB Disk Start            0000 (0)
│ │ │ │ -C2CDD Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2CDF Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2CE3 Local Header Offset   0002E707 (190215)
│ │ │ │ -C2CE7 Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2CE7: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2CF7 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2CF9   Length              0005 (5)
│ │ │ │ -C2CFB   Flags               01 (1) 'Modification'
│ │ │ │ -C2CFC   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2D00 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2D02   Length              000B (11)
│ │ │ │ -C2D04   Version             01 (1)
│ │ │ │ -C2D05   UID Size            04 (4)
│ │ │ │ -C2D06   UID                 00000000 (0)
│ │ │ │ -C2D0A   GID Size            04 (4)
│ │ │ │ -C2D0B   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2D0F CENTRAL HEADER #17    02014B50 (33639248)
│ │ │ │ -C2D13 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2D14 Created OS            03 (3) 'Unix'
│ │ │ │ -C2D15 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2D16 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2D17 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2D19 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2D1B Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2D1F CRC                   0BA4F9CD (195361229)
│ │ │ │ -C2D23 Compressed Size       00002A5F (10847)
│ │ │ │ -C2D27 Uncompressed Size     000113A7 (70567)
│ │ │ │ -C2D2B Filename Length       0016 (22)
│ │ │ │ -C2D2D Extra Length          0018 (24)
│ │ │ │ -C2D2F Comment Length        0000 (0)
│ │ │ │ -C2D31 Disk Start            0000 (0)
│ │ │ │ -C2D33 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2D35 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2D39 Local Header Offset   0002F96A (194922)
│ │ │ │ -C2D3D Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2D3D: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2D53 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2D55   Length              0005 (5)
│ │ │ │ -C2D57   Flags               01 (1) 'Modification'
│ │ │ │ -C2D58   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2D5C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2D5E   Length              000B (11)
│ │ │ │ -C2D60   Version             01 (1)
│ │ │ │ -C2D61   UID Size            04 (4)
│ │ │ │ -C2D62   UID                 00000000 (0)
│ │ │ │ -C2D66   GID Size            04 (4)
│ │ │ │ -C2D67   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2D6B CENTRAL HEADER #18    02014B50 (33639248)
│ │ │ │ -C2D6F Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2D70 Created OS            03 (3) 'Unix'
│ │ │ │ -C2D71 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2D72 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2D73 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2D75 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2D77 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2D7B CRC                   AF0A8C6F (2936704111)
│ │ │ │ -C2D7F Compressed Size       000014D9 (5337)
│ │ │ │ -C2D83 Uncompressed Size     0000518D (20877)
│ │ │ │ -C2D87 Filename Length       001D (29)
│ │ │ │ -C2D89 Extra Length          0018 (24)
│ │ │ │ -C2D8B Comment Length        0000 (0)
│ │ │ │ -C2D8D Disk Start            0000 (0)
│ │ │ │ -C2D8F Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2D91 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2D95 Local Header Offset   00032419 (205849)
│ │ │ │ -C2D99 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2D99: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2DB6 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2DB8   Length              0005 (5)
│ │ │ │ -C2DBA   Flags               01 (1) 'Modification'
│ │ │ │ -C2DBB   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2DBF Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2DC1   Length              000B (11)
│ │ │ │ -C2DC3   Version             01 (1)
│ │ │ │ -C2DC4   UID Size            04 (4)
│ │ │ │ -C2DC5   UID                 00000000 (0)
│ │ │ │ -C2DC9   GID Size            04 (4)
│ │ │ │ -C2DCA   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2DCE CENTRAL HEADER #19    02014B50 (33639248)
│ │ │ │ -C2DD2 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2DD3 Created OS            03 (3) 'Unix'
│ │ │ │ -C2DD4 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2DD5 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2DD6 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2DD8 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2DDA Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2DDE CRC                   0B59709A (190410906)
│ │ │ │ -C2DE2 Compressed Size       000037FF (14335)
│ │ │ │ -C2DE6 Uncompressed Size     0000EA4B (59979)
│ │ │ │ -C2DEA Filename Length       001C (28)
│ │ │ │ -C2DEC Extra Length          0018 (24)
│ │ │ │ -C2DEE Comment Length        0000 (0)
│ │ │ │ -C2DF0 Disk Start            0000 (0)
│ │ │ │ -C2DF2 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2DF4 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2DF8 Local Header Offset   00033949 (211273)
│ │ │ │ -C2DFC Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2DFC: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2E18 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2E1A   Length              0005 (5)
│ │ │ │ -C2E1C   Flags               01 (1) 'Modification'
│ │ │ │ -C2E1D   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2E21 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2E23   Length              000B (11)
│ │ │ │ -C2E25   Version             01 (1)
│ │ │ │ -C2E26   UID Size            04 (4)
│ │ │ │ -C2E27   UID                 00000000 (0)
│ │ │ │ -C2E2B   GID Size            04 (4)
│ │ │ │ -C2E2C   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2E30 CENTRAL HEADER #20    02014B50 (33639248)
│ │ │ │ -C2E34 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2E35 Created OS            03 (3) 'Unix'
│ │ │ │ -C2E36 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2E37 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2E38 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2E3A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2E3C Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2E40 CRC                   958EC234 (2509161012)
│ │ │ │ -C2E44 Compressed Size       0000069E (1694)
│ │ │ │ -C2E48 Uncompressed Size     000011F3 (4595)
│ │ │ │ -C2E4C Filename Length       001C (28)
│ │ │ │ -C2E4E Extra Length          0018 (24)
│ │ │ │ -C2E50 Comment Length        0000 (0)
│ │ │ │ -C2E52 Disk Start            0000 (0)
│ │ │ │ -C2E54 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2E56 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2E5A Local Header Offset   0003719E (225694)
│ │ │ │ -C2E5E Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2E5E: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2E7A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2E7C   Length              0005 (5)
│ │ │ │ -C2E7E   Flags               01 (1) 'Modification'
│ │ │ │ -C2E7F   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2E83 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2E85   Length              000B (11)
│ │ │ │ -C2E87   Version             01 (1)
│ │ │ │ -C2E88   UID Size            04 (4)
│ │ │ │ -C2E89   UID                 00000000 (0)
│ │ │ │ -C2E8D   GID Size            04 (4)
│ │ │ │ -C2E8E   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2E92 CENTRAL HEADER #21    02014B50 (33639248)
│ │ │ │ -C2E96 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2E97 Created OS            03 (3) 'Unix'
│ │ │ │ -C2E98 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2E99 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2E9A General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2E9C Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2E9E Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2EA2 CRC                   42501F7E (1112547198)
│ │ │ │ -C2EA6 Compressed Size       0000107D (4221)
│ │ │ │ -C2EAA Uncompressed Size     00004BFE (19454)
│ │ │ │ -C2EAE Filename Length       001B (27)
│ │ │ │ -C2EB0 Extra Length          0018 (24)
│ │ │ │ -C2EB2 Comment Length        0000 (0)
│ │ │ │ -C2EB4 Disk Start            0000 (0)
│ │ │ │ -C2EB6 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2EB8 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2EBC Local Header Offset   00037892 (227474)
│ │ │ │ -C2EC0 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2EC0: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2EDB Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2EDD   Length              0005 (5)
│ │ │ │ -C2EDF   Flags               01 (1) 'Modification'
│ │ │ │ -C2EE0   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2EE4 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2EE6   Length              000B (11)
│ │ │ │ -C2EE8   Version             01 (1)
│ │ │ │ -C2EE9   UID Size            04 (4)
│ │ │ │ -C2EEA   UID                 00000000 (0)
│ │ │ │ -C2EEE   GID Size            04 (4)
│ │ │ │ -C2EEF   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2EF3 CENTRAL HEADER #22    02014B50 (33639248)
│ │ │ │ -C2EF7 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2EF8 Created OS            03 (3) 'Unix'
│ │ │ │ -C2EF9 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2EFA Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2EFB General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2EFD Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2EFF Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2F03 CRC                   3D4A57FE (1028282366)
│ │ │ │ -C2F07 Compressed Size       00003B3B (15163)
│ │ │ │ -C2F0B Uncompressed Size     0000D491 (54417)
│ │ │ │ -C2F0F Filename Length       001D (29)
│ │ │ │ -C2F11 Extra Length          0018 (24)
│ │ │ │ -C2F13 Comment Length        0000 (0)
│ │ │ │ -C2F15 Disk Start            0000 (0)
│ │ │ │ -C2F17 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2F19 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2F1D Local Header Offset   00038964 (231780)
│ │ │ │ -C2F21 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2F21: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2F3E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2F40   Length              0005 (5)
│ │ │ │ -C2F42   Flags               01 (1) 'Modification'
│ │ │ │ -C2F43   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2F47 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2F49   Length              000B (11)
│ │ │ │ -C2F4B   Version             01 (1)
│ │ │ │ -C2F4C   UID Size            04 (4)
│ │ │ │ -C2F4D   UID                 00000000 (0)
│ │ │ │ -C2F51   GID Size            04 (4)
│ │ │ │ -C2F52   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2F56 CENTRAL HEADER #23    02014B50 (33639248)
│ │ │ │ -C2F5A Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2F5B Created OS            03 (3) 'Unix'
│ │ │ │ -C2F5C Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2F5D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2F5E General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2F60 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2F62 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2F66 CRC                   76464E51 (1984319057)
│ │ │ │ -C2F6A Compressed Size       00000D6B (3435)
│ │ │ │ -C2F6E Uncompressed Size     0000388A (14474)
│ │ │ │ -C2F72 Filename Length       001D (29)
│ │ │ │ -C2F74 Extra Length          0018 (24)
│ │ │ │ -C2F76 Comment Length        0000 (0)
│ │ │ │ -C2F78 Disk Start            0000 (0)
│ │ │ │ -C2F7A Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2F7C Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2F80 Local Header Offset   0003C4F6 (247030)
│ │ │ │ -C2F84 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2F84: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C2FA1 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C2FA3   Length              0005 (5)
│ │ │ │ -C2FA5   Flags               01 (1) 'Modification'
│ │ │ │ -C2FA6   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C2FAA Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C2FAC   Length              000B (11)
│ │ │ │ -C2FAE   Version             01 (1)
│ │ │ │ -C2FAF   UID Size            04 (4)
│ │ │ │ -C2FB0   UID                 00000000 (0)
│ │ │ │ -C2FB4   GID Size            04 (4)
│ │ │ │ -C2FB5   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C2FB9 CENTRAL HEADER #24    02014B50 (33639248)
│ │ │ │ -C2FBD Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C2FBE Created OS            03 (3) 'Unix'
│ │ │ │ -C2FBF Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C2FC0 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C2FC1 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C2FC3 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C2FC5 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C2FC9 CRC                   50EF047D (1357841533)
│ │ │ │ -C2FCD Compressed Size       00001C86 (7302)
│ │ │ │ -C2FD1 Uncompressed Size     0000C038 (49208)
│ │ │ │ -C2FD5 Filename Length       001A (26)
│ │ │ │ -C2FD7 Extra Length          0018 (24)
│ │ │ │ -C2FD9 Comment Length        0000 (0)
│ │ │ │ -C2FDB Disk Start            0000 (0)
│ │ │ │ -C2FDD Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C2FDF Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C2FE3 Local Header Offset   0003D2B8 (250552)
│ │ │ │ -C2FE7 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC2FE7: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3001 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3003   Length              0005 (5)
│ │ │ │ -C3005   Flags               01 (1) 'Modification'
│ │ │ │ -C3006   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C300A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C300C   Length              000B (11)
│ │ │ │ -C300E   Version             01 (1)
│ │ │ │ -C300F   UID Size            04 (4)
│ │ │ │ -C3010   UID                 00000000 (0)
│ │ │ │ -C3014   GID Size            04 (4)
│ │ │ │ -C3015   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3019 CENTRAL HEADER #25    02014B50 (33639248)
│ │ │ │ -C301D Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C301E Created OS            03 (3) 'Unix'
│ │ │ │ -C301F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3020 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3021 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3023 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3025 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C3029 CRC                   478B6B96 (1200319382)
│ │ │ │ -C302D Compressed Size       000003DF (991)
│ │ │ │ -C3031 Uncompressed Size     00000935 (2357)
│ │ │ │ -C3035 Filename Length       0012 (18)
│ │ │ │ -C3037 Extra Length          0018 (24)
│ │ │ │ -C3039 Comment Length        0000 (0)
│ │ │ │ -C303B Disk Start            0000 (0)
│ │ │ │ -C303D Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C303F Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3043 Local Header Offset   0003EF92 (257938)
│ │ │ │ -C3047 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3047: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3059 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C305B   Length              0005 (5)
│ │ │ │ -C305D   Flags               01 (1) 'Modification'
│ │ │ │ -C305E   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C3062 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3064   Length              000B (11)
│ │ │ │ -C3066   Version             01 (1)
│ │ │ │ -C3067   UID Size            04 (4)
│ │ │ │ -C3068   UID                 00000000 (0)
│ │ │ │ -C306C   GID Size            04 (4)
│ │ │ │ -C306D   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3071 CENTRAL HEADER #26    02014B50 (33639248)
│ │ │ │ -C3075 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3076 Created OS            03 (3) 'Unix'
│ │ │ │ -C3077 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3078 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3079 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C307B Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C307D Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C3081 CRC                   E79489F0 (3885271536)
│ │ │ │ -C3085 Compressed Size       000001D3 (467)
│ │ │ │ -C3089 Uncompressed Size     00000311 (785)
│ │ │ │ -C308D Filename Length       0020 (32)
│ │ │ │ -C308F Extra Length          0018 (24)
│ │ │ │ -C3091 Comment Length        0000 (0)
│ │ │ │ -C3093 Disk Start            0000 (0)
│ │ │ │ -C3095 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3097 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C309B Local Header Offset   0003F3BD (259005)
│ │ │ │ -C309F Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC309F: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C30BF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C30C1   Length              0005 (5)
│ │ │ │ -C30C3   Flags               01 (1) 'Modification'
│ │ │ │ -C30C4   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C30C8 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C30CA   Length              000B (11)
│ │ │ │ -C30CC   Version             01 (1)
│ │ │ │ -C30CD   UID Size            04 (4)
│ │ │ │ -C30CE   UID                 00000000 (0)
│ │ │ │ -C30D2   GID Size            04 (4)
│ │ │ │ -C30D3   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C30D7 CENTRAL HEADER #27    02014B50 (33639248)
│ │ │ │ -C30DB Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C30DC Created OS            03 (3) 'Unix'
│ │ │ │ -C30DD Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C30DE Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C30DF General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C30E1 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C30E3 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C30E7 CRC                   BB37392E (3140958510)
│ │ │ │ -C30EB Compressed Size       000017AE (6062)
│ │ │ │ -C30EF Uncompressed Size     00009D1B (40219)
│ │ │ │ -C30F3 Filename Length       001B (27)
│ │ │ │ -C30F5 Extra Length          0018 (24)
│ │ │ │ -C30F7 Comment Length        0000 (0)
│ │ │ │ -C30F9 Disk Start            0000 (0)
│ │ │ │ -C30FB Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C30FD Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3101 Local Header Offset   0003F5EA (259562)
│ │ │ │ -C3105 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3105: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3120 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3122   Length              0005 (5)
│ │ │ │ -C3124   Flags               01 (1) 'Modification'
│ │ │ │ -C3125   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C3129 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C312B   Length              000B (11)
│ │ │ │ -C312D   Version             01 (1)
│ │ │ │ -C312E   UID Size            04 (4)
│ │ │ │ -C312F   UID                 00000000 (0)
│ │ │ │ -C3133   GID Size            04 (4)
│ │ │ │ -C3134   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3138 CENTRAL HEADER #28    02014B50 (33639248)
│ │ │ │ -C313C Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C313D Created OS            03 (3) 'Unix'
│ │ │ │ -C313E Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C313F Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3140 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3142 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3144 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C3148 CRC                   09EB9A96 (166435478)
│ │ │ │ -C314C Compressed Size       0000136D (4973)
│ │ │ │ -C3150 Uncompressed Size     00003B58 (15192)
│ │ │ │ -C3154 Filename Length       0015 (21)
│ │ │ │ -C3156 Extra Length          0018 (24)
│ │ │ │ -C3158 Comment Length        0000 (0)
│ │ │ │ -C315A Disk Start            0000 (0)
│ │ │ │ -C315C Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C315E Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3162 Local Header Offset   00040DED (265709)
│ │ │ │ -C3166 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3166: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C317B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C317D   Length              0005 (5)
│ │ │ │ -C317F   Flags               01 (1) 'Modification'
│ │ │ │ -C3180   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C3184 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3186   Length              000B (11)
│ │ │ │ -C3188   Version             01 (1)
│ │ │ │ -C3189   UID Size            04 (4)
│ │ │ │ -C318A   UID                 00000000 (0)
│ │ │ │ -C318E   GID Size            04 (4)
│ │ │ │ -C318F   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3193 CENTRAL HEADER #29    02014B50 (33639248)
│ │ │ │ -C3197 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3198 Created OS            03 (3) 'Unix'
│ │ │ │ -C3199 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C319A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C319B General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C319D Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C319F Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C31A3 CRC                   F9EDEEDB (4193119963)
│ │ │ │ -C31A7 Compressed Size       00000AC9 (2761)
│ │ │ │ -C31AB Uncompressed Size     00002133 (8499)
│ │ │ │ -C31AF Filename Length       0011 (17)
│ │ │ │ -C31B1 Extra Length          0018 (24)
│ │ │ │ -C31B3 Comment Length        0000 (0)
│ │ │ │ -C31B5 Disk Start            0000 (0)
│ │ │ │ -C31B7 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C31B9 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C31BD Local Header Offset   000421A9 (270761)
│ │ │ │ -C31C1 Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC31C1: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C31D2 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C31D4   Length              0005 (5)
│ │ │ │ -C31D6   Flags               01 (1) 'Modification'
│ │ │ │ -C31D7   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C31DB Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C31DD   Length              000B (11)
│ │ │ │ -C31DF   Version             01 (1)
│ │ │ │ -C31E0   UID Size            04 (4)
│ │ │ │ -C31E1   UID                 00000000 (0)
│ │ │ │ -C31E5   GID Size            04 (4)
│ │ │ │ -C31E6   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C31EA CENTRAL HEADER #30    02014B50 (33639248)
│ │ │ │ -C31EE Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C31EF Created OS            03 (3) 'Unix'
│ │ │ │ -C31F0 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C31F1 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C31F2 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C31F4 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C31F6 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C31FA CRC                   061A4CFE (102386942)
│ │ │ │ -C31FE Compressed Size       000003FD (1021)
│ │ │ │ -C3202 Uncompressed Size     00000F0C (3852)
│ │ │ │ -C3206 Filename Length       0014 (20)
│ │ │ │ -C3208 Extra Length          0018 (24)
│ │ │ │ -C320A Comment Length        0000 (0)
│ │ │ │ -C320C Disk Start            0000 (0)
│ │ │ │ -C320E Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3210 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3214 Local Header Offset   00042CBD (273597)
│ │ │ │ -C3218 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3218: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C322C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C322E   Length              0005 (5)
│ │ │ │ -C3230   Flags               01 (1) 'Modification'
│ │ │ │ -C3231   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C3235 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3237   Length              000B (11)
│ │ │ │ -C3239   Version             01 (1)
│ │ │ │ -C323A   UID Size            04 (4)
│ │ │ │ -C323B   UID                 00000000 (0)
│ │ │ │ -C323F   GID Size            04 (4)
│ │ │ │ -C3240   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3244 CENTRAL HEADER #31    02014B50 (33639248)
│ │ │ │ -C3248 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3249 Created OS            03 (3) 'Unix'
│ │ │ │ -C324A Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C324B Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C324C General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C324E Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3250 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C3254 CRC                   3F5B0F93 (1062932371)
│ │ │ │ -C3258 Compressed Size       00001260 (4704)
│ │ │ │ -C325C Uncompressed Size     0000346B (13419)
│ │ │ │ -C3260 Filename Length       0014 (20)
│ │ │ │ -C3262 Extra Length          0018 (24)
│ │ │ │ -C3264 Comment Length        0000 (0)
│ │ │ │ -C3266 Disk Start            0000 (0)
│ │ │ │ -C3268 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C326A Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C326E Local Header Offset   00043108 (274696)
│ │ │ │ -C3272 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3272: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3286 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3288   Length              0005 (5)
│ │ │ │ -C328A   Flags               01 (1) 'Modification'
│ │ │ │ -C328B   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C328F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3291   Length              000B (11)
│ │ │ │ -C3293   Version             01 (1)
│ │ │ │ -C3294   UID Size            04 (4)
│ │ │ │ -C3295   UID                 00000000 (0)
│ │ │ │ -C3299   GID Size            04 (4)
│ │ │ │ -C329A   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C329E CENTRAL HEADER #32    02014B50 (33639248)
│ │ │ │ -C32A2 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C32A3 Created OS            03 (3) 'Unix'
│ │ │ │ -C32A4 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C32A5 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C32A6 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C32A8 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C32AA Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C32AE CRC                   41B13910 (1102133520)
│ │ │ │ -C32B2 Compressed Size       00000ACC (2764)
│ │ │ │ -C32B6 Uncompressed Size     000022FF (8959)
│ │ │ │ -C32BA Filename Length       001B (27)
│ │ │ │ -C32BC Extra Length          0018 (24)
│ │ │ │ -C32BE Comment Length        0000 (0)
│ │ │ │ -C32C0 Disk Start            0000 (0)
│ │ │ │ -C32C2 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C32C4 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C32C8 Local Header Offset   000443B6 (279478)
│ │ │ │ -C32CC Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC32CC: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C32E7 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C32E9   Length              0005 (5)
│ │ │ │ -C32EB   Flags               01 (1) 'Modification'
│ │ │ │ -C32EC   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C32F0 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C32F2   Length              000B (11)
│ │ │ │ -C32F4   Version             01 (1)
│ │ │ │ -C32F5   UID Size            04 (4)
│ │ │ │ -C32F6   UID                 00000000 (0)
│ │ │ │ -C32FA   GID Size            04 (4)
│ │ │ │ -C32FB   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C32FF CENTRAL HEADER #33    02014B50 (33639248)
│ │ │ │ -C3303 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3304 Created OS            03 (3) 'Unix'
│ │ │ │ -C3305 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3306 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3307 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3309 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C330B Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C330F CRC                   DB2E23B4 (3677234100)
│ │ │ │ -C3313 Compressed Size       00000C51 (3153)
│ │ │ │ -C3317 Uncompressed Size     00002742 (10050)
│ │ │ │ -C331B Filename Length       0013 (19)
│ │ │ │ -C331D Extra Length          0018 (24)
│ │ │ │ -C331F Comment Length        0000 (0)
│ │ │ │ -C3321 Disk Start            0000 (0)
│ │ │ │ -C3323 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3325 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3329 Local Header Offset   00044ED7 (282327)
│ │ │ │ -C332D Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC332D: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3340 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3342   Length              0005 (5)
│ │ │ │ -C3344   Flags               01 (1) 'Modification'
│ │ │ │ -C3345   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C3349 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C334B   Length              000B (11)
│ │ │ │ -C334D   Version             01 (1)
│ │ │ │ -C334E   UID Size            04 (4)
│ │ │ │ -C334F   UID                 00000000 (0)
│ │ │ │ -C3353   GID Size            04 (4)
│ │ │ │ -C3354   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3358 CENTRAL HEADER #34    02014B50 (33639248)
│ │ │ │ -C335C Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C335D Created OS            03 (3) 'Unix'
│ │ │ │ -C335E Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C335F Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3360 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3362 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3364 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C3368 CRC                   0705BEAC (117817004)
│ │ │ │ -C336C Compressed Size       00000C95 (3221)
│ │ │ │ -C3370 Uncompressed Size     00003D11 (15633)
│ │ │ │ -C3374 Filename Length       0014 (20)
│ │ │ │ -C3376 Extra Length          0018 (24)
│ │ │ │ -C3378 Comment Length        0000 (0)
│ │ │ │ -C337A Disk Start            0000 (0)
│ │ │ │ -C337C Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C337E Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3382 Local Header Offset   00045B75 (285557)
│ │ │ │ -C3386 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3386: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C339A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C339C   Length              0005 (5)
│ │ │ │ -C339E   Flags               01 (1) 'Modification'
│ │ │ │ -C339F   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C33A3 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C33A5   Length              000B (11)
│ │ │ │ -C33A7   Version             01 (1)
│ │ │ │ -C33A8   UID Size            04 (4)
│ │ │ │ -C33A9   UID                 00000000 (0)
│ │ │ │ -C33AD   GID Size            04 (4)
│ │ │ │ -C33AE   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C33B2 CENTRAL HEADER #35    02014B50 (33639248)
│ │ │ │ -C33B6 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C33B7 Created OS            03 (3) 'Unix'
│ │ │ │ -C33B8 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C33B9 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C33BA General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C33BC Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C33BE Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C33C2 CRC                   356E7AD6 (896432854)
│ │ │ │ -C33C6 Compressed Size       00000F43 (3907)
│ │ │ │ -C33CA Uncompressed Size     00003744 (14148)
│ │ │ │ -C33CE Filename Length       000F (15)
│ │ │ │ -C33D0 Extra Length          0018 (24)
│ │ │ │ -C33D2 Comment Length        0000 (0)
│ │ │ │ -C33D4 Disk Start            0000 (0)
│ │ │ │ -C33D6 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C33D8 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C33DC Local Header Offset   00046858 (288856)
│ │ │ │ -C33E0 Filename              'XXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC33E0: Filename 'XXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C33EF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C33F1   Length              0005 (5)
│ │ │ │ -C33F3   Flags               01 (1) 'Modification'
│ │ │ │ -C33F4   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C33F8 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C33FA   Length              000B (11)
│ │ │ │ -C33FC   Version             01 (1)
│ │ │ │ -C33FD   UID Size            04 (4)
│ │ │ │ -C33FE   UID                 00000000 (0)
│ │ │ │ -C3402   GID Size            04 (4)
│ │ │ │ -C3403   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3407 CENTRAL HEADER #36    02014B50 (33639248)
│ │ │ │ -C340B Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C340C Created OS            03 (3) 'Unix'
│ │ │ │ -C340D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C340E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C340F General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3411 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3413 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C3417 CRC                   AD08D6E7 (2903037671)
│ │ │ │ -C341B Compressed Size       000006CE (1742)
│ │ │ │ -C341F Uncompressed Size     00001AC4 (6852)
│ │ │ │ -C3423 Filename Length       000F (15)
│ │ │ │ -C3425 Extra Length          0018 (24)
│ │ │ │ -C3427 Comment Length        0000 (0)
│ │ │ │ -C3429 Disk Start            0000 (0)
│ │ │ │ -C342B Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C342D Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3431 Local Header Offset   000477E4 (292836)
│ │ │ │ -C3435 Filename              'XXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3435: Filename 'XXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3444 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3446   Length              0005 (5)
│ │ │ │ -C3448   Flags               01 (1) 'Modification'
│ │ │ │ -C3449   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C344D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C344F   Length              000B (11)
│ │ │ │ -C3451   Version             01 (1)
│ │ │ │ -C3452   UID Size            04 (4)
│ │ │ │ -C3453   UID                 00000000 (0)
│ │ │ │ -C3457   GID Size            04 (4)
│ │ │ │ -C3458   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C345C CENTRAL HEADER #37    02014B50 (33639248)
│ │ │ │ -C3460 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3461 Created OS            03 (3) 'Unix'
│ │ │ │ -C3462 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3463 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3464 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3466 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3468 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C346C CRC                   27AAA5BB (665494971)
│ │ │ │ -C3470 Compressed Size       00001A4F (6735)
│ │ │ │ -C3474 Uncompressed Size     0000650E (25870)
│ │ │ │ -C3478 Filename Length       0013 (19)
│ │ │ │ -C347A Extra Length          0018 (24)
│ │ │ │ -C347C Comment Length        0000 (0)
│ │ │ │ -C347E Disk Start            0000 (0)
│ │ │ │ -C3480 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3482 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3486 Local Header Offset   00047EFB (294651)
│ │ │ │ -C348A Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC348A: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C349D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C349F   Length              0005 (5)
│ │ │ │ -C34A1   Flags               01 (1) 'Modification'
│ │ │ │ -C34A2   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C34A6 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C34A8   Length              000B (11)
│ │ │ │ -C34AA   Version             01 (1)
│ │ │ │ -C34AB   UID Size            04 (4)
│ │ │ │ -C34AC   UID                 00000000 (0)
│ │ │ │ -C34B0   GID Size            04 (4)
│ │ │ │ -C34B1   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C34B5 CENTRAL HEADER #38    02014B50 (33639248)
│ │ │ │ -C34B9 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C34BA Created OS            03 (3) 'Unix'
│ │ │ │ -C34BB Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C34BC Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C34BD General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C34BF Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C34C1 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C34C5 CRC                   90967BFA (2425781242)
│ │ │ │ -C34C9 Compressed Size       000009A6 (2470)
│ │ │ │ -C34CD Uncompressed Size     00001B6A (7018)
│ │ │ │ -C34D1 Filename Length       0010 (16)
│ │ │ │ -C34D3 Extra Length          0018 (24)
│ │ │ │ -C34D5 Comment Length        0000 (0)
│ │ │ │ -C34D7 Disk Start            0000 (0)
│ │ │ │ -C34D9 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C34DB Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C34DF Local Header Offset   00049997 (301463)
│ │ │ │ -C34E3 Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC34E3: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C34F3 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C34F5   Length              0005 (5)
│ │ │ │ -C34F7   Flags               01 (1) 'Modification'
│ │ │ │ -C34F8   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C34FC Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C34FE   Length              000B (11)
│ │ │ │ -C3500   Version             01 (1)
│ │ │ │ -C3501   UID Size            04 (4)
│ │ │ │ -C3502   UID                 00000000 (0)
│ │ │ │ -C3506   GID Size            04 (4)
│ │ │ │ -C3507   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C350B CENTRAL HEADER #39    02014B50 (33639248)
│ │ │ │ -C350F Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3510 Created OS            03 (3) 'Unix'
│ │ │ │ -C3511 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3512 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3513 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3515 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3517 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C351B CRC                   D37ED789 (3548305289)
│ │ │ │ -C351F Compressed Size       000006B6 (1718)
│ │ │ │ -C3523 Uncompressed Size     00001565 (5477)
│ │ │ │ -C3527 Filename Length       0012 (18)
│ │ │ │ -C3529 Extra Length          0018 (24)
│ │ │ │ -C352B Comment Length        0000 (0)
│ │ │ │ -C352D Disk Start            0000 (0)
│ │ │ │ -C352F Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3531 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3535 Local Header Offset   0004A387 (304007)
│ │ │ │ -C3539 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3539: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C354B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C354D   Length              0005 (5)
│ │ │ │ -C354F   Flags               01 (1) 'Modification'
│ │ │ │ -C3550   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C3554 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3556   Length              000B (11)
│ │ │ │ -C3558   Version             01 (1)
│ │ │ │ -C3559   UID Size            04 (4)
│ │ │ │ -C355A   UID                 00000000 (0)
│ │ │ │ -C355E   GID Size            04 (4)
│ │ │ │ -C355F   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3563 CENTRAL HEADER #40    02014B50 (33639248)
│ │ │ │ -C3567 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3568 Created OS            03 (3) 'Unix'
│ │ │ │ -C3569 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C356A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C356B General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C356D Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C356F Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C3573 CRC                   92D091A2 (2463142306)
│ │ │ │ -C3577 Compressed Size       00002D59 (11609)
│ │ │ │ -C357B Uncompressed Size     0000D083 (53379)
│ │ │ │ -C357F Filename Length       0010 (16)
│ │ │ │ -C3581 Extra Length          0018 (24)
│ │ │ │ -C3583 Comment Length        0000 (0)
│ │ │ │ -C3585 Disk Start            0000 (0)
│ │ │ │ -C3587 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3589 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C358D Local Header Offset   0004AA89 (305801)
│ │ │ │ -C3591 Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3591: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C35A1 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C35A3   Length              0005 (5)
│ │ │ │ -C35A5   Flags               01 (1) 'Modification'
│ │ │ │ -C35A6   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C35AA Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C35AC   Length              000B (11)
│ │ │ │ -C35AE   Version             01 (1)
│ │ │ │ -C35AF   UID Size            04 (4)
│ │ │ │ -C35B0   UID                 00000000 (0)
│ │ │ │ -C35B4   GID Size            04 (4)
│ │ │ │ -C35B5   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C35B9 CENTRAL HEADER #41    02014B50 (33639248)
│ │ │ │ -C35BD Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C35BE Created OS            03 (3) 'Unix'
│ │ │ │ -C35BF Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C35C0 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C35C1 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C35C3 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C35C5 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C35C9 CRC                   608FA1E3 (1620025827)
│ │ │ │ -C35CD Compressed Size       00001E84 (7812)
│ │ │ │ -C35D1 Uncompressed Size     00009AAA (39594)
│ │ │ │ -C35D5 Filename Length       0012 (18)
│ │ │ │ -C35D7 Extra Length          0018 (24)
│ │ │ │ -C35D9 Comment Length        0000 (0)
│ │ │ │ -C35DB Disk Start            0000 (0)
│ │ │ │ -C35DD Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C35DF Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C35E3 Local Header Offset   0004D82C (317484)
│ │ │ │ -C35E7 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC35E7: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C35F9 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C35FB   Length              0005 (5)
│ │ │ │ -C35FD   Flags               01 (1) 'Modification'
│ │ │ │ -C35FE   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C3602 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3604   Length              000B (11)
│ │ │ │ -C3606   Version             01 (1)
│ │ │ │ -C3607   UID Size            04 (4)
│ │ │ │ -C3608   UID                 00000000 (0)
│ │ │ │ -C360C   GID Size            04 (4)
│ │ │ │ -C360D   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3611 CENTRAL HEADER #42    02014B50 (33639248)
│ │ │ │ -C3615 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3616 Created OS            03 (3) 'Unix'
│ │ │ │ -C3617 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3618 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3619 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C361B Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C361D Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C3621 CRC                   69109545 (1762694469)
│ │ │ │ -C3625 Compressed Size       00001471 (5233)
│ │ │ │ -C3629 Uncompressed Size     00007AD0 (31440)
│ │ │ │ -C362D Filename Length       0018 (24)
│ │ │ │ -C362F Extra Length          0018 (24)
│ │ │ │ -C3631 Comment Length        0000 (0)
│ │ │ │ -C3633 Disk Start            0000 (0)
│ │ │ │ -C3635 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3637 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C363B Local Header Offset   0004F6FC (325372)
│ │ │ │ -C363F Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC363F: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3657 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3659   Length              0005 (5)
│ │ │ │ -C365B   Flags               01 (1) 'Modification'
│ │ │ │ -C365C   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C3660 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3662   Length              000B (11)
│ │ │ │ -C3664   Version             01 (1)
│ │ │ │ -C3665   UID Size            04 (4)
│ │ │ │ -C3666   UID                 00000000 (0)
│ │ │ │ -C366A   GID Size            04 (4)
│ │ │ │ -C366B   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C366F CENTRAL HEADER #43    02014B50 (33639248)
│ │ │ │ -C3673 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3674 Created OS            03 (3) 'Unix'
│ │ │ │ -C3675 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3676 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3677 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3679 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C367B Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C367F CRC                   274FF23B (659550779)
│ │ │ │ -C3683 Compressed Size       000021DB (8667)
│ │ │ │ -C3687 Uncompressed Size     0000D21D (53789)
│ │ │ │ -C368B Filename Length       001F (31)
│ │ │ │ -C368D Extra Length          0018 (24)
│ │ │ │ -C368F Comment Length        0000 (0)
│ │ │ │ -C3691 Disk Start            0000 (0)
│ │ │ │ -C3693 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3695 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3699 Local Header Offset   00050BBF (330687)
│ │ │ │ -C369D Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC369D: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C36BC Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C36BE   Length              0005 (5)
│ │ │ │ -C36C0   Flags               01 (1) 'Modification'
│ │ │ │ -C36C1   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C36C5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C36C7   Length              000B (11)
│ │ │ │ -C36C9   Version             01 (1)
│ │ │ │ -C36CA   UID Size            04 (4)
│ │ │ │ -C36CB   UID                 00000000 (0)
│ │ │ │ -C36CF   GID Size            04 (4)
│ │ │ │ -C36D0   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C36D4 CENTRAL HEADER #44    02014B50 (33639248)
│ │ │ │ -C36D8 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C36D9 Created OS            03 (3) 'Unix'
│ │ │ │ -C36DA Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C36DB Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C36DC General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C36DE Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C36E0 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C36E4 CRC                   585AC976 (1482344822)
│ │ │ │ -C36E8 Compressed Size       000003F7 (1015)
│ │ │ │ -C36EC Uncompressed Size     000008A3 (2211)
│ │ │ │ -C36F0 Filename Length       001E (30)
│ │ │ │ -C36F2 Extra Length          0018 (24)
│ │ │ │ -C36F4 Comment Length        0000 (0)
│ │ │ │ -C36F6 Disk Start            0000 (0)
│ │ │ │ -C36F8 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C36FA Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C36FE Local Header Offset   00052DF3 (339443)
│ │ │ │ -C3702 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3702: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3720 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3722   Length              0005 (5)
│ │ │ │ -C3724   Flags               01 (1) 'Modification'
│ │ │ │ -C3725   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C3729 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C372B   Length              000B (11)
│ │ │ │ -C372D   Version             01 (1)
│ │ │ │ -C372E   UID Size            04 (4)
│ │ │ │ -C372F   UID                 00000000 (0)
│ │ │ │ -C3733   GID Size            04 (4)
│ │ │ │ -C3734   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3738 CENTRAL HEADER #45    02014B50 (33639248)
│ │ │ │ -C373C Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C373D Created OS            03 (3) 'Unix'
│ │ │ │ -C373E Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C373F Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3740 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3742 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3744 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C3748 CRC                   16308EDA (372281050)
│ │ │ │ -C374C Compressed Size       00004361 (17249)
│ │ │ │ -C3750 Uncompressed Size     0000E06F (57455)
│ │ │ │ -C3754 Filename Length       0013 (19)
│ │ │ │ -C3756 Extra Length          0018 (24)
│ │ │ │ -C3758 Comment Length        0000 (0)
│ │ │ │ -C375A Disk Start            0000 (0)
│ │ │ │ -C375C Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C375E Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3762 Local Header Offset   00053242 (340546)
│ │ │ │ -C3766 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3766: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3779 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C377B   Length              0005 (5)
│ │ │ │ -C377D   Flags               01 (1) 'Modification'
│ │ │ │ -C377E   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C3782 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3784   Length              000B (11)
│ │ │ │ -C3786   Version             01 (1)
│ │ │ │ -C3787   UID Size            04 (4)
│ │ │ │ -C3788   UID                 00000000 (0)
│ │ │ │ -C378C   GID Size            04 (4)
│ │ │ │ -C378D   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3791 CENTRAL HEADER #46    02014B50 (33639248)
│ │ │ │ -C3795 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3796 Created OS            03 (3) 'Unix'
│ │ │ │ -C3797 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3798 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3799 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C379B Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C379D Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C37A1 CRC                   741EF03C (1948184636)
│ │ │ │ -C37A5 Compressed Size       000026C3 (9923)
│ │ │ │ -C37A9 Uncompressed Size     00006E45 (28229)
│ │ │ │ -C37AD Filename Length       0019 (25)
│ │ │ │ -C37AF Extra Length          0018 (24)
│ │ │ │ -C37B1 Comment Length        0000 (0)
│ │ │ │ -C37B3 Disk Start            0000 (0)
│ │ │ │ -C37B5 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C37B7 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C37BB Local Header Offset   000575F0 (357872)
│ │ │ │ -C37BF Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC37BF: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C37D8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C37DA   Length              0005 (5)
│ │ │ │ -C37DC   Flags               01 (1) 'Modification'
│ │ │ │ -C37DD   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C37E1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C37E3   Length              000B (11)
│ │ │ │ -C37E5   Version             01 (1)
│ │ │ │ -C37E6   UID Size            04 (4)
│ │ │ │ -C37E7   UID                 00000000 (0)
│ │ │ │ -C37EB   GID Size            04 (4)
│ │ │ │ -C37EC   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C37F0 CENTRAL HEADER #47    02014B50 (33639248)
│ │ │ │ -C37F4 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C37F5 Created OS            03 (3) 'Unix'
│ │ │ │ -C37F6 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C37F7 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C37F8 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C37FA Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C37FC Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C3800 CRC                   F8618863 (4167141475)
│ │ │ │ -C3804 Compressed Size       00002738 (10040)
│ │ │ │ -C3808 Uncompressed Size     00008B83 (35715)
│ │ │ │ -C380C Filename Length       0019 (25)
│ │ │ │ -C380E Extra Length          0018 (24)
│ │ │ │ -C3810 Comment Length        0000 (0)
│ │ │ │ -C3812 Disk Start            0000 (0)
│ │ │ │ -C3814 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3816 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C381A Local Header Offset   00059D06 (367878)
│ │ │ │ -C381E Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC381E: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3837 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3839   Length              0005 (5)
│ │ │ │ -C383B   Flags               01 (1) 'Modification'
│ │ │ │ -C383C   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C3840 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3842   Length              000B (11)
│ │ │ │ -C3844   Version             01 (1)
│ │ │ │ -C3845   UID Size            04 (4)
│ │ │ │ -C3846   UID                 00000000 (0)
│ │ │ │ -C384A   GID Size            04 (4)
│ │ │ │ -C384B   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C384F CENTRAL HEADER #48    02014B50 (33639248)
│ │ │ │ -C3853 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3854 Created OS            03 (3) 'Unix'
│ │ │ │ -C3855 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3856 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3857 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3859 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C385B Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C385F CRC                   50018C09 (1342278665)
│ │ │ │ -C3863 Compressed Size       00000ECF (3791)
│ │ │ │ -C3867 Uncompressed Size     000053BF (21439)
│ │ │ │ -C386B Filename Length       0021 (33)
│ │ │ │ -C386D Extra Length          0018 (24)
│ │ │ │ -C386F Comment Length        0000 (0)
│ │ │ │ -C3871 Disk Start            0000 (0)
│ │ │ │ -C3873 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3875 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3879 Local Header Offset   0005C491 (378001)
│ │ │ │ -C387D Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC387D: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C389E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C38A0   Length              0005 (5)
│ │ │ │ -C38A2   Flags               01 (1) 'Modification'
│ │ │ │ -C38A3   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C38A7 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C38A9   Length              000B (11)
│ │ │ │ -C38AB   Version             01 (1)
│ │ │ │ -C38AC   UID Size            04 (4)
│ │ │ │ -C38AD   UID                 00000000 (0)
│ │ │ │ -C38B1   GID Size            04 (4)
│ │ │ │ -C38B2   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C38B6 CENTRAL HEADER #49    02014B50 (33639248)
│ │ │ │ -C38BA Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C38BB Created OS            03 (3) 'Unix'
│ │ │ │ -C38BC Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C38BD Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C38BE General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C38C0 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C38C2 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C38C6 CRC                   D1EC3113 (3521917203)
│ │ │ │ -C38CA Compressed Size       00000535 (1333)
│ │ │ │ -C38CE Uncompressed Size     00000C96 (3222)
│ │ │ │ -C38D2 Filename Length       0017 (23)
│ │ │ │ -C38D4 Extra Length          0018 (24)
│ │ │ │ -C38D6 Comment Length        0000 (0)
│ │ │ │ -C38D8 Disk Start            0000 (0)
│ │ │ │ -C38DA Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C38DC Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C38E0 Local Header Offset   0005D3BB (381883)
│ │ │ │ -C38E4 Filename              'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC38E4: Filename 'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C38FB Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C38FD   Length              0005 (5)
│ │ │ │ -C38FF   Flags               01 (1) 'Modification'
│ │ │ │ -C3900   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C3904 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3906   Length              000B (11)
│ │ │ │ -C3908   Version             01 (1)
│ │ │ │ -C3909   UID Size            04 (4)
│ │ │ │ -C390A   UID                 00000000 (0)
│ │ │ │ -C390E   GID Size            04 (4)
│ │ │ │ -C390F   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3913 CENTRAL HEADER #50    02014B50 (33639248)
│ │ │ │ -C3917 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3918 Created OS            03 (3) 'Unix'
│ │ │ │ -C3919 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C391A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C391B General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C391D Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C391F Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C3923 CRC                   9ED6F2D9 (2664887001)
│ │ │ │ -C3927 Compressed Size       00000467 (1127)
│ │ │ │ -C392B Uncompressed Size     00000931 (2353)
│ │ │ │ -C392F Filename Length       001B (27)
│ │ │ │ -C3931 Extra Length          0018 (24)
│ │ │ │ -C3933 Comment Length        0000 (0)
│ │ │ │ -C3935 Disk Start            0000 (0)
│ │ │ │ -C3937 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3939 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C393D Local Header Offset   0005D941 (383297)
│ │ │ │ -C3941 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3941: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C395C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C395E   Length              0005 (5)
│ │ │ │ -C3960   Flags               01 (1) 'Modification'
│ │ │ │ -C3961   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C3965 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3967   Length              000B (11)
│ │ │ │ -C3969   Version             01 (1)
│ │ │ │ -C396A   UID Size            04 (4)
│ │ │ │ -C396B   UID                 00000000 (0)
│ │ │ │ -C396F   GID Size            04 (4)
│ │ │ │ -C3970   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3974 CENTRAL HEADER #51    02014B50 (33639248)
│ │ │ │ -C3978 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3979 Created OS            03 (3) 'Unix'
│ │ │ │ -C397A Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C397B Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C397C General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C397E Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3980 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C3984 CRC                   BA8B93BA (3129709498)
│ │ │ │ -C3988 Compressed Size       000016F5 (5877)
│ │ │ │ -C398C Uncompressed Size     00007A86 (31366)
│ │ │ │ -C3990 Filename Length       001F (31)
│ │ │ │ -C3992 Extra Length          0018 (24)
│ │ │ │ -C3994 Comment Length        0000 (0)
│ │ │ │ -C3996 Disk Start            0000 (0)
│ │ │ │ -C3998 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C399A Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C399E Local Header Offset   0005DDFD (384509)
│ │ │ │ -C39A2 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC39A2: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C39C1 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C39C3   Length              0005 (5)
│ │ │ │ -C39C5   Flags               01 (1) 'Modification'
│ │ │ │ -C39C6   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C39CA Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C39CC   Length              000B (11)
│ │ │ │ -C39CE   Version             01 (1)
│ │ │ │ -C39CF   UID Size            04 (4)
│ │ │ │ -C39D0   UID                 00000000 (0)
│ │ │ │ -C39D4   GID Size            04 (4)
│ │ │ │ -C39D5   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C39D9 CENTRAL HEADER #52    02014B50 (33639248)
│ │ │ │ -C39DD Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C39DE Created OS            03 (3) 'Unix'
│ │ │ │ -C39DF Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C39E0 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C39E1 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C39E3 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C39E5 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C39E9 CRC                   7113BB88 (1897118600)
│ │ │ │ -C39ED Compressed Size       00004171 (16753)
│ │ │ │ -C39F1 Uncompressed Size     0001D163 (119139)
│ │ │ │ -C39F5 Filename Length       0010 (16)
│ │ │ │ -C39F7 Extra Length          0018 (24)
│ │ │ │ -C39F9 Comment Length        0000 (0)
│ │ │ │ -C39FB Disk Start            0000 (0)
│ │ │ │ -C39FD Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C39FF Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3A03 Local Header Offset   0005F54B (390475)
│ │ │ │ -C3A07 Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3A07: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3A17 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3A19   Length              0005 (5)
│ │ │ │ -C3A1B   Flags               01 (1) 'Modification'
│ │ │ │ -C3A1C   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C3A20 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3A22   Length              000B (11)
│ │ │ │ -C3A24   Version             01 (1)
│ │ │ │ -C3A25   UID Size            04 (4)
│ │ │ │ -C3A26   UID                 00000000 (0)
│ │ │ │ -C3A2A   GID Size            04 (4)
│ │ │ │ -C3A2B   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3A2F CENTRAL HEADER #53    02014B50 (33639248)
│ │ │ │ -C3A33 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3A34 Created OS            03 (3) 'Unix'
│ │ │ │ -C3A35 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3A36 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3A37 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3A39 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3A3B Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C3A3F CRC                   C55EF92D (3311335725)
│ │ │ │ -C3A43 Compressed Size       00000AE8 (2792)
│ │ │ │ -C3A47 Uncompressed Size     000021E8 (8680)
│ │ │ │ -C3A4B Filename Length       0014 (20)
│ │ │ │ -C3A4D Extra Length          0018 (24)
│ │ │ │ -C3A4F Comment Length        0000 (0)
│ │ │ │ -C3A51 Disk Start            0000 (0)
│ │ │ │ -C3A53 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3A55 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3A59 Local Header Offset   00063706 (407302)
│ │ │ │ -C3A5D Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3A5D: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3A71 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3A73   Length              0005 (5)
│ │ │ │ -C3A75   Flags               01 (1) 'Modification'
│ │ │ │ -C3A76   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C3A7A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3A7C   Length              000B (11)
│ │ │ │ -C3A7E   Version             01 (1)
│ │ │ │ -C3A7F   UID Size            04 (4)
│ │ │ │ -C3A80   UID                 00000000 (0)
│ │ │ │ -C3A84   GID Size            04 (4)
│ │ │ │ -C3A85   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3A89 CENTRAL HEADER #54    02014B50 (33639248)
│ │ │ │ -C3A8D Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3A8E Created OS            03 (3) 'Unix'
│ │ │ │ -C3A8F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3A90 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3A91 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3A93 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3A95 Modification Time     5C8FA0E3 (1552916707) 'Wed Apr 15 20:07:06 2026'
│ │ │ │ -C3A99 CRC                   B3826829 (3011668009)
│ │ │ │ -C3A9D Compressed Size       0000B524 (46372)
│ │ │ │ -C3AA1 Uncompressed Size     00041755 (268117)
│ │ │ │ -C3AA5 Filename Length       0017 (23)
│ │ │ │ -C3AA7 Extra Length          0018 (24)
│ │ │ │ -C3AA9 Comment Length        0000 (0)
│ │ │ │ -C3AAB Disk Start            0000 (0)
│ │ │ │ -C3AAD Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3AAF Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3AB3 Local Header Offset   0006423C (410172)
│ │ │ │ -C3AB7 Filename              'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3AB7: Filename 'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3ACE Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3AD0   Length              0005 (5)
│ │ │ │ -C3AD2   Flags               01 (1) 'Modification'
│ │ │ │ -C3AD3   Modification Time   69DFEFEB (1776283627) 'Wed Apr 15 20:07:07 2026'
│ │ │ │ -C3AD7 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3AD9   Length              000B (11)
│ │ │ │ -C3ADB   Version             01 (1)
│ │ │ │ -C3ADC   UID Size            04 (4)
│ │ │ │ -C3ADD   UID                 00000000 (0)
│ │ │ │ -C3AE1   GID Size            04 (4)
│ │ │ │ -C3AE2   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3AE6 CENTRAL HEADER #55    02014B50 (33639248)
│ │ │ │ -C3AEA Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3AEB Created OS            03 (3) 'Unix'
│ │ │ │ -C3AEC Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3AED Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3AEE General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3AF0 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3AF2 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3AF6 CRC                   A49E0590 (2761819536)
│ │ │ │ -C3AFA Compressed Size       000003FE (1022)
│ │ │ │ -C3AFE Uncompressed Size     0000093D (2365)
│ │ │ │ -C3B02 Filename Length       0013 (19)
│ │ │ │ -C3B04 Extra Length          0018 (24)
│ │ │ │ -C3B06 Comment Length        0000 (0)
│ │ │ │ -C3B08 Disk Start            0000 (0)
│ │ │ │ -C3B0A Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3B0C Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3B10 Local Header Offset   0006F7B1 (456625)
│ │ │ │ -C3B14 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3B14: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3B27 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3B29   Length              0005 (5)
│ │ │ │ -C3B2B   Flags               01 (1) 'Modification'
│ │ │ │ -C3B2C   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3B30 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3B32   Length              000B (11)
│ │ │ │ -C3B34   Version             01 (1)
│ │ │ │ -C3B35   UID Size            04 (4)
│ │ │ │ -C3B36   UID                 00000000 (0)
│ │ │ │ -C3B3A   GID Size            04 (4)
│ │ │ │ -C3B3B   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3B3F CENTRAL HEADER #56    02014B50 (33639248)
│ │ │ │ -C3B43 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3B44 Created OS            03 (3) 'Unix'
│ │ │ │ -C3B45 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3B46 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3B47 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3B49 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3B4B Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3B4F CRC                   1FD7FA48 (534248008)
│ │ │ │ -C3B53 Compressed Size       000014D8 (5336)
│ │ │ │ -C3B57 Uncompressed Size     00006892 (26770)
│ │ │ │ -C3B5B Filename Length       0012 (18)
│ │ │ │ -C3B5D Extra Length          0018 (24)
│ │ │ │ -C3B5F Comment Length        0000 (0)
│ │ │ │ -C3B61 Disk Start            0000 (0)
│ │ │ │ -C3B63 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3B65 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3B69 Local Header Offset   0006FBFC (457724)
│ │ │ │ -C3B6D Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3B6D: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3B7F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3B81   Length              0005 (5)
│ │ │ │ -C3B83   Flags               01 (1) 'Modification'
│ │ │ │ -C3B84   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3B88 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3B8A   Length              000B (11)
│ │ │ │ -C3B8C   Version             01 (1)
│ │ │ │ -C3B8D   UID Size            04 (4)
│ │ │ │ -C3B8E   UID                 00000000 (0)
│ │ │ │ -C3B92   GID Size            04 (4)
│ │ │ │ -C3B93   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3B97 CENTRAL HEADER #57    02014B50 (33639248)
│ │ │ │ -C3B9B Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3B9C Created OS            03 (3) 'Unix'
│ │ │ │ -C3B9D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3B9E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3B9F General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3BA1 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3BA3 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3BA7 CRC                   7167272B (1902585643)
│ │ │ │ -C3BAB Compressed Size       00001205 (4613)
│ │ │ │ -C3BAF Uncompressed Size     0000414F (16719)
│ │ │ │ -C3BB3 Filename Length       0012 (18)
│ │ │ │ -C3BB5 Extra Length          0018 (24)
│ │ │ │ -C3BB7 Comment Length        0000 (0)
│ │ │ │ -C3BB9 Disk Start            0000 (0)
│ │ │ │ -C3BBB Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3BBD Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3BC1 Local Header Offset   00071120 (463136)
│ │ │ │ -C3BC5 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3BC5: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3BD7 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3BD9   Length              0005 (5)
│ │ │ │ -C3BDB   Flags               01 (1) 'Modification'
│ │ │ │ -C3BDC   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3BE0 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3BE2   Length              000B (11)
│ │ │ │ -C3BE4   Version             01 (1)
│ │ │ │ -C3BE5   UID Size            04 (4)
│ │ │ │ -C3BE6   UID                 00000000 (0)
│ │ │ │ -C3BEA   GID Size            04 (4)
│ │ │ │ -C3BEB   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3BEF CENTRAL HEADER #58    02014B50 (33639248)
│ │ │ │ -C3BF3 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3BF4 Created OS            03 (3) 'Unix'
│ │ │ │ -C3BF5 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3BF6 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3BF7 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3BF9 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3BFB Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3BFF CRC                   5C8A4BDC (1552567260)
│ │ │ │ -C3C03 Compressed Size       00000704 (1796)
│ │ │ │ -C3C07 Uncompressed Size     000011A7 (4519)
│ │ │ │ -C3C0B Filename Length       0019 (25)
│ │ │ │ -C3C0D Extra Length          0018 (24)
│ │ │ │ -C3C0F Comment Length        0000 (0)
│ │ │ │ -C3C11 Disk Start            0000 (0)
│ │ │ │ -C3C13 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3C15 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3C19 Local Header Offset   00072371 (467825)
│ │ │ │ -C3C1D Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3C1D: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3C36 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3C38   Length              0005 (5)
│ │ │ │ -C3C3A   Flags               01 (1) 'Modification'
│ │ │ │ -C3C3B   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3C3F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3C41   Length              000B (11)
│ │ │ │ -C3C43   Version             01 (1)
│ │ │ │ -C3C44   UID Size            04 (4)
│ │ │ │ -C3C45   UID                 00000000 (0)
│ │ │ │ -C3C49   GID Size            04 (4)
│ │ │ │ -C3C4A   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3C4E CENTRAL HEADER #59    02014B50 (33639248)
│ │ │ │ -C3C52 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3C53 Created OS            03 (3) 'Unix'
│ │ │ │ -C3C54 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3C55 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3C56 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3C58 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3C5A Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3C5E CRC                   337967C1 (863594433)
│ │ │ │ -C3C62 Compressed Size       000018B8 (6328)
│ │ │ │ -C3C66 Uncompressed Size     0000A678 (42616)
│ │ │ │ -C3C6A Filename Length       0019 (25)
│ │ │ │ -C3C6C Extra Length          0018 (24)
│ │ │ │ -C3C6E Comment Length        0000 (0)
│ │ │ │ -C3C70 Disk Start            0000 (0)
│ │ │ │ -C3C72 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3C74 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3C78 Local Header Offset   00072AC8 (469704)
│ │ │ │ -C3C7C Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3C7C: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3C95 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3C97   Length              0005 (5)
│ │ │ │ -C3C99   Flags               01 (1) 'Modification'
│ │ │ │ -C3C9A   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3C9E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3CA0   Length              000B (11)
│ │ │ │ -C3CA2   Version             01 (1)
│ │ │ │ -C3CA3   UID Size            04 (4)
│ │ │ │ -C3CA4   UID                 00000000 (0)
│ │ │ │ -C3CA8   GID Size            04 (4)
│ │ │ │ -C3CA9   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3CAD CENTRAL HEADER #60    02014B50 (33639248)
│ │ │ │ -C3CB1 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3CB2 Created OS            03 (3) 'Unix'
│ │ │ │ -C3CB3 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3CB4 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3CB5 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3CB7 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3CB9 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3CBD CRC                   4D1409E6 (1293158886)
│ │ │ │ -C3CC1 Compressed Size       0000177C (6012)
│ │ │ │ -C3CC5 Uncompressed Size     0000472C (18220)
│ │ │ │ -C3CC9 Filename Length       0014 (20)
│ │ │ │ -C3CCB Extra Length          0018 (24)
│ │ │ │ -C3CCD Comment Length        0000 (0)
│ │ │ │ -C3CCF Disk Start            0000 (0)
│ │ │ │ -C3CD1 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3CD3 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3CD7 Local Header Offset   000743D3 (476115)
│ │ │ │ -C3CDB Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3CDB: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3CEF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3CF1   Length              0005 (5)
│ │ │ │ -C3CF3   Flags               01 (1) 'Modification'
│ │ │ │ -C3CF4   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3CF8 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3CFA   Length              000B (11)
│ │ │ │ -C3CFC   Version             01 (1)
│ │ │ │ -C3CFD   UID Size            04 (4)
│ │ │ │ -C3CFE   UID                 00000000 (0)
│ │ │ │ -C3D02   GID Size            04 (4)
│ │ │ │ -C3D03   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3D07 CENTRAL HEADER #61    02014B50 (33639248)
│ │ │ │ -C3D0B Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3D0C Created OS            03 (3) 'Unix'
│ │ │ │ -C3D0D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3D0E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3D0F General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3D11 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3D13 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3D17 CRC                   2F723DFF (796016127)
│ │ │ │ -C3D1B Compressed Size       00000409 (1033)
│ │ │ │ -C3D1F Uncompressed Size     00000825 (2085)
│ │ │ │ -C3D23 Filename Length       001C (28)
│ │ │ │ -C3D25 Extra Length          0018 (24)
│ │ │ │ -C3D27 Comment Length        0000 (0)
│ │ │ │ -C3D29 Disk Start            0000 (0)
│ │ │ │ -C3D2B Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3D2D Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3D31 Local Header Offset   00075B9D (482205)
│ │ │ │ -C3D35 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3D35: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3D51 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3D53   Length              0005 (5)
│ │ │ │ -C3D55   Flags               01 (1) 'Modification'
│ │ │ │ -C3D56   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3D5A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3D5C   Length              000B (11)
│ │ │ │ -C3D5E   Version             01 (1)
│ │ │ │ -C3D5F   UID Size            04 (4)
│ │ │ │ -C3D60   UID                 00000000 (0)
│ │ │ │ -C3D64   GID Size            04 (4)
│ │ │ │ -C3D65   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3D69 CENTRAL HEADER #62    02014B50 (33639248)
│ │ │ │ -C3D6D Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3D6E Created OS            03 (3) 'Unix'
│ │ │ │ -C3D6F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3D70 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3D71 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3D73 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3D75 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3D79 CRC                   CCD906B0 (3436775088)
│ │ │ │ -C3D7D Compressed Size       000024C6 (9414)
│ │ │ │ -C3D81 Uncompressed Size     0000B65D (46685)
│ │ │ │ -C3D85 Filename Length       001F (31)
│ │ │ │ -C3D87 Extra Length          0018 (24)
│ │ │ │ -C3D89 Comment Length        0000 (0)
│ │ │ │ -C3D8B Disk Start            0000 (0)
│ │ │ │ -C3D8D Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3D8F Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3D93 Local Header Offset   00075FFC (483324)
│ │ │ │ -C3D97 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3D97: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3DB6 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3DB8   Length              0005 (5)
│ │ │ │ -C3DBA   Flags               01 (1) 'Modification'
│ │ │ │ -C3DBB   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3DBF Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3DC1   Length              000B (11)
│ │ │ │ -C3DC3   Version             01 (1)
│ │ │ │ -C3DC4   UID Size            04 (4)
│ │ │ │ -C3DC5   UID                 00000000 (0)
│ │ │ │ -C3DC9   GID Size            04 (4)
│ │ │ │ -C3DCA   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3DCE CENTRAL HEADER #63    02014B50 (33639248)
│ │ │ │ -C3DD2 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3DD3 Created OS            03 (3) 'Unix'
│ │ │ │ -C3DD4 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3DD5 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3DD6 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3DD8 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3DDA Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3DDE CRC                   E78CD1A8 (3884765608)
│ │ │ │ -C3DE2 Compressed Size       00000E7C (3708)
│ │ │ │ -C3DE6 Uncompressed Size     000052DA (21210)
│ │ │ │ -C3DEA Filename Length       001F (31)
│ │ │ │ -C3DEC Extra Length          0018 (24)
│ │ │ │ -C3DEE Comment Length        0000 (0)
│ │ │ │ -C3DF0 Disk Start            0000 (0)
│ │ │ │ -C3DF2 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3DF4 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3DF8 Local Header Offset   0007851B (492827)
│ │ │ │ -C3DFC Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3DFC: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3E1B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3E1D   Length              0005 (5)
│ │ │ │ -C3E1F   Flags               01 (1) 'Modification'
│ │ │ │ -C3E20   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3E24 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3E26   Length              000B (11)
│ │ │ │ -C3E28   Version             01 (1)
│ │ │ │ -C3E29   UID Size            04 (4)
│ │ │ │ -C3E2A   UID                 00000000 (0)
│ │ │ │ -C3E2E   GID Size            04 (4)
│ │ │ │ -C3E2F   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3E33 CENTRAL HEADER #64    02014B50 (33639248)
│ │ │ │ -C3E37 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3E38 Created OS            03 (3) 'Unix'
│ │ │ │ -C3E39 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3E3A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3E3B General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3E3D Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3E3F Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3E43 CRC                   E196989B (3784743067)
│ │ │ │ -C3E47 Compressed Size       00000A44 (2628)
│ │ │ │ -C3E4B Uncompressed Size     0000247A (9338)
│ │ │ │ -C3E4F Filename Length       0013 (19)
│ │ │ │ -C3E51 Extra Length          0018 (24)
│ │ │ │ -C3E53 Comment Length        0000 (0)
│ │ │ │ -C3E55 Disk Start            0000 (0)
│ │ │ │ -C3E57 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3E59 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3E5D Local Header Offset   000793F0 (496624)
│ │ │ │ -C3E61 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3E61: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3E74 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3E76   Length              0005 (5)
│ │ │ │ -C3E78   Flags               01 (1) 'Modification'
│ │ │ │ -C3E79   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3E7D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3E7F   Length              000B (11)
│ │ │ │ -C3E81   Version             01 (1)
│ │ │ │ -C3E82   UID Size            04 (4)
│ │ │ │ -C3E83   UID                 00000000 (0)
│ │ │ │ -C3E87   GID Size            04 (4)
│ │ │ │ -C3E88   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3E8C CENTRAL HEADER #65    02014B50 (33639248)
│ │ │ │ -C3E90 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3E91 Created OS            03 (3) 'Unix'
│ │ │ │ -C3E92 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3E93 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3E94 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3E96 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3E98 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3E9C CRC                   34AC5B41 (883710785)
│ │ │ │ -C3EA0 Compressed Size       00002591 (9617)
│ │ │ │ -C3EA4 Uncompressed Size     0000BAA4 (47780)
│ │ │ │ -C3EA8 Filename Length       0019 (25)
│ │ │ │ -C3EAA Extra Length          0018 (24)
│ │ │ │ -C3EAC Comment Length        0000 (0)
│ │ │ │ -C3EAE Disk Start            0000 (0)
│ │ │ │ -C3EB0 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3EB2 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3EB6 Local Header Offset   00079E81 (499329)
│ │ │ │ -C3EBA Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3EBA: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3ED3 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3ED5   Length              0005 (5)
│ │ │ │ -C3ED7   Flags               01 (1) 'Modification'
│ │ │ │ -C3ED8   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3EDC Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3EDE   Length              000B (11)
│ │ │ │ -C3EE0   Version             01 (1)
│ │ │ │ -C3EE1   UID Size            04 (4)
│ │ │ │ -C3EE2   UID                 00000000 (0)
│ │ │ │ -C3EE6   GID Size            04 (4)
│ │ │ │ -C3EE7   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3EEB CENTRAL HEADER #66    02014B50 (33639248)
│ │ │ │ -C3EEF Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3EF0 Created OS            03 (3) 'Unix'
│ │ │ │ -C3EF1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3EF2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3EF3 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3EF5 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3EF7 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3EFB CRC                   97E60E7F (2548436607)
│ │ │ │ -C3EFF Compressed Size       00000EFD (3837)
│ │ │ │ -C3F03 Uncompressed Size     00003A2F (14895)
│ │ │ │ -C3F07 Filename Length       0024 (36)
│ │ │ │ -C3F09 Extra Length          0018 (24)
│ │ │ │ -C3F0B Comment Length        0000 (0)
│ │ │ │ -C3F0D Disk Start            0000 (0)
│ │ │ │ -C3F0F Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3F11 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3F15 Local Header Offset   0007C465 (509029)
│ │ │ │ -C3F19 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3F19: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3F3D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3F3F   Length              0005 (5)
│ │ │ │ -C3F41   Flags               01 (1) 'Modification'
│ │ │ │ -C3F42   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3F46 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3F48   Length              000B (11)
│ │ │ │ -C3F4A   Version             01 (1)
│ │ │ │ -C3F4B   UID Size            04 (4)
│ │ │ │ -C3F4C   UID                 00000000 (0)
│ │ │ │ -C3F50   GID Size            04 (4)
│ │ │ │ -C3F51   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3F55 CENTRAL HEADER #67    02014B50 (33639248)
│ │ │ │ -C3F59 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3F5A Created OS            03 (3) 'Unix'
│ │ │ │ -C3F5B Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3F5C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3F5D General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3F5F Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3F61 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3F65 CRC                   247F076B (612304747)
│ │ │ │ -C3F69 Compressed Size       00001AEA (6890)
│ │ │ │ -C3F6D Uncompressed Size     00005F7F (24447)
│ │ │ │ -C3F71 Filename Length       0017 (23)
│ │ │ │ -C3F73 Extra Length          0018 (24)
│ │ │ │ -C3F75 Comment Length        0000 (0)
│ │ │ │ -C3F77 Disk Start            0000 (0)
│ │ │ │ -C3F79 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3F7B Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3F7F Local Header Offset   0007D3C0 (512960)
│ │ │ │ -C3F83 Filename              'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3F83: Filename 'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C3F9A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C3F9C   Length              0005 (5)
│ │ │ │ -C3F9E   Flags               01 (1) 'Modification'
│ │ │ │ -C3F9F   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3FA3 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C3FA5   Length              000B (11)
│ │ │ │ -C3FA7   Version             01 (1)
│ │ │ │ -C3FA8   UID Size            04 (4)
│ │ │ │ -C3FA9   UID                 00000000 (0)
│ │ │ │ -C3FAD   GID Size            04 (4)
│ │ │ │ -C3FAE   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C3FB2 CENTRAL HEADER #68    02014B50 (33639248)
│ │ │ │ -C3FB6 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C3FB7 Created OS            03 (3) 'Unix'
│ │ │ │ -C3FB8 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C3FB9 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C3FBA General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C3FBC Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C3FBE Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C3FC2 CRC                   11E32AF1 (300100337)
│ │ │ │ -C3FC6 Compressed Size       00000ED3 (3795)
│ │ │ │ -C3FCA Uncompressed Size     000038E2 (14562)
│ │ │ │ -C3FCE Filename Length       0023 (35)
│ │ │ │ -C3FD0 Extra Length          0018 (24)
│ │ │ │ -C3FD2 Comment Length        0000 (0)
│ │ │ │ -C3FD4 Disk Start            0000 (0)
│ │ │ │ -C3FD6 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C3FD8 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C3FDC Local Header Offset   0007EEFB (519931)
│ │ │ │ -C3FE0 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC3FE0: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C4003 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4005   Length              0005 (5)
│ │ │ │ -C4007   Flags               01 (1) 'Modification'
│ │ │ │ -C4008   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C400C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C400E   Length              000B (11)
│ │ │ │ -C4010   Version             01 (1)
│ │ │ │ -C4011   UID Size            04 (4)
│ │ │ │ -C4012   UID                 00000000 (0)
│ │ │ │ -C4016   GID Size            04 (4)
│ │ │ │ -C4017   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C401B CENTRAL HEADER #69    02014B50 (33639248)
│ │ │ │ -C401F Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C4020 Created OS            03 (3) 'Unix'
│ │ │ │ -C4021 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C4022 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C4023 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C4025 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C4027 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C402B CRC                   2DB7929F (767005343)
│ │ │ │ -C402F Compressed Size       00000113 (275)
│ │ │ │ -C4033 Uncompressed Size     000001F3 (499)
│ │ │ │ -C4037 Filename Length       001B (27)
│ │ │ │ -C4039 Extra Length          0018 (24)
│ │ │ │ -C403B Comment Length        0000 (0)
│ │ │ │ -C403D Disk Start            0000 (0)
│ │ │ │ -C403F Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C4041 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C4045 Local Header Offset   0007FE2B (523819)
│ │ │ │ -C4049 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC4049: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C4064 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4066   Length              0005 (5)
│ │ │ │ -C4068   Flags               01 (1) 'Modification'
│ │ │ │ -C4069   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C406D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C406F   Length              000B (11)
│ │ │ │ -C4071   Version             01 (1)
│ │ │ │ -C4072   UID Size            04 (4)
│ │ │ │ -C4073   UID                 00000000 (0)
│ │ │ │ -C4077   GID Size            04 (4)
│ │ │ │ -C4078   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C407C CENTRAL HEADER #70    02014B50 (33639248)
│ │ │ │ -C4080 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C4081 Created OS            03 (3) 'Unix'
│ │ │ │ -C4082 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C4083 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C4084 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C4086 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C4088 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C408C CRC                   3E2ED2F5 (1043256053)
│ │ │ │ -C4090 Compressed Size       0000188D (6285)
│ │ │ │ -C4094 Uncompressed Size     00008FA8 (36776)
│ │ │ │ -C4098 Filename Length       001D (29)
│ │ │ │ -C409A Extra Length          0018 (24)
│ │ │ │ -C409C Comment Length        0000 (0)
│ │ │ │ -C409E Disk Start            0000 (0)
│ │ │ │ -C40A0 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C40A2 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C40A6 Local Header Offset   0007FF93 (524179)
│ │ │ │ -C40AA Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC40AA: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C40C7 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C40C9   Length              0005 (5)
│ │ │ │ -C40CB   Flags               01 (1) 'Modification'
│ │ │ │ -C40CC   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C40D0 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C40D2   Length              000B (11)
│ │ │ │ -C40D4   Version             01 (1)
│ │ │ │ -C40D5   UID Size            04 (4)
│ │ │ │ -C40D6   UID                 00000000 (0)
│ │ │ │ -C40DA   GID Size            04 (4)
│ │ │ │ -C40DB   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C40DF CENTRAL HEADER #71    02014B50 (33639248)
│ │ │ │ -C40E3 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C40E4 Created OS            03 (3) 'Unix'
│ │ │ │ -C40E5 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C40E6 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C40E7 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C40E9 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C40EB Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C40EF CRC                   13F8A234 (335061556)
│ │ │ │ -C40F3 Compressed Size       0000164C (5708)
│ │ │ │ -C40F7 Uncompressed Size     00003A9B (15003)
│ │ │ │ -C40FB Filename Length       0015 (21)
│ │ │ │ -C40FD Extra Length          0018 (24)
│ │ │ │ -C40FF Comment Length        0000 (0)
│ │ │ │ -C4101 Disk Start            0000 (0)
│ │ │ │ -C4103 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C4105 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C4109 Local Header Offset   00081877 (530551)
│ │ │ │ -C410D Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC410D: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C4122 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4124   Length              0005 (5)
│ │ │ │ -C4126   Flags               01 (1) 'Modification'
│ │ │ │ -C4127   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C412B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C412D   Length              000B (11)
│ │ │ │ -C412F   Version             01 (1)
│ │ │ │ -C4130   UID Size            04 (4)
│ │ │ │ -C4131   UID                 00000000 (0)
│ │ │ │ -C4135   GID Size            04 (4)
│ │ │ │ -C4136   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C413A CENTRAL HEADER #72    02014B50 (33639248)
│ │ │ │ -C413E Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C413F Created OS            03 (3) 'Unix'
│ │ │ │ -C4140 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C4141 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C4142 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C4144 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C4146 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C414A CRC                   945176DD (2488366813)
│ │ │ │ -C414E Compressed Size       000040CE (16590)
│ │ │ │ -C4152 Uncompressed Size     000133AC (78764)
│ │ │ │ -C4156 Filename Length       0016 (22)
│ │ │ │ -C4158 Extra Length          0018 (24)
│ │ │ │ -C415A Comment Length        0000 (0)
│ │ │ │ -C415C Disk Start            0000 (0)
│ │ │ │ -C415E Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C4160 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C4164 Local Header Offset   00082F12 (536338)
│ │ │ │ -C4168 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC4168: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C417E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4180   Length              0005 (5)
│ │ │ │ -C4182   Flags               01 (1) 'Modification'
│ │ │ │ -C4183   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C4187 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C4189   Length              000B (11)
│ │ │ │ -C418B   Version             01 (1)
│ │ │ │ -C418C   UID Size            04 (4)
│ │ │ │ -C418D   UID                 00000000 (0)
│ │ │ │ -C4191   GID Size            04 (4)
│ │ │ │ -C4192   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C4196 CENTRAL HEADER #73    02014B50 (33639248)
│ │ │ │ -C419A Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C419B Created OS            03 (3) 'Unix'
│ │ │ │ -C419C Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C419D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C419E General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C41A0 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C41A2 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C41A6 CRC                   FF953A42 (4287969858)
│ │ │ │ -C41AA Compressed Size       00003EB3 (16051)
│ │ │ │ -C41AE Uncompressed Size     0001C78B (116619)
│ │ │ │ -C41B2 Filename Length       0019 (25)
│ │ │ │ -C41B4 Extra Length          0018 (24)
│ │ │ │ -C41B6 Comment Length        0000 (0)
│ │ │ │ -C41B8 Disk Start            0000 (0)
│ │ │ │ -C41BA Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C41BC Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C41C0 Local Header Offset   00087030 (553008)
│ │ │ │ -C41C4 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC41C4: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C41DD Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C41DF   Length              0005 (5)
│ │ │ │ -C41E1   Flags               01 (1) 'Modification'
│ │ │ │ -C41E2   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C41E6 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C41E8   Length              000B (11)
│ │ │ │ -C41EA   Version             01 (1)
│ │ │ │ -C41EB   UID Size            04 (4)
│ │ │ │ -C41EC   UID                 00000000 (0)
│ │ │ │ -C41F0   GID Size            04 (4)
│ │ │ │ -C41F1   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C41F5 CENTRAL HEADER #74    02014B50 (33639248)
│ │ │ │ -C41F9 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C41FA Created OS            03 (3) 'Unix'
│ │ │ │ -C41FB Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C41FC Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C41FD General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C41FF Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C4201 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C4205 CRC                   D20AC80F (3523921935)
│ │ │ │ -C4209 Compressed Size       0000089D (2205)
│ │ │ │ -C420D Uncompressed Size     000036CC (14028)
│ │ │ │ -C4211 Filename Length       0011 (17)
│ │ │ │ -C4213 Extra Length          0018 (24)
│ │ │ │ -C4215 Comment Length        0000 (0)
│ │ │ │ -C4217 Disk Start            0000 (0)
│ │ │ │ -C4219 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C421B Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C421F Local Header Offset   0008AF36 (569142)
│ │ │ │ -C4223 Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC4223: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C4234 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4236   Length              0005 (5)
│ │ │ │ -C4238   Flags               01 (1) 'Modification'
│ │ │ │ -C4239   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C423D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C423F   Length              000B (11)
│ │ │ │ -C4241   Version             01 (1)
│ │ │ │ -C4242   UID Size            04 (4)
│ │ │ │ -C4243   UID                 00000000 (0)
│ │ │ │ -C4247   GID Size            04 (4)
│ │ │ │ -C4248   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C424C CENTRAL HEADER #75    02014B50 (33639248)
│ │ │ │ -C4250 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C4251 Created OS            03 (3) 'Unix'
│ │ │ │ -C4252 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C4253 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C4254 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C4256 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C4258 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C425C CRC                   ACBCD47B (2898056315)
│ │ │ │ -C4260 Compressed Size       0000519E (20894)
│ │ │ │ -C4264 Uncompressed Size     0001F99A (129434)
│ │ │ │ -C4268 Filename Length       0015 (21)
│ │ │ │ -C426A Extra Length          0018 (24)
│ │ │ │ -C426C Comment Length        0000 (0)
│ │ │ │ -C426E Disk Start            0000 (0)
│ │ │ │ -C4270 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C4272 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C4276 Local Header Offset   0008B81E (571422)
│ │ │ │ -C427A Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC427A: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C428F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4291   Length              0005 (5)
│ │ │ │ -C4293   Flags               01 (1) 'Modification'
│ │ │ │ -C4294   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C4298 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C429A   Length              000B (11)
│ │ │ │ -C429C   Version             01 (1)
│ │ │ │ -C429D   UID Size            04 (4)
│ │ │ │ -C429E   UID                 00000000 (0)
│ │ │ │ -C42A2   GID Size            04 (4)
│ │ │ │ -C42A3   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C42A7 CENTRAL HEADER #76    02014B50 (33639248)
│ │ │ │ -C42AB Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C42AC Created OS            03 (3) 'Unix'
│ │ │ │ -C42AD Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C42AE Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C42AF General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C42B1 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C42B3 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C42B7 CRC                   2CBD0730 (750585648)
│ │ │ │ -C42BB Compressed Size       00001C41 (7233)
│ │ │ │ -C42BF Uncompressed Size     00008AC8 (35528)
│ │ │ │ -C42C3 Filename Length       0019 (25)
│ │ │ │ -C42C5 Extra Length          0018 (24)
│ │ │ │ -C42C7 Comment Length        0000 (0)
│ │ │ │ -C42C9 Disk Start            0000 (0)
│ │ │ │ -C42CB Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C42CD Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C42D1 Local Header Offset   00090A0B (592395)
│ │ │ │ -C42D5 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC42D5: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C42EE Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C42F0   Length              0005 (5)
│ │ │ │ -C42F2   Flags               01 (1) 'Modification'
│ │ │ │ -C42F3   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C42F7 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C42F9   Length              000B (11)
│ │ │ │ -C42FB   Version             01 (1)
│ │ │ │ -C42FC   UID Size            04 (4)
│ │ │ │ -C42FD   UID                 00000000 (0)
│ │ │ │ -C4301   GID Size            04 (4)
│ │ │ │ -C4302   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C4306 CENTRAL HEADER #77    02014B50 (33639248)
│ │ │ │ -C430A Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C430B Created OS            03 (3) 'Unix'
│ │ │ │ -C430C Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C430D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C430E General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C4310 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C4312 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C4316 CRC                   896CE926 (2305616166)
│ │ │ │ -C431A Compressed Size       00000D91 (3473)
│ │ │ │ -C431E Uncompressed Size     00002EA4 (11940)
│ │ │ │ -C4322 Filename Length       0018 (24)
│ │ │ │ -C4324 Extra Length          0018 (24)
│ │ │ │ -C4326 Comment Length        0000 (0)
│ │ │ │ -C4328 Disk Start            0000 (0)
│ │ │ │ -C432A Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C432C Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C4330 Local Header Offset   0009269F (599711)
│ │ │ │ -C4334 Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC4334: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C434C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C434E   Length              0005 (5)
│ │ │ │ -C4350   Flags               01 (1) 'Modification'
│ │ │ │ -C4351   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C4355 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C4357   Length              000B (11)
│ │ │ │ -C4359   Version             01 (1)
│ │ │ │ -C435A   UID Size            04 (4)
│ │ │ │ -C435B   UID                 00000000 (0)
│ │ │ │ -C435F   GID Size            04 (4)
│ │ │ │ -C4360   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C4364 CENTRAL HEADER #78    02014B50 (33639248)
│ │ │ │ -C4368 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C4369 Created OS            03 (3) 'Unix'
│ │ │ │ -C436A Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C436B Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C436C General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C436E Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C4370 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C4374 CRC                   535B63FB (1398498299)
│ │ │ │ -C4378 Compressed Size       000001DF (479)
│ │ │ │ -C437C Uncompressed Size     00000323 (803)
│ │ │ │ -C4380 Filename Length       0011 (17)
│ │ │ │ -C4382 Extra Length          0018 (24)
│ │ │ │ -C4384 Comment Length        0000 (0)
│ │ │ │ -C4386 Disk Start            0000 (0)
│ │ │ │ -C4388 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C438A Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C438E Local Header Offset   00093482 (603266)
│ │ │ │ -C4392 Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC4392: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C43A3 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C43A5   Length              0005 (5)
│ │ │ │ -C43A7   Flags               01 (1) 'Modification'
│ │ │ │ -C43A8   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C43AC Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C43AE   Length              000B (11)
│ │ │ │ -C43B0   Version             01 (1)
│ │ │ │ -C43B1   UID Size            04 (4)
│ │ │ │ -C43B2   UID                 00000000 (0)
│ │ │ │ -C43B6   GID Size            04 (4)
│ │ │ │ -C43B7   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C43BB CENTRAL HEADER #79    02014B50 (33639248)
│ │ │ │ -C43BF Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C43C0 Created OS            03 (3) 'Unix'
│ │ │ │ -C43C1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C43C2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C43C3 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C43C5 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C43C7 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C43CB CRC                   32CAD6D8 (852154072)
│ │ │ │ -C43CF Compressed Size       000006BE (1726)
│ │ │ │ -C43D3 Uncompressed Size     0000141F (5151)
│ │ │ │ -C43D7 Filename Length       0019 (25)
│ │ │ │ -C43D9 Extra Length          0018 (24)
│ │ │ │ -C43DB Comment Length        0000 (0)
│ │ │ │ -C43DD Disk Start            0000 (0)
│ │ │ │ -C43DF Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C43E1 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C43E5 Local Header Offset   000936AC (603820)
│ │ │ │ -C43E9 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC43E9: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C4402 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4404   Length              0005 (5)
│ │ │ │ -C4406   Flags               01 (1) 'Modification'
│ │ │ │ -C4407   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C440B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C440D   Length              000B (11)
│ │ │ │ -C440F   Version             01 (1)
│ │ │ │ -C4410   UID Size            04 (4)
│ │ │ │ -C4411   UID                 00000000 (0)
│ │ │ │ -C4415   GID Size            04 (4)
│ │ │ │ -C4416   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C441A CENTRAL HEADER #80    02014B50 (33639248)
│ │ │ │ -C441E Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C441F Created OS            03 (3) 'Unix'
│ │ │ │ -C4420 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C4421 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C4422 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C4424 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C4426 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C442A CRC                   FC6D6CD0 (4235029712)
│ │ │ │ -C442E Compressed Size       00001B8D (7053)
│ │ │ │ -C4432 Uncompressed Size     00009F5F (40799)
│ │ │ │ -C4436 Filename Length       0018 (24)
│ │ │ │ -C4438 Extra Length          0018 (24)
│ │ │ │ -C443A Comment Length        0000 (0)
│ │ │ │ -C443C Disk Start            0000 (0)
│ │ │ │ -C443E Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C4440 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C4444 Local Header Offset   00093DBD (605629)
│ │ │ │ -C4448 Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC4448: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C4460 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4462   Length              0005 (5)
│ │ │ │ -C4464   Flags               01 (1) 'Modification'
│ │ │ │ -C4465   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C4469 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C446B   Length              000B (11)
│ │ │ │ -C446D   Version             01 (1)
│ │ │ │ -C446E   UID Size            04 (4)
│ │ │ │ -C446F   UID                 00000000 (0)
│ │ │ │ -C4473   GID Size            04 (4)
│ │ │ │ -C4474   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C4478 CENTRAL HEADER #81    02014B50 (33639248)
│ │ │ │ -C447C Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C447D Created OS            03 (3) 'Unix'
│ │ │ │ -C447E Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C447F Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C4480 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C4482 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C4484 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C4488 CRC                   11186130 (286810416)
│ │ │ │ -C448C Compressed Size       000016FF (5887)
│ │ │ │ -C4490 Uncompressed Size     00008B12 (35602)
│ │ │ │ -C4494 Filename Length       0012 (18)
│ │ │ │ -C4496 Extra Length          0018 (24)
│ │ │ │ -C4498 Comment Length        0000 (0)
│ │ │ │ -C449A Disk Start            0000 (0)
│ │ │ │ -C449C Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C449E Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C44A2 Local Header Offset   0009599C (612764)
│ │ │ │ -C44A6 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC44A6: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C44B8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C44BA   Length              0005 (5)
│ │ │ │ -C44BC   Flags               01 (1) 'Modification'
│ │ │ │ -C44BD   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C44C1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C44C3   Length              000B (11)
│ │ │ │ -C44C5   Version             01 (1)
│ │ │ │ -C44C6   UID Size            04 (4)
│ │ │ │ -C44C7   UID                 00000000 (0)
│ │ │ │ -C44CB   GID Size            04 (4)
│ │ │ │ -C44CC   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C44D0 CENTRAL HEADER #82    02014B50 (33639248)
│ │ │ │ -C44D4 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C44D5 Created OS            03 (3) 'Unix'
│ │ │ │ -C44D6 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C44D7 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C44D8 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C44DA Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C44DC Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C44E0 CRC                   0D2BB7BA (220968890)
│ │ │ │ -C44E4 Compressed Size       00001E0B (7691)
│ │ │ │ -C44E8 Uncompressed Size     00008823 (34851)
│ │ │ │ -C44EC Filename Length       0016 (22)
│ │ │ │ -C44EE Extra Length          0018 (24)
│ │ │ │ -C44F0 Comment Length        0000 (0)
│ │ │ │ -C44F2 Disk Start            0000 (0)
│ │ │ │ -C44F4 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C44F6 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C44FA Local Header Offset   000970E7 (618727)
│ │ │ │ -C44FE Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC44FE: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C4514 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4516   Length              0005 (5)
│ │ │ │ -C4518   Flags               01 (1) 'Modification'
│ │ │ │ -C4519   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C451D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C451F   Length              000B (11)
│ │ │ │ -C4521   Version             01 (1)
│ │ │ │ -C4522   UID Size            04 (4)
│ │ │ │ -C4523   UID                 00000000 (0)
│ │ │ │ -C4527   GID Size            04 (4)
│ │ │ │ -C4528   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C452C CENTRAL HEADER #83    02014B50 (33639248)
│ │ │ │ -C4530 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C4531 Created OS            03 (3) 'Unix'
│ │ │ │ -C4532 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C4533 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C4534 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C4536 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C4538 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C453C CRC                   AA93B274 (2861806196)
│ │ │ │ -C4540 Compressed Size       000029A8 (10664)
│ │ │ │ -C4544 Uncompressed Size     0000D04F (53327)
│ │ │ │ -C4548 Filename Length       001A (26)
│ │ │ │ -C454A Extra Length          0018 (24)
│ │ │ │ -C454C Comment Length        0000 (0)
│ │ │ │ -C454E Disk Start            0000 (0)
│ │ │ │ -C4550 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C4552 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C4556 Local Header Offset   00098F42 (626498)
│ │ │ │ -C455A Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC455A: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C4574 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4576   Length              0005 (5)
│ │ │ │ -C4578   Flags               01 (1) 'Modification'
│ │ │ │ -C4579   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C457D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C457F   Length              000B (11)
│ │ │ │ -C4581   Version             01 (1)
│ │ │ │ -C4582   UID Size            04 (4)
│ │ │ │ -C4583   UID                 00000000 (0)
│ │ │ │ -C4587   GID Size            04 (4)
│ │ │ │ -C4588   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C458C CENTRAL HEADER #84    02014B50 (33639248)
│ │ │ │ -C4590 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C4591 Created OS            03 (3) 'Unix'
│ │ │ │ -C4592 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C4593 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C4594 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C4596 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C4598 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C459C CRC                   C898661A (3365430810)
│ │ │ │ -C45A0 Compressed Size       000009AB (2475)
│ │ │ │ -C45A4 Uncompressed Size     00001DAC (7596)
│ │ │ │ -C45A8 Filename Length       0018 (24)
│ │ │ │ -C45AA Extra Length          0018 (24)
│ │ │ │ -C45AC Comment Length        0000 (0)
│ │ │ │ -C45AE Disk Start            0000 (0)
│ │ │ │ -C45B0 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C45B2 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C45B6 Local Header Offset   0009B93E (637246)
│ │ │ │ -C45BA Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC45BA: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C45D2 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C45D4   Length              0005 (5)
│ │ │ │ -C45D6   Flags               01 (1) 'Modification'
│ │ │ │ -C45D7   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C45DB Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C45DD   Length              000B (11)
│ │ │ │ -C45DF   Version             01 (1)
│ │ │ │ -C45E0   UID Size            04 (4)
│ │ │ │ -C45E1   UID                 00000000 (0)
│ │ │ │ -C45E5   GID Size            04 (4)
│ │ │ │ -C45E6   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C45EA CENTRAL HEADER #85    02014B50 (33639248)
│ │ │ │ -C45EE Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C45EF Created OS            03 (3) 'Unix'
│ │ │ │ -C45F0 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C45F1 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C45F2 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C45F4 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C45F6 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C45FA CRC                   F0556E9A (4032130714)
│ │ │ │ -C45FE Compressed Size       000152EE (86766)
│ │ │ │ -C4602 Uncompressed Size     000159F8 (88568)
│ │ │ │ -C4606 Filename Length       001E (30)
│ │ │ │ -C4608 Extra Length          0018 (24)
│ │ │ │ -C460A Comment Length        0000 (0)
│ │ │ │ -C460C Disk Start            0000 (0)
│ │ │ │ -C460E Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C4610 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C4614 Local Header Offset   0009C33B (639803)
│ │ │ │ -C4618 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC4618: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C4636 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4638   Length              0005 (5)
│ │ │ │ -C463A   Flags               01 (1) 'Modification'
│ │ │ │ -C463B   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C463F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C4641   Length              000B (11)
│ │ │ │ -C4643   Version             01 (1)
│ │ │ │ -C4644   UID Size            04 (4)
│ │ │ │ -C4645   UID                 00000000 (0)
│ │ │ │ -C4649   GID Size            04 (4)
│ │ │ │ -C464A   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C464E CENTRAL HEADER #86    02014B50 (33639248)
│ │ │ │ -C4652 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C4653 Created OS            03 (3) 'Unix'
│ │ │ │ -C4654 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C4655 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C4656 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C4658 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C465A Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C465E CRC                   F5E2129F (4125233823)
│ │ │ │ -C4662 Compressed Size       000016BC (5820)
│ │ │ │ -C4666 Uncompressed Size     000016CD (5837)
│ │ │ │ -C466A Filename Length       0015 (21)
│ │ │ │ -C466C Extra Length          0018 (24)
│ │ │ │ -C466E Comment Length        0000 (0)
│ │ │ │ -C4670 Disk Start            0000 (0)
│ │ │ │ -C4672 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C4674 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C4678 Local Header Offset   000B1681 (726657)
│ │ │ │ -C467C Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC467C: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C4691 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4693   Length              0005 (5)
│ │ │ │ -C4695   Flags               01 (1) 'Modification'
│ │ │ │ -C4696   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C469A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C469C   Length              000B (11)
│ │ │ │ -C469E   Version             01 (1)
│ │ │ │ -C469F   UID Size            04 (4)
│ │ │ │ -C46A0   UID                 00000000 (0)
│ │ │ │ -C46A4   GID Size            04 (4)
│ │ │ │ -C46A5   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C46A9 CENTRAL HEADER #87    02014B50 (33639248)
│ │ │ │ -C46AD Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C46AE Created OS            03 (3) 'Unix'
│ │ │ │ -C46AF Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C46B0 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C46B1 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C46B3 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C46B5 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C46B9 CRC                   F5E2129F (4125233823)
│ │ │ │ -C46BD Compressed Size       000016BC (5820)
│ │ │ │ -C46C1 Uncompressed Size     000016CD (5837)
│ │ │ │ -C46C5 Filename Length       001C (28)
│ │ │ │ -C46C7 Extra Length          0018 (24)
│ │ │ │ -C46C9 Comment Length        0000 (0)
│ │ │ │ -C46CB Disk Start            0000 (0)
│ │ │ │ -C46CD Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C46CF Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C46D3 Local Header Offset   000B2D8C (732556)
│ │ │ │ -C46D7 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC46D7: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C46F3 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C46F5   Length              0005 (5)
│ │ │ │ -C46F7   Flags               01 (1) 'Modification'
│ │ │ │ -C46F8   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C46FC Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C46FE   Length              000B (11)
│ │ │ │ -C4700   Version             01 (1)
│ │ │ │ -C4701   UID Size            04 (4)
│ │ │ │ -C4702   UID                 00000000 (0)
│ │ │ │ -C4706   GID Size            04 (4)
│ │ │ │ -C4707   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C470B CENTRAL HEADER #88    02014B50 (33639248)
│ │ │ │ -C470F Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C4710 Created OS            03 (3) 'Unix'
│ │ │ │ -C4711 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -C4712 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C4713 General Purpose Flag  0000 (0)
│ │ │ │ -C4715 Compression Method    0000 (0) 'Stored'
│ │ │ │ -C4717 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C471B CRC                   FC95F24B (4237685323)
│ │ │ │ -C471F Compressed Size       00001B84 (7044)
│ │ │ │ -C4723 Uncompressed Size     00001B84 (7044)
│ │ │ │ -C4727 Filename Length       0016 (22)
│ │ │ │ -C4729 Extra Length          0018 (24)
│ │ │ │ -C472B Comment Length        0000 (0)
│ │ │ │ -C472D Disk Start            0000 (0)
│ │ │ │ -C472F Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C4731 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C4735 Local Header Offset   000B449E (738462)
│ │ │ │ -C4739 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC4739: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C474F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4751   Length              0005 (5)
│ │ │ │ -C4753   Flags               01 (1) 'Modification'
│ │ │ │ -C4754   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C4758 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C475A   Length              000B (11)
│ │ │ │ -C475C   Version             01 (1)
│ │ │ │ -C475D   UID Size            04 (4)
│ │ │ │ -C475E   UID                 00000000 (0)
│ │ │ │ -C4762   GID Size            04 (4)
│ │ │ │ -C4763   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C4767 CENTRAL HEADER #89    02014B50 (33639248)
│ │ │ │ -C476B Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C476C Created OS            03 (3) 'Unix'
│ │ │ │ -C476D Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -C476E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C476F General Purpose Flag  0000 (0)
│ │ │ │ -C4771 Compression Method    0000 (0) 'Stored'
│ │ │ │ -C4773 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C4777 CRC                   D0D71F86 (3503759238)
│ │ │ │ -C477B Compressed Size       00000B7B (2939)
│ │ │ │ -C477F Uncompressed Size     00000B7B (2939)
│ │ │ │ -C4783 Filename Length       0016 (22)
│ │ │ │ -C4785 Extra Length          0018 (24)
│ │ │ │ -C4787 Comment Length        0000 (0)
│ │ │ │ -C4789 Disk Start            0000 (0)
│ │ │ │ -C478B Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C478D Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C4791 Local Header Offset   000B6072 (745586)
│ │ │ │ -C4795 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC4795: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C47AB Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C47AD   Length              0005 (5)
│ │ │ │ -C47AF   Flags               01 (1) 'Modification'
│ │ │ │ -C47B0   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C47B4 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C47B6   Length              000B (11)
│ │ │ │ -C47B8   Version             01 (1)
│ │ │ │ -C47B9   UID Size            04 (4)
│ │ │ │ -C47BA   UID                 00000000 (0)
│ │ │ │ -C47BE   GID Size            04 (4)
│ │ │ │ -C47BF   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C47C3 CENTRAL HEADER #90    02014B50 (33639248)
│ │ │ │ -C47C7 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C47C8 Created OS            03 (3) 'Unix'
│ │ │ │ -C47C9 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -C47CA Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C47CB General Purpose Flag  0000 (0)
│ │ │ │ -C47CD Compression Method    0000 (0) 'Stored'
│ │ │ │ -C47CF Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C47D3 CRC                   FFF9C4D2 (4294558930)
│ │ │ │ -C47D7 Compressed Size       0000138F (5007)
│ │ │ │ -C47DB Uncompressed Size     0000138F (5007)
│ │ │ │ -C47DF Filename Length       0016 (22)
│ │ │ │ -C47E1 Extra Length          0018 (24)
│ │ │ │ -C47E3 Comment Length        0000 (0)
│ │ │ │ -C47E5 Disk Start            0000 (0)
│ │ │ │ -C47E7 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C47E9 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C47ED Local Header Offset   000B6C3D (748605)
│ │ │ │ -C47F1 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC47F1: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C4807 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4809   Length              0005 (5)
│ │ │ │ -C480B   Flags               01 (1) 'Modification'
│ │ │ │ -C480C   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C4810 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C4812   Length              000B (11)
│ │ │ │ -C4814   Version             01 (1)
│ │ │ │ -C4815   UID Size            04 (4)
│ │ │ │ -C4816   UID                 00000000 (0)
│ │ │ │ -C481A   GID Size            04 (4)
│ │ │ │ -C481B   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C481F CENTRAL HEADER #91    02014B50 (33639248)
│ │ │ │ -C4823 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C4824 Created OS            03 (3) 'Unix'
│ │ │ │ -C4825 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -C4826 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C4827 General Purpose Flag  0000 (0)
│ │ │ │ -C4829 Compression Method    0000 (0) 'Stored'
│ │ │ │ -C482B Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C482F CRC                   A1037E8E (2701360782)
│ │ │ │ -C4833 Compressed Size       0000145E (5214)
│ │ │ │ -C4837 Uncompressed Size     0000145E (5214)
│ │ │ │ -C483B Filename Length       0016 (22)
│ │ │ │ -C483D Extra Length          0018 (24)
│ │ │ │ -C483F Comment Length        0000 (0)
│ │ │ │ -C4841 Disk Start            0000 (0)
│ │ │ │ -C4843 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C4845 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C4849 Local Header Offset   000B801C (753692)
│ │ │ │ -C484D Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC484D: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C4863 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4865   Length              0005 (5)
│ │ │ │ -C4867   Flags               01 (1) 'Modification'
│ │ │ │ -C4868   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C486C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C486E   Length              000B (11)
│ │ │ │ -C4870   Version             01 (1)
│ │ │ │ -C4871   UID Size            04 (4)
│ │ │ │ -C4872   UID                 00000000 (0)
│ │ │ │ -C4876   GID Size            04 (4)
│ │ │ │ -C4877   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C487B CENTRAL HEADER #92    02014B50 (33639248)
│ │ │ │ -C487F Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C4880 Created OS            03 (3) 'Unix'
│ │ │ │ -C4881 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -C4882 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C4883 General Purpose Flag  0000 (0)
│ │ │ │ -C4885 Compression Method    0000 (0) 'Stored'
│ │ │ │ -C4887 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C488B CRC                   5E9E64F1 (1587438833)
│ │ │ │ -C488F Compressed Size       000008EC (2284)
│ │ │ │ -C4893 Uncompressed Size     000008EC (2284)
│ │ │ │ -C4897 Filename Length       0016 (22)
│ │ │ │ -C4899 Extra Length          0018 (24)
│ │ │ │ -C489B Comment Length        0000 (0)
│ │ │ │ -C489D Disk Start            0000 (0)
│ │ │ │ -C489F Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C48A1 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C48A5 Local Header Offset   000B94CA (758986)
│ │ │ │ -C48A9 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC48A9: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C48BF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C48C1   Length              0005 (5)
│ │ │ │ -C48C3   Flags               01 (1) 'Modification'
│ │ │ │ -C48C4   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C48C8 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C48CA   Length              000B (11)
│ │ │ │ -C48CC   Version             01 (1)
│ │ │ │ -C48CD   UID Size            04 (4)
│ │ │ │ -C48CE   UID                 00000000 (0)
│ │ │ │ -C48D2   GID Size            04 (4)
│ │ │ │ -C48D3   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C48D7 CENTRAL HEADER #93    02014B50 (33639248)
│ │ │ │ -C48DB Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C48DC Created OS            03 (3) 'Unix'
│ │ │ │ -C48DD Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -C48DE Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C48DF General Purpose Flag  0000 (0)
│ │ │ │ -C48E1 Compression Method    0000 (0) 'Stored'
│ │ │ │ -C48E3 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C48E7 CRC                   42E340AB (1122189483)
│ │ │ │ -C48EB Compressed Size       00001F2E (7982)
│ │ │ │ -C48EF Uncompressed Size     00001F2E (7982)
│ │ │ │ -C48F3 Filename Length       001E (30)
│ │ │ │ -C48F5 Extra Length          0018 (24)
│ │ │ │ -C48F7 Comment Length        0000 (0)
│ │ │ │ -C48F9 Disk Start            0000 (0)
│ │ │ │ -C48FB Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C48FD Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C4901 Local Header Offset   000B9E06 (761350)
│ │ │ │ -C4905 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC4905: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C4923 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4925   Length              0005 (5)
│ │ │ │ -C4927   Flags               01 (1) 'Modification'
│ │ │ │ -C4928   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C492C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C492E   Length              000B (11)
│ │ │ │ -C4930   Version             01 (1)
│ │ │ │ -C4931   UID Size            04 (4)
│ │ │ │ -C4932   UID                 00000000 (0)
│ │ │ │ -C4936   GID Size            04 (4)
│ │ │ │ -C4937   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C493B CENTRAL HEADER #94    02014B50 (33639248)
│ │ │ │ -C493F Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C4940 Created OS            03 (3) 'Unix'
│ │ │ │ -C4941 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C4942 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C4943 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C4945 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C4947 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C494B CRC                   29EA8E7B (703237755)
│ │ │ │ -C494F Compressed Size       00003D82 (15746)
│ │ │ │ -C4953 Uncompressed Size     000166B0 (91824)
│ │ │ │ -C4957 Filename Length       001A (26)
│ │ │ │ -C4959 Extra Length          0018 (24)
│ │ │ │ -C495B Comment Length        0000 (0)
│ │ │ │ -C495D Disk Start            0000 (0)
│ │ │ │ -C495F Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C4961 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C4965 Local Header Offset   000BBD8C (769420)
│ │ │ │ -C4969 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC4969: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C4983 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4985   Length              0005 (5)
│ │ │ │ -C4987   Flags               01 (1) 'Modification'
│ │ │ │ -C4988   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C498C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C498E   Length              000B (11)
│ │ │ │ -C4990   Version             01 (1)
│ │ │ │ -C4991   UID Size            04 (4)
│ │ │ │ -C4992   UID                 00000000 (0)
│ │ │ │ -C4996   GID Size            04 (4)
│ │ │ │ -C4997   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C499B CENTRAL HEADER #95    02014B50 (33639248)
│ │ │ │ -C499F Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C49A0 Created OS            03 (3) 'Unix'
│ │ │ │ -C49A1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C49A2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C49A3 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C49A5 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C49A7 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C49AB CRC                   207E153D (545133885)
│ │ │ │ -C49AF Compressed Size       000029D2 (10706)
│ │ │ │ -C49B3 Uncompressed Size     0000BB3A (47930)
│ │ │ │ -C49B7 Filename Length       0018 (24)
│ │ │ │ -C49B9 Extra Length          0018 (24)
│ │ │ │ -C49BB Comment Length        0000 (0)
│ │ │ │ -C49BD Disk Start            0000 (0)
│ │ │ │ -C49BF Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C49C1 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C49C5 Local Header Offset   000BFB62 (785250)
│ │ │ │ -C49C9 Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC49C9: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C49E1 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C49E3   Length              0005 (5)
│ │ │ │ -C49E5   Flags               01 (1) 'Modification'
│ │ │ │ -C49E6   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C49EA Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C49EC   Length              000B (11)
│ │ │ │ -C49EE   Version             01 (1)
│ │ │ │ -C49EF   UID Size            04 (4)
│ │ │ │ -C49F0   UID                 00000000 (0)
│ │ │ │ -C49F4   GID Size            04 (4)
│ │ │ │ -C49F5   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C49F9 CENTRAL HEADER #96    02014B50 (33639248)
│ │ │ │ -C49FD Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C49FE Created OS            03 (3) 'Unix'
│ │ │ │ -C49FF Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C4A00 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C4A01 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C4A03 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C4A05 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C4A09 CRC                   DCB3B516 (3702764822)
│ │ │ │ -C4A0D Compressed Size       000000AE (174)
│ │ │ │ -C4A11 Uncompressed Size     000000FC (252)
│ │ │ │ -C4A15 Filename Length       0016 (22)
│ │ │ │ -C4A17 Extra Length          0018 (24)
│ │ │ │ -C4A19 Comment Length        0000 (0)
│ │ │ │ -C4A1B Disk Start            0000 (0)
│ │ │ │ -C4A1D Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C4A1F Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C4A23 Local Header Offset   000C2586 (796038)
│ │ │ │ -C4A27 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC4A27: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C4A3D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4A3F   Length              0005 (5)
│ │ │ │ -C4A41   Flags               01 (1) 'Modification'
│ │ │ │ -C4A42   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C4A46 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C4A48   Length              000B (11)
│ │ │ │ -C4A4A   Version             01 (1)
│ │ │ │ -C4A4B   UID Size            04 (4)
│ │ │ │ -C4A4C   UID                 00000000 (0)
│ │ │ │ -C4A50   GID Size            04 (4)
│ │ │ │ -C4A51   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C4A55 CENTRAL HEADER #97    02014B50 (33639248)
│ │ │ │ -C4A59 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -C4A5A Created OS            03 (3) 'Unix'
│ │ │ │ -C4A5B Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -C4A5C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -C4A5D General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -C4A5F Compression Method    0008 (8) 'Deflated'
│ │ │ │ -C4A61 Modification Time     5C8FA0E4 (1552916708) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C4A65 CRC                   58439733 (1480824627)
│ │ │ │ -C4A69 Compressed Size       00000077 (119)
│ │ │ │ -C4A6D Uncompressed Size     000000A2 (162)
│ │ │ │ -C4A71 Filename Length       002D (45)
│ │ │ │ -C4A73 Extra Length          0018 (24)
│ │ │ │ -C4A75 Comment Length        0000 (0)
│ │ │ │ -C4A77 Disk Start            0000 (0)
│ │ │ │ -C4A79 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -C4A7B Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -C4A7F Local Header Offset   000C2684 (796292)
│ │ │ │ -C4A83 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC4A83: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -C4AB0 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -C4AB2   Length              0005 (5)
│ │ │ │ -C4AB4   Flags               01 (1) 'Modification'
│ │ │ │ -C4AB5   Modification Time   69DFEFEC (1776283628) 'Wed Apr 15 20:07:08 2026'
│ │ │ │ -C4AB9 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -C4ABB   Length              000B (11)
│ │ │ │ -C4ABD   Version             01 (1)
│ │ │ │ -C4ABE   UID Size            04 (4)
│ │ │ │ -C4ABF   UID                 00000000 (0)
│ │ │ │ -C4AC3   GID Size            04 (4)
│ │ │ │ -C4AC4   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -C4AC8 END CENTRAL HEADER    06054B50 (101010256)
│ │ │ │ -C4ACC Number of this disk   0000 (0)
│ │ │ │ -C4ACE Central Dir Disk no   0000 (0)
│ │ │ │ -C4AD0 Entries in this disk  0061 (97)
│ │ │ │ -C4AD2 Total Entries         0061 (97)
│ │ │ │ -C4AD4 Size of Central Dir   00002366 (9062)
│ │ │ │ -C4AD8 Offset to Central Dir 000C2762 (796514)
│ │ │ │ -C4ADC Comment Length        0000 (0)
│ │ │ │ +C2692 LOCAL HEADER #97      04034B50 (67324752)
│ │ │ │ +C2696 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2697 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2698 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C269A Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C269C Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C26A0 CRC                   58439733 (1480824627)
│ │ │ │ +C26A4 Compressed Size       00000077 (119)
│ │ │ │ +C26A8 Uncompressed Size     000000A2 (162)
│ │ │ │ +C26AC Filename Length       002D (45)
│ │ │ │ +C26AE Extra Length          001C (28)
│ │ │ │ +C26B0 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC26B0: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C26DD Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C26DF   Length              0009 (9)
│ │ │ │ +C26E1   Flags               03 (3) 'Modification Access'
│ │ │ │ +C26E2   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C26E6   Access Time         69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C26EA Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C26EC   Length              000B (11)
│ │ │ │ +C26EE   Version             01 (1)
│ │ │ │ +C26EF   UID Size            04 (4)
│ │ │ │ +C26F0   UID                 00000000 (0)
│ │ │ │ +C26F4   GID Size            04 (4)
│ │ │ │ +C26F5   GID                 00000000 (0)
│ │ │ │ +C26F9 PAYLOAD               XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
│ │ │ │ +
│ │ │ │ +C2770 CENTRAL HEADER #1     02014B50 (33639248)
│ │ │ │ +C2774 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2775 Created OS            03 (3) 'Unix'
│ │ │ │ +C2776 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ +C2777 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2778 General Purpose Flag  0000 (0)
│ │ │ │ +C277A Compression Method    0000 (0) 'Stored'
│ │ │ │ +C277C Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2780 CRC                   2CAB616F (749429103)
│ │ │ │ +C2784 Compressed Size       00000014 (20)
│ │ │ │ +C2788 Uncompressed Size     00000014 (20)
│ │ │ │ +C278C Filename Length       0008 (8)
│ │ │ │ +C278E Extra Length          0018 (24)
│ │ │ │ +C2790 Comment Length        0000 (0)
│ │ │ │ +C2792 Disk Start            0000 (0)
│ │ │ │ +C2794 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2796 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C279A Local Header Offset   00000000 (0)
│ │ │ │ +C279E Filename              'XXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC279E: Filename 'XXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C27A6 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C27A8   Length              0005 (5)
│ │ │ │ +C27AA   Flags               01 (1) 'Modification'
│ │ │ │ +C27AB   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C27AF Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C27B1   Length              000B (11)
│ │ │ │ +C27B3   Version             01 (1)
│ │ │ │ +C27B4   UID Size            04 (4)
│ │ │ │ +C27B5   UID                 00000000 (0)
│ │ │ │ +C27B9   GID Size            04 (4)
│ │ │ │ +C27BA   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C27BE CENTRAL HEADER #2     02014B50 (33639248)
│ │ │ │ +C27C2 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C27C3 Created OS            03 (3) 'Unix'
│ │ │ │ +C27C4 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C27C5 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C27C6 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C27C8 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C27CA Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C27CE CRC                   53A58720 (1403356960)
│ │ │ │ +C27D2 Compressed Size       00000D22 (3362)
│ │ │ │ +C27D6 Uncompressed Size     00003933 (14643)
│ │ │ │ +C27DA Filename Length       001B (27)
│ │ │ │ +C27DC Extra Length          0018 (24)
│ │ │ │ +C27DE Comment Length        0000 (0)
│ │ │ │ +C27E0 Disk Start            0000 (0)
│ │ │ │ +C27E2 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C27E4 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C27E8 Local Header Offset   00000056 (86)
│ │ │ │ +C27EC Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC27EC: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2807 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2809   Length              0005 (5)
│ │ │ │ +C280B   Flags               01 (1) 'Modification'
│ │ │ │ +C280C   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2810 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2812   Length              000B (11)
│ │ │ │ +C2814   Version             01 (1)
│ │ │ │ +C2815   UID Size            04 (4)
│ │ │ │ +C2816   UID                 00000000 (0)
│ │ │ │ +C281A   GID Size            04 (4)
│ │ │ │ +C281B   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C281F CENTRAL HEADER #3     02014B50 (33639248)
│ │ │ │ +C2823 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2824 Created OS            03 (3) 'Unix'
│ │ │ │ +C2825 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2826 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2827 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2829 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C282B Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C282F CRC                   546A35FD (1416246781)
│ │ │ │ +C2833 Compressed Size       000015B1 (5553)
│ │ │ │ +C2837 Uncompressed Size     00004605 (17925)
│ │ │ │ +C283B Filename Length       0014 (20)
│ │ │ │ +C283D Extra Length          0018 (24)
│ │ │ │ +C283F Comment Length        0000 (0)
│ │ │ │ +C2841 Disk Start            0000 (0)
│ │ │ │ +C2843 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2845 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2849 Local Header Offset   00000DCD (3533)
│ │ │ │ +C284D Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC284D: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2861 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2863   Length              0005 (5)
│ │ │ │ +C2865   Flags               01 (1) 'Modification'
│ │ │ │ +C2866   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C286A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C286C   Length              000B (11)
│ │ │ │ +C286E   Version             01 (1)
│ │ │ │ +C286F   UID Size            04 (4)
│ │ │ │ +C2870   UID                 00000000 (0)
│ │ │ │ +C2874   GID Size            04 (4)
│ │ │ │ +C2875   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2879 CENTRAL HEADER #4     02014B50 (33639248)
│ │ │ │ +C287D Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C287E Created OS            03 (3) 'Unix'
│ │ │ │ +C287F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2880 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2881 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2883 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2885 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2889 CRC                   03A4A46E (61121646)
│ │ │ │ +C288D Compressed Size       000006D4 (1748)
│ │ │ │ +C2891 Uncompressed Size     00001241 (4673)
│ │ │ │ +C2895 Filename Length       0013 (19)
│ │ │ │ +C2897 Extra Length          0018 (24)
│ │ │ │ +C2899 Comment Length        0000 (0)
│ │ │ │ +C289B Disk Start            0000 (0)
│ │ │ │ +C289D Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C289F Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C28A3 Local Header Offset   000023CC (9164)
│ │ │ │ +C28A7 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC28A7: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C28BA Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C28BC   Length              0005 (5)
│ │ │ │ +C28BE   Flags               01 (1) 'Modification'
│ │ │ │ +C28BF   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C28C3 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C28C5   Length              000B (11)
│ │ │ │ +C28C7   Version             01 (1)
│ │ │ │ +C28C8   UID Size            04 (4)
│ │ │ │ +C28C9   UID                 00000000 (0)
│ │ │ │ +C28CD   GID Size            04 (4)
│ │ │ │ +C28CE   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C28D2 CENTRAL HEADER #5     02014B50 (33639248)
│ │ │ │ +C28D6 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C28D7 Created OS            03 (3) 'Unix'
│ │ │ │ +C28D8 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C28D9 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C28DA General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C28DC Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C28DE Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C28E2 CRC                   69D3269E (1775445662)
│ │ │ │ +C28E6 Compressed Size       00002E70 (11888)
│ │ │ │ +C28EA Uncompressed Size     0000D4C1 (54465)
│ │ │ │ +C28EE Filename Length       0014 (20)
│ │ │ │ +C28F0 Extra Length          0018 (24)
│ │ │ │ +C28F2 Comment Length        0000 (0)
│ │ │ │ +C28F4 Disk Start            0000 (0)
│ │ │ │ +C28F6 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C28F8 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C28FC Local Header Offset   00002AED (10989)
│ │ │ │ +C2900 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2900: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2914 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2916   Length              0005 (5)
│ │ │ │ +C2918   Flags               01 (1) 'Modification'
│ │ │ │ +C2919   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C291D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C291F   Length              000B (11)
│ │ │ │ +C2921   Version             01 (1)
│ │ │ │ +C2922   UID Size            04 (4)
│ │ │ │ +C2923   UID                 00000000 (0)
│ │ │ │ +C2927   GID Size            04 (4)
│ │ │ │ +C2928   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C292C CENTRAL HEADER #6     02014B50 (33639248)
│ │ │ │ +C2930 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2931 Created OS            03 (3) 'Unix'
│ │ │ │ +C2932 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2933 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2934 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2936 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2938 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C293C CRC                   272DD323 (657314595)
│ │ │ │ +C2940 Compressed Size       000003EF (1007)
│ │ │ │ +C2944 Uncompressed Size     00000876 (2166)
│ │ │ │ +C2948 Filename Length       0014 (20)
│ │ │ │ +C294A Extra Length          0018 (24)
│ │ │ │ +C294C Comment Length        0000 (0)
│ │ │ │ +C294E Disk Start            0000 (0)
│ │ │ │ +C2950 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2952 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2956 Local Header Offset   000059AB (22955)
│ │ │ │ +C295A Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC295A: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C296E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2970   Length              0005 (5)
│ │ │ │ +C2972   Flags               01 (1) 'Modification'
│ │ │ │ +C2973   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2977 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2979   Length              000B (11)
│ │ │ │ +C297B   Version             01 (1)
│ │ │ │ +C297C   UID Size            04 (4)
│ │ │ │ +C297D   UID                 00000000 (0)
│ │ │ │ +C2981   GID Size            04 (4)
│ │ │ │ +C2982   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2986 CENTRAL HEADER #7     02014B50 (33639248)
│ │ │ │ +C298A Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C298B Created OS            03 (3) 'Unix'
│ │ │ │ +C298C Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C298D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C298E General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2990 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2992 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2996 CRC                   2F07766F (789018223)
│ │ │ │ +C299A Compressed Size       000001AD (429)
│ │ │ │ +C299E Uncompressed Size     000002FC (764)
│ │ │ │ +C29A2 Filename Length       0011 (17)
│ │ │ │ +C29A4 Extra Length          0018 (24)
│ │ │ │ +C29A6 Comment Length        0000 (0)
│ │ │ │ +C29A8 Disk Start            0000 (0)
│ │ │ │ +C29AA Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C29AC Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C29B0 Local Header Offset   00005DE8 (24040)
│ │ │ │ +C29B4 Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC29B4: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C29C5 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C29C7   Length              0005 (5)
│ │ │ │ +C29C9   Flags               01 (1) 'Modification'
│ │ │ │ +C29CA   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C29CE Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C29D0   Length              000B (11)
│ │ │ │ +C29D2   Version             01 (1)
│ │ │ │ +C29D3   UID Size            04 (4)
│ │ │ │ +C29D4   UID                 00000000 (0)
│ │ │ │ +C29D8   GID Size            04 (4)
│ │ │ │ +C29D9   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C29DD CENTRAL HEADER #8     02014B50 (33639248)
│ │ │ │ +C29E1 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C29E2 Created OS            03 (3) 'Unix'
│ │ │ │ +C29E3 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C29E4 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C29E5 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C29E7 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C29E9 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C29ED CRC                   2E830899 (780339353)
│ │ │ │ +C29F1 Compressed Size       000020BD (8381)
│ │ │ │ +C29F5 Uncompressed Size     0000B4B1 (46257)
│ │ │ │ +C29F9 Filename Length       001B (27)
│ │ │ │ +C29FB Extra Length          0018 (24)
│ │ │ │ +C29FD Comment Length        0000 (0)
│ │ │ │ +C29FF Disk Start            0000 (0)
│ │ │ │ +C2A01 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2A03 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2A07 Local Header Offset   00005FE0 (24544)
│ │ │ │ +C2A0B Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2A0B: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2A26 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2A28   Length              0005 (5)
│ │ │ │ +C2A2A   Flags               01 (1) 'Modification'
│ │ │ │ +C2A2B   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2A2F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2A31   Length              000B (11)
│ │ │ │ +C2A33   Version             01 (1)
│ │ │ │ +C2A34   UID Size            04 (4)
│ │ │ │ +C2A35   UID                 00000000 (0)
│ │ │ │ +C2A39   GID Size            04 (4)
│ │ │ │ +C2A3A   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2A3E CENTRAL HEADER #9     02014B50 (33639248)
│ │ │ │ +C2A42 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2A43 Created OS            03 (3) 'Unix'
│ │ │ │ +C2A44 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2A45 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2A46 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2A48 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2A4A Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2A4E CRC                   4E72FA06 (1316157958)
│ │ │ │ +C2A52 Compressed Size       00000E68 (3688)
│ │ │ │ +C2A56 Uncompressed Size     00003097 (12439)
│ │ │ │ +C2A5A Filename Length       001D (29)
│ │ │ │ +C2A5C Extra Length          0018 (24)
│ │ │ │ +C2A5E Comment Length        0000 (0)
│ │ │ │ +C2A60 Disk Start            0000 (0)
│ │ │ │ +C2A62 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2A64 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2A68 Local Header Offset   000080F2 (33010)
│ │ │ │ +C2A6C Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2A6C: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2A89 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2A8B   Length              0005 (5)
│ │ │ │ +C2A8D   Flags               01 (1) 'Modification'
│ │ │ │ +C2A8E   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2A92 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2A94   Length              000B (11)
│ │ │ │ +C2A96   Version             01 (1)
│ │ │ │ +C2A97   UID Size            04 (4)
│ │ │ │ +C2A98   UID                 00000000 (0)
│ │ │ │ +C2A9C   GID Size            04 (4)
│ │ │ │ +C2A9D   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2AA1 CENTRAL HEADER #10    02014B50 (33639248)
│ │ │ │ +C2AA5 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2AA6 Created OS            03 (3) 'Unix'
│ │ │ │ +C2AA7 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2AA8 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2AA9 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2AAB Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2AAD Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2AB1 CRC                   F138337A (4046992250)
│ │ │ │ +C2AB5 Compressed Size       0000098E (2446)
│ │ │ │ +C2AB9 Uncompressed Size     00001D39 (7481)
│ │ │ │ +C2ABD Filename Length       0019 (25)
│ │ │ │ +C2ABF Extra Length          0018 (24)
│ │ │ │ +C2AC1 Comment Length        0000 (0)
│ │ │ │ +C2AC3 Disk Start            0000 (0)
│ │ │ │ +C2AC5 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2AC7 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2ACB Local Header Offset   00008FB1 (36785)
│ │ │ │ +C2ACF Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2ACF: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2AE8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2AEA   Length              0005 (5)
│ │ │ │ +C2AEC   Flags               01 (1) 'Modification'
│ │ │ │ +C2AED   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2AF1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2AF3   Length              000B (11)
│ │ │ │ +C2AF5   Version             01 (1)
│ │ │ │ +C2AF6   UID Size            04 (4)
│ │ │ │ +C2AF7   UID                 00000000 (0)
│ │ │ │ +C2AFB   GID Size            04 (4)
│ │ │ │ +C2AFC   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2B00 CENTRAL HEADER #11    02014B50 (33639248)
│ │ │ │ +C2B04 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2B05 Created OS            03 (3) 'Unix'
│ │ │ │ +C2B06 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2B07 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2B08 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2B0A Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2B0C Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2B10 CRC                   42AE2C47 (1118710855)
│ │ │ │ +C2B14 Compressed Size       00003887 (14471)
│ │ │ │ +C2B18 Uncompressed Size     0000F81F (63519)
│ │ │ │ +C2B1C Filename Length       0015 (21)
│ │ │ │ +C2B1E Extra Length          0018 (24)
│ │ │ │ +C2B20 Comment Length        0000 (0)
│ │ │ │ +C2B22 Disk Start            0000 (0)
│ │ │ │ +C2B24 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2B26 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2B2A Local Header Offset   00009992 (39314)
│ │ │ │ +C2B2E Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2B2E: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2B43 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2B45   Length              0005 (5)
│ │ │ │ +C2B47   Flags               01 (1) 'Modification'
│ │ │ │ +C2B48   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2B4C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2B4E   Length              000B (11)
│ │ │ │ +C2B50   Version             01 (1)
│ │ │ │ +C2B51   UID Size            04 (4)
│ │ │ │ +C2B52   UID                 00000000 (0)
│ │ │ │ +C2B56   GID Size            04 (4)
│ │ │ │ +C2B57   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2B5B CENTRAL HEADER #12    02014B50 (33639248)
│ │ │ │ +C2B5F Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2B60 Created OS            03 (3) 'Unix'
│ │ │ │ +C2B61 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2B62 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2B63 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2B65 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2B67 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2B6B CRC                   BCFA2578 (3170510200)
│ │ │ │ +C2B6F Compressed Size       0000AB01 (43777)
│ │ │ │ +C2B73 Uncompressed Size     0003E0D8 (254168)
│ │ │ │ +C2B77 Filename Length       0012 (18)
│ │ │ │ +C2B79 Extra Length          0018 (24)
│ │ │ │ +C2B7B Comment Length        0000 (0)
│ │ │ │ +C2B7D Disk Start            0000 (0)
│ │ │ │ +C2B7F Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2B81 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2B85 Local Header Offset   0000D268 (53864)
│ │ │ │ +C2B89 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2B89: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2B9B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2B9D   Length              0005 (5)
│ │ │ │ +C2B9F   Flags               01 (1) 'Modification'
│ │ │ │ +C2BA0   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2BA4 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2BA6   Length              000B (11)
│ │ │ │ +C2BA8   Version             01 (1)
│ │ │ │ +C2BA9   UID Size            04 (4)
│ │ │ │ +C2BAA   UID                 00000000 (0)
│ │ │ │ +C2BAE   GID Size            04 (4)
│ │ │ │ +C2BAF   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2BB3 CENTRAL HEADER #13    02014B50 (33639248)
│ │ │ │ +C2BB7 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2BB8 Created OS            03 (3) 'Unix'
│ │ │ │ +C2BB9 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2BBA Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2BBB General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2BBD Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2BBF Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2BC3 CRC                   52E3F286 (1390670470)
│ │ │ │ +C2BC7 Compressed Size       00003AF8 (15096)
│ │ │ │ +C2BCB Uncompressed Size     0001B421 (111649)
│ │ │ │ +C2BCF Filename Length       0015 (21)
│ │ │ │ +C2BD1 Extra Length          0018 (24)
│ │ │ │ +C2BD3 Comment Length        0000 (0)
│ │ │ │ +C2BD5 Disk Start            0000 (0)
│ │ │ │ +C2BD7 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2BD9 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2BDD Local Header Offset   00017DB5 (97717)
│ │ │ │ +C2BE1 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2BE1: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2BF6 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2BF8   Length              0005 (5)
│ │ │ │ +C2BFA   Flags               01 (1) 'Modification'
│ │ │ │ +C2BFB   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2BFF Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2C01   Length              000B (11)
│ │ │ │ +C2C03   Version             01 (1)
│ │ │ │ +C2C04   UID Size            04 (4)
│ │ │ │ +C2C05   UID                 00000000 (0)
│ │ │ │ +C2C09   GID Size            04 (4)
│ │ │ │ +C2C0A   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2C0E CENTRAL HEADER #14    02014B50 (33639248)
│ │ │ │ +C2C12 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2C13 Created OS            03 (3) 'Unix'
│ │ │ │ +C2C14 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2C15 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2C16 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2C18 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2C1A Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2C1E CRC                   DBC5E740 (3687180096)
│ │ │ │ +C2C22 Compressed Size       000091CA (37322)
│ │ │ │ +C2C26 Uncompressed Size     0003DBD1 (252881)
│ │ │ │ +C2C2A Filename Length       0014 (20)
│ │ │ │ +C2C2C Extra Length          0018 (24)
│ │ │ │ +C2C2E Comment Length        0000 (0)
│ │ │ │ +C2C30 Disk Start            0000 (0)
│ │ │ │ +C2C32 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2C34 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2C38 Local Header Offset   0001B8FC (112892)
│ │ │ │ +C2C3C Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2C3C: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2C50 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2C52   Length              0005 (5)
│ │ │ │ +C2C54   Flags               01 (1) 'Modification'
│ │ │ │ +C2C55   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2C59 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2C5B   Length              000B (11)
│ │ │ │ +C2C5D   Version             01 (1)
│ │ │ │ +C2C5E   UID Size            04 (4)
│ │ │ │ +C2C5F   UID                 00000000 (0)
│ │ │ │ +C2C63   GID Size            04 (4)
│ │ │ │ +C2C64   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2C68 CENTRAL HEADER #15    02014B50 (33639248)
│ │ │ │ +C2C6C Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2C6D Created OS            03 (3) 'Unix'
│ │ │ │ +C2C6E Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2C6F Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2C70 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2C72 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2C74 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2C78 CRC                   953AA54E (2503648590)
│ │ │ │ +C2C7C Compressed Size       00009BA8 (39848)
│ │ │ │ +C2C80 Uncompressed Size     00027CF5 (163061)
│ │ │ │ +C2C84 Filename Length       0019 (25)
│ │ │ │ +C2C86 Extra Length          0018 (24)
│ │ │ │ +C2C88 Comment Length        0000 (0)
│ │ │ │ +C2C8A Disk Start            0000 (0)
│ │ │ │ +C2C8C Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2C8E Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2C92 Local Header Offset   00024B14 (150292)
│ │ │ │ +C2C96 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2C96: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2CAF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2CB1   Length              0005 (5)
│ │ │ │ +C2CB3   Flags               01 (1) 'Modification'
│ │ │ │ +C2CB4   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2CB8 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2CBA   Length              000B (11)
│ │ │ │ +C2CBC   Version             01 (1)
│ │ │ │ +C2CBD   UID Size            04 (4)
│ │ │ │ +C2CBE   UID                 00000000 (0)
│ │ │ │ +C2CC2   GID Size            04 (4)
│ │ │ │ +C2CC3   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2CC7 CENTRAL HEADER #16    02014B50 (33639248)
│ │ │ │ +C2CCB Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2CCC Created OS            03 (3) 'Unix'
│ │ │ │ +C2CCD Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2CCE Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2CCF General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2CD1 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2CD3 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2CD7 CRC                   36D4AE72 (919907954)
│ │ │ │ +C2CDB Compressed Size       00001219 (4633)
│ │ │ │ +C2CDF Uncompressed Size     00003C91 (15505)
│ │ │ │ +C2CE3 Filename Length       0010 (16)
│ │ │ │ +C2CE5 Extra Length          0018 (24)
│ │ │ │ +C2CE7 Comment Length        0000 (0)
│ │ │ │ +C2CE9 Disk Start            0000 (0)
│ │ │ │ +C2CEB Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2CED Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2CF1 Local Header Offset   0002E70F (190223)
│ │ │ │ +C2CF5 Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2CF5: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2D05 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2D07   Length              0005 (5)
│ │ │ │ +C2D09   Flags               01 (1) 'Modification'
│ │ │ │ +C2D0A   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2D0E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2D10   Length              000B (11)
│ │ │ │ +C2D12   Version             01 (1)
│ │ │ │ +C2D13   UID Size            04 (4)
│ │ │ │ +C2D14   UID                 00000000 (0)
│ │ │ │ +C2D18   GID Size            04 (4)
│ │ │ │ +C2D19   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2D1D CENTRAL HEADER #17    02014B50 (33639248)
│ │ │ │ +C2D21 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2D22 Created OS            03 (3) 'Unix'
│ │ │ │ +C2D23 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2D24 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2D25 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2D27 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2D29 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2D2D CRC                   6E6B7F3A (1852538682)
│ │ │ │ +C2D31 Compressed Size       00002A60 (10848)
│ │ │ │ +C2D35 Uncompressed Size     000113A7 (70567)
│ │ │ │ +C2D39 Filename Length       0016 (22)
│ │ │ │ +C2D3B Extra Length          0018 (24)
│ │ │ │ +C2D3D Comment Length        0000 (0)
│ │ │ │ +C2D3F Disk Start            0000 (0)
│ │ │ │ +C2D41 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2D43 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2D47 Local Header Offset   0002F972 (194930)
│ │ │ │ +C2D4B Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2D4B: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2D61 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2D63   Length              0005 (5)
│ │ │ │ +C2D65   Flags               01 (1) 'Modification'
│ │ │ │ +C2D66   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2D6A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2D6C   Length              000B (11)
│ │ │ │ +C2D6E   Version             01 (1)
│ │ │ │ +C2D6F   UID Size            04 (4)
│ │ │ │ +C2D70   UID                 00000000 (0)
│ │ │ │ +C2D74   GID Size            04 (4)
│ │ │ │ +C2D75   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2D79 CENTRAL HEADER #18    02014B50 (33639248)
│ │ │ │ +C2D7D Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2D7E Created OS            03 (3) 'Unix'
│ │ │ │ +C2D7F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2D80 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2D81 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2D83 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2D85 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2D89 CRC                   EC084A66 (3959966310)
│ │ │ │ +C2D8D Compressed Size       000014D8 (5336)
│ │ │ │ +C2D91 Uncompressed Size     0000518D (20877)
│ │ │ │ +C2D95 Filename Length       001D (29)
│ │ │ │ +C2D97 Extra Length          0018 (24)
│ │ │ │ +C2D99 Comment Length        0000 (0)
│ │ │ │ +C2D9B Disk Start            0000 (0)
│ │ │ │ +C2D9D Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2D9F Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2DA3 Local Header Offset   00032422 (205858)
│ │ │ │ +C2DA7 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2DA7: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2DC4 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2DC6   Length              0005 (5)
│ │ │ │ +C2DC8   Flags               01 (1) 'Modification'
│ │ │ │ +C2DC9   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2DCD Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2DCF   Length              000B (11)
│ │ │ │ +C2DD1   Version             01 (1)
│ │ │ │ +C2DD2   UID Size            04 (4)
│ │ │ │ +C2DD3   UID                 00000000 (0)
│ │ │ │ +C2DD7   GID Size            04 (4)
│ │ │ │ +C2DD8   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2DDC CENTRAL HEADER #19    02014B50 (33639248)
│ │ │ │ +C2DE0 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2DE1 Created OS            03 (3) 'Unix'
│ │ │ │ +C2DE2 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2DE3 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2DE4 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2DE6 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2DE8 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2DEC CRC                   C2410B8F (3259042703)
│ │ │ │ +C2DF0 Compressed Size       00003805 (14341)
│ │ │ │ +C2DF4 Uncompressed Size     0000EA4B (59979)
│ │ │ │ +C2DF8 Filename Length       001C (28)
│ │ │ │ +C2DFA Extra Length          0018 (24)
│ │ │ │ +C2DFC Comment Length        0000 (0)
│ │ │ │ +C2DFE Disk Start            0000 (0)
│ │ │ │ +C2E00 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2E02 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2E06 Local Header Offset   00033951 (211281)
│ │ │ │ +C2E0A Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2E0A: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2E26 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2E28   Length              0005 (5)
│ │ │ │ +C2E2A   Flags               01 (1) 'Modification'
│ │ │ │ +C2E2B   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2E2F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2E31   Length              000B (11)
│ │ │ │ +C2E33   Version             01 (1)
│ │ │ │ +C2E34   UID Size            04 (4)
│ │ │ │ +C2E35   UID                 00000000 (0)
│ │ │ │ +C2E39   GID Size            04 (4)
│ │ │ │ +C2E3A   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2E3E CENTRAL HEADER #20    02014B50 (33639248)
│ │ │ │ +C2E42 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2E43 Created OS            03 (3) 'Unix'
│ │ │ │ +C2E44 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2E45 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2E46 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2E48 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2E4A Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2E4E CRC                   958EC234 (2509161012)
│ │ │ │ +C2E52 Compressed Size       0000069E (1694)
│ │ │ │ +C2E56 Uncompressed Size     000011F3 (4595)
│ │ │ │ +C2E5A Filename Length       001C (28)
│ │ │ │ +C2E5C Extra Length          0018 (24)
│ │ │ │ +C2E5E Comment Length        0000 (0)
│ │ │ │ +C2E60 Disk Start            0000 (0)
│ │ │ │ +C2E62 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2E64 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2E68 Local Header Offset   000371AC (225708)
│ │ │ │ +C2E6C Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2E6C: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2E88 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2E8A   Length              0005 (5)
│ │ │ │ +C2E8C   Flags               01 (1) 'Modification'
│ │ │ │ +C2E8D   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2E91 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2E93   Length              000B (11)
│ │ │ │ +C2E95   Version             01 (1)
│ │ │ │ +C2E96   UID Size            04 (4)
│ │ │ │ +C2E97   UID                 00000000 (0)
│ │ │ │ +C2E9B   GID Size            04 (4)
│ │ │ │ +C2E9C   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2EA0 CENTRAL HEADER #21    02014B50 (33639248)
│ │ │ │ +C2EA4 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2EA5 Created OS            03 (3) 'Unix'
│ │ │ │ +C2EA6 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2EA7 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2EA8 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2EAA Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2EAC Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2EB0 CRC                   EE3DA990 (3997018512)
│ │ │ │ +C2EB4 Compressed Size       0000107C (4220)
│ │ │ │ +C2EB8 Uncompressed Size     00004BFE (19454)
│ │ │ │ +C2EBC Filename Length       001B (27)
│ │ │ │ +C2EBE Extra Length          0018 (24)
│ │ │ │ +C2EC0 Comment Length        0000 (0)
│ │ │ │ +C2EC2 Disk Start            0000 (0)
│ │ │ │ +C2EC4 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2EC6 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2ECA Local Header Offset   000378A0 (227488)
│ │ │ │ +C2ECE Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2ECE: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2EE9 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2EEB   Length              0005 (5)
│ │ │ │ +C2EED   Flags               01 (1) 'Modification'
│ │ │ │ +C2EEE   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2EF2 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2EF4   Length              000B (11)
│ │ │ │ +C2EF6   Version             01 (1)
│ │ │ │ +C2EF7   UID Size            04 (4)
│ │ │ │ +C2EF8   UID                 00000000 (0)
│ │ │ │ +C2EFC   GID Size            04 (4)
│ │ │ │ +C2EFD   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2F01 CENTRAL HEADER #22    02014B50 (33639248)
│ │ │ │ +C2F05 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2F06 Created OS            03 (3) 'Unix'
│ │ │ │ +C2F07 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2F08 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2F09 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2F0B Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2F0D Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2F11 CRC                   045E51FF (73290239)
│ │ │ │ +C2F15 Compressed Size       00003B3B (15163)
│ │ │ │ +C2F19 Uncompressed Size     0000D491 (54417)
│ │ │ │ +C2F1D Filename Length       001D (29)
│ │ │ │ +C2F1F Extra Length          0018 (24)
│ │ │ │ +C2F21 Comment Length        0000 (0)
│ │ │ │ +C2F23 Disk Start            0000 (0)
│ │ │ │ +C2F25 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2F27 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2F2B Local Header Offset   00038971 (231793)
│ │ │ │ +C2F2F Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2F2F: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2F4C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2F4E   Length              0005 (5)
│ │ │ │ +C2F50   Flags               01 (1) 'Modification'
│ │ │ │ +C2F51   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2F55 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2F57   Length              000B (11)
│ │ │ │ +C2F59   Version             01 (1)
│ │ │ │ +C2F5A   UID Size            04 (4)
│ │ │ │ +C2F5B   UID                 00000000 (0)
│ │ │ │ +C2F5F   GID Size            04 (4)
│ │ │ │ +C2F60   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2F64 CENTRAL HEADER #23    02014B50 (33639248)
│ │ │ │ +C2F68 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2F69 Created OS            03 (3) 'Unix'
│ │ │ │ +C2F6A Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2F6B Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2F6C General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2F6E Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2F70 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2F74 CRC                   C52CC238 (3308044856)
│ │ │ │ +C2F78 Compressed Size       00000D6A (3434)
│ │ │ │ +C2F7C Uncompressed Size     0000388A (14474)
│ │ │ │ +C2F80 Filename Length       001D (29)
│ │ │ │ +C2F82 Extra Length          0018 (24)
│ │ │ │ +C2F84 Comment Length        0000 (0)
│ │ │ │ +C2F86 Disk Start            0000 (0)
│ │ │ │ +C2F88 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2F8A Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2F8E Local Header Offset   0003C503 (247043)
│ │ │ │ +C2F92 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2F92: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C2FAF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C2FB1   Length              0005 (5)
│ │ │ │ +C2FB3   Flags               01 (1) 'Modification'
│ │ │ │ +C2FB4   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C2FB8 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C2FBA   Length              000B (11)
│ │ │ │ +C2FBC   Version             01 (1)
│ │ │ │ +C2FBD   UID Size            04 (4)
│ │ │ │ +C2FBE   UID                 00000000 (0)
│ │ │ │ +C2FC2   GID Size            04 (4)
│ │ │ │ +C2FC3   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C2FC7 CENTRAL HEADER #24    02014B50 (33639248)
│ │ │ │ +C2FCB Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C2FCC Created OS            03 (3) 'Unix'
│ │ │ │ +C2FCD Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C2FCE Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C2FCF General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C2FD1 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C2FD3 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C2FD7 CRC                   0BFFA3F1 (201303025)
│ │ │ │ +C2FDB Compressed Size       00001C89 (7305)
│ │ │ │ +C2FDF Uncompressed Size     0000C038 (49208)
│ │ │ │ +C2FE3 Filename Length       001A (26)
│ │ │ │ +C2FE5 Extra Length          0018 (24)
│ │ │ │ +C2FE7 Comment Length        0000 (0)
│ │ │ │ +C2FE9 Disk Start            0000 (0)
│ │ │ │ +C2FEB Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C2FED Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C2FF1 Local Header Offset   0003D2C4 (250564)
│ │ │ │ +C2FF5 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC2FF5: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C300F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3011   Length              0005 (5)
│ │ │ │ +C3013   Flags               01 (1) 'Modification'
│ │ │ │ +C3014   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3018 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C301A   Length              000B (11)
│ │ │ │ +C301C   Version             01 (1)
│ │ │ │ +C301D   UID Size            04 (4)
│ │ │ │ +C301E   UID                 00000000 (0)
│ │ │ │ +C3022   GID Size            04 (4)
│ │ │ │ +C3023   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3027 CENTRAL HEADER #25    02014B50 (33639248)
│ │ │ │ +C302B Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C302C Created OS            03 (3) 'Unix'
│ │ │ │ +C302D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C302E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C302F General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3031 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3033 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3037 CRC                   478B6B96 (1200319382)
│ │ │ │ +C303B Compressed Size       000003DF (991)
│ │ │ │ +C303F Uncompressed Size     00000935 (2357)
│ │ │ │ +C3043 Filename Length       0012 (18)
│ │ │ │ +C3045 Extra Length          0018 (24)
│ │ │ │ +C3047 Comment Length        0000 (0)
│ │ │ │ +C3049 Disk Start            0000 (0)
│ │ │ │ +C304B Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C304D Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3051 Local Header Offset   0003EFA1 (257953)
│ │ │ │ +C3055 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3055: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3067 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3069   Length              0005 (5)
│ │ │ │ +C306B   Flags               01 (1) 'Modification'
│ │ │ │ +C306C   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3070 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3072   Length              000B (11)
│ │ │ │ +C3074   Version             01 (1)
│ │ │ │ +C3075   UID Size            04 (4)
│ │ │ │ +C3076   UID                 00000000 (0)
│ │ │ │ +C307A   GID Size            04 (4)
│ │ │ │ +C307B   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C307F CENTRAL HEADER #26    02014B50 (33639248)
│ │ │ │ +C3083 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3084 Created OS            03 (3) 'Unix'
│ │ │ │ +C3085 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3086 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3087 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3089 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C308B Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C308F CRC                   E79489F0 (3885271536)
│ │ │ │ +C3093 Compressed Size       000001D3 (467)
│ │ │ │ +C3097 Uncompressed Size     00000311 (785)
│ │ │ │ +C309B Filename Length       0020 (32)
│ │ │ │ +C309D Extra Length          0018 (24)
│ │ │ │ +C309F Comment Length        0000 (0)
│ │ │ │ +C30A1 Disk Start            0000 (0)
│ │ │ │ +C30A3 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C30A5 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C30A9 Local Header Offset   0003F3CC (259020)
│ │ │ │ +C30AD Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC30AD: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C30CD Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C30CF   Length              0005 (5)
│ │ │ │ +C30D1   Flags               01 (1) 'Modification'
│ │ │ │ +C30D2   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C30D6 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C30D8   Length              000B (11)
│ │ │ │ +C30DA   Version             01 (1)
│ │ │ │ +C30DB   UID Size            04 (4)
│ │ │ │ +C30DC   UID                 00000000 (0)
│ │ │ │ +C30E0   GID Size            04 (4)
│ │ │ │ +C30E1   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C30E5 CENTRAL HEADER #27    02014B50 (33639248)
│ │ │ │ +C30E9 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C30EA Created OS            03 (3) 'Unix'
│ │ │ │ +C30EB Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C30EC Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C30ED General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C30EF Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C30F1 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C30F5 CRC                   73552FFE (1934962686)
│ │ │ │ +C30F9 Compressed Size       000017AB (6059)
│ │ │ │ +C30FD Uncompressed Size     00009D1B (40219)
│ │ │ │ +C3101 Filename Length       001B (27)
│ │ │ │ +C3103 Extra Length          0018 (24)
│ │ │ │ +C3105 Comment Length        0000 (0)
│ │ │ │ +C3107 Disk Start            0000 (0)
│ │ │ │ +C3109 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C310B Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C310F Local Header Offset   0003F5F9 (259577)
│ │ │ │ +C3113 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3113: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C312E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3130   Length              0005 (5)
│ │ │ │ +C3132   Flags               01 (1) 'Modification'
│ │ │ │ +C3133   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3137 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3139   Length              000B (11)
│ │ │ │ +C313B   Version             01 (1)
│ │ │ │ +C313C   UID Size            04 (4)
│ │ │ │ +C313D   UID                 00000000 (0)
│ │ │ │ +C3141   GID Size            04 (4)
│ │ │ │ +C3142   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3146 CENTRAL HEADER #28    02014B50 (33639248)
│ │ │ │ +C314A Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C314B Created OS            03 (3) 'Unix'
│ │ │ │ +C314C Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C314D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C314E General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3150 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3152 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3156 CRC                   09EB9A96 (166435478)
│ │ │ │ +C315A Compressed Size       0000136D (4973)
│ │ │ │ +C315E Uncompressed Size     00003B58 (15192)
│ │ │ │ +C3162 Filename Length       0015 (21)
│ │ │ │ +C3164 Extra Length          0018 (24)
│ │ │ │ +C3166 Comment Length        0000 (0)
│ │ │ │ +C3168 Disk Start            0000 (0)
│ │ │ │ +C316A Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C316C Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3170 Local Header Offset   00040DF9 (265721)
│ │ │ │ +C3174 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3174: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3189 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C318B   Length              0005 (5)
│ │ │ │ +C318D   Flags               01 (1) 'Modification'
│ │ │ │ +C318E   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3192 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3194   Length              000B (11)
│ │ │ │ +C3196   Version             01 (1)
│ │ │ │ +C3197   UID Size            04 (4)
│ │ │ │ +C3198   UID                 00000000 (0)
│ │ │ │ +C319C   GID Size            04 (4)
│ │ │ │ +C319D   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C31A1 CENTRAL HEADER #29    02014B50 (33639248)
│ │ │ │ +C31A5 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C31A6 Created OS            03 (3) 'Unix'
│ │ │ │ +C31A7 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C31A8 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C31A9 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C31AB Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C31AD Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C31B1 CRC                   F9EDEEDB (4193119963)
│ │ │ │ +C31B5 Compressed Size       00000AC9 (2761)
│ │ │ │ +C31B9 Uncompressed Size     00002133 (8499)
│ │ │ │ +C31BD Filename Length       0011 (17)
│ │ │ │ +C31BF Extra Length          0018 (24)
│ │ │ │ +C31C1 Comment Length        0000 (0)
│ │ │ │ +C31C3 Disk Start            0000 (0)
│ │ │ │ +C31C5 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C31C7 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C31CB Local Header Offset   000421B5 (270773)
│ │ │ │ +C31CF Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC31CF: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C31E0 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C31E2   Length              0005 (5)
│ │ │ │ +C31E4   Flags               01 (1) 'Modification'
│ │ │ │ +C31E5   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C31E9 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C31EB   Length              000B (11)
│ │ │ │ +C31ED   Version             01 (1)
│ │ │ │ +C31EE   UID Size            04 (4)
│ │ │ │ +C31EF   UID                 00000000 (0)
│ │ │ │ +C31F3   GID Size            04 (4)
│ │ │ │ +C31F4   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C31F8 CENTRAL HEADER #30    02014B50 (33639248)
│ │ │ │ +C31FC Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C31FD Created OS            03 (3) 'Unix'
│ │ │ │ +C31FE Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C31FF Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3200 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3202 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3204 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3208 CRC                   78F661F4 (2029412852)
│ │ │ │ +C320C Compressed Size       000003FE (1022)
│ │ │ │ +C3210 Uncompressed Size     00000F0C (3852)
│ │ │ │ +C3214 Filename Length       0014 (20)
│ │ │ │ +C3216 Extra Length          0018 (24)
│ │ │ │ +C3218 Comment Length        0000 (0)
│ │ │ │ +C321A Disk Start            0000 (0)
│ │ │ │ +C321C Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C321E Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3222 Local Header Offset   00042CC9 (273609)
│ │ │ │ +C3226 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3226: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C323A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C323C   Length              0005 (5)
│ │ │ │ +C323E   Flags               01 (1) 'Modification'
│ │ │ │ +C323F   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3243 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3245   Length              000B (11)
│ │ │ │ +C3247   Version             01 (1)
│ │ │ │ +C3248   UID Size            04 (4)
│ │ │ │ +C3249   UID                 00000000 (0)
│ │ │ │ +C324D   GID Size            04 (4)
│ │ │ │ +C324E   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3252 CENTRAL HEADER #31    02014B50 (33639248)
│ │ │ │ +C3256 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3257 Created OS            03 (3) 'Unix'
│ │ │ │ +C3258 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3259 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C325A General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C325C Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C325E Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3262 CRC                   3F5B0F93 (1062932371)
│ │ │ │ +C3266 Compressed Size       00001260 (4704)
│ │ │ │ +C326A Uncompressed Size     0000346B (13419)
│ │ │ │ +C326E Filename Length       0014 (20)
│ │ │ │ +C3270 Extra Length          0018 (24)
│ │ │ │ +C3272 Comment Length        0000 (0)
│ │ │ │ +C3274 Disk Start            0000 (0)
│ │ │ │ +C3276 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3278 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C327C Local Header Offset   00043115 (274709)
│ │ │ │ +C3280 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3280: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3294 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3296   Length              0005 (5)
│ │ │ │ +C3298   Flags               01 (1) 'Modification'
│ │ │ │ +C3299   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C329D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C329F   Length              000B (11)
│ │ │ │ +C32A1   Version             01 (1)
│ │ │ │ +C32A2   UID Size            04 (4)
│ │ │ │ +C32A3   UID                 00000000 (0)
│ │ │ │ +C32A7   GID Size            04 (4)
│ │ │ │ +C32A8   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C32AC CENTRAL HEADER #32    02014B50 (33639248)
│ │ │ │ +C32B0 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C32B1 Created OS            03 (3) 'Unix'
│ │ │ │ +C32B2 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C32B3 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C32B4 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C32B6 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C32B8 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C32BC CRC                   06606451 (106980433)
│ │ │ │ +C32C0 Compressed Size       00000ACF (2767)
│ │ │ │ +C32C4 Uncompressed Size     000022FF (8959)
│ │ │ │ +C32C8 Filename Length       001B (27)
│ │ │ │ +C32CA Extra Length          0018 (24)
│ │ │ │ +C32CC Comment Length        0000 (0)
│ │ │ │ +C32CE Disk Start            0000 (0)
│ │ │ │ +C32D0 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C32D2 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C32D6 Local Header Offset   000443C3 (279491)
│ │ │ │ +C32DA Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC32DA: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C32F5 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C32F7   Length              0005 (5)
│ │ │ │ +C32F9   Flags               01 (1) 'Modification'
│ │ │ │ +C32FA   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C32FE Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3300   Length              000B (11)
│ │ │ │ +C3302   Version             01 (1)
│ │ │ │ +C3303   UID Size            04 (4)
│ │ │ │ +C3304   UID                 00000000 (0)
│ │ │ │ +C3308   GID Size            04 (4)
│ │ │ │ +C3309   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C330D CENTRAL HEADER #33    02014B50 (33639248)
│ │ │ │ +C3311 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3312 Created OS            03 (3) 'Unix'
│ │ │ │ +C3313 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3314 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3315 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3317 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3319 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C331D CRC                   8B6CCC23 (2339163171)
│ │ │ │ +C3321 Compressed Size       00000C53 (3155)
│ │ │ │ +C3325 Uncompressed Size     00002742 (10050)
│ │ │ │ +C3329 Filename Length       0013 (19)
│ │ │ │ +C332B Extra Length          0018 (24)
│ │ │ │ +C332D Comment Length        0000 (0)
│ │ │ │ +C332F Disk Start            0000 (0)
│ │ │ │ +C3331 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3333 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3337 Local Header Offset   00044EE7 (282343)
│ │ │ │ +C333B Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC333B: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C334E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3350   Length              0005 (5)
│ │ │ │ +C3352   Flags               01 (1) 'Modification'
│ │ │ │ +C3353   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3357 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3359   Length              000B (11)
│ │ │ │ +C335B   Version             01 (1)
│ │ │ │ +C335C   UID Size            04 (4)
│ │ │ │ +C335D   UID                 00000000 (0)
│ │ │ │ +C3361   GID Size            04 (4)
│ │ │ │ +C3362   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3366 CENTRAL HEADER #34    02014B50 (33639248)
│ │ │ │ +C336A Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C336B Created OS            03 (3) 'Unix'
│ │ │ │ +C336C Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C336D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C336E General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3370 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3372 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3376 CRC                   75D0E296 (1976623766)
│ │ │ │ +C337A Compressed Size       00000C92 (3218)
│ │ │ │ +C337E Uncompressed Size     00003D11 (15633)
│ │ │ │ +C3382 Filename Length       0014 (20)
│ │ │ │ +C3384 Extra Length          0018 (24)
│ │ │ │ +C3386 Comment Length        0000 (0)
│ │ │ │ +C3388 Disk Start            0000 (0)
│ │ │ │ +C338A Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C338C Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3390 Local Header Offset   00045B87 (285575)
│ │ │ │ +C3394 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3394: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C33A8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C33AA   Length              0005 (5)
│ │ │ │ +C33AC   Flags               01 (1) 'Modification'
│ │ │ │ +C33AD   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C33B1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C33B3   Length              000B (11)
│ │ │ │ +C33B5   Version             01 (1)
│ │ │ │ +C33B6   UID Size            04 (4)
│ │ │ │ +C33B7   UID                 00000000 (0)
│ │ │ │ +C33BB   GID Size            04 (4)
│ │ │ │ +C33BC   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C33C0 CENTRAL HEADER #35    02014B50 (33639248)
│ │ │ │ +C33C4 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C33C5 Created OS            03 (3) 'Unix'
│ │ │ │ +C33C6 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C33C7 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C33C8 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C33CA Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C33CC Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C33D0 CRC                   C3A581AC (3282403756)
│ │ │ │ +C33D4 Compressed Size       00000F45 (3909)
│ │ │ │ +C33D8 Uncompressed Size     00003744 (14148)
│ │ │ │ +C33DC Filename Length       000F (15)
│ │ │ │ +C33DE Extra Length          0018 (24)
│ │ │ │ +C33E0 Comment Length        0000 (0)
│ │ │ │ +C33E2 Disk Start            0000 (0)
│ │ │ │ +C33E4 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C33E6 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C33EA Local Header Offset   00046867 (288871)
│ │ │ │ +C33EE Filename              'XXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC33EE: Filename 'XXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C33FD Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C33FF   Length              0005 (5)
│ │ │ │ +C3401   Flags               01 (1) 'Modification'
│ │ │ │ +C3402   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3406 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3408   Length              000B (11)
│ │ │ │ +C340A   Version             01 (1)
│ │ │ │ +C340B   UID Size            04 (4)
│ │ │ │ +C340C   UID                 00000000 (0)
│ │ │ │ +C3410   GID Size            04 (4)
│ │ │ │ +C3411   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3415 CENTRAL HEADER #36    02014B50 (33639248)
│ │ │ │ +C3419 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C341A Created OS            03 (3) 'Unix'
│ │ │ │ +C341B Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C341C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C341D General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C341F Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3421 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3425 CRC                   AD08D6E7 (2903037671)
│ │ │ │ +C3429 Compressed Size       000006CE (1742)
│ │ │ │ +C342D Uncompressed Size     00001AC4 (6852)
│ │ │ │ +C3431 Filename Length       000F (15)
│ │ │ │ +C3433 Extra Length          0018 (24)
│ │ │ │ +C3435 Comment Length        0000 (0)
│ │ │ │ +C3437 Disk Start            0000 (0)
│ │ │ │ +C3439 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C343B Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C343F Local Header Offset   000477F5 (292853)
│ │ │ │ +C3443 Filename              'XXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3443: Filename 'XXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3452 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3454   Length              0005 (5)
│ │ │ │ +C3456   Flags               01 (1) 'Modification'
│ │ │ │ +C3457   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C345B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C345D   Length              000B (11)
│ │ │ │ +C345F   Version             01 (1)
│ │ │ │ +C3460   UID Size            04 (4)
│ │ │ │ +C3461   UID                 00000000 (0)
│ │ │ │ +C3465   GID Size            04 (4)
│ │ │ │ +C3466   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C346A CENTRAL HEADER #37    02014B50 (33639248)
│ │ │ │ +C346E Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C346F Created OS            03 (3) 'Unix'
│ │ │ │ +C3470 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3471 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3472 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3474 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3476 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C347A CRC                   5583AB14 (1434692372)
│ │ │ │ +C347E Compressed Size       00001A52 (6738)
│ │ │ │ +C3482 Uncompressed Size     0000650E (25870)
│ │ │ │ +C3486 Filename Length       0013 (19)
│ │ │ │ +C3488 Extra Length          0018 (24)
│ │ │ │ +C348A Comment Length        0000 (0)
│ │ │ │ +C348C Disk Start            0000 (0)
│ │ │ │ +C348E Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3490 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3494 Local Header Offset   00047F0C (294668)
│ │ │ │ +C3498 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3498: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C34AB Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C34AD   Length              0005 (5)
│ │ │ │ +C34AF   Flags               01 (1) 'Modification'
│ │ │ │ +C34B0   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C34B4 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C34B6   Length              000B (11)
│ │ │ │ +C34B8   Version             01 (1)
│ │ │ │ +C34B9   UID Size            04 (4)
│ │ │ │ +C34BA   UID                 00000000 (0)
│ │ │ │ +C34BE   GID Size            04 (4)
│ │ │ │ +C34BF   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C34C3 CENTRAL HEADER #38    02014B50 (33639248)
│ │ │ │ +C34C7 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C34C8 Created OS            03 (3) 'Unix'
│ │ │ │ +C34C9 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C34CA Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C34CB General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C34CD Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C34CF Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C34D3 CRC                   90967BFA (2425781242)
│ │ │ │ +C34D7 Compressed Size       000009A6 (2470)
│ │ │ │ +C34DB Uncompressed Size     00001B6A (7018)
│ │ │ │ +C34DF Filename Length       0010 (16)
│ │ │ │ +C34E1 Extra Length          0018 (24)
│ │ │ │ +C34E3 Comment Length        0000 (0)
│ │ │ │ +C34E5 Disk Start            0000 (0)
│ │ │ │ +C34E7 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C34E9 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C34ED Local Header Offset   000499AB (301483)
│ │ │ │ +C34F1 Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC34F1: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3501 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3503   Length              0005 (5)
│ │ │ │ +C3505   Flags               01 (1) 'Modification'
│ │ │ │ +C3506   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C350A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C350C   Length              000B (11)
│ │ │ │ +C350E   Version             01 (1)
│ │ │ │ +C350F   UID Size            04 (4)
│ │ │ │ +C3510   UID                 00000000 (0)
│ │ │ │ +C3514   GID Size            04 (4)
│ │ │ │ +C3515   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3519 CENTRAL HEADER #39    02014B50 (33639248)
│ │ │ │ +C351D Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C351E Created OS            03 (3) 'Unix'
│ │ │ │ +C351F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3520 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3521 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3523 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3525 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3529 CRC                   D37ED789 (3548305289)
│ │ │ │ +C352D Compressed Size       000006B6 (1718)
│ │ │ │ +C3531 Uncompressed Size     00001565 (5477)
│ │ │ │ +C3535 Filename Length       0012 (18)
│ │ │ │ +C3537 Extra Length          0018 (24)
│ │ │ │ +C3539 Comment Length        0000 (0)
│ │ │ │ +C353B Disk Start            0000 (0)
│ │ │ │ +C353D Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C353F Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3543 Local Header Offset   0004A39B (304027)
│ │ │ │ +C3547 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3547: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3559 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C355B   Length              0005 (5)
│ │ │ │ +C355D   Flags               01 (1) 'Modification'
│ │ │ │ +C355E   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3562 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3564   Length              000B (11)
│ │ │ │ +C3566   Version             01 (1)
│ │ │ │ +C3567   UID Size            04 (4)
│ │ │ │ +C3568   UID                 00000000 (0)
│ │ │ │ +C356C   GID Size            04 (4)
│ │ │ │ +C356D   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3571 CENTRAL HEADER #40    02014B50 (33639248)
│ │ │ │ +C3575 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3576 Created OS            03 (3) 'Unix'
│ │ │ │ +C3577 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3578 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3579 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C357B Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C357D Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3581 CRC                   F24D9270 (4065170032)
│ │ │ │ +C3585 Compressed Size       00002D56 (11606)
│ │ │ │ +C3589 Uncompressed Size     0000D083 (53379)
│ │ │ │ +C358D Filename Length       0010 (16)
│ │ │ │ +C358F Extra Length          0018 (24)
│ │ │ │ +C3591 Comment Length        0000 (0)
│ │ │ │ +C3593 Disk Start            0000 (0)
│ │ │ │ +C3595 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3597 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C359B Local Header Offset   0004AA9D (305821)
│ │ │ │ +C359F Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC359F: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C35AF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C35B1   Length              0005 (5)
│ │ │ │ +C35B3   Flags               01 (1) 'Modification'
│ │ │ │ +C35B4   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C35B8 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C35BA   Length              000B (11)
│ │ │ │ +C35BC   Version             01 (1)
│ │ │ │ +C35BD   UID Size            04 (4)
│ │ │ │ +C35BE   UID                 00000000 (0)
│ │ │ │ +C35C2   GID Size            04 (4)
│ │ │ │ +C35C3   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C35C7 CENTRAL HEADER #41    02014B50 (33639248)
│ │ │ │ +C35CB Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C35CC Created OS            03 (3) 'Unix'
│ │ │ │ +C35CD Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C35CE Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C35CF General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C35D1 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C35D3 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C35D7 CRC                   6DD28D49 (1842515273)
│ │ │ │ +C35DB Compressed Size       00001E7F (7807)
│ │ │ │ +C35DF Uncompressed Size     00009AAA (39594)
│ │ │ │ +C35E3 Filename Length       0012 (18)
│ │ │ │ +C35E5 Extra Length          0018 (24)
│ │ │ │ +C35E7 Comment Length        0000 (0)
│ │ │ │ +C35E9 Disk Start            0000 (0)
│ │ │ │ +C35EB Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C35ED Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C35F1 Local Header Offset   0004D83D (317501)
│ │ │ │ +C35F5 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC35F5: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3607 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3609   Length              0005 (5)
│ │ │ │ +C360B   Flags               01 (1) 'Modification'
│ │ │ │ +C360C   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3610 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3612   Length              000B (11)
│ │ │ │ +C3614   Version             01 (1)
│ │ │ │ +C3615   UID Size            04 (4)
│ │ │ │ +C3616   UID                 00000000 (0)
│ │ │ │ +C361A   GID Size            04 (4)
│ │ │ │ +C361B   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C361F CENTRAL HEADER #42    02014B50 (33639248)
│ │ │ │ +C3623 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3624 Created OS            03 (3) 'Unix'
│ │ │ │ +C3625 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3626 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3627 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3629 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C362B Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C362F CRC                   68D3A344 (1758700356)
│ │ │ │ +C3633 Compressed Size       00001478 (5240)
│ │ │ │ +C3637 Uncompressed Size     00007AD0 (31440)
│ │ │ │ +C363B Filename Length       0018 (24)
│ │ │ │ +C363D Extra Length          0018 (24)
│ │ │ │ +C363F Comment Length        0000 (0)
│ │ │ │ +C3641 Disk Start            0000 (0)
│ │ │ │ +C3643 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3645 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3649 Local Header Offset   0004F708 (325384)
│ │ │ │ +C364D Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC364D: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3665 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3667   Length              0005 (5)
│ │ │ │ +C3669   Flags               01 (1) 'Modification'
│ │ │ │ +C366A   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C366E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3670   Length              000B (11)
│ │ │ │ +C3672   Version             01 (1)
│ │ │ │ +C3673   UID Size            04 (4)
│ │ │ │ +C3674   UID                 00000000 (0)
│ │ │ │ +C3678   GID Size            04 (4)
│ │ │ │ +C3679   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C367D CENTRAL HEADER #43    02014B50 (33639248)
│ │ │ │ +C3681 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3682 Created OS            03 (3) 'Unix'
│ │ │ │ +C3683 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3684 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3685 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3687 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3689 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C368D CRC                   BE84805E (3196354654)
│ │ │ │ +C3691 Compressed Size       000021E3 (8675)
│ │ │ │ +C3695 Uncompressed Size     0000D21D (53789)
│ │ │ │ +C3699 Filename Length       001F (31)
│ │ │ │ +C369B Extra Length          0018 (24)
│ │ │ │ +C369D Comment Length        0000 (0)
│ │ │ │ +C369F Disk Start            0000 (0)
│ │ │ │ +C36A1 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C36A3 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C36A7 Local Header Offset   00050BD2 (330706)
│ │ │ │ +C36AB Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC36AB: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C36CA Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C36CC   Length              0005 (5)
│ │ │ │ +C36CE   Flags               01 (1) 'Modification'
│ │ │ │ +C36CF   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C36D3 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C36D5   Length              000B (11)
│ │ │ │ +C36D7   Version             01 (1)
│ │ │ │ +C36D8   UID Size            04 (4)
│ │ │ │ +C36D9   UID                 00000000 (0)
│ │ │ │ +C36DD   GID Size            04 (4)
│ │ │ │ +C36DE   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C36E2 CENTRAL HEADER #44    02014B50 (33639248)
│ │ │ │ +C36E6 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C36E7 Created OS            03 (3) 'Unix'
│ │ │ │ +C36E8 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C36E9 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C36EA General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C36EC Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C36EE Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C36F2 CRC                   585AC976 (1482344822)
│ │ │ │ +C36F6 Compressed Size       000003F7 (1015)
│ │ │ │ +C36FA Uncompressed Size     000008A3 (2211)
│ │ │ │ +C36FE Filename Length       001E (30)
│ │ │ │ +C3700 Extra Length          0018 (24)
│ │ │ │ +C3702 Comment Length        0000 (0)
│ │ │ │ +C3704 Disk Start            0000 (0)
│ │ │ │ +C3706 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3708 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C370C Local Header Offset   00052E0E (339470)
│ │ │ │ +C3710 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3710: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C372E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3730   Length              0005 (5)
│ │ │ │ +C3732   Flags               01 (1) 'Modification'
│ │ │ │ +C3733   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3737 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3739   Length              000B (11)
│ │ │ │ +C373B   Version             01 (1)
│ │ │ │ +C373C   UID Size            04 (4)
│ │ │ │ +C373D   UID                 00000000 (0)
│ │ │ │ +C3741   GID Size            04 (4)
│ │ │ │ +C3742   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3746 CENTRAL HEADER #45    02014B50 (33639248)
│ │ │ │ +C374A Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C374B Created OS            03 (3) 'Unix'
│ │ │ │ +C374C Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C374D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C374E General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3750 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3752 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3756 CRC                   16308EDA (372281050)
│ │ │ │ +C375A Compressed Size       00004361 (17249)
│ │ │ │ +C375E Uncompressed Size     0000E06F (57455)
│ │ │ │ +C3762 Filename Length       0013 (19)
│ │ │ │ +C3764 Extra Length          0018 (24)
│ │ │ │ +C3766 Comment Length        0000 (0)
│ │ │ │ +C3768 Disk Start            0000 (0)
│ │ │ │ +C376A Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C376C Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3770 Local Header Offset   0005325D (340573)
│ │ │ │ +C3774 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3774: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3787 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3789   Length              0005 (5)
│ │ │ │ +C378B   Flags               01 (1) 'Modification'
│ │ │ │ +C378C   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3790 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3792   Length              000B (11)
│ │ │ │ +C3794   Version             01 (1)
│ │ │ │ +C3795   UID Size            04 (4)
│ │ │ │ +C3796   UID                 00000000 (0)
│ │ │ │ +C379A   GID Size            04 (4)
│ │ │ │ +C379B   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C379F CENTRAL HEADER #46    02014B50 (33639248)
│ │ │ │ +C37A3 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C37A4 Created OS            03 (3) 'Unix'
│ │ │ │ +C37A5 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C37A6 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C37A7 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C37A9 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C37AB Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C37AF CRC                   4B98C7C0 (1268303808)
│ │ │ │ +C37B3 Compressed Size       000026C3 (9923)
│ │ │ │ +C37B7 Uncompressed Size     00006E45 (28229)
│ │ │ │ +C37BB Filename Length       0019 (25)
│ │ │ │ +C37BD Extra Length          0018 (24)
│ │ │ │ +C37BF Comment Length        0000 (0)
│ │ │ │ +C37C1 Disk Start            0000 (0)
│ │ │ │ +C37C3 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C37C5 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C37C9 Local Header Offset   0005760B (357899)
│ │ │ │ +C37CD Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC37CD: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C37E6 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C37E8   Length              0005 (5)
│ │ │ │ +C37EA   Flags               01 (1) 'Modification'
│ │ │ │ +C37EB   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C37EF Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C37F1   Length              000B (11)
│ │ │ │ +C37F3   Version             01 (1)
│ │ │ │ +C37F4   UID Size            04 (4)
│ │ │ │ +C37F5   UID                 00000000 (0)
│ │ │ │ +C37F9   GID Size            04 (4)
│ │ │ │ +C37FA   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C37FE CENTRAL HEADER #47    02014B50 (33639248)
│ │ │ │ +C3802 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3803 Created OS            03 (3) 'Unix'
│ │ │ │ +C3804 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3805 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3806 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3808 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C380A Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C380E CRC                   F8618863 (4167141475)
│ │ │ │ +C3812 Compressed Size       00002738 (10040)
│ │ │ │ +C3816 Uncompressed Size     00008B83 (35715)
│ │ │ │ +C381A Filename Length       0019 (25)
│ │ │ │ +C381C Extra Length          0018 (24)
│ │ │ │ +C381E Comment Length        0000 (0)
│ │ │ │ +C3820 Disk Start            0000 (0)
│ │ │ │ +C3822 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3824 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3828 Local Header Offset   00059D21 (367905)
│ │ │ │ +C382C Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC382C: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3845 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3847   Length              0005 (5)
│ │ │ │ +C3849   Flags               01 (1) 'Modification'
│ │ │ │ +C384A   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C384E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3850   Length              000B (11)
│ │ │ │ +C3852   Version             01 (1)
│ │ │ │ +C3853   UID Size            04 (4)
│ │ │ │ +C3854   UID                 00000000 (0)
│ │ │ │ +C3858   GID Size            04 (4)
│ │ │ │ +C3859   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C385D CENTRAL HEADER #48    02014B50 (33639248)
│ │ │ │ +C3861 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3862 Created OS            03 (3) 'Unix'
│ │ │ │ +C3863 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3864 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3865 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3867 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3869 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C386D CRC                   19093DDC (420036060)
│ │ │ │ +C3871 Compressed Size       00000ECC (3788)
│ │ │ │ +C3875 Uncompressed Size     000053BF (21439)
│ │ │ │ +C3879 Filename Length       0021 (33)
│ │ │ │ +C387B Extra Length          0018 (24)
│ │ │ │ +C387D Comment Length        0000 (0)
│ │ │ │ +C387F Disk Start            0000 (0)
│ │ │ │ +C3881 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3883 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3887 Local Header Offset   0005C4AC (378028)
│ │ │ │ +C388B Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC388B: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C38AC Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C38AE   Length              0005 (5)
│ │ │ │ +C38B0   Flags               01 (1) 'Modification'
│ │ │ │ +C38B1   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C38B5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C38B7   Length              000B (11)
│ │ │ │ +C38B9   Version             01 (1)
│ │ │ │ +C38BA   UID Size            04 (4)
│ │ │ │ +C38BB   UID                 00000000 (0)
│ │ │ │ +C38BF   GID Size            04 (4)
│ │ │ │ +C38C0   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C38C4 CENTRAL HEADER #49    02014B50 (33639248)
│ │ │ │ +C38C8 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C38C9 Created OS            03 (3) 'Unix'
│ │ │ │ +C38CA Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C38CB Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C38CC General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C38CE Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C38D0 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C38D4 CRC                   D1EC3113 (3521917203)
│ │ │ │ +C38D8 Compressed Size       00000535 (1333)
│ │ │ │ +C38DC Uncompressed Size     00000C96 (3222)
│ │ │ │ +C38E0 Filename Length       0017 (23)
│ │ │ │ +C38E2 Extra Length          0018 (24)
│ │ │ │ +C38E4 Comment Length        0000 (0)
│ │ │ │ +C38E6 Disk Start            0000 (0)
│ │ │ │ +C38E8 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C38EA Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C38EE Local Header Offset   0005D3D3 (381907)
│ │ │ │ +C38F2 Filename              'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC38F2: Filename 'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3909 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C390B   Length              0005 (5)
│ │ │ │ +C390D   Flags               01 (1) 'Modification'
│ │ │ │ +C390E   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3912 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3914   Length              000B (11)
│ │ │ │ +C3916   Version             01 (1)
│ │ │ │ +C3917   UID Size            04 (4)
│ │ │ │ +C3918   UID                 00000000 (0)
│ │ │ │ +C391C   GID Size            04 (4)
│ │ │ │ +C391D   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3921 CENTRAL HEADER #50    02014B50 (33639248)
│ │ │ │ +C3925 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3926 Created OS            03 (3) 'Unix'
│ │ │ │ +C3927 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3928 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3929 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C392B Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C392D Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3931 CRC                   9ED6F2D9 (2664887001)
│ │ │ │ +C3935 Compressed Size       00000467 (1127)
│ │ │ │ +C3939 Uncompressed Size     00000931 (2353)
│ │ │ │ +C393D Filename Length       001B (27)
│ │ │ │ +C393F Extra Length          0018 (24)
│ │ │ │ +C3941 Comment Length        0000 (0)
│ │ │ │ +C3943 Disk Start            0000 (0)
│ │ │ │ +C3945 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3947 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C394B Local Header Offset   0005D959 (383321)
│ │ │ │ +C394F Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC394F: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C396A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C396C   Length              0005 (5)
│ │ │ │ +C396E   Flags               01 (1) 'Modification'
│ │ │ │ +C396F   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3973 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3975   Length              000B (11)
│ │ │ │ +C3977   Version             01 (1)
│ │ │ │ +C3978   UID Size            04 (4)
│ │ │ │ +C3979   UID                 00000000 (0)
│ │ │ │ +C397D   GID Size            04 (4)
│ │ │ │ +C397E   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3982 CENTRAL HEADER #51    02014B50 (33639248)
│ │ │ │ +C3986 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3987 Created OS            03 (3) 'Unix'
│ │ │ │ +C3988 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3989 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C398A General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C398C Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C398E Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3992 CRC                   2606F569 (637990249)
│ │ │ │ +C3996 Compressed Size       000016F6 (5878)
│ │ │ │ +C399A Uncompressed Size     00007A86 (31366)
│ │ │ │ +C399E Filename Length       001F (31)
│ │ │ │ +C39A0 Extra Length          0018 (24)
│ │ │ │ +C39A2 Comment Length        0000 (0)
│ │ │ │ +C39A4 Disk Start            0000 (0)
│ │ │ │ +C39A6 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C39A8 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C39AC Local Header Offset   0005DE15 (384533)
│ │ │ │ +C39B0 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC39B0: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C39CF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C39D1   Length              0005 (5)
│ │ │ │ +C39D3   Flags               01 (1) 'Modification'
│ │ │ │ +C39D4   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C39D8 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C39DA   Length              000B (11)
│ │ │ │ +C39DC   Version             01 (1)
│ │ │ │ +C39DD   UID Size            04 (4)
│ │ │ │ +C39DE   UID                 00000000 (0)
│ │ │ │ +C39E2   GID Size            04 (4)
│ │ │ │ +C39E3   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C39E7 CENTRAL HEADER #52    02014B50 (33639248)
│ │ │ │ +C39EB Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C39EC Created OS            03 (3) 'Unix'
│ │ │ │ +C39ED Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C39EE Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C39EF General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C39F1 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C39F3 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C39F7 CRC                   758BB33D (1972089661)
│ │ │ │ +C39FB Compressed Size       00004168 (16744)
│ │ │ │ +C39FF Uncompressed Size     0001D163 (119139)
│ │ │ │ +C3A03 Filename Length       0010 (16)
│ │ │ │ +C3A05 Extra Length          0018 (24)
│ │ │ │ +C3A07 Comment Length        0000 (0)
│ │ │ │ +C3A09 Disk Start            0000 (0)
│ │ │ │ +C3A0B Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3A0D Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3A11 Local Header Offset   0005F564 (390500)
│ │ │ │ +C3A15 Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3A15: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3A25 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3A27   Length              0005 (5)
│ │ │ │ +C3A29   Flags               01 (1) 'Modification'
│ │ │ │ +C3A2A   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3A2E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3A30   Length              000B (11)
│ │ │ │ +C3A32   Version             01 (1)
│ │ │ │ +C3A33   UID Size            04 (4)
│ │ │ │ +C3A34   UID                 00000000 (0)
│ │ │ │ +C3A38   GID Size            04 (4)
│ │ │ │ +C3A39   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3A3D CENTRAL HEADER #53    02014B50 (33639248)
│ │ │ │ +C3A41 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3A42 Created OS            03 (3) 'Unix'
│ │ │ │ +C3A43 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3A44 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3A45 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3A47 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3A49 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3A4D CRC                   C55EF92D (3311335725)
│ │ │ │ +C3A51 Compressed Size       00000AE8 (2792)
│ │ │ │ +C3A55 Uncompressed Size     000021E8 (8680)
│ │ │ │ +C3A59 Filename Length       0014 (20)
│ │ │ │ +C3A5B Extra Length          0018 (24)
│ │ │ │ +C3A5D Comment Length        0000 (0)
│ │ │ │ +C3A5F Disk Start            0000 (0)
│ │ │ │ +C3A61 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3A63 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3A67 Local Header Offset   00063716 (407318)
│ │ │ │ +C3A6B Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3A6B: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3A7F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3A81   Length              0005 (5)
│ │ │ │ +C3A83   Flags               01 (1) 'Modification'
│ │ │ │ +C3A84   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3A88 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3A8A   Length              000B (11)
│ │ │ │ +C3A8C   Version             01 (1)
│ │ │ │ +C3A8D   UID Size            04 (4)
│ │ │ │ +C3A8E   UID                 00000000 (0)
│ │ │ │ +C3A92   GID Size            04 (4)
│ │ │ │ +C3A93   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3A97 CENTRAL HEADER #54    02014B50 (33639248)
│ │ │ │ +C3A9B Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3A9C Created OS            03 (3) 'Unix'
│ │ │ │ +C3A9D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3A9E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3A9F General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3AA1 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3AA3 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3AA7 CRC                   32543857 (844380247)
│ │ │ │ +C3AAB Compressed Size       0000B523 (46371)
│ │ │ │ +C3AAF Uncompressed Size     00041755 (268117)
│ │ │ │ +C3AB3 Filename Length       0017 (23)
│ │ │ │ +C3AB5 Extra Length          0018 (24)
│ │ │ │ +C3AB7 Comment Length        0000 (0)
│ │ │ │ +C3AB9 Disk Start            0000 (0)
│ │ │ │ +C3ABB Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3ABD Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3AC1 Local Header Offset   0006424C (410188)
│ │ │ │ +C3AC5 Filename              'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3AC5: Filename 'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3ADC Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3ADE   Length              0005 (5)
│ │ │ │ +C3AE0   Flags               01 (1) 'Modification'
│ │ │ │ +C3AE1   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3AE5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3AE7   Length              000B (11)
│ │ │ │ +C3AE9   Version             01 (1)
│ │ │ │ +C3AEA   UID Size            04 (4)
│ │ │ │ +C3AEB   UID                 00000000 (0)
│ │ │ │ +C3AEF   GID Size            04 (4)
│ │ │ │ +C3AF0   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3AF4 CENTRAL HEADER #55    02014B50 (33639248)
│ │ │ │ +C3AF8 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3AF9 Created OS            03 (3) 'Unix'
│ │ │ │ +C3AFA Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3AFB Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3AFC General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3AFE Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3B00 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3B04 CRC                   564036C9 (1447048905)
│ │ │ │ +C3B08 Compressed Size       00000400 (1024)
│ │ │ │ +C3B0C Uncompressed Size     0000093D (2365)
│ │ │ │ +C3B10 Filename Length       0013 (19)
│ │ │ │ +C3B12 Extra Length          0018 (24)
│ │ │ │ +C3B14 Comment Length        0000 (0)
│ │ │ │ +C3B16 Disk Start            0000 (0)
│ │ │ │ +C3B18 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3B1A Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3B1E Local Header Offset   0006F7C0 (456640)
│ │ │ │ +C3B22 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3B22: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3B35 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3B37   Length              0005 (5)
│ │ │ │ +C3B39   Flags               01 (1) 'Modification'
│ │ │ │ +C3B3A   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3B3E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3B40   Length              000B (11)
│ │ │ │ +C3B42   Version             01 (1)
│ │ │ │ +C3B43   UID Size            04 (4)
│ │ │ │ +C3B44   UID                 00000000 (0)
│ │ │ │ +C3B48   GID Size            04 (4)
│ │ │ │ +C3B49   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3B4D CENTRAL HEADER #56    02014B50 (33639248)
│ │ │ │ +C3B51 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3B52 Created OS            03 (3) 'Unix'
│ │ │ │ +C3B53 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3B54 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3B55 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3B57 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3B59 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3B5D CRC                   4AD4846E (1255441518)
│ │ │ │ +C3B61 Compressed Size       000014D9 (5337)
│ │ │ │ +C3B65 Uncompressed Size     00006892 (26770)
│ │ │ │ +C3B69 Filename Length       0012 (18)
│ │ │ │ +C3B6B Extra Length          0018 (24)
│ │ │ │ +C3B6D Comment Length        0000 (0)
│ │ │ │ +C3B6F Disk Start            0000 (0)
│ │ │ │ +C3B71 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3B73 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3B77 Local Header Offset   0006FC0D (457741)
│ │ │ │ +C3B7B Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3B7B: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3B8D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3B8F   Length              0005 (5)
│ │ │ │ +C3B91   Flags               01 (1) 'Modification'
│ │ │ │ +C3B92   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3B96 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3B98   Length              000B (11)
│ │ │ │ +C3B9A   Version             01 (1)
│ │ │ │ +C3B9B   UID Size            04 (4)
│ │ │ │ +C3B9C   UID                 00000000 (0)
│ │ │ │ +C3BA0   GID Size            04 (4)
│ │ │ │ +C3BA1   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3BA5 CENTRAL HEADER #57    02014B50 (33639248)
│ │ │ │ +C3BA9 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3BAA Created OS            03 (3) 'Unix'
│ │ │ │ +C3BAB Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3BAC Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3BAD General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3BAF Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3BB1 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3BB5 CRC                   AB6E6BBC (2876140476)
│ │ │ │ +C3BB9 Compressed Size       00001205 (4613)
│ │ │ │ +C3BBD Uncompressed Size     0000414F (16719)
│ │ │ │ +C3BC1 Filename Length       0012 (18)
│ │ │ │ +C3BC3 Extra Length          0018 (24)
│ │ │ │ +C3BC5 Comment Length        0000 (0)
│ │ │ │ +C3BC7 Disk Start            0000 (0)
│ │ │ │ +C3BC9 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3BCB Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3BCF Local Header Offset   00071132 (463154)
│ │ │ │ +C3BD3 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3BD3: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3BE5 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3BE7   Length              0005 (5)
│ │ │ │ +C3BE9   Flags               01 (1) 'Modification'
│ │ │ │ +C3BEA   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3BEE Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3BF0   Length              000B (11)
│ │ │ │ +C3BF2   Version             01 (1)
│ │ │ │ +C3BF3   UID Size            04 (4)
│ │ │ │ +C3BF4   UID                 00000000 (0)
│ │ │ │ +C3BF8   GID Size            04 (4)
│ │ │ │ +C3BF9   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3BFD CENTRAL HEADER #58    02014B50 (33639248)
│ │ │ │ +C3C01 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3C02 Created OS            03 (3) 'Unix'
│ │ │ │ +C3C03 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3C04 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3C05 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3C07 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3C09 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3C0D CRC                   5C8A4BDC (1552567260)
│ │ │ │ +C3C11 Compressed Size       00000704 (1796)
│ │ │ │ +C3C15 Uncompressed Size     000011A7 (4519)
│ │ │ │ +C3C19 Filename Length       0019 (25)
│ │ │ │ +C3C1B Extra Length          0018 (24)
│ │ │ │ +C3C1D Comment Length        0000 (0)
│ │ │ │ +C3C1F Disk Start            0000 (0)
│ │ │ │ +C3C21 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3C23 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3C27 Local Header Offset   00072383 (467843)
│ │ │ │ +C3C2B Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3C2B: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3C44 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3C46   Length              0005 (5)
│ │ │ │ +C3C48   Flags               01 (1) 'Modification'
│ │ │ │ +C3C49   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3C4D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3C4F   Length              000B (11)
│ │ │ │ +C3C51   Version             01 (1)
│ │ │ │ +C3C52   UID Size            04 (4)
│ │ │ │ +C3C53   UID                 00000000 (0)
│ │ │ │ +C3C57   GID Size            04 (4)
│ │ │ │ +C3C58   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3C5C CENTRAL HEADER #59    02014B50 (33639248)
│ │ │ │ +C3C60 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3C61 Created OS            03 (3) 'Unix'
│ │ │ │ +C3C62 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3C63 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3C64 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3C66 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3C68 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3C6C CRC                   3381C721 (864143137)
│ │ │ │ +C3C70 Compressed Size       000018B5 (6325)
│ │ │ │ +C3C74 Uncompressed Size     0000A678 (42616)
│ │ │ │ +C3C78 Filename Length       0019 (25)
│ │ │ │ +C3C7A Extra Length          0018 (24)
│ │ │ │ +C3C7C Comment Length        0000 (0)
│ │ │ │ +C3C7E Disk Start            0000 (0)
│ │ │ │ +C3C80 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3C82 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3C86 Local Header Offset   00072ADA (469722)
│ │ │ │ +C3C8A Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3C8A: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3CA3 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3CA5   Length              0005 (5)
│ │ │ │ +C3CA7   Flags               01 (1) 'Modification'
│ │ │ │ +C3CA8   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3CAC Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3CAE   Length              000B (11)
│ │ │ │ +C3CB0   Version             01 (1)
│ │ │ │ +C3CB1   UID Size            04 (4)
│ │ │ │ +C3CB2   UID                 00000000 (0)
│ │ │ │ +C3CB6   GID Size            04 (4)
│ │ │ │ +C3CB7   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3CBB CENTRAL HEADER #60    02014B50 (33639248)
│ │ │ │ +C3CBF Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3CC0 Created OS            03 (3) 'Unix'
│ │ │ │ +C3CC1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3CC2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3CC3 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3CC5 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3CC7 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3CCB CRC                   4D1409E6 (1293158886)
│ │ │ │ +C3CCF Compressed Size       0000177C (6012)
│ │ │ │ +C3CD3 Uncompressed Size     0000472C (18220)
│ │ │ │ +C3CD7 Filename Length       0014 (20)
│ │ │ │ +C3CD9 Extra Length          0018 (24)
│ │ │ │ +C3CDB Comment Length        0000 (0)
│ │ │ │ +C3CDD Disk Start            0000 (0)
│ │ │ │ +C3CDF Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3CE1 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3CE5 Local Header Offset   000743E2 (476130)
│ │ │ │ +C3CE9 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3CE9: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3CFD Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3CFF   Length              0005 (5)
│ │ │ │ +C3D01   Flags               01 (1) 'Modification'
│ │ │ │ +C3D02   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3D06 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3D08   Length              000B (11)
│ │ │ │ +C3D0A   Version             01 (1)
│ │ │ │ +C3D0B   UID Size            04 (4)
│ │ │ │ +C3D0C   UID                 00000000 (0)
│ │ │ │ +C3D10   GID Size            04 (4)
│ │ │ │ +C3D11   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3D15 CENTRAL HEADER #61    02014B50 (33639248)
│ │ │ │ +C3D19 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3D1A Created OS            03 (3) 'Unix'
│ │ │ │ +C3D1B Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3D1C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3D1D General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3D1F Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3D21 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3D25 CRC                   2F723DFF (796016127)
│ │ │ │ +C3D29 Compressed Size       00000409 (1033)
│ │ │ │ +C3D2D Uncompressed Size     00000825 (2085)
│ │ │ │ +C3D31 Filename Length       001C (28)
│ │ │ │ +C3D33 Extra Length          0018 (24)
│ │ │ │ +C3D35 Comment Length        0000 (0)
│ │ │ │ +C3D37 Disk Start            0000 (0)
│ │ │ │ +C3D39 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3D3B Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3D3F Local Header Offset   00075BAC (482220)
│ │ │ │ +C3D43 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3D43: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3D5F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3D61   Length              0005 (5)
│ │ │ │ +C3D63   Flags               01 (1) 'Modification'
│ │ │ │ +C3D64   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3D68 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3D6A   Length              000B (11)
│ │ │ │ +C3D6C   Version             01 (1)
│ │ │ │ +C3D6D   UID Size            04 (4)
│ │ │ │ +C3D6E   UID                 00000000 (0)
│ │ │ │ +C3D72   GID Size            04 (4)
│ │ │ │ +C3D73   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3D77 CENTRAL HEADER #62    02014B50 (33639248)
│ │ │ │ +C3D7B Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3D7C Created OS            03 (3) 'Unix'
│ │ │ │ +C3D7D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3D7E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3D7F General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3D81 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3D83 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3D87 CRC                   AF61C4DB (2942420187)
│ │ │ │ +C3D8B Compressed Size       000024C3 (9411)
│ │ │ │ +C3D8F Uncompressed Size     0000B65D (46685)
│ │ │ │ +C3D93 Filename Length       001F (31)
│ │ │ │ +C3D95 Extra Length          0018 (24)
│ │ │ │ +C3D97 Comment Length        0000 (0)
│ │ │ │ +C3D99 Disk Start            0000 (0)
│ │ │ │ +C3D9B Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3D9D Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3DA1 Local Header Offset   0007600B (483339)
│ │ │ │ +C3DA5 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3DA5: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3DC4 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3DC6   Length              0005 (5)
│ │ │ │ +C3DC8   Flags               01 (1) 'Modification'
│ │ │ │ +C3DC9   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3DCD Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3DCF   Length              000B (11)
│ │ │ │ +C3DD1   Version             01 (1)
│ │ │ │ +C3DD2   UID Size            04 (4)
│ │ │ │ +C3DD3   UID                 00000000 (0)
│ │ │ │ +C3DD7   GID Size            04 (4)
│ │ │ │ +C3DD8   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3DDC CENTRAL HEADER #63    02014B50 (33639248)
│ │ │ │ +C3DE0 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3DE1 Created OS            03 (3) 'Unix'
│ │ │ │ +C3DE2 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3DE3 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3DE4 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3DE6 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3DE8 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3DEC CRC                   BDFBBF8D (3187392397)
│ │ │ │ +C3DF0 Compressed Size       00000E7A (3706)
│ │ │ │ +C3DF4 Uncompressed Size     000052DA (21210)
│ │ │ │ +C3DF8 Filename Length       001F (31)
│ │ │ │ +C3DFA Extra Length          0018 (24)
│ │ │ │ +C3DFC Comment Length        0000 (0)
│ │ │ │ +C3DFE Disk Start            0000 (0)
│ │ │ │ +C3E00 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3E02 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3E06 Local Header Offset   00078527 (492839)
│ │ │ │ +C3E0A Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3E0A: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3E29 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3E2B   Length              0005 (5)
│ │ │ │ +C3E2D   Flags               01 (1) 'Modification'
│ │ │ │ +C3E2E   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3E32 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3E34   Length              000B (11)
│ │ │ │ +C3E36   Version             01 (1)
│ │ │ │ +C3E37   UID Size            04 (4)
│ │ │ │ +C3E38   UID                 00000000 (0)
│ │ │ │ +C3E3C   GID Size            04 (4)
│ │ │ │ +C3E3D   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3E41 CENTRAL HEADER #64    02014B50 (33639248)
│ │ │ │ +C3E45 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3E46 Created OS            03 (3) 'Unix'
│ │ │ │ +C3E47 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3E48 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3E49 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3E4B Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3E4D Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3E51 CRC                   720DE003 (1913511939)
│ │ │ │ +C3E55 Compressed Size       00000A45 (2629)
│ │ │ │ +C3E59 Uncompressed Size     0000247A (9338)
│ │ │ │ +C3E5D Filename Length       0013 (19)
│ │ │ │ +C3E5F Extra Length          0018 (24)
│ │ │ │ +C3E61 Comment Length        0000 (0)
│ │ │ │ +C3E63 Disk Start            0000 (0)
│ │ │ │ +C3E65 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3E67 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3E6B Local Header Offset   000793FA (496634)
│ │ │ │ +C3E6F Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3E6F: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3E82 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3E84   Length              0005 (5)
│ │ │ │ +C3E86   Flags               01 (1) 'Modification'
│ │ │ │ +C3E87   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3E8B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3E8D   Length              000B (11)
│ │ │ │ +C3E8F   Version             01 (1)
│ │ │ │ +C3E90   UID Size            04 (4)
│ │ │ │ +C3E91   UID                 00000000 (0)
│ │ │ │ +C3E95   GID Size            04 (4)
│ │ │ │ +C3E96   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3E9A CENTRAL HEADER #65    02014B50 (33639248)
│ │ │ │ +C3E9E Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3E9F Created OS            03 (3) 'Unix'
│ │ │ │ +C3EA0 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3EA1 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3EA2 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3EA4 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3EA6 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3EAA CRC                   2F406ADE (792750814)
│ │ │ │ +C3EAE Compressed Size       0000258D (9613)
│ │ │ │ +C3EB2 Uncompressed Size     0000BAA4 (47780)
│ │ │ │ +C3EB6 Filename Length       0019 (25)
│ │ │ │ +C3EB8 Extra Length          0018 (24)
│ │ │ │ +C3EBA Comment Length        0000 (0)
│ │ │ │ +C3EBC Disk Start            0000 (0)
│ │ │ │ +C3EBE Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3EC0 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3EC4 Local Header Offset   00079E8C (499340)
│ │ │ │ +C3EC8 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3EC8: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3EE1 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3EE3   Length              0005 (5)
│ │ │ │ +C3EE5   Flags               01 (1) 'Modification'
│ │ │ │ +C3EE6   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3EEA Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3EEC   Length              000B (11)
│ │ │ │ +C3EEE   Version             01 (1)
│ │ │ │ +C3EEF   UID Size            04 (4)
│ │ │ │ +C3EF0   UID                 00000000 (0)
│ │ │ │ +C3EF4   GID Size            04 (4)
│ │ │ │ +C3EF5   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3EF9 CENTRAL HEADER #66    02014B50 (33639248)
│ │ │ │ +C3EFD Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3EFE Created OS            03 (3) 'Unix'
│ │ │ │ +C3EFF Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3F00 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3F01 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3F03 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3F05 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3F09 CRC                   E061E754 (3764512596)
│ │ │ │ +C3F0D Compressed Size       00000EFD (3837)
│ │ │ │ +C3F11 Uncompressed Size     00003A2F (14895)
│ │ │ │ +C3F15 Filename Length       0024 (36)
│ │ │ │ +C3F17 Extra Length          0018 (24)
│ │ │ │ +C3F19 Comment Length        0000 (0)
│ │ │ │ +C3F1B Disk Start            0000 (0)
│ │ │ │ +C3F1D Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3F1F Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3F23 Local Header Offset   0007C46C (509036)
│ │ │ │ +C3F27 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3F27: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3F4B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3F4D   Length              0005 (5)
│ │ │ │ +C3F4F   Flags               01 (1) 'Modification'
│ │ │ │ +C3F50   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3F54 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3F56   Length              000B (11)
│ │ │ │ +C3F58   Version             01 (1)
│ │ │ │ +C3F59   UID Size            04 (4)
│ │ │ │ +C3F5A   UID                 00000000 (0)
│ │ │ │ +C3F5E   GID Size            04 (4)
│ │ │ │ +C3F5F   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3F63 CENTRAL HEADER #67    02014B50 (33639248)
│ │ │ │ +C3F67 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3F68 Created OS            03 (3) 'Unix'
│ │ │ │ +C3F69 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3F6A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3F6B General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3F6D Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3F6F Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3F73 CRC                   EC4F7E41 (3964632641)
│ │ │ │ +C3F77 Compressed Size       00001AE9 (6889)
│ │ │ │ +C3F7B Uncompressed Size     00005F7F (24447)
│ │ │ │ +C3F7F Filename Length       0017 (23)
│ │ │ │ +C3F81 Extra Length          0018 (24)
│ │ │ │ +C3F83 Comment Length        0000 (0)
│ │ │ │ +C3F85 Disk Start            0000 (0)
│ │ │ │ +C3F87 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3F89 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3F8D Local Header Offset   0007D3C7 (512967)
│ │ │ │ +C3F91 Filename              'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3F91: Filename 'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C3FA8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C3FAA   Length              0005 (5)
│ │ │ │ +C3FAC   Flags               01 (1) 'Modification'
│ │ │ │ +C3FAD   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C3FB1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C3FB3   Length              000B (11)
│ │ │ │ +C3FB5   Version             01 (1)
│ │ │ │ +C3FB6   UID Size            04 (4)
│ │ │ │ +C3FB7   UID                 00000000 (0)
│ │ │ │ +C3FBB   GID Size            04 (4)
│ │ │ │ +C3FBC   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C3FC0 CENTRAL HEADER #68    02014B50 (33639248)
│ │ │ │ +C3FC4 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C3FC5 Created OS            03 (3) 'Unix'
│ │ │ │ +C3FC6 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C3FC7 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C3FC8 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C3FCA Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C3FCC Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C3FD0 CRC                   11E32AF1 (300100337)
│ │ │ │ +C3FD4 Compressed Size       00000ED3 (3795)
│ │ │ │ +C3FD8 Uncompressed Size     000038E2 (14562)
│ │ │ │ +C3FDC Filename Length       0023 (35)
│ │ │ │ +C3FDE Extra Length          0018 (24)
│ │ │ │ +C3FE0 Comment Length        0000 (0)
│ │ │ │ +C3FE2 Disk Start            0000 (0)
│ │ │ │ +C3FE4 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C3FE6 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C3FEA Local Header Offset   0007EF01 (519937)
│ │ │ │ +C3FEE Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC3FEE: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C4011 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C4013   Length              0005 (5)
│ │ │ │ +C4015   Flags               01 (1) 'Modification'
│ │ │ │ +C4016   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C401A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C401C   Length              000B (11)
│ │ │ │ +C401E   Version             01 (1)
│ │ │ │ +C401F   UID Size            04 (4)
│ │ │ │ +C4020   UID                 00000000 (0)
│ │ │ │ +C4024   GID Size            04 (4)
│ │ │ │ +C4025   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C4029 CENTRAL HEADER #69    02014B50 (33639248)
│ │ │ │ +C402D Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C402E Created OS            03 (3) 'Unix'
│ │ │ │ +C402F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C4030 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C4031 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C4033 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C4035 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C4039 CRC                   2DB7929F (767005343)
│ │ │ │ +C403D Compressed Size       00000113 (275)
│ │ │ │ +C4041 Uncompressed Size     000001F3 (499)
│ │ │ │ +C4045 Filename Length       001B (27)
│ │ │ │ +C4047 Extra Length          0018 (24)
│ │ │ │ +C4049 Comment Length        0000 (0)
│ │ │ │ +C404B Disk Start            0000 (0)
│ │ │ │ +C404D Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C404F Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C4053 Local Header Offset   0007FE31 (523825)
│ │ │ │ +C4057 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC4057: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C4072 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C4074   Length              0005 (5)
│ │ │ │ +C4076   Flags               01 (1) 'Modification'
│ │ │ │ +C4077   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C407B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C407D   Length              000B (11)
│ │ │ │ +C407F   Version             01 (1)
│ │ │ │ +C4080   UID Size            04 (4)
│ │ │ │ +C4081   UID                 00000000 (0)
│ │ │ │ +C4085   GID Size            04 (4)
│ │ │ │ +C4086   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C408A CENTRAL HEADER #70    02014B50 (33639248)
│ │ │ │ +C408E Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C408F Created OS            03 (3) 'Unix'
│ │ │ │ +C4090 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C4091 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C4092 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C4094 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C4096 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C409A CRC                   CA00EBE0 (3389058016)
│ │ │ │ +C409E Compressed Size       0000188D (6285)
│ │ │ │ +C40A2 Uncompressed Size     00008FA8 (36776)
│ │ │ │ +C40A6 Filename Length       001D (29)
│ │ │ │ +C40A8 Extra Length          0018 (24)
│ │ │ │ +C40AA Comment Length        0000 (0)
│ │ │ │ +C40AC Disk Start            0000 (0)
│ │ │ │ +C40AE Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C40B0 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C40B4 Local Header Offset   0007FF99 (524185)
│ │ │ │ +C40B8 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC40B8: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C40D5 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C40D7   Length              0005 (5)
│ │ │ │ +C40D9   Flags               01 (1) 'Modification'
│ │ │ │ +C40DA   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C40DE Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C40E0   Length              000B (11)
│ │ │ │ +C40E2   Version             01 (1)
│ │ │ │ +C40E3   UID Size            04 (4)
│ │ │ │ +C40E4   UID                 00000000 (0)
│ │ │ │ +C40E8   GID Size            04 (4)
│ │ │ │ +C40E9   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C40ED CENTRAL HEADER #71    02014B50 (33639248)
│ │ │ │ +C40F1 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C40F2 Created OS            03 (3) 'Unix'
│ │ │ │ +C40F3 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C40F4 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C40F5 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C40F7 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C40F9 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C40FD CRC                   13F8A234 (335061556)
│ │ │ │ +C4101 Compressed Size       0000164C (5708)
│ │ │ │ +C4105 Uncompressed Size     00003A9B (15003)
│ │ │ │ +C4109 Filename Length       0015 (21)
│ │ │ │ +C410B Extra Length          0018 (24)
│ │ │ │ +C410D Comment Length        0000 (0)
│ │ │ │ +C410F Disk Start            0000 (0)
│ │ │ │ +C4111 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C4113 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C4117 Local Header Offset   0008187D (530557)
│ │ │ │ +C411B Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC411B: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C4130 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C4132   Length              0005 (5)
│ │ │ │ +C4134   Flags               01 (1) 'Modification'
│ │ │ │ +C4135   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C4139 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C413B   Length              000B (11)
│ │ │ │ +C413D   Version             01 (1)
│ │ │ │ +C413E   UID Size            04 (4)
│ │ │ │ +C413F   UID                 00000000 (0)
│ │ │ │ +C4143   GID Size            04 (4)
│ │ │ │ +C4144   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C4148 CENTRAL HEADER #72    02014B50 (33639248)
│ │ │ │ +C414C Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C414D Created OS            03 (3) 'Unix'
│ │ │ │ +C414E Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C414F Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C4150 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C4152 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C4154 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C4158 CRC                   A6BC1ACF (2797345487)
│ │ │ │ +C415C Compressed Size       000040C8 (16584)
│ │ │ │ +C4160 Uncompressed Size     000133AC (78764)
│ │ │ │ +C4164 Filename Length       0016 (22)
│ │ │ │ +C4166 Extra Length          0018 (24)
│ │ │ │ +C4168 Comment Length        0000 (0)
│ │ │ │ +C416A Disk Start            0000 (0)
│ │ │ │ +C416C Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C416E Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C4172 Local Header Offset   00082F18 (536344)
│ │ │ │ +C4176 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC4176: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C418C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C418E   Length              0005 (5)
│ │ │ │ +C4190   Flags               01 (1) 'Modification'
│ │ │ │ +C4191   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C4195 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C4197   Length              000B (11)
│ │ │ │ +C4199   Version             01 (1)
│ │ │ │ +C419A   UID Size            04 (4)
│ │ │ │ +C419B   UID                 00000000 (0)
│ │ │ │ +C419F   GID Size            04 (4)
│ │ │ │ +C41A0   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C41A4 CENTRAL HEADER #73    02014B50 (33639248)
│ │ │ │ +C41A8 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C41A9 Created OS            03 (3) 'Unix'
│ │ │ │ +C41AA Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C41AB Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C41AC General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C41AE Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C41B0 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C41B4 CRC                   3D47632B (1028088619)
│ │ │ │ +C41B8 Compressed Size       00003EB7 (16055)
│ │ │ │ +C41BC Uncompressed Size     0001C78B (116619)
│ │ │ │ +C41C0 Filename Length       0019 (25)
│ │ │ │ +C41C2 Extra Length          0018 (24)
│ │ │ │ +C41C4 Comment Length        0000 (0)
│ │ │ │ +C41C6 Disk Start            0000 (0)
│ │ │ │ +C41C8 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C41CA Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C41CE Local Header Offset   00087030 (553008)
│ │ │ │ +C41D2 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC41D2: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C41EB Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C41ED   Length              0005 (5)
│ │ │ │ +C41EF   Flags               01 (1) 'Modification'
│ │ │ │ +C41F0   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C41F4 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C41F6   Length              000B (11)
│ │ │ │ +C41F8   Version             01 (1)
│ │ │ │ +C41F9   UID Size            04 (4)
│ │ │ │ +C41FA   UID                 00000000 (0)
│ │ │ │ +C41FE   GID Size            04 (4)
│ │ │ │ +C41FF   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C4203 CENTRAL HEADER #74    02014B50 (33639248)
│ │ │ │ +C4207 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C4208 Created OS            03 (3) 'Unix'
│ │ │ │ +C4209 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C420A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C420B General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C420D Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C420F Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C4213 CRC                   339E52AB (866013867)
│ │ │ │ +C4217 Compressed Size       000008A3 (2211)
│ │ │ │ +C421B Uncompressed Size     000036CC (14028)
│ │ │ │ +C421F Filename Length       0011 (17)
│ │ │ │ +C4221 Extra Length          0018 (24)
│ │ │ │ +C4223 Comment Length        0000 (0)
│ │ │ │ +C4225 Disk Start            0000 (0)
│ │ │ │ +C4227 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C4229 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C422D Local Header Offset   0008AF3A (569146)
│ │ │ │ +C4231 Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC4231: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C4242 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C4244   Length              0005 (5)
│ │ │ │ +C4246   Flags               01 (1) 'Modification'
│ │ │ │ +C4247   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C424B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C424D   Length              000B (11)
│ │ │ │ +C424F   Version             01 (1)
│ │ │ │ +C4250   UID Size            04 (4)
│ │ │ │ +C4251   UID                 00000000 (0)
│ │ │ │ +C4255   GID Size            04 (4)
│ │ │ │ +C4256   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C425A CENTRAL HEADER #75    02014B50 (33639248)
│ │ │ │ +C425E Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C425F Created OS            03 (3) 'Unix'
│ │ │ │ +C4260 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C4261 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C4262 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C4264 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C4266 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C426A CRC                   FFBD87B5 (4290611125)
│ │ │ │ +C426E Compressed Size       000051A3 (20899)
│ │ │ │ +C4272 Uncompressed Size     0001F99A (129434)
│ │ │ │ +C4276 Filename Length       0015 (21)
│ │ │ │ +C4278 Extra Length          0018 (24)
│ │ │ │ +C427A Comment Length        0000 (0)
│ │ │ │ +C427C Disk Start            0000 (0)
│ │ │ │ +C427E Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C4280 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C4284 Local Header Offset   0008B828 (571432)
│ │ │ │ +C4288 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC4288: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C429D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C429F   Length              0005 (5)
│ │ │ │ +C42A1   Flags               01 (1) 'Modification'
│ │ │ │ +C42A2   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C42A6 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C42A8   Length              000B (11)
│ │ │ │ +C42AA   Version             01 (1)
│ │ │ │ +C42AB   UID Size            04 (4)
│ │ │ │ +C42AC   UID                 00000000 (0)
│ │ │ │ +C42B0   GID Size            04 (4)
│ │ │ │ +C42B1   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C42B5 CENTRAL HEADER #76    02014B50 (33639248)
│ │ │ │ +C42B9 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C42BA Created OS            03 (3) 'Unix'
│ │ │ │ +C42BB Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C42BC Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C42BD General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C42BF Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C42C1 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C42C5 CRC                   1BAA9D20 (464166176)
│ │ │ │ +C42C9 Compressed Size       00001C43 (7235)
│ │ │ │ +C42CD Uncompressed Size     00008AC8 (35528)
│ │ │ │ +C42D1 Filename Length       0019 (25)
│ │ │ │ +C42D3 Extra Length          0018 (24)
│ │ │ │ +C42D5 Comment Length        0000 (0)
│ │ │ │ +C42D7 Disk Start            0000 (0)
│ │ │ │ +C42D9 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C42DB Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C42DF Local Header Offset   00090A1A (592410)
│ │ │ │ +C42E3 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC42E3: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C42FC Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C42FE   Length              0005 (5)
│ │ │ │ +C4300   Flags               01 (1) 'Modification'
│ │ │ │ +C4301   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C4305 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C4307   Length              000B (11)
│ │ │ │ +C4309   Version             01 (1)
│ │ │ │ +C430A   UID Size            04 (4)
│ │ │ │ +C430B   UID                 00000000 (0)
│ │ │ │ +C430F   GID Size            04 (4)
│ │ │ │ +C4310   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C4314 CENTRAL HEADER #77    02014B50 (33639248)
│ │ │ │ +C4318 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C4319 Created OS            03 (3) 'Unix'
│ │ │ │ +C431A Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C431B Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C431C General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C431E Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C4320 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C4324 CRC                   FAE8837D (4209542013)
│ │ │ │ +C4328 Compressed Size       00000D92 (3474)
│ │ │ │ +C432C Uncompressed Size     00002EA4 (11940)
│ │ │ │ +C4330 Filename Length       0018 (24)
│ │ │ │ +C4332 Extra Length          0018 (24)
│ │ │ │ +C4334 Comment Length        0000 (0)
│ │ │ │ +C4336 Disk Start            0000 (0)
│ │ │ │ +C4338 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C433A Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C433E Local Header Offset   000926B0 (599728)
│ │ │ │ +C4342 Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC4342: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C435A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C435C   Length              0005 (5)
│ │ │ │ +C435E   Flags               01 (1) 'Modification'
│ │ │ │ +C435F   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C4363 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C4365   Length              000B (11)
│ │ │ │ +C4367   Version             01 (1)
│ │ │ │ +C4368   UID Size            04 (4)
│ │ │ │ +C4369   UID                 00000000 (0)
│ │ │ │ +C436D   GID Size            04 (4)
│ │ │ │ +C436E   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C4372 CENTRAL HEADER #78    02014B50 (33639248)
│ │ │ │ +C4376 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C4377 Created OS            03 (3) 'Unix'
│ │ │ │ +C4378 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C4379 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C437A General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C437C Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C437E Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C4382 CRC                   535B63FB (1398498299)
│ │ │ │ +C4386 Compressed Size       000001DF (479)
│ │ │ │ +C438A Uncompressed Size     00000323 (803)
│ │ │ │ +C438E Filename Length       0011 (17)
│ │ │ │ +C4390 Extra Length          0018 (24)
│ │ │ │ +C4392 Comment Length        0000 (0)
│ │ │ │ +C4394 Disk Start            0000 (0)
│ │ │ │ +C4396 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C4398 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C439C Local Header Offset   00093494 (603284)
│ │ │ │ +C43A0 Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC43A0: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C43B1 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C43B3   Length              0005 (5)
│ │ │ │ +C43B5   Flags               01 (1) 'Modification'
│ │ │ │ +C43B6   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C43BA Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C43BC   Length              000B (11)
│ │ │ │ +C43BE   Version             01 (1)
│ │ │ │ +C43BF   UID Size            04 (4)
│ │ │ │ +C43C0   UID                 00000000 (0)
│ │ │ │ +C43C4   GID Size            04 (4)
│ │ │ │ +C43C5   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C43C9 CENTRAL HEADER #79    02014B50 (33639248)
│ │ │ │ +C43CD Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C43CE Created OS            03 (3) 'Unix'
│ │ │ │ +C43CF Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C43D0 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C43D1 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C43D3 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C43D5 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C43D9 CRC                   32CAD6D8 (852154072)
│ │ │ │ +C43DD Compressed Size       000006BE (1726)
│ │ │ │ +C43E1 Uncompressed Size     0000141F (5151)
│ │ │ │ +C43E5 Filename Length       0019 (25)
│ │ │ │ +C43E7 Extra Length          0018 (24)
│ │ │ │ +C43E9 Comment Length        0000 (0)
│ │ │ │ +C43EB Disk Start            0000 (0)
│ │ │ │ +C43ED Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C43EF Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C43F3 Local Header Offset   000936BE (603838)
│ │ │ │ +C43F7 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC43F7: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C4410 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C4412   Length              0005 (5)
│ │ │ │ +C4414   Flags               01 (1) 'Modification'
│ │ │ │ +C4415   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C4419 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C441B   Length              000B (11)
│ │ │ │ +C441D   Version             01 (1)
│ │ │ │ +C441E   UID Size            04 (4)
│ │ │ │ +C441F   UID                 00000000 (0)
│ │ │ │ +C4423   GID Size            04 (4)
│ │ │ │ +C4424   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C4428 CENTRAL HEADER #80    02014B50 (33639248)
│ │ │ │ +C442C Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C442D Created OS            03 (3) 'Unix'
│ │ │ │ +C442E Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C442F Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C4430 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C4432 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C4434 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C4438 CRC                   3082FD4D (813890893)
│ │ │ │ +C443C Compressed Size       00001B8B (7051)
│ │ │ │ +C4440 Uncompressed Size     00009F5F (40799)
│ │ │ │ +C4444 Filename Length       0018 (24)
│ │ │ │ +C4446 Extra Length          0018 (24)
│ │ │ │ +C4448 Comment Length        0000 (0)
│ │ │ │ +C444A Disk Start            0000 (0)
│ │ │ │ +C444C Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C444E Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C4452 Local Header Offset   00093DCF (605647)
│ │ │ │ +C4456 Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC4456: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C446E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C4470   Length              0005 (5)
│ │ │ │ +C4472   Flags               01 (1) 'Modification'
│ │ │ │ +C4473   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C4477 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C4479   Length              000B (11)
│ │ │ │ +C447B   Version             01 (1)
│ │ │ │ +C447C   UID Size            04 (4)
│ │ │ │ +C447D   UID                 00000000 (0)
│ │ │ │ +C4481   GID Size            04 (4)
│ │ │ │ +C4482   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C4486 CENTRAL HEADER #81    02014B50 (33639248)
│ │ │ │ +C448A Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C448B Created OS            03 (3) 'Unix'
│ │ │ │ +C448C Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C448D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C448E General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C4490 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C4492 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C4496 CRC                   1E04A61F (503621151)
│ │ │ │ +C449A Compressed Size       00001700 (5888)
│ │ │ │ +C449E Uncompressed Size     00008B12 (35602)
│ │ │ │ +C44A2 Filename Length       0012 (18)
│ │ │ │ +C44A4 Extra Length          0018 (24)
│ │ │ │ +C44A6 Comment Length        0000 (0)
│ │ │ │ +C44A8 Disk Start            0000 (0)
│ │ │ │ +C44AA Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C44AC Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C44B0 Local Header Offset   000959AC (612780)
│ │ │ │ +C44B4 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC44B4: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C44C6 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C44C8   Length              0005 (5)
│ │ │ │ +C44CA   Flags               01 (1) 'Modification'
│ │ │ │ +C44CB   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C44CF Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C44D1   Length              000B (11)
│ │ │ │ +C44D3   Version             01 (1)
│ │ │ │ +C44D4   UID Size            04 (4)
│ │ │ │ +C44D5   UID                 00000000 (0)
│ │ │ │ +C44D9   GID Size            04 (4)
│ │ │ │ +C44DA   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C44DE CENTRAL HEADER #82    02014B50 (33639248)
│ │ │ │ +C44E2 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C44E3 Created OS            03 (3) 'Unix'
│ │ │ │ +C44E4 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C44E5 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C44E6 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C44E8 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C44EA Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C44EE CRC                   C9194D7F (3373878655)
│ │ │ │ +C44F2 Compressed Size       00001E0B (7691)
│ │ │ │ +C44F6 Uncompressed Size     00008823 (34851)
│ │ │ │ +C44FA Filename Length       0016 (22)
│ │ │ │ +C44FC Extra Length          0018 (24)
│ │ │ │ +C44FE Comment Length        0000 (0)
│ │ │ │ +C4500 Disk Start            0000 (0)
│ │ │ │ +C4502 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C4504 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C4508 Local Header Offset   000970F8 (618744)
│ │ │ │ +C450C Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC450C: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C4522 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C4524   Length              0005 (5)
│ │ │ │ +C4526   Flags               01 (1) 'Modification'
│ │ │ │ +C4527   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C452B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C452D   Length              000B (11)
│ │ │ │ +C452F   Version             01 (1)
│ │ │ │ +C4530   UID Size            04 (4)
│ │ │ │ +C4531   UID                 00000000 (0)
│ │ │ │ +C4535   GID Size            04 (4)
│ │ │ │ +C4536   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C453A CENTRAL HEADER #83    02014B50 (33639248)
│ │ │ │ +C453E Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C453F Created OS            03 (3) 'Unix'
│ │ │ │ +C4540 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C4541 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C4542 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C4544 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C4546 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C454A CRC                   FC5E70B2 (4234047666)
│ │ │ │ +C454E Compressed Size       000029A9 (10665)
│ │ │ │ +C4552 Uncompressed Size     0000D04F (53327)
│ │ │ │ +C4556 Filename Length       001A (26)
│ │ │ │ +C4558 Extra Length          0018 (24)
│ │ │ │ +C455A Comment Length        0000 (0)
│ │ │ │ +C455C Disk Start            0000 (0)
│ │ │ │ +C455E Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C4560 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C4564 Local Header Offset   00098F53 (626515)
│ │ │ │ +C4568 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC4568: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C4582 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C4584   Length              0005 (5)
│ │ │ │ +C4586   Flags               01 (1) 'Modification'
│ │ │ │ +C4587   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C458B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C458D   Length              000B (11)
│ │ │ │ +C458F   Version             01 (1)
│ │ │ │ +C4590   UID Size            04 (4)
│ │ │ │ +C4591   UID                 00000000 (0)
│ │ │ │ +C4595   GID Size            04 (4)
│ │ │ │ +C4596   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C459A CENTRAL HEADER #84    02014B50 (33639248)
│ │ │ │ +C459E Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C459F Created OS            03 (3) 'Unix'
│ │ │ │ +C45A0 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C45A1 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C45A2 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C45A4 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C45A6 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C45AA CRC                   8529CAAD (2234108589)
│ │ │ │ +C45AE Compressed Size       000009AB (2475)
│ │ │ │ +C45B2 Uncompressed Size     00001DAC (7596)
│ │ │ │ +C45B6 Filename Length       0018 (24)
│ │ │ │ +C45B8 Extra Length          0018 (24)
│ │ │ │ +C45BA Comment Length        0000 (0)
│ │ │ │ +C45BC Disk Start            0000 (0)
│ │ │ │ +C45BE Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C45C0 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C45C4 Local Header Offset   0009B950 (637264)
│ │ │ │ +C45C8 Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC45C8: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C45E0 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C45E2   Length              0005 (5)
│ │ │ │ +C45E4   Flags               01 (1) 'Modification'
│ │ │ │ +C45E5   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C45E9 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C45EB   Length              000B (11)
│ │ │ │ +C45ED   Version             01 (1)
│ │ │ │ +C45EE   UID Size            04 (4)
│ │ │ │ +C45EF   UID                 00000000 (0)
│ │ │ │ +C45F3   GID Size            04 (4)
│ │ │ │ +C45F4   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C45F8 CENTRAL HEADER #85    02014B50 (33639248)
│ │ │ │ +C45FC Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C45FD Created OS            03 (3) 'Unix'
│ │ │ │ +C45FE Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C45FF Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C4600 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C4602 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C4604 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C4608 CRC                   F0556E9A (4032130714)
│ │ │ │ +C460C Compressed Size       000152EE (86766)
│ │ │ │ +C4610 Uncompressed Size     000159F8 (88568)
│ │ │ │ +C4614 Filename Length       001E (30)
│ │ │ │ +C4616 Extra Length          0018 (24)
│ │ │ │ +C4618 Comment Length        0000 (0)
│ │ │ │ +C461A Disk Start            0000 (0)
│ │ │ │ +C461C Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C461E Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C4622 Local Header Offset   0009C34D (639821)
│ │ │ │ +C4626 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC4626: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C4644 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C4646   Length              0005 (5)
│ │ │ │ +C4648   Flags               01 (1) 'Modification'
│ │ │ │ +C4649   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C464D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C464F   Length              000B (11)
│ │ │ │ +C4651   Version             01 (1)
│ │ │ │ +C4652   UID Size            04 (4)
│ │ │ │ +C4653   UID                 00000000 (0)
│ │ │ │ +C4657   GID Size            04 (4)
│ │ │ │ +C4658   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C465C CENTRAL HEADER #86    02014B50 (33639248)
│ │ │ │ +C4660 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C4661 Created OS            03 (3) 'Unix'
│ │ │ │ +C4662 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C4663 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C4664 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C4666 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C4668 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C466C CRC                   F5E2129F (4125233823)
│ │ │ │ +C4670 Compressed Size       000016BC (5820)
│ │ │ │ +C4674 Uncompressed Size     000016CD (5837)
│ │ │ │ +C4678 Filename Length       0015 (21)
│ │ │ │ +C467A Extra Length          0018 (24)
│ │ │ │ +C467C Comment Length        0000 (0)
│ │ │ │ +C467E Disk Start            0000 (0)
│ │ │ │ +C4680 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C4682 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C4686 Local Header Offset   000B1693 (726675)
│ │ │ │ +C468A Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC468A: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C469F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C46A1   Length              0005 (5)
│ │ │ │ +C46A3   Flags               01 (1) 'Modification'
│ │ │ │ +C46A4   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C46A8 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C46AA   Length              000B (11)
│ │ │ │ +C46AC   Version             01 (1)
│ │ │ │ +C46AD   UID Size            04 (4)
│ │ │ │ +C46AE   UID                 00000000 (0)
│ │ │ │ +C46B2   GID Size            04 (4)
│ │ │ │ +C46B3   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C46B7 CENTRAL HEADER #87    02014B50 (33639248)
│ │ │ │ +C46BB Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C46BC Created OS            03 (3) 'Unix'
│ │ │ │ +C46BD Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C46BE Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C46BF General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C46C1 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C46C3 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C46C7 CRC                   F5E2129F (4125233823)
│ │ │ │ +C46CB Compressed Size       000016BC (5820)
│ │ │ │ +C46CF Uncompressed Size     000016CD (5837)
│ │ │ │ +C46D3 Filename Length       001C (28)
│ │ │ │ +C46D5 Extra Length          0018 (24)
│ │ │ │ +C46D7 Comment Length        0000 (0)
│ │ │ │ +C46D9 Disk Start            0000 (0)
│ │ │ │ +C46DB Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C46DD Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C46E1 Local Header Offset   000B2D9E (732574)
│ │ │ │ +C46E5 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC46E5: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C4701 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C4703   Length              0005 (5)
│ │ │ │ +C4705   Flags               01 (1) 'Modification'
│ │ │ │ +C4706   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C470A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C470C   Length              000B (11)
│ │ │ │ +C470E   Version             01 (1)
│ │ │ │ +C470F   UID Size            04 (4)
│ │ │ │ +C4710   UID                 00000000 (0)
│ │ │ │ +C4714   GID Size            04 (4)
│ │ │ │ +C4715   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C4719 CENTRAL HEADER #88    02014B50 (33639248)
│ │ │ │ +C471D Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C471E Created OS            03 (3) 'Unix'
│ │ │ │ +C471F Extract Zip Spec      0A (10) '1.0'
│ │ │ │ +C4720 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C4721 General Purpose Flag  0000 (0)
│ │ │ │ +C4723 Compression Method    0000 (0) 'Stored'
│ │ │ │ +C4725 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C4729 CRC                   FC95F24B (4237685323)
│ │ │ │ +C472D Compressed Size       00001B84 (7044)
│ │ │ │ +C4731 Uncompressed Size     00001B84 (7044)
│ │ │ │ +C4735 Filename Length       0016 (22)
│ │ │ │ +C4737 Extra Length          0018 (24)
│ │ │ │ +C4739 Comment Length        0000 (0)
│ │ │ │ +C473B Disk Start            0000 (0)
│ │ │ │ +C473D Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C473F Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C4743 Local Header Offset   000B44B0 (738480)
│ │ │ │ +C4747 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC4747: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C475D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C475F   Length              0005 (5)
│ │ │ │ +C4761   Flags               01 (1) 'Modification'
│ │ │ │ +C4762   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C4766 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C4768   Length              000B (11)
│ │ │ │ +C476A   Version             01 (1)
│ │ │ │ +C476B   UID Size            04 (4)
│ │ │ │ +C476C   UID                 00000000 (0)
│ │ │ │ +C4770   GID Size            04 (4)
│ │ │ │ +C4771   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C4775 CENTRAL HEADER #89    02014B50 (33639248)
│ │ │ │ +C4779 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C477A Created OS            03 (3) 'Unix'
│ │ │ │ +C477B Extract Zip Spec      0A (10) '1.0'
│ │ │ │ +C477C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C477D General Purpose Flag  0000 (0)
│ │ │ │ +C477F Compression Method    0000 (0) 'Stored'
│ │ │ │ +C4781 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C4785 CRC                   D0D71F86 (3503759238)
│ │ │ │ +C4789 Compressed Size       00000B7B (2939)
│ │ │ │ +C478D Uncompressed Size     00000B7B (2939)
│ │ │ │ +C4791 Filename Length       0016 (22)
│ │ │ │ +C4793 Extra Length          0018 (24)
│ │ │ │ +C4795 Comment Length        0000 (0)
│ │ │ │ +C4797 Disk Start            0000 (0)
│ │ │ │ +C4799 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C479B Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C479F Local Header Offset   000B6084 (745604)
│ │ │ │ +C47A3 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC47A3: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C47B9 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C47BB   Length              0005 (5)
│ │ │ │ +C47BD   Flags               01 (1) 'Modification'
│ │ │ │ +C47BE   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C47C2 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C47C4   Length              000B (11)
│ │ │ │ +C47C6   Version             01 (1)
│ │ │ │ +C47C7   UID Size            04 (4)
│ │ │ │ +C47C8   UID                 00000000 (0)
│ │ │ │ +C47CC   GID Size            04 (4)
│ │ │ │ +C47CD   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C47D1 CENTRAL HEADER #90    02014B50 (33639248)
│ │ │ │ +C47D5 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C47D6 Created OS            03 (3) 'Unix'
│ │ │ │ +C47D7 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ +C47D8 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C47D9 General Purpose Flag  0000 (0)
│ │ │ │ +C47DB Compression Method    0000 (0) 'Stored'
│ │ │ │ +C47DD Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C47E1 CRC                   FFF9C4D2 (4294558930)
│ │ │ │ +C47E5 Compressed Size       0000138F (5007)
│ │ │ │ +C47E9 Uncompressed Size     0000138F (5007)
│ │ │ │ +C47ED Filename Length       0016 (22)
│ │ │ │ +C47EF Extra Length          0018 (24)
│ │ │ │ +C47F1 Comment Length        0000 (0)
│ │ │ │ +C47F3 Disk Start            0000 (0)
│ │ │ │ +C47F5 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C47F7 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C47FB Local Header Offset   000B6C4F (748623)
│ │ │ │ +C47FF Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC47FF: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C4815 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C4817   Length              0005 (5)
│ │ │ │ +C4819   Flags               01 (1) 'Modification'
│ │ │ │ +C481A   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C481E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C4820   Length              000B (11)
│ │ │ │ +C4822   Version             01 (1)
│ │ │ │ +C4823   UID Size            04 (4)
│ │ │ │ +C4824   UID                 00000000 (0)
│ │ │ │ +C4828   GID Size            04 (4)
│ │ │ │ +C4829   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C482D CENTRAL HEADER #91    02014B50 (33639248)
│ │ │ │ +C4831 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C4832 Created OS            03 (3) 'Unix'
│ │ │ │ +C4833 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ +C4834 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C4835 General Purpose Flag  0000 (0)
│ │ │ │ +C4837 Compression Method    0000 (0) 'Stored'
│ │ │ │ +C4839 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C483D CRC                   A1037E8E (2701360782)
│ │ │ │ +C4841 Compressed Size       0000145E (5214)
│ │ │ │ +C4845 Uncompressed Size     0000145E (5214)
│ │ │ │ +C4849 Filename Length       0016 (22)
│ │ │ │ +C484B Extra Length          0018 (24)
│ │ │ │ +C484D Comment Length        0000 (0)
│ │ │ │ +C484F Disk Start            0000 (0)
│ │ │ │ +C4851 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C4853 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C4857 Local Header Offset   000B802E (753710)
│ │ │ │ +C485B Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC485B: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C4871 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C4873   Length              0005 (5)
│ │ │ │ +C4875   Flags               01 (1) 'Modification'
│ │ │ │ +C4876   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C487A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C487C   Length              000B (11)
│ │ │ │ +C487E   Version             01 (1)
│ │ │ │ +C487F   UID Size            04 (4)
│ │ │ │ +C4880   UID                 00000000 (0)
│ │ │ │ +C4884   GID Size            04 (4)
│ │ │ │ +C4885   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C4889 CENTRAL HEADER #92    02014B50 (33639248)
│ │ │ │ +C488D Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C488E Created OS            03 (3) 'Unix'
│ │ │ │ +C488F Extract Zip Spec      0A (10) '1.0'
│ │ │ │ +C4890 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C4891 General Purpose Flag  0000 (0)
│ │ │ │ +C4893 Compression Method    0000 (0) 'Stored'
│ │ │ │ +C4895 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C4899 CRC                   5E9E64F1 (1587438833)
│ │ │ │ +C489D Compressed Size       000008EC (2284)
│ │ │ │ +C48A1 Uncompressed Size     000008EC (2284)
│ │ │ │ +C48A5 Filename Length       0016 (22)
│ │ │ │ +C48A7 Extra Length          0018 (24)
│ │ │ │ +C48A9 Comment Length        0000 (0)
│ │ │ │ +C48AB Disk Start            0000 (0)
│ │ │ │ +C48AD Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C48AF Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C48B3 Local Header Offset   000B94DC (759004)
│ │ │ │ +C48B7 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC48B7: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C48CD Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C48CF   Length              0005 (5)
│ │ │ │ +C48D1   Flags               01 (1) 'Modification'
│ │ │ │ +C48D2   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C48D6 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C48D8   Length              000B (11)
│ │ │ │ +C48DA   Version             01 (1)
│ │ │ │ +C48DB   UID Size            04 (4)
│ │ │ │ +C48DC   UID                 00000000 (0)
│ │ │ │ +C48E0   GID Size            04 (4)
│ │ │ │ +C48E1   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C48E5 CENTRAL HEADER #93    02014B50 (33639248)
│ │ │ │ +C48E9 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C48EA Created OS            03 (3) 'Unix'
│ │ │ │ +C48EB Extract Zip Spec      0A (10) '1.0'
│ │ │ │ +C48EC Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C48ED General Purpose Flag  0000 (0)
│ │ │ │ +C48EF Compression Method    0000 (0) 'Stored'
│ │ │ │ +C48F1 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C48F5 CRC                   42E340AB (1122189483)
│ │ │ │ +C48F9 Compressed Size       00001F2E (7982)
│ │ │ │ +C48FD Uncompressed Size     00001F2E (7982)
│ │ │ │ +C4901 Filename Length       001E (30)
│ │ │ │ +C4903 Extra Length          0018 (24)
│ │ │ │ +C4905 Comment Length        0000 (0)
│ │ │ │ +C4907 Disk Start            0000 (0)
│ │ │ │ +C4909 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C490B Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C490F Local Header Offset   000B9E18 (761368)
│ │ │ │ +C4913 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC4913: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C4931 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C4933   Length              0005 (5)
│ │ │ │ +C4935   Flags               01 (1) 'Modification'
│ │ │ │ +C4936   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C493A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C493C   Length              000B (11)
│ │ │ │ +C493E   Version             01 (1)
│ │ │ │ +C493F   UID Size            04 (4)
│ │ │ │ +C4940   UID                 00000000 (0)
│ │ │ │ +C4944   GID Size            04 (4)
│ │ │ │ +C4945   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C4949 CENTRAL HEADER #94    02014B50 (33639248)
│ │ │ │ +C494D Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C494E Created OS            03 (3) 'Unix'
│ │ │ │ +C494F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C4950 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C4951 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C4953 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C4955 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C4959 CRC                   28F7826D (687309421)
│ │ │ │ +C495D Compressed Size       00003D80 (15744)
│ │ │ │ +C4961 Uncompressed Size     000166B0 (91824)
│ │ │ │ +C4965 Filename Length       001A (26)
│ │ │ │ +C4967 Extra Length          0018 (24)
│ │ │ │ +C4969 Comment Length        0000 (0)
│ │ │ │ +C496B Disk Start            0000 (0)
│ │ │ │ +C496D Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C496F Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C4973 Local Header Offset   000BBD9E (769438)
│ │ │ │ +C4977 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC4977: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C4991 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C4993   Length              0005 (5)
│ │ │ │ +C4995   Flags               01 (1) 'Modification'
│ │ │ │ +C4996   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C499A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C499C   Length              000B (11)
│ │ │ │ +C499E   Version             01 (1)
│ │ │ │ +C499F   UID Size            04 (4)
│ │ │ │ +C49A0   UID                 00000000 (0)
│ │ │ │ +C49A4   GID Size            04 (4)
│ │ │ │ +C49A5   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C49A9 CENTRAL HEADER #95    02014B50 (33639248)
│ │ │ │ +C49AD Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C49AE Created OS            03 (3) 'Unix'
│ │ │ │ +C49AF Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C49B0 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C49B1 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C49B3 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C49B5 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C49B9 CRC                   B0D0A5F7 (2966463991)
│ │ │ │ +C49BD Compressed Size       000029D0 (10704)
│ │ │ │ +C49C1 Uncompressed Size     0000BB3A (47930)
│ │ │ │ +C49C5 Filename Length       0018 (24)
│ │ │ │ +C49C7 Extra Length          0018 (24)
│ │ │ │ +C49C9 Comment Length        0000 (0)
│ │ │ │ +C49CB Disk Start            0000 (0)
│ │ │ │ +C49CD Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C49CF Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C49D3 Local Header Offset   000BFB72 (785266)
│ │ │ │ +C49D7 Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC49D7: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C49EF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C49F1   Length              0005 (5)
│ │ │ │ +C49F3   Flags               01 (1) 'Modification'
│ │ │ │ +C49F4   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C49F8 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C49FA   Length              000B (11)
│ │ │ │ +C49FC   Version             01 (1)
│ │ │ │ +C49FD   UID Size            04 (4)
│ │ │ │ +C49FE   UID                 00000000 (0)
│ │ │ │ +C4A02   GID Size            04 (4)
│ │ │ │ +C4A03   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C4A07 CENTRAL HEADER #96    02014B50 (33639248)
│ │ │ │ +C4A0B Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C4A0C Created OS            03 (3) 'Unix'
│ │ │ │ +C4A0D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C4A0E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C4A0F General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C4A11 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C4A13 Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C4A17 CRC                   DCB3B516 (3702764822)
│ │ │ │ +C4A1B Compressed Size       000000AE (174)
│ │ │ │ +C4A1F Uncompressed Size     000000FC (252)
│ │ │ │ +C4A23 Filename Length       0016 (22)
│ │ │ │ +C4A25 Extra Length          0018 (24)
│ │ │ │ +C4A27 Comment Length        0000 (0)
│ │ │ │ +C4A29 Disk Start            0000 (0)
│ │ │ │ +C4A2B Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C4A2D Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C4A31 Local Header Offset   000C2594 (796052)
│ │ │ │ +C4A35 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC4A35: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C4A4B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C4A4D   Length              0005 (5)
│ │ │ │ +C4A4F   Flags               01 (1) 'Modification'
│ │ │ │ +C4A50   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C4A54 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C4A56   Length              000B (11)
│ │ │ │ +C4A58   Version             01 (1)
│ │ │ │ +C4A59   UID Size            04 (4)
│ │ │ │ +C4A5A   UID                 00000000 (0)
│ │ │ │ +C4A5E   GID Size            04 (4)
│ │ │ │ +C4A5F   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C4A63 CENTRAL HEADER #97    02014B50 (33639248)
│ │ │ │ +C4A67 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +C4A68 Created OS            03 (3) 'Unix'
│ │ │ │ +C4A69 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +C4A6A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +C4A6B General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +C4A6D Compression Method    0008 (8) 'Deflated'
│ │ │ │ +C4A6F Modification Time     5C9521B3 (1553277363) 'Tue Apr 21 04:13:38 2026'
│ │ │ │ +C4A73 CRC                   58439733 (1480824627)
│ │ │ │ +C4A77 Compressed Size       00000077 (119)
│ │ │ │ +C4A7B Uncompressed Size     000000A2 (162)
│ │ │ │ +C4A7F Filename Length       002D (45)
│ │ │ │ +C4A81 Extra Length          0018 (24)
│ │ │ │ +C4A83 Comment Length        0000 (0)
│ │ │ │ +C4A85 Disk Start            0000 (0)
│ │ │ │ +C4A87 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +C4A89 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +C4A8D Local Header Offset   000C2692 (796306)
│ │ │ │ +C4A91 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC4A91: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +C4ABE Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +C4AC0   Length              0005 (5)
│ │ │ │ +C4AC2   Flags               01 (1) 'Modification'
│ │ │ │ +C4AC3   Modification Time   69E6F973 (1776744819) 'Tue Apr 21 04:13:39 2026'
│ │ │ │ +C4AC7 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +C4AC9   Length              000B (11)
│ │ │ │ +C4ACB   Version             01 (1)
│ │ │ │ +C4ACC   UID Size            04 (4)
│ │ │ │ +C4ACD   UID                 00000000 (0)
│ │ │ │ +C4AD1   GID Size            04 (4)
│ │ │ │ +C4AD2   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +C4AD6 END CENTRAL HEADER    06054B50 (101010256)
│ │ │ │ +C4ADA Number of this disk   0000 (0)
│ │ │ │ +C4ADC Central Dir Disk no   0000 (0)
│ │ │ │ +C4ADE Entries in this disk  0061 (97)
│ │ │ │ +C4AE0 Total Entries         0061 (97)
│ │ │ │ +C4AE2 Size of Central Dir   00002366 (9062)
│ │ │ │ +C4AE6 Offset to Central Dir 000C2770 (796528)
│ │ │ │ +C4AEA Comment Length        0000 (0)
│ │ │ │  #
│ │ │ │  # Warning Count: 194
│ │ │ │  #
│ │ │ │  # Done
│ │ │ ├── filetype from file(1)
│ │ │ │ @@ -1 +1 @@
│ │ │ │ -Zip archive data, made by v6.1 UNIX, extract using at least v1.0, last modified Apr 15 2026 20:07:06, uncompressed size 20, method=store
│ │ │ │ +Zip archive data, made by v6.1 UNIX, extract using at least v1.0, last modified Apr 21 2026 04:13:38, uncompressed size 20, method=store
│ │ │ ├── OEBPS/vulnerabilities.xhtml
│ │ │ │ @@ -48,69 +48,69 @@
│ │ │ │  vulnerability (<code class="inline">affected</code>), the affected Erlang/OTP releases, namely <code class="inline">28.0</code>,
│ │ │ │  <code class="inline">28.0.1</code>, and <code class="inline">28.0.2</code>, and the Erlang/OTP application that was vulnerable
│ │ │ │  in application version <code class="inline">ssh@5.3</code>, <code class="inline">ssh@5.3.1</code>, and <code class="inline">ssh@5.3.2</code>.
│ │ │ │  Erlang/OTP reports the affected versions using the release and the
│ │ │ │  application versions because it is possible to update the application independently
│ │ │ │  from the release.
│ │ │ │  In some cases, there may be an optional action statement that describes a workaround
│ │ │ │ -to avoid the mentioned vulnerability.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0959908934-1">{</span><span class="w">
│ │ │ │ -  </span><span class="s">&quot;vulnerability&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0959908934-2">{</span><span class="w">
│ │ │ │ +to avoid the mentioned vulnerability.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7858127689-1">{</span><span class="w">
│ │ │ │ +  </span><span class="s">&quot;vulnerability&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="7858127689-2">{</span><span class="w">
│ │ │ │      </span><span class="s">&quot;name&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;CVE-2025-48038&quot;</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="0959908934-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="7858127689-2">}</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="s">&quot;timestamp&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;2025-09-16T08:22:13.223967395Z&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="s">&quot;products&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0959908934-3">[</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0959908934-4">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0&quot;</span><span class="w"> </span><span class="p" data-group-id="0959908934-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0959908934-5">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0.1&quot;</span><span class="w"> </span><span class="p" data-group-id="0959908934-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0959908934-6">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0.2&quot;</span><span class="w"> </span><span class="p" data-group-id="0959908934-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0959908934-7">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:otp/ssh@5.3&quot;</span><span class="w"> </span><span class="p" data-group-id="0959908934-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0959908934-8">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:otp/ssh@5.3.1&quot;</span><span class="w"> </span><span class="p" data-group-id="0959908934-8">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0959908934-9">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:otp/ssh@5.3.2&quot;</span><span class="w"> </span><span class="p" data-group-id="0959908934-9">}</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="0959908934-3">]</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="s">&quot;products&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="7858127689-3">[</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7858127689-4">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0&quot;</span><span class="w"> </span><span class="p" data-group-id="7858127689-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7858127689-5">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0.1&quot;</span><span class="w"> </span><span class="p" data-group-id="7858127689-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7858127689-6">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0.2&quot;</span><span class="w"> </span><span class="p" data-group-id="7858127689-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7858127689-7">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:otp/ssh@5.3&quot;</span><span class="w"> </span><span class="p" data-group-id="7858127689-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7858127689-8">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:otp/ssh@5.3.1&quot;</span><span class="w"> </span><span class="p" data-group-id="7858127689-8">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7858127689-9">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:otp/ssh@5.3.2&quot;</span><span class="w"> </span><span class="p" data-group-id="7858127689-9">}</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="7858127689-3">]</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="s">&quot;status&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;affected&quot;</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="s">&quot;action_statement&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;Update to any of the following versions: pkg:otp/ssh@5.3.3&quot;</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="s">&quot;action_statement_timestamp&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;2025-09-16T08:22:13.223967395Z&quot;</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0959908934-1">}</span><span class="p">,</span></code></pre><p>Erlang/OTP reports the fixed version in a similar fashion as follows, in the same document.
│ │ │ │ +</span><span class="p" data-group-id="7858127689-1">}</span><span class="p">,</span></code></pre><p>Erlang/OTP reports the fixed version in a similar fashion as follows, in the same document.
│ │ │ │  As an example, there is a new statement for <code class="inline">CVE-2025-48038</code> with status <code class="inline">fixed</code>,
│ │ │ │  that links to the first release that do not suffer from <code class="inline">CVE-2025-48038</code>, namely
│ │ │ │ -OTP version <code class="inline">28.0.3</code> and application <code class="inline">ssh@5.3.3</code>. </p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5585156685-1">{</span><span class="w">
│ │ │ │ -  </span><span class="s">&quot;vulnerability&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="5585156685-2">{</span><span class="w">
│ │ │ │ +OTP version <code class="inline">28.0.3</code> and application <code class="inline">ssh@5.3.3</code>. </p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9573354036-1">{</span><span class="w">
│ │ │ │ +  </span><span class="s">&quot;vulnerability&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="9573354036-2">{</span><span class="w">
│ │ │ │      </span><span class="s">&quot;name&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;CVE-2025-48038&quot;</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="5585156685-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="9573354036-2">}</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="s">&quot;timestamp&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;2025-09-16T08:22:13.241103494Z&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="s">&quot;products&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="5585156685-3">[</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5585156685-4">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0.4&quot;</span><span class="w"> </span><span class="p" data-group-id="5585156685-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5585156685-5">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0.3&quot;</span><span class="w"> </span><span class="p" data-group-id="5585156685-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5585156685-6">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:otp/ssh@5.3.3&quot;</span><span class="w"> </span><span class="p" data-group-id="5585156685-6">}</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="5585156685-3">]</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="s">&quot;products&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="9573354036-3">[</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9573354036-4">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0.4&quot;</span><span class="w"> </span><span class="p" data-group-id="9573354036-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9573354036-5">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0.3&quot;</span><span class="w"> </span><span class="p" data-group-id="9573354036-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9573354036-6">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:otp/ssh@5.3.3&quot;</span><span class="w"> </span><span class="p" data-group-id="9573354036-6">}</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="9573354036-3">]</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="s">&quot;status&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;fixed&quot;</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5585156685-1">}</span><span class="p">,</span></code></pre><h2 id="third-party-vex-statements" class="section-heading">
│ │ │ │ +</span><span class="p" data-group-id="9573354036-1">}</span><span class="p">,</span></code></pre><h2 id="third-party-vex-statements" class="section-heading">
│ │ │ │    <a href="#third-party-vex-statements" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Third Party VEX Statements</span>
│ │ │ │  </h2>
│ │ │ │  <p>Erlang/OTP generates statements for third parties from which the project depends
│ │ │ │  on. It is really important to understand the scope of the third party
│ │ │ │  applications, since Erlang/OTP vendors some libraries as part of the runtime.</p><p>Vendoring means that Erlang/OTP code contains a local copy of a library.
│ │ │ │  There are numerous use cases for why this is necessary, and we will not cover the use cases here.</p><p><strong>This excludes dynamically or statically linked libraries during the Erlang/OTP build process. For instance, any security related Erlang application will rely on dynamically or statically linked version of OpenSSL cryptolib.</strong></p><p>Erlang/OTP reports vulnerabilities for any source code that is vulnerable and
│ │ │ │  included in the Erlang/OTP release.</p><p>The OpenVEX statements for our third party libraries specify the affected/fixed
│ │ │ │  version using the commit SHA1 from their respective repository. This is simply
│ │ │ │  because our third party dependencies are in C/C++ and vulnerability scanners
│ │ │ │  such as OSV report vulnerabilities in SHA1 ranges.</p><p>As an example, we mention that the OpenSSL code that Erlang/OTP vendors
│ │ │ │ -is not susceptible for <code class="inline">CVE-2023-6129</code>, as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1274178527-1">{</span><span class="w">
│ │ │ │ -  </span><span class="s">&quot;vulnerability&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="1274178527-2">{</span><span class="w">
│ │ │ │ +is not susceptible for <code class="inline">CVE-2023-6129</code>, as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2768351754-1">{</span><span class="w">
│ │ │ │ +  </span><span class="s">&quot;vulnerability&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="2768351754-2">{</span><span class="w">
│ │ │ │      </span><span class="s">&quot;name&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;CVE-2023-6129&quot;</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="1274178527-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="2768351754-2">}</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="s">&quot;timestamp&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;2025-06-18T12:18:16.47247833+02:00&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="s">&quot;products&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="1274178527-3">[</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="1274178527-4">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/openssl/openssl@01d5e2318405362b4de5e670c90d9b40a351d053&quot;</span><span class="w"> </span><span class="p" data-group-id="1274178527-4">}</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="1274178527-3">]</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="s">&quot;products&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="2768351754-3">[</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="2768351754-4">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/openssl/openssl@01d5e2318405362b4de5e670c90d9b40a351d053&quot;</span><span class="w"> </span><span class="p" data-group-id="2768351754-4">}</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="2768351754-3">]</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="s">&quot;status&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;not_affected&quot;</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="s">&quot;justification&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;vulnerable_code_not_present&quot;</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1274178527-1">}</span></code></pre><p>Diving into the example, this means that Erlang/OTP vendors a version of <code class="inline">openssl</code> taken from commit <code class="inline">01d5e2318405362b4de5e670c90d9b40a351d053</code> from the repository <code class="inline">https://github.com/openssl/openssl/commit/01d5e2318405362b4de5e670c90d9b40a351d053</code> (version of OpenSSL 3.1.4). The <code class="inline">openssl</code> code that Erlang/OTP vendors can be found in <code class="inline">./lib/erl_interface/src/openssl/</code> and <code class="inline">./erts/emulator/openssl/</code>. The OpenVEX statement claims that the code in those folders is not susceptible to <code class="inline">CVE-2023-6129</code>. The claim is towards <strong>source code existing in Erlang/OTP</strong>.</p><p>In other words, the <code class="inline">not_affected</code> status refers to the library that Erlang/OTP vendors for OpenSSL (the library that comes
│ │ │ │ +</span><span class="p" data-group-id="2768351754-1">}</span></code></pre><p>Diving into the example, this means that Erlang/OTP vendors a version of <code class="inline">openssl</code> taken from commit <code class="inline">01d5e2318405362b4de5e670c90d9b40a351d053</code> from the repository <code class="inline">https://github.com/openssl/openssl/commit/01d5e2318405362b4de5e670c90d9b40a351d053</code> (version of OpenSSL 3.1.4). The <code class="inline">openssl</code> code that Erlang/OTP vendors can be found in <code class="inline">./lib/erl_interface/src/openssl/</code> and <code class="inline">./erts/emulator/openssl/</code>. The OpenVEX statement claims that the code in those folders is not susceptible to <code class="inline">CVE-2023-6129</code>. The claim is towards <strong>source code existing in Erlang/OTP</strong>.</p><p>In other words, the <code class="inline">not_affected</code> status refers to the library that Erlang/OTP vendors for OpenSSL (the library that comes
│ │ │ │  included with Erlang/OTP). If you build Erlang/OTP and link to any OpenSSL version (e.g., 3.5.2 or even 3.1.4) during the building process,
│ │ │ │  your project has now a new build and runtime dependency and may be subject to <code class="inline">CVE-2023-6129</code>.</p><h2 id="windows-binaries" class="section-heading">
│ │ │ │    <a href="#windows-binaries" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Windows Binaries</span>
│ │ │ │  </h2>
│ │ │ ├── OEBPS/typespec.xhtml
│ │ │ │ @@ -143,126 +143,126 @@
│ │ │ │  and optional <code class="inline">(=&gt;)</code> association types. If an association type is mandatory, an
│ │ │ │  association with that type needs to be present. In the case of an optional
│ │ │ │  association type it is not required for the key type to be present.</p><p>The notation <code class="inline">#{}</code> specifies the singleton type for the empty map. Note that
│ │ │ │  this notation is not a shorthand for the <a href="../../../lib/../erts/doc/html/erlang.html#t:map/0"><code class="inline">map/0</code></a> type.</p><p>For convenience, the following types are also built-in. They can be thought of as
│ │ │ │  predefined aliases for the type unions also shown in the table.</p><p><a href="" id="builtin_types"></a></p><table><thead><tr><th style="text-align: left;">Built-in type</th><th style="text-align: left;">Defined as</th></tr></thead><tbody><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:term/0"><code class="inline">term/0</code></a></td><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:any/0"><code class="inline">any/0</code></a></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:binary/0"><code class="inline">binary/0</code></a></td><td style="text-align: left;"><code class="inline">&lt;&lt;_:_*8&gt;&gt;</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:nonempty_binary/0"><code class="inline">nonempty_binary/0</code></a></td><td style="text-align: left;"><code class="inline">&lt;&lt;_:8, _:_*8&gt;&gt;</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:bitstring/0"><code class="inline">bitstring/0</code></a></td><td style="text-align: left;"><code class="inline">&lt;&lt;_:_*1&gt;&gt;</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:nonempty_bitstring/0"><code class="inline">nonempty_bitstring/0</code></a></td><td style="text-align: left;"><code class="inline">&lt;&lt;_:1, _:_*1&gt;&gt;</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:boolean/0"><code class="inline">boolean/0</code></a></td><td style="text-align: left;"><code class="inline">'false'</code> | <code class="inline">'true'</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:byte/0"><code class="inline">byte/0</code></a></td><td style="text-align: left;"><code class="inline">0..255</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:char/0"><code class="inline">char/0</code></a></td><td style="text-align: left;"><code class="inline">0..16#10ffff</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:nil/0"><code class="inline">nil/0</code></a></td><td style="text-align: left;"><code class="inline">[]</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:number/0"><code class="inline">number/0</code></a></td><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:integer/0"><code class="inline">integer/0</code></a> | <a href="../../../lib/../erts/doc/html/erlang.html#t:float/0"><code class="inline">float/0</code></a></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:list/0"><code class="inline">list/0</code></a></td><td style="text-align: left;"><code class="inline">[any()]</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:maybe_improper_list/0"><code class="inline">maybe_improper_list/0</code></a></td><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:maybe_improper_list/2"><code class="inline">maybe_improper_list(any(), any())</code></a></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:nonempty_list/0"><code class="inline">nonempty_list/0</code></a></td><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:nonempty_list/1"><code class="inline">nonempty_list(any())</code></a></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:string/0"><code class="inline">string/0</code></a></td><td style="text-align: left;"><code class="inline">[char()]</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:nonempty_string/0"><code class="inline">nonempty_string/0</code></a></td><td style="text-align: left;"><code class="inline">[char(), ...]</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:iodata/0"><code class="inline">iodata/0</code></a></td><td style="text-align: left;"><code class="inline">iolist()</code> | <code class="inline">binary()</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:iolist/0"><code class="inline">iolist/0</code></a></td><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:maybe_improper_list/2"><code class="inline">maybe_improper_list(byte() | binary() | iolist(), binary() | [])</code></a></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:map/0"><code class="inline">map/0</code></a></td><td style="text-align: left;"><code class="inline">#{any() =&gt; any()}</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:function/0"><code class="inline">function/0</code></a></td><td style="text-align: left;"><code class="inline">fun()</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:module/0"><code class="inline">module/0</code></a></td><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:atom/0"><code class="inline">atom/0</code></a></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:mfa/0"><code class="inline">mfa/0</code></a></td><td style="text-align: left;"><code class="inline">{module(),atom(),arity()}</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:arity/0"><code class="inline">arity/0</code></a></td><td style="text-align: left;"><code class="inline">0..255</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:identifier/0"><code class="inline">identifier/0</code></a></td><td style="text-align: left;"><code class="inline">pid()</code> | <code class="inline">port()</code> | <code class="inline">reference()</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#node/0"><code class="inline">node/0</code></a></td><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:atom/0"><code class="inline">atom/0</code></a></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:timeout/0"><code class="inline">timeout/0</code></a></td><td style="text-align: left;"><code class="inline">'infinity'</code> | <code class="inline">non_neg_integer()</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:no_return/0"><code class="inline">no_return/0</code></a></td><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:none/0"><code class="inline">none/0</code></a></td></tr></tbody></table><p><em>Table: Built-in types, predefined aliases</em></p><p>In addition, the following three built-in types exist and can be thought of as
│ │ │ │  defined below, though strictly their &quot;type definition&quot; is not valid syntax
│ │ │ │  according to the type language defined above.</p><table><thead><tr><th style="text-align: left;">Built-in type</th><th style="text-align: left;">Can be thought of as defined by the syntax</th></tr></thead><tbody><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:non_neg_integer/0"><code class="inline">non_neg_integer/0</code></a></td><td style="text-align: left;"><code class="inline">0..</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:pos_integer/0"><code class="inline">pos_integer/0</code></a></td><td style="text-align: left;"><code class="inline">1..</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:neg_integer/0"><code class="inline">neg_integer/0</code></a></td><td style="text-align: left;"><code class="inline">..-1</code></td></tr></tbody></table><p><em>Table: Additional built-in types</em></p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The following built-in list types also exist, but they are expected to be
│ │ │ │ -rarely used. Hence, they have long names:</p></section><pre><code class="makeup erlang" translate="no"><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="2878895054-1">(</span><span class="p" data-group-id="2878895054-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="2878895054-2">(</span><span class="nf">any</span><span class="p" data-group-id="2878895054-3">(</span><span class="p" data-group-id="2878895054-3">)</span><span class="p">,</span><span class="w"> </span><span class="nf">any</span><span class="p" data-group-id="2878895054-4">(</span><span class="p" data-group-id="2878895054-4">)</span><span class="p" data-group-id="2878895054-2">)</span><span class="w">
│ │ │ │ -</span><span class="nf">nonempty_improper_list</span><span class="p" data-group-id="2878895054-5">(</span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="n">Type2</span><span class="p" data-group-id="2878895054-5">)</span><span class="w">
│ │ │ │ -</span><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="2878895054-6">(</span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="n">Type2</span><span class="p" data-group-id="2878895054-6">)</span></code></pre><p>where the last two types define the set of Erlang terms one would expect.</p><p>Also for convenience, record notation is allowed to be used. Records are
│ │ │ │ -shorthands for the corresponding tuples:</p><pre><code class="makeup erlang" translate="no"><span class="n">Record</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p">#</span><span class="n">Erlang_Atom</span><span class="p" data-group-id="7987587403-1">{</span><span class="p" data-group-id="7987587403-1">}</span><span class="w">
│ │ │ │ -        </span><span class="p">|</span><span class="w"> </span><span class="p">#</span><span class="n">Erlang_Atom</span><span class="p" data-group-id="7987587403-2">{</span><span class="n">Fields</span><span class="p" data-group-id="7987587403-2">}</span></code></pre><p>Records are extended to possibly contain type information. This is described in
│ │ │ │ +rarely used. Hence, they have long names:</p></section><pre><code class="makeup erlang" translate="no"><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="7792739802-1">(</span><span class="p" data-group-id="7792739802-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="7792739802-2">(</span><span class="nf">any</span><span class="p" data-group-id="7792739802-3">(</span><span class="p" data-group-id="7792739802-3">)</span><span class="p">,</span><span class="w"> </span><span class="nf">any</span><span class="p" data-group-id="7792739802-4">(</span><span class="p" data-group-id="7792739802-4">)</span><span class="p" data-group-id="7792739802-2">)</span><span class="w">
│ │ │ │ +</span><span class="nf">nonempty_improper_list</span><span class="p" data-group-id="7792739802-5">(</span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="n">Type2</span><span class="p" data-group-id="7792739802-5">)</span><span class="w">
│ │ │ │ +</span><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="7792739802-6">(</span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="n">Type2</span><span class="p" data-group-id="7792739802-6">)</span></code></pre><p>where the last two types define the set of Erlang terms one would expect.</p><p>Also for convenience, record notation is allowed to be used. Records are
│ │ │ │ +shorthands for the corresponding tuples:</p><pre><code class="makeup erlang" translate="no"><span class="n">Record</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p">#</span><span class="n">Erlang_Atom</span><span class="p" data-group-id="1710210864-1">{</span><span class="p" data-group-id="1710210864-1">}</span><span class="w">
│ │ │ │ +        </span><span class="p">|</span><span class="w"> </span><span class="p">#</span><span class="n">Erlang_Atom</span><span class="p" data-group-id="1710210864-2">{</span><span class="n">Fields</span><span class="p" data-group-id="1710210864-2">}</span></code></pre><p>Records are extended to possibly contain type information. This is described in
│ │ │ │  <a href="typespec.xhtml#typeinrecords">Type Information in Record Declarations</a>.</p><h3 id="redefining-built-in-types" class="section-heading">
│ │ │ │    <a href="#redefining-built-in-types" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Redefining built-in types</span>
│ │ │ │  </h3>
│ │ │ │  <section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Starting from Erlang/OTP 26, it is permitted to define a type having the same
│ │ │ │  name as a built-in type.</p></section><p>It is recommended to avoid deliberately reusing built-in names because it can be
│ │ │ │  confusing. However, when an Erlang/OTP release introduces a new type, code that
│ │ │ │  happened to define its own type having the same name will continue to work.</p><p>As an example, imagine that the Erlang/OTP 42 release introduces a new type
│ │ │ │ -<code class="inline">gadget()</code> defined like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">gadget</span><span class="p" data-group-id="9537214504-1">(</span><span class="p" data-group-id="9537214504-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="9537214504-2">{</span><span class="ss">&#39;gadget&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">reference</span><span class="p" data-group-id="9537214504-3">(</span><span class="p" data-group-id="9537214504-3">)</span><span class="p" data-group-id="9537214504-2">}</span><span class="p">.</span></code></pre><p>Further imagine that some code has its own (different) definition of <code class="inline">gadget()</code>,
│ │ │ │ -for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">gadget</span><span class="p" data-group-id="1331952484-1">(</span><span class="p" data-group-id="1331952484-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="1331952484-2">#{</span><span class="p" data-group-id="1331952484-2">}</span><span class="p">.</span></code></pre><p>Since redefinitions are allowed, the code will still compile (but with a
│ │ │ │ +<code class="inline">gadget()</code> defined like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">gadget</span><span class="p" data-group-id="2631776943-1">(</span><span class="p" data-group-id="2631776943-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="2631776943-2">{</span><span class="ss">&#39;gadget&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">reference</span><span class="p" data-group-id="2631776943-3">(</span><span class="p" data-group-id="2631776943-3">)</span><span class="p" data-group-id="2631776943-2">}</span><span class="p">.</span></code></pre><p>Further imagine that some code has its own (different) definition of <code class="inline">gadget()</code>,
│ │ │ │ +for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">gadget</span><span class="p" data-group-id="8202339974-1">(</span><span class="p" data-group-id="8202339974-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="8202339974-2">#{</span><span class="p" data-group-id="8202339974-2">}</span><span class="p">.</span></code></pre><p>Since redefinitions are allowed, the code will still compile (but with a
│ │ │ │  warning), and Dialyzer will not emit any additional warnings.</p><h2 id="type-declarations-of-user-defined-types" class="section-heading">
│ │ │ │    <a href="#type-declarations-of-user-defined-types" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Type Declarations of User-Defined Types</span>
│ │ │ │  </h2>
│ │ │ │  <p>As seen, the basic syntax of a type is an atom followed by closed parentheses.
│ │ │ │  New types are declared using <code class="inline">-type</code>, <a href="opaques.xhtml"><code class="inline">-opaque</code></a>, and
│ │ │ │ -<a href="nominals.xhtml"><code class="inline">-nominal</code></a> attributes as in the following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">my_struct_type</span><span class="p" data-group-id="6494329170-1">(</span><span class="p" data-group-id="6494329170-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">my_opaq_type</span><span class="p" data-group-id="6494329170-2">(</span><span class="p" data-group-id="6494329170-2">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">my_nominal_type</span><span class="p" data-group-id="6494329170-3">(</span><span class="p" data-group-id="6494329170-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span></code></pre><p>The type name is the atom <code class="inline">my_struct_type</code>, followed by parentheses. <code class="inline">Type</code> is a
│ │ │ │ +<a href="nominals.xhtml"><code class="inline">-nominal</code></a> attributes as in the following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">my_struct_type</span><span class="p" data-group-id="3195344767-1">(</span><span class="p" data-group-id="3195344767-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">my_opaq_type</span><span class="p" data-group-id="3195344767-2">(</span><span class="p" data-group-id="3195344767-2">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">my_nominal_type</span><span class="p" data-group-id="3195344767-3">(</span><span class="p" data-group-id="3195344767-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span></code></pre><p>The type name is the atom <code class="inline">my_struct_type</code>, followed by parentheses. <code class="inline">Type</code> is a
│ │ │ │  type as defined in the previous section. A current restriction is that <code class="inline">Type</code>
│ │ │ │  can contain only predefined types, or user-defined types which are either of the
│ │ │ │  following:</p><ul><li>Module-local type, that is, with a definition that is present in the code of
│ │ │ │  the module</li><li>Remote type, that is, type defined in, and exported by, other modules; more
│ │ │ │  about this soon.</li></ul><p>For module-local types, the restriction that their definition exists in the
│ │ │ │  module is enforced by the compiler and results in a compilation error. (A
│ │ │ │  similar restriction currently exists for records.)</p><p>Type declarations can also be parameterized by including type variables between
│ │ │ │  the parentheses. The syntax of type variables is the same as Erlang variables,
│ │ │ │  that is, they start with an uppercase letter. These variables are to
│ │ │ │ -appear on the RHS of the definition. A concrete example follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">orddict</span><span class="p" data-group-id="6695856884-1">(</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Val</span><span class="p" data-group-id="6695856884-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="6695856884-2">[</span><span class="p" data-group-id="6695856884-3">{</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Val</span><span class="p" data-group-id="6695856884-3">}</span><span class="p" data-group-id="6695856884-2">]</span><span class="p">.</span></code></pre><p>A module can export some types to declare that other modules are allowed to
│ │ │ │ -refer to them as <em>remote types</em>. This declaration has the following form:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export_type</span><span class="p" data-group-id="6983115540-1">(</span><span class="p" data-group-id="6983115540-2">[</span><span class="n">T1</span><span class="o">/</span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Tk</span><span class="o">/</span><span class="n">Ak</span><span class="p" data-group-id="6983115540-2">]</span><span class="p" data-group-id="6983115540-1">)</span><span class="p">.</span></code></pre><p>Here the <code class="inline">Ti</code>s are atoms (the name of the type) and the <code class="inline">Ai</code>s are their arities.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export_type</span><span class="p" data-group-id="2324588276-1">(</span><span class="p" data-group-id="2324588276-2">[</span><span class="ss">my_struct_type</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">orddict</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2324588276-2">]</span><span class="p" data-group-id="2324588276-1">)</span><span class="p">.</span></code></pre><p>Assuming that these types are exported from module <code class="inline">'mod'</code>, you can refer to
│ │ │ │ -them from other modules using remote type expressions like the following:</p><pre><code class="makeup erlang" translate="no"><span class="nc">mod</span><span class="p">:</span><span class="nf">my_struct_type</span><span class="p" data-group-id="4251181337-1">(</span><span class="p" data-group-id="4251181337-1">)</span><span class="w">
│ │ │ │ -</span><span class="nc">mod</span><span class="p">:</span><span class="nf">orddict</span><span class="p" data-group-id="4251181337-2">(</span><span class="nf">atom</span><span class="p" data-group-id="4251181337-3">(</span><span class="p" data-group-id="4251181337-3">)</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="4251181337-4">(</span><span class="p" data-group-id="4251181337-4">)</span><span class="p" data-group-id="4251181337-2">)</span></code></pre><p>It is not allowed to refer to types that are not declared as exported.</p><p>Types declared as <code class="inline">opaque</code> represent sets of terms whose structure is not
│ │ │ │ +appear on the RHS of the definition. A concrete example follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">orddict</span><span class="p" data-group-id="8817494317-1">(</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Val</span><span class="p" data-group-id="8817494317-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="8817494317-2">[</span><span class="p" data-group-id="8817494317-3">{</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Val</span><span class="p" data-group-id="8817494317-3">}</span><span class="p" data-group-id="8817494317-2">]</span><span class="p">.</span></code></pre><p>A module can export some types to declare that other modules are allowed to
│ │ │ │ +refer to them as <em>remote types</em>. This declaration has the following form:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export_type</span><span class="p" data-group-id="0723010166-1">(</span><span class="p" data-group-id="0723010166-2">[</span><span class="n">T1</span><span class="o">/</span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Tk</span><span class="o">/</span><span class="n">Ak</span><span class="p" data-group-id="0723010166-2">]</span><span class="p" data-group-id="0723010166-1">)</span><span class="p">.</span></code></pre><p>Here the <code class="inline">Ti</code>s are atoms (the name of the type) and the <code class="inline">Ai</code>s are their arities.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export_type</span><span class="p" data-group-id="0085506546-1">(</span><span class="p" data-group-id="0085506546-2">[</span><span class="ss">my_struct_type</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">orddict</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0085506546-2">]</span><span class="p" data-group-id="0085506546-1">)</span><span class="p">.</span></code></pre><p>Assuming that these types are exported from module <code class="inline">'mod'</code>, you can refer to
│ │ │ │ +them from other modules using remote type expressions like the following:</p><pre><code class="makeup erlang" translate="no"><span class="nc">mod</span><span class="p">:</span><span class="nf">my_struct_type</span><span class="p" data-group-id="4483558382-1">(</span><span class="p" data-group-id="4483558382-1">)</span><span class="w">
│ │ │ │ +</span><span class="nc">mod</span><span class="p">:</span><span class="nf">orddict</span><span class="p" data-group-id="4483558382-2">(</span><span class="nf">atom</span><span class="p" data-group-id="4483558382-3">(</span><span class="p" data-group-id="4483558382-3">)</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="4483558382-4">(</span><span class="p" data-group-id="4483558382-4">)</span><span class="p" data-group-id="4483558382-2">)</span></code></pre><p>It is not allowed to refer to types that are not declared as exported.</p><p>Types declared as <code class="inline">opaque</code> represent sets of terms whose structure is not
│ │ │ │  supposed to be visible from outside of their defining module. That is, only the
│ │ │ │  module defining them is allowed to depend on their term structure. Consequently,
│ │ │ │  such types do not make much sense as module local - module local types are not
│ │ │ │  accessible by other modules anyway - and are always to be exported.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Nominal types were introduced in Erlang/OTP 28.</p></section><p>Types declared as <code class="inline">nominal</code> are type-checked according to the user-defined
│ │ │ │  names instead of their structure. That is, <code class="inline">-nominal feet() :: integer()</code> and
│ │ │ │  <code class="inline">-nominal meter() :: integer()</code> are not the same type, while if <code class="inline">-type</code> is
│ │ │ │  used it would be.</p><p>Read more on <a href="opaques.xhtml">Opaques</a> and <a href="nominals.xhtml">Nominals</a>.</p><p><a href="" id="typeinrecords"></a></p><h2 id="type-information-in-record-declarations" class="section-heading">
│ │ │ │    <a href="#type-information-in-record-declarations" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Type Information in Record Declarations</span>
│ │ │ │  </h2>
│ │ │ │  <p>The types of record fields can be specified in the declaration of the record.
│ │ │ │ -The syntax for this is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9656804248-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9656804248-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="9656804248-2">}</span><span class="p" data-group-id="9656804248-1">)</span><span class="p">.</span></code></pre><p>For fields without type annotations, their type defaults to <code class="inline">any()</code>. That is, the
│ │ │ │ -previous example is a shorthand for the following:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2943824100-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2943824100-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">any</span><span class="p" data-group-id="2943824100-3">(</span><span class="p" data-group-id="2943824100-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="2943824100-2">}</span><span class="p" data-group-id="2943824100-1">)</span><span class="p">.</span></code></pre><p>In the presence of initial values for fields, the type must be declared after
│ │ │ │ -the initialization, as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5940723817-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5940723817-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5940723817-3">[</span><span class="p" data-group-id="5940723817-3">]</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="5940723817-2">}</span><span class="p" data-group-id="5940723817-1">)</span><span class="p">.</span></code></pre><p>The initial values for fields are to be compatible with (that is, a member of)
│ │ │ │ +The syntax for this is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0626001820-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0626001820-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="0626001820-2">}</span><span class="p" data-group-id="0626001820-1">)</span><span class="p">.</span></code></pre><p>For fields without type annotations, their type defaults to <code class="inline">any()</code>. That is, the
│ │ │ │ +previous example is a shorthand for the following:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0878280309-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0878280309-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">any</span><span class="p" data-group-id="0878280309-3">(</span><span class="p" data-group-id="0878280309-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="0878280309-2">}</span><span class="p" data-group-id="0878280309-1">)</span><span class="p">.</span></code></pre><p>In the presence of initial values for fields, the type must be declared after
│ │ │ │ +the initialization, as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9842152481-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9842152481-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9842152481-3">[</span><span class="p" data-group-id="9842152481-3">]</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="9842152481-2">}</span><span class="p" data-group-id="9842152481-1">)</span><span class="p">.</span></code></pre><p>The initial values for fields are to be compatible with (that is, a member of)
│ │ │ │  the corresponding types. This is checked by the compiler and results in a
│ │ │ │  compilation error if a violation is detected.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 19, for fields without initial values, the singleton type
│ │ │ │  <code class="inline">'undefined'</code> was added to all declared types. In other words, the following
│ │ │ │ -two record declarations had identical effects:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1389445525-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1389445525-2">{</span><span class="ss">f1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="1389445525-3">(</span><span class="p" data-group-id="1389445525-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="ss">f2</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">float</span><span class="p" data-group-id="1389445525-4">(</span><span class="p" data-group-id="1389445525-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="ss">f3</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;a&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;b&#39;</span><span class="p" data-group-id="1389445525-2">}</span><span class="p" data-group-id="1389445525-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +two record declarations had identical effects:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7219079030-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7219079030-2">{</span><span class="ss">f1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="7219079030-3">(</span><span class="p" data-group-id="7219079030-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="ss">f2</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">float</span><span class="p" data-group-id="7219079030-4">(</span><span class="p" data-group-id="7219079030-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="ss">f3</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;a&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;b&#39;</span><span class="p" data-group-id="7219079030-2">}</span><span class="p" data-group-id="7219079030-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1389445525-5">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1389445525-6">{</span><span class="ss">f1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="1389445525-7">(</span><span class="p" data-group-id="1389445525-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="ss">f2</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;undefined&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">float</span><span class="p" data-group-id="1389445525-8">(</span><span class="p" data-group-id="1389445525-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="ss">f3</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;undefined&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;a&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;b&#39;</span><span class="p" data-group-id="1389445525-6">}</span><span class="p" data-group-id="1389445525-5">)</span><span class="p">.</span></code></pre><p>This is no longer the case. If you require <code class="inline">'undefined'</code> in your record field
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7219079030-5">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7219079030-6">{</span><span class="ss">f1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="7219079030-7">(</span><span class="p" data-group-id="7219079030-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="ss">f2</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;undefined&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">float</span><span class="p" data-group-id="7219079030-8">(</span><span class="p" data-group-id="7219079030-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="ss">f3</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;undefined&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;a&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;b&#39;</span><span class="p" data-group-id="7219079030-6">}</span><span class="p" data-group-id="7219079030-5">)</span><span class="p">.</span></code></pre><p>This is no longer the case. If you require <code class="inline">'undefined'</code> in your record field
│ │ │ │  type, you must explicitly add it to the typespec, as in the 2nd example.</p></section><p>Any record, containing type information or not, once defined, can be used as a
│ │ │ │  type using the following syntax:</p><pre><code class="text">#rec{}</code></pre><p>In addition, the record fields can be further specified when using a record type
│ │ │ │  by adding type information about the field as follows:</p><pre><code class="text">#rec{some_field :: Type}</code></pre><p>Any unspecified fields are assumed to have the type in the original record
│ │ │ │  declaration.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>When records are used to create patterns for ETS and Mnesia match functions,
│ │ │ │ -Dialyzer may need some help not to emit bad warnings. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="6046804372-1">(</span><span class="p" data-group-id="6046804372-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="6046804372-2">(</span><span class="p" data-group-id="6046804372-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6046804372-3">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6046804372-4">{</span><span class="ss">name</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="6046804372-5">(</span><span class="p" data-group-id="6046804372-5">)</span><span class="p">,</span><span class="w"> </span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="6046804372-6">(</span><span class="p" data-group-id="6046804372-6">)</span><span class="p" data-group-id="6046804372-4">}</span><span class="p" data-group-id="6046804372-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +Dialyzer may need some help not to emit bad warnings. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="2117445979-1">(</span><span class="p" data-group-id="2117445979-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="2117445979-2">(</span><span class="p" data-group-id="2117445979-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2117445979-3">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2117445979-4">{</span><span class="ss">name</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="2117445979-5">(</span><span class="p" data-group-id="2117445979-5">)</span><span class="p">,</span><span class="w"> </span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="2117445979-6">(</span><span class="p" data-group-id="2117445979-6">)</span><span class="p" data-group-id="2117445979-4">}</span><span class="p" data-group-id="2117445979-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">lookup</span><span class="p" data-group-id="6046804372-7">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Tab</span><span class="p" data-group-id="6046804372-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match_object</span><span class="p" data-group-id="6046804372-8">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6046804372-9">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="6046804372-9">}</span><span class="p" data-group-id="6046804372-8">)</span><span class="p">.</span></code></pre><p>Dialyzer will emit a warning since <code class="inline">'_'</code> is not in the type of record field
│ │ │ │ +</span><span class="nf">lookup</span><span class="p" data-group-id="2117445979-7">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Tab</span><span class="p" data-group-id="2117445979-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match_object</span><span class="p" data-group-id="2117445979-8">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2117445979-9">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="2117445979-9">}</span><span class="p" data-group-id="2117445979-8">)</span><span class="p">.</span></code></pre><p>Dialyzer will emit a warning since <code class="inline">'_'</code> is not in the type of record field
│ │ │ │  <code class="inline">height</code>.</p><p>The recommended way of dealing with this is to declare the smallest record
│ │ │ │  field types to accommodate all your needs, and then create refinements as
│ │ │ │ -needed. The modified example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1006692933-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1006692933-2">{</span><span class="ss">name</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="1006692933-3">(</span><span class="p" data-group-id="1006692933-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="1006692933-4">(</span><span class="p" data-group-id="1006692933-4">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="1006692933-2">}</span><span class="p" data-group-id="1006692933-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +needed. The modified example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2994455097-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2994455097-2">{</span><span class="ss">name</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="2994455097-3">(</span><span class="p" data-group-id="2994455097-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="2994455097-4">(</span><span class="p" data-group-id="2994455097-4">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="2994455097-2">}</span><span class="p" data-group-id="2994455097-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">person</span><span class="p" data-group-id="1006692933-5">(</span><span class="p" data-group-id="1006692933-5">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1006692933-6">{</span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="1006692933-7">(</span><span class="p" data-group-id="1006692933-7">)</span><span class="p" data-group-id="1006692933-6">}</span><span class="p">.</span></code></pre><p>In specifications and type declarations the type <code class="inline">person()</code> is to be preferred
│ │ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">person</span><span class="p" data-group-id="2994455097-5">(</span><span class="p" data-group-id="2994455097-5">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2994455097-6">{</span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="2994455097-7">(</span><span class="p" data-group-id="2994455097-7">)</span><span class="p" data-group-id="2994455097-6">}</span><span class="p">.</span></code></pre><p>In specifications and type declarations the type <code class="inline">person()</code> is to be preferred
│ │ │ │  over <code class="inline">#person{}</code>.</p></section><h2 id="specifications-for-functions" class="section-heading">
│ │ │ │    <a href="#specifications-for-functions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Specifications for Functions</span>
│ │ │ │  </h2>
│ │ │ │  <p>A specification (or contract) for a function is given using the <code class="inline">-spec</code>
│ │ │ │  attribute. The general format is as follows:</p><pre><code class="text">-spec Function(ArgType1, ..., ArgTypeN) -&gt; ReturnType.</code></pre><p>An implementation of the function with the same name <code class="inline">Function</code> must exist in
│ │ │ │  the current module, and the arity of the function must match the number of
│ │ │ │  arguments, otherwise the compilation fails.</p><p>The following longer format with module name is also valid as long as <code class="inline">Module</code>
│ │ │ │  is the name of the current module. This can be useful for documentation
│ │ │ │  purposes.</p><pre><code class="text">-spec Module:Function(ArgType1, ..., ArgTypeN) -&gt; ReturnType.</code></pre><p>Also, for documentation purposes, argument names can be given:</p><pre><code class="text">-spec Function(ArgName1 :: Type1, ..., ArgNameN :: TypeN) -&gt; RT.</code></pre><p>A function specification can be overloaded. That is, it can have several types,
│ │ │ │ -separated by a semicolon (<code class="inline">;</code>). For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="2123191450-1">(</span><span class="n">T1</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p" data-group-id="2123191450-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">T3</span><span class="p">;</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="2123191450-2">(</span><span class="n">T4</span><span class="p">,</span><span class="w"> </span><span class="n">T5</span><span class="p" data-group-id="2123191450-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">T6</span><span class="p">.</span></code></pre><p>A current restriction, which currently results in a warning by Dialyzer, is that
│ │ │ │ +separated by a semicolon (<code class="inline">;</code>). For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="6811300842-1">(</span><span class="n">T1</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p" data-group-id="6811300842-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">T3</span><span class="p">;</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="6811300842-2">(</span><span class="n">T4</span><span class="p">,</span><span class="w"> </span><span class="n">T5</span><span class="p" data-group-id="6811300842-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">T6</span><span class="p">.</span></code></pre><p>A current restriction, which currently results in a warning by Dialyzer, is that
│ │ │ │  the domains of the argument types cannot overlap. For example, the following
│ │ │ │ -specification results in a warning:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="0668878518-1">(</span><span class="nf">pos_integer</span><span class="p" data-group-id="0668878518-2">(</span><span class="p" data-group-id="0668878518-2">)</span><span class="p" data-group-id="0668878518-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="0668878518-3">(</span><span class="p" data-group-id="0668878518-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="0668878518-4">(</span><span class="nf">integer</span><span class="p" data-group-id="0668878518-5">(</span><span class="p" data-group-id="0668878518-5">)</span><span class="p" data-group-id="0668878518-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="0668878518-6">(</span><span class="p" data-group-id="0668878518-6">)</span><span class="p">.</span></code></pre><p>Type variables can be used in specifications to specify relations for the input
│ │ │ │ +specification results in a warning:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="0432261288-1">(</span><span class="nf">pos_integer</span><span class="p" data-group-id="0432261288-2">(</span><span class="p" data-group-id="0432261288-2">)</span><span class="p" data-group-id="0432261288-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="0432261288-3">(</span><span class="p" data-group-id="0432261288-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="0432261288-4">(</span><span class="nf">integer</span><span class="p" data-group-id="0432261288-5">(</span><span class="p" data-group-id="0432261288-5">)</span><span class="p" data-group-id="0432261288-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="0432261288-6">(</span><span class="p" data-group-id="0432261288-6">)</span><span class="p">.</span></code></pre><p>Type variables can be used in specifications to specify relations for the input
│ │ │ │  and output arguments of a function. For example, the following specification
│ │ │ │  defines the type of a polymorphic identity function:</p><pre><code class="text">-spec id(X) -&gt; X.</code></pre><p>Notice that the above specification does not restrict the input and output type
│ │ │ │  in any way. These types can be constrained by guard-like subtype constraints and
│ │ │ │ -provide bounded quantification:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">id</span><span class="p" data-group-id="1127733466-1">(</span><span class="n">X</span><span class="p" data-group-id="1127733466-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">tuple</span><span class="p" data-group-id="1127733466-2">(</span><span class="p" data-group-id="1127733466-2">)</span><span class="p">.</span></code></pre><p>Currently, the <code class="inline">::</code> constraint (read as &quot;is a subtype of&quot;) is the only guard
│ │ │ │ +provide bounded quantification:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">id</span><span class="p" data-group-id="4915745504-1">(</span><span class="n">X</span><span class="p" data-group-id="4915745504-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">tuple</span><span class="p" data-group-id="4915745504-2">(</span><span class="p" data-group-id="4915745504-2">)</span><span class="p">.</span></code></pre><p>Currently, the <code class="inline">::</code> constraint (read as &quot;is a subtype of&quot;) is the only guard
│ │ │ │  constraint that can be used in the <code class="inline">when</code> part of a <code class="inline">-spec</code> attribute.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The above function specification uses multiple occurrences of the same type
│ │ │ │  variable. That provides more type information than the following function
│ │ │ │ -specification, where the type variables are missing:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">id</span><span class="p" data-group-id="3002569546-1">(</span><span class="nf">tuple</span><span class="p" data-group-id="3002569546-2">(</span><span class="p" data-group-id="3002569546-2">)</span><span class="p" data-group-id="3002569546-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">tuple</span><span class="p" data-group-id="3002569546-3">(</span><span class="p" data-group-id="3002569546-3">)</span><span class="p">.</span></code></pre><p>The latter specification says that the function takes some tuple and returns
│ │ │ │ +specification, where the type variables are missing:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">id</span><span class="p" data-group-id="3816123370-1">(</span><span class="nf">tuple</span><span class="p" data-group-id="3816123370-2">(</span><span class="p" data-group-id="3816123370-2">)</span><span class="p" data-group-id="3816123370-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">tuple</span><span class="p" data-group-id="3816123370-3">(</span><span class="p" data-group-id="3816123370-3">)</span><span class="p">.</span></code></pre><p>The latter specification says that the function takes some tuple and returns
│ │ │ │  some tuple. The specification with the <code class="inline">X</code> type variable specifies that the
│ │ │ │  function takes a tuple and returns <em>the same</em> tuple.</p><p>However, it is up to the tools that process the specifications to choose
│ │ │ │  whether to take this extra information into account or not.</p></section><p>The scope of a <code class="inline">::</code> constraint is the <code class="inline">(...) -&gt; RetType</code> specification after
│ │ │ │  which it appears. To avoid confusion, it is suggested that different variables
│ │ │ │  are used in different constituents of an overloaded contract, as shown in the
│ │ │ │ -following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="3295332204-1">(</span><span class="p" data-group-id="3295332204-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3295332204-3">(</span><span class="p" data-group-id="3295332204-3">)</span><span class="p" data-group-id="3295332204-2">}</span><span class="p" data-group-id="3295332204-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="3295332204-4">(</span><span class="p" data-group-id="3295332204-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="3295332204-5">(</span><span class="p" data-group-id="3295332204-6">[</span><span class="n">Y</span><span class="p" data-group-id="3295332204-6">]</span><span class="p" data-group-id="3295332204-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="3295332204-7">(</span><span class="p" data-group-id="3295332204-7">)</span><span class="p">.</span></code></pre><p>Some functions in Erlang are not meant to return; either because they define
│ │ │ │ +following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="4642354348-1">(</span><span class="p" data-group-id="4642354348-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="4642354348-3">(</span><span class="p" data-group-id="4642354348-3">)</span><span class="p" data-group-id="4642354348-2">}</span><span class="p" data-group-id="4642354348-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="4642354348-4">(</span><span class="p" data-group-id="4642354348-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="4642354348-5">(</span><span class="p" data-group-id="4642354348-6">[</span><span class="n">Y</span><span class="p" data-group-id="4642354348-6">]</span><span class="p" data-group-id="4642354348-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="4642354348-7">(</span><span class="p" data-group-id="4642354348-7">)</span><span class="p">.</span></code></pre><p>Some functions in Erlang are not meant to return; either because they define
│ │ │ │  servers or because they are used to throw exceptions, as in the following
│ │ │ │ -function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">my_error</span><span class="p" data-group-id="0461079757-1">(</span><span class="n">Err</span><span class="p" data-group-id="0461079757-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="0461079757-2">(</span><span class="p" data-group-id="0461079757-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Err</span><span class="p" data-group-id="0461079757-3">}</span><span class="p" data-group-id="0461079757-2">)</span><span class="p">.</span></code></pre><p>For such functions, it is recommended to use the special <a href="../../../lib/../erts/doc/html/erlang.html#t:no_return/0"><code class="inline">no_return/0</code></a> type
│ │ │ │ +function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">my_error</span><span class="p" data-group-id="5377098062-1">(</span><span class="n">Err</span><span class="p" data-group-id="5377098062-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="5377098062-2">(</span><span class="p" data-group-id="5377098062-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Err</span><span class="p" data-group-id="5377098062-3">}</span><span class="p" data-group-id="5377098062-2">)</span><span class="p">.</span></code></pre><p>For such functions, it is recommended to use the special <a href="../../../lib/../erts/doc/html/erlang.html#t:no_return/0"><code class="inline">no_return/0</code></a> type
│ │ │ │  for their &quot;return&quot;, through a contract of the following form:</p><pre><code class="text">-spec my_error(term()) -&gt; no_return().</code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Erlang uses the shorthand version <code class="inline">_</code> as an anonymous type variable equivalent
│ │ │ │  to <a href="../../../lib/../erts/doc/html/erlang.html#t:term/0"><code class="inline">term/0</code></a> or <a href="../../../lib/../erts/doc/html/erlang.html#t:any/0"><code class="inline">any/0</code></a>. For example, the following function</p><pre><code class="text">-spec Function(string(), _) -&gt; string().</code></pre><p>is equivalent to:</p><pre><code class="text">-spec Function(string(), any()) -&gt; string().</code></pre></section>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/tablesdatabases.xhtml
│ │ │ │ @@ -51,73 +51,73 @@
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Deleting an Element</span>
│ │ │ │  </h3>
│ │ │ │  <p>The <code class="inline">delete</code> operation is considered successful if the element was not present
│ │ │ │  in the table. Hence all attempts to check that the element is present in the
│ │ │ │  Ets/Mnesia table before deletion are unnecessary. Here follows an example for
│ │ │ │ -Ets tables:</p><p><strong>DO</strong></p><pre><code class="text">ets:delete(Tab, Key),</code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="6009766293-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="6009766293-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6009766293-2">[</span><span class="p" data-group-id="6009766293-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +Ets tables:</p><p><strong>DO</strong></p><pre><code class="text">ets:delete(Tab, Key),</code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="2275623968-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="2275623968-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2275623968-2">[</span><span class="p" data-group-id="2275623968-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6009766293-3">[</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="6009766293-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nc">ets</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="6009766293-4">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="6009766293-4">)</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2275623968-3">[</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="2275623968-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nc">ets</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="2275623968-4">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="2275623968-4">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">,</span></code></pre><h3 id="fetching-data" class="section-heading">
│ │ │ │    <a href="#fetching-data" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Fetching Data</span>
│ │ │ │  </h3>
│ │ │ │  <p>Do not fetch data that you already have.</p><p>Consider that you have a module that handles the abstract data type <code class="inline">Person</code>.
│ │ │ │  You export the interface function <code class="inline">print_person/1</code>, which uses the internal
│ │ │ │  functions <code class="inline">print_name/1</code>, <code class="inline">print_age/1</code>, and <code class="inline">print_occupation/1</code>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>If the function <code class="inline">print_name/1</code>, and so on, had been interface functions, the
│ │ │ │  situation would have been different, as you do not want the user of the
│ │ │ │  interface to know about the internal data representation.</p></section><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="c1">%%% Interface function</span><span class="w">
│ │ │ │ -</span><span class="nf">print_person</span><span class="p" data-group-id="9241381979-1">(</span><span class="n">PersonId</span><span class="p" data-group-id="9241381979-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">print_person</span><span class="p" data-group-id="0943032223-1">(</span><span class="n">PersonId</span><span class="p" data-group-id="0943032223-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Look up the person in the named table person,</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="9241381979-2">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="9241381979-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="9241381979-3">[</span><span class="n">Person</span><span class="p" data-group-id="9241381979-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">print_name</span><span class="p" data-group-id="9241381979-4">(</span><span class="n">Person</span><span class="p" data-group-id="9241381979-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">print_age</span><span class="p" data-group-id="9241381979-5">(</span><span class="n">Person</span><span class="p" data-group-id="9241381979-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">print_occupation</span><span class="p" data-group-id="9241381979-6">(</span><span class="n">Person</span><span class="p" data-group-id="9241381979-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="9241381979-7">[</span><span class="p" data-group-id="9241381979-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9241381979-8">(</span><span class="s">&quot;No person with ID = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9241381979-9">[</span><span class="n">PersonId</span><span class="p" data-group-id="9241381979-9">]</span><span class="p" data-group-id="9241381979-8">)</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="0943032223-2">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="0943032223-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0943032223-3">[</span><span class="n">Person</span><span class="p" data-group-id="0943032223-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">print_name</span><span class="p" data-group-id="0943032223-4">(</span><span class="n">Person</span><span class="p" data-group-id="0943032223-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">print_age</span><span class="p" data-group-id="0943032223-5">(</span><span class="n">Person</span><span class="p" data-group-id="0943032223-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">print_occupation</span><span class="p" data-group-id="0943032223-6">(</span><span class="n">Person</span><span class="p" data-group-id="0943032223-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0943032223-7">[</span><span class="p" data-group-id="0943032223-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0943032223-8">(</span><span class="s">&quot;No person with ID = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0943032223-9">[</span><span class="n">PersonId</span><span class="p" data-group-id="0943032223-9">]</span><span class="p" data-group-id="0943032223-8">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Internal functions</span><span class="w">
│ │ │ │ -</span><span class="nf">print_name</span><span class="p" data-group-id="9241381979-10">(</span><span class="n">Person</span><span class="p" data-group-id="9241381979-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9241381979-11">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9241381979-12">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="9241381979-12">]</span><span class="p" data-group-id="9241381979-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">print_name</span><span class="p" data-group-id="0943032223-10">(</span><span class="n">Person</span><span class="p" data-group-id="0943032223-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0943032223-11">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0943032223-12">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="0943032223-12">]</span><span class="p" data-group-id="0943032223-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">print_age</span><span class="p" data-group-id="9241381979-13">(</span><span class="n">Person</span><span class="p" data-group-id="9241381979-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9241381979-14">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9241381979-15">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="9241381979-15">]</span><span class="p" data-group-id="9241381979-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">print_age</span><span class="p" data-group-id="0943032223-13">(</span><span class="n">Person</span><span class="p" data-group-id="0943032223-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0943032223-14">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0943032223-15">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="0943032223-15">]</span><span class="p" data-group-id="0943032223-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">print_occupation</span><span class="p" data-group-id="9241381979-16">(</span><span class="n">Person</span><span class="p" data-group-id="9241381979-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9241381979-17">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9241381979-18">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">occupation</span><span class="p" data-group-id="9241381979-18">]</span><span class="p" data-group-id="9241381979-17">)</span><span class="p">.</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="c1">%%% Interface function</span><span class="w">
│ │ │ │ -</span><span class="nf">print_person</span><span class="p" data-group-id="1697830797-1">(</span><span class="n">PersonId</span><span class="p" data-group-id="1697830797-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">print_occupation</span><span class="p" data-group-id="0943032223-16">(</span><span class="n">Person</span><span class="p" data-group-id="0943032223-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0943032223-17">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0943032223-18">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">occupation</span><span class="p" data-group-id="0943032223-18">]</span><span class="p" data-group-id="0943032223-17">)</span><span class="p">.</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="c1">%%% Interface function</span><span class="w">
│ │ │ │ +</span><span class="nf">print_person</span><span class="p" data-group-id="7918677580-1">(</span><span class="n">PersonId</span><span class="p" data-group-id="7918677580-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Look up the person in the named table person,</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1697830797-2">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="1697830797-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1697830797-3">[</span><span class="n">Person</span><span class="p" data-group-id="1697830797-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">print_name</span><span class="p" data-group-id="1697830797-4">(</span><span class="n">PersonId</span><span class="p" data-group-id="1697830797-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">print_age</span><span class="p" data-group-id="1697830797-5">(</span><span class="n">PersonId</span><span class="p" data-group-id="1697830797-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">print_occupation</span><span class="p" data-group-id="1697830797-6">(</span><span class="n">PersonId</span><span class="p" data-group-id="1697830797-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1697830797-7">[</span><span class="p" data-group-id="1697830797-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1697830797-8">(</span><span class="s">&quot;No person with ID = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1697830797-9">[</span><span class="n">PersonId</span><span class="p" data-group-id="1697830797-9">]</span><span class="p" data-group-id="1697830797-8">)</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="7918677580-2">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="7918677580-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="7918677580-3">[</span><span class="n">Person</span><span class="p" data-group-id="7918677580-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">print_name</span><span class="p" data-group-id="7918677580-4">(</span><span class="n">PersonId</span><span class="p" data-group-id="7918677580-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">print_age</span><span class="p" data-group-id="7918677580-5">(</span><span class="n">PersonId</span><span class="p" data-group-id="7918677580-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">print_occupation</span><span class="p" data-group-id="7918677580-6">(</span><span class="n">PersonId</span><span class="p" data-group-id="7918677580-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="7918677580-7">[</span><span class="p" data-group-id="7918677580-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7918677580-8">(</span><span class="s">&quot;No person with ID = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7918677580-9">[</span><span class="n">PersonId</span><span class="p" data-group-id="7918677580-9">]</span><span class="p" data-group-id="7918677580-8">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Internal functions</span><span class="w">
│ │ │ │ -</span><span class="nf">print_name</span><span class="p" data-group-id="1697830797-10">(</span><span class="n">PersonId</span><span class="p" data-group-id="1697830797-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1697830797-11">[</span><span class="n">Person</span><span class="p" data-group-id="1697830797-11">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1697830797-12">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="1697830797-12">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1697830797-13">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1697830797-14">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="1697830797-14">]</span><span class="p" data-group-id="1697830797-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">print_age</span><span class="p" data-group-id="1697830797-15">(</span><span class="n">PersonId</span><span class="p" data-group-id="1697830797-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1697830797-16">[</span><span class="n">Person</span><span class="p" data-group-id="1697830797-16">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1697830797-17">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="1697830797-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1697830797-18">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1697830797-19">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="1697830797-19">]</span><span class="p" data-group-id="1697830797-18">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">print_occupation</span><span class="p" data-group-id="1697830797-20">(</span><span class="n">PersonId</span><span class="p" data-group-id="1697830797-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1697830797-21">[</span><span class="n">Person</span><span class="p" data-group-id="1697830797-21">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1697830797-22">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="1697830797-22">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1697830797-23">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1697830797-24">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">occupation</span><span class="p" data-group-id="1697830797-24">]</span><span class="p" data-group-id="1697830797-23">)</span><span class="p">.</span></code></pre><h3 id="non-persistent-database-storage" class="section-heading">
│ │ │ │ +</span><span class="nf">print_name</span><span class="p" data-group-id="7918677580-10">(</span><span class="n">PersonId</span><span class="p" data-group-id="7918677580-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7918677580-11">[</span><span class="n">Person</span><span class="p" data-group-id="7918677580-11">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="7918677580-12">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="7918677580-12">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7918677580-13">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7918677580-14">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="7918677580-14">]</span><span class="p" data-group-id="7918677580-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">print_age</span><span class="p" data-group-id="7918677580-15">(</span><span class="n">PersonId</span><span class="p" data-group-id="7918677580-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7918677580-16">[</span><span class="n">Person</span><span class="p" data-group-id="7918677580-16">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="7918677580-17">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="7918677580-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7918677580-18">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7918677580-19">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="7918677580-19">]</span><span class="p" data-group-id="7918677580-18">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">print_occupation</span><span class="p" data-group-id="7918677580-20">(</span><span class="n">PersonId</span><span class="p" data-group-id="7918677580-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7918677580-21">[</span><span class="n">Person</span><span class="p" data-group-id="7918677580-21">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="7918677580-22">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="7918677580-22">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7918677580-23">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7918677580-24">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">occupation</span><span class="p" data-group-id="7918677580-24">]</span><span class="p" data-group-id="7918677580-23">)</span><span class="p">.</span></code></pre><h3 id="non-persistent-database-storage" class="section-heading">
│ │ │ │    <a href="#non-persistent-database-storage" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Non-Persistent Database Storage</span>
│ │ │ │  </h3>
│ │ │ │  <p>For non-persistent database storage, prefer Ets tables over Mnesia
│ │ │ │  <code class="inline">local_content</code> tables. Even the Mnesia <code class="inline">dirty_write</code> operations carry a fixed
│ │ │ │ @@ -131,38 +131,38 @@
│ │ │ │  </h3>
│ │ │ │  <p>Assuming an Ets table that uses <code class="inline">idno</code> as key and contains the following:</p><pre><code class="text">[#person{idno = 1, name = &quot;Adam&quot;,  age = 31, occupation = &quot;mailman&quot;},
│ │ │ │   #person{idno = 2, name = &quot;Bryan&quot;, age = 31, occupation = &quot;cashier&quot;},
│ │ │ │   #person{idno = 3, name = &quot;Bryan&quot;, age = 35, occupation = &quot;banker&quot;},
│ │ │ │   #person{idno = 4, name = &quot;Carl&quot;,  age = 25, occupation = &quot;mailman&quot;}]</code></pre><p>If you <em>must</em> return all data stored in the Ets table, you can use
│ │ │ │  <a href="../../../lib/stdlib/doc/html/ets.html#tab2list/1"><code class="inline">ets:tab2list/1</code></a>. However, usually you are only interested in a subset of the
│ │ │ │  information in which case <a href="../../../lib/stdlib/doc/html/ets.html#tab2list/1"><code class="inline">ets:tab2list/1</code></a> is expensive. If you only want to
│ │ │ │ -extract one field from each record, for example, the age of every person, then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="1262517059-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1262517059-2">[</span><span class="p" data-group-id="1262517059-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1262517059-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ │ +extract one field from each record, for example, the age of every person, then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="7783703726-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7783703726-2">[</span><span class="p" data-group-id="7783703726-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7783703726-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ │                            </span><span class="ss">name</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ │                            </span><span class="ss">age</span><span class="o">=</span><span class="ss">&#39;$1&#39;</span><span class="p">,</span><span class="w">
│ │ │ │ -                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="1262517059-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                </span><span class="p" data-group-id="1262517059-5">[</span><span class="p" data-group-id="1262517059-5">]</span><span class="p">,</span><span class="w">
│ │ │ │ -                </span><span class="p" data-group-id="1262517059-6">[</span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="1262517059-6">]</span><span class="p" data-group-id="1262517059-3">}</span><span class="p" data-group-id="1262517059-2">]</span><span class="p" data-group-id="1262517059-1">)</span><span class="p">,</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="3928601707-1">(</span><span class="n">Tab</span><span class="p" data-group-id="3928601707-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="3928601707-2">(</span><span class="nf">fun</span><span class="p" data-group-id="3928601707-3">(</span><span class="n">X</span><span class="p" data-group-id="3928601707-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="3928601707-2">)</span><span class="p">,</span></code></pre><p>If you are only interested in the age of all persons named &quot;Bryan&quot;, then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="7684794580-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7684794580-2">[</span><span class="p" data-group-id="7684794580-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7684794580-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ │ +                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="7783703726-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="p" data-group-id="7783703726-5">[</span><span class="p" data-group-id="7783703726-5">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="p" data-group-id="7783703726-6">[</span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="7783703726-6">]</span><span class="p" data-group-id="7783703726-3">}</span><span class="p" data-group-id="7783703726-2">]</span><span class="p" data-group-id="7783703726-1">)</span><span class="p">,</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="2516212326-1">(</span><span class="n">Tab</span><span class="p" data-group-id="2516212326-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="2516212326-2">(</span><span class="nf">fun</span><span class="p" data-group-id="2516212326-3">(</span><span class="n">X</span><span class="p" data-group-id="2516212326-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="2516212326-2">)</span><span class="p">,</span></code></pre><p>If you are only interested in the age of all persons named &quot;Bryan&quot;, then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="9499537104-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9499537104-2">[</span><span class="p" data-group-id="9499537104-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9499537104-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ │                            </span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Bryan&quot;</span><span class="p">,</span><span class="w">
│ │ │ │                            </span><span class="ss">age</span><span class="o">=</span><span class="ss">&#39;$1&#39;</span><span class="p">,</span><span class="w">
│ │ │ │ -                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="7684794580-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                </span><span class="p" data-group-id="7684794580-5">[</span><span class="p" data-group-id="7684794580-5">]</span><span class="p">,</span><span class="w">
│ │ │ │ -                </span><span class="p" data-group-id="7684794580-6">[</span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="7684794580-6">]</span><span class="p" data-group-id="7684794580-3">}</span><span class="p" data-group-id="7684794580-2">]</span><span class="p" data-group-id="7684794580-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="3643894778-1">(</span><span class="n">Tab</span><span class="p" data-group-id="3643894778-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="3643894778-2">(</span><span class="nf">fun</span><span class="p" data-group-id="3643894778-3">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3643894778-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="9499537104-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="p" data-group-id="9499537104-5">[</span><span class="p" data-group-id="9499537104-5">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="p" data-group-id="9499537104-6">[</span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="9499537104-6">]</span><span class="p" data-group-id="9499537104-3">}</span><span class="p" data-group-id="9499537104-2">]</span><span class="p" data-group-id="9499537104-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="8840502315-1">(</span><span class="n">Tab</span><span class="p" data-group-id="8840502315-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="8840502315-2">(</span><span class="nf">fun</span><span class="p" data-group-id="8840502315-3">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="8840502315-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │                                  </span><span class="s">&quot;Bryan&quot;</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                                    </span><span class="p" data-group-id="3643894778-4">[</span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="3643894778-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ +                                    </span><span class="p" data-group-id="8840502315-4">[</span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="8840502315-4">]</span><span class="p">;</span><span class="w">
│ │ │ │                                   </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                                       </span><span class="n">Acc</span><span class="w">
│ │ │ │                             </span><span class="k">end</span><span class="w">
│ │ │ │ -             </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3643894778-5">[</span><span class="p" data-group-id="3643894778-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="3643894778-2">)</span></code></pre><p>If you need all information stored in the Ets table about persons named &quot;Bryan&quot;,
│ │ │ │ -then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="9964276079-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9964276079-2">[</span><span class="p" data-group-id="9964276079-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9964276079-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8840502315-5">[</span><span class="p" data-group-id="8840502315-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="8840502315-2">)</span></code></pre><p>If you need all information stored in the Ets table about persons named &quot;Bryan&quot;,
│ │ │ │ +then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="4463216664-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4463216664-2">[</span><span class="p" data-group-id="4463216664-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="4463216664-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ │                            </span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Bryan&quot;</span><span class="p">,</span><span class="w">
│ │ │ │                            </span><span class="ss">age</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ │ -                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="9964276079-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9964276079-5">[</span><span class="p" data-group-id="9964276079-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9964276079-6">[</span><span class="ss">&#39;$_&#39;</span><span class="p" data-group-id="9964276079-6">]</span><span class="p" data-group-id="9964276079-3">}</span><span class="p" data-group-id="9964276079-2">]</span><span class="p" data-group-id="9964276079-1">)</span><span class="p">,</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="2172865212-1">(</span><span class="n">Tab</span><span class="p" data-group-id="2172865212-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="2172865212-2">(</span><span class="nf">fun</span><span class="p" data-group-id="2172865212-3">(</span><span class="n">X</span><span class="p" data-group-id="2172865212-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="s">&quot;Bryan&quot;</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="2172865212-2">)</span><span class="p">,</span></code></pre><h3 id="ordered_set-tables" class="section-heading">
│ │ │ │ +                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="4463216664-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4463216664-5">[</span><span class="p" data-group-id="4463216664-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4463216664-6">[</span><span class="ss">&#39;$_&#39;</span><span class="p" data-group-id="4463216664-6">]</span><span class="p" data-group-id="4463216664-3">}</span><span class="p" data-group-id="4463216664-2">]</span><span class="p" data-group-id="4463216664-1">)</span><span class="p">,</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="4646976533-1">(</span><span class="n">Tab</span><span class="p" data-group-id="4646976533-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="4646976533-2">(</span><span class="nf">fun</span><span class="p" data-group-id="4646976533-3">(</span><span class="n">X</span><span class="p" data-group-id="4646976533-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="s">&quot;Bryan&quot;</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="4646976533-2">)</span><span class="p">,</span></code></pre><h3 id="ordered_set-tables" class="section-heading">
│ │ │ │    <a href="#ordered_set-tables" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text"><code class="inline">ordered_set</code> Tables</span>
│ │ │ │  </h3>
│ │ │ │  <p>If the data in the table is to be accessed so that the order of the keys in the
│ │ │ │  table is significant, the table type <code class="inline">ordered_set</code> can be used instead of the
│ │ │ │ @@ -198,20 +198,20 @@
│ │ │ │  Clearly, the second table would have to be kept consistent with the master
│ │ │ │  table. Mnesia can do this for you, but a home-brew index table can be very
│ │ │ │  efficient compared to the overhead involved in using Mnesia.</p><p>An index table for the table in the previous examples would have to be a bag (as
│ │ │ │  keys would appear more than once) and can have the following contents:</p><pre><code class="text">[#index_entry{name=&quot;Adam&quot;, idno=1},
│ │ │ │   #index_entry{name=&quot;Bryan&quot;, idno=2},
│ │ │ │   #index_entry{name=&quot;Bryan&quot;, idno=3},
│ │ │ │   #index_entry{name=&quot;Carl&quot;, idno=4}]</code></pre><p>Given this index table, a lookup of the <code class="inline">age</code> fields for all persons named
│ │ │ │ -&quot;Bryan&quot; can be done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="n">MatchingIDs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="7584729556-1">(</span><span class="n">IndexTable</span><span class="p">,</span><span class="s">&quot;Bryan&quot;</span><span class="p" data-group-id="7584729556-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="7584729556-2">(</span><span class="nf">fun</span><span class="p" data-group-id="7584729556-3">(</span><span class="o">#</span><span class="ss">index_entry</span><span class="p" data-group-id="7584729556-4">{</span><span class="ss">idno</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ID</span><span class="p" data-group-id="7584729556-4">}</span><span class="p" data-group-id="7584729556-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                 </span><span class="p" data-group-id="7584729556-5">[</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7584729556-6">{</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="7584729556-6">}</span><span class="p" data-group-id="7584729556-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="7584729556-7">(</span><span class="n">PersonTable</span><span class="p">,</span><span class="w"> </span><span class="n">ID</span><span class="p" data-group-id="7584729556-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ +&quot;Bryan&quot; can be done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="n">MatchingIDs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="2492531725-1">(</span><span class="n">IndexTable</span><span class="p">,</span><span class="s">&quot;Bryan&quot;</span><span class="p" data-group-id="2492531725-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="2492531725-2">(</span><span class="nf">fun</span><span class="p" data-group-id="2492531725-3">(</span><span class="o">#</span><span class="ss">index_entry</span><span class="p" data-group-id="2492531725-4">{</span><span class="ss">idno</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ID</span><span class="p" data-group-id="2492531725-4">}</span><span class="p" data-group-id="2492531725-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                 </span><span class="p" data-group-id="2492531725-5">[</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2492531725-6">{</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="2492531725-6">}</span><span class="p" data-group-id="2492531725-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="2492531725-7">(</span><span class="n">PersonTable</span><span class="p">,</span><span class="w"> </span><span class="n">ID</span><span class="p" data-group-id="2492531725-7">)</span><span class="p">,</span><span class="w">
│ │ │ │                   </span><span class="n">Age</span><span class="w">
│ │ │ │            </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -          </span><span class="n">MatchingIDs</span><span class="p" data-group-id="7584729556-2">)</span><span class="p">,</span></code></pre><p>Notice that this code does not use <a href="../../../lib/stdlib/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a>, but instead uses the
│ │ │ │ +          </span><span class="n">MatchingIDs</span><span class="p" data-group-id="2492531725-2">)</span><span class="p">,</span></code></pre><p>Notice that this code does not use <a href="../../../lib/stdlib/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a>, but instead uses the
│ │ │ │  <a href="../../../lib/stdlib/doc/html/ets.html#lookup/2"><code class="inline">ets:lookup/2</code></a> call. The <a href="../../../lib/stdlib/doc/html/lists.html#map/2"><code class="inline">lists:map/2</code></a> call is only used to traverse the <code class="inline">idno</code>s
│ │ │ │  matching the name &quot;Bryan&quot; in the table; thus the number of lookups in the master
│ │ │ │  table is minimized.</p><p>Keeping an index table introduces some overhead when inserting records in the
│ │ │ │  table. The number of operations gained from the table must therefore be compared
│ │ │ │  against the number of operations inserting objects in the table. However, notice
│ │ │ │  that the gain is significant when the key can be used to lookup elements.</p><h2 id="mnesia" class="section-heading">
│ │ │ │    <a href="#mnesia" class="hover-link">
│ │ │ │ @@ -226,47 +226,47 @@
│ │ │ │    <span class="text">Secondary Index</span>
│ │ │ │  </h3>
│ │ │ │  <p>If you frequently do lookups on a field that is not the key of the table, you
│ │ │ │  lose performance using <a href="../../../lib/mnesia/doc/html/mnesia.html#select/3">mnesia:select()</a> or
│ │ │ │  <a href="../../../lib/mnesia/doc/html/mnesia.html#match_object/1"><code class="inline">mnesia:match_object()</code></a> as these functions traverse
│ │ │ │  the whole table. Instead, you can create a secondary index and use
│ │ │ │  <a href="../../../lib/mnesia/doc/html/mnesia.html#index_read/3"><code class="inline">mnesia:index_read/3</code></a> to get faster access at the expense of using more
│ │ │ │ -memory.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5171905808-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5171905808-2">{</span><span class="ss">idno</span><span class="p">,</span><span class="w"> </span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="ss">occupation</span><span class="p" data-group-id="5171905808-2">}</span><span class="p" data-group-id="5171905808-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +memory.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2269432458-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2269432458-2">{</span><span class="ss">idno</span><span class="p">,</span><span class="w"> </span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="ss">occupation</span><span class="p" data-group-id="2269432458-2">}</span><span class="p" data-group-id="2269432458-1">)</span><span class="p">.</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5171905808-3">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="5171905808-3">}</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │ -</span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">create_table</span><span class="p" data-group-id="5171905808-4">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5171905808-5">[</span><span class="p" data-group-id="5171905808-6">{</span><span class="ss">index</span><span class="p">,</span><span class="p" data-group-id="5171905808-7">[</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="5171905808-7">]</span><span class="p" data-group-id="5171905808-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                              </span><span class="p" data-group-id="5171905808-8">{</span><span class="ss">attributes</span><span class="p">,</span><span class="w">
│ │ │ │ -                                    </span><span class="nf">record_info</span><span class="p" data-group-id="5171905808-9">(</span><span class="ss">fields</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="5171905808-9">)</span><span class="p" data-group-id="5171905808-8">}</span><span class="p" data-group-id="5171905808-5">]</span><span class="p" data-group-id="5171905808-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5171905808-10">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="5171905808-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">add_table_index</span><span class="p" data-group-id="5171905808-11">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="5171905808-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2269432458-3">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="2269432458-3">}</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │ +</span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">create_table</span><span class="p" data-group-id="2269432458-4">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2269432458-5">[</span><span class="p" data-group-id="2269432458-6">{</span><span class="ss">index</span><span class="p">,</span><span class="p" data-group-id="2269432458-7">[</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="2269432458-7">]</span><span class="p" data-group-id="2269432458-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                              </span><span class="p" data-group-id="2269432458-8">{</span><span class="ss">attributes</span><span class="p">,</span><span class="w">
│ │ │ │ +                                    </span><span class="nf">record_info</span><span class="p" data-group-id="2269432458-9">(</span><span class="ss">fields</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="2269432458-9">)</span><span class="p" data-group-id="2269432458-8">}</span><span class="p" data-group-id="2269432458-5">]</span><span class="p" data-group-id="2269432458-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2269432458-10">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="2269432458-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">add_table_index</span><span class="p" data-group-id="2269432458-11">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="2269432458-11">)</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="n">PersonsAge42</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │ -     </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_index_read</span><span class="p" data-group-id="5171905808-12">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="5171905808-12">)</span><span class="p">,</span></code></pre><h3 id="transactions" class="section-heading">
│ │ │ │ +     </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_index_read</span><span class="p" data-group-id="2269432458-12">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="2269432458-12">)</span><span class="p">,</span></code></pre><h3 id="transactions" class="section-heading">
│ │ │ │    <a href="#transactions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Transactions</span>
│ │ │ │  </h3>
│ │ │ │  <p>Using transactions is a way to guarantee that the distributed Mnesia database
│ │ │ │  remains consistent, even when many different processes update it in parallel.
│ │ │ │  However, if you have real-time requirements it is recommended to use dirty
│ │ │ │  operations instead of transactions. When using dirty operations, you lose the
│ │ │ │  consistency guarantee; this is usually solved by only letting one process update
│ │ │ │  the table. Other processes must send update requests to that process.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% Using transaction</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3369964293-1">(</span><span class="p" data-group-id="3369964293-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -          </span><span class="p" data-group-id="3369964293-2">[</span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="3369964293-3">(</span><span class="p" data-group-id="3369964293-4">{</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="3369964293-4">}</span><span class="p" data-group-id="3369964293-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -           </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="3369964293-5">(</span><span class="p" data-group-id="3369964293-6">{</span><span class="n">Table2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="p" data-group-id="3369964293-6">}</span><span class="p" data-group-id="3369964293-5">)</span><span class="p" data-group-id="3369964293-2">]</span><span class="w">
│ │ │ │ +</span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="9201538227-1">(</span><span class="p" data-group-id="9201538227-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +          </span><span class="p" data-group-id="9201538227-2">[</span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="9201538227-3">(</span><span class="p" data-group-id="9201538227-4">{</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="9201538227-4">}</span><span class="p" data-group-id="9201538227-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +           </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="9201538227-5">(</span><span class="p" data-group-id="9201538227-6">{</span><span class="n">Table2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="p" data-group-id="9201538227-6">}</span><span class="p" data-group-id="9201538227-5">)</span><span class="p" data-group-id="9201538227-2">]</span><span class="w">
│ │ │ │        </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="p" data-group-id="3369964293-7">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3369964293-8">[</span><span class="n">Result1</span><span class="p">,</span><span class="w"> </span><span class="n">Result2</span><span class="p" data-group-id="3369964293-8">]</span><span class="p" data-group-id="3369964293-7">}</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">transaction</span><span class="p" data-group-id="3369964293-9">(</span><span class="n">Fun</span><span class="p" data-group-id="3369964293-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9201538227-7">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9201538227-8">[</span><span class="n">Result1</span><span class="p">,</span><span class="w"> </span><span class="n">Result2</span><span class="p" data-group-id="9201538227-8">]</span><span class="p" data-group-id="9201538227-7">}</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">transaction</span><span class="p" data-group-id="9201538227-9">(</span><span class="n">Fun</span><span class="p" data-group-id="9201538227-9">)</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% Same thing using dirty operations</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Result1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_read</span><span class="p" data-group-id="3369964293-10">(</span><span class="p" data-group-id="3369964293-11">{</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="3369964293-11">}</span><span class="p" data-group-id="3369964293-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Result2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_read</span><span class="p" data-group-id="3369964293-12">(</span><span class="p" data-group-id="3369964293-13">{</span><span class="n">Table2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="p" data-group-id="3369964293-13">}</span><span class="p" data-group-id="3369964293-12">)</span><span class="p">,</span></code></pre>
│ │ │ │ +</span><span class="n">Result1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_read</span><span class="p" data-group-id="9201538227-10">(</span><span class="p" data-group-id="9201538227-11">{</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="9201538227-11">}</span><span class="p" data-group-id="9201538227-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Result2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_read</span><span class="p" data-group-id="9201538227-12">(</span><span class="p" data-group-id="9201538227-13">{</span><span class="n">Table2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="p" data-group-id="9201538227-13">}</span><span class="p" data-group-id="9201538227-12">)</span><span class="p">,</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/sup_princ.xhtml
│ │ │ │ @@ -33,48 +33,48 @@
│ │ │ │  the order specified by this list, and are terminated in the reverse order.</p><h2 id="example" class="section-heading">
│ │ │ │    <a href="#example" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Example</span>
│ │ │ │  </h2>
│ │ │ │  <p>The callback module for a supervisor starting the server from
│ │ │ │ -<a href="gen_server_concepts.xhtml#ex">gen_server Behaviour</a> can look as follows:</p><p><a href="" id="ex"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9407935376-1">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="9407935376-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="9407935376-2">(</span><span class="ss">supervisor</span><span class="p" data-group-id="9407935376-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<a href="gen_server_concepts.xhtml#ex">gen_server Behaviour</a> can look as follows:</p><p><a href="" id="ex"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4478799905-1">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="4478799905-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="4478799905-2">(</span><span class="ss">supervisor</span><span class="p" data-group-id="4478799905-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9407935376-3">(</span><span class="p" data-group-id="9407935376-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9407935376-4">]</span><span class="p" data-group-id="9407935376-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9407935376-5">(</span><span class="p" data-group-id="9407935376-6">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9407935376-6">]</span><span class="p" data-group-id="9407935376-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4478799905-3">(</span><span class="p" data-group-id="4478799905-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4478799905-4">]</span><span class="p" data-group-id="4478799905-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4478799905-5">(</span><span class="p" data-group-id="4478799905-6">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4478799905-6">]</span><span class="p" data-group-id="4478799905-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="9407935376-7">(</span><span class="p" data-group-id="9407935376-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="9407935376-8">(</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9407935376-9">[</span><span class="p" data-group-id="9407935376-9">]</span><span class="p" data-group-id="9407935376-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="4478799905-7">(</span><span class="p" data-group-id="4478799905-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="4478799905-8">(</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4478799905-9">[</span><span class="p" data-group-id="4478799905-9">]</span><span class="p" data-group-id="4478799905-8">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="9407935376-10">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="9407935376-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9407935376-11">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">one_for_one</span><span class="p">,</span><span class="w"> </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="9407935376-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9407935376-12">[</span><span class="p" data-group-id="9407935376-13">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9407935376-14">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9407935376-15">[</span><span class="p" data-group-id="9407935376-15">]</span><span class="p" data-group-id="9407935376-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="4478799905-10">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="4478799905-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4478799905-11">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">one_for_one</span><span class="p">,</span><span class="w"> </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="4478799905-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4478799905-12">[</span><span class="p" data-group-id="4478799905-13">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4478799905-14">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4478799905-15">[</span><span class="p" data-group-id="4478799905-15">]</span><span class="p" data-group-id="4478799905-14">}</span><span class="p">,</span><span class="w">
│ │ │ │                      </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">permanent</span><span class="p">,</span><span class="w">
│ │ │ │                      </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p">,</span><span class="w">
│ │ │ │                      </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">worker</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9407935376-16">[</span><span class="ss">ch3</span><span class="p" data-group-id="9407935376-16">]</span><span class="p" data-group-id="9407935376-13">}</span><span class="p" data-group-id="9407935376-12">]</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9407935376-17">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9407935376-18">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="9407935376-18">}</span><span class="p" data-group-id="9407935376-17">}</span><span class="p">.</span></code></pre><p>The <code class="inline">SupFlags</code> variable in the return value from <code class="inline">init/1</code> represents the
│ │ │ │ +                    </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4478799905-16">[</span><span class="ss">ch3</span><span class="p" data-group-id="4478799905-16">]</span><span class="p" data-group-id="4478799905-13">}</span><span class="p" data-group-id="4478799905-12">]</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4478799905-17">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4478799905-18">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="4478799905-18">}</span><span class="p" data-group-id="4478799905-17">}</span><span class="p">.</span></code></pre><p>The <code class="inline">SupFlags</code> variable in the return value from <code class="inline">init/1</code> represents the
│ │ │ │  <a href="sup_princ.xhtml#flags">supervisor flags</a>.</p><p>The <code class="inline">ChildSpecs</code> variable in the return value from <code class="inline">init/1</code> is a list of
│ │ │ │  <a href="sup_princ.xhtml#spec">child specifications</a>.</p><p><a href="" id="flags"></a></p><h2 id="supervisor-flags" class="section-heading">
│ │ │ │    <a href="#supervisor-flags" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Supervisor Flags</span>
│ │ │ │  </h2>
│ │ │ │ -<p>This is the type definition for the supervisor flags:</p><pre><code class="makeup erlang" translate="no"><span class="nf">sup_flags</span><span class="p" data-group-id="7840710966-1">(</span><span class="p" data-group-id="7840710966-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7840710966-2">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">strategy</span><span class="p" data-group-id="7840710966-3">(</span><span class="p" data-group-id="7840710966-3">)</span><span class="p">,</span><span class="w">           </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -                </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="7840710966-4">(</span><span class="p" data-group-id="7840710966-4">)</span><span class="p">,</span><span class="w">   </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -                </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="7840710966-5">(</span><span class="p" data-group-id="7840710966-5">)</span><span class="p">,</span><span class="w">          </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -                </span><span class="ss">auto_shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">auto_shutdown</span><span class="p" data-group-id="7840710966-6">(</span><span class="p" data-group-id="7840710966-6">)</span><span class="p" data-group-id="7840710966-2">}</span><span class="w"> </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -    </span><span class="nf">strategy</span><span class="p" data-group-id="7840710966-7">(</span><span class="p" data-group-id="7840710966-7">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">one_for_all</span><span class="w">
│ │ │ │ +<p>This is the type definition for the supervisor flags:</p><pre><code class="makeup erlang" translate="no"><span class="nf">sup_flags</span><span class="p" data-group-id="6792109061-1">(</span><span class="p" data-group-id="6792109061-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6792109061-2">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">strategy</span><span class="p" data-group-id="6792109061-3">(</span><span class="p" data-group-id="6792109061-3">)</span><span class="p">,</span><span class="w">           </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +                </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="6792109061-4">(</span><span class="p" data-group-id="6792109061-4">)</span><span class="p">,</span><span class="w">   </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +                </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="6792109061-5">(</span><span class="p" data-group-id="6792109061-5">)</span><span class="p">,</span><span class="w">          </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +                </span><span class="ss">auto_shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">auto_shutdown</span><span class="p" data-group-id="6792109061-6">(</span><span class="p" data-group-id="6792109061-6">)</span><span class="p" data-group-id="6792109061-2">}</span><span class="w"> </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +    </span><span class="nf">strategy</span><span class="p" data-group-id="6792109061-7">(</span><span class="p" data-group-id="6792109061-7">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">one_for_all</span><span class="w">
│ │ │ │                 </span><span class="p">|</span><span class="w"> </span><span class="ss">one_for_one</span><span class="w">
│ │ │ │                 </span><span class="p">|</span><span class="w"> </span><span class="ss">rest_for_one</span><span class="w">
│ │ │ │                 </span><span class="p">|</span><span class="w"> </span><span class="ss">simple_one_for_one</span><span class="w">
│ │ │ │ -    </span><span class="nf">auto_shutdown</span><span class="p" data-group-id="7840710966-8">(</span><span class="p" data-group-id="7840710966-8">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">never</span><span class="w">
│ │ │ │ +    </span><span class="nf">auto_shutdown</span><span class="p" data-group-id="6792109061-8">(</span><span class="p" data-group-id="6792109061-8">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">never</span><span class="w">
│ │ │ │                      </span><span class="p">|</span><span class="w"> </span><span class="ss">any_significant</span><span class="w">
│ │ │ │                      </span><span class="p">|</span><span class="w"> </span><span class="ss">all_significant</span></code></pre><ul><li><code class="inline">strategy</code> specifies the <a href="sup_princ.xhtml#strategy">restart strategy</a>.</li><li><code class="inline">intensity</code> and <code class="inline">period</code> specify the
│ │ │ │  <a href="sup_princ.xhtml#max_intensity">maximum restart intensity</a>.</li><li><code class="inline">auto_shutdown</code> specifies whether and when a supervisor should
│ │ │ │  <a href="sup_princ.xhtml#automatic-shutdown">automatically shut itself down</a>.</li></ul><p><a href="" id="strategy"></a></p><h2 id="restart-strategy" class="section-heading">
│ │ │ │    <a href="#restart-strategy" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │ @@ -313,28 +313,28 @@
│ │ │ │  exhaust the <a href="sup_princ.xhtml#max_intensity">Maximum Restart Intensity</a> of the
│ │ │ │  parent supervisor.</p></section><p><a href="" id="spec"></a></p><h2 id="child-specification" class="section-heading">
│ │ │ │    <a href="#child-specification" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Child Specification</span>
│ │ │ │  </h2>
│ │ │ │ -<p>The type definition for a child specification is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">child_spec</span><span class="p" data-group-id="8713444829-1">(</span><span class="p" data-group-id="8713444829-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8713444829-2">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">child_id</span><span class="p" data-group-id="8713444829-3">(</span><span class="p" data-group-id="8713444829-3">)</span><span class="p">,</span><span class="w">             </span><span class="c1">% mandatory</span><span class="w">
│ │ │ │ -                 </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">mfargs</span><span class="p" data-group-id="8713444829-4">(</span><span class="p" data-group-id="8713444829-4">)</span><span class="p">,</span><span class="w">            </span><span class="c1">% mandatory</span><span class="w">
│ │ │ │ -                 </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">restart</span><span class="p" data-group-id="8713444829-5">(</span><span class="p" data-group-id="8713444829-5">)</span><span class="p">,</span><span class="w">         </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -                 </span><span class="ss">significant</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">significant</span><span class="p" data-group-id="8713444829-6">(</span><span class="p" data-group-id="8713444829-6">)</span><span class="p">,</span><span class="w"> </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -                 </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">shutdown</span><span class="p" data-group-id="8713444829-7">(</span><span class="p" data-group-id="8713444829-7">)</span><span class="p">,</span><span class="w">       </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -                 </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">worker</span><span class="p" data-group-id="8713444829-8">(</span><span class="p" data-group-id="8713444829-8">)</span><span class="p">,</span><span class="w">             </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -                 </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">modules</span><span class="p" data-group-id="8713444829-9">(</span><span class="p" data-group-id="8713444829-9">)</span><span class="p" data-group-id="8713444829-2">}</span><span class="w">         </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -    </span><span class="nf">child_id</span><span class="p" data-group-id="8713444829-10">(</span><span class="p" data-group-id="8713444829-10">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8713444829-11">(</span><span class="p" data-group-id="8713444829-11">)</span><span class="w">
│ │ │ │ -    </span><span class="nf">mfargs</span><span class="p" data-group-id="8713444829-12">(</span><span class="p" data-group-id="8713444829-12">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8713444829-13">{</span><span class="n">M</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">module</span><span class="p" data-group-id="8713444829-14">(</span><span class="p" data-group-id="8713444829-14">)</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="8713444829-15">(</span><span class="p" data-group-id="8713444829-15">)</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="8713444829-16">[</span><span class="nf">term</span><span class="p" data-group-id="8713444829-17">(</span><span class="p" data-group-id="8713444829-17">)</span><span class="p" data-group-id="8713444829-16">]</span><span class="p" data-group-id="8713444829-13">}</span><span class="w">
│ │ │ │ -    </span><span class="nf">modules</span><span class="p" data-group-id="8713444829-18">(</span><span class="p" data-group-id="8713444829-18">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8713444829-19">[</span><span class="nf">module</span><span class="p" data-group-id="8713444829-20">(</span><span class="p" data-group-id="8713444829-20">)</span><span class="p" data-group-id="8713444829-19">]</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">dynamic</span><span class="w">
│ │ │ │ -    </span><span class="nf">restart</span><span class="p" data-group-id="8713444829-21">(</span><span class="p" data-group-id="8713444829-21">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">permanent</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">transient</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">temporary</span><span class="w">
│ │ │ │ -    </span><span class="nf">significant</span><span class="p" data-group-id="8713444829-22">(</span><span class="p" data-group-id="8713444829-22">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">boolean</span><span class="p" data-group-id="8713444829-23">(</span><span class="p" data-group-id="8713444829-23">)</span><span class="w">
│ │ │ │ -    </span><span class="nf">shutdown</span><span class="p" data-group-id="8713444829-24">(</span><span class="p" data-group-id="8713444829-24">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">timeout</span><span class="p" data-group-id="8713444829-25">(</span><span class="p" data-group-id="8713444829-25">)</span><span class="w">
│ │ │ │ -    </span><span class="nf">worker</span><span class="p" data-group-id="8713444829-26">(</span><span class="p" data-group-id="8713444829-26">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">worker</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">supervisor</span></code></pre><ul><li><p><code class="inline">id</code> is used to identify the child specification internally by the supervisor.</p><p>The <code class="inline">id</code> key is mandatory.</p><p>Note that this identifier occasionally has been called &quot;name&quot;. As far as
│ │ │ │ +<p>The type definition for a child specification is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">child_spec</span><span class="p" data-group-id="9927721289-1">(</span><span class="p" data-group-id="9927721289-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9927721289-2">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">child_id</span><span class="p" data-group-id="9927721289-3">(</span><span class="p" data-group-id="9927721289-3">)</span><span class="p">,</span><span class="w">             </span><span class="c1">% mandatory</span><span class="w">
│ │ │ │ +                 </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">mfargs</span><span class="p" data-group-id="9927721289-4">(</span><span class="p" data-group-id="9927721289-4">)</span><span class="p">,</span><span class="w">            </span><span class="c1">% mandatory</span><span class="w">
│ │ │ │ +                 </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">restart</span><span class="p" data-group-id="9927721289-5">(</span><span class="p" data-group-id="9927721289-5">)</span><span class="p">,</span><span class="w">         </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +                 </span><span class="ss">significant</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">significant</span><span class="p" data-group-id="9927721289-6">(</span><span class="p" data-group-id="9927721289-6">)</span><span class="p">,</span><span class="w"> </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +                 </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">shutdown</span><span class="p" data-group-id="9927721289-7">(</span><span class="p" data-group-id="9927721289-7">)</span><span class="p">,</span><span class="w">       </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +                 </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">worker</span><span class="p" data-group-id="9927721289-8">(</span><span class="p" data-group-id="9927721289-8">)</span><span class="p">,</span><span class="w">             </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +                 </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">modules</span><span class="p" data-group-id="9927721289-9">(</span><span class="p" data-group-id="9927721289-9">)</span><span class="p" data-group-id="9927721289-2">}</span><span class="w">         </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +    </span><span class="nf">child_id</span><span class="p" data-group-id="9927721289-10">(</span><span class="p" data-group-id="9927721289-10">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="9927721289-11">(</span><span class="p" data-group-id="9927721289-11">)</span><span class="w">
│ │ │ │ +    </span><span class="nf">mfargs</span><span class="p" data-group-id="9927721289-12">(</span><span class="p" data-group-id="9927721289-12">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9927721289-13">{</span><span class="n">M</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">module</span><span class="p" data-group-id="9927721289-14">(</span><span class="p" data-group-id="9927721289-14">)</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="9927721289-15">(</span><span class="p" data-group-id="9927721289-15">)</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="9927721289-16">[</span><span class="nf">term</span><span class="p" data-group-id="9927721289-17">(</span><span class="p" data-group-id="9927721289-17">)</span><span class="p" data-group-id="9927721289-16">]</span><span class="p" data-group-id="9927721289-13">}</span><span class="w">
│ │ │ │ +    </span><span class="nf">modules</span><span class="p" data-group-id="9927721289-18">(</span><span class="p" data-group-id="9927721289-18">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9927721289-19">[</span><span class="nf">module</span><span class="p" data-group-id="9927721289-20">(</span><span class="p" data-group-id="9927721289-20">)</span><span class="p" data-group-id="9927721289-19">]</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">dynamic</span><span class="w">
│ │ │ │ +    </span><span class="nf">restart</span><span class="p" data-group-id="9927721289-21">(</span><span class="p" data-group-id="9927721289-21">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">permanent</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">transient</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">temporary</span><span class="w">
│ │ │ │ +    </span><span class="nf">significant</span><span class="p" data-group-id="9927721289-22">(</span><span class="p" data-group-id="9927721289-22">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">boolean</span><span class="p" data-group-id="9927721289-23">(</span><span class="p" data-group-id="9927721289-23">)</span><span class="w">
│ │ │ │ +    </span><span class="nf">shutdown</span><span class="p" data-group-id="9927721289-24">(</span><span class="p" data-group-id="9927721289-24">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">timeout</span><span class="p" data-group-id="9927721289-25">(</span><span class="p" data-group-id="9927721289-25">)</span><span class="w">
│ │ │ │ +    </span><span class="nf">worker</span><span class="p" data-group-id="9927721289-26">(</span><span class="p" data-group-id="9927721289-26">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">worker</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">supervisor</span></code></pre><ul><li><p><code class="inline">id</code> is used to identify the child specification internally by the supervisor.</p><p>The <code class="inline">id</code> key is mandatory.</p><p>Note that this identifier occasionally has been called &quot;name&quot;. As far as
│ │ │ │  possible, the terms &quot;identifier&quot; or &quot;id&quot; are now used but in order to keep
│ │ │ │  backwards compatibility, some occurrences of &quot;name&quot; can still be found, for
│ │ │ │  example in error messages.</p></li><li><p><code class="inline">start</code> defines the function call used to start the child process. It is a
│ │ │ │  module-function-arguments tuple used as <a href="../../../lib/../erts/doc/html/erlang.html#apply/3"><code class="inline">apply(M, F, A)</code></a>.</p><p>It is to be (or result in) a call to any of the following:</p><ul><li><a href="../../../lib/stdlib/doc/html/supervisor.html#start_link/3"><code class="inline">supervisor:start_link/2,3</code></a></li><li><a href="../../../lib/stdlib/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/3,4</code></a></li><li><a href="../../../lib/stdlib/doc/html/gen_statem.html#start_link/4"><code class="inline">gen_statem:start_link/3,4</code></a></li><li><a href="../../../lib/stdlib/doc/html/gen_event.html#start_link/2"><code class="inline">gen_event:start_link/0,1,2</code></a></li><li>A function compliant with these functions. For details, see
│ │ │ │  <a href="../../../lib/stdlib/doc/html/supervisor.html"><code class="inline">supervisor</code></a>.</li></ul><p>The <code class="inline">start</code> key is mandatory.</p></li><li><p><a href="" id="restart"></a> <code class="inline">restart</code> defines when a terminated child process is to be
│ │ │ │  restarted.</p><ul><li>A <code class="inline">permanent</code> child process is always restarted.</li><li>A <code class="inline">temporary</code> child process is never restarted (not even when the supervisor
│ │ │ │  restart strategy is <code class="inline">rest_for_one</code> or <code class="inline">one_for_all</code> and a sibling death
│ │ │ │ @@ -362,53 +362,53 @@
│ │ │ │  <code class="inline">supervisor</code>, the default value <code class="inline">infinity</code> will be used.</p></li><li><p><code class="inline">type</code> specifies whether the child process is a supervisor or a worker.</p><p>The <code class="inline">type</code> key is optional. If it is not given, the default value <code class="inline">worker</code>
│ │ │ │  will be used.</p></li><li><p><code class="inline">modules</code> has to be a list consisting of a single element. The value
│ │ │ │  of that element depends on the behaviour of the process:</p><ul><li>If the child process is a <code class="inline">gen_event</code>, the element has to be the atom
│ │ │ │  <code class="inline">dynamic</code>.</li><li>Otherwise, the element should be <code class="inline">Module</code>, where <code class="inline">Module</code> is the
│ │ │ │  name of the callback module.</li></ul><p>This information is used by the release handler during upgrades and
│ │ │ │  downgrades; see <a href="release_handling.xhtml">Release Handling</a>.</p><p>The <code class="inline">modules</code> key is optional. If it is not given, it defaults to <code class="inline">[M]</code>, where
│ │ │ │  <code class="inline">M</code> comes from the child's start <code class="inline">{M,F,A}</code>.</p></li></ul><p><em>Example:</em> The child specification to start the server <code class="inline">ch3</code> in the previous
│ │ │ │ -example looks as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0670136532-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="0670136532-2">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0670136532-3">[</span><span class="p" data-group-id="0670136532-3">]</span><span class="p" data-group-id="0670136532-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +example looks as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2529885413-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2529885413-2">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2529885413-3">[</span><span class="p" data-group-id="2529885413-3">]</span><span class="p" data-group-id="2529885413-2">}</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">permanent</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">worker</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="0670136532-4">[</span><span class="ss">ch3</span><span class="p" data-group-id="0670136532-4">]</span><span class="p" data-group-id="0670136532-1">}</span></code></pre><p>or simplified, relying on the default values:</p><pre><code class="text">#{id =&gt; ch3,
│ │ │ │ +  </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2529885413-4">[</span><span class="ss">ch3</span><span class="p" data-group-id="2529885413-4">]</span><span class="p" data-group-id="2529885413-1">}</span></code></pre><p>or simplified, relying on the default values:</p><pre><code class="text">#{id =&gt; ch3,
│ │ │ │    start =&gt; {ch3, start_link, []},
│ │ │ │    shutdown =&gt; brutal_kill}</code></pre><p>Example: A child specification to start the event manager from the chapter about
│ │ │ │ -<a href="events.xhtml#mgr">gen_event</a>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2553441722-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">error_man</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2553441722-2">{</span><span class="ss">gen_event</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2553441722-3">[</span><span class="p" data-group-id="2553441722-4">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">error_man</span><span class="p" data-group-id="2553441722-4">}</span><span class="p" data-group-id="2553441722-3">]</span><span class="p" data-group-id="2553441722-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">dynamic</span><span class="p" data-group-id="2553441722-1">}</span></code></pre><p>Both server and event manager are registered processes which can be expected to
│ │ │ │ +<a href="events.xhtml#mgr">gen_event</a>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8090404901-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">error_man</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8090404901-2">{</span><span class="ss">gen_event</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8090404901-3">[</span><span class="p" data-group-id="8090404901-4">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">error_man</span><span class="p" data-group-id="8090404901-4">}</span><span class="p" data-group-id="8090404901-3">]</span><span class="p" data-group-id="8090404901-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">dynamic</span><span class="p" data-group-id="8090404901-1">}</span></code></pre><p>Both server and event manager are registered processes which can be expected to
│ │ │ │  be always accessible. Thus they are specified to be <code class="inline">permanent</code>.</p><p><code class="inline">ch3</code> does not need to do any cleaning up before termination. Thus, no shutdown
│ │ │ │  time is needed, but <code class="inline">brutal_kill</code> is sufficient. <code class="inline">error_man</code> can need some time
│ │ │ │  for the event handlers to clean up, thus the shutdown time is set to 5000 ms
│ │ │ │ -(which is the default value).</p><p>Example: A child specification to start another supervisor:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7344573455-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">sup</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7344573455-2">{</span><span class="ss">sup</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7344573455-3">[</span><span class="p" data-group-id="7344573455-3">]</span><span class="p" data-group-id="7344573455-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +(which is the default value).</p><p>Example: A child specification to start another supervisor:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4049078226-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">sup</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4049078226-2">{</span><span class="ss">sup</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4049078226-3">[</span><span class="p" data-group-id="4049078226-3">]</span><span class="p" data-group-id="4049078226-2">}</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">transient</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="7344573455-1">}</span><span class="w"> </span><span class="c1">% will cause default shutdown=&gt;infinity</span></code></pre><p><a href="" id="super_tree"></a></p><h2 id="starting-a-supervisor" class="section-heading">
│ │ │ │ +  </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="4049078226-1">}</span><span class="w"> </span><span class="c1">% will cause default shutdown=&gt;infinity</span></code></pre><p><a href="" id="super_tree"></a></p><h2 id="starting-a-supervisor" class="section-heading">
│ │ │ │    <a href="#starting-a-supervisor" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Starting a Supervisor</span>
│ │ │ │  </h2>
│ │ │ │  <p>In the previous example, the supervisor is started by calling
│ │ │ │ -<code class="inline">ch_sup:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="7396468718-1">(</span><span class="p" data-group-id="7396468718-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="7396468718-2">(</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7396468718-3">[</span><span class="p" data-group-id="7396468718-3">]</span><span class="p" data-group-id="7396468718-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch_sup:start_link</code> calls function <a href="../../../lib/stdlib/doc/html/supervisor.html#start_link/2"><code class="inline">supervisor:start_link/2</code></a>, which spawns and
│ │ │ │ +<code class="inline">ch_sup:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="7704567951-1">(</span><span class="p" data-group-id="7704567951-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="7704567951-2">(</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7704567951-3">[</span><span class="p" data-group-id="7704567951-3">]</span><span class="p" data-group-id="7704567951-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch_sup:start_link</code> calls function <a href="../../../lib/stdlib/doc/html/supervisor.html#start_link/2"><code class="inline">supervisor:start_link/2</code></a>, which spawns and
│ │ │ │  links to a new process, a supervisor.</p><ul><li>The first argument, <code class="inline">ch_sup</code>, is the name of the callback module, that is, the
│ │ │ │  module where the <code class="inline">init</code> callback function is located.</li><li>The second argument, <code class="inline">[]</code>, is a term that is passed as is to the callback
│ │ │ │  function <code class="inline">init</code>. Here, <code class="inline">init</code> does not need any data and ignores the argument.</li></ul><p>In this case, the supervisor is not registered. Instead its pid must be used. A
│ │ │ │  name can be specified by calling
│ │ │ │  <a href="../../../lib/stdlib/doc/html/supervisor.html#start_link/3"><code class="inline">supervisor:start_link({local, Name}, Module, Args)</code></a>
│ │ │ │  or
│ │ │ │  <a href="../../../lib/stdlib/doc/html/supervisor.html#start_link/3"><code class="inline">supervisor:start_link({global, Name}, Module, Args)</code></a>.</p><p>The new supervisor process calls the callback function <code class="inline">ch_sup:init([])</code>. <code class="inline">init</code>
│ │ │ │ -has to return <code class="inline">{ok, {SupFlags, ChildSpecs}}</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="2865965715-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="2865965715-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2865965715-2">#{</span><span class="p" data-group-id="2865965715-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2865965715-3">[</span><span class="p" data-group-id="2865965715-4">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2865965715-5">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2865965715-6">[</span><span class="p" data-group-id="2865965715-6">]</span><span class="p" data-group-id="2865965715-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p" data-group-id="2865965715-4">}</span><span class="p" data-group-id="2865965715-3">]</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2865965715-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2865965715-8">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="2865965715-8">}</span><span class="p" data-group-id="2865965715-7">}</span><span class="p">.</span></code></pre><p>Subsequently, the supervisor starts its child processes according to the child
│ │ │ │ +has to return <code class="inline">{ok, {SupFlags, ChildSpecs}}</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="9611562635-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="9611562635-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9611562635-2">#{</span><span class="p" data-group-id="9611562635-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9611562635-3">[</span><span class="p" data-group-id="9611562635-4">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9611562635-5">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9611562635-6">[</span><span class="p" data-group-id="9611562635-6">]</span><span class="p" data-group-id="9611562635-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p" data-group-id="9611562635-4">}</span><span class="p" data-group-id="9611562635-3">]</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9611562635-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9611562635-8">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="9611562635-8">}</span><span class="p" data-group-id="9611562635-7">}</span><span class="p">.</span></code></pre><p>Subsequently, the supervisor starts its child processes according to the child
│ │ │ │  specifications in the start specification. In this case there is a single child
│ │ │ │  process, called <code class="inline">ch3</code>.</p><p><a href="../../../lib/stdlib/doc/html/supervisor.html#start_link/3"><code class="inline">supervisor:start_link/3</code></a> is synchronous. It does not return until all child
│ │ │ │  processes have been started.</p><h2 id="adding-a-child-process" class="section-heading">
│ │ │ │    <a href="#adding-a-child-process" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Adding a Child Process</span>
│ │ │ │ @@ -437,31 +437,31 @@
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Simplified one_for_one Supervisors</span>
│ │ │ │  </h2>
│ │ │ │  <p>A supervisor with restart strategy <code class="inline">simple_one_for_one</code> is a simplified
│ │ │ │  <code class="inline">one_for_one</code> supervisor, where all child processes are dynamically added
│ │ │ │  instances of the same process.</p><p>The following is an example of a callback module for a <code class="inline">simple_one_for_one</code>
│ │ │ │ -supervisor:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5798419478-1">(</span><span class="ss">simple_sup</span><span class="p" data-group-id="5798419478-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="5798419478-2">(</span><span class="ss">supervisor</span><span class="p" data-group-id="5798419478-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +supervisor:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1457424526-1">(</span><span class="ss">simple_sup</span><span class="p" data-group-id="1457424526-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="1457424526-2">(</span><span class="ss">supervisor</span><span class="p" data-group-id="1457424526-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5798419478-3">(</span><span class="p" data-group-id="5798419478-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5798419478-4">]</span><span class="p" data-group-id="5798419478-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5798419478-5">(</span><span class="p" data-group-id="5798419478-6">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5798419478-6">]</span><span class="p" data-group-id="5798419478-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1457424526-3">(</span><span class="p" data-group-id="1457424526-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1457424526-4">]</span><span class="p" data-group-id="1457424526-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1457424526-5">(</span><span class="p" data-group-id="1457424526-6">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1457424526-6">]</span><span class="p" data-group-id="1457424526-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="5798419478-7">(</span><span class="p" data-group-id="5798419478-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="5798419478-8">(</span><span class="ss">simple_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5798419478-9">[</span><span class="p" data-group-id="5798419478-9">]</span><span class="p" data-group-id="5798419478-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="1457424526-7">(</span><span class="p" data-group-id="1457424526-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="1457424526-8">(</span><span class="ss">simple_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1457424526-9">[</span><span class="p" data-group-id="1457424526-9">]</span><span class="p" data-group-id="1457424526-8">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="5798419478-10">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="5798419478-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5798419478-11">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">simple_one_for_one</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="1457424526-10">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="1457424526-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1457424526-11">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">simple_one_for_one</span><span class="p">,</span><span class="w">
│ │ │ │                   </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ │ -                 </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="5798419478-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5798419478-12">[</span><span class="p" data-group-id="5798419478-13">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">call</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5798419478-14">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5798419478-15">[</span><span class="p" data-group-id="5798419478-15">]</span><span class="p" data-group-id="5798419478-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p" data-group-id="5798419478-13">}</span><span class="p" data-group-id="5798419478-12">]</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5798419478-16">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5798419478-17">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="5798419478-17">}</span><span class="p" data-group-id="5798419478-16">}</span><span class="p">.</span></code></pre><p>When started, the supervisor does not start any child
│ │ │ │ +                 </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="1457424526-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1457424526-12">[</span><span class="p" data-group-id="1457424526-13">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">call</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1457424526-14">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1457424526-15">[</span><span class="p" data-group-id="1457424526-15">]</span><span class="p" data-group-id="1457424526-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p" data-group-id="1457424526-13">}</span><span class="p" data-group-id="1457424526-12">]</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1457424526-16">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1457424526-17">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="1457424526-17">}</span><span class="p" data-group-id="1457424526-16">}</span><span class="p">.</span></code></pre><p>When started, the supervisor does not start any child
│ │ │ │  processes. Instead, all child processes need to be added dynamically by
│ │ │ │  calling <a href="../../../lib/stdlib/doc/html/supervisor.html#start_child/2"><code class="inline">supervisor:start_child(Sup, List)</code></a>.</p><p><code class="inline">Sup</code> is the pid, or name, of the supervisor. <code class="inline">List</code> is an arbitrary list of
│ │ │ │  terms, which are added to the list of arguments specified in the child
│ │ │ │  specification. If the start function is specified as <code class="inline">{M, F, A}</code>, the child
│ │ │ │  process is started by calling <a href="../../../lib/../erts/doc/html/erlang.html#apply/3"><code class="inline">apply(M, F, A++List)</code></a>.</p><p>For example, adding a child to <code class="inline">simple_sup</code> above:</p><pre><code class="text">supervisor:start_child(Pid, [id1])</code></pre><p>The result is that the child process is started by calling
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#apply/3"><code class="inline">apply(call, start_link, []++[id1])</code></a>, or actually:</p><pre><code class="text">call:start_link(id1)</code></pre><p>A child under a <code class="inline">simple_one_for_one</code> supervisor can be terminated with the
│ │ │ │  following:</p><pre><code class="text">supervisor:terminate_child(Sup, Pid)</code></pre><p><code class="inline">Sup</code> is the pid, or name, of the supervisor and <code class="inline">Pid</code> is the pid of the child.</p><p>Because a <code class="inline">simple_one_for_one</code> supervisor can have many children, it shuts them
│ │ │ ├── OEBPS/statem.xhtml
│ │ │ │ @@ -29,15 +29,15 @@
│ │ │ │  </h2>
│ │ │ │  <p>Established Automata Theory does not deal much with how a <em>state transition</em>
│ │ │ │  is triggered, but assumes that the output is a function of the input
│ │ │ │  (and the state) and that they are some kind of values.</p><p>For an Event-Driven State Machine, the input is an <em>event</em> that triggers
│ │ │ │  a <em>state transition</em> and the output is actions executed during
│ │ │ │  the <em>state transition</em>.  Analogously to the mathematical model
│ │ │ │  of a Finite State Machine, it can be described as a set of relations
│ │ │ │ -of the following form:</p><pre><code class="makeup erlang" translate="no"><span class="n">State</span><span class="p" data-group-id="5248319249-1">(</span><span class="n">S</span><span class="p" data-group-id="5248319249-1">)</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="5248319249-2">(</span><span class="n">E</span><span class="p" data-group-id="5248319249-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Actions</span><span class="p" data-group-id="5248319249-3">(</span><span class="n">A</span><span class="p" data-group-id="5248319249-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5248319249-4">(</span><span class="n">S</span><span class="err">&#39;</span><span class="p" data-group-id="5248319249-4">)</span></code></pre><p>These relations are interpreted as follows: if we are in state <code class="inline">S</code>,
│ │ │ │ +of the following form:</p><pre><code class="makeup erlang" translate="no"><span class="n">State</span><span class="p" data-group-id="1501328431-1">(</span><span class="n">S</span><span class="p" data-group-id="1501328431-1">)</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="1501328431-2">(</span><span class="n">E</span><span class="p" data-group-id="1501328431-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Actions</span><span class="p" data-group-id="1501328431-3">(</span><span class="n">A</span><span class="p" data-group-id="1501328431-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="1501328431-4">(</span><span class="n">S</span><span class="err">&#39;</span><span class="p" data-group-id="1501328431-4">)</span></code></pre><p>These relations are interpreted as follows: if we are in state <code class="inline">S</code>,
│ │ │ │  and event <code class="inline">E</code> occurs, we are to perform actions <code class="inline">A</code>, and make a transition
│ │ │ │  to state <code class="inline">S'</code>.  Notice that <code class="inline">S'</code> can be equal to <code class="inline">S</code>,
│ │ │ │  and that <code class="inline">A</code> can be empty.</p><p>In <code class="inline">gen_statem</code> we define a <em>state change</em> as a <em>state transition</em> in which the
│ │ │ │  new state <code class="inline">S'</code> is different from the current state <code class="inline">S</code>, where &quot;different&quot; means
│ │ │ │  Erlang's strict inequality: <code class="inline">=/=</code> also known as &quot;does not match&quot;. <code class="inline">gen_statem</code>
│ │ │ │  does more things during <em>state changes</em> than during other <em>state transitions</em>.</p><p>As <code class="inline">A</code> and <code class="inline">S'</code> depend only on <code class="inline">S</code> and <code class="inline">E</code>, the kind of state machine described
│ │ │ │  here is a Mealy machine (see, for example, the Wikipedia article
│ │ │ │ @@ -310,20 +310,20 @@
│ │ │ │    </a>
│ │ │ │    <span class="text">State Enter Calls</span>
│ │ │ │  </h2>
│ │ │ │  <p>The <code class="inline">gen_statem</code> behaviour can, if this is enabled, regardless of <em>callback
│ │ │ │  mode</em>, automatically call the <a href="../../../lib/stdlib/doc/html/gen_statem.html#t:state_enter/0"><em>state callback</em></a>
│ │ │ │  with special arguments whenever the state changes, so you can write
│ │ │ │  state enter actions near the rest of the <em>state transition</em> rules.
│ │ │ │ -It typically looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">StateName</span><span class="p" data-group-id="9030319854-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9030319854-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +It typically looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">StateName</span><span class="p" data-group-id="2715942069-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2715942069-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">enter</span><span class="w"> </span><span class="ss">actions</span><span class="w"> </span><span class="ss">here</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9030319854-2">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">NewData</span><span class="p" data-group-id="9030319854-2">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="n">StateName</span><span class="p" data-group-id="9030319854-3">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9030319854-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2715942069-2">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">NewData</span><span class="p" data-group-id="2715942069-2">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="n">StateName</span><span class="p" data-group-id="2715942069-3">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2715942069-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">actions</span><span class="w"> </span><span class="ss">here</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9030319854-4">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="n">NewStateName</span><span class="p">,</span><span class="w"> </span><span class="n">NewData</span><span class="p" data-group-id="9030319854-4">}</span><span class="p">.</span></code></pre><p>Since the <em>state enter call</em> is not an event there are restrictions on the
│ │ │ │ +    </span><span class="p" data-group-id="2715942069-4">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="n">NewStateName</span><span class="p">,</span><span class="w"> </span><span class="n">NewData</span><span class="p" data-group-id="2715942069-4">}</span><span class="p">.</span></code></pre><p>Since the <em>state enter call</em> is not an event there are restrictions on the
│ │ │ │  allowed return value and state <a href="#transition-actions"><em>transition actions</em></a>.
│ │ │ │  You must not change the state, <a href="#postponing-events">postpone</a> this non-event,
│ │ │ │  <a href="#inserted-events">insert any events</a>, or change the
│ │ │ │  <a href="#callback-module"><em>callback module</em></a>.</p><p>The first state that is entered after <a href="../../../lib/stdlib/doc/html/gen_statem.html#c:init/1"><code class="inline">gen_statem:init/1</code></a> will get
│ │ │ │  a <em>state enter call</em> with <code class="inline">OldState</code> equal to the current state.</p><p>You may repeat the <em>state enter call</em> using the <code class="inline">{repeat_state,...}</code> return
│ │ │ │  value from the <a href="#state-callback"><em>state callback</em></a>. In this case
│ │ │ │  <code class="inline">OldState</code> will also be equal to the current state.</p><p>Depending on how your state machine is specified, this can be a very useful
│ │ │ │ @@ -404,72 +404,72 @@
│ │ │ │  
│ │ │ │      locked      --&gt; check_code : {button, Button}&lt;br /&gt;* Collect Buttons
│ │ │ │      check_code  --&gt; locked     : Incorrect code
│ │ │ │      check_code  --&gt; open       : Correct code&lt;br /&gt;* do_unlock()&lt;br /&gt;* Clear Buttons&lt;br /&gt;* Set state_timeout 10 s
│ │ │ │  
│ │ │ │      open        --&gt; open   : {button, Digit}
│ │ │ │      open        --&gt; locked : state_timeout&lt;br /&gt;* do_lock()</code></pre><p>This code lock state machine can be implemented using <a href="../../../lib/stdlib/doc/html/gen_statem.html"><code class="inline">gen_statem</code></a> with
│ │ │ │ -the following <em>callback module</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4640536711-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="4640536711-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="4640536711-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="4640536711-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4640536711-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock</span><span class="p" data-group-id="4640536711-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +the following <em>callback module</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5243615644-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="5243615644-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="5243615644-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="5243615644-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5243615644-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock</span><span class="p" data-group-id="5243615644-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4640536711-4">(</span><span class="p" data-group-id="4640536711-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4640536711-5">]</span><span class="p" data-group-id="4640536711-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4640536711-6">(</span><span class="p" data-group-id="4640536711-7">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4640536711-7">]</span><span class="p" data-group-id="4640536711-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4640536711-8">(</span><span class="p" data-group-id="4640536711-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="4640536711-9">]</span><span class="p" data-group-id="4640536711-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4640536711-10">(</span><span class="p" data-group-id="4640536711-11">[</span><span class="ss">locked</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">open</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="4640536711-11">]</span><span class="p" data-group-id="4640536711-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="4640536711-12">(</span><span class="n">Code</span><span class="p" data-group-id="4640536711-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="4640536711-13">(</span><span class="p" data-group-id="4640536711-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="4640536711-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4640536711-15">[</span><span class="p" data-group-id="4640536711-15">]</span><span class="p" data-group-id="4640536711-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">button</span><span class="p" data-group-id="4640536711-16">(</span><span class="n">Button</span><span class="p" data-group-id="4640536711-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="4640536711-17">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4640536711-18">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="4640536711-18">}</span><span class="p" data-group-id="4640536711-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="4640536711-19">(</span><span class="n">Code</span><span class="p" data-group-id="4640536711-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="4640536711-20">(</span><span class="p" data-group-id="4640536711-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4640536711-21">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="4640536711-22">(</span><span class="n">Code</span><span class="p" data-group-id="4640536711-22">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4640536711-23">[</span><span class="p" data-group-id="4640536711-23">]</span><span class="p" data-group-id="4640536711-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4640536711-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4640536711-24">}</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="4640536711-25">(</span><span class="p" data-group-id="4640536711-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">state_functions</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="7977973321-1">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7977973321-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7977973321-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="7977973321-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="7977973321-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7977973321-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5243615644-4">(</span><span class="p" data-group-id="5243615644-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5243615644-5">]</span><span class="p" data-group-id="5243615644-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5243615644-6">(</span><span class="p" data-group-id="5243615644-7">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5243615644-7">]</span><span class="p" data-group-id="5243615644-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5243615644-8">(</span><span class="p" data-group-id="5243615644-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="5243615644-9">]</span><span class="p" data-group-id="5243615644-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5243615644-10">(</span><span class="p" data-group-id="5243615644-11">[</span><span class="ss">locked</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">open</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="5243615644-11">]</span><span class="p" data-group-id="5243615644-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="5243615644-12">(</span><span class="n">Code</span><span class="p" data-group-id="5243615644-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="5243615644-13">(</span><span class="p" data-group-id="5243615644-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="5243615644-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5243615644-15">[</span><span class="p" data-group-id="5243615644-15">]</span><span class="p" data-group-id="5243615644-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">button</span><span class="p" data-group-id="5243615644-16">(</span><span class="n">Button</span><span class="p" data-group-id="5243615644-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="5243615644-17">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5243615644-18">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5243615644-18">}</span><span class="p" data-group-id="5243615644-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="5243615644-19">(</span><span class="n">Code</span><span class="p" data-group-id="5243615644-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="5243615644-20">(</span><span class="p" data-group-id="5243615644-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5243615644-21">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="5243615644-22">(</span><span class="n">Code</span><span class="p" data-group-id="5243615644-22">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5243615644-23">[</span><span class="p" data-group-id="5243615644-23">]</span><span class="p" data-group-id="5243615644-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5243615644-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5243615644-24">}</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="5243615644-25">(</span><span class="p" data-group-id="5243615644-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">state_functions</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="3983708280-1">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3983708280-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3983708280-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="3983708280-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="3983708280-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3983708280-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │          </span><span class="k">if</span><span class="w">
│ │ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="7977973321-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="7977973321-4">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="3983708280-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="3983708280-4">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="7977973321-5">(</span><span class="n">Buttons</span><span class="p" data-group-id="7977973321-5">)</span><span class="w">
│ │ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="7977973321-6">[</span><span class="n">Button</span><span class="p" data-group-id="7977973321-6">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="3983708280-5">(</span><span class="n">Buttons</span><span class="p" data-group-id="3983708280-5">)</span><span class="w">
│ │ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="3983708280-6">[</span><span class="n">Button</span><span class="p" data-group-id="3983708280-6">]</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="7977973321-7">(</span><span class="p" data-group-id="7977973321-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="7977973321-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7977973321-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="7977973321-10">[</span><span class="p" data-group-id="7977973321-10">]</span><span class="p" data-group-id="7977973321-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="7977973321-11">[</span><span class="p" data-group-id="7977973321-12">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="7977973321-12">}</span><span class="p" data-group-id="7977973321-11">]</span><span class="p" data-group-id="7977973321-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="3983708280-7">(</span><span class="p" data-group-id="3983708280-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="3983708280-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3983708280-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="3983708280-10">[</span><span class="p" data-group-id="3983708280-10">]</span><span class="p" data-group-id="3983708280-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="3983708280-11">[</span><span class="p" data-group-id="3983708280-12">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="3983708280-12">}</span><span class="p" data-group-id="3983708280-11">]</span><span class="p" data-group-id="3983708280-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="7977973321-13">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7977973321-14">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="7977973321-14">}</span><span class="p" data-group-id="7977973321-13">}</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="6400259060-1">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w">  </span><span class="n">Data</span><span class="p" data-group-id="6400259060-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="6400259060-2">(</span><span class="p" data-group-id="6400259060-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6400259060-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6400259060-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="6400259060-4">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6400259060-5">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6400259060-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6400259060-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6400259060-6">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6400259060-6">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">do_lock</span><span class="p" data-group-id="2795348104-1">(</span><span class="p" data-group-id="2795348104-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2795348104-2">(</span><span class="s">&quot;Lock</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2795348104-3">[</span><span class="p" data-group-id="2795348104-3">]</span><span class="p" data-group-id="2795348104-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">do_unlock</span><span class="p" data-group-id="2795348104-4">(</span><span class="p" data-group-id="2795348104-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2795348104-5">(</span><span class="s">&quot;Unlock</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2795348104-6">[</span><span class="p" data-group-id="2795348104-6">]</span><span class="p" data-group-id="2795348104-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="3983708280-13">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3983708280-14">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="3983708280-14">}</span><span class="p" data-group-id="3983708280-13">}</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="6930599205-1">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w">  </span><span class="n">Data</span><span class="p" data-group-id="6930599205-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="6930599205-2">(</span><span class="p" data-group-id="6930599205-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6930599205-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6930599205-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="6930599205-4">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6930599205-5">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6930599205-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6930599205-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6930599205-6">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6930599205-6">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">do_lock</span><span class="p" data-group-id="9685759974-1">(</span><span class="p" data-group-id="9685759974-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9685759974-2">(</span><span class="s">&quot;Lock</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9685759974-3">[</span><span class="p" data-group-id="9685759974-3">]</span><span class="p" data-group-id="9685759974-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">do_unlock</span><span class="p" data-group-id="9685759974-4">(</span><span class="p" data-group-id="9685759974-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9685759974-5">(</span><span class="s">&quot;Unlock</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9685759974-6">[</span><span class="p" data-group-id="9685759974-6">]</span><span class="p" data-group-id="9685759974-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="2795348104-7">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="2795348104-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="2795348104-8">(</span><span class="p" data-group-id="2795348104-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="9685759974-7">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="9685759974-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="9685759974-8">(</span><span class="p" data-group-id="9685759974-8">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><h2 id="starting-gen_statem" class="section-heading">
│ │ │ │    <a href="#starting-gen_statem" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Starting gen_statem</span>
│ │ │ │  </h2>
│ │ │ │  <p>In the example in the previous section, <code class="inline">gen_statem</code> is started by calling
│ │ │ │ -<code class="inline">code_lock:start_link(Code)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="6721209538-1">(</span><span class="n">Code</span><span class="p" data-group-id="6721209538-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="6721209538-2">(</span><span class="p" data-group-id="6721209538-3">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="6721209538-3">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6721209538-4">[</span><span class="p" data-group-id="6721209538-4">]</span><span class="p" data-group-id="6721209538-2">)</span><span class="p">.</span></code></pre><p><code class="inline">start_link/1</code> calls function <a href="../../../lib/stdlib/doc/html/gen_statem.html#start_link/4"><code class="inline">gen_statem:start_link/4</code></a>,
│ │ │ │ +<code class="inline">code_lock:start_link(Code)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="8427662624-1">(</span><span class="n">Code</span><span class="p" data-group-id="8427662624-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="8427662624-2">(</span><span class="p" data-group-id="8427662624-3">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="8427662624-3">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8427662624-4">[</span><span class="p" data-group-id="8427662624-4">]</span><span class="p" data-group-id="8427662624-2">)</span><span class="p">.</span></code></pre><p><code class="inline">start_link/1</code> calls function <a href="../../../lib/stdlib/doc/html/gen_statem.html#start_link/4"><code class="inline">gen_statem:start_link/4</code></a>,
│ │ │ │  which spawns and links to a new process, a <code class="inline">gen_statem</code>.</p><ul><li><p>The first argument, <code class="inline">{local,?NAME}</code>, specifies the name. In this case, the
│ │ │ │  <code class="inline">gen_statem</code> is locally registered as <code class="inline">code_lock</code> through the macro <code class="inline">?NAME</code>.</p><p>If the name is omitted, the <code class="inline">gen_statem</code> is not registered. Instead its pid
│ │ │ │  must be used. The name can also be specified as <code class="inline">{global, Name}</code>, then the
│ │ │ │  <code class="inline">gen_statem</code> is registered using <a href="../../../lib/kernel/doc/html/global.html#register_name/2"><code class="inline">global:register_name/2</code></a> in Kernel.</p></li><li><p>The second argument, <code class="inline">?MODULE</code>, is the name of the <em>callback module</em>,
│ │ │ │  that is, the module where the callback functions are located,
│ │ │ │  which is this module.</p><p>The interface functions (<code class="inline">start_link/1</code> and <code class="inline">button/1</code>) are located in the
│ │ │ │  same module as the callback functions (<code class="inline">init/1</code>, <code class="inline">locked/3</code>, and <code class="inline">open/3</code>).
│ │ │ │ @@ -479,184 +479,184 @@
│ │ │ │  see <a href="../../../lib/stdlib/doc/html/gen_statem.html#start_link/3"><code class="inline">gen_statem:start_link/3</code></a>.</p></li></ul><p>If name registration succeeds, the new <code class="inline">gen_statem</code> process calls callback
│ │ │ │  function <code class="inline">code_lock:init(Code)</code>. This function is expected to return
│ │ │ │  <code class="inline">{ok, State, Data}</code>, where <code class="inline">State</code> is the initial state of the <code class="inline">gen_statem</code>,
│ │ │ │  in this case <code class="inline">locked</code>; assuming that the door is locked to begin with.
│ │ │ │  <code class="inline">Data</code> is the internal server data of the <code class="inline">gen_statem</code>. Here the server data
│ │ │ │  is a <a href="../../../lib/stdlib/doc/html/maps.html"><code class="inline">map()</code></a> with key <code class="inline">code</code> that stores the correct
│ │ │ │  button sequence, key <code class="inline">length</code> stores its length, and key <code class="inline">buttons</code>
│ │ │ │ -that stores the collected buttons up to the same length.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="3333355111-1">(</span><span class="n">Code</span><span class="p" data-group-id="3333355111-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="3333355111-2">(</span><span class="p" data-group-id="3333355111-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3333355111-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="3333355111-4">(</span><span class="n">Code</span><span class="p" data-group-id="3333355111-4">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3333355111-5">[</span><span class="p" data-group-id="3333355111-5">]</span><span class="p" data-group-id="3333355111-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3333355111-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3333355111-6">}</span><span class="p">.</span></code></pre><p>Function <a href="../../../lib/stdlib/doc/html/gen_statem.html#start_link/3"><code class="inline">gen_statem:start_link/3,4</code></a>
│ │ │ │ +that stores the collected buttons up to the same length.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="1347632833-1">(</span><span class="n">Code</span><span class="p" data-group-id="1347632833-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="1347632833-2">(</span><span class="p" data-group-id="1347632833-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1347632833-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="1347632833-4">(</span><span class="n">Code</span><span class="p" data-group-id="1347632833-4">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1347632833-5">[</span><span class="p" data-group-id="1347632833-5">]</span><span class="p" data-group-id="1347632833-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1347632833-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1347632833-6">}</span><span class="p">.</span></code></pre><p>Function <a href="../../../lib/stdlib/doc/html/gen_statem.html#start_link/3"><code class="inline">gen_statem:start_link/3,4</code></a>
│ │ │ │  is synchronous. It does not return until the <code class="inline">gen_statem</code> is initialized
│ │ │ │  and is ready to receive events.</p><p>Function <a href="../../../lib/stdlib/doc/html/gen_statem.html#start_link/3"><code class="inline">gen_statem:start_link/3,4</code></a>
│ │ │ │  must be used if the <code class="inline">gen_statem</code> is part of a supervision tree, that is,
│ │ │ │  started by a supervisor.  Function
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_statem.html#start/3"><code class="inline">gen_statem:start/3,4</code></a> can be used to start
│ │ │ │  a standalone <code class="inline">gen_statem</code>, meaning it is not part of a supervision tree.</p><p>Function <a href="../../../lib/stdlib/doc/html/gen_statem.html#c:callback_mode/0"><code class="inline">Module:callback_mode/0</code></a> selects
│ │ │ │  the <a href="#callback-modes"><code class="inline">CallbackMode</code></a> for the <em>callback module</em>,
│ │ │ │  in this case <a href="../../../lib/stdlib/doc/html/gen_statem.html#t:callback_mode/0"><code class="inline">state_functions</code></a>.
│ │ │ │ -That is, each state has its own handler function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">callback_mode</span><span class="p" data-group-id="9091880263-1">(</span><span class="p" data-group-id="9091880263-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +That is, each state has its own handler function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">callback_mode</span><span class="p" data-group-id="3897597299-1">(</span><span class="p" data-group-id="3897597299-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">state_functions</span><span class="p">.</span></code></pre><h2 id="handling-events" class="section-heading">
│ │ │ │    <a href="#handling-events" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Handling Events</span>
│ │ │ │  </h2>
│ │ │ │  <p>The function notifying the code lock about a button event is implemented using
│ │ │ │ -<a href="../../../lib/stdlib/doc/html/gen_statem.html#cast/2"><code class="inline">gen_statem:cast/2</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">button</span><span class="p" data-group-id="0392646979-1">(</span><span class="n">Button</span><span class="p" data-group-id="0392646979-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="0392646979-2">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0392646979-3">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0392646979-3">}</span><span class="p" data-group-id="0392646979-2">)</span><span class="p">.</span></code></pre><p>The first argument is the name of the <code class="inline">gen_statem</code> and must agree with
│ │ │ │ +<a href="../../../lib/stdlib/doc/html/gen_statem.html#cast/2"><code class="inline">gen_statem:cast/2</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">button</span><span class="p" data-group-id="7095673949-1">(</span><span class="n">Button</span><span class="p" data-group-id="7095673949-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="7095673949-2">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7095673949-3">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7095673949-3">}</span><span class="p" data-group-id="7095673949-2">)</span><span class="p">.</span></code></pre><p>The first argument is the name of the <code class="inline">gen_statem</code> and must agree with
│ │ │ │  the name used to start it. So, we use the same macro <code class="inline">?NAME</code> as when starting.
│ │ │ │  <code class="inline">{button, Button}</code> is the event content.</p><p>The event is sent to the <code class="inline">gen_statem</code>. When the event is received, the
│ │ │ │  <code class="inline">gen_statem</code> calls <code class="inline">StateName(cast, Event, Data)</code>, which is expected
│ │ │ │  to return a tuple <code class="inline">{next_state, NewStateName, NewData}</code>, or
│ │ │ │  <code class="inline">{next_state, NewStateName, NewData, Actions}</code>. <code class="inline">StateName</code> is the name
│ │ │ │  of the current state and <code class="inline">NewStateName</code> is the name of the next state.
│ │ │ │  <code class="inline">NewData</code> is a new value for the server data of the <code class="inline">gen_statem</code>,
│ │ │ │ -and <code class="inline">Actions</code> is a list of actions to be performed by the <code class="inline">gen_statem</code> engine.</p><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="0294368630-1">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0294368630-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0294368630-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="0294368630-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="0294368630-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0294368630-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +and <code class="inline">Actions</code> is a list of actions to be performed by the <code class="inline">gen_statem</code> engine.</p><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="2265947935-1">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2265947935-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2265947935-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="2265947935-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="2265947935-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2265947935-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │          </span><span class="k">if</span><span class="w">
│ │ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="0294368630-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="0294368630-4">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="2265947935-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="2265947935-4">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="0294368630-5">(</span><span class="n">Buttons</span><span class="p" data-group-id="0294368630-5">)</span><span class="w">
│ │ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="0294368630-6">[</span><span class="n">Button</span><span class="p" data-group-id="0294368630-6">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="2265947935-5">(</span><span class="n">Buttons</span><span class="p" data-group-id="2265947935-5">)</span><span class="w">
│ │ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="2265947935-6">[</span><span class="n">Button</span><span class="p" data-group-id="2265947935-6">]</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="0294368630-7">(</span><span class="p" data-group-id="0294368630-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="0294368630-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0294368630-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="0294368630-10">[</span><span class="p" data-group-id="0294368630-10">]</span><span class="p" data-group-id="0294368630-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="0294368630-11">[</span><span class="p" data-group-id="0294368630-12">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="0294368630-12">}</span><span class="p" data-group-id="0294368630-11">]</span><span class="p" data-group-id="0294368630-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="2265947935-7">(</span><span class="p" data-group-id="2265947935-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="2265947935-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2265947935-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="2265947935-10">[</span><span class="p" data-group-id="2265947935-10">]</span><span class="p" data-group-id="2265947935-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="2265947935-11">[</span><span class="p" data-group-id="2265947935-12">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="2265947935-12">}</span><span class="p" data-group-id="2265947935-11">]</span><span class="p" data-group-id="2265947935-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="0294368630-13">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0294368630-14">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="0294368630-14">}</span><span class="p" data-group-id="0294368630-13">}</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="2265947935-13">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2265947935-14">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="2265947935-14">}</span><span class="p" data-group-id="2265947935-13">}</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>In state <code class="inline">locked</code>, when a button is pressed, it is collected with the
│ │ │ │  previously pressed buttons up to the length of the correct code, then
│ │ │ │  compared with the correct code. Depending on the result, the door is
│ │ │ │  either unlocked and the <code class="inline">gen_statem</code> goes to state <code class="inline">open</code>, or the door
│ │ │ │  remains in state <code class="inline">locked</code>.</p><p>When changing to state <code class="inline">open</code>, the collected buttons are reset, the lock
│ │ │ │ -unlocked, and a <em>state time-out</em> for 10 seconds is started.</p><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="0745552567-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0745552567-2">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0745552567-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0745552567-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0745552567-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0745552567-3">}</span><span class="p">.</span></code></pre><p>In state <code class="inline">open</code>, a button event is ignored by staying in the same state.
│ │ │ │ +unlocked, and a <em>state time-out</em> for 10 seconds is started.</p><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="3775260377-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3775260377-2">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="3775260377-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3775260377-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3775260377-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3775260377-3">}</span><span class="p">.</span></code></pre><p>In state <code class="inline">open</code>, a button event is ignored by staying in the same state.
│ │ │ │  This can also be done by returning <code class="inline">{keep_state, Data}</code>, or in this case
│ │ │ │  since <code class="inline">Data</code> is unchanged, by returning <code class="inline">keep_state_and_data</code>.</p><h2 id="state-time-outs" class="section-heading">
│ │ │ │    <a href="#state-time-outs" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">State Time-Outs</span>
│ │ │ │  </h2>
│ │ │ │  <p>When a correct code has been given, the door is unlocked and the following
│ │ │ │ -tuple is returned from <code class="inline">locked/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4105529011-1">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4105529011-2">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="4105529011-3">[</span><span class="p" data-group-id="4105529011-3">]</span><span class="p" data-group-id="4105529011-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4105529011-4">[</span><span class="p" data-group-id="4105529011-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="4105529011-5">}</span><span class="p" data-group-id="4105529011-4">]</span><span class="p" data-group-id="4105529011-1">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span></code></pre><p>10,000 is a time-out value in milliseconds. After this time (10 seconds),
│ │ │ │ +tuple is returned from <code class="inline">locked/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9837633917-1">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9837633917-2">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="9837633917-3">[</span><span class="p" data-group-id="9837633917-3">]</span><span class="p" data-group-id="9837633917-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9837633917-4">[</span><span class="p" data-group-id="9837633917-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="9837633917-5">}</span><span class="p" data-group-id="9837633917-4">]</span><span class="p" data-group-id="9837633917-1">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span></code></pre><p>10,000 is a time-out value in milliseconds. After this time (10 seconds),
│ │ │ │  a time-out occurs. Then, <code class="inline">StateName(state_timeout, lock, Data)</code> is called.
│ │ │ │  The time-out occurs when the door has been in state <code class="inline">open</code> for 10 seconds.
│ │ │ │ -After that the door is locked again:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="4886893464-1">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w">  </span><span class="n">Data</span><span class="p" data-group-id="4886893464-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="4886893464-2">(</span><span class="p" data-group-id="4886893464-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4886893464-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4886893464-3">}</span><span class="p">;</span></code></pre><p>The timer for a <em>state time-out</em> is automatically canceled when
│ │ │ │ +After that the door is locked again:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="7200396073-1">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w">  </span><span class="n">Data</span><span class="p" data-group-id="7200396073-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="7200396073-2">(</span><span class="p" data-group-id="7200396073-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7200396073-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7200396073-3">}</span><span class="p">;</span></code></pre><p>The timer for a <em>state time-out</em> is automatically canceled when
│ │ │ │  the state machine does a <em>state change</em>.</p><p>You can restart, cancel, or update a <em>state time-out</em>. See section
│ │ │ │  <a href="#time-outs"><em>Time-Outs</em></a> for details.</p><h2 id="all-state-events" class="section-heading">
│ │ │ │    <a href="#all-state-events" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">All State Events</span>
│ │ │ │  </h2>
│ │ │ │  <p>Sometimes events can arrive in any state of the <code class="inline">gen_statem</code>. It is convenient
│ │ │ │  to handle these in a common state handler function that all state functions
│ │ │ │  call for events not specific to the state.</p><p>Consider a <code class="inline">code_length/0</code> function that returns the length
│ │ │ │  of the correct code.  We dispatch all events that are not state-specific
│ │ │ │  to the common function <code class="inline">handle_common/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1586865189-1">(</span><span class="p" data-group-id="1586865189-2">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1586865189-2">]</span><span class="p" data-group-id="1586865189-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9649490313-1">(</span><span class="p" data-group-id="9649490313-2">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9649490313-2">]</span><span class="p" data-group-id="9649490313-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">code_length</span><span class="p" data-group-id="1586865189-3">(</span><span class="p" data-group-id="1586865189-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="1586865189-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="1586865189-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">code_length</span><span class="p" data-group-id="9649490313-3">(</span><span class="p" data-group-id="9649490313-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="9649490313-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="9649490313-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="1586865189-5">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1586865189-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="1586865189-6">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1586865189-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">handle_common</span><span class="p" data-group-id="1586865189-7">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1586865189-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="9649490313-5">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="9649490313-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="9649490313-6">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9649490313-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">handle_common</span><span class="p" data-group-id="9649490313-7">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9649490313-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="1586865189-8">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1586865189-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="1586865189-9">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1586865189-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">handle_common</span><span class="p" data-group-id="1586865189-10">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1586865189-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="1586865189-11">(</span><span class="p" data-group-id="1586865189-12">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="1586865189-12">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1586865189-13">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="1586865189-13">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1586865189-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1586865189-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="1586865189-15">[</span><span class="p" data-group-id="1586865189-16">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="1586865189-17">(</span><span class="n">Code</span><span class="p" data-group-id="1586865189-17">)</span><span class="p" data-group-id="1586865189-16">}</span><span class="p" data-group-id="1586865189-15">]</span><span class="p" data-group-id="1586865189-14">}</span><span class="p">.</span></code></pre><p>Another way to do it is through a convenience macro <code class="inline">?HANDLE_COMMON/0</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0066793635-1">(</span><span class="p" data-group-id="0066793635-2">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0066793635-2">]</span><span class="p" data-group-id="0066793635-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="9649490313-8">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="9649490313-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="9649490313-9">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9649490313-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">handle_common</span><span class="p" data-group-id="9649490313-10">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9649490313-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="9649490313-11">(</span><span class="p" data-group-id="9649490313-12">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="9649490313-12">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9649490313-13">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="9649490313-13">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9649490313-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9649490313-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="9649490313-15">[</span><span class="p" data-group-id="9649490313-16">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="9649490313-17">(</span><span class="n">Code</span><span class="p" data-group-id="9649490313-17">)</span><span class="p" data-group-id="9649490313-16">}</span><span class="p" data-group-id="9649490313-15">]</span><span class="p" data-group-id="9649490313-14">}</span><span class="p">.</span></code></pre><p>Another way to do it is through a convenience macro <code class="inline">?HANDLE_COMMON/0</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7072627570-1">(</span><span class="p" data-group-id="7072627570-2">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7072627570-2">]</span><span class="p" data-group-id="7072627570-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">code_length</span><span class="p" data-group-id="0066793635-3">(</span><span class="p" data-group-id="0066793635-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="0066793635-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="0066793635-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">code_length</span><span class="p" data-group-id="7072627570-3">(</span><span class="p" data-group-id="7072627570-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="7072627570-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="7072627570-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0066793635-5">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="0066793635-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="0066793635-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="0066793635-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="0066793635-7">)</span><span class="p" data-group-id="0066793635-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7072627570-5">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="7072627570-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="7072627570-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="7072627570-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="7072627570-7">)</span><span class="p" data-group-id="7072627570-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="0066793635-8">(</span><span class="p" data-group-id="0066793635-9">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="0066793635-9">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0066793635-10">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="0066793635-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0066793635-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0066793635-11">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="0066793635-12">[</span><span class="p" data-group-id="0066793635-13">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="0066793635-14">(</span><span class="n">Code</span><span class="p" data-group-id="0066793635-14">)</span><span class="p" data-group-id="0066793635-13">}</span><span class="p" data-group-id="0066793635-12">]</span><span class="p" data-group-id="0066793635-11">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="7072627570-8">(</span><span class="p" data-group-id="7072627570-9">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="7072627570-9">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7072627570-10">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="7072627570-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7072627570-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7072627570-11">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="7072627570-12">[</span><span class="p" data-group-id="7072627570-13">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="7072627570-14">(</span><span class="n">Code</span><span class="p" data-group-id="7072627570-14">)</span><span class="p" data-group-id="7072627570-13">}</span><span class="p" data-group-id="7072627570-12">]</span><span class="p" data-group-id="7072627570-11">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="0066793635-15">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0066793635-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="7072627570-15">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7072627570-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="0066793635-16">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0066793635-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="7072627570-16">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7072627570-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span></code></pre><p>This example uses <a href="../../../lib/stdlib/doc/html/gen_statem.html#call/2"><code class="inline">gen_statem:call/2</code></a>, which waits for a reply from the server.
│ │ │ │  The reply is sent with a <code class="inline">{reply, From, Reply}</code> tuple in an action list in the
│ │ │ │  <code class="inline">{keep_state, ...}</code> tuple that retains the current state. This return form is
│ │ │ │  convenient when you want to stay in the current state but do not know or care
│ │ │ │  about what it is.</p><p>If the common <em>state callback</em> needs to know the current state a function
│ │ │ │ -<code class="inline">handle_common/4</code> can be used instead:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6579859003-1">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="6579859003-2">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="6579859003-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="6579859003-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="6579859003-3">)</span><span class="p" data-group-id="6579859003-1">)</span><span class="p">.</span></code></pre><h2 id="one-state-callback" class="section-heading">
│ │ │ │ +<code class="inline">handle_common/4</code> can be used instead:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0689791712-1">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="0689791712-2">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="0689791712-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="0689791712-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="0689791712-3">)</span><span class="p" data-group-id="0689791712-1">)</span><span class="p">.</span></code></pre><h2 id="one-state-callback" class="section-heading">
│ │ │ │    <a href="#one-state-callback" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">One State Callback</span>
│ │ │ │  </h2>
│ │ │ │  <p>If <a href="#callback-modes"><em>callback mode</em></a> <code class="inline">handle_event_function</code> is used,
│ │ │ │  all events are handled in
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_statem.html#c:handle_event/4"><code class="inline">Module:handle_event/4</code></a> and we can
│ │ │ │  (but do not have to) use an event-centered approach where we first branch
│ │ │ │  depending on event and then depending on state:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8854590393-1">(</span><span class="p" data-group-id="8854590393-2">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="8854590393-2">]</span><span class="p" data-group-id="8854590393-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8245856943-1">(</span><span class="p" data-group-id="8245856943-2">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="8245856943-2">]</span><span class="p" data-group-id="8245856943-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="8854590393-3">(</span><span class="p" data-group-id="8854590393-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="8245856943-3">(</span><span class="p" data-group-id="8245856943-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">handle_event_function</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="8854590393-4">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8854590393-5">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="8854590393-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8854590393-6">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="8854590393-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8854590393-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8245856943-4">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8245856943-5">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="8245856943-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8245856943-6">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="8245856943-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8245856943-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │  	</span><span class="ss">locked</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="8854590393-7">#{</span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="8854590393-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="8245856943-7">#{</span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="8245856943-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │                  </span><span class="k">if</span><span class="w">
│ │ │ │ -                    </span><span class="nf">length</span><span class="p" data-group-id="8854590393-8">(</span><span class="n">Buttons</span><span class="p" data-group-id="8854590393-8">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                    </span><span class="nf">length</span><span class="p" data-group-id="8245856943-8">(</span><span class="n">Buttons</span><span class="p" data-group-id="8245856943-8">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                          </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │ │                      </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                        </span><span class="nf">tl</span><span class="p" data-group-id="8854590393-9">(</span><span class="n">Buttons</span><span class="p" data-group-id="8854590393-9">)</span><span class="w">
│ │ │ │ -                </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="8854590393-10">[</span><span class="n">Button</span><span class="p" data-group-id="8854590393-10">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                        </span><span class="nf">tl</span><span class="p" data-group-id="8245856943-9">(</span><span class="n">Buttons</span><span class="p" data-group-id="8245856943-9">)</span><span class="w">
│ │ │ │ +                </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="8245856943-10">[</span><span class="n">Button</span><span class="p" data-group-id="8245856943-10">]</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="k">if</span><span class="w">
│ │ │ │                  </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -                    </span><span class="nf">do_unlock</span><span class="p" data-group-id="8854590393-11">(</span><span class="p" data-group-id="8854590393-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="p" data-group-id="8854590393-12">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8854590393-13">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="8854590393-14">[</span><span class="p" data-group-id="8854590393-14">]</span><span class="p" data-group-id="8854590393-13">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                     </span><span class="p" data-group-id="8854590393-15">[</span><span class="p" data-group-id="8854590393-16">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="8854590393-16">}</span><span class="p" data-group-id="8854590393-15">]</span><span class="p" data-group-id="8854590393-12">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +                    </span><span class="nf">do_unlock</span><span class="p" data-group-id="8245856943-11">(</span><span class="p" data-group-id="8245856943-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="p" data-group-id="8245856943-12">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8245856943-13">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="8245856943-14">[</span><span class="p" data-group-id="8245856943-14">]</span><span class="p" data-group-id="8245856943-13">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                     </span><span class="p" data-group-id="8245856943-15">[</span><span class="p" data-group-id="8245856943-16">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="8245856943-16">}</span><span class="p" data-group-id="8245856943-15">]</span><span class="p" data-group-id="8245856943-12">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │                  </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ │ -                    </span><span class="p" data-group-id="8854590393-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8854590393-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="8854590393-18">}</span><span class="p" data-group-id="8854590393-17">}</span><span class="w">
│ │ │ │ +                    </span><span class="p" data-group-id="8245856943-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8245856943-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="8245856943-18">}</span><span class="p" data-group-id="8245856943-17">}</span><span class="w">
│ │ │ │              </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">open</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">keep_state_and_data</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="8854590393-19">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8854590393-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="8854590393-20">(</span><span class="p" data-group-id="8854590393-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8854590393-21">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8854590393-21">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="8854590393-22">(</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="8854590393-23">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="8854590393-23">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8854590393-24">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="8854590393-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8854590393-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8854590393-25">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="8854590393-26">[</span><span class="p" data-group-id="8854590393-27">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="8854590393-28">(</span><span class="n">Code</span><span class="p" data-group-id="8854590393-28">)</span><span class="p" data-group-id="8854590393-27">}</span><span class="p" data-group-id="8854590393-26">]</span><span class="p" data-group-id="8854590393-25">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8245856943-19">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8245856943-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="8245856943-20">(</span><span class="p" data-group-id="8245856943-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8245856943-21">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8245856943-21">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8245856943-22">(</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8245856943-23">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="8245856943-23">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8245856943-24">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="8245856943-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8245856943-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8245856943-25">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="8245856943-26">[</span><span class="p" data-group-id="8245856943-27">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="8245856943-28">(</span><span class="n">Code</span><span class="p" data-group-id="8245856943-28">)</span><span class="p" data-group-id="8245856943-27">}</span><span class="p" data-group-id="8245856943-26">]</span><span class="p" data-group-id="8245856943-25">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="stopping" class="section-heading">
│ │ │ │    <a href="#stopping" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Stopping</span>
│ │ │ │  </h2>
│ │ │ │ @@ -668,59 +668,59 @@
│ │ │ │  </h3>
│ │ │ │  <p>If the <code class="inline">gen_statem</code> is part of a supervision tree, no stop function is needed.
│ │ │ │  The <code class="inline">gen_statem</code> is automatically terminated by its supervisor. Exactly how
│ │ │ │  this is done is defined by a <a href="sup_princ.xhtml#shutdown">shutdown strategy</a>
│ │ │ │  set in the supervisor.</p><p>If it is necessary to clean up before termination, the shutdown strategy
│ │ │ │  must be a time-out value and the <code class="inline">gen_statem</code> must in function <code class="inline">init/1</code>
│ │ │ │  set itself to trap exit signals by calling
│ │ │ │ -<a href="../../../lib/../erts/doc/html/erlang.html#process_flag/2"><code class="inline">process_flag(trap_exit, true)</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="7923347259-1">(</span><span class="n">Args</span><span class="p" data-group-id="7923347259-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="7923347259-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="7923347259-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="7923347259-3">(</span><span class="p" data-group-id="7923347259-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +<a href="../../../lib/../erts/doc/html/erlang.html#process_flag/2"><code class="inline">process_flag(trap_exit, true)</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="2408116835-1">(</span><span class="n">Args</span><span class="p" data-group-id="2408116835-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="2408116835-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="2408116835-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="2408116835-3">(</span><span class="p" data-group-id="2408116835-3">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>When ordered to shut down, the <code class="inline">gen_statem</code> then calls callback function
│ │ │ │  <code class="inline">terminate(shutdown, State, Data)</code>.</p><p>In this example, function <code class="inline">terminate/3</code> locks the door if it is open,
│ │ │ │  so we do not accidentally leave the door open
│ │ │ │ -when the supervision tree terminates:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="3806688316-1">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="3806688316-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="3806688316-2">(</span><span class="p" data-group-id="3806688316-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +when the supervision tree terminates:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="7256212191-1">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="7256212191-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="7256212191-2">(</span><span class="p" data-group-id="7256212191-2">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><h3 id="standalone-gen_statem" class="section-heading">
│ │ │ │    <a href="#standalone-gen_statem" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Standalone gen_statem</span>
│ │ │ │  </h3>
│ │ │ │  <p>If the <code class="inline">gen_statem</code> is not part of a supervision tree, it can be stopped
│ │ │ │  using <a href="../../../lib/stdlib/doc/html/gen_statem.html#stop/1"><code class="inline">gen_statem:stop/1</code></a>, preferably through
│ │ │ │  an API function:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3859724440-1">(</span><span class="p" data-group-id="3859724440-2">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3859724440-2">]</span><span class="p" data-group-id="3859724440-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2617739641-1">(</span><span class="p" data-group-id="2617739641-2">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2617739641-2">]</span><span class="p" data-group-id="2617739641-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="3859724440-3">(</span><span class="p" data-group-id="3859724440-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="3859724440-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="3859724440-4">)</span><span class="p">.</span></code></pre><p>This makes the <code class="inline">gen_statem</code> call callback function <code class="inline">terminate/3</code> just like
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="2617739641-3">(</span><span class="p" data-group-id="2617739641-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="2617739641-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="2617739641-4">)</span><span class="p">.</span></code></pre><p>This makes the <code class="inline">gen_statem</code> call callback function <code class="inline">terminate/3</code> just like
│ │ │ │  for a supervised server and waits for the process to terminate.</p><h2 id="event-time-outs" class="section-heading">
│ │ │ │    <a href="#event-time-outs" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Event Time-Outs</span>
│ │ │ │  </h2>
│ │ │ │  <p>A time-out feature inherited from <code class="inline">gen_statem</code>'s predecessor <a href="../../../lib/stdlib/doc/html/gen_fsm.html"><code class="inline">gen_fsm</code></a>,
│ │ │ │  is an <em>event time-out</em>, that is, if an event arrives the timer is canceled.
│ │ │ │  You get either an event or a time-out, but not both.</p><p>It is ordered by the
│ │ │ │  <a href="#transition-actions"><em>transition action</em></a> <code class="inline">{timeout, Time, EventContent}</code>,
│ │ │ │  or just an integer <code class="inline">Time</code>, even without the enclosing actions list (the latter
│ │ │ │  is a form inherited from <code class="inline">gen_fsm</code>).</p><p>This type of time-out is useful, for example, to act on inactivity.
│ │ │ │  Let's restart the code sequence if no button is pressed for say 30 seconds:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="4213645228-1">(</span><span class="ss">timeout</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4213645228-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4213645228-2">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4213645228-3">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="4213645228-4">[</span><span class="p" data-group-id="4213645228-4">]</span><span class="p" data-group-id="4213645228-3">}</span><span class="p" data-group-id="4213645228-2">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="4213645228-5">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4213645228-6">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="4213645228-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="4213645228-7">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="4213645228-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4213645228-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="2518746149-1">(</span><span class="ss">timeout</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2518746149-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2518746149-2">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2518746149-3">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="2518746149-4">[</span><span class="p" data-group-id="2518746149-4">]</span><span class="p" data-group-id="2518746149-3">}</span><span class="p" data-group-id="2518746149-2">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="2518746149-5">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2518746149-6">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2518746149-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="2518746149-7">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="2518746149-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2518746149-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="4213645228-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4213645228-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="4213645228-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p" data-group-id="4213645228-8">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="2518746149-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2518746149-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="2518746149-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p" data-group-id="2518746149-8">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Whenever we receive a button event we start an <em>event time-out</em> of 30 seconds,
│ │ │ │  and if we get an <em>event type</em> of <code class="inline">timeout</code> we reset the remaining
│ │ │ │  code sequence.</p><p>An <em>event time-out</em> is canceled by any other event so you either get
│ │ │ │  some other event or the time-out event. Therefore, canceling,
│ │ │ │  restarting, or updating an <em>event time-out</em> is neither possible nor
│ │ │ │  necessary. Whatever event you act on has already canceled
│ │ │ │  the <em>event time-out</em>, so there is never a running <em>event time-out</em>
│ │ │ │ @@ -739,30 +739,30 @@
│ │ │ │  another, maybe cancel the time-out without changing states, or perhaps run
│ │ │ │  multiple time-outs in parallel. All this can be accomplished with
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_statem.html#t:generic_timeout/0"><em>generic time-outs</em></a>. They may look a little
│ │ │ │  bit like <a href="../../../lib/stdlib/doc/html/gen_statem.html#t:event_timeout/0"><em>event time-outs</em></a> but contain
│ │ │ │  a name to allow for any number of them simultaneously and they are
│ │ │ │  not automatically canceled.</p><p>Here is how to accomplish the <em>state time-out</em> in the previous example
│ │ │ │  by instead using a <em>generic time-out</em> named for example <code class="inline">open</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="7360631968-1">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7360631968-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7360631968-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="7360631968-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="7360631968-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7360631968-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="0324592172-1">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0324592172-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0324592172-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0324592172-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="0324592172-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0324592172-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="7360631968-4">(</span><span class="p" data-group-id="7360631968-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="7360631968-5">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7360631968-6">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="7360631968-7">[</span><span class="p" data-group-id="7360631968-7">]</span><span class="p" data-group-id="7360631968-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="7360631968-8">[</span><span class="p" data-group-id="7360631968-9">{</span><span class="p" data-group-id="7360631968-10">{</span><span class="ss">timeout</span><span class="p">,</span><span class="ss">open</span><span class="p" data-group-id="7360631968-10">}</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="7360631968-9">}</span><span class="p" data-group-id="7360631968-8">]</span><span class="p" data-group-id="7360631968-5">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="0324592172-4">(</span><span class="p" data-group-id="0324592172-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="0324592172-5">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0324592172-6">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="0324592172-7">[</span><span class="p" data-group-id="0324592172-7">]</span><span class="p" data-group-id="0324592172-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="0324592172-8">[</span><span class="p" data-group-id="0324592172-9">{</span><span class="p" data-group-id="0324592172-10">{</span><span class="ss">timeout</span><span class="p">,</span><span class="ss">open</span><span class="p" data-group-id="0324592172-10">}</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="0324592172-9">}</span><span class="p" data-group-id="0324592172-8">]</span><span class="p" data-group-id="0324592172-5">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="7360631968-11">(</span><span class="p" data-group-id="7360631968-12">{</span><span class="ss">timeout</span><span class="p">,</span><span class="ss">open</span><span class="p" data-group-id="7360631968-12">}</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7360631968-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="7360631968-13">(</span><span class="p" data-group-id="7360631968-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7360631968-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="ss">locked</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="7360631968-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="7360631968-15">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7360631968-16">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="7360631968-16">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7360631968-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7360631968-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="7360631968-17">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="0324592172-11">(</span><span class="p" data-group-id="0324592172-12">{</span><span class="ss">timeout</span><span class="p">,</span><span class="ss">open</span><span class="p" data-group-id="0324592172-12">}</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0324592172-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="0324592172-13">(</span><span class="p" data-group-id="0324592172-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0324592172-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="ss">locked</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="0324592172-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="0324592172-15">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0324592172-16">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0324592172-16">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0324592172-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0324592172-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="0324592172-17">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Specific <em>generic time-outs</em> can just as <a href="#state-time-outs"><em>state time-outs</em></a>
│ │ │ │  be restarted or canceled by setting it to a new time or <code class="inline">infinity</code>.</p><p>In this particular case we do not need to cancel the time-out since
│ │ │ │  the time-out event is the only possible reason to do a <em>state change</em>
│ │ │ │  from <code class="inline">open</code> to <code class="inline">locked</code>.</p><p>Instead of bothering with when to cancel a time-out, a late time-out event
│ │ │ │  can be handled by ignoring it if it arrives in a state
│ │ │ │  where it is known to be late.</p><p>You can restart, cancel, or update a <em>generic time-out</em>.
│ │ │ │  See section <a href="#time-outs"><em>Time-Outs</em></a> for details.</p><h2 id="erlang-timers" class="section-heading">
│ │ │ │ @@ -774,32 +774,32 @@
│ │ │ │  <p>The most versatile way to handle time-outs is to use Erlang Timers; see
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#start_timer/4"><code class="inline">erlang:start_timer/3,4</code></a>. Most time-out tasks
│ │ │ │  can be performed with the time-out features in <a href="../../../lib/stdlib/doc/html/gen_statem.html"><code class="inline">gen_statem</code></a>,
│ │ │ │  but an example of one that cannot is if you should need the return value
│ │ │ │  from <a href="../../../lib/../erts/doc/html/erlang.html#cancel_timer/2"><code class="inline">erlang:cancel_timer(Tref)</code></a>, that is,
│ │ │ │  the remaining time of the timer.</p><p>Here is how to accomplish the <em>state time-out</em> in the previous example
│ │ │ │  by instead using an Erlang Timer:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="5210200014-1">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5210200014-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5210200014-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="5210200014-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="5210200014-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5210200014-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="3720994782-1">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3720994782-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3720994782-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="3720994782-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="3720994782-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3720994782-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="5210200014-4">(</span><span class="p" data-group-id="5210200014-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="3720994782-4">(</span><span class="p" data-group-id="3720994782-4">)</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="n">Tref</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │ -                 </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">start_timer</span><span class="p" data-group-id="5210200014-5">(</span><span class="w">
│ │ │ │ -                     </span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5210200014-6">(</span><span class="p" data-group-id="5210200014-6">)</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p" data-group-id="5210200014-5">)</span><span class="p">,</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="5210200014-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5210200014-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="5210200014-9">[</span><span class="p" data-group-id="5210200014-9">]</span><span class="p">,</span><span class="w"> </span><span class="ss">timer</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Tref</span><span class="p" data-group-id="5210200014-8">}</span><span class="p" data-group-id="5210200014-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +                 </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">start_timer</span><span class="p" data-group-id="3720994782-5">(</span><span class="w">
│ │ │ │ +                     </span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3720994782-6">(</span><span class="p" data-group-id="3720994782-6">)</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p" data-group-id="3720994782-5">)</span><span class="p">,</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="3720994782-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3720994782-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="3720994782-9">[</span><span class="p" data-group-id="3720994782-9">]</span><span class="p">,</span><span class="w"> </span><span class="ss">timer</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Tref</span><span class="p" data-group-id="3720994782-8">}</span><span class="p" data-group-id="3720994782-7">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="5210200014-10">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5210200014-11">{</span><span class="ss">timeout</span><span class="p">,</span><span class="n">Tref</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="5210200014-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5210200014-12">#{</span><span class="ss">timer</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Tref</span><span class="p" data-group-id="5210200014-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5210200014-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="5210200014-13">(</span><span class="p" data-group-id="5210200014-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5210200014-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="ss">locked</span><span class="p">,</span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="5210200014-15">(</span><span class="ss">timer</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5210200014-15">)</span><span class="p" data-group-id="5210200014-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="5210200014-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5210200014-17">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5210200014-17">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5210200014-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5210200014-18">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="5210200014-18">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="3720994782-10">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3720994782-11">{</span><span class="ss">timeout</span><span class="p">,</span><span class="n">Tref</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="3720994782-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3720994782-12">#{</span><span class="ss">timer</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Tref</span><span class="p" data-group-id="3720994782-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3720994782-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="3720994782-13">(</span><span class="p" data-group-id="3720994782-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3720994782-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="ss">locked</span><span class="p">,</span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="3720994782-15">(</span><span class="ss">timer</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3720994782-15">)</span><span class="p" data-group-id="3720994782-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="3720994782-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3720994782-17">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="3720994782-17">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3720994782-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3720994782-18">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="3720994782-18">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Removing the <code class="inline">timer</code> key from the map when we do a <em>state change</em> to <code class="inline">locked</code>
│ │ │ │  is not strictly necessary since we can only get into state <code class="inline">open</code>
│ │ │ │  with an updated <code class="inline">timer</code> map value. But it can be nice to not have
│ │ │ │  outdated values in the state <code class="inline">Data</code>.</p><p>If you need to cancel a timer because of some other event, you can use
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#cancel_timer/2"><code class="inline">erlang:cancel_timer(Tref)</code></a>. Note that no time-out
│ │ │ │  message will arrive after this (because the timer has been
│ │ │ │  explicitly canceled), unless you have already postponed one earlier
│ │ │ │ @@ -815,16 +815,16 @@
│ │ │ │    <span class="text">Postponing Events</span>
│ │ │ │  </h2>
│ │ │ │  <p>If you want to ignore a particular event in the current state and handle it
│ │ │ │  in a future state, you can postpone the event. A postponed event
│ │ │ │  is retried after a <em>state change</em>, that is, <code class="inline">OldState =/= NewState</code>.</p><p>Postponing is ordered by the
│ │ │ │  <a href="#transition-actions"><em>transition action</em></a> <code class="inline">postpone</code>.</p><p>In this example, instead of ignoring button events while in the <code class="inline">open</code> state,
│ │ │ │  we can postpone them and handle them later in the <code class="inline">locked</code> state:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="0590976012-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0590976012-2">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0590976012-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0590976012-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0590976012-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p">,</span><span class="p" data-group-id="0590976012-4">[</span><span class="ss">postpone</span><span class="p" data-group-id="0590976012-4">]</span><span class="p" data-group-id="0590976012-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="3836828818-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3836828818-2">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="3836828818-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3836828818-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3836828818-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p">,</span><span class="p" data-group-id="3836828818-4">[</span><span class="ss">postpone</span><span class="p" data-group-id="3836828818-4">]</span><span class="p" data-group-id="3836828818-3">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Since a postponed event is only retried after a <em>state change</em>, you have to
│ │ │ │  think about where to keep a state data item. You can keep it in the server
│ │ │ │  <code class="inline">Data</code> or in the <code class="inline">State</code> itself, for example by having two more or less
│ │ │ │  identical states to keep a boolean value, or by using a complex state (see
│ │ │ │  section <a href="#complex-state"><em>Complex State</em></a>) with
│ │ │ │  <a href="#callback-modes"><em>callback mode</em></a>
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_statem.html#t:callback_mode/0"><code class="inline">handle_event_function</code></a>. If a change
│ │ │ │ @@ -845,55 +845,55 @@
│ │ │ │    <a href="#selective-receive" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Selective Receive</span>
│ │ │ │  </h3>
│ │ │ │  <p>Erlang's selective <code class="inline">receive</code> statement is often used to describe simple state
│ │ │ │  machine examples in straightforward Erlang code. The following is a possible
│ │ │ │ -implementation of the first example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9854851556-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="9854851556-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9854851556-2">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_1</span><span class="p" data-group-id="9854851556-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9854851556-3">(</span><span class="p" data-group-id="9854851556-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9854851556-4">]</span><span class="p" data-group-id="9854851556-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="9854851556-5">(</span><span class="n">Code</span><span class="p" data-group-id="9854851556-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="9854851556-6">(</span><span class="w">
│ │ │ │ -      </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="9854851556-7">(</span><span class="p" data-group-id="9854851556-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	      </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">register</span><span class="p" data-group-id="9854851556-8">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9854851556-9">(</span><span class="p" data-group-id="9854851556-9">)</span><span class="p" data-group-id="9854851556-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ -	      </span><span class="nf">do_lock</span><span class="p" data-group-id="9854851556-10">(</span><span class="p" data-group-id="9854851556-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -	      </span><span class="nf">locked</span><span class="p" data-group-id="9854851556-11">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="9854851556-12">(</span><span class="n">Code</span><span class="p" data-group-id="9854851556-12">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9854851556-13">[</span><span class="p" data-group-id="9854851556-13">]</span><span class="p" data-group-id="9854851556-11">)</span><span class="w">
│ │ │ │ -      </span><span class="k">end</span><span class="p" data-group-id="9854851556-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +implementation of the first example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8942439046-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="8942439046-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8942439046-2">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_1</span><span class="p" data-group-id="8942439046-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8942439046-3">(</span><span class="p" data-group-id="8942439046-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8942439046-4">]</span><span class="p" data-group-id="8942439046-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="8942439046-5">(</span><span class="n">Code</span><span class="p" data-group-id="8942439046-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="8942439046-6">(</span><span class="w">
│ │ │ │ +      </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8942439046-7">(</span><span class="p" data-group-id="8942439046-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	      </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">register</span><span class="p" data-group-id="8942439046-8">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8942439046-9">(</span><span class="p" data-group-id="8942439046-9">)</span><span class="p" data-group-id="8942439046-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +	      </span><span class="nf">do_lock</span><span class="p" data-group-id="8942439046-10">(</span><span class="p" data-group-id="8942439046-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +	      </span><span class="nf">locked</span><span class="p" data-group-id="8942439046-11">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="8942439046-12">(</span><span class="n">Code</span><span class="p" data-group-id="8942439046-12">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8942439046-13">[</span><span class="p" data-group-id="8942439046-13">]</span><span class="p" data-group-id="8942439046-11">)</span><span class="w">
│ │ │ │ +      </span><span class="k">end</span><span class="p" data-group-id="8942439046-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">button</span><span class="p" data-group-id="9854851556-14">(</span><span class="n">Button</span><span class="p" data-group-id="9854851556-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="o">?</span><span class="n">NAME</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9854851556-15">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9854851556-15">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="6911474107-1">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="6911474107-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">button</span><span class="p" data-group-id="8942439046-14">(</span><span class="n">Button</span><span class="p" data-group-id="8942439046-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="o">?</span><span class="n">NAME</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8942439046-15">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="8942439046-15">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="9703386289-1">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="9703386289-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6911474107-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6911474107-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9703386289-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9703386289-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │                  </span><span class="k">if</span><span class="w">
│ │ │ │ -                    </span><span class="nf">length</span><span class="p" data-group-id="6911474107-3">(</span><span class="n">Buttons</span><span class="p" data-group-id="6911474107-3">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                    </span><span class="nf">length</span><span class="p" data-group-id="9703386289-3">(</span><span class="n">Buttons</span><span class="p" data-group-id="9703386289-3">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                          </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │ │                      </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                        </span><span class="nf">tl</span><span class="p" data-group-id="6911474107-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="6911474107-4">)</span><span class="w">
│ │ │ │ -                </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="6911474107-5">[</span><span class="n">Button</span><span class="p" data-group-id="6911474107-5">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                        </span><span class="nf">tl</span><span class="p" data-group-id="9703386289-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="9703386289-4">)</span><span class="w">
│ │ │ │ +                </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="9703386289-5">[</span><span class="n">Button</span><span class="p" data-group-id="9703386289-5">]</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="k">if</span><span class="w">
│ │ │ │                  </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -                    </span><span class="nf">do_unlock</span><span class="p" data-group-id="6911474107-6">(</span><span class="p" data-group-id="6911474107-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ -		    </span><span class="nf">open</span><span class="p" data-group-id="6911474107-7">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="6911474107-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ +                    </span><span class="nf">do_unlock</span><span class="p" data-group-id="9703386289-6">(</span><span class="p" data-group-id="9703386289-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +		    </span><span class="nf">open</span><span class="p" data-group-id="9703386289-7">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="9703386289-7">)</span><span class="p">;</span><span class="w">
│ │ │ │                  </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ │ -                    </span><span class="nf">locked</span><span class="p" data-group-id="6911474107-8">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="6911474107-8">)</span><span class="w">
│ │ │ │ +                    </span><span class="nf">locked</span><span class="p" data-group-id="9703386289-8">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="9703386289-8">)</span><span class="w">
│ │ │ │              </span><span class="k">end</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="4483984620-1">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="4483984620-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="3994487275-1">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="3994487275-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ -	    </span><span class="nf">do_lock</span><span class="p" data-group-id="4483984620-2">(</span><span class="p" data-group-id="4483984620-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -	    </span><span class="nf">locked</span><span class="p" data-group-id="4483984620-3">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4483984620-4">[</span><span class="p" data-group-id="4483984620-4">]</span><span class="p" data-group-id="4483984620-3">)</span><span class="w">
│ │ │ │ +	    </span><span class="nf">do_lock</span><span class="p" data-group-id="3994487275-2">(</span><span class="p" data-group-id="3994487275-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +	    </span><span class="nf">locked</span><span class="p" data-group-id="3994487275-3">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3994487275-4">[</span><span class="p" data-group-id="3994487275-4">]</span><span class="p" data-group-id="3994487275-3">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">do_lock</span><span class="p" data-group-id="4483984620-5">(</span><span class="p" data-group-id="4483984620-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4483984620-6">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4483984620-7">[</span><span class="p" data-group-id="4483984620-7">]</span><span class="p" data-group-id="4483984620-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">do_unlock</span><span class="p" data-group-id="4483984620-8">(</span><span class="p" data-group-id="4483984620-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4483984620-9">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4483984620-10">[</span><span class="p" data-group-id="4483984620-10">]</span><span class="p" data-group-id="4483984620-9">)</span><span class="p">.</span></code></pre><p>The selective receive in this case causes <code class="inline">open</code> to implicitly postpone any
│ │ │ │ +</span><span class="nf">do_lock</span><span class="p" data-group-id="3994487275-5">(</span><span class="p" data-group-id="3994487275-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3994487275-6">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3994487275-7">[</span><span class="p" data-group-id="3994487275-7">]</span><span class="p" data-group-id="3994487275-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">do_unlock</span><span class="p" data-group-id="3994487275-8">(</span><span class="p" data-group-id="3994487275-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3994487275-9">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3994487275-10">[</span><span class="p" data-group-id="3994487275-10">]</span><span class="p" data-group-id="3994487275-9">)</span><span class="p">.</span></code></pre><p>The selective receive in this case causes <code class="inline">open</code> to implicitly postpone any
│ │ │ │  events to the <code class="inline">locked</code> state.</p><p>A catch-all receive should never be used from a <code class="inline">gen_statem</code> behaviour
│ │ │ │  (or from any <code class="inline">gen_*</code> behaviour), as the receive statement is within
│ │ │ │  the <code class="inline">gen_*</code> engine itself. <a href="../../../lib/stdlib/doc/html/sys.html"><code class="inline">sys</code></a>-compatible behaviours must respond to
│ │ │ │  system messages and therefore do that in their engine receive loop,
│ │ │ │  passing non-system messages to the <em>callback module</em>. Using a catch-all
│ │ │ │  receive can result in system messages being discarded, which in turn
│ │ │ │  can lead to unexpected behaviour. If a selective receive must be used,
│ │ │ │ @@ -916,40 +916,40 @@
│ │ │ │  section), especially if only one or a few states have state enter actions,
│ │ │ │  this is a perfect use case for the built in
│ │ │ │  <a href="#state-enter-calls"><em>state enter calls</em></a>.</p><p>You return a list containing <code class="inline">state_enter</code> from your
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_statem.html#c:callback_mode/0"><code class="inline">callback_mode/0</code></a> function and the
│ │ │ │  <code class="inline">gen_statem</code> engine will call your <em>state callback</em> once with an event
│ │ │ │  <code class="inline">(enter, OldState, ...)</code> whenever it does a <em>state change</em>. Then you
│ │ │ │  just need to handle these event-like calls in all states.</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="9395497873-1">(</span><span class="n">Code</span><span class="p" data-group-id="9395497873-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="9395497873-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="9395497873-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9395497873-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="9395497873-4">(</span><span class="n">Code</span><span class="p" data-group-id="9395497873-4">)</span><span class="p" data-group-id="9395497873-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9395497873-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9395497873-5">}</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="9395497873-6">(</span><span class="p" data-group-id="9395497873-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9395497873-7">[</span><span class="ss">state_functions</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="9395497873-7">]</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="9395497873-8">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9395497873-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="9395497873-9">(</span><span class="p" data-group-id="9395497873-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9395497873-10">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="9395497873-11">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9395497873-12">[</span><span class="p" data-group-id="9395497873-12">]</span><span class="p" data-group-id="9395497873-11">}</span><span class="p" data-group-id="9395497873-10">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="9395497873-13">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9395497873-14">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9395497873-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="9395497873-15">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="9395497873-15">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9395497873-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="1495887083-1">(</span><span class="n">Code</span><span class="p" data-group-id="1495887083-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="1495887083-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="1495887083-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1495887083-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="1495887083-4">(</span><span class="n">Code</span><span class="p" data-group-id="1495887083-4">)</span><span class="p" data-group-id="1495887083-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1495887083-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1495887083-5">}</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="1495887083-6">(</span><span class="p" data-group-id="1495887083-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1495887083-7">[</span><span class="ss">state_functions</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="1495887083-7">]</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="1495887083-8">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1495887083-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="1495887083-9">(</span><span class="p" data-group-id="1495887083-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1495887083-10">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="1495887083-11">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1495887083-12">[</span><span class="p" data-group-id="1495887083-12">]</span><span class="p" data-group-id="1495887083-11">}</span><span class="p" data-group-id="1495887083-10">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="1495887083-13">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1495887083-14">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1495887083-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="1495887083-15">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="1495887083-15">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1495887083-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="9395497873-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9395497873-16">}</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="1495887083-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1495887083-16">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="9395497873-17">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="9395497873-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="9395497873-18">(</span><span class="p" data-group-id="9395497873-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9395497873-19">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="9395497873-20">[</span><span class="p" data-group-id="9395497873-21">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="9395497873-21">}</span><span class="p" data-group-id="9395497873-20">]</span><span class="p" data-group-id="9395497873-19">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="9395497873-22">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9395497873-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9395497873-23">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9395497873-23">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="1495887083-17">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="1495887083-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="1495887083-18">(</span><span class="p" data-group-id="1495887083-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1495887083-19">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="1495887083-20">[</span><span class="p" data-group-id="1495887083-21">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="1495887083-21">}</span><span class="p" data-group-id="1495887083-20">]</span><span class="p" data-group-id="1495887083-19">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="1495887083-22">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1495887083-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1495887083-23">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1495887083-23">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>You can repeat the state enter code by returning one of
│ │ │ │  <code class="inline">{repeat_state, ...}</code>,<code class="inline">{repeat_state_and_data, _}</code>,
│ │ │ │  or <code class="inline">repeat_state_and_data</code> that otherwise behaves exactly like their
│ │ │ │  <code class="inline">keep_state</code> siblings.  See the type
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_statem.html#t:state_callback_result/2"><code class="inline">state_callback_result()</code></a>
│ │ │ │  in the Reference Manual.</p><h2 id="inserted-events" class="section-heading">
│ │ │ │    <a href="#inserted-events" class="hover-link">
│ │ │ │ @@ -971,44 +971,44 @@
│ │ │ │  to dispatch pre-processed events as internal events to the main state
│ │ │ │  machine.</p><p>Using internal events also can make it easier to synchronize the state
│ │ │ │  machines.</p><p>A variant of this is to use a <a href="#complex-state">complex state</a> with
│ │ │ │  <a href="#one-state-callback">one state callback</a>, modeling the state
│ │ │ │  with, for example, a tuple <code class="inline">{MainFSMState, SubFSMState}</code>.</p><p>To illustrate this we make up an example where the buttons instead generate
│ │ │ │  down and up (press and release) events, and the lock responds
│ │ │ │  to an up event only after the corresponding down event.</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9786068272-1">(</span><span class="p" data-group-id="9786068272-2">[</span><span class="ss">down</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">up</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9786068272-2">]</span><span class="p" data-group-id="9786068272-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3750383051-1">(</span><span class="p" data-group-id="3750383051-2">[</span><span class="ss">down</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">up</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3750383051-2">]</span><span class="p" data-group-id="3750383051-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">down</span><span class="p" data-group-id="9786068272-3">(</span><span class="n">Button</span><span class="p" data-group-id="9786068272-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="9786068272-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9786068272-5">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9786068272-5">}</span><span class="p" data-group-id="9786068272-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">down</span><span class="p" data-group-id="3750383051-3">(</span><span class="n">Button</span><span class="p" data-group-id="3750383051-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="3750383051-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3750383051-5">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3750383051-5">}</span><span class="p" data-group-id="3750383051-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">up</span><span class="p" data-group-id="9786068272-6">(</span><span class="n">Button</span><span class="p" data-group-id="9786068272-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="9786068272-7">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9786068272-8">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9786068272-8">}</span><span class="p" data-group-id="9786068272-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">up</span><span class="p" data-group-id="3750383051-6">(</span><span class="n">Button</span><span class="p" data-group-id="3750383051-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="3750383051-7">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3750383051-8">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3750383051-8">}</span><span class="p" data-group-id="3750383051-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="9786068272-9">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9786068272-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="9786068272-10">(</span><span class="p" data-group-id="9786068272-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9786068272-11">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="9786068272-12">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9786068272-13">[</span><span class="p" data-group-id="9786068272-13">]</span><span class="p" data-group-id="9786068272-12">}</span><span class="p" data-group-id="9786068272-11">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="9786068272-14">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9786068272-15">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9786068272-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="9786068272-16">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="9786068272-16">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9786068272-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">handle_common</span><span class="p" data-group-id="5346481322-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5346481322-2">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5346481322-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5346481322-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5346481322-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5346481322-4">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="5346481322-4">}</span><span class="p" data-group-id="5346481322-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="5346481322-5">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5346481322-6">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5346481322-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5346481322-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="3750383051-9">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3750383051-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="3750383051-10">(</span><span class="p" data-group-id="3750383051-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3750383051-11">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="3750383051-12">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3750383051-13">[</span><span class="p" data-group-id="3750383051-13">]</span><span class="p" data-group-id="3750383051-12">}</span><span class="p" data-group-id="3750383051-11">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="3750383051-14">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3750383051-15">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3750383051-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="3750383051-16">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="3750383051-16">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3750383051-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">handle_common</span><span class="p" data-group-id="0358342013-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0358342013-2">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0358342013-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0358342013-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0358342013-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0358342013-4">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="0358342013-4">}</span><span class="p" data-group-id="0358342013-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="0358342013-5">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0358342013-6">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0358342013-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0358342013-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Data</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="5346481322-7">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="5346481322-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="5346481322-8">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="5346481322-9">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5346481322-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="5346481322-10">[</span><span class="p" data-group-id="5346481322-11">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="5346481322-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5346481322-12">}</span><span class="p" data-group-id="5346481322-11">}</span><span class="p" data-group-id="5346481322-10">]</span><span class="p" data-group-id="5346481322-8">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="5346481322-13">#{</span><span class="p" data-group-id="5346481322-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0358342013-7">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="0358342013-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="0358342013-8">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="0358342013-9">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0358342013-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="0358342013-10">[</span><span class="p" data-group-id="0358342013-11">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="0358342013-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0358342013-12">}</span><span class="p" data-group-id="0358342013-11">}</span><span class="p" data-group-id="0358342013-10">]</span><span class="p" data-group-id="0358342013-8">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0358342013-13">#{</span><span class="p" data-group-id="0358342013-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">keep_state_and_data</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="5346481322-14">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5346481322-15">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5346481322-15">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5346481322-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5346481322-16">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p">,</span><span class="p" data-group-id="5346481322-17">[</span><span class="ss">postpone</span><span class="p" data-group-id="5346481322-17">]</span><span class="p" data-group-id="5346481322-16">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="0358342013-14">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0358342013-15">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0358342013-15">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0358342013-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0358342013-16">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p">,</span><span class="p" data-group-id="0358342013-17">[</span><span class="ss">postpone</span><span class="p" data-group-id="0358342013-17">]</span><span class="p" data-group-id="0358342013-16">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>If you start this program with <code class="inline">code_lock:start([17])</code> you can unlock with
│ │ │ │  <code class="inline">code_lock:down(17), code_lock:up(17).</code></p><h2 id="example-revisited" class="section-heading">
│ │ │ │    <a href="#example-revisited" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Example Revisited</span>
│ │ │ │  </h2>
│ │ │ │ @@ -1036,152 +1036,152 @@
│ │ │ │  Also, the state diagram does not show that the <code class="inline">code_length/0</code> call
│ │ │ │  must be handled in every state.</p><h3 id="callback-mode-state_functions" class="section-heading">
│ │ │ │    <a href="#callback-mode-state_functions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Callback Mode: state_functions</span>
│ │ │ │  </h3>
│ │ │ │ -<p>Using state functions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7366827135-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="7366827135-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="7366827135-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="7366827135-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7366827135-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_2</span><span class="p" data-group-id="7366827135-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>Using state functions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7692613265-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="7692613265-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="7692613265-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="7692613265-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7692613265-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_2</span><span class="p" data-group-id="7692613265-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7366827135-4">(</span><span class="p" data-group-id="7366827135-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7366827135-5">]</span><span class="p" data-group-id="7366827135-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7366827135-6">(</span><span class="p" data-group-id="7366827135-7">[</span><span class="ss">down</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">up</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7366827135-7">]</span><span class="p" data-group-id="7366827135-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7366827135-8">(</span><span class="p" data-group-id="7366827135-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="7366827135-9">]</span><span class="p" data-group-id="7366827135-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7366827135-10">(</span><span class="p" data-group-id="7366827135-11">[</span><span class="ss">locked</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">open</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="7366827135-11">]</span><span class="p" data-group-id="7366827135-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="7366827135-12">(</span><span class="n">Code</span><span class="p" data-group-id="7366827135-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="7366827135-13">(</span><span class="p" data-group-id="7366827135-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="7366827135-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7366827135-15">[</span><span class="p" data-group-id="7366827135-15">]</span><span class="p" data-group-id="7366827135-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="7366827135-16">(</span><span class="p" data-group-id="7366827135-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="7366827135-17">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="7366827135-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">down</span><span class="p" data-group-id="7366827135-18">(</span><span class="n">Button</span><span class="p" data-group-id="7366827135-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="7366827135-19">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7366827135-20">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7366827135-20">}</span><span class="p" data-group-id="7366827135-19">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">up</span><span class="p" data-group-id="7366827135-21">(</span><span class="n">Button</span><span class="p" data-group-id="7366827135-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="7366827135-22">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7366827135-23">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7366827135-23">}</span><span class="p" data-group-id="7366827135-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">code_length</span><span class="p" data-group-id="7366827135-24">(</span><span class="p" data-group-id="7366827135-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="7366827135-25">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="7366827135-25">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="7254832101-1">(</span><span class="n">Code</span><span class="p" data-group-id="7254832101-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="7254832101-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="7254832101-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7254832101-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="7254832101-4">(</span><span class="n">Code</span><span class="p" data-group-id="7254832101-4">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7254832101-5">[</span><span class="p" data-group-id="7254832101-5">]</span><span class="p" data-group-id="7254832101-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7254832101-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7254832101-6">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7692613265-4">(</span><span class="p" data-group-id="7692613265-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7692613265-5">]</span><span class="p" data-group-id="7692613265-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7692613265-6">(</span><span class="p" data-group-id="7692613265-7">[</span><span class="ss">down</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">up</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7692613265-7">]</span><span class="p" data-group-id="7692613265-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7692613265-8">(</span><span class="p" data-group-id="7692613265-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="7692613265-9">]</span><span class="p" data-group-id="7692613265-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7692613265-10">(</span><span class="p" data-group-id="7692613265-11">[</span><span class="ss">locked</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">open</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="7692613265-11">]</span><span class="p" data-group-id="7692613265-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="7692613265-12">(</span><span class="n">Code</span><span class="p" data-group-id="7692613265-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="7692613265-13">(</span><span class="p" data-group-id="7692613265-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="7692613265-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7692613265-15">[</span><span class="p" data-group-id="7692613265-15">]</span><span class="p" data-group-id="7692613265-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="7692613265-16">(</span><span class="p" data-group-id="7692613265-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="7692613265-17">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="7692613265-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">down</span><span class="p" data-group-id="7692613265-18">(</span><span class="n">Button</span><span class="p" data-group-id="7692613265-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="7692613265-19">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7692613265-20">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7692613265-20">}</span><span class="p" data-group-id="7692613265-19">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">up</span><span class="p" data-group-id="7692613265-21">(</span><span class="n">Button</span><span class="p" data-group-id="7692613265-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="7692613265-22">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7692613265-23">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7692613265-23">}</span><span class="p" data-group-id="7692613265-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">code_length</span><span class="p" data-group-id="7692613265-24">(</span><span class="p" data-group-id="7692613265-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="7692613265-25">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="7692613265-25">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="9645393351-1">(</span><span class="n">Code</span><span class="p" data-group-id="9645393351-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="9645393351-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="9645393351-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9645393351-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="9645393351-4">(</span><span class="n">Code</span><span class="p" data-group-id="9645393351-4">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9645393351-5">[</span><span class="p" data-group-id="9645393351-5">]</span><span class="p" data-group-id="9645393351-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9645393351-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9645393351-6">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="7254832101-7">(</span><span class="p" data-group-id="7254832101-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7254832101-8">[</span><span class="ss">state_functions</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="7254832101-8">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="9645393351-7">(</span><span class="p" data-group-id="9645393351-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9645393351-8">[</span><span class="ss">state_functions</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="9645393351-8">]</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7254832101-9">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="7254832101-10">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="7254832101-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="7254832101-11">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="7254832101-11">)</span><span class="p" data-group-id="7254832101-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9645393351-9">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="9645393351-10">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="9645393351-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="9645393351-11">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="9645393351-11">)</span><span class="p" data-group-id="9645393351-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="7254832101-12">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7254832101-13">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7254832101-13">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7254832101-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7254832101-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7254832101-15">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="7254832101-15">}</span><span class="p" data-group-id="7254832101-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="7254832101-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7254832101-17">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7254832101-17">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7254832101-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="9645393351-12">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9645393351-13">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9645393351-13">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9645393351-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9645393351-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9645393351-15">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="9645393351-15">}</span><span class="p" data-group-id="9645393351-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="9645393351-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9645393351-17">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9645393351-17">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9645393351-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Data</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="7254832101-18">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="7254832101-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="7254832101-19">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="7254832101-20">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7254832101-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="7254832101-21">[</span><span class="p" data-group-id="7254832101-22">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="7254832101-23">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7254832101-23">}</span><span class="p" data-group-id="7254832101-22">}</span><span class="p" data-group-id="7254832101-21">]</span><span class="p" data-group-id="7254832101-19">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="7254832101-24">#{</span><span class="p" data-group-id="7254832101-24">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9645393351-18">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="9645393351-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="9645393351-19">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="9645393351-20">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9645393351-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="9645393351-21">[</span><span class="p" data-group-id="9645393351-22">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="9645393351-23">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9645393351-23">}</span><span class="p" data-group-id="9645393351-22">}</span><span class="p" data-group-id="9645393351-21">]</span><span class="p" data-group-id="9645393351-19">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9645393351-24">#{</span><span class="p" data-group-id="9645393351-24">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">keep_state_and_data</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="7254832101-25">(</span><span class="p" data-group-id="7254832101-26">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="7254832101-26">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7254832101-27">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="7254832101-27">}</span><span class="p" data-group-id="7254832101-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7254832101-28">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="7254832101-29">[</span><span class="p" data-group-id="7254832101-30">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="7254832101-31">(</span><span class="n">Code</span><span class="p" data-group-id="7254832101-31">)</span><span class="p" data-group-id="7254832101-30">}</span><span class="p" data-group-id="7254832101-29">]</span><span class="p" data-group-id="7254832101-28">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="9140840186-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9140840186-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="9140840186-2">(</span><span class="p" data-group-id="9140840186-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9140840186-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9140840186-4">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="9140840186-5">[</span><span class="p" data-group-id="9140840186-5">]</span><span class="p" data-group-id="9140840186-4">}</span><span class="p" data-group-id="9140840186-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="9140840186-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9140840186-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9140840186-7">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9140840186-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="9140840186-9">[</span><span class="p" data-group-id="9140840186-9">]</span><span class="p" data-group-id="9140840186-8">}</span><span class="p" data-group-id="9140840186-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="9140840186-10">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9140840186-11">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9140840186-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="9140840186-12">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="9140840186-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9140840186-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="9645393351-25">(</span><span class="p" data-group-id="9645393351-26">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="9645393351-26">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9645393351-27">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="9645393351-27">}</span><span class="p" data-group-id="9645393351-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9645393351-28">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="9645393351-29">[</span><span class="p" data-group-id="9645393351-30">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="9645393351-31">(</span><span class="n">Code</span><span class="p" data-group-id="9645393351-31">)</span><span class="p" data-group-id="9645393351-30">}</span><span class="p" data-group-id="9645393351-29">]</span><span class="p" data-group-id="9645393351-28">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="3434040238-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3434040238-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="3434040238-2">(</span><span class="p" data-group-id="3434040238-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3434040238-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3434040238-4">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="3434040238-5">[</span><span class="p" data-group-id="3434040238-5">]</span><span class="p" data-group-id="3434040238-4">}</span><span class="p" data-group-id="3434040238-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="3434040238-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3434040238-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3434040238-7">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3434040238-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="3434040238-9">[</span><span class="p" data-group-id="3434040238-9">]</span><span class="p" data-group-id="3434040238-8">}</span><span class="p" data-group-id="3434040238-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="3434040238-10">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3434040238-11">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3434040238-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="3434040238-12">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="3434040238-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3434040238-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │          </span><span class="k">if</span><span class="w">
│ │ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="9140840186-13">(</span><span class="n">Buttons</span><span class="p" data-group-id="9140840186-13">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="3434040238-13">(</span><span class="n">Buttons</span><span class="p" data-group-id="3434040238-13">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="9140840186-14">(</span><span class="n">Buttons</span><span class="p" data-group-id="9140840186-14">)</span><span class="w">
│ │ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="9140840186-15">[</span><span class="n">Button</span><span class="p" data-group-id="9140840186-15">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="3434040238-14">(</span><span class="n">Buttons</span><span class="p" data-group-id="3434040238-14">)</span><span class="w">
│ │ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="3434040238-15">[</span><span class="n">Button</span><span class="p" data-group-id="3434040238-15">]</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="9140840186-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9140840186-16">}</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="3434040238-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3434040238-16">}</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="9140840186-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9140840186-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="9140840186-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="9140840186-19">[</span><span class="p" data-group-id="9140840186-20">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="9140840186-20">}</span><span class="p" data-group-id="9140840186-19">]</span><span class="p" data-group-id="9140840186-17">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="3434040238-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3434040238-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="3434040238-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="3434040238-19">[</span><span class="p" data-group-id="3434040238-20">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="3434040238-20">}</span><span class="p" data-group-id="3434040238-19">]</span><span class="p" data-group-id="3434040238-17">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="1272215641-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="1272215641-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="1272215641-2">(</span><span class="p" data-group-id="1272215641-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1272215641-3">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="1272215641-4">[</span><span class="p" data-group-id="1272215641-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="1272215641-5">}</span><span class="p" data-group-id="1272215641-4">]</span><span class="p" data-group-id="1272215641-3">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="1272215641-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1272215641-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1272215641-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1272215641-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="1272215641-8">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1272215641-9">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1272215641-9">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="1272215641-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1272215641-10">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1272215641-11">[</span><span class="ss">postpone</span><span class="p" data-group-id="1272215641-11">]</span><span class="p" data-group-id="1272215641-10">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="4697885979-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="4697885979-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="4697885979-2">(</span><span class="p" data-group-id="4697885979-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4697885979-3">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="4697885979-4">[</span><span class="p" data-group-id="4697885979-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="4697885979-5">}</span><span class="p" data-group-id="4697885979-4">]</span><span class="p" data-group-id="4697885979-3">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="4697885979-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4697885979-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4697885979-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4697885979-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="4697885979-8">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4697885979-9">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4697885979-9">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="4697885979-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4697885979-10">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4697885979-11">[</span><span class="ss">postpone</span><span class="p" data-group-id="4697885979-11">]</span><span class="p" data-group-id="4697885979-10">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">do_lock</span><span class="p" data-group-id="1272215641-12">(</span><span class="p" data-group-id="1272215641-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1272215641-13">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1272215641-14">[</span><span class="p" data-group-id="1272215641-14">]</span><span class="p" data-group-id="1272215641-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">do_unlock</span><span class="p" data-group-id="1272215641-15">(</span><span class="p" data-group-id="1272215641-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1272215641-16">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1272215641-17">[</span><span class="p" data-group-id="1272215641-17">]</span><span class="p" data-group-id="1272215641-16">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">do_lock</span><span class="p" data-group-id="4697885979-12">(</span><span class="p" data-group-id="4697885979-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4697885979-13">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4697885979-14">[</span><span class="p" data-group-id="4697885979-14">]</span><span class="p" data-group-id="4697885979-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">do_unlock</span><span class="p" data-group-id="4697885979-15">(</span><span class="p" data-group-id="4697885979-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4697885979-16">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4697885979-17">[</span><span class="p" data-group-id="4697885979-17">]</span><span class="p" data-group-id="4697885979-16">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="1272215641-18">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="1272215641-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="1272215641-19">(</span><span class="p" data-group-id="1272215641-19">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="4697885979-18">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="4697885979-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="4697885979-19">(</span><span class="p" data-group-id="4697885979-19">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><h3 id="callback-mode-handle_event_function" class="section-heading">
│ │ │ │    <a href="#callback-mode-handle_event_function" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Callback Mode: handle_event_function</span>
│ │ │ │  </h3>
│ │ │ │  <p>This section describes what to change in the example to use one
│ │ │ │  <code class="inline">handle_event/4</code> function.  The previously used approach to first branch
│ │ │ │  depending on event does not work that well here because of
│ │ │ │ -the <em>state enter calls</em>, so this example first branches depending on state:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5541033840-1">(</span><span class="p" data-group-id="5541033840-2">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="5541033840-2">]</span><span class="p" data-group-id="5541033840-1">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">callback_mode</span><span class="p" data-group-id="3309034769-1">(</span><span class="p" data-group-id="3309034769-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3309034769-2">[</span><span class="ss">handle_event_function</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="3309034769-2">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │ │ +the <em>state enter calls</em>, so this example first branches depending on state:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6843267317-1">(</span><span class="p" data-group-id="6843267317-2">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="6843267317-2">]</span><span class="p" data-group-id="6843267317-1">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">callback_mode</span><span class="p" data-group-id="3570130538-1">(</span><span class="p" data-group-id="3570130538-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3570130538-2">[</span><span class="ss">handle_event_function</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="3570130538-2">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │ │  </span><span class="c1">%% State: locked</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="2751578639-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2751578639-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="2751578639-2">(</span><span class="p" data-group-id="2751578639-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2751578639-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2751578639-4">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="2751578639-5">[</span><span class="p" data-group-id="2751578639-5">]</span><span class="p" data-group-id="2751578639-4">}</span><span class="p" data-group-id="2751578639-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="2751578639-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2751578639-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2751578639-7">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2751578639-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="2751578639-9">[</span><span class="p" data-group-id="2751578639-9">]</span><span class="p" data-group-id="2751578639-8">}</span><span class="p" data-group-id="2751578639-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="2751578639-10">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2751578639-11">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2751578639-11">}</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2751578639-12">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="2751578639-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2751578639-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="6980626492-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6980626492-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="6980626492-2">(</span><span class="p" data-group-id="6980626492-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6980626492-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6980626492-4">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="6980626492-5">[</span><span class="p" data-group-id="6980626492-5">]</span><span class="p" data-group-id="6980626492-4">}</span><span class="p" data-group-id="6980626492-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="6980626492-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6980626492-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6980626492-7">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6980626492-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="6980626492-9">[</span><span class="p" data-group-id="6980626492-9">]</span><span class="p" data-group-id="6980626492-8">}</span><span class="p" data-group-id="6980626492-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="6980626492-10">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6980626492-11">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6980626492-11">}</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6980626492-12">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="6980626492-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6980626492-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │          </span><span class="k">if</span><span class="w">
│ │ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="2751578639-13">(</span><span class="n">Buttons</span><span class="p" data-group-id="2751578639-13">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="6980626492-13">(</span><span class="n">Buttons</span><span class="p" data-group-id="6980626492-13">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="2751578639-14">(</span><span class="n">Buttons</span><span class="p" data-group-id="2751578639-14">)</span><span class="w">
│ │ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="2751578639-15">[</span><span class="n">Button</span><span class="p" data-group-id="2751578639-15">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="6980626492-14">(</span><span class="n">Buttons</span><span class="p" data-group-id="6980626492-14">)</span><span class="w">
│ │ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="6980626492-15">[</span><span class="n">Button</span><span class="p" data-group-id="6980626492-15">]</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="2751578639-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2751578639-16">}</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="6980626492-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6980626492-16">}</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="2751578639-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2751578639-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="2751578639-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="2751578639-19">[</span><span class="p" data-group-id="2751578639-20">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="2751578639-20">}</span><span class="p" data-group-id="2751578639-19">]</span><span class="p" data-group-id="2751578639-17">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="6980626492-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6980626492-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="6980626492-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="6980626492-19">[</span><span class="p" data-group-id="6980626492-20">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="6980626492-20">}</span><span class="p" data-group-id="6980626492-19">]</span><span class="p" data-group-id="6980626492-17">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │ │  </span><span class="c1">%% State: open</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="2990217933-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="2990217933-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="2990217933-2">(</span><span class="p" data-group-id="2990217933-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2990217933-3">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="2990217933-4">[</span><span class="p" data-group-id="2990217933-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="2990217933-5">}</span><span class="p" data-group-id="2990217933-4">]</span><span class="p" data-group-id="2990217933-3">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="2990217933-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2990217933-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2990217933-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2990217933-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="2990217933-8">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2990217933-9">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="2990217933-9">}</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="2990217933-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2990217933-10">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="p" data-group-id="2990217933-11">[</span><span class="ss">postpone</span><span class="p" data-group-id="2990217933-11">]</span><span class="p" data-group-id="2990217933-10">}</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%% Common events</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="3905939161-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3905939161-2">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3905939161-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3905939161-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3905939161-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3905939161-4">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="3905939161-4">}</span><span class="p" data-group-id="3905939161-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="3905939161-5">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3905939161-6">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3905939161-6">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3905939161-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="6458239976-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="6458239976-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="6458239976-2">(</span><span class="p" data-group-id="6458239976-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6458239976-3">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="6458239976-4">[</span><span class="p" data-group-id="6458239976-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="6458239976-5">}</span><span class="p" data-group-id="6458239976-4">]</span><span class="p" data-group-id="6458239976-3">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="6458239976-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6458239976-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6458239976-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6458239976-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="6458239976-8">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6458239976-9">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6458239976-9">}</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="6458239976-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6458239976-10">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="p" data-group-id="6458239976-11">[</span><span class="ss">postpone</span><span class="p" data-group-id="6458239976-11">]</span><span class="p" data-group-id="6458239976-10">}</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%% Common events</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="2018186787-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2018186787-2">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2018186787-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2018186787-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2018186787-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2018186787-4">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="2018186787-4">}</span><span class="p" data-group-id="2018186787-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="2018186787-5">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2018186787-6">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2018186787-6">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2018186787-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Data</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3905939161-7">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="3905939161-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="3905939161-8">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="3905939161-9">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3905939161-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="3905939161-10">[</span><span class="p" data-group-id="3905939161-11">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="3905939161-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3905939161-12">}</span><span class="p" data-group-id="3905939161-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="3905939161-13">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="3905939161-13">}</span><span class="p" data-group-id="3905939161-10">]</span><span class="p" data-group-id="3905939161-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3905939161-14">#{</span><span class="p" data-group-id="3905939161-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="2018186787-7">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="2018186787-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="2018186787-8">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="2018186787-9">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2018186787-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="2018186787-10">[</span><span class="p" data-group-id="2018186787-11">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="2018186787-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2018186787-12">}</span><span class="p" data-group-id="2018186787-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="2018186787-13">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="2018186787-13">}</span><span class="p" data-group-id="2018186787-10">]</span><span class="p" data-group-id="2018186787-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="2018186787-14">#{</span><span class="p" data-group-id="2018186787-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">keep_state_and_data</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="3905939161-15">(</span><span class="p" data-group-id="3905939161-16">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="3905939161-16">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3905939161-17">#{</span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="3905939161-17">}</span><span class="p" data-group-id="3905939161-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3905939161-18">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="3905939161-19">[</span><span class="p" data-group-id="3905939161-20">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">Length</span><span class="p" data-group-id="3905939161-20">}</span><span class="p" data-group-id="3905939161-19">]</span><span class="p" data-group-id="3905939161-18">}</span><span class="p">.</span></code></pre><p>Notice that postponing buttons from the <code class="inline">open</code> state to the <code class="inline">locked</code> state
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="2018186787-15">(</span><span class="p" data-group-id="2018186787-16">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="2018186787-16">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2018186787-17">#{</span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="2018186787-17">}</span><span class="p" data-group-id="2018186787-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2018186787-18">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="2018186787-19">[</span><span class="p" data-group-id="2018186787-20">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">Length</span><span class="p" data-group-id="2018186787-20">}</span><span class="p" data-group-id="2018186787-19">]</span><span class="p" data-group-id="2018186787-18">}</span><span class="p">.</span></code></pre><p>Notice that postponing buttons from the <code class="inline">open</code> state to the <code class="inline">locked</code> state
│ │ │ │  seems like a strange thing to do for a code lock, but it at least
│ │ │ │  illustrates event postponing.</p><h2 id="filter-the-state" class="section-heading">
│ │ │ │    <a href="#filter-the-state" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Filter the State</span>
│ │ │ │  </h2>
│ │ │ │ @@ -1191,30 +1191,30 @@
│ │ │ │  and which digits that remain to unlock.</p><p>This state data can be regarded as sensitive, and maybe not what you want
│ │ │ │  in the error log because of some unpredictable event.</p><p>Another reason to filter the state can be that the state is too large to print,
│ │ │ │  as it fills the error log with uninteresting details.</p><p>To avoid this, you can format the internal state that gets in the error log
│ │ │ │  and gets returned from <a href="../../../lib/stdlib/doc/html/sys.html#get_status/1"><code class="inline">sys:get_status/1,2</code></a>
│ │ │ │  by implementing function
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_statem.html#c:format_status/2"><code class="inline">Module:format_status/2</code></a>,
│ │ │ │  for example like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2375486410-1">(</span><span class="p" data-group-id="2375486410-2">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">format_status</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2375486410-2">]</span><span class="p" data-group-id="2375486410-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1186613946-1">(</span><span class="p" data-group-id="1186613946-2">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">format_status</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1186613946-2">]</span><span class="p" data-group-id="1186613946-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">format_status</span><span class="p" data-group-id="2375486410-3">(</span><span class="n">Opt</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2375486410-4">[</span><span class="p">_</span><span class="n">PDict</span><span class="p">,</span><span class="n">State</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="2375486410-4">]</span><span class="p" data-group-id="2375486410-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">format_status</span><span class="p" data-group-id="1186613946-3">(</span><span class="n">Opt</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1186613946-4">[</span><span class="p">_</span><span class="n">PDict</span><span class="p">,</span><span class="n">State</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="1186613946-4">]</span><span class="p" data-group-id="1186613946-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">StateData</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="2375486410-5">{</span><span class="n">State</span><span class="p">,</span><span class="w">
│ │ │ │ -	 </span><span class="nc">maps</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="2375486410-6">(</span><span class="w">
│ │ │ │ -	   </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="2375486410-7">(</span><span class="ss">code</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="2375486410-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">false</span><span class="p">;</span><span class="w">
│ │ │ │ -	       </span><span class="p" data-group-id="2375486410-8">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="2375486410-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">true</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="1186613946-5">{</span><span class="n">State</span><span class="p">,</span><span class="w">
│ │ │ │ +	 </span><span class="nc">maps</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="1186613946-6">(</span><span class="w">
│ │ │ │ +	   </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="1186613946-7">(</span><span class="ss">code</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="1186613946-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">false</span><span class="p">;</span><span class="w">
│ │ │ │ +	       </span><span class="p" data-group-id="1186613946-8">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="1186613946-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">true</span><span class="w">
│ │ │ │  	   </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -	   </span><span class="n">Data</span><span class="p" data-group-id="2375486410-6">)</span><span class="p" data-group-id="2375486410-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	   </span><span class="n">Data</span><span class="p" data-group-id="1186613946-6">)</span><span class="p" data-group-id="1186613946-5">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Opt</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │  	</span><span class="ss">terminate</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  	    </span><span class="n">StateData</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">normal</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="p" data-group-id="2375486410-9">[</span><span class="p" data-group-id="2375486410-10">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="2375486410-11">[</span><span class="p" data-group-id="2375486410-12">{</span><span class="s">&quot;State&quot;</span><span class="p">,</span><span class="n">StateData</span><span class="p" data-group-id="2375486410-12">}</span><span class="p" data-group-id="2375486410-11">]</span><span class="p" data-group-id="2375486410-10">}</span><span class="p" data-group-id="2375486410-9">]</span><span class="w">
│ │ │ │ +	    </span><span class="p" data-group-id="1186613946-9">[</span><span class="p" data-group-id="1186613946-10">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="1186613946-11">[</span><span class="p" data-group-id="1186613946-12">{</span><span class="s">&quot;State&quot;</span><span class="p">,</span><span class="n">StateData</span><span class="p" data-group-id="1186613946-12">}</span><span class="p" data-group-id="1186613946-11">]</span><span class="p" data-group-id="1186613946-10">}</span><span class="p" data-group-id="1186613946-9">]</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>It is not mandatory to implement a
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_statem.html#c:format_status/2"><code class="inline">Module:format_status/2</code></a> function.
│ │ │ │  If you do not, a default implementation is used that does the same
│ │ │ │  as this example function without filtering the <code class="inline">Data</code> term, that is,
│ │ │ │  <code class="inline">StateData = {State, Data}</code>, in this example containing sensitive information.</p><h2 id="complex-state" class="section-heading">
│ │ │ │    <a href="#complex-state" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │ @@ -1227,104 +1227,104 @@
│ │ │ │  like a tuple.</p><p>One reason to use this is when you have a state item that when changed
│ │ │ │  should cancel the <a href="#state-time-outs"><em>state time-out</em></a>, or one that affects
│ │ │ │  the event handling in combination with postponing events. We will go for
│ │ │ │  the latter and complicate the previous example by introducing
│ │ │ │  a configurable lock button (this is the state item in question),
│ │ │ │  which in the <code class="inline">open</code> state immediately locks the door, and an API function
│ │ │ │  <code class="inline">set_lock_button/1</code> to set the lock button.</p><p>Suppose now that we call <code class="inline">set_lock_button</code> while the door is open,
│ │ │ │ -and we have already postponed a button event that was the new lock button:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="3963811104-1">(</span><span class="p" data-group-id="3963811104-2">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3963811104-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">x</span><span class="p" data-group-id="3963811104-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3963811104-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.666</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="3963811104-3">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="3963811104-4">(</span><span class="ss">a</span><span class="p" data-group-id="3963811104-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +and we have already postponed a button event that was the new lock button:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="0284459849-1">(</span><span class="p" data-group-id="0284459849-2">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="0284459849-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">x</span><span class="p" data-group-id="0284459849-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0284459849-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.666</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0284459849-3">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="0284459849-4">(</span><span class="ss">a</span><span class="p" data-group-id="0284459849-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="3963811104-5">(</span><span class="ss">b</span><span class="p" data-group-id="3963811104-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="0284459849-5">(</span><span class="ss">b</span><span class="p" data-group-id="0284459849-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="3963811104-6">(</span><span class="ss">c</span><span class="p" data-group-id="3963811104-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="0284459849-6">(</span><span class="ss">c</span><span class="p" data-group-id="0284459849-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │  </span><span class="n">Open</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="3963811104-7">(</span><span class="ss">y</span><span class="p" data-group-id="3963811104-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="0284459849-7">(</span><span class="ss">y</span><span class="p" data-group-id="0284459849-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">set_lock_button</span><span class="p" data-group-id="3963811104-8">(</span><span class="ss">y</span><span class="p" data-group-id="3963811104-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">set_lock_button</span><span class="p" data-group-id="0284459849-8">(</span><span class="ss">y</span><span class="p" data-group-id="0284459849-8">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">x</span><span class="w">
│ │ │ │  </span><span class="c1">% What should happen here?  Immediate lock or nothing?</span></code></pre><p>We could say that the button was pressed too early so it should not be
│ │ │ │  recognized as the lock button. Or we can make the lock button part of
│ │ │ │  the state so when we then change the lock button in the locked state,
│ │ │ │  the change becomes a <em>state change</em> and all postponed events are retried,
│ │ │ │  therefore the lock is immediately locked!</p><p>We define the state as <code class="inline">{StateName, LockButton}</code>, where <code class="inline">StateName</code>
│ │ │ │ -is as before and <code class="inline">LockButton</code> is the current lock button:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6378815840-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="6378815840-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="6378815840-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="6378815840-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6378815840-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_3</span><span class="p" data-group-id="6378815840-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +is as before and <code class="inline">LockButton</code> is the current lock button:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8001056600-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="8001056600-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="8001056600-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="8001056600-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8001056600-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_3</span><span class="p" data-group-id="8001056600-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6378815840-4">(</span><span class="p" data-group-id="6378815840-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6378815840-5">]</span><span class="p" data-group-id="6378815840-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6378815840-6">(</span><span class="p" data-group-id="6378815840-7">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">set_lock_button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6378815840-7">]</span><span class="p" data-group-id="6378815840-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6378815840-8">(</span><span class="p" data-group-id="6378815840-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="6378815840-9">]</span><span class="p" data-group-id="6378815840-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6378815840-10">(</span><span class="p" data-group-id="6378815840-11">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="6378815840-11">]</span><span class="p" data-group-id="6378815840-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="6378815840-12">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">LockButton</span><span class="p" data-group-id="6378815840-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="6378815840-13">(</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6378815840-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="6378815840-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6378815840-15">{</span><span class="n">Code</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6378815840-15">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6378815840-16">[</span><span class="p" data-group-id="6378815840-16">]</span><span class="p" data-group-id="6378815840-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="6378815840-17">(</span><span class="p" data-group-id="6378815840-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="6378815840-18">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="6378815840-18">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">button</span><span class="p" data-group-id="6378815840-19">(</span><span class="n">Button</span><span class="p" data-group-id="6378815840-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="6378815840-20">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6378815840-21">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6378815840-21">}</span><span class="p" data-group-id="6378815840-20">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">set_lock_button</span><span class="p" data-group-id="6378815840-22">(</span><span class="n">LockButton</span><span class="p" data-group-id="6378815840-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="6378815840-23">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6378815840-24">{</span><span class="ss">set_lock_button</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6378815840-24">}</span><span class="p" data-group-id="6378815840-23">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="6493246408-1">(</span><span class="p" data-group-id="6493246408-2">{</span><span class="n">Code</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6493246408-2">}</span><span class="p" data-group-id="6493246408-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="6493246408-3">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="6493246408-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6493246408-4">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="6493246408-5">(</span><span class="n">Code</span><span class="p" data-group-id="6493246408-5">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6493246408-6">[</span><span class="p" data-group-id="6493246408-6">]</span><span class="p" data-group-id="6493246408-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6493246408-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6493246408-8">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6493246408-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6493246408-7">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8001056600-4">(</span><span class="p" data-group-id="8001056600-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8001056600-5">]</span><span class="p" data-group-id="8001056600-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8001056600-6">(</span><span class="p" data-group-id="8001056600-7">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">set_lock_button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8001056600-7">]</span><span class="p" data-group-id="8001056600-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8001056600-8">(</span><span class="p" data-group-id="8001056600-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="8001056600-9">]</span><span class="p" data-group-id="8001056600-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8001056600-10">(</span><span class="p" data-group-id="8001056600-11">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="8001056600-11">]</span><span class="p" data-group-id="8001056600-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="8001056600-12">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">LockButton</span><span class="p" data-group-id="8001056600-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="8001056600-13">(</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="8001056600-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="8001056600-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8001056600-15">{</span><span class="n">Code</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="8001056600-15">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8001056600-16">[</span><span class="p" data-group-id="8001056600-16">]</span><span class="p" data-group-id="8001056600-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="8001056600-17">(</span><span class="p" data-group-id="8001056600-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="8001056600-18">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="8001056600-18">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">button</span><span class="p" data-group-id="8001056600-19">(</span><span class="n">Button</span><span class="p" data-group-id="8001056600-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="8001056600-20">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8001056600-21">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="8001056600-21">}</span><span class="p" data-group-id="8001056600-20">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">set_lock_button</span><span class="p" data-group-id="8001056600-22">(</span><span class="n">LockButton</span><span class="p" data-group-id="8001056600-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="8001056600-23">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8001056600-24">{</span><span class="ss">set_lock_button</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="8001056600-24">}</span><span class="p" data-group-id="8001056600-23">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="1921521258-1">(</span><span class="p" data-group-id="1921521258-2">{</span><span class="n">Code</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="1921521258-2">}</span><span class="p" data-group-id="1921521258-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="1921521258-3">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="1921521258-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1921521258-4">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="1921521258-5">(</span><span class="n">Code</span><span class="p" data-group-id="1921521258-5">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1921521258-6">[</span><span class="p" data-group-id="1921521258-6">]</span><span class="p" data-group-id="1921521258-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1921521258-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1921521258-8">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="1921521258-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1921521258-7">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="6493246408-9">(</span><span class="p" data-group-id="6493246408-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6493246408-10">[</span><span class="ss">handle_event_function</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="6493246408-10">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="1921521258-9">(</span><span class="p" data-group-id="1921521258-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1921521258-10">[</span><span class="ss">handle_event_function</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="1921521258-10">]</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% State: locked</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="6493246408-11">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6493246408-12">{</span><span class="ss">locked</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6493246408-12">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6493246408-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="6493246408-13">(</span><span class="p" data-group-id="6493246408-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6493246408-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6493246408-15">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="6493246408-16">[</span><span class="p" data-group-id="6493246408-16">]</span><span class="p" data-group-id="6493246408-15">}</span><span class="p" data-group-id="6493246408-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="6493246408-17">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6493246408-18">{</span><span class="ss">locked</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6493246408-18">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6493246408-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6493246408-19">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6493246408-20">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="6493246408-21">[</span><span class="p" data-group-id="6493246408-21">]</span><span class="p" data-group-id="6493246408-20">}</span><span class="p" data-group-id="6493246408-19">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="6493246408-22">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6493246408-23">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6493246408-23">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6493246408-24">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6493246408-24">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6493246408-25">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="6493246408-25">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6493246408-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1921521258-11">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1921521258-12">{</span><span class="ss">locked</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1921521258-12">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1921521258-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="1921521258-13">(</span><span class="p" data-group-id="1921521258-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1921521258-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1921521258-15">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="1921521258-16">[</span><span class="p" data-group-id="1921521258-16">]</span><span class="p" data-group-id="1921521258-15">}</span><span class="p" data-group-id="1921521258-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1921521258-17">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1921521258-18">{</span><span class="ss">locked</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1921521258-18">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1921521258-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1921521258-19">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1921521258-20">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="1921521258-21">[</span><span class="p" data-group-id="1921521258-21">]</span><span class="p" data-group-id="1921521258-20">}</span><span class="p" data-group-id="1921521258-19">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1921521258-22">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1921521258-23">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1921521258-23">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1921521258-24">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="1921521258-24">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="1921521258-25">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="1921521258-25">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1921521258-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │          </span><span class="k">if</span><span class="w">
│ │ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="6493246408-26">(</span><span class="n">Buttons</span><span class="p" data-group-id="6493246408-26">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="1921521258-26">(</span><span class="n">Buttons</span><span class="p" data-group-id="1921521258-26">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="6493246408-27">(</span><span class="n">Buttons</span><span class="p" data-group-id="6493246408-27">)</span><span class="w">
│ │ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="6493246408-28">[</span><span class="n">Button</span><span class="p" data-group-id="6493246408-28">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="1921521258-27">(</span><span class="n">Buttons</span><span class="p" data-group-id="1921521258-27">)</span><span class="w">
│ │ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="1921521258-28">[</span><span class="n">Button</span><span class="p" data-group-id="1921521258-28">]</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="6493246408-29">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6493246408-30">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6493246408-30">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6493246408-29">}</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="1921521258-29">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1921521258-30">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="1921521258-30">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1921521258-29">}</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="6493246408-31">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6493246408-32">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="6493246408-32">}</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="6493246408-33">[</span><span class="p" data-group-id="6493246408-34">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="6493246408-34">}</span><span class="p" data-group-id="6493246408-33">]</span><span class="p" data-group-id="6493246408-31">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="1921521258-31">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1921521258-32">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="1921521258-32">}</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="1921521258-33">[</span><span class="p" data-group-id="1921521258-34">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="1921521258-34">}</span><span class="p" data-group-id="1921521258-33">]</span><span class="p" data-group-id="1921521258-31">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │ │  </span><span class="c1">%% State: open</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="0658215176-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0658215176-2">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0658215176-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="0658215176-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="0658215176-3">(</span><span class="p" data-group-id="0658215176-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0658215176-4">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="0658215176-5">[</span><span class="p" data-group-id="0658215176-6">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="0658215176-6">}</span><span class="p" data-group-id="0658215176-5">]</span><span class="p" data-group-id="0658215176-4">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="0658215176-7">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0658215176-8">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="0658215176-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0658215176-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0658215176-9">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0658215176-10">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="0658215176-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0658215176-9">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="0658215176-11">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0658215176-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="0658215176-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0658215176-13">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="0658215176-13">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0658215176-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0658215176-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0658215176-15">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="0658215176-15">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0658215176-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="0658215176-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0658215176-17">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0658215176-17">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0658215176-18">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0658215176-18">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="0658215176-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0658215176-19">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="p" data-group-id="0658215176-20">[</span><span class="ss">postpone</span><span class="p" data-group-id="0658215176-20">]</span><span class="p" data-group-id="0658215176-19">}</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="0921941705-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0921941705-2">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0921941705-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="0921941705-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="0921941705-3">(</span><span class="p" data-group-id="0921941705-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0921941705-4">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="0921941705-5">[</span><span class="p" data-group-id="0921941705-6">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="0921941705-6">}</span><span class="p" data-group-id="0921941705-5">]</span><span class="p" data-group-id="0921941705-4">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="0921941705-7">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0921941705-8">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="0921941705-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0921941705-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0921941705-9">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0921941705-10">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="0921941705-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0921941705-9">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="0921941705-11">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0921941705-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="0921941705-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0921941705-13">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="0921941705-13">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0921941705-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0921941705-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0921941705-15">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="0921941705-15">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0921941705-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="0921941705-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0921941705-17">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0921941705-17">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0921941705-18">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0921941705-18">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="0921941705-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0921941705-19">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="p" data-group-id="0921941705-20">[</span><span class="ss">postpone</span><span class="p" data-group-id="0921941705-20">]</span><span class="p" data-group-id="0921941705-19">}</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │ │  </span><span class="c1">%% Common events</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="4318195627-1">(</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="4318195627-2">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="4318195627-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4318195627-3">{</span><span class="ss">set_lock_button</span><span class="p">,</span><span class="n">NewLockButton</span><span class="p" data-group-id="4318195627-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="4318195627-4">{</span><span class="n">StateName</span><span class="p">,</span><span class="n">OldLockButton</span><span class="p" data-group-id="4318195627-4">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4318195627-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4318195627-5">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4318195627-6">{</span><span class="n">StateName</span><span class="p">,</span><span class="n">NewLockButton</span><span class="p" data-group-id="4318195627-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="4318195627-7">[</span><span class="p" data-group-id="4318195627-8">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">OldLockButton</span><span class="p" data-group-id="4318195627-8">}</span><span class="p" data-group-id="4318195627-7">]</span><span class="p" data-group-id="4318195627-5">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">do_lock</span><span class="p" data-group-id="4547909584-1">(</span><span class="p" data-group-id="4547909584-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4547909584-2">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4547909584-3">[</span><span class="p" data-group-id="4547909584-3">]</span><span class="p" data-group-id="4547909584-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">do_unlock</span><span class="p" data-group-id="4547909584-4">(</span><span class="p" data-group-id="4547909584-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4547909584-5">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4547909584-6">[</span><span class="p" data-group-id="4547909584-6">]</span><span class="p" data-group-id="4547909584-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8781778513-1">(</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8781778513-2">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="8781778513-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8781778513-3">{</span><span class="ss">set_lock_button</span><span class="p">,</span><span class="n">NewLockButton</span><span class="p" data-group-id="8781778513-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8781778513-4">{</span><span class="n">StateName</span><span class="p">,</span><span class="n">OldLockButton</span><span class="p" data-group-id="8781778513-4">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8781778513-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8781778513-5">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8781778513-6">{</span><span class="n">StateName</span><span class="p">,</span><span class="n">NewLockButton</span><span class="p" data-group-id="8781778513-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="8781778513-7">[</span><span class="p" data-group-id="8781778513-8">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">OldLockButton</span><span class="p" data-group-id="8781778513-8">}</span><span class="p" data-group-id="8781778513-7">]</span><span class="p" data-group-id="8781778513-5">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">do_lock</span><span class="p" data-group-id="5331282193-1">(</span><span class="p" data-group-id="5331282193-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5331282193-2">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5331282193-3">[</span><span class="p" data-group-id="5331282193-3">]</span><span class="p" data-group-id="5331282193-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">do_unlock</span><span class="p" data-group-id="5331282193-4">(</span><span class="p" data-group-id="5331282193-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5331282193-5">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5331282193-6">[</span><span class="p" data-group-id="5331282193-6">]</span><span class="p" data-group-id="5331282193-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="4547909584-7">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="4547909584-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="4547909584-8">(</span><span class="p" data-group-id="4547909584-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="5331282193-7">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="5331282193-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="5331282193-8">(</span><span class="p" data-group-id="5331282193-8">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><h2 id="hibernation" class="section-heading">
│ │ │ │    <a href="#hibernation" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Hibernation</span>
│ │ │ │  </h2>
│ │ │ │  <p>If you have many servers in one node and they have some state(s) in their
│ │ │ │ @@ -1333,19 +1333,19 @@
│ │ │ │  footprint of a server can be minimized by hibernating it through
│ │ │ │  <a href="../../../lib/stdlib/doc/html/proc_lib.html#hibernate/3"><code class="inline">proc_lib:hibernate/3</code></a>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>It is rather costly to hibernate a process; see <a href="../../../lib/../erts/doc/html/erlang.html#hibernate/3"><code class="inline">erlang:hibernate/3</code></a>. It is
│ │ │ │  not something you want to do after every event.</p></section><p>We can in this example hibernate in the <code class="inline">{open, _}</code> state,
│ │ │ │  because what normally occurs in that state is that the <em>state time-out</em>
│ │ │ │  after a while triggers a transition to <code class="inline">{locked, _}</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │  </span><span class="c1">%% State: open</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="9017795662-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9017795662-2">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9017795662-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="9017795662-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="9017795662-3">(</span><span class="p" data-group-id="9017795662-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9017795662-4">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="9017795662-5">[</span><span class="p" data-group-id="9017795662-6">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="9017795662-6">}</span><span class="p">,</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ -      </span><span class="ss">hibernate</span><span class="p" data-group-id="9017795662-5">]</span><span class="p" data-group-id="9017795662-4">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1677631568-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1677631568-2">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1677631568-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="1677631568-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="1677631568-3">(</span><span class="p" data-group-id="1677631568-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1677631568-4">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="1677631568-5">[</span><span class="p" data-group-id="1677631568-6">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="1677631568-6">}</span><span class="p">,</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +      </span><span class="ss">hibernate</span><span class="p" data-group-id="1677631568-5">]</span><span class="p" data-group-id="1677631568-4">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>The atom <a href="../../../lib/stdlib/doc/html/gen_statem.html#t:hibernate/0"><code class="inline">hibernate</code></a> in the action list on the
│ │ │ │  last line when entering the <code class="inline">{open, _}</code> state is the only change. If any event
│ │ │ │  arrives in the <code class="inline">{open, _},</code> state, we do not bother to rehibernate,
│ │ │ │  so the server stays awake after any event.</p><p>To change that we would need to insert action <code class="inline">hibernate</code> in more places.
│ │ │ │  For example, the state-independent <code class="inline">set_lock_button</code> operation
│ │ │ │  would have to use <code class="inline">hibernate</code> but only in the <code class="inline">{open, _}</code> state,
│ │ │ │  which would clutter the code.</p><p>Another not uncommon scenario is to use the
│ │ │ ├── OEBPS/spec_proc.xhtml
│ │ │ │ @@ -28,72 +28,72 @@
│ │ │ │    <a href="#simple-debugging" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Simple Debugging</span>
│ │ │ │  </h2>
│ │ │ │  <p>The <a href="../../../lib/stdlib/doc/html/sys.html"><code class="inline">sys</code></a> module has functions for simple debugging of processes implemented
│ │ │ │  using behaviours. The <code class="inline">code_lock</code> example from
│ │ │ │ -<a href="statem.xhtml#example">gen_statem Behaviour</a> is used to illustrate this:</p><pre><code class="makeup erlang" translate="no"><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="3693282988-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">15.0</span><span class="p" data-group-id="3693282988-1">]</span><span class="w"> </span><span class="p" data-group-id="3693282988-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="3693282988-2">]</span><span class="w"> </span><span class="p" data-group-id="3693282988-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="3693282988-3">]</span><span class="w"> </span><span class="p" data-group-id="3693282988-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="3693282988-4">]</span><span class="w"> </span><span class="p" data-group-id="3693282988-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="3693282988-5">]</span><span class="w"> </span><span class="p" data-group-id="3693282988-6">[</span><span class="ss">jit</span><span class="p" data-group-id="3693282988-6">]</span><span class="w">
│ │ │ │ +<a href="statem.xhtml#example">gen_statem Behaviour</a> is used to illustrate this:</p><pre><code class="makeup erlang" translate="no"><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="3438002146-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">15.0</span><span class="p" data-group-id="3438002146-1">]</span><span class="w"> </span><span class="p" data-group-id="3438002146-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="3438002146-2">]</span><span class="w"> </span><span class="p" data-group-id="3438002146-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="3438002146-3">]</span><span class="w"> </span><span class="p" data-group-id="3438002146-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="3438002146-4">]</span><span class="w"> </span><span class="p" data-group-id="3438002146-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="3438002146-5">]</span><span class="w"> </span><span class="p" data-group-id="3438002146-6">[</span><span class="ss">jit</span><span class="p" data-group-id="3438002146-6">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V15</span><span class="p">.</span><span class="mi">0</span><span class="w"> </span><span class="p" data-group-id="3693282988-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="3693282988-8">(</span><span class="p" data-group-id="3693282988-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="3693282988-7">)</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="3693282988-9">(</span><span class="p" data-group-id="3693282988-10">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3693282988-10">]</span><span class="p" data-group-id="3693282988-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V15</span><span class="p">.</span><span class="mi">0</span><span class="w"> </span><span class="p" data-group-id="3438002146-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="3438002146-8">(</span><span class="p" data-group-id="3438002146-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="3438002146-7">)</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="3438002146-9">(</span><span class="p" data-group-id="3438002146-10">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3438002146-10">]</span><span class="p" data-group-id="3438002146-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="n">Lock</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3693282988-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="3693282988-11">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="3693282988-12">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3693282988-12">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3438002146-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="3438002146-11">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="3438002146-12">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3438002146-12">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="3693282988-13">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3693282988-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="3438002146-13">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3438002146-13">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="3693282988-14">(</span><span class="mi">1</span><span class="p" data-group-id="3693282988-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="3693282988-15">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3693282988-15">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="3438002146-14">(</span><span class="mi">1</span><span class="p" data-group-id="3438002146-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="3438002146-15">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3438002146-15">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="3693282988-16">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3693282988-16">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="3693282988-17">(</span><span class="mi">2</span><span class="p" data-group-id="3693282988-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="3693282988-18">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3693282988-18">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="3438002146-16">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3438002146-16">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="3438002146-17">(</span><span class="mi">2</span><span class="p" data-group-id="3438002146-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="3438002146-18">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3438002146-18">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="3693282988-19">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3693282988-19">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="3693282988-20">(</span><span class="mi">3</span><span class="p" data-group-id="3693282988-20">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="3693282988-21">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3693282988-21">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="3438002146-19">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3438002146-19">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="3438002146-20">(</span><span class="mi">3</span><span class="p" data-group-id="3438002146-20">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="3438002146-21">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3438002146-21">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="3693282988-22">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3693282988-22">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">7&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="3693282988-23">(</span><span class="mi">4</span><span class="p" data-group-id="3693282988-23">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="3693282988-24">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3693282988-24">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="3438002146-22">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3438002146-22">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">7&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="3438002146-23">(</span><span class="mi">4</span><span class="p" data-group-id="3438002146-23">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="3438002146-24">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3438002146-24">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │  </span><span class="n">Unlock</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="3693282988-25">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3693282988-25">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="nb">start_timer</span><span class="w"> </span><span class="p" data-group-id="3693282988-26">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10000</span><span class="p">,</span><span class="ss">lock</span><span class="p">,</span><span class="p" data-group-id="3693282988-27">[</span><span class="p" data-group-id="3693282988-27">]</span><span class="p" data-group-id="3693282988-26">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="3438002146-25">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3438002146-25">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="nb">start_timer</span><span class="w"> </span><span class="p" data-group-id="3438002146-26">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10000</span><span class="p">,</span><span class="ss">lock</span><span class="p">,</span><span class="p" data-group-id="3438002146-27">[</span><span class="p" data-group-id="3438002146-27">]</span><span class="p" data-group-id="3438002146-26">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │ │  </span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">state_timeout</span><span class="w"> </span><span class="ss">lock</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │ │  </span><span class="n">Lock</span><span class="w">
│ │ │ │  </span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">state_timeout</span><span class="w"> </span><span class="ss">lock</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">open</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">8&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="3693282988-28">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="nb">get</span><span class="p" data-group-id="3693282988-28">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3693282988-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="3693282988-30">[</span><span class="p" data-group-id="3693282988-31">{</span><span class="ss">start_time</span><span class="p">,</span><span class="p" data-group-id="3693282988-32">{</span><span class="p" data-group-id="3693282988-33">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3693282988-33">}</span><span class="p">,</span><span class="p" data-group-id="3693282988-34">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3693282988-34">}</span><span class="p" data-group-id="3693282988-32">}</span><span class="p" data-group-id="3693282988-31">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="3693282988-35">{</span><span class="ss">current_time</span><span class="p">,</span><span class="p" data-group-id="3693282988-36">{</span><span class="p" data-group-id="3693282988-37">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3693282988-37">}</span><span class="p">,</span><span class="p" data-group-id="3693282988-38">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">48</span><span class="p" data-group-id="3693282988-38">}</span><span class="p" data-group-id="3693282988-36">}</span><span class="p" data-group-id="3693282988-35">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="3693282988-39">{</span><span class="ss">reductions</span><span class="p">,</span><span class="mi">4098</span><span class="p" data-group-id="3693282988-39">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="3693282988-40">{</span><span class="ss">messages_in</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="3693282988-40">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="3693282988-41">{</span><span class="ss">messages_out</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="3693282988-41">}</span><span class="p" data-group-id="3693282988-30">]</span><span class="p" data-group-id="3693282988-29">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">9&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="3693282988-42">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="3693282988-42">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">10&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="3693282988-43">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="3693282988-43">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">11&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">get_status</span><span class="p" data-group-id="3693282988-44">(</span><span class="ss">code_lock</span><span class="p" data-group-id="3693282988-44">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3693282988-45">{</span><span class="ss">status</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3693282988-46">{</span><span class="ss">module</span><span class="p">,</span><span class="ss">gen_statem</span><span class="p" data-group-id="3693282988-46">}</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3693282988-47">[</span><span class="p" data-group-id="3693282988-48">[</span><span class="p" data-group-id="3693282988-49">{</span><span class="ss">&#39;$initial_call&#39;</span><span class="p">,</span><span class="p" data-group-id="3693282988-50">{</span><span class="ss">code_lock</span><span class="p">,</span><span class="ss">init</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3693282988-50">}</span><span class="p" data-group-id="3693282988-49">}</span><span class="p">,</span><span class="w">
│ │ │ │ -          </span><span class="p" data-group-id="3693282988-51">{</span><span class="ss">&#39;$ancestors&#39;</span><span class="p">,</span><span class="p" data-group-id="3693282988-52">[</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.87</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.70</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.65</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.69</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ -                         </span><span class="o">&lt;</span><span class="mf">0.64</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">kernel_sup</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.47</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="3693282988-52">]</span><span class="p" data-group-id="3693282988-51">}</span><span class="p" data-group-id="3693282988-48">]</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="ss">running</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="p" data-group-id="3693282988-53">[</span><span class="p" data-group-id="3693282988-53">]</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="3693282988-54">[</span><span class="p" data-group-id="3693282988-55">{</span><span class="ss">header</span><span class="p">,</span><span class="s">&quot;Status for state machine code_lock&quot;</span><span class="p" data-group-id="3693282988-55">}</span><span class="p">,</span><span class="w">
│ │ │ │ -          </span><span class="p" data-group-id="3693282988-56">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="3693282988-57">[</span><span class="p" data-group-id="3693282988-58">{</span><span class="s">&quot;Status&quot;</span><span class="p">,</span><span class="ss">running</span><span class="p" data-group-id="3693282988-58">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                 </span><span class="p" data-group-id="3693282988-59">{</span><span class="s">&quot;Parent&quot;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="3693282988-59">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                 </span><span class="p" data-group-id="3693282988-60">{</span><span class="s">&quot;Modules&quot;</span><span class="p">,</span><span class="p" data-group-id="3693282988-61">[</span><span class="ss">code_lock</span><span class="p" data-group-id="3693282988-61">]</span><span class="p" data-group-id="3693282988-60">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                 </span><span class="p" data-group-id="3693282988-62">{</span><span class="s">&quot;Time-outs&quot;</span><span class="p">,</span><span class="p" data-group-id="3693282988-63">{</span><span class="mi">0</span><span class="p">,</span><span class="p" data-group-id="3693282988-64">[</span><span class="p" data-group-id="3693282988-64">]</span><span class="p" data-group-id="3693282988-63">}</span><span class="p" data-group-id="3693282988-62">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                 </span><span class="p" data-group-id="3693282988-65">{</span><span class="s">&quot;Logged Events&quot;</span><span class="p">,</span><span class="p" data-group-id="3693282988-66">[</span><span class="p" data-group-id="3693282988-66">]</span><span class="p" data-group-id="3693282988-65">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                 </span><span class="p" data-group-id="3693282988-67">{</span><span class="s">&quot;Postponed&quot;</span><span class="p">,</span><span class="p" data-group-id="3693282988-68">[</span><span class="p" data-group-id="3693282988-68">]</span><span class="p" data-group-id="3693282988-67">}</span><span class="p" data-group-id="3693282988-57">]</span><span class="p" data-group-id="3693282988-56">}</span><span class="p">,</span><span class="w">
│ │ │ │ -          </span><span class="p" data-group-id="3693282988-69">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="3693282988-70">[</span><span class="p" data-group-id="3693282988-71">{</span><span class="s">&quot;State&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -                  </span><span class="p" data-group-id="3693282988-72">{</span><span class="ss">locked</span><span class="p">,</span><span class="p" data-group-id="3693282988-73">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3693282988-74">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3693282988-74">]</span><span class="p">,</span><span class="w">
│ │ │ │ -                            </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3693282988-75">[</span><span class="p" data-group-id="3693282988-75">]</span><span class="p" data-group-id="3693282988-73">}</span><span class="p" data-group-id="3693282988-72">}</span><span class="p" data-group-id="3693282988-71">}</span><span class="p" data-group-id="3693282988-70">]</span><span class="p" data-group-id="3693282988-69">}</span><span class="p" data-group-id="3693282988-54">]</span><span class="p" data-group-id="3693282988-47">]</span><span class="p" data-group-id="3693282988-45">}</span></code></pre><h2 id="special-processes" class="section-heading">
│ │ │ │ +</span><span class="gp unselectable">8&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="3438002146-28">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="nb">get</span><span class="p" data-group-id="3438002146-28">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3438002146-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="3438002146-30">[</span><span class="p" data-group-id="3438002146-31">{</span><span class="ss">start_time</span><span class="p">,</span><span class="p" data-group-id="3438002146-32">{</span><span class="p" data-group-id="3438002146-33">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3438002146-33">}</span><span class="p">,</span><span class="p" data-group-id="3438002146-34">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3438002146-34">}</span><span class="p" data-group-id="3438002146-32">}</span><span class="p" data-group-id="3438002146-31">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="3438002146-35">{</span><span class="ss">current_time</span><span class="p">,</span><span class="p" data-group-id="3438002146-36">{</span><span class="p" data-group-id="3438002146-37">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3438002146-37">}</span><span class="p">,</span><span class="p" data-group-id="3438002146-38">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">48</span><span class="p" data-group-id="3438002146-38">}</span><span class="p" data-group-id="3438002146-36">}</span><span class="p" data-group-id="3438002146-35">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="3438002146-39">{</span><span class="ss">reductions</span><span class="p">,</span><span class="mi">4098</span><span class="p" data-group-id="3438002146-39">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="3438002146-40">{</span><span class="ss">messages_in</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="3438002146-40">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="3438002146-41">{</span><span class="ss">messages_out</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="3438002146-41">}</span><span class="p" data-group-id="3438002146-30">]</span><span class="p" data-group-id="3438002146-29">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">9&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="3438002146-42">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="3438002146-42">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">ok</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">10&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="3438002146-43">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="3438002146-43">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">ok</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">11&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">get_status</span><span class="p" data-group-id="3438002146-44">(</span><span class="ss">code_lock</span><span class="p" data-group-id="3438002146-44">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3438002146-45">{</span><span class="ss">status</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3438002146-46">{</span><span class="ss">module</span><span class="p">,</span><span class="ss">gen_statem</span><span class="p" data-group-id="3438002146-46">}</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3438002146-47">[</span><span class="p" data-group-id="3438002146-48">[</span><span class="p" data-group-id="3438002146-49">{</span><span class="ss">&#39;$initial_call&#39;</span><span class="p">,</span><span class="p" data-group-id="3438002146-50">{</span><span class="ss">code_lock</span><span class="p">,</span><span class="ss">init</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3438002146-50">}</span><span class="p" data-group-id="3438002146-49">}</span><span class="p">,</span><span class="w">
│ │ │ │ +          </span><span class="p" data-group-id="3438002146-51">{</span><span class="ss">&#39;$ancestors&#39;</span><span class="p">,</span><span class="p" data-group-id="3438002146-52">[</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.87</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.70</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.65</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.69</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ +                         </span><span class="o">&lt;</span><span class="mf">0.64</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">kernel_sup</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.47</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="3438002146-52">]</span><span class="p" data-group-id="3438002146-51">}</span><span class="p" data-group-id="3438002146-48">]</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="ss">running</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="p" data-group-id="3438002146-53">[</span><span class="p" data-group-id="3438002146-53">]</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="3438002146-54">[</span><span class="p" data-group-id="3438002146-55">{</span><span class="ss">header</span><span class="p">,</span><span class="s">&quot;Status for state machine code_lock&quot;</span><span class="p" data-group-id="3438002146-55">}</span><span class="p">,</span><span class="w">
│ │ │ │ +          </span><span class="p" data-group-id="3438002146-56">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="3438002146-57">[</span><span class="p" data-group-id="3438002146-58">{</span><span class="s">&quot;Status&quot;</span><span class="p">,</span><span class="ss">running</span><span class="p" data-group-id="3438002146-58">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                 </span><span class="p" data-group-id="3438002146-59">{</span><span class="s">&quot;Parent&quot;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="3438002146-59">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                 </span><span class="p" data-group-id="3438002146-60">{</span><span class="s">&quot;Modules&quot;</span><span class="p">,</span><span class="p" data-group-id="3438002146-61">[</span><span class="ss">code_lock</span><span class="p" data-group-id="3438002146-61">]</span><span class="p" data-group-id="3438002146-60">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                 </span><span class="p" data-group-id="3438002146-62">{</span><span class="s">&quot;Time-outs&quot;</span><span class="p">,</span><span class="p" data-group-id="3438002146-63">{</span><span class="mi">0</span><span class="p">,</span><span class="p" data-group-id="3438002146-64">[</span><span class="p" data-group-id="3438002146-64">]</span><span class="p" data-group-id="3438002146-63">}</span><span class="p" data-group-id="3438002146-62">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                 </span><span class="p" data-group-id="3438002146-65">{</span><span class="s">&quot;Logged Events&quot;</span><span class="p">,</span><span class="p" data-group-id="3438002146-66">[</span><span class="p" data-group-id="3438002146-66">]</span><span class="p" data-group-id="3438002146-65">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                 </span><span class="p" data-group-id="3438002146-67">{</span><span class="s">&quot;Postponed&quot;</span><span class="p">,</span><span class="p" data-group-id="3438002146-68">[</span><span class="p" data-group-id="3438002146-68">]</span><span class="p" data-group-id="3438002146-67">}</span><span class="p" data-group-id="3438002146-57">]</span><span class="p" data-group-id="3438002146-56">}</span><span class="p">,</span><span class="w">
│ │ │ │ +          </span><span class="p" data-group-id="3438002146-69">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="3438002146-70">[</span><span class="p" data-group-id="3438002146-71">{</span><span class="s">&quot;State&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +                  </span><span class="p" data-group-id="3438002146-72">{</span><span class="ss">locked</span><span class="p">,</span><span class="p" data-group-id="3438002146-73">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3438002146-74">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3438002146-74">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                            </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3438002146-75">[</span><span class="p" data-group-id="3438002146-75">]</span><span class="p" data-group-id="3438002146-73">}</span><span class="p" data-group-id="3438002146-72">}</span><span class="p" data-group-id="3438002146-71">}</span><span class="p" data-group-id="3438002146-70">]</span><span class="p" data-group-id="3438002146-69">}</span><span class="p" data-group-id="3438002146-54">]</span><span class="p" data-group-id="3438002146-47">]</span><span class="p" data-group-id="3438002146-45">}</span></code></pre><h2 id="special-processes" class="section-heading">
│ │ │ │    <a href="#special-processes" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Special Processes</span>
│ │ │ │  </h2>
│ │ │ │  <p>This section describes how to write a process that complies to the OTP design
│ │ │ │  principles, without using a standard behaviour. Such a process is to:</p><ul><li>Be started in a way that makes the process fit into a supervision tree</li><li>Support the <code class="inline">sys</code> <a href="spec_proc.xhtml#debug">debug facilities</a></li><li>Take care of <a href="spec_proc.xhtml#msg">system messages</a>.</li></ul><p>System messages are messages with a special meaning, used in the supervision
│ │ │ │ @@ -103,238 +103,238 @@
│ │ │ │    <a href="#example" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Example</span>
│ │ │ │  </h3>
│ │ │ │  <p>Here follows the simple server from
│ │ │ │  <a href="design_principles.xhtml#ch1">Overview</a>,
│ │ │ │ -implemented using <code class="inline">sys</code> and <code class="inline">proc_lib</code> to fit into a supervision tree:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4758882748-1">(</span><span class="ss">ch4</span><span class="p" data-group-id="4758882748-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4758882748-2">(</span><span class="p" data-group-id="4758882748-3">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4758882748-3">]</span><span class="p" data-group-id="4758882748-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4758882748-4">(</span><span class="p" data-group-id="4758882748-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4758882748-5">]</span><span class="p" data-group-id="4758882748-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4758882748-6">(</span><span class="p" data-group-id="4758882748-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4758882748-7">]</span><span class="p" data-group-id="4758882748-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4758882748-8">(</span><span class="p" data-group-id="4758882748-9">[</span><span class="ss">system_continue</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">system_terminate</span><span class="p">/</span><span class="mi">4</span><span class="p">,</span><span class="w">
│ │ │ │ +implemented using <code class="inline">sys</code> and <code class="inline">proc_lib</code> to fit into a supervision tree:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6824952753-1">(</span><span class="ss">ch4</span><span class="p" data-group-id="6824952753-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6824952753-2">(</span><span class="p" data-group-id="6824952753-3">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6824952753-3">]</span><span class="p" data-group-id="6824952753-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6824952753-4">(</span><span class="p" data-group-id="6824952753-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6824952753-5">]</span><span class="p" data-group-id="6824952753-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6824952753-6">(</span><span class="p" data-group-id="6824952753-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6824952753-7">]</span><span class="p" data-group-id="6824952753-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6824952753-8">(</span><span class="p" data-group-id="6824952753-9">[</span><span class="ss">system_continue</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">system_terminate</span><span class="p">/</span><span class="mi">4</span><span class="p">,</span><span class="w">
│ │ │ │           </span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="ss">system_get_state</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">system_replace_state</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4758882748-9">]</span><span class="p" data-group-id="4758882748-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +         </span><span class="ss">system_get_state</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">system_replace_state</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6824952753-9">]</span><span class="p" data-group-id="6824952753-8">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="4758882748-10">(</span><span class="p" data-group-id="4758882748-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="4758882748-11">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4758882748-12">[</span><span class="nf">self</span><span class="p" data-group-id="4758882748-13">(</span><span class="p" data-group-id="4758882748-13">)</span><span class="p" data-group-id="4758882748-12">]</span><span class="p" data-group-id="4758882748-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="6824952753-10">(</span><span class="p" data-group-id="6824952753-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="6824952753-11">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6824952753-12">[</span><span class="nf">self</span><span class="p" data-group-id="6824952753-13">(</span><span class="p" data-group-id="6824952753-13">)</span><span class="p" data-group-id="6824952753-12">]</span><span class="p" data-group-id="6824952753-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="4758882748-14">(</span><span class="p" data-group-id="4758882748-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ch4</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4758882748-15">{</span><span class="nf">self</span><span class="p" data-group-id="4758882748-16">(</span><span class="p" data-group-id="4758882748-16">)</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="4758882748-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="6824952753-14">(</span><span class="p" data-group-id="6824952753-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ch4</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6824952753-15">{</span><span class="nf">self</span><span class="p" data-group-id="6824952753-16">(</span><span class="p" data-group-id="6824952753-16">)</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="6824952753-15">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="4758882748-17">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="4758882748-17">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="6824952753-17">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="6824952753-17">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="n">Res</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="4758882748-18">(</span><span class="n">Ch</span><span class="p" data-group-id="4758882748-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ch4</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4758882748-19">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4758882748-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="6824952753-18">(</span><span class="n">Ch</span><span class="p" data-group-id="6824952753-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ch4</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6824952753-19">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="6824952753-19">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="4758882748-20">(</span><span class="n">Parent</span><span class="p" data-group-id="4758882748-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="4758882748-21">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4758882748-22">(</span><span class="p" data-group-id="4758882748-22">)</span><span class="p" data-group-id="4758882748-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Chs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="4758882748-23">(</span><span class="p" data-group-id="4758882748-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Deb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="4758882748-24">(</span><span class="p" data-group-id="4758882748-25">[</span><span class="p" data-group-id="4758882748-25">]</span><span class="p" data-group-id="4758882748-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="4758882748-26">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4758882748-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4758882748-28">(</span><span class="p" data-group-id="4758882748-28">)</span><span class="p" data-group-id="4758882748-27">}</span><span class="p" data-group-id="4758882748-26">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="4758882748-29">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="4758882748-29">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="6824952753-20">(</span><span class="n">Parent</span><span class="p" data-group-id="6824952753-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="6824952753-21">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6824952753-22">(</span><span class="p" data-group-id="6824952753-22">)</span><span class="p" data-group-id="6824952753-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Chs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="6824952753-23">(</span><span class="p" data-group-id="6824952753-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Deb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="6824952753-24">(</span><span class="p" data-group-id="6824952753-25">[</span><span class="p" data-group-id="6824952753-25">]</span><span class="p" data-group-id="6824952753-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="6824952753-26">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6824952753-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6824952753-28">(</span><span class="p" data-group-id="6824952753-28">)</span><span class="p" data-group-id="6824952753-27">}</span><span class="p" data-group-id="6824952753-26">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="6824952753-29">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="6824952753-29">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="4758882748-30">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="4758882748-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="6824952753-30">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="6824952753-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="4758882748-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="4758882748-31">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="4758882748-32">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4758882748-33">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="4758882748-33">}</span><span class="p" data-group-id="4758882748-32">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="4758882748-34">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="4758882748-34">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="4758882748-35">(</span><span class="n">Chs</span><span class="p" data-group-id="4758882748-35">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4758882748-36">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4758882748-36">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">Deb3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="4758882748-37">(</span><span class="n">Deb2</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4758882748-38">{</span><span class="ss">out</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4758882748-39">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4758882748-39">}</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="4758882748-38">}</span><span class="p" data-group-id="4758882748-37">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="4758882748-40">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb3</span><span class="p" data-group-id="4758882748-40">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="4758882748-41">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4758882748-41">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="4758882748-42">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4758882748-43">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4758882748-44">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4758882748-44">}</span><span class="p" data-group-id="4758882748-43">}</span><span class="p" data-group-id="4758882748-42">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="4758882748-45">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4758882748-45">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="4758882748-46">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb2</span><span class="p" data-group-id="4758882748-46">)</span><span class="p">;</span><span class="w">
│ │ │ │ -
│ │ │ │ -        </span><span class="p" data-group-id="4758882748-47">{</span><span class="ss">system</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="4758882748-47">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="4758882748-48">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w">
│ │ │ │ -                                  </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4758882748-48">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="6824952753-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="6824952753-31">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="6824952753-32">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6824952753-33">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="6824952753-33">}</span><span class="p" data-group-id="6824952753-32">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="6824952753-34">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="6824952753-34">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="6824952753-35">(</span><span class="n">Chs</span><span class="p" data-group-id="6824952753-35">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6824952753-36">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="6824952753-36">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">Deb3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="6824952753-37">(</span><span class="n">Deb2</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6824952753-38">{</span><span class="ss">out</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6824952753-39">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="6824952753-39">}</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="6824952753-38">}</span><span class="p" data-group-id="6824952753-37">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="6824952753-40">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb3</span><span class="p" data-group-id="6824952753-40">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="6824952753-41">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="6824952753-41">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="6824952753-42">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6824952753-43">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6824952753-44">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="6824952753-44">}</span><span class="p" data-group-id="6824952753-43">}</span><span class="p" data-group-id="6824952753-42">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="6824952753-45">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6824952753-45">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="6824952753-46">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb2</span><span class="p" data-group-id="6824952753-46">)</span><span class="p">;</span><span class="w">
│ │ │ │ +
│ │ │ │ +        </span><span class="p" data-group-id="6824952753-47">{</span><span class="ss">system</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="6824952753-47">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="6824952753-48">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w">
│ │ │ │ +                                  </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6824952753-48">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_continue</span><span class="p" data-group-id="4758882748-49">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4758882748-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="4758882748-50">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="4758882748-50">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">system_continue</span><span class="p" data-group-id="6824952753-49">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6824952753-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="6824952753-50">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="6824952753-50">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_terminate</span><span class="p" data-group-id="4758882748-51">(</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Chs</span><span class="p" data-group-id="4758882748-51">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">exit</span><span class="p" data-group-id="4758882748-52">(</span><span class="n">Reason</span><span class="p" data-group-id="4758882748-52">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">system_terminate</span><span class="p" data-group-id="6824952753-51">(</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Chs</span><span class="p" data-group-id="6824952753-51">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">exit</span><span class="p" data-group-id="6824952753-52">(</span><span class="n">Reason</span><span class="p" data-group-id="6824952753-52">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_get_state</span><span class="p" data-group-id="4758882748-53">(</span><span class="n">Chs</span><span class="p" data-group-id="4758882748-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4758882748-54">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4758882748-54">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">system_get_state</span><span class="p" data-group-id="6824952753-53">(</span><span class="n">Chs</span><span class="p" data-group-id="6824952753-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6824952753-54">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6824952753-54">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_replace_state</span><span class="p" data-group-id="4758882748-55">(</span><span class="n">StateFun</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4758882748-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">NChs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StateFun</span><span class="p" data-group-id="4758882748-56">(</span><span class="n">Chs</span><span class="p" data-group-id="4758882748-56">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4758882748-57">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p" data-group-id="4758882748-57">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">system_replace_state</span><span class="p" data-group-id="6824952753-55">(</span><span class="n">StateFun</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6824952753-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">NChs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StateFun</span><span class="p" data-group-id="6824952753-56">(</span><span class="n">Chs</span><span class="p" data-group-id="6824952753-56">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6824952753-57">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p" data-group-id="6824952753-57">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">write_debug</span><span class="p" data-group-id="4758882748-58">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="4758882748-58">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4758882748-59">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> event = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4758882748-60">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="4758882748-60">]</span><span class="p" data-group-id="4758882748-59">)</span><span class="p">.</span></code></pre><p id="ex">As it is not relevant to the example, the channel handling functions have been
│ │ │ │ +</span><span class="nf">write_debug</span><span class="p" data-group-id="6824952753-58">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6824952753-58">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6824952753-59">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> event = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6824952753-60">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="6824952753-60">]</span><span class="p" data-group-id="6824952753-59">)</span><span class="p">.</span></code></pre><p id="ex">As it is not relevant to the example, the channel handling functions have been
│ │ │ │  omitted. To compile this example, the
│ │ │ │  <a href="design_principles.xhtml#channels-implementation">implementation of channel handling</a>
│ │ │ │  needs to be added to the module.</p><p>Here is an example showing how the debugging functions in the <code class="inline">sys</code>
│ │ │ │  module can be used for <code class="inline">ch4</code>:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl</span><span class="w">
│ │ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="6109837123-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">15.0</span><span class="p" data-group-id="6109837123-1">]</span><span class="w"> </span><span class="p" data-group-id="6109837123-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="6109837123-2">]</span><span class="w"> </span><span class="p" data-group-id="6109837123-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="6109837123-3">]</span><span class="w"> </span><span class="p" data-group-id="6109837123-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="6109837123-4">]</span><span class="w"> </span><span class="p" data-group-id="6109837123-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="6109837123-5">]</span><span class="w"> </span><span class="p" data-group-id="6109837123-6">[</span><span class="ss">jit</span><span class="p" data-group-id="6109837123-6">]</span><span class="w">
│ │ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="0976470177-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">15.0</span><span class="p" data-group-id="0976470177-1">]</span><span class="w"> </span><span class="p" data-group-id="0976470177-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="0976470177-2">]</span><span class="w"> </span><span class="p" data-group-id="0976470177-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="0976470177-3">]</span><span class="w"> </span><span class="p" data-group-id="0976470177-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="0976470177-4">]</span><span class="w"> </span><span class="p" data-group-id="0976470177-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="0976470177-5">]</span><span class="w"> </span><span class="p" data-group-id="0976470177-6">[</span><span class="ss">jit</span><span class="p" data-group-id="0976470177-6">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V15</span><span class="p">.</span><span class="mi">0</span><span class="w"> </span><span class="p" data-group-id="6109837123-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="6109837123-8">(</span><span class="p" data-group-id="6109837123-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="6109837123-7">)</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="6109837123-9">(</span><span class="p" data-group-id="6109837123-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6109837123-10">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="6109837123-10">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="6109837123-11">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="6109837123-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="6109837123-12">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="6109837123-12">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">alloc</span><span class="p" data-group-id="6109837123-13">(</span><span class="p" data-group-id="6109837123-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6109837123-14">{</span><span class="ss">in</span><span class="p">,</span><span class="ss">alloc</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="6109837123-14">}</span><span class="w">
│ │ │ │ -</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6109837123-15">{</span><span class="ss">out</span><span class="p">,</span><span class="p" data-group-id="6109837123-16">{</span><span class="ss">ch4</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6109837123-16">}</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="6109837123-15">}</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V15</span><span class="p">.</span><span class="mi">0</span><span class="w"> </span><span class="p" data-group-id="0976470177-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="0976470177-8">(</span><span class="p" data-group-id="0976470177-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="0976470177-7">)</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="0976470177-9">(</span><span class="p" data-group-id="0976470177-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0976470177-10">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0976470177-10">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="0976470177-11">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0976470177-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">ok</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="0976470177-12">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0976470177-12">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">ok</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">alloc</span><span class="p" data-group-id="0976470177-13">(</span><span class="p" data-group-id="0976470177-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0976470177-14">{</span><span class="ss">in</span><span class="p">,</span><span class="ss">alloc</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0976470177-14">}</span><span class="w">
│ │ │ │ +</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0976470177-15">{</span><span class="ss">out</span><span class="p">,</span><span class="p" data-group-id="0976470177-16">{</span><span class="ss">ch4</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0976470177-16">}</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0976470177-15">}</span><span class="w">
│ │ │ │  </span><span class="mi">1</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">free</span><span class="p" data-group-id="6109837123-17">(</span><span class="ss">ch1</span><span class="p" data-group-id="6109837123-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6109837123-18">{</span><span class="ss">in</span><span class="p">,</span><span class="p" data-group-id="6109837123-19">{</span><span class="ss">free</span><span class="p">,</span><span class="ss">ch1</span><span class="p" data-group-id="6109837123-19">}</span><span class="p" data-group-id="6109837123-18">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">free</span><span class="p" data-group-id="0976470177-17">(</span><span class="ss">ch1</span><span class="p" data-group-id="0976470177-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0976470177-18">{</span><span class="ss">in</span><span class="p">,</span><span class="p" data-group-id="0976470177-19">{</span><span class="ss">free</span><span class="p">,</span><span class="ss">ch1</span><span class="p" data-group-id="0976470177-19">}</span><span class="p" data-group-id="0976470177-18">}</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="6109837123-20">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="nb">get</span><span class="p" data-group-id="6109837123-20">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6109837123-21">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="6109837123-22">[</span><span class="p" data-group-id="6109837123-23">{</span><span class="ss">start_time</span><span class="p">,</span><span class="p" data-group-id="6109837123-24">{</span><span class="p" data-group-id="6109837123-25">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6109837123-25">}</span><span class="p">,</span><span class="p" data-group-id="6109837123-26">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">26</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="6109837123-26">}</span><span class="p" data-group-id="6109837123-24">}</span><span class="p" data-group-id="6109837123-23">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="6109837123-27">{</span><span class="ss">current_time</span><span class="p">,</span><span class="p" data-group-id="6109837123-28">{</span><span class="p" data-group-id="6109837123-29">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6109837123-29">}</span><span class="p">,</span><span class="p" data-group-id="6109837123-30">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">26</span><span class="p">,</span><span class="mi">49</span><span class="p" data-group-id="6109837123-30">}</span><span class="p" data-group-id="6109837123-28">}</span><span class="p" data-group-id="6109837123-27">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="6109837123-31">{</span><span class="ss">reductions</span><span class="p">,</span><span class="mi">202</span><span class="p" data-group-id="6109837123-31">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="6109837123-32">{</span><span class="ss">messages_in</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6109837123-32">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="6109837123-33">{</span><span class="ss">messages_out</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6109837123-33">}</span><span class="p" data-group-id="6109837123-22">]</span><span class="p" data-group-id="6109837123-21">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">7&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="6109837123-34">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="6109837123-34">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">8&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="6109837123-35">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="6109837123-35">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">9&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">get_status</span><span class="p" data-group-id="6109837123-36">(</span><span class="ss">ch4</span><span class="p" data-group-id="6109837123-36">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6109837123-37">{</span><span class="ss">status</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6109837123-38">{</span><span class="ss">module</span><span class="p">,</span><span class="ss">ch4</span><span class="p" data-group-id="6109837123-38">}</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6109837123-39">[</span><span class="p" data-group-id="6109837123-40">[</span><span class="p" data-group-id="6109837123-41">{</span><span class="ss">&#39;$initial_call&#39;</span><span class="p">,</span><span class="p" data-group-id="6109837123-42">{</span><span class="ss">ch4</span><span class="p">,</span><span class="ss">init</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6109837123-42">}</span><span class="p" data-group-id="6109837123-41">}</span><span class="p">,</span><span class="w">
│ │ │ │ -          </span><span class="p" data-group-id="6109837123-43">{</span><span class="ss">&#39;$ancestors&#39;</span><span class="p">,</span><span class="p" data-group-id="6109837123-44">[</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.87</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.70</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.65</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.69</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ -                         </span><span class="o">&lt;</span><span class="mf">0.64</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">kernel_sup</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.47</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="6109837123-44">]</span><span class="p" data-group-id="6109837123-43">}</span><span class="p" data-group-id="6109837123-40">]</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="ss">running</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="p" data-group-id="6109837123-45">[</span><span class="p" data-group-id="6109837123-45">]</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="6109837123-46">{</span><span class="p" data-group-id="6109837123-47">[</span><span class="mi">1</span><span class="p" data-group-id="6109837123-47">]</span><span class="p">,</span><span class="p" data-group-id="6109837123-48">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">10</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p">,</span><span class="mi">14</span><span class="p">,</span><span class="mi">15</span><span class="p">,</span><span class="mi">16</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">18</span><span class="p">,</span><span class="mi">19</span><span class="p">|</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6109837123-48">]</span><span class="p" data-group-id="6109837123-46">}</span><span class="p" data-group-id="6109837123-39">]</span><span class="p" data-group-id="6109837123-37">}</span></code></pre><h3 id="starting-the-process" class="section-heading">
│ │ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="0976470177-20">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="nb">get</span><span class="p" data-group-id="0976470177-20">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0976470177-21">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="0976470177-22">[</span><span class="p" data-group-id="0976470177-23">{</span><span class="ss">start_time</span><span class="p">,</span><span class="p" data-group-id="0976470177-24">{</span><span class="p" data-group-id="0976470177-25">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0976470177-25">}</span><span class="p">,</span><span class="p" data-group-id="0976470177-26">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">26</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="0976470177-26">}</span><span class="p" data-group-id="0976470177-24">}</span><span class="p" data-group-id="0976470177-23">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="0976470177-27">{</span><span class="ss">current_time</span><span class="p">,</span><span class="p" data-group-id="0976470177-28">{</span><span class="p" data-group-id="0976470177-29">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0976470177-29">}</span><span class="p">,</span><span class="p" data-group-id="0976470177-30">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">26</span><span class="p">,</span><span class="mi">49</span><span class="p" data-group-id="0976470177-30">}</span><span class="p" data-group-id="0976470177-28">}</span><span class="p" data-group-id="0976470177-27">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="0976470177-31">{</span><span class="ss">reductions</span><span class="p">,</span><span class="mi">202</span><span class="p" data-group-id="0976470177-31">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="0976470177-32">{</span><span class="ss">messages_in</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0976470177-32">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="0976470177-33">{</span><span class="ss">messages_out</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0976470177-33">}</span><span class="p" data-group-id="0976470177-22">]</span><span class="p" data-group-id="0976470177-21">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">7&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="0976470177-34">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="0976470177-34">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">ok</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">8&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="0976470177-35">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="0976470177-35">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">ok</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">9&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">get_status</span><span class="p" data-group-id="0976470177-36">(</span><span class="ss">ch4</span><span class="p" data-group-id="0976470177-36">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0976470177-37">{</span><span class="ss">status</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0976470177-38">{</span><span class="ss">module</span><span class="p">,</span><span class="ss">ch4</span><span class="p" data-group-id="0976470177-38">}</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0976470177-39">[</span><span class="p" data-group-id="0976470177-40">[</span><span class="p" data-group-id="0976470177-41">{</span><span class="ss">&#39;$initial_call&#39;</span><span class="p">,</span><span class="p" data-group-id="0976470177-42">{</span><span class="ss">ch4</span><span class="p">,</span><span class="ss">init</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0976470177-42">}</span><span class="p" data-group-id="0976470177-41">}</span><span class="p">,</span><span class="w">
│ │ │ │ +          </span><span class="p" data-group-id="0976470177-43">{</span><span class="ss">&#39;$ancestors&#39;</span><span class="p">,</span><span class="p" data-group-id="0976470177-44">[</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.87</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.70</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.65</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.69</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ +                         </span><span class="o">&lt;</span><span class="mf">0.64</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">kernel_sup</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.47</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0976470177-44">]</span><span class="p" data-group-id="0976470177-43">}</span><span class="p" data-group-id="0976470177-40">]</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="ss">running</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="p" data-group-id="0976470177-45">[</span><span class="p" data-group-id="0976470177-45">]</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="0976470177-46">{</span><span class="p" data-group-id="0976470177-47">[</span><span class="mi">1</span><span class="p" data-group-id="0976470177-47">]</span><span class="p">,</span><span class="p" data-group-id="0976470177-48">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">10</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p">,</span><span class="mi">14</span><span class="p">,</span><span class="mi">15</span><span class="p">,</span><span class="mi">16</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">18</span><span class="p">,</span><span class="mi">19</span><span class="p">|</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0976470177-48">]</span><span class="p" data-group-id="0976470177-46">}</span><span class="p" data-group-id="0976470177-39">]</span><span class="p" data-group-id="0976470177-37">}</span></code></pre><h3 id="starting-the-process" class="section-heading">
│ │ │ │    <a href="#starting-the-process" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Starting the Process</span>
│ │ │ │  </h3>
│ │ │ │  <p>A function in the <a href="../../../lib/stdlib/doc/html/proc_lib.html"><code class="inline">proc_lib</code></a> module is to be used to start the process. Several
│ │ │ │  functions are available, for example,
│ │ │ │  <a href="../../../lib/stdlib/doc/html/proc_lib.html#spawn_link/4"><code class="inline">proc_lib:spawn_link/3,4</code></a>
│ │ │ │  for asynchronous start and
│ │ │ │  <a href="../../../lib/stdlib/doc/html/proc_lib.html#start_link/5"><code class="inline">proc_lib:start_link/3,4,5</code></a> for synchronous start.</p><p>Information necessary for a process within a supervision tree, such as
│ │ │ │  details on ancestors and the initial call, is stored when a process
│ │ │ │  is started through one of these functions.</p><p>If the process terminates with a reason other than <code class="inline">normal</code> or <code class="inline">shutdown</code>, a
│ │ │ │  crash report is generated. For more information about the crash report, see
│ │ │ │  <a href="../../../lib/kernel/doc/html/logger_chapter.xhtml">Logging</a> in Kernel User's Guide.</p><p>In the example, synchronous start is used. The process starts by calling
│ │ │ │ -<code class="inline">ch4:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="2811471378-1">(</span><span class="p" data-group-id="2811471378-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="2811471378-2">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2811471378-3">[</span><span class="nf">self</span><span class="p" data-group-id="2811471378-4">(</span><span class="p" data-group-id="2811471378-4">)</span><span class="p" data-group-id="2811471378-3">]</span><span class="p" data-group-id="2811471378-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch4:start_link/0</code> calls <a href="../../../lib/stdlib/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a>, which takes a module
│ │ │ │ +<code class="inline">ch4:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="7275617884-1">(</span><span class="p" data-group-id="7275617884-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="7275617884-2">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7275617884-3">[</span><span class="nf">self</span><span class="p" data-group-id="7275617884-4">(</span><span class="p" data-group-id="7275617884-4">)</span><span class="p" data-group-id="7275617884-3">]</span><span class="p" data-group-id="7275617884-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch4:start_link/0</code> calls <a href="../../../lib/stdlib/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a>, which takes a module
│ │ │ │  name, a function name, and an argument list as arguments. It then
│ │ │ │  spawns a new process and establishes a link. The new process starts
│ │ │ │  by executing the given function, here <code class="inline">ch4:init(Pid)</code>, where <code class="inline">Pid</code> is
│ │ │ │  the pid of the parent process (obtained by the call to
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#self/0"><code class="inline">self()</code></a> in the call to <a href="../../../lib/stdlib/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a>).</p><p>All initialization, including name registration, is done in <code class="inline">init/1</code>. The new
│ │ │ │ -process has to acknowledge that it has been started to the parent:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="7648332382-1">(</span><span class="n">Parent</span><span class="p" data-group-id="7648332382-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +process has to acknowledge that it has been started to the parent:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="7360429268-1">(</span><span class="n">Parent</span><span class="p" data-group-id="7360429268-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="7648332382-2">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7648332382-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7648332382-4">(</span><span class="p" data-group-id="7648332382-4">)</span><span class="p" data-group-id="7648332382-3">}</span><span class="p" data-group-id="7648332382-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="7648332382-5">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7648332382-5">)</span><span class="p">.</span></code></pre><p><a href="../../../lib/stdlib/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a> is synchronous and does not return until
│ │ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="7360429268-2">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7360429268-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7360429268-4">(</span><span class="p" data-group-id="7360429268-4">)</span><span class="p" data-group-id="7360429268-3">}</span><span class="p" data-group-id="7360429268-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="7360429268-5">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7360429268-5">)</span><span class="p">.</span></code></pre><p><a href="../../../lib/stdlib/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a> is synchronous and does not return until
│ │ │ │  <a href="../../../lib/stdlib/doc/html/proc_lib.html#init_ack/2"><code class="inline">proc_lib:init_ack/1,2</code></a> or
│ │ │ │  <a href="../../../lib/stdlib/doc/html/proc_lib.html#init_fail/3"><code class="inline">proc_lib:init_fail/2,3</code></a> has been called,
│ │ │ │  or the process has exited.</p><p><a href="" id="debug"></a></p><h3 id="debugging" class="section-heading">
│ │ │ │    <a href="#debugging" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Debugging</span>
│ │ │ │  </h3>
│ │ │ │  <p>To support the debug facilities in <code class="inline">sys</code>, a <em>debug structure</em> is needed. The
│ │ │ │ -<code class="inline">Deb</code> term is initialized using <a href="../../../lib/stdlib/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="0586701803-1">(</span><span class="n">Parent</span><span class="p" data-group-id="0586701803-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +<code class="inline">Deb</code> term is initialized using <a href="../../../lib/stdlib/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="7507232397-1">(</span><span class="n">Parent</span><span class="p" data-group-id="7507232397-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="n">Deb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="0586701803-2">(</span><span class="p" data-group-id="0586701803-3">[</span><span class="p" data-group-id="0586701803-3">]</span><span class="p" data-group-id="0586701803-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Deb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="7507232397-2">(</span><span class="p" data-group-id="7507232397-3">[</span><span class="p" data-group-id="7507232397-3">]</span><span class="p" data-group-id="7507232397-2">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="0586701803-4">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="0586701803-4">)</span><span class="p">.</span></code></pre><p><a href="../../../lib/stdlib/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a> takes a list of options. Given an empty list as in this
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="7507232397-4">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="7507232397-4">)</span><span class="p">.</span></code></pre><p><a href="../../../lib/stdlib/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a> takes a list of options. Given an empty list as in this
│ │ │ │  example means that debugging is initially disabled. For information about the
│ │ │ │  possible options, see <a href="../../../lib/stdlib/doc/html/sys.html"><code class="inline">sys</code></a> in STDLIB.</p><p>For each <em>system event</em> to be logged or traced, the following function
│ │ │ │ -is to be called:</p><pre><code class="makeup erlang" translate="no"><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="8739303623-1">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Func</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="8739303623-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Deb1</span></code></pre><p>The arguments have the following meaning:</p><ul><li><code class="inline">Deb</code> is the debug structure as returned from <a href="../../../lib/stdlib/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a>.</li><li><code class="inline">Func</code> is a fun specifying a (user-defined) function used to format trace
│ │ │ │ +is to be called:</p><pre><code class="makeup erlang" translate="no"><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="6723005196-1">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Func</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="6723005196-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Deb1</span></code></pre><p>The arguments have the following meaning:</p><ul><li><code class="inline">Deb</code> is the debug structure as returned from <a href="../../../lib/stdlib/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a>.</li><li><code class="inline">Func</code> is a fun specifying a (user-defined) function used to format trace
│ │ │ │  output. For each system event, the format function is called as
│ │ │ │  <code class="inline">Func(Dev, Event, Info)</code>, where:<ul><li><code class="inline">Dev</code> is the I/O device to which the output is to be printed. See <a href="../../../lib/stdlib/doc/html/io.html"><code class="inline">io</code></a>
│ │ │ │  in STDLIB.</li><li><code class="inline">Event</code> and <code class="inline">Info</code> are passed as-is from the call to <a href="../../../lib/stdlib/doc/html/sys.html#handle_debug/4"><code class="inline">sys:handle_debug/4</code></a>.</li></ul></li><li><code class="inline">Info</code> is used to pass more information to <code class="inline">Func</code>. It can be any term, and it
│ │ │ │  is passed as-is.</li><li><code class="inline">Event</code> is the system event. It is up to the user to define what a system
│ │ │ │  event is and how it is to be represented. Typically, at least incoming and
│ │ │ │  outgoing messages are considered system events and represented by the tuples
│ │ │ │  <code class="inline">{in,Msg[,From]}</code> and <code class="inline">{out,Msg,To[,State]}</code>, respectively.</li></ul><p><a href="../../../lib/stdlib/doc/html/sys.html#handle_debug/4"><code class="inline">sys:handle_debug/4</code></a> returns an updated debug structure <code class="inline">Deb1</code>.</p><p>In the example, <a href="../../../lib/stdlib/doc/html/sys.html#handle_debug/4"><code class="inline">sys:handle_debug/4</code></a> is called for each incoming and
│ │ │ │  outgoing message. The format function <code class="inline">Func</code> is the function
│ │ │ │ -<code class="inline">ch4:write_debug/3</code>, which prints the message using <a href="../../../lib/stdlib/doc/html/io.html#format/3"><code class="inline">io:format/3</code></a>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="8805414693-1">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="8805414693-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +<code class="inline">ch4:write_debug/3</code>, which prints the message using <a href="../../../lib/stdlib/doc/html/io.html#format/3"><code class="inline">io:format/3</code></a>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="5190701284-1">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="5190701284-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8805414693-2">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="8805414693-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="8805414693-3">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8805414693-4">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="8805414693-4">}</span><span class="p" data-group-id="8805414693-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="8805414693-5">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="8805414693-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="8805414693-6">(</span><span class="n">Chs</span><span class="p" data-group-id="8805414693-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8805414693-7">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="8805414693-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">Deb3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="8805414693-8">(</span><span class="n">Deb2</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8805414693-9">{</span><span class="ss">out</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8805414693-10">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="8805414693-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="8805414693-9">}</span><span class="p" data-group-id="8805414693-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="8805414693-11">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb3</span><span class="p" data-group-id="8805414693-11">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8805414693-12">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="8805414693-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="8805414693-13">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8805414693-14">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8805414693-15">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="8805414693-15">}</span><span class="p" data-group-id="8805414693-14">}</span><span class="p" data-group-id="8805414693-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="8805414693-16">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="8805414693-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="8805414693-17">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb2</span><span class="p" data-group-id="8805414693-17">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="5190701284-2">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="5190701284-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="5190701284-3">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5190701284-4">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="5190701284-4">}</span><span class="p" data-group-id="5190701284-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="5190701284-5">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="5190701284-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="5190701284-6">(</span><span class="n">Chs</span><span class="p" data-group-id="5190701284-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5190701284-7">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="5190701284-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">Deb3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="5190701284-8">(</span><span class="n">Deb2</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5190701284-9">{</span><span class="ss">out</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5190701284-10">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="5190701284-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="5190701284-9">}</span><span class="p" data-group-id="5190701284-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="5190701284-11">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb3</span><span class="p" data-group-id="5190701284-11">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="5190701284-12">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="5190701284-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="5190701284-13">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5190701284-14">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5190701284-15">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="5190701284-15">}</span><span class="p" data-group-id="5190701284-14">}</span><span class="p" data-group-id="5190701284-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="5190701284-16">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="5190701284-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="5190701284-17">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb2</span><span class="p" data-group-id="5190701284-17">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">write_debug</span><span class="p" data-group-id="8805414693-18">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="8805414693-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8805414693-19">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> event = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8805414693-20">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="8805414693-20">]</span><span class="p" data-group-id="8805414693-19">)</span><span class="p">.</span></code></pre><p><a href="" id="msg"></a></p><h3 id="handling-system-messages" class="section-heading">
│ │ │ │ +</span><span class="nf">write_debug</span><span class="p" data-group-id="5190701284-18">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5190701284-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5190701284-19">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> event = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5190701284-20">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="5190701284-20">]</span><span class="p" data-group-id="5190701284-19">)</span><span class="p">.</span></code></pre><p><a href="" id="msg"></a></p><h3 id="handling-system-messages" class="section-heading">
│ │ │ │    <a href="#handling-system-messages" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Handling System Messages</span>
│ │ │ │  </h3>
│ │ │ │  <p><em>System messages</em> are received as:</p><pre><code class="text">{system, From, Request}</code></pre><p>The content and meaning of these messages are not to be interpreted by the
│ │ │ │ -process. Instead the following function is to be called:</p><pre><code class="makeup erlang" translate="no"><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="1415613735-1">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="1415613735-1">)</span></code></pre><p>The arguments have the following meaning:</p><ul><li><code class="inline">Request</code> and <code class="inline">From</code> from the received system message are to be
│ │ │ │ +process. Instead the following function is to be called:</p><pre><code class="makeup erlang" translate="no"><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="2253728851-1">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2253728851-1">)</span></code></pre><p>The arguments have the following meaning:</p><ul><li><code class="inline">Request</code> and <code class="inline">From</code> from the received system message are to be
│ │ │ │  passed as-is to the call to <a href="../../../lib/stdlib/doc/html/sys.html#handle_system_msg/6"><code class="inline">sys:handle_system_msg/6</code></a>.</li><li><code class="inline">Parent</code> is the pid of the parent process.</li><li><code class="inline">Module</code> is the name of the module implementing the special process.</li><li><code class="inline">Deb</code> is the debug structure.</li><li><code class="inline">State</code> is a term describing the internal state and is passed on to
│ │ │ │  <code class="inline">Module:system_continue/3</code>, <code class="inline">Module:system_terminate/4</code>,
│ │ │ │  <code class="inline">Module:system_get_state/1</code>, and <code class="inline">Module:system_replace_state/2</code>.</li></ul><p><a href="../../../lib/stdlib/doc/html/sys.html#handle_system_msg/6"><code class="inline">sys:handle_system_msg/6</code></a> does not return. It handles the system
│ │ │ │  message and <em>eventually</em> calls either of the following functions:</p><ul><li><p><code class="inline">Module:system_continue(Parent, Deb, State)</code> - if process execution is to
│ │ │ │  continue.</p></li><li><p><code class="inline">Module:system_terminate(Reason, Parent, Deb, State)</code> - if the
│ │ │ │  process is to terminate.</p></li></ul><p>While handling the system message, <a href="../../../lib/stdlib/doc/html/sys.html#handle_system_msg/6"><code class="inline">sys:handle_system_msg/6</code></a> can call
│ │ │ │  one of the following functions:</p><ul><li><p><code class="inline">Module:system_get_state(State)</code> - if the process is to return its state.</p></li><li><p><code class="inline">Module:system_replace_state(StateFun, State)</code> - if the process is
│ │ │ │  to replace its state using the fun <code class="inline">StateFun</code>. See <a href="../../../lib/stdlib/doc/html/sys.html#replace_state/3"><code class="inline">sys:replace_state/3</code></a>
│ │ │ │  for more information.</p></li><li><p><code class="inline">system_code_change(Misc, Module, OldVsn, Extra)</code> - if the process is to
│ │ │ │  perform a code change.</p></li></ul><p>A process in a supervision tree is expected to terminate with the same reason as
│ │ │ │ -its parent.</p><p>In the example, system messages are handled by the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="6599516189-1">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="6599516189-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +its parent.</p><p>In the example, system messages are handled by the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="6817269141-1">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="6817269141-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -        </span><span class="p" data-group-id="6599516189-2">{</span><span class="ss">system</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="6599516189-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="6599516189-3">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w">
│ │ │ │ -                                  </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6599516189-3">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="6817269141-2">{</span><span class="ss">system</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="6817269141-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="6817269141-3">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w">
│ │ │ │ +                                  </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6817269141-3">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_continue</span><span class="p" data-group-id="6599516189-4">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6599516189-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="6599516189-5">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="6599516189-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">system_continue</span><span class="p" data-group-id="6817269141-4">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6817269141-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="6817269141-5">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="6817269141-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_terminate</span><span class="p" data-group-id="6599516189-6">(</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6599516189-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">exit</span><span class="p" data-group-id="6599516189-7">(</span><span class="n">Reason</span><span class="p" data-group-id="6599516189-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">system_terminate</span><span class="p" data-group-id="6817269141-6">(</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6817269141-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">exit</span><span class="p" data-group-id="6817269141-7">(</span><span class="n">Reason</span><span class="p" data-group-id="6817269141-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_get_state</span><span class="p" data-group-id="6599516189-8">(</span><span class="n">Chs</span><span class="p" data-group-id="6599516189-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6599516189-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6599516189-9">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">system_get_state</span><span class="p" data-group-id="6817269141-8">(</span><span class="n">Chs</span><span class="p" data-group-id="6817269141-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6817269141-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6817269141-9">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_replace_state</span><span class="p" data-group-id="6599516189-10">(</span><span class="n">StateFun</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6599516189-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">NChs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StateFun</span><span class="p" data-group-id="6599516189-11">(</span><span class="n">Chs</span><span class="p" data-group-id="6599516189-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6599516189-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p" data-group-id="6599516189-12">}</span><span class="p">.</span></code></pre><p>If a special process is configured to trap exits, it must take notice
│ │ │ │ +</span><span class="nf">system_replace_state</span><span class="p" data-group-id="6817269141-10">(</span><span class="n">StateFun</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6817269141-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">NChs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StateFun</span><span class="p" data-group-id="6817269141-11">(</span><span class="n">Chs</span><span class="p" data-group-id="6817269141-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6817269141-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p" data-group-id="6817269141-12">}</span><span class="p">.</span></code></pre><p>If a special process is configured to trap exits, it must take notice
│ │ │ │  of 'EXIT' messages from its parent process and terminate using the
│ │ │ │ -same exit reason once the parent process has terminated.</p><p>Here is an example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="8240444424-1">(</span><span class="n">Parent</span><span class="p" data-group-id="8240444424-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +same exit reason once the parent process has terminated.</p><p>Here is an example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="7541113230-1">(</span><span class="n">Parent</span><span class="p" data-group-id="7541113230-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="8240444424-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="8240444424-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="7541113230-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="7541113230-2">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="8240444424-3">(</span><span class="n">Parent</span><span class="p" data-group-id="8240444424-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="7541113230-3">(</span><span class="n">Parent</span><span class="p" data-group-id="7541113230-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="8240444424-4">(</span><span class="n">Parent</span><span class="p" data-group-id="8240444424-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="7541113230-4">(</span><span class="n">Parent</span><span class="p" data-group-id="7541113230-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8240444424-5">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="8240444424-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="7541113230-5">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="7541113230-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="c1">%% Clean up here, if needed.</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="8240444424-6">(</span><span class="n">Reason</span><span class="p" data-group-id="8240444424-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="7541113230-6">(</span><span class="n">Reason</span><span class="p" data-group-id="7541113230-6">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><h2 id="user-defined-behaviours" class="section-heading">
│ │ │ │    <a href="#user-defined-behaviours" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">User-Defined Behaviours</span>
│ │ │ │  </h2>
│ │ │ │ @@ -353,69 +353,69 @@
│ │ │ │  function. Note that the <code class="inline">-optional_callbacks</code> attribute is to be used together
│ │ │ │  with the <code class="inline">-callback</code> attribute; it cannot be combined with the
│ │ │ │  <code class="inline">behaviour_info()</code> function described below.</p><p>Tools that need to know about optional callback functions can call
│ │ │ │  <code class="inline">Behaviour:behaviour_info(optional_callbacks)</code> to get a list of all optional
│ │ │ │  callback functions.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>We recommend using the <code class="inline">-callback</code> attribute rather than the
│ │ │ │  <code class="inline">behaviour_info()</code> function. The reason is that the extra type information can
│ │ │ │  be used by tools to produce documentation or find discrepancies.</p></section><p>As an alternative to the <code class="inline">-callback</code> and <code class="inline">-optional_callbacks</code> attributes you
│ │ │ │ -may directly implement and export <code class="inline">behaviour_info()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">behaviour_info</span><span class="p" data-group-id="5418477102-1">(</span><span class="ss">callbacks</span><span class="p" data-group-id="5418477102-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5418477102-2">[</span><span class="p" data-group-id="5418477102-3">{</span><span class="n">Name1</span><span class="p">,</span><span class="w"> </span><span class="n">Arity1</span><span class="p" data-group-id="5418477102-3">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="p" data-group-id="5418477102-4">{</span><span class="n">NameN</span><span class="p">,</span><span class="w"> </span><span class="n">ArityN</span><span class="p" data-group-id="5418477102-4">}</span><span class="p" data-group-id="5418477102-2">]</span><span class="p">.</span></code></pre><p>where each <code class="inline">{Name, Arity}</code> specifies the name and arity of a callback function.
│ │ │ │ +may directly implement and export <code class="inline">behaviour_info()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">behaviour_info</span><span class="p" data-group-id="3032725460-1">(</span><span class="ss">callbacks</span><span class="p" data-group-id="3032725460-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3032725460-2">[</span><span class="p" data-group-id="3032725460-3">{</span><span class="n">Name1</span><span class="p">,</span><span class="w"> </span><span class="n">Arity1</span><span class="p" data-group-id="3032725460-3">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="p" data-group-id="3032725460-4">{</span><span class="n">NameN</span><span class="p">,</span><span class="w"> </span><span class="n">ArityN</span><span class="p" data-group-id="3032725460-4">}</span><span class="p" data-group-id="3032725460-2">]</span><span class="p">.</span></code></pre><p>where each <code class="inline">{Name, Arity}</code> specifies the name and arity of a callback function.
│ │ │ │  This function is otherwise automatically generated by the compiler using the
│ │ │ │  <code class="inline">-callback</code> attributes.</p><p>When the compiler encounters the module attribute <code class="inline">-behaviour(Behaviour).</code> in a
│ │ │ │  module <code class="inline">Mod</code>, it calls <code class="inline">Behaviour:behaviour_info(callbacks)</code> and compares the
│ │ │ │  result with the set of functions actually exported from <code class="inline">Mod</code>, and issues a
│ │ │ │  warning if any callback function is missing.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% User-defined behaviour module</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8316485760-1">(</span><span class="ss">simple_server</span><span class="p" data-group-id="8316485760-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8316485760-2">(</span><span class="p" data-group-id="8316485760-3">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8316485760-3">]</span><span class="p" data-group-id="8316485760-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3158520897-1">(</span><span class="ss">simple_server</span><span class="p" data-group-id="3158520897-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3158520897-2">(</span><span class="p" data-group-id="3158520897-3">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3158520897-3">]</span><span class="p" data-group-id="3158520897-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">init</span><span class="p" data-group-id="8316485760-4">(</span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8316485760-5">(</span><span class="p" data-group-id="8316485760-5">)</span><span class="p" data-group-id="8316485760-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">&#39;ok&#39;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">handle_req</span><span class="p" data-group-id="8316485760-6">(</span><span class="n">Req</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8316485760-7">(</span><span class="p" data-group-id="8316485760-7">)</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8316485760-8">(</span><span class="p" data-group-id="8316485760-8">)</span><span class="p" data-group-id="8316485760-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8316485760-9">{</span><span class="ss">&#39;ok&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8316485760-10">(</span><span class="p" data-group-id="8316485760-10">)</span><span class="p" data-group-id="8316485760-9">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">terminate</span><span class="p" data-group-id="8316485760-11">(</span><span class="p" data-group-id="8316485760-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">&#39;ok&#39;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">format_state</span><span class="p" data-group-id="8316485760-12">(</span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8316485760-13">(</span><span class="p" data-group-id="8316485760-13">)</span><span class="p" data-group-id="8316485760-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8316485760-14">(</span><span class="p" data-group-id="8316485760-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">init</span><span class="p" data-group-id="3158520897-4">(</span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="3158520897-5">(</span><span class="p" data-group-id="3158520897-5">)</span><span class="p" data-group-id="3158520897-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">&#39;ok&#39;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">handle_req</span><span class="p" data-group-id="3158520897-6">(</span><span class="n">Req</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="3158520897-7">(</span><span class="p" data-group-id="3158520897-7">)</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="3158520897-8">(</span><span class="p" data-group-id="3158520897-8">)</span><span class="p" data-group-id="3158520897-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3158520897-9">{</span><span class="ss">&#39;ok&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="3158520897-10">(</span><span class="p" data-group-id="3158520897-10">)</span><span class="p" data-group-id="3158520897-9">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">terminate</span><span class="p" data-group-id="3158520897-11">(</span><span class="p" data-group-id="3158520897-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">&#39;ok&#39;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">format_state</span><span class="p" data-group-id="3158520897-12">(</span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="3158520897-13">(</span><span class="p" data-group-id="3158520897-13">)</span><span class="p" data-group-id="3158520897-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="3158520897-14">(</span><span class="p" data-group-id="3158520897-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">optional_callbacks</span><span class="p" data-group-id="8316485760-15">(</span><span class="p" data-group-id="8316485760-16">[</span><span class="ss">format_state</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8316485760-16">]</span><span class="p" data-group-id="8316485760-15">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">optional_callbacks</span><span class="p" data-group-id="3158520897-15">(</span><span class="p" data-group-id="3158520897-16">[</span><span class="ss">format_state</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3158520897-16">]</span><span class="p" data-group-id="3158520897-15">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% Alternatively you may define:</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │  </span><span class="c1">%% -export([behaviour_info/1]).</span><span class="w">
│ │ │ │  </span><span class="c1">%% behaviour_info(callbacks) -&gt;</span><span class="w">
│ │ │ │  </span><span class="c1">%%     [{init,1},</span><span class="w">
│ │ │ │  </span><span class="c1">%%      {handle_req,2},</span><span class="w">
│ │ │ │  </span><span class="c1">%%      {terminate,0}].</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="8316485760-17">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="8316485760-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="8316485760-18">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8316485760-19">[</span><span class="nf">self</span><span class="p" data-group-id="8316485760-20">(</span><span class="p" data-group-id="8316485760-20">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="8316485760-19">]</span><span class="p" data-group-id="8316485760-18">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="3158520897-17">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="3158520897-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="3158520897-18">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3158520897-19">[</span><span class="nf">self</span><span class="p" data-group-id="3158520897-20">(</span><span class="p" data-group-id="3158520897-20">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="3158520897-19">]</span><span class="p" data-group-id="3158520897-18">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="8316485760-21">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="8316485760-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="8316485760-22">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8316485760-23">(</span><span class="p" data-group-id="8316485760-23">)</span><span class="p" data-group-id="8316485760-22">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="3158520897-21">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="3158520897-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="3158520897-22">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3158520897-23">(</span><span class="p" data-group-id="3158520897-23">)</span><span class="p" data-group-id="3158520897-22">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Dbg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="8316485760-24">(</span><span class="p" data-group-id="8316485760-25">[</span><span class="p" data-group-id="8316485760-25">]</span><span class="p" data-group-id="8316485760-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="8316485760-26">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8316485760-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8316485760-28">(</span><span class="p" data-group-id="8316485760-28">)</span><span class="p" data-group-id="8316485760-27">}</span><span class="p" data-group-id="8316485760-26">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="8316485760-29">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Dbg</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8316485760-29">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="n">Dbg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="3158520897-24">(</span><span class="p" data-group-id="3158520897-25">[</span><span class="p" data-group-id="3158520897-25">]</span><span class="p" data-group-id="3158520897-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="3158520897-26">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3158520897-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3158520897-28">(</span><span class="p" data-group-id="3158520897-28">)</span><span class="p" data-group-id="3158520897-27">}</span><span class="p" data-group-id="3158520897-26">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="3158520897-29">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Dbg</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3158520897-29">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>In a callback module:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2846638308-1">(</span><span class="ss">db</span><span class="p" data-group-id="2846638308-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="2846638308-2">(</span><span class="ss">simple_server</span><span class="p" data-group-id="2846638308-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>In a callback module:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6317412164-1">(</span><span class="ss">db</span><span class="p" data-group-id="6317412164-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="6317412164-2">(</span><span class="ss">simple_server</span><span class="p" data-group-id="6317412164-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2846638308-3">(</span><span class="p" data-group-id="2846638308-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_req</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2846638308-4">]</span><span class="p" data-group-id="2846638308-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6317412164-3">(</span><span class="p" data-group-id="6317412164-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_req</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6317412164-4">]</span><span class="p" data-group-id="6317412164-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>The contracts specified with <code class="inline">-callback</code> attributes in behaviour modules can be
│ │ │ │  further refined by adding <code class="inline">-spec</code> attributes in callback modules. This can be
│ │ │ │  useful as <code class="inline">-callback</code> contracts are usually generic. The same callback module
│ │ │ │ -with contracts for the callbacks:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9465597710-1">(</span><span class="ss">db</span><span class="p" data-group-id="9465597710-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="9465597710-2">(</span><span class="ss">simple_server</span><span class="p" data-group-id="9465597710-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +with contracts for the callbacks:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6853577453-1">(</span><span class="ss">db</span><span class="p" data-group-id="6853577453-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="6853577453-2">(</span><span class="ss">simple_server</span><span class="p" data-group-id="6853577453-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9465597710-3">(</span><span class="p" data-group-id="9465597710-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_req</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9465597710-4">]</span><span class="p" data-group-id="9465597710-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6853577453-3">(</span><span class="p" data-group-id="6853577453-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_req</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6853577453-4">]</span><span class="p" data-group-id="6853577453-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9465597710-5">(</span><span class="ss">state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9465597710-6">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="9465597710-7">[</span><span class="nf">atom</span><span class="p" data-group-id="9465597710-8">(</span><span class="p" data-group-id="9465597710-8">)</span><span class="p" data-group-id="9465597710-7">]</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="9465597710-9">(</span><span class="p" data-group-id="9465597710-9">)</span><span class="p" data-group-id="9465597710-6">}</span><span class="p" data-group-id="9465597710-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6853577453-5">(</span><span class="ss">state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6853577453-6">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="6853577453-7">[</span><span class="nf">atom</span><span class="p" data-group-id="6853577453-8">(</span><span class="p" data-group-id="6853577453-8">)</span><span class="p" data-group-id="6853577453-7">]</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="6853577453-9">(</span><span class="p" data-group-id="6853577453-9">)</span><span class="p" data-group-id="6853577453-6">}</span><span class="p" data-group-id="6853577453-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">state</span><span class="p" data-group-id="9465597710-10">(</span><span class="p" data-group-id="9465597710-10">)</span><span class="w">   </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="9465597710-11">{</span><span class="p" data-group-id="9465597710-11">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">request</span><span class="p" data-group-id="9465597710-12">(</span><span class="p" data-group-id="9465597710-12">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="9465597710-13">{</span><span class="ss">&#39;store&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="9465597710-14">(</span><span class="p" data-group-id="9465597710-14">)</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="9465597710-15">(</span><span class="p" data-group-id="9465597710-15">)</span><span class="p" data-group-id="9465597710-13">}</span><span class="p">;</span><span class="w">
│ │ │ │ -                   </span><span class="p" data-group-id="9465597710-16">{</span><span class="ss">&#39;lookup&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="9465597710-17">(</span><span class="p" data-group-id="9465597710-17">)</span><span class="p" data-group-id="9465597710-16">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">state</span><span class="p" data-group-id="6853577453-10">(</span><span class="p" data-group-id="6853577453-10">)</span><span class="w">   </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="6853577453-11">{</span><span class="p" data-group-id="6853577453-11">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">request</span><span class="p" data-group-id="6853577453-12">(</span><span class="p" data-group-id="6853577453-12">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="6853577453-13">{</span><span class="ss">&#39;store&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="6853577453-14">(</span><span class="p" data-group-id="6853577453-14">)</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="6853577453-15">(</span><span class="p" data-group-id="6853577453-15">)</span><span class="p" data-group-id="6853577453-13">}</span><span class="p">;</span><span class="w">
│ │ │ │ +                   </span><span class="p" data-group-id="6853577453-16">{</span><span class="ss">&#39;lookup&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="6853577453-17">(</span><span class="p" data-group-id="6853577453-17">)</span><span class="p" data-group-id="6853577453-16">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">handle_req</span><span class="p" data-group-id="9465597710-18">(</span><span class="nf">request</span><span class="p" data-group-id="9465597710-19">(</span><span class="p" data-group-id="9465597710-19">)</span><span class="p">,</span><span class="w"> </span><span class="nf">state</span><span class="p" data-group-id="9465597710-20">(</span><span class="p" data-group-id="9465597710-20">)</span><span class="p" data-group-id="9465597710-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9465597710-21">{</span><span class="ss">&#39;ok&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="9465597710-22">(</span><span class="p" data-group-id="9465597710-22">)</span><span class="p" data-group-id="9465597710-21">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">handle_req</span><span class="p" data-group-id="6853577453-18">(</span><span class="nf">request</span><span class="p" data-group-id="6853577453-19">(</span><span class="p" data-group-id="6853577453-19">)</span><span class="p">,</span><span class="w"> </span><span class="nf">state</span><span class="p" data-group-id="6853577453-20">(</span><span class="p" data-group-id="6853577453-20">)</span><span class="p" data-group-id="6853577453-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6853577453-21">{</span><span class="ss">&#39;ok&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="6853577453-22">(</span><span class="p" data-group-id="6853577453-22">)</span><span class="p" data-group-id="6853577453-21">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Each <code class="inline">-spec</code> contract is to be a subtype of the respective <code class="inline">-callback</code> contract.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/seq_prog.xhtml
│ │ │ │ @@ -41,293 +41,293 @@
│ │ │ │  </span><span class="mi">7</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">2&gt; </span></code></pre><p>As shown, the Erlang shell numbers the lines that can be entered (as <code class="inline">1&gt;</code>, <code class="inline">2&gt;</code>, ...)
│ │ │ │  and correctly says that 2 + 5 is 7. If you make writing mistakes in the
│ │ │ │  shell, you can delete with the backspace key, as in most shells. There are many
│ │ │ │  more editing commands in the shell (see
│ │ │ │  <a href="../../../lib/../erts/doc/html/tty.xhtml">tty - A command line interface</a> in ERTS User's Guide).</p><p>(Notice that many line numbers given by the shell in the following examples are
│ │ │ │  out of sequence. This is because this tutorial was written and code-tested in
│ │ │ │ -separate sessions).</p><p>Here is a bit more complex calculation:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="2686173574-1">(</span><span class="mi">42</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">77</span><span class="p" data-group-id="2686173574-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">66</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │ │ +separate sessions).</p><p>Here is a bit more complex calculation:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="9244574115-1">(</span><span class="mi">42</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">77</span><span class="p" data-group-id="9244574115-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">66</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mf">2618.0</span></code></pre><p>Notice the use of brackets, the multiplication operator <code class="inline">*</code>, and the division
│ │ │ │  operator <code class="inline">/</code>, as in normal arithmetic (see
│ │ │ │  <a href="../../../lib/../system/doc/html/expressions.xhtml">Expressions</a>).</p><p>Press Control-C to shut down the Erlang system and the Erlang shell.</p><p>The following output is shown:</p><pre><code class="text">BREAK: (a)bort (c)ontinue (p)roc info (i)nfo (l)oaded
│ │ │ │         (v)ersion (k)ill (D)b-tables (d)istribution
│ │ │ │  a
│ │ │ │ -$</code></pre><p>Type <code class="inline">a</code> to leave the Erlang system.</p><p>Another way to shut down the Erlang system is by entering <a href="../../../lib/../erts/doc/html/erlang.html#halt/0"><code class="inline">halt/0</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nf">halt</span><span class="p" data-group-id="1722084411-1">(</span><span class="p" data-group-id="1722084411-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +$</code></pre><p>Type <code class="inline">a</code> to leave the Erlang system.</p><p>Another way to shut down the Erlang system is by entering <a href="../../../lib/../erts/doc/html/erlang.html#halt/0"><code class="inline">halt/0</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nf">halt</span><span class="p" data-group-id="0652599919-1">(</span><span class="p" data-group-id="0652599919-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="err">$</span></code></pre><h2 id="modules-and-functions" class="section-heading">
│ │ │ │    <a href="#modules-and-functions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Modules and Functions</span>
│ │ │ │  </h2>
│ │ │ │  <p>A programming language is not much use if you can only run code from the shell.
│ │ │ │  So here is a small Erlang program. Enter it into a file named <code class="inline">tut.erl</code> using a
│ │ │ │  suitable text editor. The file name <code class="inline">tut.erl</code> is important, and also that it is
│ │ │ │  in the same directory as the one where you started <code class="inline">erl</code>. If you are lucky, your
│ │ │ │  editor has an Erlang mode that makes it easier for you to enter and format your
│ │ │ │  code nicely (see <a href="../../../lib/tools/doc/html/erlang_mode_chapter.xhtml">The Erlang mode for Emacs</a>
│ │ │ │  in Tools User's Guide), but you can manage perfectly well without. Here is the
│ │ │ │ -code to enter:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3013868723-1">(</span><span class="ss">tut</span><span class="p" data-group-id="3013868723-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3013868723-2">(</span><span class="p" data-group-id="3013868723-3">[</span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3013868723-3">]</span><span class="p" data-group-id="3013868723-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +code to enter:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1094980269-1">(</span><span class="ss">tut</span><span class="p" data-group-id="1094980269-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1094980269-2">(</span><span class="p" data-group-id="1094980269-3">[</span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1094980269-3">]</span><span class="p" data-group-id="1094980269-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">double</span><span class="p" data-group-id="3013868723-4">(</span><span class="n">X</span><span class="p" data-group-id="3013868723-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">double</span><span class="p" data-group-id="1094980269-4">(</span><span class="n">X</span><span class="p" data-group-id="1094980269-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="p">.</span></code></pre><p>It is not hard to guess that this program doubles the value of numbers. The
│ │ │ │  first two lines of the code are described later. Let us compile the program.
│ │ │ │ -This can be done in an Erlang shell as follows, where <code class="inline">c</code> means compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nf">c</span><span class="p" data-group-id="7783684506-1">(</span><span class="ss">tut</span><span class="p" data-group-id="7783684506-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7783684506-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut</span><span class="p" data-group-id="7783684506-2">}</span></code></pre><p>The <code class="inline">{ok,tut}</code> means that the compilation is OK. If it says <code class="inline">error</code> it means
│ │ │ │ +This can be done in an Erlang shell as follows, where <code class="inline">c</code> means compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nf">c</span><span class="p" data-group-id="6829858079-1">(</span><span class="ss">tut</span><span class="p" data-group-id="6829858079-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6829858079-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut</span><span class="p" data-group-id="6829858079-2">}</span></code></pre><p>The <code class="inline">{ok,tut}</code> means that the compilation is OK. If it says <code class="inline">error</code> it means
│ │ │ │  that there is some mistake in the text that you entered. Additional error
│ │ │ │  messages give an idea about what is wrong so you can modify the text and then try
│ │ │ │ -to compile the program again.</p><p>Now run the program:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">tut</span><span class="p">:</span><span class="nf">double</span><span class="p" data-group-id="8833046488-1">(</span><span class="mi">10</span><span class="p" data-group-id="8833046488-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +to compile the program again.</p><p>Now run the program:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">tut</span><span class="p">:</span><span class="nf">double</span><span class="p" data-group-id="0542141440-1">(</span><span class="mi">10</span><span class="p" data-group-id="0542141440-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">20</span></code></pre><p>As expected, double of 10 is 20.</p><p>Now let us get back to the first two lines of the code. Erlang programs are
│ │ │ │  written in files. Each file contains an Erlang <em>module</em>. The first line of code
│ │ │ │ -in the module is the module name (see <a href="../../../lib/../system/doc/html/modules.xhtml">Modules</a>):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8089203378-1">(</span><span class="ss">tut</span><span class="p" data-group-id="8089203378-1">)</span><span class="p">.</span></code></pre><p>Thus, the module is called <em>tut</em>. Notice the full stop <code class="inline">.</code> at the end of the
│ │ │ │ +in the module is the module name (see <a href="../../../lib/../system/doc/html/modules.xhtml">Modules</a>):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7264834402-1">(</span><span class="ss">tut</span><span class="p" data-group-id="7264834402-1">)</span><span class="p">.</span></code></pre><p>Thus, the module is called <em>tut</em>. Notice the full stop <code class="inline">.</code> at the end of the
│ │ │ │  line. The files which are used to store the module must have the same name as
│ │ │ │  the module but with the extension <code class="inline">.erl</code>. In this case the file name is
│ │ │ │  <code class="inline">tut.erl</code>. When using a function in another module, the syntax
│ │ │ │  <code class="inline">module_name:function_name(arguments)</code> is used. So the following means call
│ │ │ │ -function <code class="inline">double</code> in module <code class="inline">tut</code> with argument <code class="inline">10</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">tut</span><span class="p">:</span><span class="nf">double</span><span class="p" data-group-id="0779423654-1">(</span><span class="mi">10</span><span class="p" data-group-id="0779423654-1">)</span><span class="p">.</span></code></pre><p>The second line says that the module <code class="inline">tut</code> contains a function called <code class="inline">double</code>,
│ │ │ │ -which takes one argument (<code class="inline">X</code> in our example):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5598957454-1">(</span><span class="p" data-group-id="5598957454-2">[</span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5598957454-2">]</span><span class="p" data-group-id="5598957454-1">)</span><span class="p">.</span></code></pre><p>The second line also says that this function can be called from outside the
│ │ │ │ +function <code class="inline">double</code> in module <code class="inline">tut</code> with argument <code class="inline">10</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">tut</span><span class="p">:</span><span class="nf">double</span><span class="p" data-group-id="3009852058-1">(</span><span class="mi">10</span><span class="p" data-group-id="3009852058-1">)</span><span class="p">.</span></code></pre><p>The second line says that the module <code class="inline">tut</code> contains a function called <code class="inline">double</code>,
│ │ │ │ +which takes one argument (<code class="inline">X</code> in our example):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2330078751-1">(</span><span class="p" data-group-id="2330078751-2">[</span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2330078751-2">]</span><span class="p" data-group-id="2330078751-1">)</span><span class="p">.</span></code></pre><p>The second line also says that this function can be called from outside the
│ │ │ │  module <code class="inline">tut</code>. More about this later. Again, notice the <code class="inline">.</code> at the end of the
│ │ │ │  line.</p><p>Now for a more complicated example, the factorial of a number. For example, the
│ │ │ │ -factorial of 4 is <code class="inline">4 * 3 * 2 * 1</code>, which equals 24.</p><p>Enter the following code in a file named <code class="inline">tut1.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1474189918-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="1474189918-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1474189918-2">(</span><span class="p" data-group-id="1474189918-3">[</span><span class="ss">fac</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1474189918-3">]</span><span class="p" data-group-id="1474189918-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +factorial of 4 is <code class="inline">4 * 3 * 2 * 1</code>, which equals 24.</p><p>Enter the following code in a file named <code class="inline">tut1.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6113446280-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="6113446280-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6113446280-2">(</span><span class="p" data-group-id="6113446280-3">[</span><span class="ss">fac</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6113446280-3">]</span><span class="p" data-group-id="6113446280-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">fac</span><span class="p" data-group-id="1474189918-4">(</span><span class="mi">1</span><span class="p" data-group-id="1474189918-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">fac</span><span class="p" data-group-id="6113446280-4">(</span><span class="mi">1</span><span class="p" data-group-id="6113446280-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">fac</span><span class="p" data-group-id="1474189918-5">(</span><span class="n">N</span><span class="p" data-group-id="1474189918-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="1474189918-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="1474189918-6">)</span><span class="p">.</span></code></pre><p>So this is a module called <code class="inline">tut1</code> that contains a function called <code class="inline">fac</code>, which
│ │ │ │ -takes one argument, <code class="inline">N</code>.</p><p>The first part says that the factorial of 1 is 1:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fac</span><span class="p" data-group-id="8162054469-1">(</span><span class="mi">1</span><span class="p" data-group-id="8162054469-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">fac</span><span class="p" data-group-id="6113446280-5">(</span><span class="n">N</span><span class="p" data-group-id="6113446280-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="6113446280-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="6113446280-6">)</span><span class="p">.</span></code></pre><p>So this is a module called <code class="inline">tut1</code> that contains a function called <code class="inline">fac</code>, which
│ │ │ │ +takes one argument, <code class="inline">N</code>.</p><p>The first part says that the factorial of 1 is 1:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fac</span><span class="p" data-group-id="1094201550-1">(</span><span class="mi">1</span><span class="p" data-group-id="1094201550-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="mi">1</span><span class="p">;</span></code></pre><p>Notice that this part ends with a semicolon <code class="inline">;</code> that indicates that there is
│ │ │ │  more of the function <code class="inline">fac</code> to come.</p><p>The second part says that the factorial of N is N multiplied by the factorial of
│ │ │ │ -N - 1:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fac</span><span class="p" data-group-id="4535465791-1">(</span><span class="n">N</span><span class="p" data-group-id="4535465791-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="4535465791-2">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="4535465791-2">)</span><span class="p">.</span></code></pre><p>Notice that this part ends with a <code class="inline">.</code> saying that there are no more parts of
│ │ │ │ -this function.</p><p>Compile the file:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nf">c</span><span class="p" data-group-id="8852013694-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="8852013694-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8852013694-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut1</span><span class="p" data-group-id="8852013694-2">}</span></code></pre><p>And now calculate the factorial of 4.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">6&gt; </span><span class="nc">tut1</span><span class="p">:</span><span class="nf">fac</span><span class="p" data-group-id="8215497777-1">(</span><span class="mi">4</span><span class="p" data-group-id="8215497777-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +N - 1:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fac</span><span class="p" data-group-id="5519935065-1">(</span><span class="n">N</span><span class="p" data-group-id="5519935065-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="5519935065-2">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="5519935065-2">)</span><span class="p">.</span></code></pre><p>Notice that this part ends with a <code class="inline">.</code> saying that there are no more parts of
│ │ │ │ +this function.</p><p>Compile the file:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nf">c</span><span class="p" data-group-id="3351292841-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="3351292841-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3351292841-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut1</span><span class="p" data-group-id="3351292841-2">}</span></code></pre><p>And now calculate the factorial of 4.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">6&gt; </span><span class="nc">tut1</span><span class="p">:</span><span class="nf">fac</span><span class="p" data-group-id="6793319286-1">(</span><span class="mi">4</span><span class="p" data-group-id="6793319286-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">24</span></code></pre><p>Here the function <code class="inline">fac</code> in module <code class="inline">tut1</code> is called with argument <code class="inline">4</code>.</p><p>A function can have many arguments. Let us expand the module <code class="inline">tut1</code> with the
│ │ │ │ -function to multiply two numbers:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8010779523-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="8010779523-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8010779523-2">(</span><span class="p" data-group-id="8010779523-3">[</span><span class="ss">fac</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">mult</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8010779523-3">]</span><span class="p" data-group-id="8010779523-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +function to multiply two numbers:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3383628683-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="3383628683-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3383628683-2">(</span><span class="p" data-group-id="3383628683-3">[</span><span class="ss">fac</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">mult</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3383628683-3">]</span><span class="p" data-group-id="3383628683-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">fac</span><span class="p" data-group-id="8010779523-4">(</span><span class="mi">1</span><span class="p" data-group-id="8010779523-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">fac</span><span class="p" data-group-id="3383628683-4">(</span><span class="mi">1</span><span class="p" data-group-id="3383628683-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">fac</span><span class="p" data-group-id="8010779523-5">(</span><span class="n">N</span><span class="p" data-group-id="8010779523-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="8010779523-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="8010779523-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">fac</span><span class="p" data-group-id="3383628683-5">(</span><span class="n">N</span><span class="p" data-group-id="3383628683-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="3383628683-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="3383628683-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">mult</span><span class="p" data-group-id="8010779523-7">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8010779523-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">mult</span><span class="p" data-group-id="3383628683-7">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3383628683-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">Y</span><span class="p">.</span></code></pre><p>Notice that it is also required to expand the <code class="inline">-export</code> line with the
│ │ │ │ -information that there is another function <code class="inline">mult</code> with two arguments.</p><p>Compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">7&gt; </span><span class="nf">c</span><span class="p" data-group-id="0584904400-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="0584904400-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0584904400-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut1</span><span class="p" data-group-id="0584904400-2">}</span></code></pre><p>Try out the new function <code class="inline">mult</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">8&gt; </span><span class="nc">tut1</span><span class="p">:</span><span class="nf">mult</span><span class="p" data-group-id="5420676977-1">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5420676977-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +information that there is another function <code class="inline">mult</code> with two arguments.</p><p>Compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">7&gt; </span><span class="nf">c</span><span class="p" data-group-id="4957585998-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="4957585998-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4957585998-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut1</span><span class="p" data-group-id="4957585998-2">}</span></code></pre><p>Try out the new function <code class="inline">mult</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">8&gt; </span><span class="nc">tut1</span><span class="p">:</span><span class="nf">mult</span><span class="p" data-group-id="8055609877-1">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="8055609877-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">12</span></code></pre><p>In this example the numbers are integers and the arguments in the functions in
│ │ │ │  the code <code class="inline">N</code>, <code class="inline">X</code>, and <code class="inline">Y</code> are called variables. Variables must start with a
│ │ │ │  capital letter (see <a href="../../../lib/../system/doc/html/expressions.xhtml">Variables</a>). Examples of
│ │ │ │  variables are <code class="inline">Number</code>, <code class="inline">ShoeSize</code>, and <code class="inline">Age</code>.</p><h2 id="atoms" class="section-heading">
│ │ │ │    <a href="#atoms" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Atoms</span>
│ │ │ │  </h2>
│ │ │ │  <p>Atoms are another data type in Erlang. Atoms start with a lowercase letter (see
│ │ │ │  <a href="../../../lib/../system/doc/html/data_types.xhtml">Atom</a>), for example, <code class="inline">charles</code>, <code class="inline">centimeter</code>, and
│ │ │ │  <code class="inline">inch</code>. Atoms are simply names, nothing else. They are not like variables, which
│ │ │ │  can have a value.</p><p>Enter the next program in a file named <code class="inline">tut2.erl</code>. It can be useful for
│ │ │ │ -converting from inches to centimeters and conversely:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4003510904-1">(</span><span class="ss">tut2</span><span class="p" data-group-id="4003510904-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4003510904-2">(</span><span class="p" data-group-id="4003510904-3">[</span><span class="ss">convert</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4003510904-3">]</span><span class="p" data-group-id="4003510904-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +converting from inches to centimeters and conversely:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0657365542-1">(</span><span class="ss">tut2</span><span class="p" data-group-id="0657365542-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0657365542-2">(</span><span class="p" data-group-id="0657365542-3">[</span><span class="ss">convert</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0657365542-3">]</span><span class="p" data-group-id="0657365542-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">convert</span><span class="p" data-group-id="4003510904-4">(</span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="4003510904-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">convert</span><span class="p" data-group-id="0657365542-4">(</span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="0657365542-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">M</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">convert</span><span class="p" data-group-id="4003510904-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="ss">centimeter</span><span class="p" data-group-id="4003510904-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p">.</span></code></pre><p>Compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">9&gt; </span><span class="nf">c</span><span class="p" data-group-id="8871649774-1">(</span><span class="ss">tut2</span><span class="p" data-group-id="8871649774-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8871649774-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut2</span><span class="p" data-group-id="8871649774-2">}</span></code></pre><p>Test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">10&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="3306113341-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="3306113341-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">convert</span><span class="p" data-group-id="0657365542-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="ss">centimeter</span><span class="p" data-group-id="0657365542-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p">.</span></code></pre><p>Compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">9&gt; </span><span class="nf">c</span><span class="p" data-group-id="6247768585-1">(</span><span class="ss">tut2</span><span class="p" data-group-id="6247768585-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6247768585-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut2</span><span class="p" data-group-id="6247768585-2">}</span></code></pre><p>Test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">10&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="1986142143-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="1986142143-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mf">1.1811023622047243</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">11&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="3306113341-2">(</span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="ss">centimeter</span><span class="p" data-group-id="3306113341-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">11&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="1986142143-2">(</span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="ss">centimeter</span><span class="p" data-group-id="1986142143-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mf">17.78</span></code></pre><p>Notice the introduction of decimals (floating point numbers) without any
│ │ │ │  explanation. Hopefully you can cope with that.</p><p>Let us see what happens if something other than <code class="inline">centimeter</code> or <code class="inline">inch</code> is
│ │ │ │ -entered in the <code class="inline">convert</code> function:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">12&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="6514656941-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">miles</span><span class="p" data-group-id="6514656941-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +entered in the <code class="inline">convert</code> function:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">12&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="4402046943-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">miles</span><span class="p" data-group-id="4402046943-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no function clause matching tut2:convert(3,miles) (tut2.erl, line 4)</span></code></pre><p>The two parts of the <code class="inline">convert</code> function are called its clauses. As shown,
│ │ │ │  <code class="inline">miles</code> is not part of either of the clauses. The Erlang system cannot <em>match</em>
│ │ │ │  either of the clauses so an error message <code class="inline">function_clause</code> is returned. The
│ │ │ │  shell formats the error message nicely, but the error tuple is saved in the
│ │ │ │ -shell's history list and can be output by the shell command <code class="inline">v/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">13&gt; </span><span class="nf">v</span><span class="p" data-group-id="2010758910-1">(</span><span class="mi">12</span><span class="p" data-group-id="2010758910-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2010758910-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="2010758910-3">{</span><span class="ss">function_clause</span><span class="p">,</span><span class="p" data-group-id="2010758910-4">[</span><span class="p" data-group-id="2010758910-5">{</span><span class="ss">tut2</span><span class="p">,</span><span class="ss">convert</span><span class="p">,</span><span class="w">
│ │ │ │ -                                </span><span class="p" data-group-id="2010758910-6">[</span><span class="mi">3</span><span class="p">,</span><span class="ss">miles</span><span class="p" data-group-id="2010758910-6">]</span><span class="p">,</span><span class="w">
│ │ │ │ -                                </span><span class="p" data-group-id="2010758910-7">[</span><span class="p" data-group-id="2010758910-8">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;tut2.erl&quot;</span><span class="p" data-group-id="2010758910-8">}</span><span class="p">,</span><span class="p" data-group-id="2010758910-9">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="2010758910-9">}</span><span class="p" data-group-id="2010758910-7">]</span><span class="p" data-group-id="2010758910-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                          </span><span class="p" data-group-id="2010758910-10">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="w">
│ │ │ │ -                                    </span><span class="p" data-group-id="2010758910-11">[</span><span class="p" data-group-id="2010758910-12">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;erl_eval.erl&quot;</span><span class="p" data-group-id="2010758910-12">}</span><span class="p">,</span><span class="p" data-group-id="2010758910-13">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">677</span><span class="p" data-group-id="2010758910-13">}</span><span class="p" data-group-id="2010758910-11">]</span><span class="p" data-group-id="2010758910-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                          </span><span class="p" data-group-id="2010758910-14">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="2010758910-15">[</span><span class="p" data-group-id="2010758910-16">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="2010758910-16">}</span><span class="p">,</span><span class="p" data-group-id="2010758910-17">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">687</span><span class="p" data-group-id="2010758910-17">}</span><span class="p" data-group-id="2010758910-15">]</span><span class="p" data-group-id="2010758910-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                          </span><span class="p" data-group-id="2010758910-18">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="2010758910-19">[</span><span class="p" data-group-id="2010758910-20">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="2010758910-20">}</span><span class="p">,</span><span class="p" data-group-id="2010758910-21">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">642</span><span class="p" data-group-id="2010758910-21">}</span><span class="p" data-group-id="2010758910-19">]</span><span class="p" data-group-id="2010758910-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                          </span><span class="p" data-group-id="2010758910-22">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_loop</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ -                                 </span><span class="p" data-group-id="2010758910-23">[</span><span class="p" data-group-id="2010758910-24">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="2010758910-24">}</span><span class="p">,</span><span class="p" data-group-id="2010758910-25">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">627</span><span class="p" data-group-id="2010758910-25">}</span><span class="p" data-group-id="2010758910-23">]</span><span class="p" data-group-id="2010758910-22">}</span><span class="p" data-group-id="2010758910-4">]</span><span class="p" data-group-id="2010758910-3">}</span><span class="p" data-group-id="2010758910-2">}</span></code></pre><h2 id="tuples" class="section-heading">
│ │ │ │ +shell's history list and can be output by the shell command <code class="inline">v/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">13&gt; </span><span class="nf">v</span><span class="p" data-group-id="3177307888-1">(</span><span class="mi">12</span><span class="p" data-group-id="3177307888-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3177307888-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="3177307888-3">{</span><span class="ss">function_clause</span><span class="p">,</span><span class="p" data-group-id="3177307888-4">[</span><span class="p" data-group-id="3177307888-5">{</span><span class="ss">tut2</span><span class="p">,</span><span class="ss">convert</span><span class="p">,</span><span class="w">
│ │ │ │ +                                </span><span class="p" data-group-id="3177307888-6">[</span><span class="mi">3</span><span class="p">,</span><span class="ss">miles</span><span class="p" data-group-id="3177307888-6">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                                </span><span class="p" data-group-id="3177307888-7">[</span><span class="p" data-group-id="3177307888-8">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;tut2.erl&quot;</span><span class="p" data-group-id="3177307888-8">}</span><span class="p">,</span><span class="p" data-group-id="3177307888-9">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3177307888-9">}</span><span class="p" data-group-id="3177307888-7">]</span><span class="p" data-group-id="3177307888-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                          </span><span class="p" data-group-id="3177307888-10">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="w">
│ │ │ │ +                                    </span><span class="p" data-group-id="3177307888-11">[</span><span class="p" data-group-id="3177307888-12">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;erl_eval.erl&quot;</span><span class="p" data-group-id="3177307888-12">}</span><span class="p">,</span><span class="p" data-group-id="3177307888-13">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">677</span><span class="p" data-group-id="3177307888-13">}</span><span class="p" data-group-id="3177307888-11">]</span><span class="p" data-group-id="3177307888-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                          </span><span class="p" data-group-id="3177307888-14">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="3177307888-15">[</span><span class="p" data-group-id="3177307888-16">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="3177307888-16">}</span><span class="p">,</span><span class="p" data-group-id="3177307888-17">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">687</span><span class="p" data-group-id="3177307888-17">}</span><span class="p" data-group-id="3177307888-15">]</span><span class="p" data-group-id="3177307888-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                          </span><span class="p" data-group-id="3177307888-18">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="3177307888-19">[</span><span class="p" data-group-id="3177307888-20">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="3177307888-20">}</span><span class="p">,</span><span class="p" data-group-id="3177307888-21">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">642</span><span class="p" data-group-id="3177307888-21">}</span><span class="p" data-group-id="3177307888-19">]</span><span class="p" data-group-id="3177307888-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                          </span><span class="p" data-group-id="3177307888-22">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_loop</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ +                                 </span><span class="p" data-group-id="3177307888-23">[</span><span class="p" data-group-id="3177307888-24">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="3177307888-24">}</span><span class="p">,</span><span class="p" data-group-id="3177307888-25">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">627</span><span class="p" data-group-id="3177307888-25">}</span><span class="p" data-group-id="3177307888-23">]</span><span class="p" data-group-id="3177307888-22">}</span><span class="p" data-group-id="3177307888-4">]</span><span class="p" data-group-id="3177307888-3">}</span><span class="p" data-group-id="3177307888-2">}</span></code></pre><h2 id="tuples" class="section-heading">
│ │ │ │    <a href="#tuples" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Tuples</span>
│ │ │ │  </h2>
│ │ │ │ -<p>Now the <code class="inline">tut2</code> program is hardly good programming style. Consider:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="9085190323-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="9085190323-1">)</span><span class="p">.</span></code></pre><p>Does this mean that 3 is in inches? Or does it mean that 3 is in centimeters and
│ │ │ │ +<p>Now the <code class="inline">tut2</code> program is hardly good programming style. Consider:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="2657064817-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="2657064817-1">)</span><span class="p">.</span></code></pre><p>Does this mean that 3 is in inches? Or does it mean that 3 is in centimeters and
│ │ │ │  is to be converted to inches? Erlang has a way to group things together to make
│ │ │ │  things more understandable. These are called <em>tuples</em> and are surrounded by
│ │ │ │  curly brackets, <code class="inline">{</code> and <code class="inline">}</code>.</p><p>So, <code class="inline">{inch,3}</code> denotes 3 inches and <code class="inline">{centimeter,5}</code> denotes 5 centimeters. Now
│ │ │ │  let us write a new program that converts centimeters to inches and conversely.
│ │ │ │ -Enter the following code in a file called <code class="inline">tut3.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9140110927-1">(</span><span class="ss">tut3</span><span class="p" data-group-id="9140110927-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9140110927-2">(</span><span class="p" data-group-id="9140110927-3">[</span><span class="ss">convert_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9140110927-3">]</span><span class="p" data-group-id="9140110927-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +Enter the following code in a file called <code class="inline">tut3.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0893937971-1">(</span><span class="ss">tut3</span><span class="p" data-group-id="0893937971-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0893937971-2">(</span><span class="p" data-group-id="0893937971-3">[</span><span class="ss">convert_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0893937971-3">]</span><span class="p" data-group-id="0893937971-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">convert_length</span><span class="p" data-group-id="9140110927-4">(</span><span class="p" data-group-id="9140110927-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9140110927-5">}</span><span class="p" data-group-id="9140110927-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9140110927-6">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="9140110927-6">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">convert_length</span><span class="p" data-group-id="9140110927-7">(</span><span class="p" data-group-id="9140110927-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9140110927-8">}</span><span class="p" data-group-id="9140110927-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9140110927-9">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="9140110927-9">}</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">14&gt; </span><span class="nf">c</span><span class="p" data-group-id="5524670857-1">(</span><span class="ss">tut3</span><span class="p" data-group-id="5524670857-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5524670857-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut3</span><span class="p" data-group-id="5524670857-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">15&gt; </span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="5524670857-3">(</span><span class="p" data-group-id="5524670857-4">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="5524670857-4">}</span><span class="p" data-group-id="5524670857-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5524670857-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="mf">12.7</span><span class="p" data-group-id="5524670857-5">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">16&gt; </span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="5524670857-6">(</span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="5524670857-7">(</span><span class="p" data-group-id="5524670857-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="5524670857-8">}</span><span class="p" data-group-id="5524670857-7">)</span><span class="p" data-group-id="5524670857-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5524670857-9">{</span><span class="ss">inch</span><span class="p">,</span><span class="mf">5.0</span><span class="p" data-group-id="5524670857-9">}</span></code></pre><p>Notice on line 16 that 5 inches are converted to centimeters and back again,
│ │ │ │ +</span><span class="nf">convert_length</span><span class="p" data-group-id="0893937971-4">(</span><span class="p" data-group-id="0893937971-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0893937971-5">}</span><span class="p" data-group-id="0893937971-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0893937971-6">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="0893937971-6">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">convert_length</span><span class="p" data-group-id="0893937971-7">(</span><span class="p" data-group-id="0893937971-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0893937971-8">}</span><span class="p" data-group-id="0893937971-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0893937971-9">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="0893937971-9">}</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">14&gt; </span><span class="nf">c</span><span class="p" data-group-id="0156867835-1">(</span><span class="ss">tut3</span><span class="p" data-group-id="0156867835-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0156867835-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut3</span><span class="p" data-group-id="0156867835-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">15&gt; </span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="0156867835-3">(</span><span class="p" data-group-id="0156867835-4">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="0156867835-4">}</span><span class="p" data-group-id="0156867835-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0156867835-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="mf">12.7</span><span class="p" data-group-id="0156867835-5">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">16&gt; </span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="0156867835-6">(</span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="0156867835-7">(</span><span class="p" data-group-id="0156867835-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="0156867835-8">}</span><span class="p" data-group-id="0156867835-7">)</span><span class="p" data-group-id="0156867835-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0156867835-9">{</span><span class="ss">inch</span><span class="p">,</span><span class="mf">5.0</span><span class="p" data-group-id="0156867835-9">}</span></code></pre><p>Notice on line 16 that 5 inches are converted to centimeters and back again,
│ │ │ │  yielding the original value. This also shows that the argument to a function
│ │ │ │  can be the result of another function. Consider how line 16 (above) works. The
│ │ │ │  argument given to the function <code class="inline">{inch,5}</code> is first matched against the first
│ │ │ │  head clause of <code class="inline">convert_length</code>, that is, <code class="inline">convert_length({centimeter,X})</code>. It
│ │ │ │  can be seen that <code class="inline">{centimeter,X}</code> does not match <code class="inline">{inch,5}</code> (the head is the bit
│ │ │ │  before the <code class="inline">-&gt;</code>). This having failed, let us try the head of the next clause
│ │ │ │  that is, <code class="inline">convert_length({inch,Y})</code>. This matches, and <code class="inline">Y</code> gets the value 5.</p><p>Tuples can have more than two parts, in fact as many parts as you want, and
│ │ │ │  contain any valid Erlang <em>term</em>. For example, to represent the temperature of
│ │ │ │ -various cities of the world:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4617213286-1">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4617213286-2">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="4617213286-2">}</span><span class="p" data-group-id="4617213286-1">}</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4617213286-3">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4617213286-4">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="4617213286-4">}</span><span class="p" data-group-id="4617213286-3">}</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4617213286-5">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4617213286-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="4617213286-6">}</span><span class="p" data-group-id="4617213286-5">}</span></code></pre><p>Tuples have a fixed number of items in them. Each item in a tuple is called an
│ │ │ │ +various cities of the world:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6996981847-1">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6996981847-2">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="6996981847-2">}</span><span class="p" data-group-id="6996981847-1">}</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6996981847-3">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6996981847-4">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="6996981847-4">}</span><span class="p" data-group-id="6996981847-3">}</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6996981847-5">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6996981847-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="6996981847-6">}</span><span class="p" data-group-id="6996981847-5">}</span></code></pre><p>Tuples have a fixed number of items in them. Each item in a tuple is called an
│ │ │ │  <em>element</em>. In the tuple <code class="inline">{moscow,{c,-10}}</code>, element 1 is <code class="inline">moscow</code> and element 2
│ │ │ │  is <code class="inline">{c,-10}</code>. Here <code class="inline">c</code> represents Celsius and <code class="inline">f</code> Fahrenheit.</p><h2 id="lists" class="section-heading">
│ │ │ │    <a href="#lists" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Lists</span>
│ │ │ │  </h2>
│ │ │ │  <p>Whereas tuples group things together, it is also necessary to represent lists of
│ │ │ │  things. Lists in Erlang are surrounded by square brackets, <code class="inline">[</code> and <code class="inline">]</code>. For
│ │ │ │ -example, a list of the temperatures of various cities in the world can be:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3692983561-1">[</span><span class="p" data-group-id="3692983561-2">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3692983561-3">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="3692983561-3">}</span><span class="p" data-group-id="3692983561-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3692983561-4">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3692983561-5">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="3692983561-5">}</span><span class="p" data-group-id="3692983561-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3692983561-6">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3692983561-7">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="3692983561-7">}</span><span class="p" data-group-id="3692983561-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3692983561-8">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3692983561-9">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="3692983561-9">}</span><span class="p" data-group-id="3692983561-8">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3692983561-10">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3692983561-11">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="3692983561-11">}</span><span class="p" data-group-id="3692983561-10">}</span><span class="p" data-group-id="3692983561-1">]</span></code></pre><p>Notice that this list was so long that it did not fit on one line. This does not
│ │ │ │ +example, a list of the temperatures of various cities in the world can be:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7197282565-1">[</span><span class="p" data-group-id="7197282565-2">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7197282565-3">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="7197282565-3">}</span><span class="p" data-group-id="7197282565-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7197282565-4">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7197282565-5">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="7197282565-5">}</span><span class="p" data-group-id="7197282565-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7197282565-6">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7197282565-7">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="7197282565-7">}</span><span class="p" data-group-id="7197282565-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7197282565-8">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7197282565-9">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="7197282565-9">}</span><span class="p" data-group-id="7197282565-8">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7197282565-10">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7197282565-11">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="7197282565-11">}</span><span class="p" data-group-id="7197282565-10">}</span><span class="p" data-group-id="7197282565-1">]</span></code></pre><p>Notice that this list was so long that it did not fit on one line. This does not
│ │ │ │  matter, Erlang allows line breaks at all &quot;sensible places&quot; but not, for example,
│ │ │ │  in the middle of atoms, integers, and others.</p><p>A useful way of looking at parts of lists is by using <code class="inline">|</code>. This is best
│ │ │ │ -explained by an example using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">17&gt; </span><span class="p" data-group-id="0038431325-1">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="n">TheRest</span><span class="p" data-group-id="0038431325-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0038431325-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0038431325-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0038431325-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0038431325-3">]</span><span class="w">
│ │ │ │ +explained by an example using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">17&gt; </span><span class="p" data-group-id="3184221617-1">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="n">TheRest</span><span class="p" data-group-id="3184221617-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3184221617-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="3184221617-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3184221617-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="3184221617-3">]</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">18&gt; </span><span class="n">First</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">1</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">19&gt; </span><span class="n">TheRest</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0038431325-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0038431325-4">]</span></code></pre><p>To separate the first element of the list from the rest of the list, <code class="inline">|</code> is
│ │ │ │ -used. <code class="inline">First</code> has the value <code class="inline">1</code> and <code class="inline">TheRest</code> has the value <code class="inline">[2,3,4,5]</code>.</p><p>Another example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">20&gt; </span><span class="p" data-group-id="4282984356-1">[</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">R</span><span class="p" data-group-id="4282984356-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4282984356-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="4282984356-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4282984356-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="4282984356-3">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3184221617-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="3184221617-4">]</span></code></pre><p>To separate the first element of the list from the rest of the list, <code class="inline">|</code> is
│ │ │ │ +used. <code class="inline">First</code> has the value <code class="inline">1</code> and <code class="inline">TheRest</code> has the value <code class="inline">[2,3,4,5]</code>.</p><p>Another example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">20&gt; </span><span class="p" data-group-id="8750349195-1">[</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">R</span><span class="p" data-group-id="8750349195-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8750349195-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="8750349195-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8750349195-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="8750349195-3">]</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">21&gt; </span><span class="n">E1</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">1</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">22&gt; </span><span class="n">E2</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">2</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">23&gt; </span><span class="n">R</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4282984356-4">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="4282984356-4">]</span></code></pre><p>Here you see the use of <code class="inline">|</code> to get the first two elements from the list. If you
│ │ │ │ +</span><span class="p" data-group-id="8750349195-4">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="8750349195-4">]</span></code></pre><p>Here you see the use of <code class="inline">|</code> to get the first two elements from the list. If you
│ │ │ │  try to get more elements from the list than there are elements in the list, an
│ │ │ │  error is returned. Notice also the special case of the list with no elements,
│ │ │ │ -<code class="inline">[]</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">24&gt; </span><span class="p" data-group-id="0644123108-1">[</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="0644123108-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0644123108-2">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0644123108-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0644123108-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0644123108-3">]</span><span class="w">
│ │ │ │ +<code class="inline">[]</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">24&gt; </span><span class="p" data-group-id="2785897400-1">[</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="2785897400-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2785897400-2">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="2785897400-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2785897400-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2785897400-3">]</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">25&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">1</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">26&gt; </span><span class="n">B</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">2</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">27&gt; </span><span class="n">C</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0644123108-4">[</span><span class="p" data-group-id="0644123108-4">]</span></code></pre><p>In the previous examples, new variable names are used, instead of reusing the
│ │ │ │ +</span><span class="p" data-group-id="2785897400-4">[</span><span class="p" data-group-id="2785897400-4">]</span></code></pre><p>In the previous examples, new variable names are used, instead of reusing the
│ │ │ │  old ones: <code class="inline">First</code>, <code class="inline">TheRest</code>, <code class="inline">E1</code>, <code class="inline">E2</code>, <code class="inline">R</code>, <code class="inline">A</code>, <code class="inline">B</code>, and <code class="inline">C</code>. The reason for
│ │ │ │  this is that a variable can only be given a value once in its context (scope).
│ │ │ │  More about this later.</p><p>The following example shows how to find the length of a list. Enter the
│ │ │ │ -following code in a file named <code class="inline">tut4.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0596250876-1">(</span><span class="ss">tut4</span><span class="p" data-group-id="0596250876-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +following code in a file named <code class="inline">tut4.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2879623543-1">(</span><span class="ss">tut4</span><span class="p" data-group-id="2879623543-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0596250876-2">(</span><span class="p" data-group-id="0596250876-3">[</span><span class="ss">list_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0596250876-3">]</span><span class="p" data-group-id="0596250876-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2879623543-2">(</span><span class="p" data-group-id="2879623543-3">[</span><span class="ss">list_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2879623543-3">]</span><span class="p" data-group-id="2879623543-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">list_length</span><span class="p" data-group-id="0596250876-4">(</span><span class="p" data-group-id="0596250876-5">[</span><span class="p" data-group-id="0596250876-5">]</span><span class="p" data-group-id="0596250876-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">list_length</span><span class="p" data-group-id="2879623543-4">(</span><span class="p" data-group-id="2879623543-5">[</span><span class="p" data-group-id="2879623543-5">]</span><span class="p" data-group-id="2879623543-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="mi">0</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">list_length</span><span class="p" data-group-id="0596250876-6">(</span><span class="p" data-group-id="0596250876-7">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0596250876-7">]</span><span class="p" data-group-id="0596250876-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">list_length</span><span class="p" data-group-id="0596250876-8">(</span><span class="n">Rest</span><span class="p" data-group-id="0596250876-8">)</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">28&gt; </span><span class="nf">c</span><span class="p" data-group-id="1472701298-1">(</span><span class="ss">tut4</span><span class="p" data-group-id="1472701298-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1472701298-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut4</span><span class="p" data-group-id="1472701298-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">29&gt; </span><span class="nc">tut4</span><span class="p">:</span><span class="nf">list_length</span><span class="p" data-group-id="1472701298-3">(</span><span class="p" data-group-id="1472701298-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="1472701298-4">]</span><span class="p" data-group-id="1472701298-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="mi">7</span></code></pre><p>Explanation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_length</span><span class="p" data-group-id="8869915286-1">(</span><span class="p" data-group-id="8869915286-2">[</span><span class="p" data-group-id="8869915286-2">]</span><span class="p" data-group-id="8869915286-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="mi">0</span><span class="p">;</span></code></pre><p>The length of an empty list is obviously 0.</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_length</span><span class="p" data-group-id="2280627569-1">(</span><span class="p" data-group-id="2280627569-2">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="2280627569-2">]</span><span class="p" data-group-id="2280627569-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">list_length</span><span class="p" data-group-id="2280627569-3">(</span><span class="n">Rest</span><span class="p" data-group-id="2280627569-3">)</span><span class="p">.</span></code></pre><p>The length of a list with the first element <code class="inline">First</code> and the remaining elements
│ │ │ │ +</span><span class="nf">list_length</span><span class="p" data-group-id="2879623543-6">(</span><span class="p" data-group-id="2879623543-7">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="2879623543-7">]</span><span class="p" data-group-id="2879623543-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">list_length</span><span class="p" data-group-id="2879623543-8">(</span><span class="n">Rest</span><span class="p" data-group-id="2879623543-8">)</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">28&gt; </span><span class="nf">c</span><span class="p" data-group-id="9374149804-1">(</span><span class="ss">tut4</span><span class="p" data-group-id="9374149804-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9374149804-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut4</span><span class="p" data-group-id="9374149804-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">29&gt; </span><span class="nc">tut4</span><span class="p">:</span><span class="nf">list_length</span><span class="p" data-group-id="9374149804-3">(</span><span class="p" data-group-id="9374149804-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="9374149804-4">]</span><span class="p" data-group-id="9374149804-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="mi">7</span></code></pre><p>Explanation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_length</span><span class="p" data-group-id="0862908261-1">(</span><span class="p" data-group-id="0862908261-2">[</span><span class="p" data-group-id="0862908261-2">]</span><span class="p" data-group-id="0862908261-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="mi">0</span><span class="p">;</span></code></pre><p>The length of an empty list is obviously 0.</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_length</span><span class="p" data-group-id="0736985689-1">(</span><span class="p" data-group-id="0736985689-2">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0736985689-2">]</span><span class="p" data-group-id="0736985689-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">list_length</span><span class="p" data-group-id="0736985689-3">(</span><span class="n">Rest</span><span class="p" data-group-id="0736985689-3">)</span><span class="p">.</span></code></pre><p>The length of a list with the first element <code class="inline">First</code> and the remaining elements
│ │ │ │  <code class="inline">Rest</code> is 1 + the length of <code class="inline">Rest</code>.</p><p>(Advanced readers only: This is not tail recursive, there is a better way to
│ │ │ │  write this function.)</p><p>In general, tuples are used where &quot;records&quot; or &quot;structs&quot; are used in other
│ │ │ │  languages. Also, lists are used when representing things with varying sizes,
│ │ │ │  that is, where linked lists are used in other languages.</p><p>Erlang does not have a string data type. Instead, strings can be represented by
│ │ │ │  lists of Unicode characters. This implies for example that the list <code class="inline">[97,98,99]</code>
│ │ │ │  is equivalent to <code class="inline">&quot;abc&quot;</code>. The Erlang shell is &quot;clever&quot; and guesses what list you
│ │ │ │ -mean and outputs it in what it thinks is the most appropriate form, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">30&gt; </span><span class="p" data-group-id="0028348392-1">[</span><span class="mi">97</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="0028348392-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +mean and outputs it in what it thinks is the most appropriate form, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">30&gt; </span><span class="p" data-group-id="1283231839-1">[</span><span class="mi">97</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="1283231839-1">]</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;abc&quot;</span></code></pre><h2 id="maps" class="section-heading">
│ │ │ │    <a href="#maps" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Maps</span>
│ │ │ │  </h2>
│ │ │ │  <p>Maps are a set of key to value associations. These associations are encapsulated
│ │ │ │ -with <code class="inline">#{</code> and <code class="inline">}</code>. To create an association from <code class="inline">&quot;key&quot;</code> to value <code class="inline">42</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="3771684561-1">#{</span><span class="w"> </span><span class="s">&quot;key&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p" data-group-id="3771684561-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3771684561-2">#{</span><span class="s">&quot;key&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="3771684561-2">}</span></code></pre><p>Let us jump straight into the deep end with an example using some interesting
│ │ │ │ +with <code class="inline">#{</code> and <code class="inline">}</code>. To create an association from <code class="inline">&quot;key&quot;</code> to value <code class="inline">42</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="2015126637-1">#{</span><span class="w"> </span><span class="s">&quot;key&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p" data-group-id="2015126637-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2015126637-2">#{</span><span class="s">&quot;key&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="2015126637-2">}</span></code></pre><p>Let us jump straight into the deep end with an example using some interesting
│ │ │ │  features.</p><p>The following example shows how to calculate alpha blending using maps to
│ │ │ │ -reference color and alpha channels. Enter the code in a file named <code class="inline">color.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4328735602-1">(</span><span class="ss">color</span><span class="p" data-group-id="4328735602-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +reference color and alpha channels. Enter the code in a file named <code class="inline">color.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8267982160-1">(</span><span class="ss">color</span><span class="p" data-group-id="8267982160-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4328735602-2">(</span><span class="p" data-group-id="4328735602-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="ss">blend</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4328735602-3">]</span><span class="p" data-group-id="4328735602-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8267982160-2">(</span><span class="p" data-group-id="8267982160-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="ss">blend</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8267982160-3">]</span><span class="p" data-group-id="8267982160-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4328735602-4">(</span><span class="nf">is_channel</span><span class="p" data-group-id="4328735602-5">(</span><span class="n">V</span><span class="p" data-group-id="4328735602-5">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4328735602-6">(</span><span class="nf">is_float</span><span class="p" data-group-id="4328735602-7">(</span><span class="n">V</span><span class="p" data-group-id="4328735602-7">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="4328735602-6">)</span><span class="p" data-group-id="4328735602-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8267982160-4">(</span><span class="nf">is_channel</span><span class="p" data-group-id="8267982160-5">(</span><span class="n">V</span><span class="p" data-group-id="8267982160-5">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8267982160-6">(</span><span class="nf">is_float</span><span class="p" data-group-id="8267982160-7">(</span><span class="n">V</span><span class="p" data-group-id="8267982160-7">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="8267982160-6">)</span><span class="p" data-group-id="8267982160-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">new</span><span class="p" data-group-id="4328735602-8">(</span><span class="n">R</span><span class="p">,</span><span class="n">G</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">A</span><span class="p" data-group-id="4328735602-8">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="4328735602-9">(</span><span class="n">R</span><span class="p" data-group-id="4328735602-9">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="4328735602-10">(</span><span class="n">G</span><span class="p" data-group-id="4328735602-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -                  </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="4328735602-11">(</span><span class="n">B</span><span class="p" data-group-id="4328735602-11">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="4328735602-12">(</span><span class="n">A</span><span class="p" data-group-id="4328735602-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4328735602-13">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">G</span><span class="p">,</span><span class="w"> </span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="4328735602-13">}</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">blend</span><span class="p" data-group-id="4328735602-14">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="4328735602-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">blend</span><span class="p" data-group-id="4328735602-15">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="nf">alpha</span><span class="p" data-group-id="4328735602-16">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="4328735602-16">)</span><span class="p" data-group-id="4328735602-15">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">blend</span><span class="p" data-group-id="4328735602-17">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="n">Alpha</span><span class="p" data-group-id="4328735602-17">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Alpha</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Dst</span><span class="p" data-group-id="4328735602-18">#{</span><span class="w">
│ │ │ │ -        </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="nf">red</span><span class="p" data-group-id="4328735602-19">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="4328735602-19">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="nf">green</span><span class="p" data-group-id="4328735602-20">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="4328735602-20">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="nf">blue</span><span class="p" data-group-id="4328735602-21">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="4328735602-21">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">new</span><span class="p" data-group-id="8267982160-8">(</span><span class="n">R</span><span class="p">,</span><span class="n">G</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">A</span><span class="p" data-group-id="8267982160-8">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8267982160-9">(</span><span class="n">R</span><span class="p" data-group-id="8267982160-9">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8267982160-10">(</span><span class="n">G</span><span class="p" data-group-id="8267982160-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +                  </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8267982160-11">(</span><span class="n">B</span><span class="p" data-group-id="8267982160-11">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8267982160-12">(</span><span class="n">A</span><span class="p" data-group-id="8267982160-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8267982160-13">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">G</span><span class="p">,</span><span class="w"> </span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="8267982160-13">}</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">blend</span><span class="p" data-group-id="8267982160-14">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="8267982160-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">blend</span><span class="p" data-group-id="8267982160-15">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="nf">alpha</span><span class="p" data-group-id="8267982160-16">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="8267982160-16">)</span><span class="p" data-group-id="8267982160-15">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">blend</span><span class="p" data-group-id="8267982160-17">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="n">Alpha</span><span class="p" data-group-id="8267982160-17">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Alpha</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Dst</span><span class="p" data-group-id="8267982160-18">#{</span><span class="w">
│ │ │ │ +        </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="nf">red</span><span class="p" data-group-id="8267982160-19">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="8267982160-19">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="nf">green</span><span class="p" data-group-id="8267982160-20">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="8267982160-20">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="nf">blue</span><span class="p" data-group-id="8267982160-21">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="8267982160-21">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │          </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Alpha</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4328735602-18">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">blend</span><span class="p" data-group-id="4328735602-22">(</span><span class="p">_</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4328735602-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Dst</span><span class="p" data-group-id="4328735602-23">#{</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8267982160-18">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">blend</span><span class="p" data-group-id="8267982160-22">(</span><span class="p">_</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="8267982160-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Dst</span><span class="p" data-group-id="8267982160-23">#{</span><span class="w">
│ │ │ │          </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="mf">0.0</span><span class="p">,</span><span class="w">
│ │ │ │          </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mf">0.0</span><span class="p">,</span><span class="w">
│ │ │ │          </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="mf">0.0</span><span class="p">,</span><span class="w">
│ │ │ │          </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mf">0.0</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4328735602-23">}</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8267982160-23">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">alpha</span><span class="p" data-group-id="4328735602-24">(</span><span class="p" data-group-id="4328735602-25">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="4328735602-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4328735602-26">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="4328735602-26">}</span><span class="p" data-group-id="4328735602-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="4328735602-27">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="4328735602-27">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">alpha</span><span class="p" data-group-id="8267982160-24">(</span><span class="p" data-group-id="8267982160-25">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8267982160-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8267982160-26">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="8267982160-26">}</span><span class="p" data-group-id="8267982160-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="8267982160-27">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8267982160-27">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">red</span><span class="p" data-group-id="4328735602-28">(</span><span class="p" data-group-id="4328735602-29">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="4328735602-29">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4328735602-30">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="4328735602-30">}</span><span class="p" data-group-id="4328735602-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="4328735602-31">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="4328735602-31">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">green</span><span class="p" data-group-id="4328735602-32">(</span><span class="p" data-group-id="4328735602-33">#{</span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="4328735602-33">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4328735602-34">#{</span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="4328735602-34">}</span><span class="p" data-group-id="4328735602-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="4328735602-35">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="4328735602-35">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">blue</span><span class="p" data-group-id="4328735602-36">(</span><span class="p" data-group-id="4328735602-37">#{</span><span class="ss">blue</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="4328735602-37">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4328735602-38">#{</span><span class="ss">blue</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="4328735602-38">}</span><span class="p" data-group-id="4328735602-36">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="4328735602-39">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="4328735602-39">)</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">c</span><span class="p" data-group-id="4704390947-1">(</span><span class="ss">color</span><span class="p" data-group-id="4704390947-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4704390947-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">color</span><span class="p" data-group-id="4704390947-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">C1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">color</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="4704390947-3">(</span><span class="mf">0.3</span><span class="p">,</span><span class="mf">0.4</span><span class="p">,</span><span class="mf">0.5</span><span class="p">,</span><span class="mf">1.0</span><span class="p" data-group-id="4704390947-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4704390947-4">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.5</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.4</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p" data-group-id="4704390947-4">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">C2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">color</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="4704390947-5">(</span><span class="mf">1.0</span><span class="p">,</span><span class="mf">0.8</span><span class="p">,</span><span class="mf">0.1</span><span class="p">,</span><span class="mf">0.3</span><span class="p" data-group-id="4704390947-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4704390947-6">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.1</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.8</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="4704390947-6">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">color</span><span class="p">:</span><span class="nf">blend</span><span class="p" data-group-id="4704390947-7">(</span><span class="n">C1</span><span class="p">,</span><span class="n">C2</span><span class="p" data-group-id="4704390947-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4704390947-8">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.5</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.4</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p" data-group-id="4704390947-8">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">color</span><span class="p">:</span><span class="nf">blend</span><span class="p" data-group-id="4704390947-9">(</span><span class="n">C2</span><span class="p">,</span><span class="n">C1</span><span class="p" data-group-id="4704390947-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4704390947-10">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.38</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.52</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.51</span><span class="p" data-group-id="4704390947-10">}</span></code></pre><p>This example warrants some explanation:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5982948096-1">(</span><span class="nf">is_channel</span><span class="p" data-group-id="5982948096-2">(</span><span class="n">V</span><span class="p" data-group-id="5982948096-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5982948096-3">(</span><span class="nf">is_float</span><span class="p" data-group-id="5982948096-4">(</span><span class="n">V</span><span class="p" data-group-id="5982948096-4">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="5982948096-3">)</span><span class="p" data-group-id="5982948096-1">)</span><span class="p">.</span></code></pre><p>First a macro <code class="inline">is_channel</code> is defined to help with the guard tests. This is only
│ │ │ │ +</span><span class="nf">red</span><span class="p" data-group-id="8267982160-28">(</span><span class="p" data-group-id="8267982160-29">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8267982160-29">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8267982160-30">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="8267982160-30">}</span><span class="p" data-group-id="8267982160-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="8267982160-31">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8267982160-31">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">green</span><span class="p" data-group-id="8267982160-32">(</span><span class="p" data-group-id="8267982160-33">#{</span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8267982160-33">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8267982160-34">#{</span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="8267982160-34">}</span><span class="p" data-group-id="8267982160-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="8267982160-35">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8267982160-35">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">blue</span><span class="p" data-group-id="8267982160-36">(</span><span class="p" data-group-id="8267982160-37">#{</span><span class="ss">blue</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8267982160-37">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8267982160-38">#{</span><span class="ss">blue</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="8267982160-38">}</span><span class="p" data-group-id="8267982160-36">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="8267982160-39">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8267982160-39">)</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">c</span><span class="p" data-group-id="5509940146-1">(</span><span class="ss">color</span><span class="p" data-group-id="5509940146-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5509940146-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">color</span><span class="p" data-group-id="5509940146-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">C1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">color</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="5509940146-3">(</span><span class="mf">0.3</span><span class="p">,</span><span class="mf">0.4</span><span class="p">,</span><span class="mf">0.5</span><span class="p">,</span><span class="mf">1.0</span><span class="p" data-group-id="5509940146-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5509940146-4">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.5</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.4</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p" data-group-id="5509940146-4">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">C2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">color</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="5509940146-5">(</span><span class="mf">1.0</span><span class="p">,</span><span class="mf">0.8</span><span class="p">,</span><span class="mf">0.1</span><span class="p">,</span><span class="mf">0.3</span><span class="p" data-group-id="5509940146-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5509940146-6">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.1</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.8</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="5509940146-6">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">color</span><span class="p">:</span><span class="nf">blend</span><span class="p" data-group-id="5509940146-7">(</span><span class="n">C1</span><span class="p">,</span><span class="n">C2</span><span class="p" data-group-id="5509940146-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5509940146-8">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.5</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.4</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p" data-group-id="5509940146-8">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">color</span><span class="p">:</span><span class="nf">blend</span><span class="p" data-group-id="5509940146-9">(</span><span class="n">C2</span><span class="p">,</span><span class="n">C1</span><span class="p" data-group-id="5509940146-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5509940146-10">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.38</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.52</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.51</span><span class="p" data-group-id="5509940146-10">}</span></code></pre><p>This example warrants some explanation:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9102511908-1">(</span><span class="nf">is_channel</span><span class="p" data-group-id="9102511908-2">(</span><span class="n">V</span><span class="p" data-group-id="9102511908-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9102511908-3">(</span><span class="nf">is_float</span><span class="p" data-group-id="9102511908-4">(</span><span class="n">V</span><span class="p" data-group-id="9102511908-4">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="9102511908-3">)</span><span class="p" data-group-id="9102511908-1">)</span><span class="p">.</span></code></pre><p>First a macro <code class="inline">is_channel</code> is defined to help with the guard tests. This is only
│ │ │ │  here for convenience and to reduce syntax cluttering. For more information about
│ │ │ │ -macros, see <a href="../../../lib/../system/doc/html/macros.xhtml">The Preprocessor</a>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">new</span><span class="p" data-group-id="8665962610-1">(</span><span class="n">R</span><span class="p">,</span><span class="n">G</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">A</span><span class="p" data-group-id="8665962610-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8665962610-2">(</span><span class="n">R</span><span class="p" data-group-id="8665962610-2">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8665962610-3">(</span><span class="n">G</span><span class="p" data-group-id="8665962610-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -                  </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8665962610-4">(</span><span class="n">B</span><span class="p" data-group-id="8665962610-4">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8665962610-5">(</span><span class="n">A</span><span class="p" data-group-id="8665962610-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8665962610-6">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">G</span><span class="p">,</span><span class="w"> </span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="8665962610-6">}</span><span class="p">.</span></code></pre><p>The function <code class="inline">new/4</code> creates a new map term and lets the keys <code class="inline">red</code>, <code class="inline">green</code>,
│ │ │ │ +macros, see <a href="../../../lib/../system/doc/html/macros.xhtml">The Preprocessor</a>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">new</span><span class="p" data-group-id="8527265458-1">(</span><span class="n">R</span><span class="p">,</span><span class="n">G</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">A</span><span class="p" data-group-id="8527265458-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8527265458-2">(</span><span class="n">R</span><span class="p" data-group-id="8527265458-2">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8527265458-3">(</span><span class="n">G</span><span class="p" data-group-id="8527265458-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +                  </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8527265458-4">(</span><span class="n">B</span><span class="p" data-group-id="8527265458-4">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8527265458-5">(</span><span class="n">A</span><span class="p" data-group-id="8527265458-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8527265458-6">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">G</span><span class="p">,</span><span class="w"> </span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="8527265458-6">}</span><span class="p">.</span></code></pre><p>The function <code class="inline">new/4</code> creates a new map term and lets the keys <code class="inline">red</code>, <code class="inline">green</code>,
│ │ │ │  <code class="inline">blue</code>, and <code class="inline">alpha</code> be associated with an initial value. In this case, only
│ │ │ │  float values between and including 0.0 and 1.0 are allowed, as ensured by the
│ │ │ │  <code class="inline">?is_channel/1</code> macro for each argument. Only the <code class="inline">=&gt;</code> operator is allowed when
│ │ │ │  creating a new map.</p><p>By calling <code class="inline">blend/2</code> on any color term created by <code class="inline">new/4</code>, the resulting color
│ │ │ │ -can be calculated as determined by the two map terms.</p><p>The first thing <code class="inline">blend/2</code> does is to calculate the resulting alpha channel:</p><pre><code class="makeup erlang" translate="no"><span class="nf">alpha</span><span class="p" data-group-id="9169133284-1">(</span><span class="p" data-group-id="9169133284-2">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="9169133284-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9169133284-3">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="9169133284-3">}</span><span class="p" data-group-id="9169133284-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="9169133284-4">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="9169133284-4">)</span><span class="p">.</span></code></pre><p>The value associated with key <code class="inline">alpha</code> is fetched for both arguments using the
│ │ │ │ +can be calculated as determined by the two map terms.</p><p>The first thing <code class="inline">blend/2</code> does is to calculate the resulting alpha channel:</p><pre><code class="makeup erlang" translate="no"><span class="nf">alpha</span><span class="p" data-group-id="2380814556-1">(</span><span class="p" data-group-id="2380814556-2">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="2380814556-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2380814556-3">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="2380814556-3">}</span><span class="p" data-group-id="2380814556-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="2380814556-4">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="2380814556-4">)</span><span class="p">.</span></code></pre><p>The value associated with key <code class="inline">alpha</code> is fetched for both arguments using the
│ │ │ │  <code class="inline">:=</code> operator. The other keys in the map are ignored, only the key <code class="inline">alpha</code> is
│ │ │ │ -required and checked for.</p><p>This is also the case for functions <code class="inline">red/2</code>, <code class="inline">blue/2</code>, and <code class="inline">green/2</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">red</span><span class="p" data-group-id="4301525806-1">(</span><span class="p" data-group-id="4301525806-2">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="4301525806-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4301525806-3">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="4301525806-3">}</span><span class="p" data-group-id="4301525806-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="4301525806-4">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="4301525806-4">)</span><span class="p">.</span></code></pre><p>The difference here is that a check is made for two keys in each map argument.
│ │ │ │ -The other keys are ignored.</p><p>Finally, let us return the resulting color in <code class="inline">blend/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">blend</span><span class="p" data-group-id="7017218739-1">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="n">Alpha</span><span class="p" data-group-id="7017218739-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Alpha</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Dst</span><span class="p" data-group-id="7017218739-2">#{</span><span class="w">
│ │ │ │ -        </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="nf">red</span><span class="p" data-group-id="7017218739-3">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="7017218739-3">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="nf">green</span><span class="p" data-group-id="7017218739-4">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="7017218739-4">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="nf">blue</span><span class="p" data-group-id="7017218739-5">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="7017218739-5">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ +required and checked for.</p><p>This is also the case for functions <code class="inline">red/2</code>, <code class="inline">blue/2</code>, and <code class="inline">green/2</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">red</span><span class="p" data-group-id="3682356227-1">(</span><span class="p" data-group-id="3682356227-2">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="3682356227-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3682356227-3">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="3682356227-3">}</span><span class="p" data-group-id="3682356227-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="3682356227-4">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="3682356227-4">)</span><span class="p">.</span></code></pre><p>The difference here is that a check is made for two keys in each map argument.
│ │ │ │ +The other keys are ignored.</p><p>Finally, let us return the resulting color in <code class="inline">blend/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">blend</span><span class="p" data-group-id="5584957888-1">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="n">Alpha</span><span class="p" data-group-id="5584957888-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Alpha</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Dst</span><span class="p" data-group-id="5584957888-2">#{</span><span class="w">
│ │ │ │ +        </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="nf">red</span><span class="p" data-group-id="5584957888-3">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="5584957888-3">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="nf">green</span><span class="p" data-group-id="5584957888-4">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="5584957888-4">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="nf">blue</span><span class="p" data-group-id="5584957888-5">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="5584957888-5">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │          </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Alpha</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7017218739-2">}</span><span class="p">;</span></code></pre><p>The <code class="inline">Dst</code> map is updated with new channel values. The syntax for updating an
│ │ │ │ +    </span><span class="p" data-group-id="5584957888-2">}</span><span class="p">;</span></code></pre><p>The <code class="inline">Dst</code> map is updated with new channel values. The syntax for updating an
│ │ │ │  existing key with a new value is with the <code class="inline">:=</code> operator.</p><h2 id="standard-modules-and-manual-pages" class="section-heading">
│ │ │ │    <a href="#standard-modules-and-manual-pages" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Standard Modules and Manual Pages</span>
│ │ │ │  </h2>
│ │ │ │  <p>Erlang has many standard modules to help you do things. For example, the module
│ │ │ │ @@ -347,24 +347,24 @@
│ │ │ │    <a href="#writing-output-to-a-terminal" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Writing Output to a Terminal</span>
│ │ │ │  </h2>
│ │ │ │  <p>It is nice to be able to do formatted output in examples, so the next example
│ │ │ │  shows a simple way to use the <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> function. Like all other exported
│ │ │ │ -functions, you can test the <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> function in the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">31&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9388205817-1">(</span><span class="s">&quot;hello world</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9388205817-2">[</span><span class="p" data-group-id="9388205817-2">]</span><span class="p" data-group-id="9388205817-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +functions, you can test the <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> function in the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">31&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2497371159-1">(</span><span class="s">&quot;hello world</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2497371159-2">[</span><span class="p" data-group-id="2497371159-2">]</span><span class="p" data-group-id="2497371159-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span><span class="w"> </span><span class="ss">world</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">32&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9388205817-3">(</span><span class="s">&quot;this outputs one Erlang term: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9388205817-4">[</span><span class="ss">hello</span><span class="p" data-group-id="9388205817-4">]</span><span class="p" data-group-id="9388205817-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">32&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2497371159-3">(</span><span class="s">&quot;this outputs one Erlang term: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2497371159-4">[</span><span class="ss">hello</span><span class="p" data-group-id="2497371159-4">]</span><span class="p" data-group-id="2497371159-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">this</span><span class="w"> </span><span class="ss">outputs</span><span class="w"> </span><span class="ss">one</span><span class="w"> </span><span class="n">Erlang</span><span class="w"> </span><span class="nc">term</span><span class="p">:</span><span class="w"> </span><span class="ss">hello</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">33&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9388205817-5">(</span><span class="s">&quot;this outputs two Erlang terms: </span><span class="si">~w</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9388205817-6">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">world</span><span class="p" data-group-id="9388205817-6">]</span><span class="p" data-group-id="9388205817-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">33&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2497371159-5">(</span><span class="s">&quot;this outputs two Erlang terms: </span><span class="si">~w</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2497371159-6">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">world</span><span class="p" data-group-id="2497371159-6">]</span><span class="p" data-group-id="2497371159-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">this</span><span class="w"> </span><span class="ss">outputs</span><span class="w"> </span><span class="ss">two</span><span class="w"> </span><span class="n">Erlang</span><span class="w"> </span><span class="nc">terms</span><span class="p">:</span><span class="w"> </span><span class="ss">helloworld</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">34&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9388205817-7">(</span><span class="s">&quot;this outputs two Erlang terms: </span><span class="si">~w</span><span class="s"> </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9388205817-8">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">world</span><span class="p" data-group-id="9388205817-8">]</span><span class="p" data-group-id="9388205817-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">34&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2497371159-7">(</span><span class="s">&quot;this outputs two Erlang terms: </span><span class="si">~w</span><span class="s"> </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2497371159-8">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">world</span><span class="p" data-group-id="2497371159-8">]</span><span class="p" data-group-id="2497371159-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">this</span><span class="w"> </span><span class="ss">outputs</span><span class="w"> </span><span class="ss">two</span><span class="w"> </span><span class="n">Erlang</span><span class="w"> </span><span class="nc">terms</span><span class="p">:</span><span class="w"> </span><span class="ss">hello</span><span class="w"> </span><span class="ss">world</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>The function <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> (that is, <code class="inline">format</code> with two arguments) takes two lists.
│ │ │ │  The first one is nearly always a list written between <code class="inline">&quot; &quot;</code>. This list is printed
│ │ │ │  out as it is, except that each <code class="inline">~w</code> is replaced by a term taken in order from the
│ │ │ │  second list. Each <code class="inline">~n</code> is replaced by a new line. The <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> function
│ │ │ │  itself returns the atom <code class="inline">ok</code> if everything goes as planned. Like other functions
│ │ │ │  in Erlang, it crashes if an error occurs. This is not a fault in Erlang, it is a
│ │ │ │ @@ -378,34 +378,34 @@
│ │ │ │    <span class="text">A Larger Example</span>
│ │ │ │  </h2>
│ │ │ │  <p>Now for a larger example to consolidate what you have learnt so far. Assume that
│ │ │ │  you have a list of temperature readings from a number of cities in the world.
│ │ │ │  Some of them are in Celsius and some in Fahrenheit (as in the previous list).
│ │ │ │  First let us convert them all to Celsius, then let us print the data neatly.</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% This module is in file tut5.erl</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0724581968-1">(</span><span class="ss">tut5</span><span class="p" data-group-id="0724581968-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0724581968-2">(</span><span class="p" data-group-id="0724581968-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0724581968-3">]</span><span class="p" data-group-id="0724581968-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1917714265-1">(</span><span class="ss">tut5</span><span class="p" data-group-id="1917714265-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1917714265-2">(</span><span class="p" data-group-id="1917714265-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1917714265-3">]</span><span class="p" data-group-id="1917714265-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% Only this function is exported</span><span class="w">
│ │ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="0724581968-4">(</span><span class="p" data-group-id="0724581968-5">[</span><span class="p" data-group-id="0724581968-5">]</span><span class="p" data-group-id="0724581968-4">)</span><span class="p">-&gt;</span><span class="w">                        </span><span class="c1">% No output for an empty list</span><span class="w">
│ │ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="1917714265-4">(</span><span class="p" data-group-id="1917714265-5">[</span><span class="p" data-group-id="1917714265-5">]</span><span class="p" data-group-id="1917714265-4">)</span><span class="p">-&gt;</span><span class="w">                        </span><span class="c1">% No output for an empty list</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="0724581968-6">(</span><span class="p" data-group-id="0724581968-7">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0724581968-7">]</span><span class="p" data-group-id="0724581968-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="0724581968-8">(</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="0724581968-9">(</span><span class="n">City</span><span class="p" data-group-id="0724581968-9">)</span><span class="p" data-group-id="0724581968-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">format_temps</span><span class="p" data-group-id="0724581968-10">(</span><span class="n">Rest</span><span class="p" data-group-id="0724581968-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="0724581968-11">(</span><span class="p" data-group-id="0724581968-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0724581968-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0724581968-13">}</span><span class="p" data-group-id="0724581968-12">}</span><span class="p" data-group-id="0724581968-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% No conversion needed</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0724581968-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0724581968-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0724581968-15">}</span><span class="p" data-group-id="0724581968-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="0724581968-16">(</span><span class="p" data-group-id="0724581968-17">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0724581968-18">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0724581968-18">}</span><span class="p" data-group-id="0724581968-17">}</span><span class="p" data-group-id="0724581968-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Do the conversion</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0724581968-19">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0724581968-20">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0724581968-21">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="0724581968-21">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="0724581968-20">}</span><span class="p" data-group-id="0724581968-19">}</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="0724581968-22">(</span><span class="p" data-group-id="0724581968-23">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0724581968-24">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0724581968-24">}</span><span class="p" data-group-id="0724581968-23">}</span><span class="p" data-group-id="0724581968-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0724581968-25">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0724581968-26">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0724581968-26">]</span><span class="p" data-group-id="0724581968-25">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">35&gt; </span><span class="nf">c</span><span class="p" data-group-id="5841612068-1">(</span><span class="ss">tut5</span><span class="p" data-group-id="5841612068-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5841612068-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut5</span><span class="p" data-group-id="5841612068-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">36&gt; </span><span class="nc">tut5</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="5841612068-3">(</span><span class="p" data-group-id="5841612068-4">[</span><span class="p" data-group-id="5841612068-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5841612068-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="5841612068-6">}</span><span class="p" data-group-id="5841612068-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5841612068-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5841612068-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="5841612068-8">}</span><span class="p" data-group-id="5841612068-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5841612068-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5841612068-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="5841612068-10">}</span><span class="p" data-group-id="5841612068-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5841612068-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5841612068-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="5841612068-12">}</span><span class="p" data-group-id="5841612068-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5841612068-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5841612068-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="5841612068-14">}</span><span class="p" data-group-id="5841612068-13">}</span><span class="p" data-group-id="5841612068-4">]</span><span class="p" data-group-id="5841612068-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="1917714265-6">(</span><span class="p" data-group-id="1917714265-7">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1917714265-7">]</span><span class="p" data-group-id="1917714265-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="1917714265-8">(</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="1917714265-9">(</span><span class="n">City</span><span class="p" data-group-id="1917714265-9">)</span><span class="p" data-group-id="1917714265-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">format_temps</span><span class="p" data-group-id="1917714265-10">(</span><span class="n">Rest</span><span class="p" data-group-id="1917714265-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="1917714265-11">(</span><span class="p" data-group-id="1917714265-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1917714265-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="1917714265-13">}</span><span class="p" data-group-id="1917714265-12">}</span><span class="p" data-group-id="1917714265-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% No conversion needed</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1917714265-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1917714265-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="1917714265-15">}</span><span class="p" data-group-id="1917714265-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="1917714265-16">(</span><span class="p" data-group-id="1917714265-17">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1917714265-18">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="1917714265-18">}</span><span class="p" data-group-id="1917714265-17">}</span><span class="p" data-group-id="1917714265-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Do the conversion</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1917714265-19">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1917714265-20">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1917714265-21">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="1917714265-21">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="1917714265-20">}</span><span class="p" data-group-id="1917714265-19">}</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="1917714265-22">(</span><span class="p" data-group-id="1917714265-23">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1917714265-24">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="1917714265-24">}</span><span class="p" data-group-id="1917714265-23">}</span><span class="p" data-group-id="1917714265-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1917714265-25">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1917714265-26">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="1917714265-26">]</span><span class="p" data-group-id="1917714265-25">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">35&gt; </span><span class="nf">c</span><span class="p" data-group-id="3075444191-1">(</span><span class="ss">tut5</span><span class="p" data-group-id="3075444191-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3075444191-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut5</span><span class="p" data-group-id="3075444191-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">36&gt; </span><span class="nc">tut5</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="3075444191-3">(</span><span class="p" data-group-id="3075444191-4">[</span><span class="p" data-group-id="3075444191-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3075444191-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="3075444191-6">}</span><span class="p" data-group-id="3075444191-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3075444191-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3075444191-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="3075444191-8">}</span><span class="p" data-group-id="3075444191-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3075444191-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3075444191-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="3075444191-10">}</span><span class="p" data-group-id="3075444191-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3075444191-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3075444191-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="3075444191-12">}</span><span class="p" data-group-id="3075444191-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3075444191-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3075444191-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="3075444191-14">}</span><span class="p" data-group-id="3075444191-13">}</span><span class="p" data-group-id="3075444191-4">]</span><span class="p" data-group-id="3075444191-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">moscow</span><span class="w">          </span><span class="o">-</span><span class="mi">10</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">cape_town</span><span class="w">       </span><span class="mf">21.11111111111111</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">stockholm</span><span class="w">       </span><span class="o">-</span><span class="mi">4</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">paris</span><span class="w">           </span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">london</span><span class="w">          </span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>Before looking at how this program works, notice that a few comments are added
│ │ │ │  to the code. A comment starts with a %-character and goes on to the end of the
│ │ │ │ @@ -433,28 +433,28 @@
│ │ │ │    <a href="#matching-guards-and-scope-of-variables" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Matching, Guards, and Scope of Variables</span>
│ │ │ │  </h2>
│ │ │ │  <p>It can be useful to find the maximum and minimum temperature in lists like this.
│ │ │ │  Before extending the program to do this, let us look at functions for finding
│ │ │ │ -the maximum value of the elements in a list:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5964183830-1">(</span><span class="ss">tut6</span><span class="p" data-group-id="5964183830-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5964183830-2">(</span><span class="p" data-group-id="5964183830-3">[</span><span class="ss">list_max</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5964183830-3">]</span><span class="p" data-group-id="5964183830-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +the maximum value of the elements in a list:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7284910965-1">(</span><span class="ss">tut6</span><span class="p" data-group-id="7284910965-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7284910965-2">(</span><span class="p" data-group-id="7284910965-3">[</span><span class="ss">list_max</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7284910965-3">]</span><span class="p" data-group-id="7284910965-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">list_max</span><span class="p" data-group-id="5964183830-4">(</span><span class="p" data-group-id="5964183830-5">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="5964183830-5">]</span><span class="p" data-group-id="5964183830-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="nf">list_max</span><span class="p" data-group-id="5964183830-6">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Head</span><span class="p" data-group-id="5964183830-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">list_max</span><span class="p" data-group-id="7284910965-4">(</span><span class="p" data-group-id="7284910965-5">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="7284910965-5">]</span><span class="p" data-group-id="7284910965-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="nf">list_max</span><span class="p" data-group-id="7284910965-6">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Head</span><span class="p" data-group-id="7284910965-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">list_max</span><span class="p" data-group-id="5964183830-7">(</span><span class="p" data-group-id="5964183830-8">[</span><span class="p" data-group-id="5964183830-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="5964183830-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">list_max</span><span class="p" data-group-id="7284910965-7">(</span><span class="p" data-group-id="7284910965-8">[</span><span class="p" data-group-id="7284910965-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="7284910965-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Res</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">list_max</span><span class="p" data-group-id="5964183830-9">(</span><span class="p" data-group-id="5964183830-10">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="5964183830-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="5964183830-9">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Head</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Result_so_far</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">list_max</span><span class="p" data-group-id="5964183830-11">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Head</span><span class="p" data-group-id="5964183830-11">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">list_max</span><span class="p" data-group-id="5964183830-12">(</span><span class="p" data-group-id="5964183830-13">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="5964183830-13">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="5964183830-12">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">list_max</span><span class="p" data-group-id="5964183830-14">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="5964183830-14">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">37&gt; </span><span class="nf">c</span><span class="p" data-group-id="2195993188-1">(</span><span class="ss">tut6</span><span class="p" data-group-id="2195993188-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2195993188-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut6</span><span class="p" data-group-id="2195993188-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">38&gt; </span><span class="nc">tut6</span><span class="p">:</span><span class="nf">list_max</span><span class="p" data-group-id="2195993188-3">(</span><span class="p" data-group-id="2195993188-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2195993188-4">]</span><span class="p" data-group-id="2195993188-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">list_max</span><span class="p" data-group-id="7284910965-9">(</span><span class="p" data-group-id="7284910965-10">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="7284910965-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="7284910965-9">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Head</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Result_so_far</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">list_max</span><span class="p" data-group-id="7284910965-11">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Head</span><span class="p" data-group-id="7284910965-11">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">list_max</span><span class="p" data-group-id="7284910965-12">(</span><span class="p" data-group-id="7284910965-13">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="7284910965-13">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="7284910965-12">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">list_max</span><span class="p" data-group-id="7284910965-14">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="7284910965-14">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">37&gt; </span><span class="nf">c</span><span class="p" data-group-id="2198533129-1">(</span><span class="ss">tut6</span><span class="p" data-group-id="2198533129-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2198533129-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut6</span><span class="p" data-group-id="2198533129-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">38&gt; </span><span class="nc">tut6</span><span class="p">:</span><span class="nf">list_max</span><span class="p" data-group-id="2198533129-3">(</span><span class="p" data-group-id="2198533129-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2198533129-4">]</span><span class="p" data-group-id="2198533129-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">7</span></code></pre><p>First notice that two functions have the same name, <code class="inline">list_max</code>. However, each of
│ │ │ │  these takes a different number of arguments (parameters). In Erlang these are
│ │ │ │  regarded as completely different functions. Where you need to distinguish
│ │ │ │  between these functions, you write Name/Arity, where Name is the function name
│ │ │ │  and Arity is the number of arguments, in this case <code class="inline">list_max/1</code> and
│ │ │ │  <code class="inline">list_max/2</code>.</p><p>In this example you walk through a list &quot;carrying&quot; a value, in this case
│ │ │ │  <code class="inline">Result_so_far</code>. <code class="inline">list_max/1</code> simply assumes that the max value of the list is
│ │ │ │ @@ -483,180 +483,180 @@
│ │ │ │  </span><span class="mi">5</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">40&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no match of right hand side value 6</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">41&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no match of right hand side value 6</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">42&gt; </span><span class="n">N</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">6</span></code></pre><p>The use of the match operator is particularly useful for pulling apart Erlang
│ │ │ │ -terms and creating new ones.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">43&gt; </span><span class="p" data-group-id="9080987364-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9080987364-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9080987364-2">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9080987364-3">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="9080987364-3">}</span><span class="p" data-group-id="9080987364-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9080987364-4">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="9080987364-5">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">28</span><span class="p" data-group-id="9080987364-5">}</span><span class="p" data-group-id="9080987364-4">}</span><span class="w">
│ │ │ │ +terms and creating new ones.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">43&gt; </span><span class="p" data-group-id="5238221543-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5238221543-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5238221543-2">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5238221543-3">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="5238221543-3">}</span><span class="p" data-group-id="5238221543-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5238221543-4">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="5238221543-5">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">28</span><span class="p" data-group-id="5238221543-5">}</span><span class="p" data-group-id="5238221543-4">}</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">44&gt; </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">paris</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">45&gt; </span><span class="n">Y</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9080987364-6">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">28</span><span class="p" data-group-id="9080987364-6">}</span></code></pre><p>Here <code class="inline">X</code> gets the value <code class="inline">paris</code> and <code class="inline">Y</code> the value <code class="inline">{f,28}</code>.</p><p>If you try to do the same again with another city, an error is returned:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">46&gt; </span><span class="p" data-group-id="3640908533-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3640908533-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3640908533-2">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3640908533-3">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="3640908533-3">}</span><span class="p" data-group-id="3640908533-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5238221543-6">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">28</span><span class="p" data-group-id="5238221543-6">}</span></code></pre><p>Here <code class="inline">X</code> gets the value <code class="inline">paris</code> and <code class="inline">Y</code> the value <code class="inline">{f,28}</code>.</p><p>If you try to do the same again with another city, an error is returned:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">46&gt; </span><span class="p" data-group-id="5951286516-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5951286516-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5951286516-2">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5951286516-3">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="5951286516-3">}</span><span class="p" data-group-id="5951286516-2">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no match of right hand side value {london,{f,36}}</span></code></pre><p>Variables can also be used to improve the readability of programs. For example,
│ │ │ │ -in function <code class="inline">list_max/2</code> above, you can write:</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_max</span><span class="p" data-group-id="0310872020-1">(</span><span class="p" data-group-id="0310872020-2">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="0310872020-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="0310872020-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Head</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Result_so_far</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +in function <code class="inline">list_max/2</code> above, you can write:</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_max</span><span class="p" data-group-id="1419201872-1">(</span><span class="p" data-group-id="1419201872-2">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="1419201872-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="1419201872-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Head</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Result_so_far</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">New_result_far</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Head</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">list_max</span><span class="p" data-group-id="0310872020-3">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">New_result_far</span><span class="p" data-group-id="0310872020-3">)</span><span class="p">;</span></code></pre><p>This is possibly a little clearer.</p><h2 id="more-about-lists" class="section-heading">
│ │ │ │ +    </span><span class="nf">list_max</span><span class="p" data-group-id="1419201872-3">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">New_result_far</span><span class="p" data-group-id="1419201872-3">)</span><span class="p">;</span></code></pre><p>This is possibly a little clearer.</p><h2 id="more-about-lists" class="section-heading">
│ │ │ │    <a href="#more-about-lists" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">More About Lists</span>
│ │ │ │  </h2>
│ │ │ │ -<p>Remember that the <code class="inline">|</code> operator can be used to get the head of a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">47&gt; </span><span class="p" data-group-id="1726886326-1">[</span><span class="n">M1</span><span class="p">|</span><span class="n">T1</span><span class="p" data-group-id="1726886326-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1726886326-2">[</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="ss">rome</span><span class="p" data-group-id="1726886326-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1726886326-3">[</span><span class="ss">paris</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="1726886326-3">]</span><span class="w">
│ │ │ │ +<p>Remember that the <code class="inline">|</code> operator can be used to get the head of a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">47&gt; </span><span class="p" data-group-id="7578236926-1">[</span><span class="n">M1</span><span class="p">|</span><span class="n">T1</span><span class="p" data-group-id="7578236926-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7578236926-2">[</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="ss">rome</span><span class="p" data-group-id="7578236926-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7578236926-3">[</span><span class="ss">paris</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="7578236926-3">]</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">48&gt; </span><span class="n">M1</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">paris</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">49&gt; </span><span class="n">T1</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1726886326-4">[</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="1726886326-4">]</span></code></pre><p>The <code class="inline">|</code> operator can also be used to add a head to a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">50&gt; </span><span class="n">L1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1157650690-1">[</span><span class="ss">madrid</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="1157650690-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1157650690-2">[</span><span class="ss">madrid</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="1157650690-2">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7578236926-4">[</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="7578236926-4">]</span></code></pre><p>The <code class="inline">|</code> operator can also be used to add a head to a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">50&gt; </span><span class="n">L1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7890053698-1">[</span><span class="ss">madrid</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="7890053698-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7890053698-2">[</span><span class="ss">madrid</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="7890053698-2">]</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">51&gt; </span><span class="n">L1</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1157650690-3">[</span><span class="ss">madrid</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="1157650690-3">]</span></code></pre><p>Now an example of this when working with lists - reversing the order of a list:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9967523360-1">(</span><span class="ss">tut8</span><span class="p" data-group-id="9967523360-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7890053698-3">[</span><span class="ss">madrid</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="7890053698-3">]</span></code></pre><p>Now an example of this when working with lists - reversing the order of a list:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0078288859-1">(</span><span class="ss">tut8</span><span class="p" data-group-id="0078288859-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9967523360-2">(</span><span class="p" data-group-id="9967523360-3">[</span><span class="ss">reverse</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9967523360-3">]</span><span class="p" data-group-id="9967523360-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0078288859-2">(</span><span class="p" data-group-id="0078288859-3">[</span><span class="ss">reverse</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0078288859-3">]</span><span class="p" data-group-id="0078288859-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="9967523360-4">(</span><span class="n">List</span><span class="p" data-group-id="9967523360-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="9967523360-5">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9967523360-6">[</span><span class="p" data-group-id="9967523360-6">]</span><span class="p" data-group-id="9967523360-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="0078288859-4">(</span><span class="n">List</span><span class="p" data-group-id="0078288859-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="0078288859-5">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0078288859-6">[</span><span class="p" data-group-id="0078288859-6">]</span><span class="p" data-group-id="0078288859-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="9967523360-7">(</span><span class="p" data-group-id="9967523360-8">[</span><span class="n">Head</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9967523360-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="9967523360-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="9967523360-9">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9967523360-10">[</span><span class="n">Head</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="9967523360-10">]</span><span class="p" data-group-id="9967523360-9">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="9967523360-11">(</span><span class="p" data-group-id="9967523360-12">[</span><span class="p" data-group-id="9967523360-12">]</span><span class="p">,</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="9967523360-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Reversed_List</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">52&gt; </span><span class="nf">c</span><span class="p" data-group-id="0872232441-1">(</span><span class="ss">tut8</span><span class="p" data-group-id="0872232441-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0872232441-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut8</span><span class="p" data-group-id="0872232441-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">53&gt; </span><span class="nc">tut8</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="0872232441-3">(</span><span class="p" data-group-id="0872232441-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0872232441-4">]</span><span class="p" data-group-id="0872232441-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0872232441-5">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0872232441-5">]</span></code></pre><p>Consider how <code class="inline">Reversed_List</code> is built. It starts as [], then successively the
│ │ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="0078288859-7">(</span><span class="p" data-group-id="0078288859-8">[</span><span class="n">Head</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0078288859-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="0078288859-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="0078288859-9">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0078288859-10">[</span><span class="n">Head</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="0078288859-10">]</span><span class="p" data-group-id="0078288859-9">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="0078288859-11">(</span><span class="p" data-group-id="0078288859-12">[</span><span class="p" data-group-id="0078288859-12">]</span><span class="p">,</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="0078288859-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Reversed_List</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">52&gt; </span><span class="nf">c</span><span class="p" data-group-id="4802909750-1">(</span><span class="ss">tut8</span><span class="p" data-group-id="4802909750-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4802909750-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut8</span><span class="p" data-group-id="4802909750-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">53&gt; </span><span class="nc">tut8</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="4802909750-3">(</span><span class="p" data-group-id="4802909750-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4802909750-4">]</span><span class="p" data-group-id="4802909750-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4802909750-5">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4802909750-5">]</span></code></pre><p>Consider how <code class="inline">Reversed_List</code> is built. It starts as [], then successively the
│ │ │ │  heads are taken off of the list to be reversed and added to the
│ │ │ │ -<code class="inline">Reversed_List</code>, as shown in the following:</p><pre><code class="makeup erlang" translate="no"><span class="nf">reverse</span><span class="p" data-group-id="6431462421-1">(</span><span class="p" data-group-id="6431462421-2">[</span><span class="mi">1</span><span class="p">|</span><span class="p" data-group-id="6431462421-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6431462421-3">]</span><span class="p" data-group-id="6431462421-2">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6431462421-4">[</span><span class="p" data-group-id="6431462421-4">]</span><span class="p" data-group-id="6431462421-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="6431462421-5">(</span><span class="p" data-group-id="6431462421-6">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6431462421-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6431462421-7">[</span><span class="mi">1</span><span class="p">|</span><span class="p" data-group-id="6431462421-8">[</span><span class="p" data-group-id="6431462421-8">]</span><span class="p" data-group-id="6431462421-7">]</span><span class="p" data-group-id="6431462421-5">)</span><span class="w">
│ │ │ │ +<code class="inline">Reversed_List</code>, as shown in the following:</p><pre><code class="makeup erlang" translate="no"><span class="nf">reverse</span><span class="p" data-group-id="2250149389-1">(</span><span class="p" data-group-id="2250149389-2">[</span><span class="mi">1</span><span class="p">|</span><span class="p" data-group-id="2250149389-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2250149389-3">]</span><span class="p" data-group-id="2250149389-2">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2250149389-4">[</span><span class="p" data-group-id="2250149389-4">]</span><span class="p" data-group-id="2250149389-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="2250149389-5">(</span><span class="p" data-group-id="2250149389-6">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2250149389-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2250149389-7">[</span><span class="mi">1</span><span class="p">|</span><span class="p" data-group-id="2250149389-8">[</span><span class="p" data-group-id="2250149389-8">]</span><span class="p" data-group-id="2250149389-7">]</span><span class="p" data-group-id="2250149389-5">)</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="6431462421-9">(</span><span class="p" data-group-id="6431462421-10">[</span><span class="mi">2</span><span class="p">|</span><span class="p" data-group-id="6431462421-11">[</span><span class="mi">3</span><span class="p" data-group-id="6431462421-11">]</span><span class="p" data-group-id="6431462421-10">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6431462421-12">[</span><span class="mi">1</span><span class="p" data-group-id="6431462421-12">]</span><span class="p" data-group-id="6431462421-9">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="6431462421-13">(</span><span class="p" data-group-id="6431462421-14">[</span><span class="mi">3</span><span class="p" data-group-id="6431462421-14">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6431462421-15">[</span><span class="mi">2</span><span class="p">|</span><span class="p" data-group-id="6431462421-16">[</span><span class="mi">1</span><span class="p" data-group-id="6431462421-16">]</span><span class="p" data-group-id="6431462421-15">]</span><span class="p" data-group-id="6431462421-13">)</span><span class="w">
│ │ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="2250149389-9">(</span><span class="p" data-group-id="2250149389-10">[</span><span class="mi">2</span><span class="p">|</span><span class="p" data-group-id="2250149389-11">[</span><span class="mi">3</span><span class="p" data-group-id="2250149389-11">]</span><span class="p" data-group-id="2250149389-10">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2250149389-12">[</span><span class="mi">1</span><span class="p" data-group-id="2250149389-12">]</span><span class="p" data-group-id="2250149389-9">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="2250149389-13">(</span><span class="p" data-group-id="2250149389-14">[</span><span class="mi">3</span><span class="p" data-group-id="2250149389-14">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2250149389-15">[</span><span class="mi">2</span><span class="p">|</span><span class="p" data-group-id="2250149389-16">[</span><span class="mi">1</span><span class="p" data-group-id="2250149389-16">]</span><span class="p" data-group-id="2250149389-15">]</span><span class="p" data-group-id="2250149389-13">)</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="6431462421-17">(</span><span class="p" data-group-id="6431462421-18">[</span><span class="mi">3</span><span class="p">|</span><span class="p" data-group-id="6431462421-19">[</span><span class="p" data-group-id="6431462421-19">]</span><span class="p" data-group-id="6431462421-18">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6431462421-20">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6431462421-20">]</span><span class="p" data-group-id="6431462421-17">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="6431462421-21">(</span><span class="p" data-group-id="6431462421-22">[</span><span class="p" data-group-id="6431462421-22">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6431462421-23">[</span><span class="mi">3</span><span class="p">|</span><span class="p" data-group-id="6431462421-24">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6431462421-24">]</span><span class="p" data-group-id="6431462421-23">]</span><span class="p" data-group-id="6431462421-21">)</span><span class="w">
│ │ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="2250149389-17">(</span><span class="p" data-group-id="2250149389-18">[</span><span class="mi">3</span><span class="p">|</span><span class="p" data-group-id="2250149389-19">[</span><span class="p" data-group-id="2250149389-19">]</span><span class="p" data-group-id="2250149389-18">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2250149389-20">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2250149389-20">]</span><span class="p" data-group-id="2250149389-17">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="2250149389-21">(</span><span class="p" data-group-id="2250149389-22">[</span><span class="p" data-group-id="2250149389-22">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2250149389-23">[</span><span class="mi">3</span><span class="p">|</span><span class="p" data-group-id="2250149389-24">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2250149389-24">]</span><span class="p" data-group-id="2250149389-23">]</span><span class="p" data-group-id="2250149389-21">)</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="6431462421-25">(</span><span class="p" data-group-id="6431462421-26">[</span><span class="p" data-group-id="6431462421-26">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6431462421-27">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6431462421-27">]</span><span class="p" data-group-id="6431462421-25">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6431462421-28">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6431462421-28">]</span></code></pre><p>The module <code class="inline">lists</code> contains many functions for manipulating lists, for example,
│ │ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="2250149389-25">(</span><span class="p" data-group-id="2250149389-26">[</span><span class="p" data-group-id="2250149389-26">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2250149389-27">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2250149389-27">]</span><span class="p" data-group-id="2250149389-25">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2250149389-28">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2250149389-28">]</span></code></pre><p>The module <code class="inline">lists</code> contains many functions for manipulating lists, for example,
│ │ │ │  for reversing them. So before writing a list-manipulating function it is a good
│ │ │ │  idea to check if one has not already been written for you (see the <a href="../../../lib/stdlib/doc/html/lists.html"><code class="inline">lists</code></a> manual
│ │ │ │  page in STDLIB).</p><p>Now let us get back to the cities and temperatures, but take a more structured
│ │ │ │ -approach this time. First let us convert the whole list to Celsius as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3073591670-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="3073591670-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3073591670-2">(</span><span class="p" data-group-id="3073591670-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3073591670-3">]</span><span class="p" data-group-id="3073591670-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +approach this time. First let us convert the whole list to Celsius as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1634405883-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="1634405883-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1634405883-2">(</span><span class="p" data-group-id="1634405883-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1634405883-3">]</span><span class="p" data-group-id="1634405883-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="3073591670-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="3073591670-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3073591670-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="3073591670-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="1634405883-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="1634405883-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1634405883-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="1634405883-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3073591670-6">(</span><span class="p" data-group-id="3073591670-7">[</span><span class="p" data-group-id="3073591670-8">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3073591670-9">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="3073591670-9">}</span><span class="p" data-group-id="3073591670-8">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3073591670-7">]</span><span class="p" data-group-id="3073591670-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3073591670-10">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3073591670-11">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3073591670-12">(</span><span class="n">F</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="3073591670-12">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="3073591670-11">}</span><span class="p" data-group-id="3073591670-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3073591670-13">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3073591670-14">(</span><span class="n">Rest</span><span class="p" data-group-id="3073591670-14">)</span><span class="p" data-group-id="3073591670-13">]</span><span class="p">;</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3073591670-15">(</span><span class="p" data-group-id="3073591670-16">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3073591670-16">]</span><span class="p" data-group-id="3073591670-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3073591670-17">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3073591670-18">(</span><span class="n">Rest</span><span class="p" data-group-id="3073591670-18">)</span><span class="p" data-group-id="3073591670-17">]</span><span class="p">;</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3073591670-19">(</span><span class="p" data-group-id="3073591670-20">[</span><span class="p" data-group-id="3073591670-20">]</span><span class="p" data-group-id="3073591670-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3073591670-21">[</span><span class="p" data-group-id="3073591670-21">]</span><span class="p">.</span></code></pre><p>Test the function:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">54&gt; </span><span class="nf">c</span><span class="p" data-group-id="0358397623-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="0358397623-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0358397623-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut7</span><span class="p" data-group-id="0358397623-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">55&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="0358397623-3">(</span><span class="p" data-group-id="0358397623-4">[</span><span class="p" data-group-id="0358397623-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0358397623-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="0358397623-6">}</span><span class="p" data-group-id="0358397623-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0358397623-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0358397623-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="0358397623-8">}</span><span class="p" data-group-id="0358397623-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0358397623-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0358397623-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="0358397623-10">}</span><span class="p" data-group-id="0358397623-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0358397623-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0358397623-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="0358397623-12">}</span><span class="p" data-group-id="0358397623-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0358397623-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0358397623-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="0358397623-14">}</span><span class="p" data-group-id="0358397623-13">}</span><span class="p" data-group-id="0358397623-4">]</span><span class="p" data-group-id="0358397623-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0358397623-15">[</span><span class="p" data-group-id="0358397623-16">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="0358397623-17">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="0358397623-17">}</span><span class="p" data-group-id="0358397623-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="0358397623-18">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="0358397623-19">{</span><span class="ss">c</span><span class="p">,</span><span class="mf">21.11111111111111</span><span class="p" data-group-id="0358397623-19">}</span><span class="p" data-group-id="0358397623-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="0358397623-20">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="0358397623-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="0358397623-21">}</span><span class="p" data-group-id="0358397623-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="0358397623-22">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="0358397623-23">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="p" data-group-id="0358397623-23">}</span><span class="p" data-group-id="0358397623-22">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="0358397623-24">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="0358397623-25">{</span><span class="ss">c</span><span class="p">,</span><span class="mf">2.2222222222222223</span><span class="p" data-group-id="0358397623-25">}</span><span class="p" data-group-id="0358397623-24">}</span><span class="p" data-group-id="0358397623-15">]</span></code></pre><p>Explanation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">format_temps</span><span class="p" data-group-id="6836091726-1">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="6836091726-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="6836091726-2">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="6836091726-2">)</span><span class="p">.</span></code></pre><p>Here <code class="inline">format_temps/1</code> calls <code class="inline">convert_list_to_c/1</code>. <code class="inline">convert_list_to_c/1</code> takes
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1634405883-6">(</span><span class="p" data-group-id="1634405883-7">[</span><span class="p" data-group-id="1634405883-8">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1634405883-9">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="1634405883-9">}</span><span class="p" data-group-id="1634405883-8">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1634405883-7">]</span><span class="p" data-group-id="1634405883-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1634405883-10">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1634405883-11">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1634405883-12">(</span><span class="n">F</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="1634405883-12">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="1634405883-11">}</span><span class="p" data-group-id="1634405883-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1634405883-13">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1634405883-14">(</span><span class="n">Rest</span><span class="p" data-group-id="1634405883-14">)</span><span class="p" data-group-id="1634405883-13">]</span><span class="p">;</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1634405883-15">(</span><span class="p" data-group-id="1634405883-16">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1634405883-16">]</span><span class="p" data-group-id="1634405883-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1634405883-17">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1634405883-18">(</span><span class="n">Rest</span><span class="p" data-group-id="1634405883-18">)</span><span class="p" data-group-id="1634405883-17">]</span><span class="p">;</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1634405883-19">(</span><span class="p" data-group-id="1634405883-20">[</span><span class="p" data-group-id="1634405883-20">]</span><span class="p" data-group-id="1634405883-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1634405883-21">[</span><span class="p" data-group-id="1634405883-21">]</span><span class="p">.</span></code></pre><p>Test the function:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">54&gt; </span><span class="nf">c</span><span class="p" data-group-id="5447306529-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="5447306529-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5447306529-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut7</span><span class="p" data-group-id="5447306529-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">55&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="5447306529-3">(</span><span class="p" data-group-id="5447306529-4">[</span><span class="p" data-group-id="5447306529-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5447306529-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="5447306529-6">}</span><span class="p" data-group-id="5447306529-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5447306529-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5447306529-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="5447306529-8">}</span><span class="p" data-group-id="5447306529-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5447306529-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5447306529-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="5447306529-10">}</span><span class="p" data-group-id="5447306529-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5447306529-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5447306529-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="5447306529-12">}</span><span class="p" data-group-id="5447306529-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5447306529-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5447306529-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="5447306529-14">}</span><span class="p" data-group-id="5447306529-13">}</span><span class="p" data-group-id="5447306529-4">]</span><span class="p" data-group-id="5447306529-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5447306529-15">[</span><span class="p" data-group-id="5447306529-16">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="5447306529-17">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="5447306529-17">}</span><span class="p" data-group-id="5447306529-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5447306529-18">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="5447306529-19">{</span><span class="ss">c</span><span class="p">,</span><span class="mf">21.11111111111111</span><span class="p" data-group-id="5447306529-19">}</span><span class="p" data-group-id="5447306529-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5447306529-20">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="5447306529-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="5447306529-21">}</span><span class="p" data-group-id="5447306529-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5447306529-22">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="5447306529-23">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="p" data-group-id="5447306529-23">}</span><span class="p" data-group-id="5447306529-22">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5447306529-24">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="5447306529-25">{</span><span class="ss">c</span><span class="p">,</span><span class="mf">2.2222222222222223</span><span class="p" data-group-id="5447306529-25">}</span><span class="p" data-group-id="5447306529-24">}</span><span class="p" data-group-id="5447306529-15">]</span></code></pre><p>Explanation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">format_temps</span><span class="p" data-group-id="2179358711-1">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="2179358711-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="2179358711-2">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="2179358711-2">)</span><span class="p">.</span></code></pre><p>Here <code class="inline">format_temps/1</code> calls <code class="inline">convert_list_to_c/1</code>. <code class="inline">convert_list_to_c/1</code> takes
│ │ │ │  off the head of the <code class="inline">List_of_cities</code>, converts it to Celsius if needed. The <code class="inline">|</code>
│ │ │ │ -operator is used to add the (maybe converted) value to the rest of the list:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0415164302-1">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0415164302-2">(</span><span class="n">Rest</span><span class="p" data-group-id="0415164302-2">)</span><span class="p" data-group-id="0415164302-1">]</span><span class="p">;</span></code></pre><p>or:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2291206381-1">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="2291206381-2">(</span><span class="n">Rest</span><span class="p" data-group-id="2291206381-2">)</span><span class="p" data-group-id="2291206381-1">]</span><span class="p">;</span></code></pre><p>This is done until the end of the list is reached, that is, the list is empty:</p><pre><code class="makeup erlang" translate="no"><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7423373495-1">(</span><span class="p" data-group-id="7423373495-2">[</span><span class="p" data-group-id="7423373495-2">]</span><span class="p" data-group-id="7423373495-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7423373495-3">[</span><span class="p" data-group-id="7423373495-3">]</span><span class="p">.</span></code></pre><p>Now when the list is converted, a function to print it is added:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7675095550-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="7675095550-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7675095550-2">(</span><span class="p" data-group-id="7675095550-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7675095550-3">]</span><span class="p" data-group-id="7675095550-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="7675095550-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="7675095550-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Converted_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7675095550-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="7675095550-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="7675095550-6">(</span><span class="n">Converted_List</span><span class="p" data-group-id="7675095550-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7675095550-7">(</span><span class="p" data-group-id="7675095550-8">[</span><span class="p" data-group-id="7675095550-9">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7675095550-10">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="7675095550-10">}</span><span class="p" data-group-id="7675095550-9">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7675095550-8">]</span><span class="p" data-group-id="7675095550-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7675095550-11">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7675095550-12">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7675095550-13">(</span><span class="n">F</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="7675095550-13">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="7675095550-12">}</span><span class="p" data-group-id="7675095550-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7675095550-14">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7675095550-15">(</span><span class="n">Rest</span><span class="p" data-group-id="7675095550-15">)</span><span class="p" data-group-id="7675095550-14">]</span><span class="p">;</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7675095550-16">(</span><span class="p" data-group-id="7675095550-17">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7675095550-17">]</span><span class="p" data-group-id="7675095550-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7675095550-18">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7675095550-19">(</span><span class="n">Rest</span><span class="p" data-group-id="7675095550-19">)</span><span class="p" data-group-id="7675095550-18">]</span><span class="p">;</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7675095550-20">(</span><span class="p" data-group-id="7675095550-21">[</span><span class="p" data-group-id="7675095550-21">]</span><span class="p" data-group-id="7675095550-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7675095550-22">[</span><span class="p" data-group-id="7675095550-22">]</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="7675095550-23">(</span><span class="p" data-group-id="7675095550-24">[</span><span class="p" data-group-id="7675095550-25">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7675095550-26">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7675095550-26">}</span><span class="p" data-group-id="7675095550-25">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7675095550-24">]</span><span class="p" data-group-id="7675095550-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7675095550-27">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7675095550-28">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7675095550-28">]</span><span class="p" data-group-id="7675095550-27">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="7675095550-29">(</span><span class="n">Rest</span><span class="p" data-group-id="7675095550-29">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="7675095550-30">(</span><span class="p" data-group-id="7675095550-31">[</span><span class="p" data-group-id="7675095550-31">]</span><span class="p" data-group-id="7675095550-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ok</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">56&gt; </span><span class="nf">c</span><span class="p" data-group-id="4125526246-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="4125526246-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4125526246-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut7</span><span class="p" data-group-id="4125526246-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">57&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="4125526246-3">(</span><span class="p" data-group-id="4125526246-4">[</span><span class="p" data-group-id="4125526246-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4125526246-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="4125526246-6">}</span><span class="p" data-group-id="4125526246-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4125526246-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4125526246-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="4125526246-8">}</span><span class="p" data-group-id="4125526246-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4125526246-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4125526246-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="4125526246-10">}</span><span class="p" data-group-id="4125526246-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4125526246-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4125526246-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="4125526246-12">}</span><span class="p" data-group-id="4125526246-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4125526246-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4125526246-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="4125526246-14">}</span><span class="p" data-group-id="4125526246-13">}</span><span class="p" data-group-id="4125526246-4">]</span><span class="p" data-group-id="4125526246-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +operator is used to add the (maybe converted) value to the rest of the list:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5167118407-1">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5167118407-2">(</span><span class="n">Rest</span><span class="p" data-group-id="5167118407-2">)</span><span class="p" data-group-id="5167118407-1">]</span><span class="p">;</span></code></pre><p>or:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4446437745-1">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="4446437745-2">(</span><span class="n">Rest</span><span class="p" data-group-id="4446437745-2">)</span><span class="p" data-group-id="4446437745-1">]</span><span class="p">;</span></code></pre><p>This is done until the end of the list is reached, that is, the list is empty:</p><pre><code class="makeup erlang" translate="no"><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0912587772-1">(</span><span class="p" data-group-id="0912587772-2">[</span><span class="p" data-group-id="0912587772-2">]</span><span class="p" data-group-id="0912587772-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0912587772-3">[</span><span class="p" data-group-id="0912587772-3">]</span><span class="p">.</span></code></pre><p>Now when the list is converted, a function to print it is added:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8249976974-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="8249976974-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8249976974-2">(</span><span class="p" data-group-id="8249976974-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8249976974-3">]</span><span class="p" data-group-id="8249976974-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="8249976974-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="8249976974-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Converted_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="8249976974-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="8249976974-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="8249976974-6">(</span><span class="n">Converted_List</span><span class="p" data-group-id="8249976974-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="8249976974-7">(</span><span class="p" data-group-id="8249976974-8">[</span><span class="p" data-group-id="8249976974-9">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8249976974-10">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="8249976974-10">}</span><span class="p" data-group-id="8249976974-9">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="8249976974-8">]</span><span class="p" data-group-id="8249976974-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8249976974-11">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8249976974-12">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8249976974-13">(</span><span class="n">F</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="8249976974-13">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="8249976974-12">}</span><span class="p" data-group-id="8249976974-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8249976974-14">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="8249976974-15">(</span><span class="n">Rest</span><span class="p" data-group-id="8249976974-15">)</span><span class="p" data-group-id="8249976974-14">]</span><span class="p">;</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="8249976974-16">(</span><span class="p" data-group-id="8249976974-17">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="8249976974-17">]</span><span class="p" data-group-id="8249976974-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8249976974-18">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="8249976974-19">(</span><span class="n">Rest</span><span class="p" data-group-id="8249976974-19">)</span><span class="p" data-group-id="8249976974-18">]</span><span class="p">;</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="8249976974-20">(</span><span class="p" data-group-id="8249976974-21">[</span><span class="p" data-group-id="8249976974-21">]</span><span class="p" data-group-id="8249976974-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8249976974-22">[</span><span class="p" data-group-id="8249976974-22">]</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="8249976974-23">(</span><span class="p" data-group-id="8249976974-24">[</span><span class="p" data-group-id="8249976974-25">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8249976974-26">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8249976974-26">}</span><span class="p" data-group-id="8249976974-25">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="8249976974-24">]</span><span class="p" data-group-id="8249976974-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8249976974-27">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8249976974-28">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8249976974-28">]</span><span class="p" data-group-id="8249976974-27">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="8249976974-29">(</span><span class="n">Rest</span><span class="p" data-group-id="8249976974-29">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="8249976974-30">(</span><span class="p" data-group-id="8249976974-31">[</span><span class="p" data-group-id="8249976974-31">]</span><span class="p" data-group-id="8249976974-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ok</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">56&gt; </span><span class="nf">c</span><span class="p" data-group-id="9664356959-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="9664356959-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9664356959-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut7</span><span class="p" data-group-id="9664356959-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">57&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="9664356959-3">(</span><span class="p" data-group-id="9664356959-4">[</span><span class="p" data-group-id="9664356959-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9664356959-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="9664356959-6">}</span><span class="p" data-group-id="9664356959-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9664356959-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9664356959-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="9664356959-8">}</span><span class="p" data-group-id="9664356959-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9664356959-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9664356959-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="9664356959-10">}</span><span class="p" data-group-id="9664356959-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9664356959-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9664356959-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="9664356959-12">}</span><span class="p" data-group-id="9664356959-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9664356959-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9664356959-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="9664356959-14">}</span><span class="p" data-group-id="9664356959-13">}</span><span class="p" data-group-id="9664356959-4">]</span><span class="p" data-group-id="9664356959-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">moscow</span><span class="w">          </span><span class="o">-</span><span class="mi">10</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">cape_town</span><span class="w">       </span><span class="mf">21.11111111111111</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">stockholm</span><span class="w">       </span><span class="o">-</span><span class="mi">4</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">paris</span><span class="w">           </span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">london</span><span class="w">          </span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>Now a function has to be added to find the cities with the maximum and minimum
│ │ │ │  temperatures. The following program is not the most efficient way of doing this
│ │ │ │  as you walk through the list of cities four times. But it is better to first
│ │ │ │  strive for clarity and correctness and to make programs efficient only if
│ │ │ │ -needed.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7056683131-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="7056683131-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7056683131-2">(</span><span class="p" data-group-id="7056683131-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7056683131-3">]</span><span class="p" data-group-id="7056683131-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +needed.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5226444511-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="5226444511-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5226444511-2">(</span><span class="p" data-group-id="5226444511-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5226444511-3">]</span><span class="p" data-group-id="5226444511-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="7056683131-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="7056683131-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Converted_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7056683131-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="7056683131-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="7056683131-6">(</span><span class="n">Converted_List</span><span class="p" data-group-id="7056683131-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7056683131-7">{</span><span class="n">Max_city</span><span class="p">,</span><span class="w"> </span><span class="n">Min_city</span><span class="p" data-group-id="7056683131-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="7056683131-8">(</span><span class="n">Converted_List</span><span class="p" data-group-id="7056683131-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">print_max_and_min</span><span class="p" data-group-id="7056683131-9">(</span><span class="n">Max_city</span><span class="p">,</span><span class="w"> </span><span class="n">Min_city</span><span class="p" data-group-id="7056683131-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7056683131-10">(</span><span class="p" data-group-id="7056683131-11">[</span><span class="p" data-group-id="7056683131-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7056683131-13">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7056683131-13">}</span><span class="p" data-group-id="7056683131-12">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7056683131-11">]</span><span class="p" data-group-id="7056683131-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7056683131-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7056683131-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7056683131-16">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="7056683131-16">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="7056683131-15">}</span><span class="p" data-group-id="7056683131-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7056683131-17">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7056683131-18">(</span><span class="n">Rest</span><span class="p" data-group-id="7056683131-18">)</span><span class="p" data-group-id="7056683131-17">]</span><span class="p">;</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7056683131-19">(</span><span class="p" data-group-id="7056683131-20">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7056683131-20">]</span><span class="p" data-group-id="7056683131-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7056683131-21">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7056683131-22">(</span><span class="n">Rest</span><span class="p" data-group-id="7056683131-22">)</span><span class="p" data-group-id="7056683131-21">]</span><span class="p">;</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7056683131-23">(</span><span class="p" data-group-id="7056683131-24">[</span><span class="p" data-group-id="7056683131-24">]</span><span class="p" data-group-id="7056683131-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7056683131-25">[</span><span class="p" data-group-id="7056683131-25">]</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="7056683131-26">(</span><span class="p" data-group-id="7056683131-27">[</span><span class="p" data-group-id="7056683131-28">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7056683131-29">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7056683131-29">}</span><span class="p" data-group-id="7056683131-28">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7056683131-27">]</span><span class="p" data-group-id="7056683131-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7056683131-30">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7056683131-31">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7056683131-31">]</span><span class="p" data-group-id="7056683131-30">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="7056683131-32">(</span><span class="n">Rest</span><span class="p" data-group-id="7056683131-32">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="7056683131-33">(</span><span class="p" data-group-id="7056683131-34">[</span><span class="p" data-group-id="7056683131-34">]</span><span class="p" data-group-id="7056683131-33">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="5226444511-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="5226444511-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Converted_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5226444511-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="5226444511-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="5226444511-6">(</span><span class="n">Converted_List</span><span class="p" data-group-id="5226444511-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5226444511-7">{</span><span class="n">Max_city</span><span class="p">,</span><span class="w"> </span><span class="n">Min_city</span><span class="p" data-group-id="5226444511-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5226444511-8">(</span><span class="n">Converted_List</span><span class="p" data-group-id="5226444511-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">print_max_and_min</span><span class="p" data-group-id="5226444511-9">(</span><span class="n">Max_city</span><span class="p">,</span><span class="w"> </span><span class="n">Min_city</span><span class="p" data-group-id="5226444511-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5226444511-10">(</span><span class="p" data-group-id="5226444511-11">[</span><span class="p" data-group-id="5226444511-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5226444511-13">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5226444511-13">}</span><span class="p" data-group-id="5226444511-12">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5226444511-11">]</span><span class="p" data-group-id="5226444511-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5226444511-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5226444511-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5226444511-16">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="5226444511-16">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="5226444511-15">}</span><span class="p" data-group-id="5226444511-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5226444511-17">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5226444511-18">(</span><span class="n">Rest</span><span class="p" data-group-id="5226444511-18">)</span><span class="p" data-group-id="5226444511-17">]</span><span class="p">;</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5226444511-19">(</span><span class="p" data-group-id="5226444511-20">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5226444511-20">]</span><span class="p" data-group-id="5226444511-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5226444511-21">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5226444511-22">(</span><span class="n">Rest</span><span class="p" data-group-id="5226444511-22">)</span><span class="p" data-group-id="5226444511-21">]</span><span class="p">;</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5226444511-23">(</span><span class="p" data-group-id="5226444511-24">[</span><span class="p" data-group-id="5226444511-24">]</span><span class="p" data-group-id="5226444511-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5226444511-25">[</span><span class="p" data-group-id="5226444511-25">]</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="5226444511-26">(</span><span class="p" data-group-id="5226444511-27">[</span><span class="p" data-group-id="5226444511-28">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5226444511-29">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5226444511-29">}</span><span class="p" data-group-id="5226444511-28">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5226444511-27">]</span><span class="p" data-group-id="5226444511-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5226444511-30">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5226444511-31">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5226444511-31">]</span><span class="p" data-group-id="5226444511-30">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="5226444511-32">(</span><span class="n">Rest</span><span class="p" data-group-id="5226444511-32">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="5226444511-33">(</span><span class="p" data-group-id="5226444511-34">[</span><span class="p" data-group-id="5226444511-34">]</span><span class="p" data-group-id="5226444511-33">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="7056683131-35">(</span><span class="p" data-group-id="7056683131-36">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7056683131-36">]</span><span class="p" data-group-id="7056683131-35">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="7056683131-37">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="n">City</span><span class="p" data-group-id="7056683131-37">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5226444511-35">(</span><span class="p" data-group-id="5226444511-36">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5226444511-36">]</span><span class="p" data-group-id="5226444511-35">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5226444511-37">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="n">City</span><span class="p" data-group-id="5226444511-37">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="7056683131-38">(</span><span class="p" data-group-id="7056683131-39">[</span><span class="p" data-group-id="7056683131-40">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7056683131-41">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7056683131-41">}</span><span class="p" data-group-id="7056683131-40">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7056683131-39">]</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="7056683131-42">{</span><span class="n">Max_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7056683131-43">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_Temp</span><span class="p" data-group-id="7056683131-43">}</span><span class="p" data-group-id="7056683131-42">}</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="7056683131-44">{</span><span class="n">Min_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7056683131-45">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_Temp</span><span class="p" data-group-id="7056683131-45">}</span><span class="p" data-group-id="7056683131-44">}</span><span class="p" data-group-id="7056683131-38">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5226444511-38">(</span><span class="p" data-group-id="5226444511-39">[</span><span class="p" data-group-id="5226444511-40">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5226444511-41">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5226444511-41">}</span><span class="p" data-group-id="5226444511-40">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5226444511-39">]</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="5226444511-42">{</span><span class="n">Max_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5226444511-43">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_Temp</span><span class="p" data-group-id="5226444511-43">}</span><span class="p" data-group-id="5226444511-42">}</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="5226444511-44">{</span><span class="n">Min_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5226444511-45">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_Temp</span><span class="p" data-group-id="5226444511-45">}</span><span class="p" data-group-id="5226444511-44">}</span><span class="p" data-group-id="5226444511-38">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">Temp</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Max_Temp</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Max_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7056683131-46">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7056683131-47">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7056683131-47">}</span><span class="p" data-group-id="7056683131-46">}</span><span class="p">;</span><span class="w">           </span><span class="c1">% Change</span><span class="w">
│ │ │ │ +            </span><span class="n">Max_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5226444511-46">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5226444511-47">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5226444511-47">}</span><span class="p" data-group-id="5226444511-46">}</span><span class="p">;</span><span class="w">           </span><span class="c1">% Change</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Max_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7056683131-48">{</span><span class="n">Max_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7056683131-49">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_Temp</span><span class="p" data-group-id="7056683131-49">}</span><span class="p" data-group-id="7056683131-48">}</span><span class="w"> </span><span class="c1">% Unchanged</span><span class="w">
│ │ │ │ +            </span><span class="n">Max_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5226444511-48">{</span><span class="n">Max_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5226444511-49">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_Temp</span><span class="p" data-group-id="5226444511-49">}</span><span class="p" data-group-id="5226444511-48">}</span><span class="w"> </span><span class="c1">% Unchanged</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │           </span><span class="n">Temp</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Min_Temp</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Min_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7056683131-50">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7056683131-51">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7056683131-51">}</span><span class="p" data-group-id="7056683131-50">}</span><span class="p">;</span><span class="w">           </span><span class="c1">% Change</span><span class="w">
│ │ │ │ +            </span><span class="n">Min_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5226444511-50">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5226444511-51">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5226444511-51">}</span><span class="p" data-group-id="5226444511-50">}</span><span class="p">;</span><span class="w">           </span><span class="c1">% Change</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Min_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7056683131-52">{</span><span class="n">Min_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7056683131-53">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_Temp</span><span class="p" data-group-id="7056683131-53">}</span><span class="p" data-group-id="7056683131-52">}</span><span class="w"> </span><span class="c1">% Unchanged</span><span class="w">
│ │ │ │ +            </span><span class="n">Min_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5226444511-52">{</span><span class="n">Min_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5226444511-53">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_Temp</span><span class="p" data-group-id="5226444511-53">}</span><span class="p" data-group-id="5226444511-52">}</span><span class="w"> </span><span class="c1">% Unchanged</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="7056683131-54">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="7056683131-54">)</span><span class="p">;</span><span class="w">
│ │ │ │ +    </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5226444511-54">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="5226444511-54">)</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="7056683131-55">(</span><span class="p" data-group-id="7056683131-56">[</span><span class="p" data-group-id="7056683131-56">]</span><span class="p">,</span><span class="w"> </span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="7056683131-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7056683131-57">{</span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="7056683131-57">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5226444511-55">(</span><span class="p" data-group-id="5226444511-56">[</span><span class="p" data-group-id="5226444511-56">]</span><span class="p">,</span><span class="w"> </span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="5226444511-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5226444511-57">{</span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="5226444511-57">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">print_max_and_min</span><span class="p" data-group-id="7056683131-58">(</span><span class="p" data-group-id="7056683131-59">{</span><span class="n">Max_name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7056683131-60">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_temp</span><span class="p" data-group-id="7056683131-60">}</span><span class="p" data-group-id="7056683131-59">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7056683131-61">{</span><span class="n">Min_name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7056683131-62">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_temp</span><span class="p" data-group-id="7056683131-62">}</span><span class="p" data-group-id="7056683131-61">}</span><span class="p" data-group-id="7056683131-58">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7056683131-63">(</span><span class="s">&quot;Max temperature was </span><span class="si">~w</span><span class="s"> c in </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7056683131-64">[</span><span class="n">Max_temp</span><span class="p">,</span><span class="w"> </span><span class="n">Max_name</span><span class="p" data-group-id="7056683131-64">]</span><span class="p" data-group-id="7056683131-63">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7056683131-65">(</span><span class="s">&quot;Min temperature was </span><span class="si">~w</span><span class="s"> c in </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7056683131-66">[</span><span class="n">Min_temp</span><span class="p">,</span><span class="w"> </span><span class="n">Min_name</span><span class="p" data-group-id="7056683131-66">]</span><span class="p" data-group-id="7056683131-65">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">58&gt; </span><span class="nf">c</span><span class="p" data-group-id="2833942882-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="2833942882-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2833942882-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut7</span><span class="p" data-group-id="2833942882-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">59&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="2833942882-3">(</span><span class="p" data-group-id="2833942882-4">[</span><span class="p" data-group-id="2833942882-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2833942882-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="2833942882-6">}</span><span class="p" data-group-id="2833942882-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2833942882-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2833942882-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="2833942882-8">}</span><span class="p" data-group-id="2833942882-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2833942882-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2833942882-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="2833942882-10">}</span><span class="p" data-group-id="2833942882-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2833942882-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2833942882-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="2833942882-12">}</span><span class="p" data-group-id="2833942882-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2833942882-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2833942882-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="2833942882-14">}</span><span class="p" data-group-id="2833942882-13">}</span><span class="p" data-group-id="2833942882-4">]</span><span class="p" data-group-id="2833942882-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">print_max_and_min</span><span class="p" data-group-id="5226444511-58">(</span><span class="p" data-group-id="5226444511-59">{</span><span class="n">Max_name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5226444511-60">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_temp</span><span class="p" data-group-id="5226444511-60">}</span><span class="p" data-group-id="5226444511-59">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5226444511-61">{</span><span class="n">Min_name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5226444511-62">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_temp</span><span class="p" data-group-id="5226444511-62">}</span><span class="p" data-group-id="5226444511-61">}</span><span class="p" data-group-id="5226444511-58">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5226444511-63">(</span><span class="s">&quot;Max temperature was </span><span class="si">~w</span><span class="s"> c in </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5226444511-64">[</span><span class="n">Max_temp</span><span class="p">,</span><span class="w"> </span><span class="n">Max_name</span><span class="p" data-group-id="5226444511-64">]</span><span class="p" data-group-id="5226444511-63">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5226444511-65">(</span><span class="s">&quot;Min temperature was </span><span class="si">~w</span><span class="s"> c in </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5226444511-66">[</span><span class="n">Min_temp</span><span class="p">,</span><span class="w"> </span><span class="n">Min_name</span><span class="p" data-group-id="5226444511-66">]</span><span class="p" data-group-id="5226444511-65">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">58&gt; </span><span class="nf">c</span><span class="p" data-group-id="7356430003-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="7356430003-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7356430003-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut7</span><span class="p" data-group-id="7356430003-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">59&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="7356430003-3">(</span><span class="p" data-group-id="7356430003-4">[</span><span class="p" data-group-id="7356430003-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7356430003-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="7356430003-6">}</span><span class="p" data-group-id="7356430003-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7356430003-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7356430003-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="7356430003-8">}</span><span class="p" data-group-id="7356430003-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7356430003-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7356430003-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="7356430003-10">}</span><span class="p" data-group-id="7356430003-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7356430003-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7356430003-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="7356430003-12">}</span><span class="p" data-group-id="7356430003-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7356430003-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7356430003-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="7356430003-14">}</span><span class="p" data-group-id="7356430003-13">}</span><span class="p" data-group-id="7356430003-4">]</span><span class="p" data-group-id="7356430003-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">moscow</span><span class="w">          </span><span class="o">-</span><span class="mi">10</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">cape_town</span><span class="w">       </span><span class="mf">21.11111111111111</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">stockholm</span><span class="w">       </span><span class="o">-</span><span class="mi">4</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">paris</span><span class="w">           </span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">london</span><span class="w">          </span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="n">Max</span><span class="w"> </span><span class="ss">temperature</span><span class="w"> </span><span class="ss">was</span><span class="w"> </span><span class="mf">21.11111111111111</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">cape_town</span><span class="w">
│ │ │ │  </span><span class="n">Min</span><span class="w"> </span><span class="ss">temperature</span><span class="w"> </span><span class="ss">was</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">moscow</span><span class="w">
│ │ │ │ @@ -678,88 +678,88 @@
│ │ │ │          </span><span class="n">Action</span><span class="w"> </span><span class="mi">4</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>Notice that there is no <code class="inline">;</code> before <code class="inline">end</code>. Conditions do the same as guards, that
│ │ │ │  is, tests that succeed or fail. Erlang starts at the top and tests until it
│ │ │ │  finds a condition that succeeds. Then it evaluates (performs) the action
│ │ │ │  following the condition and ignores all other conditions and actions before the
│ │ │ │  <code class="inline">end</code>. If no condition matches, a run-time failure occurs. A condition that
│ │ │ │  always succeeds is the atom <code class="inline">true</code>. This is often used last in an <code class="inline">if</code>, meaning,
│ │ │ │ -do the action following the <code class="inline">true</code> if all other conditions have failed.</p><p>The following is a short program to show the workings of <code class="inline">if</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0223156978-1">(</span><span class="ss">tut9</span><span class="p" data-group-id="0223156978-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0223156978-2">(</span><span class="p" data-group-id="0223156978-3">[</span><span class="ss">test_if</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0223156978-3">]</span><span class="p" data-group-id="0223156978-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +do the action following the <code class="inline">true</code> if all other conditions have failed.</p><p>The following is a short program to show the workings of <code class="inline">if</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2255577056-1">(</span><span class="ss">tut9</span><span class="p" data-group-id="2255577056-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2255577056-2">(</span><span class="p" data-group-id="2255577056-3">[</span><span class="ss">test_if</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2255577056-3">]</span><span class="p" data-group-id="2255577056-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">test_if</span><span class="p" data-group-id="0223156978-4">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0223156978-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">test_if</span><span class="p" data-group-id="2255577056-4">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="2255577056-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0223156978-5">(</span><span class="s">&quot;A == 5</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0223156978-6">[</span><span class="p" data-group-id="0223156978-6">]</span><span class="p" data-group-id="0223156978-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2255577056-5">(</span><span class="s">&quot;A == 5</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2255577056-6">[</span><span class="p" data-group-id="2255577056-6">]</span><span class="p" data-group-id="2255577056-5">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="ss">a_equals_5</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">6</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0223156978-7">(</span><span class="s">&quot;B == 6</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0223156978-8">[</span><span class="p" data-group-id="0223156978-8">]</span><span class="p" data-group-id="0223156978-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2255577056-7">(</span><span class="s">&quot;B == 6</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2255577056-8">[</span><span class="p" data-group-id="2255577056-8">]</span><span class="p" data-group-id="2255577056-7">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="ss">b_equals_6</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">                      </span><span class="c1">%That is A equals 2 and B equals 3</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0223156978-9">(</span><span class="s">&quot;A == 2, B == 3</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0223156978-10">[</span><span class="p" data-group-id="0223156978-10">]</span><span class="p" data-group-id="0223156978-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2255577056-9">(</span><span class="s">&quot;A == 2, B == 3</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2255577056-10">[</span><span class="p" data-group-id="2255577056-10">]</span><span class="p" data-group-id="2255577056-9">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="ss">a_equals_2_b_equals_3</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">7</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">                     </span><span class="c1">%That is A equals 1 or B equals 7</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0223156978-11">(</span><span class="s">&quot;A == 1 ; B == 7</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0223156978-12">[</span><span class="p" data-group-id="0223156978-12">]</span><span class="p" data-group-id="0223156978-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2255577056-11">(</span><span class="s">&quot;A == 1 ; B == 7</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2255577056-12">[</span><span class="p" data-group-id="2255577056-12">]</span><span class="p" data-group-id="2255577056-11">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="ss">a_equals_1_or_b_equals_7</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Testing this program gives:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">60&gt; </span><span class="nf">c</span><span class="p" data-group-id="2502014810-1">(</span><span class="ss">tut9</span><span class="p" data-group-id="2502014810-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2502014810-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut9</span><span class="p" data-group-id="2502014810-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">61&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="2502014810-3">(</span><span class="mi">5</span><span class="p">,</span><span class="mi">33</span><span class="p" data-group-id="2502014810-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Testing this program gives:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">60&gt; </span><span class="nf">c</span><span class="p" data-group-id="7012790104-1">(</span><span class="ss">tut9</span><span class="p" data-group-id="7012790104-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7012790104-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut9</span><span class="p" data-group-id="7012790104-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">61&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="7012790104-3">(</span><span class="mi">5</span><span class="p">,</span><span class="mi">33</span><span class="p" data-group-id="7012790104-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │ │  </span><span class="ss">a_equals_5</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">62&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="2502014810-4">(</span><span class="mi">33</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2502014810-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">62&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="7012790104-4">(</span><span class="mi">33</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7012790104-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">6</span><span class="w">
│ │ │ │  </span><span class="ss">b_equals_6</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">63&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="2502014810-5">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="2502014810-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">63&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="7012790104-5">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="7012790104-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="w">
│ │ │ │  </span><span class="ss">a_equals_2_b_equals_3</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">64&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="2502014810-6">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="2502014810-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">64&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="7012790104-6">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="7012790104-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">7</span><span class="w">
│ │ │ │  </span><span class="ss">a_equals_1_or_b_equals_7</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">65&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="2502014810-7">(</span><span class="mi">33</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p" data-group-id="2502014810-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">65&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="7012790104-7">(</span><span class="mi">33</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p" data-group-id="7012790104-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">7</span><span class="w">
│ │ │ │  </span><span class="ss">a_equals_1_or_b_equals_7</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">66&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="2502014810-8">(</span><span class="mi">33</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="2502014810-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">66&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="7012790104-8">(</span><span class="mi">33</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="7012790104-8">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no true branch found when evaluating an if expression
│ │ │ │       in function  tut9:test_if/2 (tut9.erl, line 5)</span></code></pre><p>Notice that <code class="inline">tut9:test_if(33,33)</code> does not cause any condition to succeed. This
│ │ │ │  leads to the run time error <code class="inline">if_clause</code>, here nicely formatted by the shell. See
│ │ │ │  <a href="../../../lib/../system/doc/html/expressions.xhtml">Guard Sequences</a> for details of the many guard tests
│ │ │ │  available.</p><p><code class="inline">case</code> is another construct in Erlang. Recall that the <code class="inline">convert_length</code> function
│ │ │ │ -was written as:</p><pre><code class="makeup erlang" translate="no"><span class="nf">convert_length</span><span class="p" data-group-id="2903901978-1">(</span><span class="p" data-group-id="2903901978-2">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="2903901978-2">}</span><span class="p" data-group-id="2903901978-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2903901978-3">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="2903901978-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">convert_length</span><span class="p" data-group-id="2903901978-4">(</span><span class="p" data-group-id="2903901978-5">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2903901978-5">}</span><span class="p" data-group-id="2903901978-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2903901978-6">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="2903901978-6">}</span><span class="p">.</span></code></pre><p>The same program can also be written as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2280588188-1">(</span><span class="ss">tut10</span><span class="p" data-group-id="2280588188-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2280588188-2">(</span><span class="p" data-group-id="2280588188-3">[</span><span class="ss">convert_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2280588188-3">]</span><span class="p" data-group-id="2280588188-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +was written as:</p><pre><code class="makeup erlang" translate="no"><span class="nf">convert_length</span><span class="p" data-group-id="7226239968-1">(</span><span class="p" data-group-id="7226239968-2">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="7226239968-2">}</span><span class="p" data-group-id="7226239968-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7226239968-3">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="7226239968-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">convert_length</span><span class="p" data-group-id="7226239968-4">(</span><span class="p" data-group-id="7226239968-5">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7226239968-5">}</span><span class="p" data-group-id="7226239968-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7226239968-6">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="7226239968-6">}</span><span class="p">.</span></code></pre><p>The same program can also be written as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4926529548-1">(</span><span class="ss">tut10</span><span class="p" data-group-id="4926529548-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4926529548-2">(</span><span class="p" data-group-id="4926529548-3">[</span><span class="ss">convert_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4926529548-3">]</span><span class="p" data-group-id="4926529548-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">convert_length</span><span class="p" data-group-id="2280588188-4">(</span><span class="n">Length</span><span class="p" data-group-id="2280588188-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">convert_length</span><span class="p" data-group-id="4926529548-4">(</span><span class="n">Length</span><span class="p" data-group-id="4926529548-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="2280588188-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="2280588188-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="2280588188-6">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="2280588188-6">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="2280588188-7">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2280588188-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="2280588188-8">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="2280588188-8">}</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">67&gt; </span><span class="nf">c</span><span class="p" data-group-id="8370864176-1">(</span><span class="ss">tut10</span><span class="p" data-group-id="8370864176-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8370864176-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut10</span><span class="p" data-group-id="8370864176-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">68&gt; </span><span class="nc">tut10</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="8370864176-3">(</span><span class="p" data-group-id="8370864176-4">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p" data-group-id="8370864176-4">}</span><span class="p" data-group-id="8370864176-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8370864176-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="mf">15.24</span><span class="p" data-group-id="8370864176-5">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">69&gt; </span><span class="nc">tut10</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="8370864176-6">(</span><span class="p" data-group-id="8370864176-7">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="mf">2.5</span><span class="p" data-group-id="8370864176-7">}</span><span class="p" data-group-id="8370864176-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8370864176-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="mf">0.984251968503937</span><span class="p" data-group-id="8370864176-8">}</span></code></pre><p>Both <code class="inline">case</code> and <code class="inline">if</code> have <em>return values</em>, that is, in the above example <code class="inline">case</code>
│ │ │ │ +        </span><span class="p" data-group-id="4926529548-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4926529548-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="4926529548-6">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="4926529548-6">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="4926529548-7">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4926529548-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="4926529548-8">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="4926529548-8">}</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">67&gt; </span><span class="nf">c</span><span class="p" data-group-id="7588139447-1">(</span><span class="ss">tut10</span><span class="p" data-group-id="7588139447-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7588139447-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut10</span><span class="p" data-group-id="7588139447-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">68&gt; </span><span class="nc">tut10</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="7588139447-3">(</span><span class="p" data-group-id="7588139447-4">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p" data-group-id="7588139447-4">}</span><span class="p" data-group-id="7588139447-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7588139447-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="mf">15.24</span><span class="p" data-group-id="7588139447-5">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">69&gt; </span><span class="nc">tut10</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="7588139447-6">(</span><span class="p" data-group-id="7588139447-7">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="mf">2.5</span><span class="p" data-group-id="7588139447-7">}</span><span class="p" data-group-id="7588139447-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7588139447-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="mf">0.984251968503937</span><span class="p" data-group-id="7588139447-8">}</span></code></pre><p>Both <code class="inline">case</code> and <code class="inline">if</code> have <em>return values</em>, that is, in the above example <code class="inline">case</code>
│ │ │ │  returned either <code class="inline">{inch,X/2.54}</code> or <code class="inline">{centimeter,Y*2.54}</code>. The behaviour of
│ │ │ │  <code class="inline">case</code> can also be modified by using guards. The following example clarifies
│ │ │ │  this. It tells us the length of a month, given the year. The year must be known,
│ │ │ │ -since February has 29 days in a leap year.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4768232774-1">(</span><span class="ss">tut11</span><span class="p" data-group-id="4768232774-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4768232774-2">(</span><span class="p" data-group-id="4768232774-3">[</span><span class="ss">month_length</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4768232774-3">]</span><span class="p" data-group-id="4768232774-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +since February has 29 days in a leap year.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4947565352-1">(</span><span class="ss">tut11</span><span class="p" data-group-id="4947565352-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4947565352-2">(</span><span class="p" data-group-id="4947565352-3">[</span><span class="ss">month_length</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4947565352-3">]</span><span class="p" data-group-id="4947565352-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">month_length</span><span class="p" data-group-id="4768232774-4">(</span><span class="n">Year</span><span class="p">,</span><span class="w"> </span><span class="n">Month</span><span class="p" data-group-id="4768232774-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">month_length</span><span class="p" data-group-id="4947565352-4">(</span><span class="n">Year</span><span class="p">,</span><span class="w"> </span><span class="n">Month</span><span class="p" data-group-id="4947565352-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% All years divisible by 400 are leap</span><span class="w">
│ │ │ │      </span><span class="c1">%% Years divisible by 100 are not leap (except the 400 rule above)</span><span class="w">
│ │ │ │      </span><span class="c1">%% Years divisible by 4 are leap (except the 100 rule above)</span><span class="w">
│ │ │ │      </span><span class="n">Leap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">if</span><span class="w">
│ │ │ │ -        </span><span class="nf">trunc</span><span class="p" data-group-id="4768232774-5">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="p" data-group-id="4768232774-5">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nf">trunc</span><span class="p" data-group-id="4947565352-5">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="p" data-group-id="4947565352-5">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">leap</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="nf">trunc</span><span class="p" data-group-id="4768232774-6">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">100</span><span class="p" data-group-id="4768232774-6">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">100</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nf">trunc</span><span class="p" data-group-id="4947565352-6">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">100</span><span class="p" data-group-id="4947565352-6">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">100</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">not_leap</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="nf">trunc</span><span class="p" data-group-id="4768232774-7">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="4768232774-7">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">4</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nf">trunc</span><span class="p" data-group-id="4947565352-7">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="4947565352-7">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">4</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">leap</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">not_leap</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Month</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">sep</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">30</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">apr</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">30</span><span class="p">;</span><span class="w">
│ │ │ │ @@ -770,151 +770,151 @@
│ │ │ │          </span><span class="ss">jan</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">mar</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">may</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">jul</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">aug</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">oct</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">dec</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">70&gt; </span><span class="nf">c</span><span class="p" data-group-id="3752879904-1">(</span><span class="ss">tut11</span><span class="p" data-group-id="3752879904-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3752879904-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut11</span><span class="p" data-group-id="3752879904-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">71&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="3752879904-3">(</span><span class="mi">2004</span><span class="p">,</span><span class="w"> </span><span class="ss">feb</span><span class="p" data-group-id="3752879904-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">70&gt; </span><span class="nf">c</span><span class="p" data-group-id="3244589754-1">(</span><span class="ss">tut11</span><span class="p" data-group-id="3244589754-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3244589754-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut11</span><span class="p" data-group-id="3244589754-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">71&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="3244589754-3">(</span><span class="mi">2004</span><span class="p">,</span><span class="w"> </span><span class="ss">feb</span><span class="p" data-group-id="3244589754-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">29</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">72&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="3752879904-4">(</span><span class="mi">2003</span><span class="p">,</span><span class="w"> </span><span class="ss">feb</span><span class="p" data-group-id="3752879904-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">72&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="3244589754-4">(</span><span class="mi">2003</span><span class="p">,</span><span class="w"> </span><span class="ss">feb</span><span class="p" data-group-id="3244589754-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">28</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">73&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="3752879904-5">(</span><span class="mi">1947</span><span class="p">,</span><span class="w"> </span><span class="ss">aug</span><span class="p" data-group-id="3752879904-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">73&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="3244589754-5">(</span><span class="mi">1947</span><span class="p">,</span><span class="w"> </span><span class="ss">aug</span><span class="p" data-group-id="3244589754-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">31</span></code></pre><h2 id="built-in-functions-bifs" class="section-heading">
│ │ │ │    <a href="#built-in-functions-bifs" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Built-In Functions (BIFs)</span>
│ │ │ │  </h2>
│ │ │ │  <p>BIFs are functions that for some reason are built-in to the Erlang virtual
│ │ │ │  machine. BIFs often implement functionality that is impossible or is too
│ │ │ │  inefficient to implement in Erlang. Some BIFs can be called using the function
│ │ │ │  name only, but by default they belong to the <code class="inline">erlang</code> module. For example,
│ │ │ │  the call to the BIF <code class="inline">trunc</code> below is equivalent to a call to <code class="inline">erlang:trunc</code>.</p><p>As shown, first it is checked if a year is leap. If a year is divisible by 400,
│ │ │ │  it is a leap year. To determine this, first divide the year by 400 and use the
│ │ │ │  BIF <code class="inline">trunc</code> (more about this later) to cut off any decimals. Then multiply by
│ │ │ │  400 again and see if the same value is returned again. For example, year 2004:</p><pre><code class="makeup erlang" translate="no"><span class="mi">2004</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">5.01</span><span class="w">
│ │ │ │ -</span><span class="nf">trunc</span><span class="p" data-group-id="3336135490-1">(</span><span class="mf">5.01</span><span class="p" data-group-id="3336135490-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │ │ +</span><span class="nf">trunc</span><span class="p" data-group-id="9202055524-1">(</span><span class="mf">5.01</span><span class="p" data-group-id="9202055524-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │ │  </span><span class="mi">5</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2000</span></code></pre><p>2000 is not the same as 2004, so 2004 is not divisible by 400. Year 2000:</p><pre><code class="makeup erlang" translate="no"><span class="mi">2000</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">5.0</span><span class="w">
│ │ │ │ -</span><span class="nf">trunc</span><span class="p" data-group-id="6032527643-1">(</span><span class="mf">5.0</span><span class="p" data-group-id="6032527643-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │ │ +</span><span class="nf">trunc</span><span class="p" data-group-id="0737736395-1">(</span><span class="mf">5.0</span><span class="p" data-group-id="0737736395-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │ │  </span><span class="mi">5</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2000</span></code></pre><p>That is, a leap year. The next two <code class="inline">trunc</code>-tests evaluate if the year is
│ │ │ │  divisible by 100 or 4 in the same way. The first <code class="inline">if</code> returns <code class="inline">leap</code> or
│ │ │ │  <code class="inline">not_leap</code>, which ends up in the variable <code class="inline">Leap</code>. This variable is used in the
│ │ │ │  guard for <code class="inline">feb</code> in the following <code class="inline">case</code> that tells us how long the month is.</p><p>This example showed the use of <code class="inline">trunc</code>. It is easier to use the Erlang operator
│ │ │ │  <code class="inline">rem</code> that gives the remainder after division, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">74&gt; </span><span class="mi">2004</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">400</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="mi">4</span></code></pre><p>So instead of writing:</p><pre><code class="makeup erlang" translate="no"><span class="nf">trunc</span><span class="p" data-group-id="5487586989-1">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="p" data-group-id="5487586989-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="mi">4</span></code></pre><p>So instead of writing:</p><pre><code class="makeup erlang" translate="no"><span class="nf">trunc</span><span class="p" data-group-id="9557020192-1">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="p" data-group-id="9557020192-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">leap</span><span class="p">;</span></code></pre><p>it can be written:</p><pre><code class="makeup erlang" translate="no"><span class="n">Year</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">leap</span><span class="p">;</span></code></pre><p>There are many other BIFs such as <code class="inline">trunc</code>. Only a few BIFs can be used in
│ │ │ │  guards, and you cannot use functions you have defined yourself in guards. (see
│ │ │ │  <a href="../../../lib/../system/doc/html/expressions.xhtml">Guard Sequences</a>) (For advanced readers: This is to
│ │ │ │  ensure that guards do not have side effects.) Let us play with a few of these
│ │ │ │ -functions in the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">75&gt; </span><span class="nf">trunc</span><span class="p" data-group-id="8470753644-1">(</span><span class="mf">5.6</span><span class="p" data-group-id="8470753644-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +functions in the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">75&gt; </span><span class="nf">trunc</span><span class="p" data-group-id="8408430067-1">(</span><span class="mf">5.6</span><span class="p" data-group-id="8408430067-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">5</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">76&gt; </span><span class="nf">round</span><span class="p" data-group-id="8470753644-2">(</span><span class="mf">5.6</span><span class="p" data-group-id="8470753644-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">76&gt; </span><span class="nf">round</span><span class="p" data-group-id="8408430067-2">(</span><span class="mf">5.6</span><span class="p" data-group-id="8408430067-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">6</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">77&gt; </span><span class="nf">length</span><span class="p" data-group-id="8470753644-3">(</span><span class="p" data-group-id="8470753644-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="8470753644-4">]</span><span class="p" data-group-id="8470753644-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">77&gt; </span><span class="nf">length</span><span class="p" data-group-id="8408430067-3">(</span><span class="p" data-group-id="8408430067-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="8408430067-4">]</span><span class="p" data-group-id="8408430067-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">78&gt; </span><span class="nf">float</span><span class="p" data-group-id="8470753644-5">(</span><span class="mi">5</span><span class="p" data-group-id="8470753644-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">78&gt; </span><span class="nf">float</span><span class="p" data-group-id="8408430067-5">(</span><span class="mi">5</span><span class="p" data-group-id="8408430067-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mf">5.0</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">79&gt; </span><span class="nf">is_atom</span><span class="p" data-group-id="8470753644-6">(</span><span class="ss">hello</span><span class="p" data-group-id="8470753644-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">79&gt; </span><span class="nf">is_atom</span><span class="p" data-group-id="8408430067-6">(</span><span class="ss">hello</span><span class="p" data-group-id="8408430067-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">80&gt; </span><span class="nf">is_atom</span><span class="p" data-group-id="8470753644-7">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="8470753644-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">80&gt; </span><span class="nf">is_atom</span><span class="p" data-group-id="8408430067-7">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="8408430067-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">81&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="8470753644-8">(</span><span class="p" data-group-id="8470753644-9">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8470753644-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p" data-group-id="8470753644-10">}</span><span class="p" data-group-id="8470753644-9">}</span><span class="p" data-group-id="8470753644-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">81&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="8408430067-8">(</span><span class="p" data-group-id="8408430067-9">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8408430067-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p" data-group-id="8408430067-10">}</span><span class="p" data-group-id="8408430067-9">}</span><span class="p" data-group-id="8408430067-8">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">82&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="8470753644-11">(</span><span class="p" data-group-id="8470753644-12">[</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8470753644-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p" data-group-id="8470753644-13">}</span><span class="p" data-group-id="8470753644-12">]</span><span class="p" data-group-id="8470753644-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">82&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="8408430067-11">(</span><span class="p" data-group-id="8408430067-12">[</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8408430067-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p" data-group-id="8408430067-13">}</span><span class="p" data-group-id="8408430067-12">]</span><span class="p" data-group-id="8408430067-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span></code></pre><p>All of these can be used in guards. Now for some BIFs that cannot be used in
│ │ │ │ -guards:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">83&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="3643715369-1">(</span><span class="ss">hello</span><span class="p" data-group-id="3643715369-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +guards:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">83&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="7031598379-1">(</span><span class="ss">hello</span><span class="p" data-group-id="7031598379-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;hello&quot;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">84&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="3643715369-2">(</span><span class="s">&quot;goodbye&quot;</span><span class="p" data-group-id="3643715369-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">84&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="7031598379-2">(</span><span class="s">&quot;goodbye&quot;</span><span class="p" data-group-id="7031598379-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">goodbye</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">85&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="3643715369-3">(</span><span class="mi">22</span><span class="p" data-group-id="3643715369-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">85&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="7031598379-3">(</span><span class="mi">22</span><span class="p" data-group-id="7031598379-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;22&quot;</span></code></pre><p>These three BIFs do conversions that would be difficult (or impossible) to do in
│ │ │ │  Erlang.</p><h2 id="higher-order-functions-funs" class="section-heading">
│ │ │ │    <a href="#higher-order-functions-funs" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Higher-Order Functions (Funs)</span>
│ │ │ │  </h2>
│ │ │ │  <p>Erlang, like most modern functional programming languages, has higher-order
│ │ │ │ -functions. Here is an example using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">86&gt; </span><span class="n">Xf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="2131934745-1">(</span><span class="n">X</span><span class="p" data-group-id="2131934745-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +functions. Here is an example using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">86&gt; </span><span class="n">Xf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="4122024165-1">(</span><span class="n">X</span><span class="p" data-group-id="4122024165-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">5.123085357</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">87&gt; </span><span class="n">Xf</span><span class="p" data-group-id="2131934745-2">(</span><span class="mi">5</span><span class="p" data-group-id="2131934745-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">87&gt; </span><span class="n">Xf</span><span class="p" data-group-id="4122024165-2">(</span><span class="mi">5</span><span class="p" data-group-id="4122024165-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">10</span></code></pre><p>Here a function that doubles the value of a number is defined and assigned to
│ │ │ │  a variable. Thus <code class="inline">Xf(5)</code> returns value 10.</p><p>Two useful functions when working with lists are <code class="inline">foreach</code> and <code class="inline">map</code>, which
│ │ │ │ -are defined as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="5841781065-1">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5841781065-2">[</span><span class="n">First</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="5841781065-2">]</span><span class="p" data-group-id="5841781065-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Fun</span><span class="p" data-group-id="5841781065-3">(</span><span class="n">First</span><span class="p" data-group-id="5841781065-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="5841781065-4">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5841781065-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">foreach</span><span class="p" data-group-id="5841781065-5">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5841781065-6">[</span><span class="p" data-group-id="5841781065-6">]</span><span class="p" data-group-id="5841781065-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +are defined as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="2020038472-1">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2020038472-2">[</span><span class="n">First</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="2020038472-2">]</span><span class="p" data-group-id="2020038472-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Fun</span><span class="p" data-group-id="2020038472-3">(</span><span class="n">First</span><span class="p" data-group-id="2020038472-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="2020038472-4">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="2020038472-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">foreach</span><span class="p" data-group-id="2020038472-5">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2020038472-6">[</span><span class="p" data-group-id="2020038472-6">]</span><span class="p" data-group-id="2020038472-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="5841781065-7">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5841781065-8">[</span><span class="n">First</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="5841781065-8">]</span><span class="p" data-group-id="5841781065-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5841781065-9">[</span><span class="n">Fun</span><span class="p" data-group-id="5841781065-10">(</span><span class="n">First</span><span class="p" data-group-id="5841781065-10">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="5841781065-11">(</span><span class="n">Fun</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="5841781065-11">)</span><span class="p" data-group-id="5841781065-9">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="5841781065-12">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5841781065-13">[</span><span class="p" data-group-id="5841781065-13">]</span><span class="p" data-group-id="5841781065-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5841781065-14">[</span><span class="p" data-group-id="5841781065-14">]</span><span class="p">.</span></code></pre><p>These two functions are provided in the standard library module <code class="inline">lists</code>. <code class="inline">foreach</code> takes
│ │ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="2020038472-7">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2020038472-8">[</span><span class="n">First</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="2020038472-8">]</span><span class="p" data-group-id="2020038472-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2020038472-9">[</span><span class="n">Fun</span><span class="p" data-group-id="2020038472-10">(</span><span class="n">First</span><span class="p" data-group-id="2020038472-10">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="2020038472-11">(</span><span class="n">Fun</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="2020038472-11">)</span><span class="p" data-group-id="2020038472-9">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="2020038472-12">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2020038472-13">[</span><span class="p" data-group-id="2020038472-13">]</span><span class="p" data-group-id="2020038472-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2020038472-14">[</span><span class="p" data-group-id="2020038472-14">]</span><span class="p">.</span></code></pre><p>These two functions are provided in the standard library module <code class="inline">lists</code>. <code class="inline">foreach</code> takes
│ │ │ │  a list and applies a fun to every element in the list. <code class="inline">map</code> creates a new list
│ │ │ │  by applying a fun to every element in a list. Going back to the shell, <code class="inline">map</code> is
│ │ │ │ -used with a fun to add 3 to every element of a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">88&gt; </span><span class="n">Add_3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="1546657389-1">(</span><span class="n">X</span><span class="p" data-group-id="1546657389-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +used with a fun to add 3 to every element of a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">88&gt; </span><span class="n">Add_3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="2286716816-1">(</span><span class="n">X</span><span class="p" data-group-id="2286716816-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">5.123085357</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">89&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="1546657389-2">(</span><span class="n">Add_3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1546657389-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1546657389-3">]</span><span class="p" data-group-id="1546657389-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1546657389-4">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="1546657389-4">]</span></code></pre><p>Let us (again) print the temperatures in a list of cities:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">90&gt; </span><span class="n">Print_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="1440262149-1">(</span><span class="p" data-group-id="1440262149-2">{</span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1440262149-3">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="1440262149-3">}</span><span class="p" data-group-id="1440262149-2">}</span><span class="p" data-group-id="1440262149-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1440262149-4">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1440262149-5">[</span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="1440262149-5">]</span><span class="p" data-group-id="1440262149-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">89&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="2286716816-2">(</span><span class="n">Add_3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2286716816-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2286716816-3">]</span><span class="p" data-group-id="2286716816-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2286716816-4">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2286716816-4">]</span></code></pre><p>Let us (again) print the temperatures in a list of cities:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">90&gt; </span><span class="n">Print_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0796540614-1">(</span><span class="p" data-group-id="0796540614-2">{</span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0796540614-3">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0796540614-3">}</span><span class="p" data-group-id="0796540614-2">}</span><span class="p" data-group-id="0796540614-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0796540614-4">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0796540614-5">[</span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0796540614-5">]</span><span class="p" data-group-id="0796540614-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">5.123085357</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">91&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="1440262149-6">(</span><span class="n">Print_City</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1440262149-7">[</span><span class="p" data-group-id="1440262149-8">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1440262149-9">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="1440262149-9">}</span><span class="p" data-group-id="1440262149-8">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1440262149-10">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1440262149-11">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="1440262149-11">}</span><span class="p" data-group-id="1440262149-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1440262149-12">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1440262149-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="1440262149-13">}</span><span class="p" data-group-id="1440262149-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1440262149-14">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1440262149-15">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="1440262149-15">}</span><span class="p" data-group-id="1440262149-14">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1440262149-16">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1440262149-17">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="1440262149-17">}</span><span class="p" data-group-id="1440262149-16">}</span><span class="p" data-group-id="1440262149-7">]</span><span class="p" data-group-id="1440262149-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">91&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="0796540614-6">(</span><span class="n">Print_City</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0796540614-7">[</span><span class="p" data-group-id="0796540614-8">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0796540614-9">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="0796540614-9">}</span><span class="p" data-group-id="0796540614-8">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0796540614-10">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0796540614-11">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="0796540614-11">}</span><span class="p" data-group-id="0796540614-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0796540614-12">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0796540614-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="0796540614-13">}</span><span class="p" data-group-id="0796540614-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0796540614-14">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0796540614-15">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="0796540614-15">}</span><span class="p" data-group-id="0796540614-14">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0796540614-16">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0796540614-17">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="0796540614-17">}</span><span class="p" data-group-id="0796540614-16">}</span><span class="p" data-group-id="0796540614-7">]</span><span class="p" data-group-id="0796540614-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">moscow</span><span class="w">          </span><span class="ss">c</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="w">
│ │ │ │  </span><span class="ss">cape_town</span><span class="w">       </span><span class="ss">f</span><span class="w"> </span><span class="mi">70</span><span class="w">
│ │ │ │  </span><span class="ss">stockholm</span><span class="w">       </span><span class="ss">c</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="w">
│ │ │ │  </span><span class="ss">paris</span><span class="w">           </span><span class="ss">f</span><span class="w"> </span><span class="mi">28</span><span class="w">
│ │ │ │  </span><span class="ss">london</span><span class="w">          </span><span class="ss">f</span><span class="w"> </span><span class="mi">36</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>Let us now define a fun that can be used to go through a list of cities and
│ │ │ │ -temperatures and transform them all to Celsius.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3519826101-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="3519826101-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +temperatures and transform them all to Celsius.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8629267071-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="8629267071-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3519826101-2">(</span><span class="p" data-group-id="3519826101-3">[</span><span class="ss">convert_list_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3519826101-3">]</span><span class="p" data-group-id="3519826101-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8629267071-2">(</span><span class="p" data-group-id="8629267071-3">[</span><span class="ss">convert_list_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8629267071-3">]</span><span class="p" data-group-id="8629267071-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">convert_to_c</span><span class="p" data-group-id="3519826101-4">(</span><span class="p" data-group-id="3519826101-5">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3519826101-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="3519826101-6">}</span><span class="p" data-group-id="3519826101-5">}</span><span class="p" data-group-id="3519826101-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3519826101-7">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3519826101-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="nf">trunc</span><span class="p" data-group-id="3519826101-9">(</span><span class="p" data-group-id="3519826101-10">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="3519826101-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="3519826101-9">)</span><span class="p" data-group-id="3519826101-8">}</span><span class="p" data-group-id="3519826101-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">convert_to_c</span><span class="p" data-group-id="3519826101-11">(</span><span class="p" data-group-id="3519826101-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3519826101-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="3519826101-13">}</span><span class="p" data-group-id="3519826101-12">}</span><span class="p" data-group-id="3519826101-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3519826101-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3519826101-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="3519826101-15">}</span><span class="p" data-group-id="3519826101-14">}</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3519826101-16">(</span><span class="n">List</span><span class="p" data-group-id="3519826101-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="3519826101-17">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="3519826101-17">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">92&gt; </span><span class="nc">tut13</span><span class="p">:</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="9083107480-1">(</span><span class="p" data-group-id="9083107480-2">[</span><span class="p" data-group-id="9083107480-3">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9083107480-4">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="9083107480-4">}</span><span class="p" data-group-id="9083107480-3">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9083107480-5">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9083107480-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="9083107480-6">}</span><span class="p" data-group-id="9083107480-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9083107480-7">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9083107480-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="9083107480-8">}</span><span class="p" data-group-id="9083107480-7">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9083107480-9">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9083107480-10">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="9083107480-10">}</span><span class="p" data-group-id="9083107480-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9083107480-11">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9083107480-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="9083107480-12">}</span><span class="p" data-group-id="9083107480-11">}</span><span class="p" data-group-id="9083107480-2">]</span><span class="p" data-group-id="9083107480-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9083107480-13">[</span><span class="p" data-group-id="9083107480-14">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="9083107480-15">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="9083107480-15">}</span><span class="p" data-group-id="9083107480-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9083107480-16">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="9083107480-17">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">21</span><span class="p" data-group-id="9083107480-17">}</span><span class="p" data-group-id="9083107480-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9083107480-18">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="9083107480-19">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="9083107480-19">}</span><span class="p" data-group-id="9083107480-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9083107480-20">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="9083107480-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="9083107480-21">}</span><span class="p" data-group-id="9083107480-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9083107480-22">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="9083107480-23">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9083107480-23">}</span><span class="p" data-group-id="9083107480-22">}</span><span class="p" data-group-id="9083107480-13">]</span></code></pre><p>The <code class="inline">convert_to_c</code> function is the same as before, but here it is used as a fun:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="3079480472-1">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="3079480472-1">)</span></code></pre><p>When a function defined elsewhere is used as a fun, it can be referred to as
│ │ │ │ +</span><span class="nf">convert_to_c</span><span class="p" data-group-id="8629267071-4">(</span><span class="p" data-group-id="8629267071-5">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8629267071-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8629267071-6">}</span><span class="p" data-group-id="8629267071-5">}</span><span class="p" data-group-id="8629267071-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8629267071-7">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8629267071-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="nf">trunc</span><span class="p" data-group-id="8629267071-9">(</span><span class="p" data-group-id="8629267071-10">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="8629267071-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="8629267071-9">)</span><span class="p" data-group-id="8629267071-8">}</span><span class="p" data-group-id="8629267071-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">convert_to_c</span><span class="p" data-group-id="8629267071-11">(</span><span class="p" data-group-id="8629267071-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8629267071-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8629267071-13">}</span><span class="p" data-group-id="8629267071-12">}</span><span class="p" data-group-id="8629267071-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8629267071-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8629267071-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8629267071-15">}</span><span class="p" data-group-id="8629267071-14">}</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="8629267071-16">(</span><span class="n">List</span><span class="p" data-group-id="8629267071-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="8629267071-17">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="8629267071-17">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">92&gt; </span><span class="nc">tut13</span><span class="p">:</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="6191859133-1">(</span><span class="p" data-group-id="6191859133-2">[</span><span class="p" data-group-id="6191859133-3">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6191859133-4">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="6191859133-4">}</span><span class="p" data-group-id="6191859133-3">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6191859133-5">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6191859133-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="6191859133-6">}</span><span class="p" data-group-id="6191859133-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6191859133-7">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6191859133-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="6191859133-8">}</span><span class="p" data-group-id="6191859133-7">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6191859133-9">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6191859133-10">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="6191859133-10">}</span><span class="p" data-group-id="6191859133-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6191859133-11">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6191859133-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="6191859133-12">}</span><span class="p" data-group-id="6191859133-11">}</span><span class="p" data-group-id="6191859133-2">]</span><span class="p" data-group-id="6191859133-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6191859133-13">[</span><span class="p" data-group-id="6191859133-14">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="6191859133-15">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="6191859133-15">}</span><span class="p" data-group-id="6191859133-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6191859133-16">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="6191859133-17">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">21</span><span class="p" data-group-id="6191859133-17">}</span><span class="p" data-group-id="6191859133-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6191859133-18">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="6191859133-19">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="6191859133-19">}</span><span class="p" data-group-id="6191859133-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6191859133-20">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="6191859133-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="6191859133-21">}</span><span class="p" data-group-id="6191859133-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6191859133-22">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="6191859133-23">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6191859133-23">}</span><span class="p" data-group-id="6191859133-22">}</span><span class="p" data-group-id="6191859133-13">]</span></code></pre><p>The <code class="inline">convert_to_c</code> function is the same as before, but here it is used as a fun:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="4126840360-1">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="4126840360-1">)</span></code></pre><p>When a function defined elsewhere is used as a fun, it can be referred to as
│ │ │ │  <code class="inline">fun Function/Arity</code> (remember that <code class="inline">Arity</code> = number of arguments). That is
│ │ │ │  why <code class="inline">fun convert_to_c/1</code> can be used in the call above. As shown,
│ │ │ │  <code class="inline">convert_list_to_c</code> becomes much shorter and easier to understand.</p><p>The standard module <code class="inline">lists</code> also contains a function <code class="inline">sort(Fun, List)</code> where
│ │ │ │  <code class="inline">Fun</code> is a fun with two arguments. This fun returns <code class="inline">true</code> if the first argument
│ │ │ │  is less than the second argument, or else <code class="inline">false</code>. Sorting is added to the
│ │ │ │ -<code class="inline">convert_list_to_c</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7842131011-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="7842131011-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">convert_list_to_c</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8135123854-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="8135123854-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7842131011-2">(</span><span class="p" data-group-id="7842131011-3">[</span><span class="ss">convert_list_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7842131011-3">]</span><span class="p" data-group-id="7842131011-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8135123854-2">(</span><span class="p" data-group-id="8135123854-3">[</span><span class="ss">convert_list_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8135123854-3">]</span><span class="p" data-group-id="8135123854-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">convert_to_c</span><span class="p" data-group-id="7842131011-4">(</span><span class="p" data-group-id="7842131011-5">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7842131011-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7842131011-6">}</span><span class="p" data-group-id="7842131011-5">}</span><span class="p" data-group-id="7842131011-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7842131011-7">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7842131011-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="nf">trunc</span><span class="p" data-group-id="7842131011-9">(</span><span class="p" data-group-id="7842131011-10">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="7842131011-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="7842131011-9">)</span><span class="p" data-group-id="7842131011-8">}</span><span class="p" data-group-id="7842131011-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">convert_to_c</span><span class="p" data-group-id="7842131011-11">(</span><span class="p" data-group-id="7842131011-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7842131011-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7842131011-13">}</span><span class="p" data-group-id="7842131011-12">}</span><span class="p" data-group-id="7842131011-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7842131011-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7842131011-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7842131011-15">}</span><span class="p" data-group-id="7842131011-14">}</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7842131011-16">(</span><span class="n">List</span><span class="p" data-group-id="7842131011-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">New_list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="7842131011-17">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7842131011-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">sort</span><span class="p" data-group-id="7842131011-18">(</span><span class="nf">fun</span><span class="p" data-group-id="7842131011-19">(</span><span class="p" data-group-id="7842131011-20">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7842131011-21">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp1</span><span class="p" data-group-id="7842131011-21">}</span><span class="p" data-group-id="7842131011-20">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7842131011-22">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7842131011-23">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp2</span><span class="p" data-group-id="7842131011-23">}</span><span class="p" data-group-id="7842131011-22">}</span><span class="p" data-group-id="7842131011-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                       </span><span class="n">Temp1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Temp2</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">New_list</span><span class="p" data-group-id="7842131011-18">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">93&gt; </span><span class="nf">c</span><span class="p" data-group-id="9714723903-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="9714723903-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9714723903-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut13</span><span class="p" data-group-id="9714723903-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">94&gt; </span><span class="nc">tut13</span><span class="p">:</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="9714723903-3">(</span><span class="p" data-group-id="9714723903-4">[</span><span class="p" data-group-id="9714723903-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9714723903-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="9714723903-6">}</span><span class="p" data-group-id="9714723903-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9714723903-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9714723903-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="9714723903-8">}</span><span class="p" data-group-id="9714723903-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9714723903-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9714723903-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="9714723903-10">}</span><span class="p" data-group-id="9714723903-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9714723903-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9714723903-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="9714723903-12">}</span><span class="p" data-group-id="9714723903-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9714723903-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9714723903-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="9714723903-14">}</span><span class="p" data-group-id="9714723903-13">}</span><span class="p" data-group-id="9714723903-4">]</span><span class="p" data-group-id="9714723903-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9714723903-15">[</span><span class="p" data-group-id="9714723903-16">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="9714723903-17">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="9714723903-17">}</span><span class="p" data-group-id="9714723903-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9714723903-18">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="9714723903-19">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="9714723903-19">}</span><span class="p" data-group-id="9714723903-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9714723903-20">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="9714723903-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="9714723903-21">}</span><span class="p" data-group-id="9714723903-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9714723903-22">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="9714723903-23">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9714723903-23">}</span><span class="p" data-group-id="9714723903-22">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9714723903-24">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="9714723903-25">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">21</span><span class="p" data-group-id="9714723903-25">}</span><span class="p" data-group-id="9714723903-24">}</span><span class="p" data-group-id="9714723903-15">]</span></code></pre><p>In <code class="inline">sort</code> the fun is used:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="p" data-group-id="0214296930-1">(</span><span class="p" data-group-id="0214296930-2">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0214296930-3">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp1</span><span class="p" data-group-id="0214296930-3">}</span><span class="p" data-group-id="0214296930-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0214296930-4">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0214296930-5">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp2</span><span class="p" data-group-id="0214296930-5">}</span><span class="p" data-group-id="0214296930-4">}</span><span class="p" data-group-id="0214296930-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Temp1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Temp2</span><span class="w"> </span><span class="k">end</span><span class="p">,</span></code></pre><p>Here the concept of an <em>anonymous variable</em> <code class="inline">_</code> is introduced. This is simply
│ │ │ │ +</span><span class="nf">convert_to_c</span><span class="p" data-group-id="8135123854-4">(</span><span class="p" data-group-id="8135123854-5">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8135123854-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8135123854-6">}</span><span class="p" data-group-id="8135123854-5">}</span><span class="p" data-group-id="8135123854-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8135123854-7">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8135123854-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="nf">trunc</span><span class="p" data-group-id="8135123854-9">(</span><span class="p" data-group-id="8135123854-10">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="8135123854-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="8135123854-9">)</span><span class="p" data-group-id="8135123854-8">}</span><span class="p" data-group-id="8135123854-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">convert_to_c</span><span class="p" data-group-id="8135123854-11">(</span><span class="p" data-group-id="8135123854-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8135123854-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8135123854-13">}</span><span class="p" data-group-id="8135123854-12">}</span><span class="p" data-group-id="8135123854-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8135123854-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8135123854-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8135123854-15">}</span><span class="p" data-group-id="8135123854-14">}</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="8135123854-16">(</span><span class="n">List</span><span class="p" data-group-id="8135123854-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">New_list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="8135123854-17">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="8135123854-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">sort</span><span class="p" data-group-id="8135123854-18">(</span><span class="nf">fun</span><span class="p" data-group-id="8135123854-19">(</span><span class="p" data-group-id="8135123854-20">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8135123854-21">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp1</span><span class="p" data-group-id="8135123854-21">}</span><span class="p" data-group-id="8135123854-20">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8135123854-22">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8135123854-23">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp2</span><span class="p" data-group-id="8135123854-23">}</span><span class="p" data-group-id="8135123854-22">}</span><span class="p" data-group-id="8135123854-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                       </span><span class="n">Temp1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Temp2</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">New_list</span><span class="p" data-group-id="8135123854-18">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">93&gt; </span><span class="nf">c</span><span class="p" data-group-id="9847182257-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="9847182257-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9847182257-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut13</span><span class="p" data-group-id="9847182257-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">94&gt; </span><span class="nc">tut13</span><span class="p">:</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="9847182257-3">(</span><span class="p" data-group-id="9847182257-4">[</span><span class="p" data-group-id="9847182257-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9847182257-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="9847182257-6">}</span><span class="p" data-group-id="9847182257-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9847182257-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9847182257-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="9847182257-8">}</span><span class="p" data-group-id="9847182257-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9847182257-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9847182257-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="9847182257-10">}</span><span class="p" data-group-id="9847182257-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9847182257-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9847182257-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="9847182257-12">}</span><span class="p" data-group-id="9847182257-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9847182257-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9847182257-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="9847182257-14">}</span><span class="p" data-group-id="9847182257-13">}</span><span class="p" data-group-id="9847182257-4">]</span><span class="p" data-group-id="9847182257-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9847182257-15">[</span><span class="p" data-group-id="9847182257-16">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="9847182257-17">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="9847182257-17">}</span><span class="p" data-group-id="9847182257-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9847182257-18">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="9847182257-19">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="9847182257-19">}</span><span class="p" data-group-id="9847182257-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9847182257-20">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="9847182257-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="9847182257-21">}</span><span class="p" data-group-id="9847182257-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9847182257-22">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="9847182257-23">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9847182257-23">}</span><span class="p" data-group-id="9847182257-22">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9847182257-24">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="9847182257-25">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">21</span><span class="p" data-group-id="9847182257-25">}</span><span class="p" data-group-id="9847182257-24">}</span><span class="p" data-group-id="9847182257-15">]</span></code></pre><p>In <code class="inline">sort</code> the fun is used:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="p" data-group-id="9156830739-1">(</span><span class="p" data-group-id="9156830739-2">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9156830739-3">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp1</span><span class="p" data-group-id="9156830739-3">}</span><span class="p" data-group-id="9156830739-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9156830739-4">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9156830739-5">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp2</span><span class="p" data-group-id="9156830739-5">}</span><span class="p" data-group-id="9156830739-4">}</span><span class="p" data-group-id="9156830739-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Temp1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Temp2</span><span class="w"> </span><span class="k">end</span><span class="p">,</span></code></pre><p>Here the concept of an <em>anonymous variable</em> <code class="inline">_</code> is introduced. This is simply
│ │ │ │  shorthand for a variable that gets a value, but the value is ignored. This can
│ │ │ │  be used anywhere suitable, not just in funs. <code class="inline">Temp1 &lt; Temp2</code> returns <code class="inline">true</code> if
│ │ │ │  <code class="inline">Temp1</code> is less than <code class="inline">Temp2</code>.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/secure_coding.xhtml
│ │ │ │ @@ -279,108 +279,108 @@
│ │ │ │  left to the supervision structure, and all unexpected <em>conditions</em> should be
│ │ │ │  considered errors. In brief, this is because encountering something unexpected
│ │ │ │  means that we have left the <em>known and tested</em> path, and continuing greatly
│ │ │ │  increases the risk for bugs and security issues.</p><p>Erlang code should be written as restrictively as possible, to provoke errors
│ │ │ │  whenever anything unexpected happens. The idea is to make the third error
│ │ │ │  category, program bugs, visible as a crash instead of silently continuing.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">High</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/252.html" title="">CWE-252</a>, <a href="https://cwe.mitre.org/data/definitions/253.html" title="">CWE-253</a>, <a href="https://cwe.mitre.org/data/definitions/391.html" title="">CWE-391</a>, <a href="https://cwe.mitre.org/data/definitions/392.html" title="">CWE-392</a>,
│ │ │ │  <a href="https://cwe.mitre.org/data/definitions/394.html" title="">CWE-394</a>, <a href="https://cwe.mitre.org/data/definitions/396.html" title="">CWE-396</a>, <a href="#owasp-a10-2025" title=""><code class="inline">A10:2025</code></a></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="k">case</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="3306842855-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="3306842855-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="k">case</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="1982910920-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="1982910920-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │      </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">C</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">D</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ │ -</span><span class="k">case</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="3306842855-2">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="3306842855-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="k">case</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="1982910920-2">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="1982910920-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │      </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">C</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="c1">%% What if operation/2 is extended to also return &#39;maybe&#39;, or someone</span><span class="w">
│ │ │ │      </span><span class="c1">%% misspells &#39;true&#39; as &#39;tru&#39;?</span><span class="w">
│ │ │ │      </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">D</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">write</span><span class="p" data-group-id="3306842855-3">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3306842855-3">)</span><span class="w">
│ │ │ │ +</span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">write</span><span class="p" data-group-id="1982910920-3">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1982910920-3">)</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ │ -</span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">write</span><span class="p" data-group-id="3306842855-4">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3306842855-4">)</span><span class="w">
│ │ │ │ +</span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">write</span><span class="p" data-group-id="1982910920-4">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1982910920-4">)</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="3306842855-5">(</span><span class="p" data-group-id="3306842855-6">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3306842855-6">]</span><span class="p" data-group-id="3306842855-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3306842855-7">[</span><span class="nf">bar</span><span class="p" data-group-id="3306842855-8">(</span><span class="n">First</span><span class="p" data-group-id="3306842855-8">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="3306842855-9">(</span><span class="n">Rest</span><span class="p" data-group-id="3306842855-9">)</span><span class="p" data-group-id="3306842855-7">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="3306842855-10">(</span><span class="p" data-group-id="3306842855-11">[</span><span class="p" data-group-id="3306842855-11">]</span><span class="p" data-group-id="3306842855-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3306842855-12">[</span><span class="p" data-group-id="3306842855-12">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="1982910920-5">(</span><span class="p" data-group-id="1982910920-6">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1982910920-6">]</span><span class="p" data-group-id="1982910920-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1982910920-7">[</span><span class="nf">bar</span><span class="p" data-group-id="1982910920-8">(</span><span class="n">First</span><span class="p" data-group-id="1982910920-8">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="1982910920-9">(</span><span class="n">Rest</span><span class="p" data-group-id="1982910920-9">)</span><span class="p" data-group-id="1982910920-7">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="1982910920-10">(</span><span class="p" data-group-id="1982910920-11">[</span><span class="p" data-group-id="1982910920-11">]</span><span class="p" data-group-id="1982910920-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1982910920-12">[</span><span class="p" data-group-id="1982910920-12">]</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="3306842855-13">(</span><span class="p" data-group-id="3306842855-14">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3306842855-14">]</span><span class="p" data-group-id="3306842855-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3306842855-15">[</span><span class="nf">bar</span><span class="p" data-group-id="3306842855-16">(</span><span class="n">First</span><span class="p" data-group-id="3306842855-16">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="3306842855-17">(</span><span class="n">Rest</span><span class="p" data-group-id="3306842855-17">)</span><span class="p" data-group-id="3306842855-15">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="3306842855-18">(</span><span class="p">_</span><span class="p" data-group-id="3306842855-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3306842855-19">[</span><span class="p" data-group-id="3306842855-19">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="1982910920-13">(</span><span class="p" data-group-id="1982910920-14">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1982910920-14">]</span><span class="p" data-group-id="1982910920-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1982910920-15">[</span><span class="nf">bar</span><span class="p" data-group-id="1982910920-16">(</span><span class="n">First</span><span class="p" data-group-id="1982910920-16">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="1982910920-17">(</span><span class="n">Rest</span><span class="p" data-group-id="1982910920-17">)</span><span class="p" data-group-id="1982910920-15">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="1982910920-18">(</span><span class="p">_</span><span class="p" data-group-id="1982910920-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1982910920-19">[</span><span class="p" data-group-id="1982910920-19">]</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="3306842855-20">(</span><span class="p" data-group-id="3306842855-21">&lt;&lt;</span><span class="s">&quot;foo&quot;</span><span class="p" data-group-id="3306842855-21">&gt;&gt;</span><span class="p" data-group-id="3306842855-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">foo</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="3306842855-22">(</span><span class="p" data-group-id="3306842855-23">&lt;&lt;</span><span class="s">&quot;bar&quot;</span><span class="p" data-group-id="3306842855-23">&gt;&gt;</span><span class="p" data-group-id="3306842855-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">bar</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="3306842855-24">(</span><span class="p" data-group-id="3306842855-25">&lt;&lt;</span><span class="s">&quot;quux&quot;</span><span class="p" data-group-id="3306842855-25">&gt;&gt;</span><span class="p" data-group-id="3306842855-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">quux</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="1982910920-20">(</span><span class="p" data-group-id="1982910920-21">&lt;&lt;</span><span class="s">&quot;foo&quot;</span><span class="p" data-group-id="1982910920-21">&gt;&gt;</span><span class="p" data-group-id="1982910920-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">foo</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="1982910920-22">(</span><span class="p" data-group-id="1982910920-23">&lt;&lt;</span><span class="s">&quot;bar&quot;</span><span class="p" data-group-id="1982910920-23">&gt;&gt;</span><span class="p" data-group-id="1982910920-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">bar</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="1982910920-24">(</span><span class="p" data-group-id="1982910920-25">&lt;&lt;</span><span class="s">&quot;quux&quot;</span><span class="p" data-group-id="1982910920-25">&gt;&gt;</span><span class="p" data-group-id="1982910920-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">quux</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO NOT, when set of possible atoms is known beforehand</span><span class="w">
│ │ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="3306842855-26">(</span><span class="n">Text</span><span class="p" data-group-id="3306842855-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">binary_to_existing_atom</span><span class="p" data-group-id="3306842855-27">(</span><span class="n">Text</span><span class="p" data-group-id="3306842855-27">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="1982910920-26">(</span><span class="n">Text</span><span class="p" data-group-id="1982910920-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">binary_to_existing_atom</span><span class="p" data-group-id="1982910920-27">(</span><span class="n">Text</span><span class="p" data-group-id="1982910920-27">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="k">try</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="3306842855-28">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="3306842855-28">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3306842855-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="3306842855-29">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">something</span><span class="p" data-group-id="3306842855-30">(</span><span class="n">X</span><span class="p" data-group-id="3306842855-30">)</span><span class="w">
│ │ │ │ +</span><span class="k">try</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="1982910920-28">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="1982910920-28">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1982910920-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1982910920-29">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">something</span><span class="p" data-group-id="1982910920-30">(</span><span class="n">X</span><span class="p" data-group-id="1982910920-30">)</span><span class="w">
│ │ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ │      </span><span class="nc">error</span><span class="p">:</span><span class="ss">specific_error</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">error</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ │ -</span><span class="k">try</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="3306842855-31">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="3306842855-31">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3306842855-32">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="3306842855-32">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">something</span><span class="p" data-group-id="3306842855-33">(</span><span class="n">X</span><span class="p" data-group-id="3306842855-33">)</span><span class="w">
│ │ │ │ +</span><span class="k">try</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="1982910920-31">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="1982910920-31">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1982910920-32">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1982910920-32">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">something</span><span class="p" data-group-id="1982910920-33">(</span><span class="n">X</span><span class="p" data-group-id="1982910920-33">)</span><span class="w">
│ │ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ │      </span><span class="nc">error</span><span class="p">:</span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">error</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% PREFER</span><span class="w">
│ │ │ │ -</span><span class="k">case</span><span class="w"> </span><span class="nf">my_filter</span><span class="p" data-group-id="3306842855-34">(</span><span class="n">List0</span><span class="p">,</span><span class="w"> </span><span class="ss">unchanged</span><span class="p" data-group-id="3306842855-34">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="k">case</span><span class="w"> </span><span class="nf">my_filter</span><span class="p" data-group-id="1982910920-34">(</span><span class="n">List0</span><span class="p">,</span><span class="w"> </span><span class="ss">unchanged</span><span class="p" data-group-id="1982910920-34">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │      </span><span class="ss">unchanged</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List0</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3306842855-35">{</span><span class="ss">changed</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="3306842855-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1982910920-35">{</span><span class="ss">changed</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="1982910920-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% AVOID</span><span class="w">
│ │ │ │ -</span><span class="k">case</span><span class="w"> </span><span class="nf">my_filter</span><span class="p" data-group-id="3306842855-36">(</span><span class="n">List0</span><span class="p">,</span><span class="w"> </span><span class="ss">unchanged</span><span class="p" data-group-id="3306842855-36">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="k">case</span><span class="w"> </span><span class="nf">my_filter</span><span class="p" data-group-id="1982910920-36">(</span><span class="n">List0</span><span class="p">,</span><span class="w"> </span><span class="ss">unchanged</span><span class="p" data-group-id="1982910920-36">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │      </span><span class="ss">unchanged</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List0</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="c1">%% What if a misspelled atom like &#39;uchanged&#39; is returned?</span><span class="w">
│ │ │ │      </span><span class="n">List</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% PREFER</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3306842855-37">[</span><span class="nf">op</span><span class="p" data-group-id="3306842855-38">(</span><span class="n">L</span><span class="p" data-group-id="3306842855-38">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="o">#</span><span class="ss">my_record</span><span class="p" data-group-id="3306842855-39">{</span><span class="p" data-group-id="3306842855-39">}</span><span class="o">=</span><span class="n">L</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">ListOfMyRecord</span><span class="p" data-group-id="3306842855-37">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1982910920-37">[</span><span class="nf">op</span><span class="p" data-group-id="1982910920-38">(</span><span class="n">L</span><span class="p" data-group-id="1982910920-38">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="o">#</span><span class="ss">my_record</span><span class="p" data-group-id="1982910920-39">{</span><span class="p" data-group-id="1982910920-39">}</span><span class="o">=</span><span class="n">L</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">ListOfMyRecord</span><span class="p" data-group-id="1982910920-37">]</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% AVOID, this silently filters out entries that do not match #my_record{}</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3306842855-40">[</span><span class="nf">op</span><span class="p" data-group-id="3306842855-41">(</span><span class="n">L</span><span class="p" data-group-id="3306842855-41">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="o">#</span><span class="ss">my_record</span><span class="p" data-group-id="3306842855-42">{</span><span class="p" data-group-id="3306842855-42">}</span><span class="o">=</span><span class="n">L</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">ListOfMyRecord</span><span class="p" data-group-id="3306842855-40">]</span></code></pre><p><a href="" id="rule-stl-002"></a></p><h4><a href="#rule-stl-002" title=""><code class="inline">STL-002</code></a> - Avoid Boolean Blindness</h4><p>Whenever boolean values have a context, prefer using more descriptive atoms to
│ │ │ │ +</span><span class="p" data-group-id="1982910920-40">[</span><span class="nf">op</span><span class="p" data-group-id="1982910920-41">(</span><span class="n">L</span><span class="p" data-group-id="1982910920-41">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="o">#</span><span class="ss">my_record</span><span class="p" data-group-id="1982910920-42">{</span><span class="p" data-group-id="1982910920-42">}</span><span class="o">=</span><span class="n">L</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">ListOfMyRecord</span><span class="p" data-group-id="1982910920-40">]</span></code></pre><p><a href="" id="rule-stl-002"></a></p><h4><a href="#rule-stl-002" title=""><code class="inline">STL-002</code></a> - Avoid Boolean Blindness</h4><p>Whenever boolean values have a context, prefer using more descriptive atoms to
│ │ │ │  express the boolean value, for example <code class="inline">initialized</code>/<code class="inline">uninitialized</code> or
│ │ │ │  <code class="inline">changed</code>/<code class="inline">unchanged</code>. This makes it easier to distinguish between different
│ │ │ │  boolean variables when many of them are used together, especially when matching
│ │ │ │  in function heads and the like.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Recommendation</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/628.html" title="">CWE-628</a></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="k">case</span><span class="w"> </span><span class="nf">my_filter</span><span class="p" data-group-id="5910300026-1">(</span><span class="n">List0</span><span class="p">,</span><span class="w"> </span><span class="ss">unchanged</span><span class="p" data-group-id="5910300026-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="k">case</span><span class="w"> </span><span class="nf">my_filter</span><span class="p" data-group-id="2764916586-1">(</span><span class="n">List0</span><span class="p">,</span><span class="w"> </span><span class="ss">unchanged</span><span class="p" data-group-id="2764916586-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │      </span><span class="ss">unchanged</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List0</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5910300026-2">{</span><span class="ss">changed</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="5910300026-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2764916586-2">{</span><span class="ss">changed</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="2764916586-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ │ -</span><span class="k">case</span><span class="w"> </span><span class="nf">my_filter</span><span class="p" data-group-id="5910300026-3">(</span><span class="n">List0</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="5910300026-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="k">case</span><span class="w"> </span><span class="nf">my_filter</span><span class="p" data-group-id="2764916586-3">(</span><span class="n">List0</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="2764916586-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │      </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List0</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5910300026-4">{</span><span class="ss">true</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="5910300026-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2764916586-4">{</span><span class="ss">true</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="2764916586-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p><a href="" id="rule-stl-003"></a></p><h4><a href="#rule-stl-003" title=""><code class="inline">STL-003</code></a> - Use Uppercase Names for Macros</h4><p>Macros are distinguished by a <code class="inline">?</code> prefix, so an accidental omission of the
│ │ │ │  prefix leaves the name there instead of applying the macro. For example,
│ │ │ │  <code class="inline">function_call(?my_macro, SomeArg)</code> becomes <code class="inline">function_call(my_macro, SomeArg)</code>
│ │ │ │  which is syntactically valid, hiding the error.</p><p>Static analysis tools can often find these issues, but a quicker way to find
│ │ │ │  them is to adopt the convention that all macros should be upper-case. Missing a
│ │ │ │  <code class="inline">?</code> will in most cases then lead to an unbound variable error or similar.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Recommendation</code></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7321220117-1">(</span><span class="n">MY_MACRO</span><span class="p">,</span><span class="w"> </span><span class="mi">65535</span><span class="p" data-group-id="7321220117-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0710580338-1">(</span><span class="n">MY_MACRO</span><span class="p">,</span><span class="w"> </span><span class="mi">65535</span><span class="p" data-group-id="0710580338-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7321220117-2">(</span><span class="ss">my_macro</span><span class="p">,</span><span class="w"> </span><span class="mi">65535</span><span class="p" data-group-id="7321220117-2">)</span><span class="p">.</span></code></pre><h3 id="deployment" class="section-heading">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0710580338-2">(</span><span class="ss">my_macro</span><span class="p">,</span><span class="w"> </span><span class="mi">65535</span><span class="p" data-group-id="0710580338-2">)</span><span class="p">.</span></code></pre><h3 id="deployment" class="section-heading">
│ │ │ │    <a href="#deployment" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Deployment</span>
│ │ │ │  </h3>
│ │ │ │  <p><a href="" id="rule-dep-001"></a></p><h4><a href="#rule-dep-001" title=""><code class="inline">DEP-001</code></a> - Do Not Expose Default Erlang Distribution on Untrusted Networks</h4><p>The builtin Erlang distribution makes it possible to easily and transparently
│ │ │ │  communicate between Erlang nodes. By default, communication is performed over
│ │ │ │ @@ -473,27 +473,27 @@
│ │ │ │  pervasive error handling throughout the code at large is drastically reduced,
│ │ │ │  and with it a large source of bugs and security issues.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Medium</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/389.html" title="">CWE-389</a>, <a href="https://cwe.mitre.org/data/definitions/544.html" title="">CWE-544</a>, <a href="https://cwe.mitre.org/data/definitions/653.html" title="">CWE-653</a>, <a href="#owasp-a10-2025" title=""><code class="inline">A10:2025</code></a></p><p><a href="" id="rule-dsg-002"></a></p><h4><a href="#rule-dsg-002" title=""><code class="inline">DSG-002</code></a> - Prefer Letting the User Decide What Warrants an Exception</h4><p>Prefer to design your interfaces so that the user decides whether an error is
│ │ │ │  exceptional or not, by following the <code class="inline">{ok, Result} | {error, Reason}</code>
│ │ │ │  convention. Generally speaking the user of an interface has more context than
│ │ │ │  the one implementing it, and giving them the freedom to choose through pattern
│ │ │ │  matching tends to result in clearer code as the handling of raised exceptions
│ │ │ │  is more difficult to follow.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Recommendation</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/389.html" title="">CWE-389</a>, <a href="#owasp-a10-2025" title=""><code class="inline">A10:2025</code></a></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% PREFER</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0886277021-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="0886277021-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">some_function</span><span class="p" data-group-id="0886277021-2">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0886277021-2">)</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1330713279-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="1330713279-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">some_function</span><span class="p" data-group-id="1330713279-2">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="1330713279-2">)</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% PREFER</span><span class="w">
│ │ │ │ -</span><span class="k">case</span><span class="w"> </span><span class="nf">some_function</span><span class="p" data-group-id="0886277021-3">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0886277021-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0886277021-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="0886277021-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="k">case</span><span class="w"> </span><span class="nf">some_function</span><span class="p" data-group-id="1330713279-3">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="1330713279-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1330713279-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="1330713279-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="c1">%% Happy path</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0886277021-5">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="0886277021-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1330713279-5">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="1330713279-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="c1">%% Handle it</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% AVOID</span><span class="w">
│ │ │ │ -</span><span class="k">try</span><span class="w"> </span><span class="nf">some_function</span><span class="p" data-group-id="0886277021-6">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0886277021-6">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="k">try</span><span class="w"> </span><span class="nf">some_function</span><span class="p" data-group-id="1330713279-6">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="1330713279-6">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │      </span><span class="n">C</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> 
│ │ │ │          </span><span class="c1">%% Happy path</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ │      </span><span class="nc">error</span><span class="p">:</span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="c1">%% Handle it</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p><a href="" id="rule-dsg-003"></a></p><h4><a href="#rule-dsg-003" title=""><code class="inline">DSG-003</code></a> - Do Not Abuse Atoms</h4><p>Atoms are designed to provide an easy way to create named constants in code.
│ │ │ │ @@ -515,23 +515,23 @@
│ │ │ │  <a href="#rule-dsg-011" title=""><code class="inline">DSG-011</code></a>) unless the API also provides some way of preventing creation of
│ │ │ │  atoms. For example, <a href="../../../lib/../erts/doc/html/erlang.html#binary_to_term/2" title=""><code class="inline">binary_to_term/2</code></a> with the <code class="inline">safe</code> option will prevent
│ │ │ │  new atoms from being created. However, note that even if the <code class="inline">safe</code> option is
│ │ │ │  used and the data originates from an untrusted source, it still has to be
│ │ │ │  validated and sanitized, since it can still be harmful to the Erlang
│ │ │ │  application in other ways.</p><p>In general, it is best to avoid using such functions altogether on untrusted
│ │ │ │  data, even with the <code class="inline">safe</code> option.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">High</code></p><p>Related CWEs and OWASP risks: <a href="#cwe-770" title=""><code class="inline">CWE-770</code></a>, <a href="#owasp-api10-2023" title=""><code class="inline">API10:2023</code></a></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO, AND PREFER (see STL-001)</span><span class="w">
│ │ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="6984331609-1">(</span><span class="p" data-group-id="6984331609-2">&lt;&lt;</span><span class="s">&quot;foo&quot;</span><span class="p" data-group-id="6984331609-2">&gt;&gt;</span><span class="p" data-group-id="6984331609-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">foo</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="6984331609-3">(</span><span class="p" data-group-id="6984331609-4">&lt;&lt;</span><span class="s">&quot;bar&quot;</span><span class="p" data-group-id="6984331609-4">&gt;&gt;</span><span class="p" data-group-id="6984331609-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">bar</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="6984331609-5">(</span><span class="p" data-group-id="6984331609-6">&lt;&lt;</span><span class="s">&quot;quux&quot;</span><span class="p" data-group-id="6984331609-6">&gt;&gt;</span><span class="p" data-group-id="6984331609-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">quux</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="8413013370-1">(</span><span class="p" data-group-id="8413013370-2">&lt;&lt;</span><span class="s">&quot;foo&quot;</span><span class="p" data-group-id="8413013370-2">&gt;&gt;</span><span class="p" data-group-id="8413013370-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">foo</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="8413013370-3">(</span><span class="p" data-group-id="8413013370-4">&lt;&lt;</span><span class="s">&quot;bar&quot;</span><span class="p" data-group-id="8413013370-4">&gt;&gt;</span><span class="p" data-group-id="8413013370-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">bar</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="8413013370-5">(</span><span class="p" data-group-id="8413013370-6">&lt;&lt;</span><span class="s">&quot;quux&quot;</span><span class="p" data-group-id="8413013370-6">&gt;&gt;</span><span class="p" data-group-id="8413013370-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">quux</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="6984331609-7">(</span><span class="n">Text</span><span class="p" data-group-id="6984331609-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">binary_to_existing_atom</span><span class="p" data-group-id="6984331609-8">(</span><span class="n">Text</span><span class="p" data-group-id="6984331609-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="8413013370-7">(</span><span class="n">Text</span><span class="p" data-group-id="8413013370-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">binary_to_existing_atom</span><span class="p" data-group-id="8413013370-8">(</span><span class="n">Text</span><span class="p" data-group-id="8413013370-8">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="6984331609-9">(</span><span class="n">Text</span><span class="p" data-group-id="6984331609-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">binary_to_atom</span><span class="p" data-group-id="6984331609-10">(</span><span class="n">Text</span><span class="p" data-group-id="6984331609-10">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-dsg-004"></a></p><h4><a href="#rule-dsg-004" title=""><code class="inline">DSG-004</code></a> - Do Not Use Undocumented Functionality</h4><p>Undocumented functions or functionality must <strong>never</strong> be used. This includes
│ │ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="8413013370-9">(</span><span class="n">Text</span><span class="p" data-group-id="8413013370-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">binary_to_atom</span><span class="p" data-group-id="8413013370-10">(</span><span class="n">Text</span><span class="p" data-group-id="8413013370-10">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-dsg-004"></a></p><h4><a href="#rule-dsg-004" title=""><code class="inline">DSG-004</code></a> - Do Not Use Undocumented Functionality</h4><p>Undocumented functions or functionality must <strong>never</strong> be used. This includes
│ │ │ │  undocumented arguments to documented functions and undocumented system
│ │ │ │  services. Using such functionality poses a serious security risk. These
│ │ │ │  functions and features are intended strictly for internal use within Erlang/OTP
│ │ │ │  and are not supported for external use.</p><p>Merely passing the wrong arguments to these functions can cause the system to
│ │ │ │  behave in unexpected ways from that point on, and their behavior may change or
│ │ │ │  they may be removed without prior notice.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Critical</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/242.html" title="">CWE-242</a>, <a href="https://cwe.mitre.org/data/definitions/477.html" title="">CWE-477</a>, <a href="https://cwe.mitre.org/data/definitions/676.html" title="">CWE-676</a></p><p><a href="" id="rule-dsg-005"></a></p><h4><a href="#rule-dsg-005" title=""><code class="inline">DSG-005</code></a> - Do Not Use Deprecated Functionality</h4><p>When functionality is deprecated in Erlang/OTP, the documentation will
│ │ │ │  typically point to other or new functionality to use instead. The deprecation
│ │ │ │ @@ -572,28 +572,28 @@
│ │ │ │  them through their name instead of their process or table identifier. This
│ │ │ │  should be used with care, as a process or table may terminate at any time.
│ │ │ │  For example, if two messages are sent to a process through a registered name,
│ │ │ │  the second message may arrive to a newly restarted process that has not seen
│ │ │ │  the first, which may be significant (<a href="https://cwe.mitre.org/data/definitions/386.html" title="">CWE-386</a>).</p><p>To prevent these issues, either redesign your interface so that multiple
│ │ │ │  messages or lookups are not necessary, or look up the identifier from the
│ │ │ │  registered name and use the identifier instead.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Recommendation</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/386.html" title="">CWE-386</a></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="n">Pid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="9171297671-1">(</span><span class="ss">registered_process</span><span class="p" data-group-id="9171297671-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Pid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="5311960800-1">(</span><span class="ss">registered_process</span><span class="p" data-group-id="5311960800-1">)</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">hello</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">world</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Tid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">whereis</span><span class="p" data-group-id="9171297671-2">(</span><span class="ss">registered_table</span><span class="p" data-group-id="9171297671-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="9171297671-3">(</span><span class="n">Tid</span><span class="p">,</span><span class="w"> </span><span class="n">KeyA</span><span class="p" data-group-id="9171297671-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="9171297671-4">(</span><span class="n">Tid</span><span class="p">,</span><span class="w"> </span><span class="n">KeyB</span><span class="p" data-group-id="9171297671-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Tid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">whereis</span><span class="p" data-group-id="5311960800-2">(</span><span class="ss">registered_table</span><span class="p" data-group-id="5311960800-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="5311960800-3">(</span><span class="n">Tid</span><span class="p">,</span><span class="w"> </span><span class="n">KeyA</span><span class="p" data-group-id="5311960800-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="5311960800-4">(</span><span class="n">Tid</span><span class="p">,</span><span class="w"> </span><span class="n">KeyB</span><span class="p" data-group-id="5311960800-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ │  </span><span class="ss">registered_process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">hello</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="ss">registered_process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">world</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="9171297671-5">(</span><span class="ss">registered_table</span><span class="p">,</span><span class="w"> </span><span class="n">KeyA</span><span class="p" data-group-id="9171297671-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="9171297671-6">(</span><span class="ss">registered_table</span><span class="p">,</span><span class="w"> </span><span class="n">KeyB</span><span class="p" data-group-id="9171297671-6">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-dsg-011"></a></p><h4><a href="#rule-dsg-011" title=""><code class="inline">DSG-011</code></a> - Only Deserialize Trusted Data</h4><p>Erlang/OTP provides various functionality that serializes and deserializes
│ │ │ │ +</span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="5311960800-5">(</span><span class="ss">registered_table</span><span class="p">,</span><span class="w"> </span><span class="n">KeyA</span><span class="p" data-group-id="5311960800-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="5311960800-6">(</span><span class="ss">registered_table</span><span class="p">,</span><span class="w"> </span><span class="n">KeyB</span><span class="p" data-group-id="5311960800-6">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-dsg-011"></a></p><h4><a href="#rule-dsg-011" title=""><code class="inline">DSG-011</code></a> - Only Deserialize Trusted Data</h4><p>Erlang/OTP provides various functionality that serializes and deserializes
│ │ │ │  general Erlang terms. Such functionality is intended to be used in a trusted
│ │ │ │  environment and is not suitable for communication with untrusted entities. For
│ │ │ │  example, you do not want to load a <a href="../../../lib/mnesia/doc/html/index.html" title=""><code class="inline">mnesia</code></a> backup from an untrusted entity.
│ │ │ │  One issue with this being the potential for atom exhaustion, but more
│ │ │ │  importantly you could potentially end up with a <code class="inline">mnesia</code> table containing
│ │ │ │  harmful data (<a href="#cwe-502" title=""><code class="inline">CWE-502</code></a>). Other examples are <a href="../../../lib/stdlib/doc/html/dets.html"><code class="inline">dets</code></a> and <a href="../../../lib/kernel/doc/html/disk_log.html"><code class="inline">disk_log</code></a>.</p><p>JSON is an example of a better format to use when communicating with untrusted
│ │ │ │  entities. Erlang/OTP provides the <a href="../../../lib/stdlib/doc/html/json.html"><code class="inline">json</code></a> module for JSON encoding/decoding.
│ │ │ │ @@ -610,51 +610,51 @@
│ │ │ │    <span class="text">Language</span>
│ │ │ │  </h3>
│ │ │ │  <p><a href="" id="rule-lng-001"></a></p><h4><a href="#rule-lng-001" title=""><code class="inline">LNG-001</code></a> - Prefer Tuples Over Exporting Variables</h4><p>For historical reasons, Erlang does not employ lexical scoping, and variables
│ │ │ │  defined in &quot;inner&quot; expressions are available in &quot;outer&quot; expressions that follow
│ │ │ │  them. Using this makes code harder to reason about, and it is preferable to
│ │ │ │  write your code as if Erlang has lexical scoping by returning a tuple instead.
│ │ │ │  There are no performance penalties for doing this.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Recommendation</code></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="nf">some_function</span><span class="p" data-group-id="6215518405-1">(</span><span class="n">State0</span><span class="p" data-group-id="6215518405-1">)</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6215518405-2">{</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="6215518405-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="6215518405-3">(</span><span class="n">State0</span><span class="p" data-group-id="6215518405-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -                      </span><span class="p" data-group-id="6215518405-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="6215518405-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                          </span><span class="p" data-group-id="6215518405-5">{</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="nf">bar</span><span class="p" data-group-id="6215518405-6">(</span><span class="n">A</span><span class="p" data-group-id="6215518405-6">)</span><span class="p" data-group-id="6215518405-5">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">some_function</span><span class="p" data-group-id="8152676808-1">(</span><span class="n">State0</span><span class="p" data-group-id="8152676808-1">)</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8152676808-2">{</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="8152676808-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="8152676808-3">(</span><span class="n">State0</span><span class="p" data-group-id="8152676808-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +                      </span><span class="p" data-group-id="8152676808-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="8152676808-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                          </span><span class="p" data-group-id="8152676808-5">{</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="nf">bar</span><span class="p" data-group-id="8152676808-6">(</span><span class="n">A</span><span class="p" data-group-id="8152676808-6">)</span><span class="p" data-group-id="8152676808-5">}</span><span class="p">;</span><span class="w">
│ │ │ │                        </span><span class="ss">b</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                          </span><span class="p" data-group-id="6215518405-7">{</span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">State0</span><span class="p" data-group-id="6215518405-7">}</span><span class="w">
│ │ │ │ +                          </span><span class="p" data-group-id="8152676808-7">{</span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">State0</span><span class="p" data-group-id="8152676808-7">}</span><span class="w">
│ │ │ │                    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">bar</span><span class="p" data-group-id="6215518405-8">(</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="6215518405-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">bar</span><span class="p" data-group-id="8152676808-8">(</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="8152676808-8">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ │ -</span><span class="nf">some_function</span><span class="p" data-group-id="6215518405-9">(</span><span class="n">State0</span><span class="p" data-group-id="6215518405-9">)</span><span class="w">
│ │ │ │ -    </span><span class="n">C</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="6215518405-10">(</span><span class="n">State0</span><span class="p" data-group-id="6215518405-10">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="6215518405-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="6215518405-11">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="n">State1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">bar</span><span class="p" data-group-id="6215518405-12">(</span><span class="n">A</span><span class="p" data-group-id="6215518405-12">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">some_function</span><span class="p" data-group-id="8152676808-9">(</span><span class="n">State0</span><span class="p" data-group-id="8152676808-9">)</span><span class="w">
│ │ │ │ +    </span><span class="n">C</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="8152676808-10">(</span><span class="n">State0</span><span class="p" data-group-id="8152676808-10">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="8152676808-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="8152676808-11">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                </span><span class="n">State1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">bar</span><span class="p" data-group-id="8152676808-12">(</span><span class="n">A</span><span class="p" data-group-id="8152676808-12">)</span><span class="p">,</span><span class="w">
│ │ │ │                  </span><span class="ss">a</span><span class="p">;</span><span class="w">
│ │ │ │              </span><span class="ss">b</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                  </span><span class="n">State1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">State0</span><span class="p">,</span><span class="w">
│ │ │ │                  </span><span class="ss">b</span><span class="w">
│ │ │ │          </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">bar</span><span class="p" data-group-id="6215518405-13">(</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="6215518405-13">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-lng-002"></a></p><h4><a href="#rule-lng-002" title=""><code class="inline">LNG-002</code></a> - Do Not Use <code class="inline">catch</code></h4><p>The legacy <code class="inline">catch</code> construct cannot distinguish between <a href="../../../lib/../erts/doc/html/erlang.html#throw/1"><code class="inline">throw/1</code></a> and a normal
│ │ │ │ +    </span><span class="nf">bar</span><span class="p" data-group-id="8152676808-13">(</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="8152676808-13">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-lng-002"></a></p><h4><a href="#rule-lng-002" title=""><code class="inline">LNG-002</code></a> - Do Not Use <code class="inline">catch</code></h4><p>The legacy <code class="inline">catch</code> construct cannot distinguish between <a href="../../../lib/../erts/doc/html/erlang.html#throw/1"><code class="inline">throw/1</code></a> and a normal
│ │ │ │  return, which can have very unexpected results. For instance, the
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_server.html"><code class="inline">gen_server</code></a> behavior will unintentionally accept any documented return value
│ │ │ │  when thrown because of its use of <code class="inline">catch</code>.</p><p>Instead, the modern <a href="../../../lib/../system/doc/html/expressions.html"><code class="inline">try ... catch ... end</code></a>
│ │ │ │  construct should be used.</p><p>Starting from Erlang/OTP 29, the compiler will by default raise
│ │ │ │  warnings for uses of the legacy <code class="inline">catch</code> construct.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Recommendation</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/253.html" title="">CWE-253</a>, <a href="https://cwe.mitre.org/data/definitions/480.html" title="">CWE-480</a>, <a href="#owasp-a10-2025" title=""><code class="inline">A10:2025</code></a></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="k">try</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="0186820566-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0186820566-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="k">try</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="7244755674-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="7244755674-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │      </span><span class="n">C</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ │      </span><span class="nc">throw</span><span class="p">:</span><span class="n">Value</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="nc">error</span><span class="p">:</span><span class="n">Reason</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ │ -</span><span class="nf">case</span><span class="w"> </span><span class="p" data-group-id="0186820566-2">(</span><span class="k">catch</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="0186820566-3">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0186820566-3">)</span><span class="p" data-group-id="0186820566-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0186820566-4">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="0186820566-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">case</span><span class="w"> </span><span class="p" data-group-id="7244755674-2">(</span><span class="k">catch</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="7244755674-3">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="7244755674-3">)</span><span class="p" data-group-id="7244755674-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7244755674-4">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="7244755674-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="n">C</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p><a href="" id="rule-lng-003"></a></p><h4><a href="#rule-lng-003" title=""><code class="inline">LNG-003</code></a> - Do Not Use the Legacy <code class="inline">and</code> and <code class="inline">or</code> Operators</h4><p>These operators have been superseded by <code class="inline">andalso</code> and <code class="inline">orelse</code>, respectively.</p><p>The legacy operators have higher precedence than in most other languages. For
│ │ │ │  example <code class="inline">X and Y =:= 3</code> is parsed as <code class="inline">(X and Y) =:= 3</code>. In a function body,
│ │ │ │  this will crash, but when used in a guard it will silently fail. It can also
│ │ │ │  unexpectedly corrupt the intended logic without crashing when all operands are
│ │ │ │ @@ -723,38 +723,38 @@
│ │ │ │  leaking out through a crash or core dump.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Medium</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/209.html" title="">CWE-209</a>, <a href="https://cwe.mitre.org/data/definitions/532.html" title="">CWE-532</a></p><p><a href="" id="rule-msc-005"></a></p><h4><a href="#rule-msc-005" title=""><code class="inline">MSC-005</code></a> - Treat Match Specifications As Code</h4><p>Match specifications, such as those used with ETS, are vulnerable to injection
│ │ │ │  attacks if they are constructed based on untrusted input.</p><p>When untrusted data is matched verbatim (such as a key), it is important to
│ │ │ │  wrap it in <code class="inline">{const, UntrustedData}</code> expressions. Building general queries based
│ │ │ │  on untrusted data should be avoided, but if that cannot be done, the query
│ │ │ │  should be the result of <em>parsing</em> the untrusted data into a match
│ │ │ │  specification (where the final shape is controlled by the programmer), rather
│ │ │ │  than attempting to <em>validate</em> the data before passing it in unaltered.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">High</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/74.html" title="">CWE-74</a></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="nf">find</span><span class="p" data-group-id="9713526495-1">(</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Needle</span><span class="p" data-group-id="9713526495-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match</span><span class="p" data-group-id="9713526495-2">(</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9713526495-3">{</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9713526495-4">{</span><span class="ss">const</span><span class="p">,</span><span class="w"> </span><span class="n">Needle</span><span class="p" data-group-id="9713526495-4">}</span><span class="p">,</span><span class="w"> </span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="9713526495-3">}</span><span class="p" data-group-id="9713526495-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">find</span><span class="p" data-group-id="7049282391-1">(</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Needle</span><span class="p" data-group-id="7049282391-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match</span><span class="p" data-group-id="7049282391-2">(</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7049282391-3">{</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7049282391-4">{</span><span class="ss">const</span><span class="p">,</span><span class="w"> </span><span class="n">Needle</span><span class="p" data-group-id="7049282391-4">}</span><span class="p">,</span><span class="w"> </span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="7049282391-3">}</span><span class="p" data-group-id="7049282391-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ │ -</span><span class="nf">find</span><span class="p" data-group-id="9713526495-5">(</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Needle</span><span class="p" data-group-id="9713526495-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match</span><span class="p" data-group-id="9713526495-6">(</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9713526495-7">{</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Needle</span><span class="p">,</span><span class="w"> </span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="9713526495-7">}</span><span class="p" data-group-id="9713526495-6">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-msc-006"></a></p><h4><a href="#rule-msc-006" title=""><code class="inline">MSC-006</code></a> - Consider &quot;Link Following&quot; Attacks</h4><p>When operating on untrusted file paths and trying to access files through them,
│ │ │ │ +</span><span class="nf">find</span><span class="p" data-group-id="7049282391-5">(</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Needle</span><span class="p" data-group-id="7049282391-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match</span><span class="p" data-group-id="7049282391-6">(</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7049282391-7">{</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Needle</span><span class="p">,</span><span class="w"> </span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="7049282391-7">}</span><span class="p" data-group-id="7049282391-6">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-msc-006"></a></p><h4><a href="#rule-msc-006" title=""><code class="inline">MSC-006</code></a> - Consider &quot;Link Following&quot; Attacks</h4><p>When operating on untrusted file paths and trying to access files through them,
│ │ │ │  it is possible that the name does not actually identify a file, but a link
│ │ │ │  instead, which can in turn point at an unintended resource which is potentially
│ │ │ │  outside of the intended boundaries.</p><p>This can be mitigated by using <a href="../../../lib/stdlib/doc/html/filelib.html#safe_relative_path/2"><code class="inline">filelib:safe_relative_path/2</code></a> to ensure that
│ │ │ │  the path does not escape the given bounds regardless of links. Note that it is
│ │ │ │  impossible to guarantee atomicity across several filesystem operations, so care
│ │ │ │  must be taken to avoid time-of-check time-of-use (TOCTOU) race conditions where
│ │ │ │  a file or symbolic link is swapped out in the middle of these operations. When
│ │ │ │  operating on a shared folder structure, ensure that only one entity has access
│ │ │ │  to said structure.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Medium</code></p><p>Related CWEs and OWASP risks: <a href="#cwe-22" title=""><code class="inline">CWE-22</code></a>, <a href="https://cwe.mitre.org/data/definitions/59.html" title="">CWE-59</a>, <a href="https://cwe.mitre.org/data/definitions/61.html" title="">CWE-61</a></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="4252036892-1">(</span><span class="n">UntrustedPath</span><span class="p">,</span><span class="w"> </span><span class="n">Root</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4252036892-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">filelib</span><span class="p">:</span><span class="nf">safe_relative_path</span><span class="p" data-group-id="4252036892-2">(</span><span class="n">UntrustedPath</span><span class="p">,</span><span class="w"> </span><span class="n">Root</span><span class="p" data-group-id="4252036892-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="ss">unsafe</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4252036892-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">unsafe</span><span class="p" data-group-id="4252036892-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="n">Path</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="4252036892-4">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4252036892-5">(</span><span class="n">Root</span><span class="p">,</span><span class="w"> </span><span class="n">Path</span><span class="p" data-group-id="4252036892-5">)</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4252036892-4">)</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="1304377204-1">(</span><span class="n">UntrustedPath</span><span class="p">,</span><span class="w"> </span><span class="n">Root</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="1304377204-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">filelib</span><span class="p">:</span><span class="nf">safe_relative_path</span><span class="p" data-group-id="1304377204-2">(</span><span class="n">UntrustedPath</span><span class="p">,</span><span class="w"> </span><span class="n">Root</span><span class="p" data-group-id="1304377204-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +        </span><span class="ss">unsafe</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1304377204-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">unsafe</span><span class="p" data-group-id="1304377204-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="n">Path</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="1304377204-4">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1304377204-5">(</span><span class="n">Root</span><span class="p">,</span><span class="w"> </span><span class="n">Path</span><span class="p" data-group-id="1304377204-5">)</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="1304377204-4">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ │ -</span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="4252036892-6">(</span><span class="n">UntrustedPath</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4252036892-6">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-msc-007"></a></p><h4><a href="#rule-msc-007" title=""><code class="inline">MSC-007</code></a> - Avoid Using Debug Functionality in Production</h4><p>Functionality that has been explicitly marked to be used only for debugging,
│ │ │ │ +</span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="1304377204-6">(</span><span class="n">UntrustedPath</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="1304377204-6">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-msc-007"></a></p><h4><a href="#rule-msc-007" title=""><code class="inline">MSC-007</code></a> - Avoid Using Debug Functionality in Production</h4><p>Functionality that has been explicitly marked to be used only for debugging,
│ │ │ │  such as <a href="../../../lib/../erts/doc/html/erlang.html#list_to_pid/1"><code class="inline">erlang:list_to_pid/1</code></a> or the <a href="../../../lib/ssl/doc/html/ssl.html#t:common_option/0"><code class="inline">keep_secrets</code></a>
│ │ │ │  <a href="../../../lib/ssl/doc/html/index.html" title=""><code class="inline">ssl</code></a> option should not be used in production environments, except during
│ │ │ │  interactive debugging. Unlike with normal functionality, there are no promises
│ │ │ │  of API stability for debug functionality, and they may change without notice.
│ │ │ │  They sometimes also have adverse effects on system properties while used (such
│ │ │ │  as greatly increasing scheduling latency), which are acceptable during
│ │ │ │  testing but not in production.</p><p>In production environments, debug functionality should be considered unsafe as
│ │ │ ├── OEBPS/robustness.xhtml
│ │ │ │ @@ -33,68 +33,68 @@
│ │ │ │  </h2>
│ │ │ │  <p>Before improving the messenger program, let us look at some general principles,
│ │ │ │  using the ping pong program as an example. Recall that when &quot;ping&quot; finishes, it
│ │ │ │  tells &quot;pong&quot; that it has done so by sending the atom <code class="inline">finished</code> as a message to
│ │ │ │  &quot;pong&quot; so that &quot;pong&quot; can also finish. Another way to let &quot;pong&quot; finish is to
│ │ │ │  make &quot;pong&quot; exit if it does not receive a message from ping within a certain
│ │ │ │  time. This can be done by adding a <em>time-out</em> to <code class="inline">pong</code> as shown in the
│ │ │ │ -following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8388792907-1">(</span><span class="ss">tut19</span><span class="p" data-group-id="8388792907-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4685176694-1">(</span><span class="ss">tut19</span><span class="p" data-group-id="4685176694-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8388792907-2">(</span><span class="p" data-group-id="8388792907-3">[</span><span class="ss">start_ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">start_pong</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8388792907-3">]</span><span class="p" data-group-id="8388792907-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4685176694-2">(</span><span class="p" data-group-id="4685176694-3">[</span><span class="ss">start_ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">start_pong</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4685176694-3">]</span><span class="p" data-group-id="4685176694-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="8388792907-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="8388792907-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8388792907-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8388792907-6">[</span><span class="p" data-group-id="8388792907-6">]</span><span class="p" data-group-id="8388792907-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="4685176694-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="4685176694-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4685176694-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4685176694-6">[</span><span class="p" data-group-id="4685176694-6">]</span><span class="p" data-group-id="4685176694-5">)</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="8388792907-7">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="8388792907-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8388792907-8">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="8388792907-8">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8388792907-9">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8388792907-10">(</span><span class="p" data-group-id="8388792907-10">)</span><span class="p" data-group-id="8388792907-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="4685176694-7">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="4685176694-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4685176694-8">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="4685176694-8">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4685176694-9">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4685176694-10">(</span><span class="p" data-group-id="4685176694-10">)</span><span class="p" data-group-id="4685176694-9">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8388792907-11">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8388792907-12">[</span><span class="p" data-group-id="8388792907-12">]</span><span class="p" data-group-id="8388792907-11">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4685176694-11">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4685176694-12">[</span><span class="p" data-group-id="4685176694-12">]</span><span class="p" data-group-id="4685176694-11">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="8388792907-13">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="8388792907-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="4685176694-13">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="4685176694-13">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="8388792907-14">(</span><span class="p" data-group-id="8388792907-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="4685176694-14">(</span><span class="p" data-group-id="4685176694-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8388792907-15">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="8388792907-15">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8388792907-16">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8388792907-17">[</span><span class="p" data-group-id="8388792907-17">]</span><span class="p" data-group-id="8388792907-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="4685176694-15">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="4685176694-15">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4685176694-16">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4685176694-17">[</span><span class="p" data-group-id="4685176694-17">]</span><span class="p" data-group-id="4685176694-16">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="8388792907-18">(</span><span class="p" data-group-id="8388792907-18">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="4685176694-18">(</span><span class="p" data-group-id="4685176694-18">)</span><span class="w">
│ │ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8388792907-19">(</span><span class="s">&quot;Pong timed out</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8388792907-20">[</span><span class="p" data-group-id="8388792907-20">]</span><span class="p" data-group-id="8388792907-19">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4685176694-19">(</span><span class="s">&quot;Pong timed out</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4685176694-20">[</span><span class="p" data-group-id="4685176694-20">]</span><span class="p" data-group-id="4685176694-19">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_pong</span><span class="p" data-group-id="8388792907-21">(</span><span class="p" data-group-id="8388792907-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="8388792907-22">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="8388792907-23">(</span><span class="ss">tut19</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8388792907-24">[</span><span class="p" data-group-id="8388792907-24">]</span><span class="p" data-group-id="8388792907-23">)</span><span class="p" data-group-id="8388792907-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_pong</span><span class="p" data-group-id="4685176694-21">(</span><span class="p" data-group-id="4685176694-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="4685176694-22">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="4685176694-23">(</span><span class="ss">tut19</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4685176694-24">[</span><span class="p" data-group-id="4685176694-24">]</span><span class="p" data-group-id="4685176694-23">)</span><span class="p" data-group-id="4685176694-22">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_ping</span><span class="p" data-group-id="8388792907-25">(</span><span class="n">Pong_Node</span><span class="p" data-group-id="8388792907-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="8388792907-26">(</span><span class="ss">tut19</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8388792907-27">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="8388792907-27">]</span><span class="p" data-group-id="8388792907-26">)</span><span class="p">.</span></code></pre><p>After this is compiled and the file <code class="inline">tut19.beam</code> is copied to the necessary
│ │ │ │ +</span><span class="nf">start_ping</span><span class="p" data-group-id="4685176694-25">(</span><span class="n">Pong_Node</span><span class="p" data-group-id="4685176694-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="4685176694-26">(</span><span class="ss">tut19</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4685176694-27">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="4685176694-27">]</span><span class="p" data-group-id="4685176694-26">)</span><span class="p">.</span></code></pre><p>After this is compiled and the file <code class="inline">tut19.beam</code> is copied to the necessary
│ │ │ │  directories, the following is seen on (pong@kosken):</p><pre><code class="text">(pong@kosken)1&gt; tut19:start_pong().
│ │ │ │  true
│ │ │ │  Pong received ping
│ │ │ │  Pong received ping
│ │ │ │  Pong received ping
│ │ │ │  Pong timed out</code></pre><p>And the following is seen on (ping@gollum):</p><pre><code class="text">(ping@gollum)1&gt; tut19:start_ping(pong@kosken).
│ │ │ │  &lt;0.36.0&gt;
│ │ │ │  Ping received pong
│ │ │ │  Ping received pong
│ │ │ │  Ping received pong
│ │ │ │ -ping finished</code></pre><p>The time-out is set in:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pong</span><span class="p" data-group-id="3009041411-1">(</span><span class="p" data-group-id="3009041411-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +ping finished</code></pre><p>The time-out is set in:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pong</span><span class="p" data-group-id="1899071091-1">(</span><span class="p" data-group-id="1899071091-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3009041411-2">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="3009041411-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3009041411-3">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3009041411-4">[</span><span class="p" data-group-id="3009041411-4">]</span><span class="p" data-group-id="3009041411-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="1899071091-2">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="1899071091-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1899071091-3">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1899071091-4">[</span><span class="p" data-group-id="1899071091-4">]</span><span class="p" data-group-id="1899071091-3">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="3009041411-5">(</span><span class="p" data-group-id="3009041411-5">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="1899071091-5">(</span><span class="p" data-group-id="1899071091-5">)</span><span class="w">
│ │ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3009041411-6">(</span><span class="s">&quot;Pong timed out</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3009041411-7">[</span><span class="p" data-group-id="3009041411-7">]</span><span class="p" data-group-id="3009041411-6">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1899071091-6">(</span><span class="s">&quot;Pong timed out</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1899071091-7">[</span><span class="p" data-group-id="1899071091-7">]</span><span class="p" data-group-id="1899071091-6">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The time-out (<code class="inline">after 5000</code>) is started when <code class="inline">receive</code> is entered. The time-out
│ │ │ │  is canceled if <code class="inline">{ping,Ping_PID}</code> is received. If <code class="inline">{ping,Ping_PID}</code> is not
│ │ │ │  received, the actions following the time-out are done after 5000 milliseconds.
│ │ │ │  <code class="inline">after</code> must be last in the <code class="inline">receive</code>, that is, preceded by all other message
│ │ │ │  reception specifications in the <code class="inline">receive</code>. It is also possible to call a
│ │ │ │ -function that returns an integer for the time-out:</p><pre><code class="makeup erlang" translate="no"><span class="k">after</span><span class="w"> </span><span class="nf">pong_timeout</span><span class="p" data-group-id="2605303717-1">(</span><span class="p" data-group-id="2605303717-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>In general, there are better ways than using time-outs to supervise parts of a
│ │ │ │ +function that returns an integer for the time-out:</p><pre><code class="makeup erlang" translate="no"><span class="k">after</span><span class="w"> </span><span class="nf">pong_timeout</span><span class="p" data-group-id="2581216232-1">(</span><span class="p" data-group-id="2581216232-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>In general, there are better ways than using time-outs to supervise parts of a
│ │ │ │  distributed Erlang system. Time-outs are usually appropriate to supervise
│ │ │ │  external events, for example, if you have expected a message from some external
│ │ │ │  system within a specified time. For example, a time-out can be used to log a
│ │ │ │  user out of the messenger system if they have not accessed it for, say, ten
│ │ │ │  minutes.</p><h2 id="error-handling" class="section-heading">
│ │ │ │    <a href="#error-handling" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │ @@ -114,96 +114,96 @@
│ │ │ │  something called a <em>signal</em> to all the processes it has links to.</p><p>The signal carries information about the pid it was sent from and the exit
│ │ │ │  reason.</p><p>The default behaviour of a process that receives a normal exit is to ignore the
│ │ │ │  signal.</p><p>The default behaviour in the two other cases (that is, abnormal exit) above is
│ │ │ │  to:</p><ul><li>Bypass all messages to the receiving process.</li><li>Kill the receiving process.</li><li>Propagate the same error signal to the links of the killed process.</li></ul><p>In this way you can connect all processes in a transaction together using links.
│ │ │ │  If one of the processes exits abnormally, all the processes in the transaction
│ │ │ │  are killed. As it is often wanted to create a process and link to it at the same
│ │ │ │  time, there is a special BIF, <a href="../../../lib/../erts/doc/html/erlang.html#spawn_link/1">spawn_link</a> that does the
│ │ │ │ -same as <code class="inline">spawn</code>, but also creates a link to the spawned process.</p><p>Now an example of the ping pong example using links to terminate &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1418847151-1">(</span><span class="ss">tut20</span><span class="p" data-group-id="1418847151-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +same as <code class="inline">spawn</code>, but also creates a link to the spawned process.</p><p>Now an example of the ping pong example using links to terminate &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7564624931-1">(</span><span class="ss">tut20</span><span class="p" data-group-id="7564624931-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1418847151-2">(</span><span class="p" data-group-id="1418847151-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1418847151-3">]</span><span class="p" data-group-id="1418847151-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7564624931-2">(</span><span class="p" data-group-id="7564624931-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7564624931-3">]</span><span class="p" data-group-id="7564624931-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="1418847151-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1418847151-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">link</span><span class="p" data-group-id="1418847151-5">(</span><span class="n">Pong_Pid</span><span class="p" data-group-id="1418847151-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping1</span><span class="p" data-group-id="1418847151-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1418847151-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="7564624931-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="7564624931-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">link</span><span class="p" data-group-id="7564624931-5">(</span><span class="n">Pong_Pid</span><span class="p" data-group-id="7564624931-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping1</span><span class="p" data-group-id="7564624931-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="7564624931-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping1</span><span class="p" data-group-id="1418847151-7">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="1418847151-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">exit</span><span class="p" data-group-id="1418847151-8">(</span><span class="ss">ping</span><span class="p" data-group-id="1418847151-8">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">ping1</span><span class="p" data-group-id="7564624931-7">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7564624931-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">exit</span><span class="p" data-group-id="7564624931-8">(</span><span class="ss">ping</span><span class="p" data-group-id="7564624931-8">)</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping1</span><span class="p" data-group-id="1418847151-9">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1418847151-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Pong_Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1418847151-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1418847151-11">(</span><span class="p" data-group-id="1418847151-11">)</span><span class="p" data-group-id="1418847151-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">ping1</span><span class="p" data-group-id="7564624931-9">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="7564624931-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pong_Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7564624931-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7564624931-11">(</span><span class="p" data-group-id="7564624931-11">)</span><span class="p" data-group-id="7564624931-10">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1418847151-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1418847151-13">[</span><span class="p" data-group-id="1418847151-13">]</span><span class="p" data-group-id="1418847151-12">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7564624931-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7564624931-13">[</span><span class="p" data-group-id="7564624931-13">]</span><span class="p" data-group-id="7564624931-12">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping1</span><span class="p" data-group-id="1418847151-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1418847151-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping1</span><span class="p" data-group-id="7564624931-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="7564624931-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="1418847151-15">(</span><span class="p" data-group-id="1418847151-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="7564624931-15">(</span><span class="p" data-group-id="7564624931-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1418847151-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="1418847151-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1418847151-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1418847151-18">[</span><span class="p" data-group-id="1418847151-18">]</span><span class="p" data-group-id="1418847151-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="7564624931-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="7564624931-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7564624931-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7564624931-18">[</span><span class="p" data-group-id="7564624931-18">]</span><span class="p" data-group-id="7564624931-17">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="1418847151-19">(</span><span class="p" data-group-id="1418847151-19">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="7564624931-19">(</span><span class="p" data-group-id="7564624931-19">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="1418847151-20">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="1418847151-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">PongPID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="1418847151-21">(</span><span class="ss">tut20</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1418847151-22">[</span><span class="p" data-group-id="1418847151-22">]</span><span class="p" data-group-id="1418847151-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="1418847151-23">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut20</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1418847151-24">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">PongPID</span><span class="p" data-group-id="1418847151-24">]</span><span class="p" data-group-id="1418847151-23">)</span><span class="p">.</span></code></pre><pre><code class="text">(s1@bill)3&gt; tut20:start(s2@kosken).
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="7564624931-20">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="7564624931-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">PongPID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="7564624931-21">(</span><span class="ss">tut20</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7564624931-22">[</span><span class="p" data-group-id="7564624931-22">]</span><span class="p" data-group-id="7564624931-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="7564624931-23">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut20</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7564624931-24">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">PongPID</span><span class="p" data-group-id="7564624931-24">]</span><span class="p" data-group-id="7564624931-23">)</span><span class="p">.</span></code></pre><pre><code class="text">(s1@bill)3&gt; tut20:start(s2@kosken).
│ │ │ │  Pong received ping
│ │ │ │  &lt;3820.41.0&gt;
│ │ │ │  Ping received pong
│ │ │ │  Pong received ping
│ │ │ │  Ping received pong
│ │ │ │  Pong received ping
│ │ │ │  Ping received pong</code></pre><p>This is a slight modification of the ping pong program where both processes are
│ │ │ │  spawned from the same <code class="inline">start/1</code> function, and the &quot;ping&quot; process can be spawned
│ │ │ │  on a separate node. Notice the use of the <code class="inline">link</code> BIF. &quot;Ping&quot; calls
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#exit/1"><code class="inline">exit(ping)</code></a> when it finishes and this causes an exit signal to be
│ │ │ │  sent to &quot;pong&quot;, which also terminates.</p><p>It is possible to modify the default behaviour of a process so that it does not
│ │ │ │  get killed when it receives abnormal exit signals. Instead, all signals are
│ │ │ │  turned into normal messages of the format <code class="inline">{'EXIT',FromPID,Reason}</code> and added to
│ │ │ │ -the end of the receiving process' message queue. This behaviour is set by:</p><pre><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="8217620274-1">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="8217620274-1">)</span></code></pre><p>There are several other process flags, see <a href="../../../lib/../erts/doc/html/erlang.html#process_flag/2">erlang(3)</a>.
│ │ │ │ +the end of the receiving process' message queue. This behaviour is set by:</p><pre><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="1519376174-1">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="1519376174-1">)</span></code></pre><p>There are several other process flags, see <a href="../../../lib/../erts/doc/html/erlang.html#process_flag/2">erlang(3)</a>.
│ │ │ │  Changing the default behaviour of a process in this way is usually not done in
│ │ │ │  standard user programs, but is left to the supervisory programs in OTP. However,
│ │ │ │ -the ping pong program is modified to illustrate exit trapping.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3789237354-1">(</span><span class="ss">tut21</span><span class="p" data-group-id="3789237354-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +the ping pong program is modified to illustrate exit trapping.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1943582697-1">(</span><span class="ss">tut21</span><span class="p" data-group-id="1943582697-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3789237354-2">(</span><span class="p" data-group-id="3789237354-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3789237354-3">]</span><span class="p" data-group-id="3789237354-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1943582697-2">(</span><span class="p" data-group-id="1943582697-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1943582697-3">]</span><span class="p" data-group-id="1943582697-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="3789237354-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="3789237354-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">link</span><span class="p" data-group-id="3789237354-5">(</span><span class="n">Pong_Pid</span><span class="p" data-group-id="3789237354-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping1</span><span class="p" data-group-id="3789237354-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="3789237354-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="1943582697-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1943582697-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">link</span><span class="p" data-group-id="1943582697-5">(</span><span class="n">Pong_Pid</span><span class="p" data-group-id="1943582697-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping1</span><span class="p" data-group-id="1943582697-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1943582697-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping1</span><span class="p" data-group-id="3789237354-7">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="3789237354-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">exit</span><span class="p" data-group-id="3789237354-8">(</span><span class="ss">ping</span><span class="p" data-group-id="3789237354-8">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">ping1</span><span class="p" data-group-id="1943582697-7">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="1943582697-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">exit</span><span class="p" data-group-id="1943582697-8">(</span><span class="ss">ping</span><span class="p" data-group-id="1943582697-8">)</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping1</span><span class="p" data-group-id="3789237354-9">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="3789237354-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Pong_Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3789237354-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3789237354-11">(</span><span class="p" data-group-id="3789237354-11">)</span><span class="p" data-group-id="3789237354-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">ping1</span><span class="p" data-group-id="1943582697-9">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1943582697-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pong_Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1943582697-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1943582697-11">(</span><span class="p" data-group-id="1943582697-11">)</span><span class="p" data-group-id="1943582697-10">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3789237354-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3789237354-13">[</span><span class="p" data-group-id="3789237354-13">]</span><span class="p" data-group-id="3789237354-12">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1943582697-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1943582697-13">[</span><span class="p" data-group-id="1943582697-13">]</span><span class="p" data-group-id="1943582697-12">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping1</span><span class="p" data-group-id="3789237354-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="3789237354-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping1</span><span class="p" data-group-id="1943582697-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1943582697-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="3789237354-15">(</span><span class="p" data-group-id="3789237354-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="3789237354-16">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3789237354-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">pong1</span><span class="p" data-group-id="3789237354-17">(</span><span class="p" data-group-id="3789237354-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="1943582697-15">(</span><span class="p" data-group-id="1943582697-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="1943582697-16">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="1943582697-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">pong1</span><span class="p" data-group-id="1943582697-17">(</span><span class="p" data-group-id="1943582697-17">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">pong1</span><span class="p" data-group-id="3789237354-18">(</span><span class="p" data-group-id="3789237354-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">pong1</span><span class="p" data-group-id="1943582697-18">(</span><span class="p" data-group-id="1943582697-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3789237354-19">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="3789237354-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3789237354-20">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3789237354-21">[</span><span class="p" data-group-id="3789237354-21">]</span><span class="p" data-group-id="3789237354-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="1943582697-19">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="1943582697-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1943582697-20">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1943582697-21">[</span><span class="p" data-group-id="1943582697-21">]</span><span class="p" data-group-id="1943582697-20">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">pong1</span><span class="p" data-group-id="3789237354-22">(</span><span class="p" data-group-id="3789237354-22">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3789237354-23">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="3789237354-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3789237354-24">(</span><span class="s">&quot;pong exiting, got </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3789237354-25">[</span><span class="p" data-group-id="3789237354-26">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="3789237354-26">}</span><span class="p" data-group-id="3789237354-25">]</span><span class="p" data-group-id="3789237354-24">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">pong1</span><span class="p" data-group-id="1943582697-22">(</span><span class="p" data-group-id="1943582697-22">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="1943582697-23">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="1943582697-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1943582697-24">(</span><span class="s">&quot;pong exiting, got </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1943582697-25">[</span><span class="p" data-group-id="1943582697-26">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="1943582697-26">}</span><span class="p" data-group-id="1943582697-25">]</span><span class="p" data-group-id="1943582697-24">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="3789237354-27">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="3789237354-27">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">PongPID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="3789237354-28">(</span><span class="ss">tut21</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3789237354-29">[</span><span class="p" data-group-id="3789237354-29">]</span><span class="p" data-group-id="3789237354-28">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="3789237354-30">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut21</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3789237354-31">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">PongPID</span><span class="p" data-group-id="3789237354-31">]</span><span class="p" data-group-id="3789237354-30">)</span><span class="p">.</span></code></pre><pre><code class="text">(s1@bill)1&gt; tut21:start(s2@gollum).
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="1943582697-27">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="1943582697-27">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">PongPID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="1943582697-28">(</span><span class="ss">tut21</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1943582697-29">[</span><span class="p" data-group-id="1943582697-29">]</span><span class="p" data-group-id="1943582697-28">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="1943582697-30">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut21</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1943582697-31">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">PongPID</span><span class="p" data-group-id="1943582697-31">]</span><span class="p" data-group-id="1943582697-30">)</span><span class="p">.</span></code></pre><pre><code class="text">(s1@bill)1&gt; tut21:start(s2@gollum).
│ │ │ │  &lt;3820.39.0&gt;
│ │ │ │  Pong received ping
│ │ │ │  Ping received pong
│ │ │ │  Pong received ping
│ │ │ │  Ping received pong
│ │ │ │  Pong received ping
│ │ │ │  Ping received pong
│ │ │ │ @@ -256,135 +256,135 @@
│ │ │ │  </span><span class="c1">%%% Started: messenger:client(Server_Node, Name)</span><span class="w">
│ │ │ │  </span><span class="c1">%%% To client: logoff</span><span class="w">
│ │ │ │  </span><span class="c1">%%% To client: {message_to, ToName, Message}</span><span class="w">
│ │ │ │  </span><span class="c1">%%%</span><span class="w">
│ │ │ │  </span><span class="c1">%%% Configuration: change the server_node() function to return the</span><span class="w">
│ │ │ │  </span><span class="c1">%%% name of the node where the messenger server runs</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6248438468-1">(</span><span class="ss">messenger</span><span class="p" data-group-id="6248438468-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6248438468-2">(</span><span class="p" data-group-id="6248438468-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6248438468-3">]</span><span class="p" data-group-id="6248438468-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3294445017-1">(</span><span class="ss">messenger</span><span class="p" data-group-id="3294445017-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3294445017-2">(</span><span class="p" data-group-id="3294445017-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3294445017-3">]</span><span class="p" data-group-id="3294445017-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Change the function below to return the name of the node where the</span><span class="w">
│ │ │ │  </span><span class="c1">%%% messenger server runs</span><span class="w">
│ │ │ │ -</span><span class="nf">server_node</span><span class="p" data-group-id="6248438468-4">(</span><span class="p" data-group-id="6248438468-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_node</span><span class="p" data-group-id="3294445017-4">(</span><span class="p" data-group-id="3294445017-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">messenger@super</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% This is the server process for the &quot;messenger&quot;</span><span class="w">
│ │ │ │  </span><span class="c1">%%% the user list has the format [{ClientPid1, Name1},{ClientPid2, Name2},...]</span><span class="w">
│ │ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="6248438468-5">(</span><span class="p" data-group-id="6248438468-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="6248438468-6">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="6248438468-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">server</span><span class="p" data-group-id="6248438468-7">(</span><span class="p" data-group-id="6248438468-8">[</span><span class="p" data-group-id="6248438468-8">]</span><span class="p" data-group-id="6248438468-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="3294445017-5">(</span><span class="p" data-group-id="3294445017-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="3294445017-6">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3294445017-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">server</span><span class="p" data-group-id="3294445017-7">(</span><span class="p" data-group-id="3294445017-8">[</span><span class="p" data-group-id="3294445017-8">]</span><span class="p" data-group-id="3294445017-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="6248438468-9">(</span><span class="n">User_List</span><span class="p" data-group-id="6248438468-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="3294445017-9">(</span><span class="n">User_List</span><span class="p" data-group-id="3294445017-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6248438468-10">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6248438468-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="6248438468-11">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6248438468-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="6248438468-12">(</span><span class="n">New_User_List</span><span class="p" data-group-id="6248438468-12">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6248438468-13">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="6248438468-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="6248438468-14">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6248438468-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="6248438468-15">(</span><span class="n">New_User_List</span><span class="p" data-group-id="6248438468-15">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6248438468-16">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6248438468-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="6248438468-17">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6248438468-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6248438468-18">(</span><span class="s">&quot;list is now: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6248438468-19">[</span><span class="n">User_List</span><span class="p" data-group-id="6248438468-19">]</span><span class="p" data-group-id="6248438468-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="6248438468-20">(</span><span class="n">User_List</span><span class="p" data-group-id="6248438468-20">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3294445017-10">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3294445017-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="3294445017-11">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3294445017-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="3294445017-12">(</span><span class="n">New_User_List</span><span class="p" data-group-id="3294445017-12">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3294445017-13">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="3294445017-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="3294445017-14">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3294445017-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="3294445017-15">(</span><span class="n">New_User_List</span><span class="p" data-group-id="3294445017-15">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3294445017-16">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3294445017-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="3294445017-17">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3294445017-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3294445017-18">(</span><span class="s">&quot;list is now: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3294445017-19">[</span><span class="n">User_List</span><span class="p" data-group-id="3294445017-19">]</span><span class="p" data-group-id="3294445017-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="3294445017-20">(</span><span class="n">User_List</span><span class="p" data-group-id="3294445017-20">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Start the server</span><span class="w">
│ │ │ │ -</span><span class="nf">start_server</span><span class="p" data-group-id="6248438468-21">(</span><span class="p" data-group-id="6248438468-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="6248438468-22">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="6248438468-23">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6248438468-24">[</span><span class="p" data-group-id="6248438468-24">]</span><span class="p" data-group-id="6248438468-23">)</span><span class="p" data-group-id="6248438468-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_server</span><span class="p" data-group-id="3294445017-21">(</span><span class="p" data-group-id="3294445017-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="3294445017-22">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="3294445017-23">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3294445017-24">[</span><span class="p" data-group-id="3294445017-24">]</span><span class="p" data-group-id="3294445017-23">)</span><span class="p" data-group-id="3294445017-22">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server adds a new user to the user list</span><span class="w">
│ │ │ │ -</span><span class="nf">server_logon</span><span class="p" data-group-id="6248438468-25">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6248438468-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_logon</span><span class="p" data-group-id="3294445017-25">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3294445017-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% check if logged on anywhere else</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="6248438468-26">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6248438468-26">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="3294445017-26">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3294445017-26">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6248438468-27">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="6248438468-27">}</span><span class="p">,</span><span class="w">  </span><span class="c1">%reject logon</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3294445017-27">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="3294445017-27">}</span><span class="p">,</span><span class="w">  </span><span class="c1">%reject logon</span><span class="w">
│ │ │ │              </span><span class="n">User_List</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6248438468-28">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">logged_on</span><span class="p" data-group-id="6248438468-28">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">link</span><span class="p" data-group-id="6248438468-29">(</span><span class="n">From</span><span class="p" data-group-id="6248438468-29">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="6248438468-30">[</span><span class="p" data-group-id="6248438468-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6248438468-31">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6248438468-30">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3294445017-28">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">logged_on</span><span class="p" data-group-id="3294445017-28">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">link</span><span class="p" data-group-id="3294445017-29">(</span><span class="n">From</span><span class="p" data-group-id="3294445017-29">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="3294445017-30">[</span><span class="p" data-group-id="3294445017-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3294445017-31">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3294445017-30">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server deletes a user from the user list</span><span class="w">
│ │ │ │ -</span><span class="nf">server_logoff</span><span class="p" data-group-id="6248438468-32">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6248438468-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="6248438468-33">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6248438468-33">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">server_logoff</span><span class="p" data-group-id="3294445017-32">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3294445017-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="3294445017-33">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3294445017-33">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server transfers a message between users</span><span class="w">
│ │ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="6248438468-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6248438468-34">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="3294445017-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3294445017-34">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% check that the user is logged on and who he is</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="6248438468-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6248438468-35">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="3294445017-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3294445017-35">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6248438468-36">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="6248438468-36">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6248438468-37">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6248438468-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="6248438468-38">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6248438468-38">)</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3294445017-36">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="3294445017-36">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3294445017-37">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3294445017-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="3294445017-38">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3294445017-38">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% If the user exists, send the message</span><span class="w">
│ │ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="6248438468-39">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6248438468-39">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="3294445017-39">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3294445017-39">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Find the receiver and send the message</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="6248438468-40">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6248438468-40">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="3294445017-40">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3294445017-40">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6248438468-41">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="6248438468-41">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6248438468-42">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="6248438468-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6248438468-43">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6248438468-43">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6248438468-44">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="6248438468-44">}</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3294445017-41">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="3294445017-41">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3294445017-42">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="3294445017-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3294445017-43">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3294445017-43">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3294445017-44">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="3294445017-44">}</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% User Commands</span><span class="w">
│ │ │ │ -</span><span class="nf">logon</span><span class="p" data-group-id="6248438468-45">(</span><span class="n">Name</span><span class="p" data-group-id="6248438468-45">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="6248438468-46">(</span><span class="ss">mess_client</span><span class="p" data-group-id="6248438468-46">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">logon</span><span class="p" data-group-id="3294445017-45">(</span><span class="n">Name</span><span class="p" data-group-id="3294445017-45">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="3294445017-46">(</span><span class="ss">mess_client</span><span class="p" data-group-id="3294445017-46">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">register</span><span class="p" data-group-id="6248438468-47">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ │ -                     </span><span class="nf">spawn</span><span class="p" data-group-id="6248438468-48">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6248438468-49">[</span><span class="nf">server_node</span><span class="p" data-group-id="6248438468-50">(</span><span class="p" data-group-id="6248438468-50">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6248438468-49">]</span><span class="p" data-group-id="6248438468-48">)</span><span class="p" data-group-id="6248438468-47">)</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="nf">register</span><span class="p" data-group-id="3294445017-47">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ │ +                     </span><span class="nf">spawn</span><span class="p" data-group-id="3294445017-48">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3294445017-49">[</span><span class="nf">server_node</span><span class="p" data-group-id="3294445017-50">(</span><span class="p" data-group-id="3294445017-50">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3294445017-49">]</span><span class="p" data-group-id="3294445017-48">)</span><span class="p" data-group-id="3294445017-47">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">already_logged_on</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">logoff</span><span class="p" data-group-id="6248438468-51">(</span><span class="p" data-group-id="6248438468-51">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">logoff</span><span class="p" data-group-id="3294445017-51">(</span><span class="p" data-group-id="3294445017-51">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">logoff</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">message</span><span class="p" data-group-id="6248438468-52">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6248438468-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="6248438468-53">(</span><span class="ss">mess_client</span><span class="p" data-group-id="6248438468-53">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ │ +</span><span class="nf">message</span><span class="p" data-group-id="3294445017-52">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3294445017-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="3294445017-53">(</span><span class="ss">mess_client</span><span class="p" data-group-id="3294445017-53">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">not_logged_on</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6248438468-54">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6248438468-54">}</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3294445017-54">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3294445017-54">}</span><span class="p">,</span><span class="w">
│ │ │ │               </span><span class="ss">ok</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% The client process which runs on each user node</span><span class="w">
│ │ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="6248438468-55">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6248438468-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6248438468-56">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="6248438468-56">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6248438468-57">{</span><span class="nf">self</span><span class="p" data-group-id="6248438468-58">(</span><span class="p" data-group-id="6248438468-58">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6248438468-57">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">await_result</span><span class="p" data-group-id="6248438468-59">(</span><span class="p" data-group-id="6248438468-59">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="6248438468-60">(</span><span class="n">Server_Node</span><span class="p" data-group-id="6248438468-60">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="3294445017-55">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3294445017-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3294445017-56">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="3294445017-56">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3294445017-57">{</span><span class="nf">self</span><span class="p" data-group-id="3294445017-58">(</span><span class="p" data-group-id="3294445017-58">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3294445017-57">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">await_result</span><span class="p" data-group-id="3294445017-59">(</span><span class="p" data-group-id="3294445017-59">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="3294445017-60">(</span><span class="n">Server_Node</span><span class="p" data-group-id="3294445017-60">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="6248438468-61">(</span><span class="n">Server_Node</span><span class="p" data-group-id="6248438468-61">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="3294445017-61">(</span><span class="n">Server_Node</span><span class="p" data-group-id="3294445017-61">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">logoff</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="6248438468-62">(</span><span class="ss">normal</span><span class="p" data-group-id="6248438468-62">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6248438468-63">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6248438468-63">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="6248438468-64">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="6248438468-64">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6248438468-65">{</span><span class="nf">self</span><span class="p" data-group-id="6248438468-66">(</span><span class="p" data-group-id="6248438468-66">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6248438468-65">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">await_result</span><span class="p" data-group-id="6248438468-67">(</span><span class="p" data-group-id="6248438468-67">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6248438468-68">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6248438468-68">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6248438468-69">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6248438468-70">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6248438468-70">]</span><span class="p" data-group-id="6248438468-69">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="3294445017-62">(</span><span class="ss">normal</span><span class="p" data-group-id="3294445017-62">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3294445017-63">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3294445017-63">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="3294445017-64">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="3294445017-64">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3294445017-65">{</span><span class="nf">self</span><span class="p" data-group-id="3294445017-66">(</span><span class="p" data-group-id="3294445017-66">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3294445017-65">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">await_result</span><span class="p" data-group-id="3294445017-67">(</span><span class="p" data-group-id="3294445017-67">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3294445017-68">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3294445017-68">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3294445017-69">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3294445017-70">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3294445017-70">]</span><span class="p" data-group-id="3294445017-69">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="6248438468-71">(</span><span class="n">Server_Node</span><span class="p" data-group-id="6248438468-71">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="3294445017-71">(</span><span class="n">Server_Node</span><span class="p" data-group-id="3294445017-71">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% wait for a response from the server</span><span class="w">
│ │ │ │ -</span><span class="nf">await_result</span><span class="p" data-group-id="6248438468-72">(</span><span class="p" data-group-id="6248438468-72">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">await_result</span><span class="p" data-group-id="3294445017-72">(</span><span class="p" data-group-id="3294445017-72">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6248438468-73">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">Why</span><span class="p" data-group-id="6248438468-73">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Stop the client</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6248438468-74">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6248438468-75">[</span><span class="n">Why</span><span class="p" data-group-id="6248438468-75">]</span><span class="p" data-group-id="6248438468-74">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="6248438468-76">(</span><span class="ss">normal</span><span class="p" data-group-id="6248438468-76">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6248438468-77">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">What</span><span class="p" data-group-id="6248438468-77">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Normal response</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6248438468-78">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6248438468-79">[</span><span class="n">What</span><span class="p" data-group-id="6248438468-79">]</span><span class="p" data-group-id="6248438468-78">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3294445017-73">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">Why</span><span class="p" data-group-id="3294445017-73">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Stop the client</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3294445017-74">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3294445017-75">[</span><span class="n">Why</span><span class="p" data-group-id="3294445017-75">]</span><span class="p" data-group-id="3294445017-74">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="3294445017-76">(</span><span class="ss">normal</span><span class="p" data-group-id="3294445017-76">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3294445017-77">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">What</span><span class="p" data-group-id="3294445017-77">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Normal response</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3294445017-78">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3294445017-79">[</span><span class="n">What</span><span class="p" data-group-id="3294445017-79">]</span><span class="p" data-group-id="3294445017-78">)</span><span class="w">
│ │ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6248438468-80">(</span><span class="s">&quot;No response from server</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6248438468-81">[</span><span class="p" data-group-id="6248438468-81">]</span><span class="p" data-group-id="6248438468-80">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="6248438468-82">(</span><span class="ss">timeout</span><span class="p" data-group-id="6248438468-82">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3294445017-80">(</span><span class="s">&quot;No response from server</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3294445017-81">[</span><span class="p" data-group-id="3294445017-81">]</span><span class="p" data-group-id="3294445017-80">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="3294445017-82">(</span><span class="ss">timeout</span><span class="p" data-group-id="3294445017-82">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The following changes are added:</p><p>The messenger server traps exits. If it receives an exit signal,
│ │ │ │  <code class="inline">{'EXIT',From,Reason}</code>, this means that a client process has terminated or is
│ │ │ │  unreachable for one of the following reasons:</p><ul><li>The user has logged off (the &quot;logoff&quot; message is removed).</li><li>The network connection to the client is broken.</li><li>The node on which the client process resides has gone down.</li><li>The client process has done some illegal operation.</li></ul><p>If an exit signal is received as above, the tuple <code class="inline">{From,Name}</code> is deleted from
│ │ │ │  the server's <code class="inline">User_List</code> using the <code class="inline">server_logoff</code> function. If the node on which
│ │ │ │  the server runs goes down, an exit signal (automatically generated by the
│ │ │ │  system) is sent to all of the client processes:
│ │ │ │  <code class="inline">{'EXIT',MessengerPID,noconnection}</code> causing all the client processes to
│ │ │ ├── OEBPS/release_structure.xhtml
│ │ │ │ @@ -41,37 +41,37 @@
│ │ │ │    <a href="#release-resource-file" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Release Resource File</span>
│ │ │ │  </h2>
│ │ │ │  <p>To define a release, create a <em>release resource file</em>, or in short a <code class="inline">.rel</code>
│ │ │ │  file. In the file, specify the name and version of the release, which ERTS
│ │ │ │ -version it is based on, and which applications it consists of:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2803806640-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2803806640-2">{</span><span class="n">Name</span><span class="p">,</span><span class="n">Vsn</span><span class="p" data-group-id="2803806640-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2803806640-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">EVsn</span><span class="p" data-group-id="2803806640-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2803806640-4">[</span><span class="p" data-group-id="2803806640-5">{</span><span class="n">Application1</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsn1</span><span class="p" data-group-id="2803806640-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +version it is based on, and which applications it consists of:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0640546193-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0640546193-2">{</span><span class="n">Name</span><span class="p">,</span><span class="n">Vsn</span><span class="p" data-group-id="0640546193-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0640546193-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">EVsn</span><span class="p" data-group-id="0640546193-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0640546193-4">[</span><span class="p" data-group-id="0640546193-5">{</span><span class="n">Application1</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsn1</span><span class="p" data-group-id="0640546193-5">}</span><span class="p">,</span><span class="w">
│ │ │ │     </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2803806640-6">{</span><span class="n">ApplicationN</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsnN</span><span class="p" data-group-id="2803806640-6">}</span><span class="p" data-group-id="2803806640-4">]</span><span class="p" data-group-id="2803806640-1">}</span><span class="p">.</span></code></pre><p><code class="inline">Name</code>, <code class="inline">Vsn</code>, <code class="inline">EVsn</code>, and <code class="inline">AppVsn</code> are strings.</p><p>The file must be named <code class="inline">Rel.rel</code>, where <code class="inline">Rel</code> is a unique name.</p><p>Each <code class="inline">Application</code> (atom) and <code class="inline">AppVsn</code> is the name and version of an application
│ │ │ │ +  </span><span class="p" data-group-id="0640546193-6">{</span><span class="n">ApplicationN</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsnN</span><span class="p" data-group-id="0640546193-6">}</span><span class="p" data-group-id="0640546193-4">]</span><span class="p" data-group-id="0640546193-1">}</span><span class="p">.</span></code></pre><p><code class="inline">Name</code>, <code class="inline">Vsn</code>, <code class="inline">EVsn</code>, and <code class="inline">AppVsn</code> are strings.</p><p>The file must be named <code class="inline">Rel.rel</code>, where <code class="inline">Rel</code> is a unique name.</p><p>Each <code class="inline">Application</code> (atom) and <code class="inline">AppVsn</code> is the name and version of an application
│ │ │ │  included in the release. The minimal release based on Erlang/OTP consists of the
│ │ │ │  Kernel and STDLIB applications, so these applications must be included in the
│ │ │ │  list.</p><p>If the release is to be upgraded, it must also include the SASL application.</p><p><a href="" id="ch_rel"></a></p><p>Here is an example showing the <code class="inline">.app</code> file for a release of <code class="inline">ch_app</code> from
│ │ │ │ -the <a href="applications.xhtml#ch_app">Applications</a> section:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6667851050-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="6667851050-2">[</span><span class="p" data-group-id="6667851050-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="6667851050-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6667851050-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="6667851050-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6667851050-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6667851050-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="6667851050-6">]</span><span class="p" data-group-id="6667851050-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6667851050-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6667851050-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="6667851050-8">]</span><span class="p" data-group-id="6667851050-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6667851050-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6667851050-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="6667851050-10">]</span><span class="p" data-group-id="6667851050-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6667851050-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6667851050-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="6667851050-13">[</span><span class="p" data-group-id="6667851050-13">]</span><span class="p" data-group-id="6667851050-12">}</span><span class="p" data-group-id="6667851050-11">}</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="6667851050-2">]</span><span class="p" data-group-id="6667851050-1">}</span><span class="p">.</span></code></pre><p>The <code class="inline">.rel</code> file must also contain <code class="inline">kernel</code>, <code class="inline">stdlib</code>, and <code class="inline">sasl</code>, as these
│ │ │ │ -applications are required by <code class="inline">ch_app</code>. The file is called <code class="inline">ch_rel-1.rel</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0244181843-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="0244181843-2">{</span><span class="s">&quot;ch_rel&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;A&quot;</span><span class="p" data-group-id="0244181843-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="0244181843-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;14.2.5&quot;</span><span class="p" data-group-id="0244181843-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="0244181843-4">[</span><span class="p" data-group-id="0244181843-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;9.2.4&quot;</span><span class="p" data-group-id="0244181843-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="0244181843-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.2.3&quot;</span><span class="p" data-group-id="0244181843-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="0244181843-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;4.2.1&quot;</span><span class="p" data-group-id="0244181843-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="0244181843-8">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="0244181843-8">}</span><span class="p" data-group-id="0244181843-4">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0244181843-1">}</span><span class="p">.</span></code></pre><p><a href="" id="boot"></a></p><h2 id="generating-boot-scripts" class="section-heading">
│ │ │ │ +the <a href="applications.xhtml#ch_app">Applications</a> section:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4058934916-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="4058934916-2">[</span><span class="p" data-group-id="4058934916-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="4058934916-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4058934916-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="4058934916-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4058934916-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4058934916-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="4058934916-6">]</span><span class="p" data-group-id="4058934916-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4058934916-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4058934916-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="4058934916-8">]</span><span class="p" data-group-id="4058934916-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4058934916-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4058934916-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="4058934916-10">]</span><span class="p" data-group-id="4058934916-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4058934916-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4058934916-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="4058934916-13">[</span><span class="p" data-group-id="4058934916-13">]</span><span class="p" data-group-id="4058934916-12">}</span><span class="p" data-group-id="4058934916-11">}</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="4058934916-2">]</span><span class="p" data-group-id="4058934916-1">}</span><span class="p">.</span></code></pre><p>The <code class="inline">.rel</code> file must also contain <code class="inline">kernel</code>, <code class="inline">stdlib</code>, and <code class="inline">sasl</code>, as these
│ │ │ │ +applications are required by <code class="inline">ch_app</code>. The file is called <code class="inline">ch_rel-1.rel</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1973457920-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="1973457920-2">{</span><span class="s">&quot;ch_rel&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;A&quot;</span><span class="p" data-group-id="1973457920-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="1973457920-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;14.2.5&quot;</span><span class="p" data-group-id="1973457920-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="1973457920-4">[</span><span class="p" data-group-id="1973457920-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;9.2.4&quot;</span><span class="p" data-group-id="1973457920-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="1973457920-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.2.3&quot;</span><span class="p" data-group-id="1973457920-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="1973457920-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;4.2.1&quot;</span><span class="p" data-group-id="1973457920-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="1973457920-8">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="1973457920-8">}</span><span class="p" data-group-id="1973457920-4">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1973457920-1">}</span><span class="p">.</span></code></pre><p><a href="" id="boot"></a></p><h2 id="generating-boot-scripts" class="section-heading">
│ │ │ │    <a href="#generating-boot-scripts" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Generating Boot Scripts</span>
│ │ │ │  </h2>
│ │ │ │  <p><a href="../../../lib/sasl/doc/html/systools.html"><code class="inline">systools</code></a> in the SASL application includes tools to build and check
│ │ │ │  releases. The functions read the <code class="inline">.rel</code> and <code class="inline">.app</code> files and perform
│ │ │ │ @@ -95,17 +95,17 @@
│ │ │ │    <a href="#creating-a-release-package" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Creating a Release Package</span>
│ │ │ │  </h2>
│ │ │ │  <p>The <a href="../../../lib/sasl/doc/html/systools.html#make_tar/2"><code class="inline">systools:make_tar/1,2</code></a> function takes a
│ │ │ │  <code class="inline">.rel</code> file as input and creates a zipped tar file with the code for
│ │ │ │ -the specified applications, a <em>release package</em>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="2470219041-1">(</span><span class="s">&quot;ch_rel-1&quot;</span><span class="p" data-group-id="2470219041-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +the specified applications, a <em>release package</em>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="5291634478-1">(</span><span class="s">&quot;ch_rel-1&quot;</span><span class="p" data-group-id="5291634478-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="2470219041-2">(</span><span class="s">&quot;ch_rel-1&quot;</span><span class="p" data-group-id="2470219041-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="5291634478-2">(</span><span class="s">&quot;ch_rel-1&quot;</span><span class="p" data-group-id="5291634478-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>The release package by default contains:</p><ul><li>The <code class="inline">.app</code> files</li><li>The <code class="inline">.rel</code> file</li><li>The object code for all applications, structured according to the
│ │ │ │  <a href="applications.xhtml#app_dir">application directory structure</a></li><li>The binary boot script renamed to <code class="inline">start.boot</code></li></ul><pre><code class="text">% tar tf ch_rel-1.tar
│ │ │ │  lib/kernel-9.2.4/ebin/kernel.app
│ │ │ │  lib/kernel-9.2.4/ebin/application.beam
│ │ │ │  ...
│ │ │ │  lib/stdlib-5.2.3/ebin/stdlib.app
│ │ │ │  lib/stdlib-5.2.3/ebin/argparse.beam
│ │ │ ├── OEBPS/release_handling.xhtml
│ │ │ │ @@ -128,38 +128,38 @@
│ │ │ │    <span class="text">update</span>
│ │ │ │  </h3>
│ │ │ │  <p>If a more complex change has been made, for example, a change to the format of
│ │ │ │  the internal state of a <a href="../../../lib/stdlib/doc/html/gen_server.html"><code class="inline">gen_server</code></a>, simple code replacement is not sufficient.
│ │ │ │  Instead, it is necessary to:</p><ul><li>Suspend the processes using the module (to avoid that they try to handle any
│ │ │ │  requests before the code replacement is completed).</li><li>Ask them to transform the internal state format and switch to the new version
│ │ │ │  of the module.</li><li>Remove the old version.</li><li>Resume the processes.</li></ul><p>This is called <em>synchronized code replacement</em> and for this the following
│ │ │ │ -instructions are used:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9747137435-1">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9747137435-2">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="9747137435-2">}</span><span class="p" data-group-id="9747137435-1">}</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9747137435-3">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="9747137435-3">}</span></code></pre><p><code class="inline">update</code> with argument <code class="inline">{advanced,Extra}</code> is used when changing the internal
│ │ │ │ +instructions are used:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6038376113-1">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6038376113-2">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="6038376113-2">}</span><span class="p" data-group-id="6038376113-1">}</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6038376113-3">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="6038376113-3">}</span></code></pre><p><code class="inline">update</code> with argument <code class="inline">{advanced,Extra}</code> is used when changing the internal
│ │ │ │  state of a behaviour as described above. It causes behaviour processes to call
│ │ │ │  the callback function <code class="inline">code_change/3</code>, passing the term <code class="inline">Extra</code> and some other
│ │ │ │  information as arguments. See the manual pages for the respective behaviours and
│ │ │ │  <a href="appup_cookbook.xhtml#int_state">Appup Cookbook</a>.</p><p><code class="inline">update</code> with argument <code class="inline">supervisor</code> is used when changing the start
│ │ │ │  specification of a supervisor. See <a href="appup_cookbook.xhtml#sup">Appup Cookbook</a>.</p><p>When a module is to be updated, the release handler finds which processes that
│ │ │ │  are <em>using</em> the module by traversing the supervision tree of each running
│ │ │ │ -application and checking all the child specifications:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8964209673-1">{</span><span class="n">Id</span><span class="p">,</span><span class="w"> </span><span class="n">StartFunc</span><span class="p">,</span><span class="w"> </span><span class="n">Restart</span><span class="p">,</span><span class="w"> </span><span class="n">Shutdown</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">Modules</span><span class="p" data-group-id="8964209673-1">}</span></code></pre><p>A process uses a module if the name is listed in <code class="inline">Modules</code> in the child
│ │ │ │ +application and checking all the child specifications:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4421096806-1">{</span><span class="n">Id</span><span class="p">,</span><span class="w"> </span><span class="n">StartFunc</span><span class="p">,</span><span class="w"> </span><span class="n">Restart</span><span class="p">,</span><span class="w"> </span><span class="n">Shutdown</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">Modules</span><span class="p" data-group-id="4421096806-1">}</span></code></pre><p>A process uses a module if the name is listed in <code class="inline">Modules</code> in the child
│ │ │ │  specification for the process.</p><p>If <code class="inline">Modules=dynamic</code>, which is the case for event managers, the event manager
│ │ │ │  process informs the release handler about the list of currently installed event
│ │ │ │  handlers (<code class="inline">gen_event</code>), and it is checked if the module name is in this list
│ │ │ │  instead.</p><p>The release handler suspends, asks for code change, and resumes processes by
│ │ │ │  calling the functions <code class="inline">sys:suspend/1,2</code>, <code class="inline">sys:change_code/4,5</code>, and
│ │ │ │  <code class="inline">sys:resume/1,2</code>, respectively.</p><h3 id="add_module-and-delete_module" class="section-heading">
│ │ │ │    <a href="#add_module-and-delete_module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">add_module and delete_module</span>
│ │ │ │  </h3>
│ │ │ │ -<p>If a new module is introduced, the following instruction is used:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5372899023-1">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="5372899023-1">}</span></code></pre><p>This instruction loads module <code class="inline">Module</code>. When running Erlang in
│ │ │ │ +<p>If a new module is introduced, the following instruction is used:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7822817405-1">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="7822817405-1">}</span></code></pre><p>This instruction loads module <code class="inline">Module</code>. When running Erlang in
│ │ │ │  embedded mode it is necessary to use this instruction. It is not
│ │ │ │  strictly required when running Erlang in interactive mode, since the
│ │ │ │ -code server automatically searches for and loads unloaded modules.</p><p>The opposite of <code class="inline">add_module</code> is <code class="inline">delete_module</code>, which unloads a module:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1202454546-1">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="1202454546-1">}</span></code></pre><p>Any process, in any application, with <code class="inline">Module</code> as residence module, is
│ │ │ │ +code server automatically searches for and loads unloaded modules.</p><p>The opposite of <code class="inline">add_module</code> is <code class="inline">delete_module</code>, which unloads a module:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0800305042-1">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="0800305042-1">}</span></code></pre><p>Any process, in any application, with <code class="inline">Module</code> as residence module, is
│ │ │ │  killed when the instruction is evaluated. Therefore, the user must
│ │ │ │  ensure that all such processes are terminated before deleting module
│ │ │ │  <code class="inline">Module</code> to avoid a situation with failing supervisor restarts.</p><h3 id="application-instructions" class="section-heading">
│ │ │ │    <a href="#application-instructions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Application Instructions</span>
│ │ │ │ @@ -246,60 +246,60 @@
│ │ │ │  <code class="inline">.app</code> file.</li><li>Each <code class="inline">UpFromVsn</code> is a previous version of the application to upgrade from.</li><li>Each <code class="inline">DownToVsn</code> is a previous version of the application to downgrade to.</li><li>Each <code class="inline">Instructions</code> is a list of release handling instructions.</li></ul><p><code class="inline">UpFromVsn</code> and <code class="inline">DownToVsn</code> can also be specified as regular expressions. For
│ │ │ │  more information about the syntax and contents of the <code class="inline">.appup</code> file, see
│ │ │ │  <a href="../../../lib/sasl/doc/html/appup.xhtml"><code class="inline">appup</code></a> in SASL.</p><p><a href="appup_cookbook.xhtml">Appup Cookbook</a> includes examples of <code class="inline">.appup</code> files for
│ │ │ │  typical upgrade/downgrade cases.</p><p><em>Example:</em> Consider the release <code class="inline">ch_rel-1</code> from
│ │ │ │  <a href="release_structure.xhtml#ch_rel">Releases</a>. Assume you want to add a function
│ │ │ │  <code class="inline">available/0</code> to server <code class="inline">ch3</code>, which returns the number of available channels
│ │ │ │  (when trying out the example, make the change in a copy of the original
│ │ │ │ -directory, to ensure that the first version is still available):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2448248279-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="2448248279-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="2448248279-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="2448248279-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +directory, to ensure that the first version is still available):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1781084415-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="1781084415-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="1781084415-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="1781084415-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2448248279-3">(</span><span class="p" data-group-id="2448248279-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2448248279-4">]</span><span class="p" data-group-id="2448248279-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2448248279-5">(</span><span class="p" data-group-id="2448248279-6">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2448248279-6">]</span><span class="p" data-group-id="2448248279-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2448248279-7">(</span><span class="p" data-group-id="2448248279-8">[</span><span class="ss">available</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2448248279-8">]</span><span class="p" data-group-id="2448248279-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2448248279-9">(</span><span class="p" data-group-id="2448248279-10">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2448248279-10">]</span><span class="p" data-group-id="2448248279-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1781084415-3">(</span><span class="p" data-group-id="1781084415-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1781084415-4">]</span><span class="p" data-group-id="1781084415-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1781084415-5">(</span><span class="p" data-group-id="1781084415-6">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1781084415-6">]</span><span class="p" data-group-id="1781084415-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1781084415-7">(</span><span class="p" data-group-id="1781084415-8">[</span><span class="ss">available</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1781084415-8">]</span><span class="p" data-group-id="1781084415-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1781084415-9">(</span><span class="p" data-group-id="1781084415-10">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1781084415-10">]</span><span class="p" data-group-id="1781084415-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="2448248279-11">(</span><span class="p" data-group-id="2448248279-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="2448248279-12">(</span><span class="p" data-group-id="2448248279-13">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="2448248279-13">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2448248279-14">[</span><span class="p" data-group-id="2448248279-14">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2448248279-15">[</span><span class="p" data-group-id="2448248279-15">]</span><span class="p" data-group-id="2448248279-12">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="1781084415-11">(</span><span class="p" data-group-id="1781084415-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="1781084415-12">(</span><span class="p" data-group-id="1781084415-13">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="1781084415-13">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1781084415-14">[</span><span class="p" data-group-id="1781084415-14">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1781084415-15">[</span><span class="p" data-group-id="1781084415-15">]</span><span class="p" data-group-id="1781084415-12">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="2448248279-16">(</span><span class="p" data-group-id="2448248279-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="2448248279-17">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="2448248279-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="1781084415-16">(</span><span class="p" data-group-id="1781084415-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="1781084415-17">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="1781084415-17">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="2448248279-18">(</span><span class="n">Ch</span><span class="p" data-group-id="2448248279-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="2448248279-19">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2448248279-20">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2448248279-20">}</span><span class="p" data-group-id="2448248279-19">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="1781084415-18">(</span><span class="n">Ch</span><span class="p" data-group-id="1781084415-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="1781084415-19">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1781084415-20">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1781084415-20">}</span><span class="p" data-group-id="1781084415-19">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">available</span><span class="p" data-group-id="2448248279-21">(</span><span class="p" data-group-id="2448248279-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="2448248279-22">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">available</span><span class="p" data-group-id="2448248279-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">available</span><span class="p" data-group-id="1781084415-21">(</span><span class="p" data-group-id="1781084415-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="1781084415-22">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">available</span><span class="p" data-group-id="1781084415-22">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="2448248279-23">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="2448248279-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2448248279-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="2448248279-25">(</span><span class="p" data-group-id="2448248279-25">)</span><span class="p" data-group-id="2448248279-24">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="1781084415-23">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="1781084415-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1781084415-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="1781084415-25">(</span><span class="p" data-group-id="1781084415-25">)</span><span class="p" data-group-id="1781084415-24">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="2448248279-26">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2448248279-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2448248279-27">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="2448248279-27">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="2448248279-28">(</span><span class="n">Chs</span><span class="p" data-group-id="2448248279-28">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2448248279-29">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="2448248279-29">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="2448248279-30">(</span><span class="ss">available</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2448248279-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">available</span><span class="p" data-group-id="2448248279-31">(</span><span class="n">Chs</span><span class="p" data-group-id="2448248279-31">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2448248279-32">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2448248279-32">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="1781084415-26">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1781084415-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1781084415-27">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="1781084415-27">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="1781084415-28">(</span><span class="n">Chs</span><span class="p" data-group-id="1781084415-28">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1781084415-29">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="1781084415-29">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="1781084415-30">(</span><span class="ss">available</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1781084415-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">available</span><span class="p" data-group-id="1781084415-31">(</span><span class="n">Chs</span><span class="p" data-group-id="1781084415-31">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1781084415-32">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1781084415-32">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="2448248279-33">(</span><span class="p" data-group-id="2448248279-34">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2448248279-34">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2448248279-33">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="2448248279-35">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2448248279-35">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2448248279-36">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="2448248279-36">}</span><span class="p">.</span></code></pre><p>A new version of the <code class="inline">ch_app.app</code> file must now be created, where the version is
│ │ │ │ -updated:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0246366318-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="0246366318-2">[</span><span class="p" data-group-id="0246366318-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="0246366318-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="0246366318-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="0246366318-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="0246366318-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0246366318-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="0246366318-6">]</span><span class="p" data-group-id="0246366318-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="0246366318-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0246366318-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="0246366318-8">]</span><span class="p" data-group-id="0246366318-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="0246366318-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0246366318-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="0246366318-10">]</span><span class="p" data-group-id="0246366318-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="0246366318-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0246366318-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="0246366318-13">[</span><span class="p" data-group-id="0246366318-13">]</span><span class="p" data-group-id="0246366318-12">}</span><span class="p" data-group-id="0246366318-11">}</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="0246366318-2">]</span><span class="p" data-group-id="0246366318-1">}</span><span class="p">.</span></code></pre><p>To upgrade <code class="inline">ch_app</code> from <code class="inline">&quot;1&quot;</code> to <code class="inline">&quot;2&quot;</code> (and to downgrade from <code class="inline">&quot;2&quot;</code> to <code class="inline">&quot;1&quot;</code>),
│ │ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="1781084415-33">(</span><span class="p" data-group-id="1781084415-34">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1781084415-34">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1781084415-33">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="1781084415-35">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1781084415-35">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1781084415-36">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="1781084415-36">}</span><span class="p">.</span></code></pre><p>A new version of the <code class="inline">ch_app.app</code> file must now be created, where the version is
│ │ │ │ +updated:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4720736490-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="4720736490-2">[</span><span class="p" data-group-id="4720736490-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="4720736490-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4720736490-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="4720736490-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4720736490-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4720736490-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="4720736490-6">]</span><span class="p" data-group-id="4720736490-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4720736490-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4720736490-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="4720736490-8">]</span><span class="p" data-group-id="4720736490-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4720736490-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4720736490-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="4720736490-10">]</span><span class="p" data-group-id="4720736490-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4720736490-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4720736490-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="4720736490-13">[</span><span class="p" data-group-id="4720736490-13">]</span><span class="p" data-group-id="4720736490-12">}</span><span class="p" data-group-id="4720736490-11">}</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="4720736490-2">]</span><span class="p" data-group-id="4720736490-1">}</span><span class="p">.</span></code></pre><p>To upgrade <code class="inline">ch_app</code> from <code class="inline">&quot;1&quot;</code> to <code class="inline">&quot;2&quot;</code> (and to downgrade from <code class="inline">&quot;2&quot;</code> to <code class="inline">&quot;1&quot;</code>),
│ │ │ │  you only need to load the new (old) version of the <code class="inline">ch3</code> callback module. Create
│ │ │ │ -the application upgrade file <code class="inline">ch_app.appup</code> in the <code class="inline">ebin</code> directory:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4717266064-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4717266064-2">[</span><span class="p" data-group-id="4717266064-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4717266064-4">[</span><span class="p" data-group-id="4717266064-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="4717266064-5">}</span><span class="p" data-group-id="4717266064-4">]</span><span class="p" data-group-id="4717266064-3">}</span><span class="p" data-group-id="4717266064-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4717266064-6">[</span><span class="p" data-group-id="4717266064-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4717266064-8">[</span><span class="p" data-group-id="4717266064-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="4717266064-9">}</span><span class="p" data-group-id="4717266064-8">]</span><span class="p" data-group-id="4717266064-7">}</span><span class="p" data-group-id="4717266064-6">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4717266064-1">}</span><span class="p">.</span></code></pre><p><a href="" id="relup"></a></p><h2 id="release-upgrade-file" class="section-heading">
│ │ │ │ +the application upgrade file <code class="inline">ch_app.appup</code> in the <code class="inline">ebin</code> directory:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6735741471-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6735741471-2">[</span><span class="p" data-group-id="6735741471-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6735741471-4">[</span><span class="p" data-group-id="6735741471-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="6735741471-5">}</span><span class="p" data-group-id="6735741471-4">]</span><span class="p" data-group-id="6735741471-3">}</span><span class="p" data-group-id="6735741471-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6735741471-6">[</span><span class="p" data-group-id="6735741471-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6735741471-8">[</span><span class="p" data-group-id="6735741471-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="6735741471-9">}</span><span class="p" data-group-id="6735741471-8">]</span><span class="p" data-group-id="6735741471-7">}</span><span class="p" data-group-id="6735741471-6">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6735741471-1">}</span><span class="p">.</span></code></pre><p><a href="" id="relup"></a></p><h2 id="release-upgrade-file" class="section-heading">
│ │ │ │    <a href="#release-upgrade-file" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Release Upgrade File</span>
│ │ │ │  </h2>
│ │ │ │  <p>To define how to upgrade/downgrade between the new version and previous versions
│ │ │ │  of a release, a <em>release upgrade file</em>, or in short <code class="inline">.relup</code> file, is to be
│ │ │ │ @@ -310,22 +310,22 @@
│ │ │ │  are to be added and deleted, and which applications that must be upgraded and/or
│ │ │ │  downgraded. The instructions for this are fetched from the <code class="inline">.appup</code> files and
│ │ │ │  transformed into a single list of low-level instructions in the right order.</p><p>If the <code class="inline">relup</code> file is relatively simple, it can be created manually. It is only
│ │ │ │  to contain low-level instructions.</p><p>For details about the syntax and contents of the release upgrade file, see
│ │ │ │  <a href="../../../lib/sasl/doc/html/relup.xhtml"><code class="inline">relup</code></a> in SASL.</p><p><em>Example, continued from the previous section:</em> You have a new version &quot;2&quot; of
│ │ │ │  <code class="inline">ch_app</code> and an <code class="inline">.appup</code> file. A new version of the <code class="inline">.rel</code> file is also needed.
│ │ │ │  This time the file is called <code class="inline">ch_rel-2.rel</code> and the release version string is
│ │ │ │ -changed from &quot;A&quot; to &quot;B&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1625979602-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1625979602-2">{</span><span class="s">&quot;ch_rel&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="1625979602-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1625979602-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;14.2.5&quot;</span><span class="p" data-group-id="1625979602-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1625979602-4">[</span><span class="p" data-group-id="1625979602-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;9.2.4&quot;</span><span class="p" data-group-id="1625979602-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="1625979602-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.2.3&quot;</span><span class="p" data-group-id="1625979602-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="1625979602-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;4.2.1&quot;</span><span class="p" data-group-id="1625979602-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="1625979602-8">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="1625979602-8">}</span><span class="p" data-group-id="1625979602-4">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1625979602-1">}</span><span class="p">.</span></code></pre><p>Now the <code class="inline">relup</code> file can be generated:</p><pre><code class="text">1&gt; systools:make_relup(&quot;ch_rel-2&quot;, [&quot;ch_rel-1&quot;], [&quot;ch_rel-1&quot;]).
│ │ │ │ +changed from &quot;A&quot; to &quot;B&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0057796994-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0057796994-2">{</span><span class="s">&quot;ch_rel&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="0057796994-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0057796994-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;14.2.5&quot;</span><span class="p" data-group-id="0057796994-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0057796994-4">[</span><span class="p" data-group-id="0057796994-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;9.2.4&quot;</span><span class="p" data-group-id="0057796994-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0057796994-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.2.3&quot;</span><span class="p" data-group-id="0057796994-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0057796994-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;4.2.1&quot;</span><span class="p" data-group-id="0057796994-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0057796994-8">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="0057796994-8">}</span><span class="p" data-group-id="0057796994-4">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0057796994-1">}</span><span class="p">.</span></code></pre><p>Now the <code class="inline">relup</code> file can be generated:</p><pre><code class="text">1&gt; systools:make_relup(&quot;ch_rel-2&quot;, [&quot;ch_rel-1&quot;], [&quot;ch_rel-1&quot;]).
│ │ │ │  ok</code></pre><p>This generates a <code class="inline">relup</code> file with instructions for how to upgrade from version
│ │ │ │  &quot;A&quot; (&quot;ch_rel-1&quot;) to version &quot;B&quot; (&quot;ch_rel-2&quot;) and how to downgrade from version
│ │ │ │  &quot;B&quot; to version &quot;A&quot;.</p><p>Both the old and new versions of the <code class="inline">.app</code> and <code class="inline">.rel</code> files must be in the code
│ │ │ │  path, as well as the <code class="inline">.appup</code> and (new) <code class="inline">.beam</code> files. The code path can be
│ │ │ │  extended by using the option <code class="inline">path</code>:</p><pre><code class="text">1&gt; systools:make_relup(&quot;ch_rel-2&quot;, [&quot;ch_rel-1&quot;], [&quot;ch_rel-1&quot;],
│ │ │ │  [{path,[&quot;../ch_rel-1&quot;,
│ │ │ │  &quot;../ch_rel-1/lib/ch_app-1/ebin&quot;]}]).
│ │ │ │ @@ -338,25 +338,25 @@
│ │ │ │  <p>When you have made a new version of a release, a release package can be created
│ │ │ │  with this new version and transferred to the target environment.</p><p>To install the new version of the release in runtime, the <em>release
│ │ │ │  handler</em> is used. This is a process belonging to the SASL application,
│ │ │ │  which handles unpacking, installation, and removal of release
│ │ │ │  packages. The <a href="../../../lib/sasl/doc/html/release_handler.html"><code class="inline">release_handler</code></a> module communicates with this process.</p><p>Assuming there is an operational target system with installation root directory
│ │ │ │  <code class="inline">$ROOT</code>, the release package with the new version of the release is to be copied
│ │ │ │  to <code class="inline">$ROOT/releases</code>.</p><p>First, <em>unpack</em> the release package. The files are then extracted from the
│ │ │ │ -package:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">unpack_release</span><span class="p" data-group-id="4643319022-1">(</span><span class="n">ReleaseName</span><span class="p" data-group-id="4643319022-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4643319022-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Vsn</span><span class="p" data-group-id="4643319022-2">}</span></code></pre><ul><li><code class="inline">ReleaseName</code> is the name of the release package except the <code class="inline">.tar.gz</code>
│ │ │ │ +package:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">unpack_release</span><span class="p" data-group-id="7076567271-1">(</span><span class="n">ReleaseName</span><span class="p" data-group-id="7076567271-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7076567271-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Vsn</span><span class="p" data-group-id="7076567271-2">}</span></code></pre><ul><li><code class="inline">ReleaseName</code> is the name of the release package except the <code class="inline">.tar.gz</code>
│ │ │ │  extension.</li><li><code class="inline">Vsn</code> is the version of the unpacked release, as defined in its <code class="inline">.rel</code> file.</li></ul><p>A directory <code class="inline">$ROOT/lib/releases/Vsn</code> is created, where the <code class="inline">.rel</code> file, the boot
│ │ │ │  script <code class="inline">start.boot</code>, the system configuration file <code class="inline">sys.config</code>, and <code class="inline">relup</code> are
│ │ │ │  placed. For applications with new version numbers, the application directories
│ │ │ │  are placed under <code class="inline">$ROOT/lib</code>. Unchanged applications are not affected.</p><p>An unpacked release can be <em>installed</em>. The release handler then evaluates the
│ │ │ │ -instructions in <code class="inline">relup</code>, step by step:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="8462950729-1">(</span><span class="n">Vsn</span><span class="p" data-group-id="8462950729-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8462950729-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FromVsn</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8462950729-3">[</span><span class="p" data-group-id="8462950729-3">]</span><span class="p" data-group-id="8462950729-2">}</span></code></pre><p>If an error occurs during the installation, the system is rebooted using the old
│ │ │ │ +instructions in <code class="inline">relup</code>, step by step:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="3576832412-1">(</span><span class="n">Vsn</span><span class="p" data-group-id="3576832412-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3576832412-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FromVsn</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3576832412-3">[</span><span class="p" data-group-id="3576832412-3">]</span><span class="p" data-group-id="3576832412-2">}</span></code></pre><p>If an error occurs during the installation, the system is rebooted using the old
│ │ │ │  version of the release. If installation succeeds, the system is afterwards using
│ │ │ │  the new version of the release, but if anything happens and the system is
│ │ │ │  rebooted, it starts using the previous version again.</p><p>To be made the default version, the newly installed release must be made
│ │ │ │  <em>permanent</em>, which means the previous version becomes <em>old</em>:</p><pre><code class="text">release_handler:make_permanent(Vsn) =&gt; ok</code></pre><p>The system keeps information about which versions are old and permanent in the
│ │ │ │ -files <code class="inline">$ROOT/releases/RELEASES</code> and <code class="inline">$ROOT/releases/start_erl.data</code>.</p><p>To downgrade from <code class="inline">Vsn</code> to <code class="inline">FromVsn</code>, <code class="inline">install_release</code> must be called again:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="8996478669-1">(</span><span class="n">FromVsn</span><span class="p" data-group-id="8996478669-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8996478669-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Vsn</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8996478669-3">[</span><span class="p" data-group-id="8996478669-3">]</span><span class="p" data-group-id="8996478669-2">}</span></code></pre><p>An installed, but not permanent, release can be <em>removed</em>. Information about the
│ │ │ │ +files <code class="inline">$ROOT/releases/RELEASES</code> and <code class="inline">$ROOT/releases/start_erl.data</code>.</p><p>To downgrade from <code class="inline">Vsn</code> to <code class="inline">FromVsn</code>, <code class="inline">install_release</code> must be called again:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="7613458393-1">(</span><span class="n">FromVsn</span><span class="p" data-group-id="7613458393-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7613458393-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Vsn</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7613458393-3">[</span><span class="p" data-group-id="7613458393-3">]</span><span class="p" data-group-id="7613458393-2">}</span></code></pre><p>An installed, but not permanent, release can be <em>removed</em>. Information about the
│ │ │ │  release is then deleted from <code class="inline">$ROOT/releases/RELEASES</code> and the release-specific
│ │ │ │  code, that is, the new application directories and the <code class="inline">$ROOT/releases/Vsn</code>
│ │ │ │  directory, are removed.</p><pre><code class="text">release_handler:remove_release(Vsn) =&gt; ok</code></pre><h3 id="example-continued-from-the-previous-sections" class="section-heading">
│ │ │ │    <a href="#example-continued-from-the-previous-sections" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Example (continued from the previous sections)</span>
│ │ │ │ @@ -367,17 +367,17 @@
│ │ │ │  is needed, the file is to contain the empty list:</p><pre><code class="text">[].</code></pre><p><em>Step 2)</em> Start the system as a simple target system. In reality, it is to be
│ │ │ │  started as an embedded system. However, using <code class="inline">erl</code> with the correct boot script
│ │ │ │  and config file is enough for illustration purposes:</p><pre><code class="text">% cd $ROOT
│ │ │ │  % bin/erl -boot $ROOT/releases/A/start -config $ROOT/releases/A/sys
│ │ │ │  ...</code></pre><p><code class="inline">$ROOT</code> is the installation directory of the target system.</p><p><em>Step 3)</em> In another Erlang shell, generate start scripts and create a release
│ │ │ │  package for the new version <code class="inline">&quot;B&quot;</code>. Remember to include (a possible updated)
│ │ │ │  <code class="inline">sys.config</code> and the <code class="inline">relup</code> file. For more information, see
│ │ │ │ -<a href="release_handling.xhtml#relup">Release Upgrade File</a>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="4419343650-1">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="4419343650-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<a href="release_handling.xhtml#relup">Release Upgrade File</a>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="6002219330-1">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="6002219330-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="4419343650-2">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="4419343650-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="6002219330-2">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="6002219330-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>The new release package now also contains version &quot;2&quot; of <code class="inline">ch_app</code> and the
│ │ │ │  <code class="inline">relup</code> file:</p><pre><code class="text">% tar tf ch_rel-2.tar
│ │ │ │  lib/kernel-9.2.4/ebin/kernel.app
│ │ │ │  lib/kernel-9.2.4/ebin/application.beam
│ │ │ │  ...
│ │ │ │  lib/stdlib-5.2.3/ebin/stdlib.app
│ │ │ │  lib/stdlib-5.2.3/ebin/argparse.beam
│ │ │ │ @@ -390,31 +390,31 @@
│ │ │ │  lib/ch_app-2/ebin/ch_sup.beam
│ │ │ │  lib/ch_app-2/ebin/ch3.beam
│ │ │ │  releases/B/start.boot
│ │ │ │  releases/B/relup
│ │ │ │  releases/B/sys.config
│ │ │ │  releases/B/ch_rel-2.rel
│ │ │ │  releases/ch_rel-2.rel</code></pre><p><em>Step 4)</em> Copy the release package <code class="inline">ch_rel-2.tar.gz</code> to the <code class="inline">$ROOT/releases</code>
│ │ │ │ -directory.</p><p><em>Step 5)</em> In the running target system, unpack the release package:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">unpack_release</span><span class="p" data-group-id="0999255859-1">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="0999255859-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0999255859-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="0999255859-2">}</span></code></pre><p>The new application version <code class="inline">ch_app-2</code> is installed under <code class="inline">$ROOT/lib</code> next to
│ │ │ │ +directory.</p><p><em>Step 5)</em> In the running target system, unpack the release package:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">unpack_release</span><span class="p" data-group-id="9572645199-1">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="9572645199-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9572645199-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="9572645199-2">}</span></code></pre><p>The new application version <code class="inline">ch_app-2</code> is installed under <code class="inline">$ROOT/lib</code> next to
│ │ │ │  <code class="inline">ch_app-1</code>. The <code class="inline">kernel</code>, <code class="inline">stdlib</code>, and <code class="inline">sasl</code> directories are not affected, as
│ │ │ │  they have not changed.</p><p>Under <code class="inline">$ROOT/releases</code>, a new directory <code class="inline">B</code> is created, containing
│ │ │ │ -<code class="inline">ch_rel-2.rel</code>, <code class="inline">start.boot</code>, <code class="inline">sys.config</code>, and <code class="inline">relup</code>.</p><p><em>Step 6)</em> Check if the function <code class="inline">ch3:available/0</code> is available:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">ch3</span><span class="p">:</span><span class="nf">available</span><span class="p" data-group-id="7518963047-1">(</span><span class="p" data-group-id="7518963047-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">ch_rel-2.rel</code>, <code class="inline">start.boot</code>, <code class="inline">sys.config</code>, and <code class="inline">relup</code>.</p><p><em>Step 6)</em> Check if the function <code class="inline">ch3:available/0</code> is available:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">ch3</span><span class="p">:</span><span class="nf">available</span><span class="p" data-group-id="0679769119-1">(</span><span class="p" data-group-id="0679769119-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: undefined function ch3:available/0</span></code></pre><p><em>Step 7)</em> Install the new release. The instructions in <code class="inline">$ROOT/releases/B/relup</code>
│ │ │ │  are executed one by one, resulting in the new version of <code class="inline">ch3</code> being loaded. The
│ │ │ │ -function <code class="inline">ch3:available/0</code> is now available:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="1993054760-1">(</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="1993054760-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1993054760-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="p" data-group-id="1993054760-3">[</span><span class="p" data-group-id="1993054760-3">]</span><span class="p" data-group-id="1993054760-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">ch3</span><span class="p">:</span><span class="nf">available</span><span class="p" data-group-id="1993054760-4">(</span><span class="p" data-group-id="1993054760-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +function <code class="inline">ch3:available/0</code> is now available:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="6038442774-1">(</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="6038442774-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6038442774-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="p" data-group-id="6038442774-3">[</span><span class="p" data-group-id="6038442774-3">]</span><span class="p" data-group-id="6038442774-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">ch3</span><span class="p">:</span><span class="nf">available</span><span class="p" data-group-id="6038442774-4">(</span><span class="p" data-group-id="6038442774-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">code</span><span class="p">:</span><span class="nf">which</span><span class="p" data-group-id="1993054760-5">(</span><span class="ss">ch3</span><span class="p" data-group-id="1993054760-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">code</span><span class="p">:</span><span class="nf">which</span><span class="p" data-group-id="6038442774-5">(</span><span class="ss">ch3</span><span class="p" data-group-id="6038442774-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;.../lib/ch_app-2/ebin/ch3.beam&quot;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nc">code</span><span class="p">:</span><span class="nf">which</span><span class="p" data-group-id="1993054760-6">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="1993054760-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nc">code</span><span class="p">:</span><span class="nf">which</span><span class="p" data-group-id="6038442774-6">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="6038442774-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;.../lib/ch_app-1/ebin/ch_sup.beam&quot;</span></code></pre><p>Processes in <code class="inline">ch_app</code> for which code has not been updated, for example, the
│ │ │ │  supervisor, are still evaluating code from <code class="inline">ch_app-1</code>.</p><p><em>Step 8)</em> If the target system is now rebooted, it uses version &quot;A&quot; again. The
│ │ │ │ -&quot;B&quot; version must be made permanent, to be used when the system is rebooted.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">7&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">make_permanent</span><span class="p" data-group-id="2766801615-1">(</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="2766801615-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +&quot;B&quot; version must be made permanent, to be used when the system is rebooted.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">7&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">make_permanent</span><span class="p" data-group-id="9469057646-1">(</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="9469057646-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p><a href="" id="sys"></a></p><h2 id="updating-application-specifications" class="section-heading">
│ │ │ │    <a href="#updating-application-specifications" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Updating Application Specifications</span>
│ │ │ │  </h2>
│ │ │ │  <p>When a new version of a release is installed, the application specifications are
│ │ │ │ @@ -423,14 +423,14 @@
│ │ │ │  boot script is generated from the same <code class="inline">.rel</code> file as is used to build the
│ │ │ │  release package itself.</p></section><p>Specifically, the application configuration parameters are automatically updated
│ │ │ │  according to (in increasing priority order):</p><ul><li>The data in the boot script, fetched from the new application resource file
│ │ │ │  <code class="inline">App.app</code></li><li>The new <code class="inline">sys.config</code></li><li>Command-line arguments <code class="inline">-App Par Val</code></li></ul><p>This means that parameter values set in the other system configuration files and
│ │ │ │  values set using <a href="../../../lib/kernel/doc/html/application.html#set_env/3"><code class="inline">application:set_env/3</code></a> are disregarded.</p><p>When an installed release is made permanent, the system process <code class="inline">init</code> is set to
│ │ │ │  point out the new <code class="inline">sys.config</code>.</p><p>After the installation, the application controller compares the old and new
│ │ │ │  configuration parameters for all running applications and calls the callback
│ │ │ │ -function:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">config_change</span><span class="p" data-group-id="2638035532-1">(</span><span class="n">Changed</span><span class="p">,</span><span class="w"> </span><span class="n">New</span><span class="p">,</span><span class="w"> </span><span class="n">Removed</span><span class="p" data-group-id="2638035532-1">)</span></code></pre><ul><li><code class="inline">Module</code> is the application callback module as defined by the <code class="inline">mod</code> key in the
│ │ │ │ +function:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">config_change</span><span class="p" data-group-id="7801581420-1">(</span><span class="n">Changed</span><span class="p">,</span><span class="w"> </span><span class="n">New</span><span class="p">,</span><span class="w"> </span><span class="n">Removed</span><span class="p" data-group-id="7801581420-1">)</span></code></pre><ul><li><code class="inline">Module</code> is the application callback module as defined by the <code class="inline">mod</code> key in the
│ │ │ │  <code class="inline">.app</code> file.</li><li><code class="inline">Changed</code> and <code class="inline">New</code> are lists of <code class="inline">{Par,Val}</code> for all changed and added
│ │ │ │  configuration parameters, respectively.</li><li><code class="inline">Removed</code> is a list of all parameters <code class="inline">Par</code> that have been removed.</li></ul><p>The function is optional and can be omitted when implementing an application
│ │ │ │  callback module.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/ref_man_records.xhtml
│ │ │ │ @@ -28,17 +28,17 @@
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Defining Records</span>
│ │ │ │  </h2>
│ │ │ │  <p>A record definition consists of the name of the record, followed by the field
│ │ │ │  names of the record. Record and field names must be atoms. Each field can be
│ │ │ │  given an optional default value. If no default value is supplied, <code class="inline">undefined</code> is
│ │ │ │ -used.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5223967764-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5223967764-2">{</span><span class="n">Field1</span><span class="w"> </span><span class="p" data-group-id="5223967764-3">[</span><span class="o">=</span><span class="w"> </span><span class="n">Expr1</span><span class="p" data-group-id="5223967764-3">]</span><span class="p">,</span><span class="w">
│ │ │ │ +used.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8281055787-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8281055787-2">{</span><span class="n">Field1</span><span class="w"> </span><span class="p" data-group-id="8281055787-3">[</span><span class="o">=</span><span class="w"> </span><span class="n">Expr1</span><span class="p" data-group-id="8281055787-3">]</span><span class="p">,</span><span class="w">
│ │ │ │                 </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -               </span><span class="n">FieldN</span><span class="w"> </span><span class="p" data-group-id="5223967764-4">[</span><span class="o">=</span><span class="w"> </span><span class="n">ExprN</span><span class="p" data-group-id="5223967764-4">]</span><span class="p" data-group-id="5223967764-2">}</span><span class="p" data-group-id="5223967764-1">)</span><span class="p">.</span></code></pre><p>The default value for a field is an arbitrary expression, except that it must
│ │ │ │ +               </span><span class="n">FieldN</span><span class="w"> </span><span class="p" data-group-id="8281055787-4">[</span><span class="o">=</span><span class="w"> </span><span class="n">ExprN</span><span class="p" data-group-id="8281055787-4">]</span><span class="p" data-group-id="8281055787-2">}</span><span class="p" data-group-id="8281055787-1">)</span><span class="p">.</span></code></pre><p>The default value for a field is an arbitrary expression, except that it must
│ │ │ │  not use any variables.</p><p>A record definition can be placed anywhere among the attributes and function
│ │ │ │  declarations of a module, but the definition must come before any usage of the
│ │ │ │  record.</p><p>If a record is used in several modules, it is recommended that the record
│ │ │ │  definition is placed in an include file.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Starting from Erlang/OTP 26, records can be defined in the Erlang shell
│ │ │ │  using the syntax described in this section. In earlier releases, it was
│ │ │ │  necessary to use the <a href="../../../lib/stdlib/doc/html/shell.html"><code class="inline">shell</code></a> built-in function <code class="inline">rd/2</code>.</p></section><h2 id="creating-records" class="section-heading">
│ │ │ │    <a href="#creating-records" class="hover-link">
│ │ │ │ @@ -48,32 +48,32 @@
│ │ │ │  </h2>
│ │ │ │  <p>The following expression creates a new <code class="inline">Name</code> record where the value of each
│ │ │ │  field <code class="inline">FieldI</code> is the value of evaluating the corresponding expression <code class="inline">ExprI</code>:</p><pre><code class="text">#Name{Field1=Expr1, ..., FieldK=ExprK}</code></pre><p>The fields can be in any order, not necessarily the same order as in the record
│ │ │ │  definition, and fields can be omitted. Omitted fields get their respective
│ │ │ │  default value instead.</p><p>If several fields are to be assigned the same value, the following construction
│ │ │ │  can be used:</p><pre><code class="text">#Name{Field1=Expr1, ..., FieldK=ExprK, _=ExprL}</code></pre><p>Omitted fields then get the value of evaluating <code class="inline">ExprL</code> instead of their default
│ │ │ │  values. This feature is primarily intended to be used to create patterns for ETS
│ │ │ │ -and Mnesia match functions.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4912348011-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4912348011-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="4912348011-2">}</span><span class="p" data-group-id="4912348011-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +and Mnesia match functions.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6659402101-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6659402101-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="6659402101-2">}</span><span class="p" data-group-id="6659402101-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">lookup</span><span class="p" data-group-id="4912348011-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Tab</span><span class="p" data-group-id="4912348011-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match_object</span><span class="p" data-group-id="4912348011-4">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="4912348011-5">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="4912348011-5">}</span><span class="p" data-group-id="4912348011-4">)</span><span class="p">.</span></code></pre><h2 id="accessing-record-fields" class="section-heading">
│ │ │ │ +</span><span class="nf">lookup</span><span class="p" data-group-id="6659402101-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Tab</span><span class="p" data-group-id="6659402101-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match_object</span><span class="p" data-group-id="6659402101-4">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6659402101-5">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="6659402101-5">}</span><span class="p" data-group-id="6659402101-4">)</span><span class="p">.</span></code></pre><h2 id="accessing-record-fields" class="section-heading">
│ │ │ │    <a href="#accessing-record-fields" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Accessing Record Fields</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="text">Expr#Name.Field</code></pre><p>Returns the value of the specified field. <code class="inline">Expr</code> is to evaluate to a <code class="inline">Name</code>
│ │ │ │ -record.</p><p><em>Example</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5697840377-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5697840377-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="5697840377-2">}</span><span class="p" data-group-id="5697840377-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +record.</p><p><em>Example</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4640852534-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4640852534-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="4640852534-2">}</span><span class="p" data-group-id="4640852534-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">get_person_name</span><span class="p" data-group-id="5697840377-3">(</span><span class="n">Person</span><span class="p" data-group-id="5697840377-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">get_person_name</span><span class="p" data-group-id="4640852534-3">(</span><span class="n">Person</span><span class="p" data-group-id="4640852534-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">.</span></code></pre><p>The following expression returns the position of the specified field in the
│ │ │ │ -tuple representation of the record:</p><pre><code class="text">#Name.Field</code></pre><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1575101612-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1575101612-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="1575101612-2">}</span><span class="p" data-group-id="1575101612-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +tuple representation of the record:</p><pre><code class="text">#Name.Field</code></pre><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6861355250-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6861355250-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="6861355250-2">}</span><span class="p" data-group-id="6861355250-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">lookup</span><span class="p" data-group-id="1575101612-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="1575101612-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="1575101612-4">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="1575101612-4">)</span><span class="p">.</span></code></pre><h2 id="updating-records" class="section-heading">
│ │ │ │ +</span><span class="nf">lookup</span><span class="p" data-group-id="6861355250-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="6861355250-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="6861355250-4">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="6861355250-4">)</span><span class="p">.</span></code></pre><h2 id="updating-records" class="section-heading">
│ │ │ │    <a href="#updating-records" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Updating Records</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="text">Expr#Name{Field1=Expr1, ..., FieldK=ExprK}</code></pre><p><code class="inline">Expr</code> is to evaluate to a <code class="inline">Name</code> record. A copy of this record is returned,
│ │ │ │  with the value of each specified field <code class="inline">FieldI</code> changed to the value of
│ │ │ │ @@ -83,48 +83,48 @@
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Records in Guards</span>
│ │ │ │  </h2>
│ │ │ │  <p>Since record expressions are expanded to tuple expressions, creating
│ │ │ │  records and accessing record fields are allowed in guards. However,
│ │ │ │  all subexpressions (for initializing fields) must be valid guard
│ │ │ │ -expressions as well.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle</span><span class="p" data-group-id="1212450039-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="1212450039-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Msg</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="o">#</span><span class="ss">msg</span><span class="p" data-group-id="1212450039-2">{</span><span class="ss">to</span><span class="o">=</span><span class="ss">void</span><span class="p">,</span><span class="w"> </span><span class="ss">no</span><span class="o">=</span><span class="mi">3</span><span class="p" data-group-id="1212450039-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +expressions as well.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle</span><span class="p" data-group-id="0754041851-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0754041851-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Msg</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="o">#</span><span class="ss">msg</span><span class="p" data-group-id="0754041851-2">{</span><span class="ss">to</span><span class="o">=</span><span class="ss">void</span><span class="p">,</span><span class="w"> </span><span class="ss">no</span><span class="o">=</span><span class="mi">3</span><span class="p" data-group-id="0754041851-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle</span><span class="p" data-group-id="1212450039-3">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="1212450039-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">running</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>There is also a type test BIF <a href="../../../lib/../erts/doc/html/erlang.html#is_record/2"><code class="inline">is_record(Term, RecordTag)</code></a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_person</span><span class="p" data-group-id="2071476903-1">(</span><span class="n">P</span><span class="p" data-group-id="2071476903-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="2071476903-2">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="2071476903-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle</span><span class="p" data-group-id="0754041851-3">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0754041851-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">running</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>There is also a type test BIF <a href="../../../lib/../erts/doc/html/erlang.html#is_record/2"><code class="inline">is_record(Term, RecordTag)</code></a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_person</span><span class="p" data-group-id="6058913454-1">(</span><span class="n">P</span><span class="p" data-group-id="6058913454-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="6058913454-2">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="6058913454-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">is_person</span><span class="p" data-group-id="2071476903-3">(</span><span class="p">_</span><span class="n">P</span><span class="p" data-group-id="2071476903-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">is_person</span><span class="p" data-group-id="6058913454-3">(</span><span class="p">_</span><span class="n">P</span><span class="p" data-group-id="6058913454-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">false</span><span class="p">.</span></code></pre><h2 id="records-in-patterns" class="section-heading">
│ │ │ │    <a href="#records-in-patterns" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Records in Patterns</span>
│ │ │ │  </h2>
│ │ │ │  <p>A pattern that matches a certain record is created in the same way as a record
│ │ │ │  is created:</p><pre><code class="text">#Name{Field1=Expr1, ..., FieldK=ExprK}</code></pre><p>In this case, one or more of <code class="inline">Expr1</code> ... <code class="inline">ExprK</code> can be unbound variables.</p><h2 id="nested-records" class="section-heading">
│ │ │ │    <a href="#nested-records" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Nested Records</span>
│ │ │ │  </h2>
│ │ │ │ -<p>Assume the following record definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6350839066-1">(</span><span class="ss">nrec0</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6350839066-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested0&quot;</span><span class="p" data-group-id="6350839066-2">}</span><span class="p" data-group-id="6350839066-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6350839066-3">(</span><span class="ss">nrec1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6350839066-4">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested1&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">nrec0</span><span class="o">=</span><span class="o">#</span><span class="ss">nrec0</span><span class="p" data-group-id="6350839066-5">{</span><span class="p" data-group-id="6350839066-5">}</span><span class="p" data-group-id="6350839066-4">}</span><span class="p" data-group-id="6350839066-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6350839066-6">(</span><span class="ss">nrec2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6350839066-7">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested2&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">nrec1</span><span class="o">=</span><span class="o">#</span><span class="ss">nrec1</span><span class="p" data-group-id="6350839066-8">{</span><span class="p" data-group-id="6350839066-8">}</span><span class="p" data-group-id="6350839066-7">}</span><span class="p" data-group-id="6350839066-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>Assume the following record definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7389708756-1">(</span><span class="ss">nrec0</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7389708756-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested0&quot;</span><span class="p" data-group-id="7389708756-2">}</span><span class="p" data-group-id="7389708756-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7389708756-3">(</span><span class="ss">nrec1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7389708756-4">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested1&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">nrec0</span><span class="o">=</span><span class="o">#</span><span class="ss">nrec0</span><span class="p" data-group-id="7389708756-5">{</span><span class="p" data-group-id="7389708756-5">}</span><span class="p" data-group-id="7389708756-4">}</span><span class="p" data-group-id="7389708756-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7389708756-6">(</span><span class="ss">nrec2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7389708756-7">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested2&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">nrec1</span><span class="o">=</span><span class="o">#</span><span class="ss">nrec1</span><span class="p" data-group-id="7389708756-8">{</span><span class="p" data-group-id="7389708756-8">}</span><span class="p" data-group-id="7389708756-7">}</span><span class="p" data-group-id="7389708756-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">N2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">nrec2</span><span class="p" data-group-id="6350839066-9">{</span><span class="p" data-group-id="6350839066-9">}</span><span class="p">,</span></code></pre><p>Accessing or updating nested records can be written without parentheses:</p><pre><code class="text">&quot;nested0&quot; = N2#nrec2.nrec1#nrec1.nrec0#nrec0.name,
│ │ │ │ +</span><span class="n">N2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">nrec2</span><span class="p" data-group-id="7389708756-9">{</span><span class="p" data-group-id="7389708756-9">}</span><span class="p">,</span></code></pre><p>Accessing or updating nested records can be written without parentheses:</p><pre><code class="text">&quot;nested0&quot; = N2#nrec2.nrec1#nrec1.nrec0#nrec0.name,
│ │ │ │      N0n = N2#nrec2.nrec1#nrec1.nrec0#nrec0{name = &quot;nested0a&quot;},</code></pre><p>which is equivalent to:</p><pre><code class="text">&quot;nested0&quot; = ((N2#nrec2.nrec1)#nrec1.nrec0)#nrec0.name,
│ │ │ │  N0n = ((N2#nrec2.nrec1)#nrec1.nrec0)#nrec0{name = &quot;nested0a&quot;},</code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP R14, parentheses were necessary when accessing or updating
│ │ │ │  nested records.</p></section><h2 id="internal-representation-of-records" class="section-heading">
│ │ │ │    <a href="#internal-representation-of-records" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Internal Representation of Records</span>
│ │ │ │  </h2>
│ │ │ │  <p>Record expressions are translated to tuple expressions during compilation. A
│ │ │ │ -record defined as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9388960435-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9388960435-2">{</span><span class="n">Field1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">FieldN</span><span class="p" data-group-id="9388960435-2">}</span><span class="p" data-group-id="9388960435-1">)</span><span class="p">.</span></code></pre><p>is internally represented by the tuple:</p><pre><code class="text">{Name, Value1, ..., ValueN}</code></pre><p>Here each <code class="inline">ValueI</code> is the default value for <code class="inline">FieldI</code>.</p><p>To each module using records, a pseudo function is added during compilation to
│ │ │ │ -obtain information about records:</p><pre><code class="makeup erlang" translate="no"><span class="nf">record_info</span><span class="p" data-group-id="2204064809-1">(</span><span class="ss">fields</span><span class="p">,</span><span class="w"> </span><span class="n">Record</span><span class="p" data-group-id="2204064809-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2204064809-2">[</span><span class="n">Field</span><span class="p" data-group-id="2204064809-2">]</span><span class="w">
│ │ │ │ -</span><span class="nf">record_info</span><span class="p" data-group-id="2204064809-3">(</span><span class="nb">size</span><span class="p">,</span><span class="w"> </span><span class="n">Record</span><span class="p" data-group-id="2204064809-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Size</span></code></pre><p><code class="inline">Size</code> is the size of the tuple representation, that is, one more than the
│ │ │ │ +record defined as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2251208175-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2251208175-2">{</span><span class="n">Field1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">FieldN</span><span class="p" data-group-id="2251208175-2">}</span><span class="p" data-group-id="2251208175-1">)</span><span class="p">.</span></code></pre><p>is internally represented by the tuple:</p><pre><code class="text">{Name, Value1, ..., ValueN}</code></pre><p>Here each <code class="inline">ValueI</code> is the default value for <code class="inline">FieldI</code>.</p><p>To each module using records, a pseudo function is added during compilation to
│ │ │ │ +obtain information about records:</p><pre><code class="makeup erlang" translate="no"><span class="nf">record_info</span><span class="p" data-group-id="7976448093-1">(</span><span class="ss">fields</span><span class="p">,</span><span class="w"> </span><span class="n">Record</span><span class="p" data-group-id="7976448093-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7976448093-2">[</span><span class="n">Field</span><span class="p" data-group-id="7976448093-2">]</span><span class="w">
│ │ │ │ +</span><span class="nf">record_info</span><span class="p" data-group-id="7976448093-3">(</span><span class="nb">size</span><span class="p">,</span><span class="w"> </span><span class="n">Record</span><span class="p" data-group-id="7976448093-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Size</span></code></pre><p><code class="inline">Size</code> is the size of the tuple representation, that is, one more than the
│ │ │ │  number of fields.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/ref_man_processes.xhtml
│ │ │ │ @@ -30,18 +30,18 @@
│ │ │ │  (grow and shrink dynamically) with a small memory footprint, fast to create and
│ │ │ │  terminate, and the scheduling overhead is low.</p><h2 id="process-creation" class="section-heading">
│ │ │ │    <a href="#process-creation" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Process Creation</span>
│ │ │ │  </h2>
│ │ │ │ -<p>A process is created by calling <a href="../../../lib/../erts/doc/html/erlang.html#spawn/3"><code class="inline">spawn()</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="4341042252-1">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="4341042252-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pid</span><span class="p" data-group-id="4341042252-2">(</span><span class="p" data-group-id="4341042252-2">)</span><span class="w">
│ │ │ │ -  </span><span class="n">Module</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="4341042252-3">(</span><span class="p" data-group-id="4341042252-3">)</span><span class="w">
│ │ │ │ -  </span><span class="n">Args</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4341042252-4">[</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="4341042252-4">]</span><span class="w">
│ │ │ │ -    </span><span class="n">ArgI</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="4341042252-5">(</span><span class="p" data-group-id="4341042252-5">)</span></code></pre><p><code class="inline">spawn()</code> creates a new process and returns the pid.</p><p>The new process starts executing in <code class="inline">Module:Name(Arg1,...,ArgN)</code> where the
│ │ │ │ +<p>A process is created by calling <a href="../../../lib/../erts/doc/html/erlang.html#spawn/3"><code class="inline">spawn()</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="9413686961-1">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="9413686961-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pid</span><span class="p" data-group-id="9413686961-2">(</span><span class="p" data-group-id="9413686961-2">)</span><span class="w">
│ │ │ │ +  </span><span class="n">Module</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="9413686961-3">(</span><span class="p" data-group-id="9413686961-3">)</span><span class="w">
│ │ │ │ +  </span><span class="n">Args</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9413686961-4">[</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="9413686961-4">]</span><span class="w">
│ │ │ │ +    </span><span class="n">ArgI</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="9413686961-5">(</span><span class="p" data-group-id="9413686961-5">)</span></code></pre><p><code class="inline">spawn()</code> creates a new process and returns the pid.</p><p>The new process starts executing in <code class="inline">Module:Name(Arg1,...,ArgN)</code> where the
│ │ │ │  arguments are the elements of the (possibly empty) <code class="inline">Args</code> argument list.</p><p>There exist a number of different <code class="inline">spawn</code> BIFs:</p><ul><li><a href="../../../lib/../erts/doc/html/erlang.html#spawn/4"><code class="inline">spawn/1,2,3,4</code></a></li><li><a href="../../../lib/../erts/doc/html/erlang.html#spawn_link/4"><code class="inline">spawn_link/1,2,3,4</code></a></li><li><a href="../../../lib/../erts/doc/html/erlang.html#spawn_monitor/4"><code class="inline">spawn_monitor/1,2,3,4</code></a></li><li><a href="../../../lib/../erts/doc/html/erlang.html#spawn_opt/5"><code class="inline">spawn_opt/2,3,4,5</code></a></li><li><a href="../../../lib/../erts/doc/html/erlang.html#spawn_request/5"><code class="inline">spawn_request/1,2,3,4,5</code></a></li></ul><h2 id="registered-processes" class="section-heading">
│ │ │ │    <a href="#registered-processes" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Registered Processes</span>
│ │ │ │  </h2>
│ │ │ │  <p>Besides addressing a process by using its pid, there are also BIFs for
│ │ │ ├── OEBPS/ref_man_functions.xhtml
│ │ │ │ @@ -25,51 +25,51 @@
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Function Declaration Syntax</span>
│ │ │ │  </h2>
│ │ │ │  <p>A <em>function declaration</em> is a sequence of function clauses separated by
│ │ │ │  semicolons, and terminated by a period (<code class="inline">.</code>).</p><p>A <em>function clause</em> consists of a <em>clause head</em> and a <em>clause body</em>, separated by
│ │ │ │  <code class="inline">-&gt;</code>.</p><p>A clause <em>head</em> consists of the function name, an argument list, and an optional
│ │ │ │ -guard sequence beginning with the keyword <code class="inline">when</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="p" data-group-id="5441603992-1">(</span><span class="n">Pattern11</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">Pattern1N</span><span class="p" data-group-id="5441603992-1">)</span><span class="w"> </span><span class="p" data-group-id="5441603992-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="5441603992-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +guard sequence beginning with the keyword <code class="inline">when</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="p" data-group-id="9013386684-1">(</span><span class="n">Pattern11</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">Pattern1N</span><span class="p" data-group-id="9013386684-1">)</span><span class="w"> </span><span class="p" data-group-id="9013386684-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="9013386684-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="n">Name</span><span class="p" data-group-id="5441603992-3">(</span><span class="n">PatternK1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">PatternKN</span><span class="p" data-group-id="5441603992-3">)</span><span class="w"> </span><span class="p" data-group-id="5441603992-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqK</span><span class="p" data-group-id="5441603992-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="n">Name</span><span class="p" data-group-id="9013386684-3">(</span><span class="n">PatternK1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">PatternKN</span><span class="p" data-group-id="9013386684-3">)</span><span class="w"> </span><span class="p" data-group-id="9013386684-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqK</span><span class="p" data-group-id="9013386684-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">BodyK</span><span class="p">.</span></code></pre><p>The function name is an atom. Each argument is a pattern.</p><p>The number of arguments <code class="inline">N</code> is the <em>arity</em> of the function. A function is
│ │ │ │  uniquely defined by the module name, function name, and arity. That is, two
│ │ │ │  functions with the same name and in the same module, but with different arities
│ │ │ │  are two different functions.</p><p>A function named <code class="inline">f</code> in module <code class="inline">mod</code> and with arity <code class="inline">N</code> is often denoted as
│ │ │ │  <code class="inline">mod:f/N</code>.</p><p>A clause <em>body</em> consists of a sequence of expressions separated by comma (<code class="inline">,</code>):</p><pre><code class="text">Expr1,
│ │ │ │  ...,
│ │ │ │  ExprN</code></pre><p>Valid Erlang expressions and guard sequences are described in
│ │ │ │ -<a href="expressions.xhtml">Expressions</a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">fact</span><span class="p" data-group-id="1595115448-1">(</span><span class="n">N</span><span class="p" data-group-id="1595115448-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% first clause head</span><span class="w">
│ │ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="1595115448-2">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="1595115448-2">)</span><span class="p">;</span><span class="w">     </span><span class="c1">% first clause body</span><span class="w">
│ │ │ │ +<a href="expressions.xhtml">Expressions</a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">fact</span><span class="p" data-group-id="5986547684-1">(</span><span class="n">N</span><span class="p" data-group-id="5986547684-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% first clause head</span><span class="w">
│ │ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="5986547684-2">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="5986547684-2">)</span><span class="p">;</span><span class="w">     </span><span class="c1">% first clause body</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="1595115448-3">(</span><span class="mi">0</span><span class="p" data-group-id="1595115448-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">             </span><span class="c1">% second clause head</span><span class="w">
│ │ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="5986547684-3">(</span><span class="mi">0</span><span class="p" data-group-id="5986547684-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">             </span><span class="c1">% second clause head</span><span class="w">
│ │ │ │      </span><span class="mi">1</span><span class="p">.</span><span class="w">                 </span><span class="c1">% second clause body</span></code></pre><p><a href="" id="eval"></a></p><h2 id="function-evaluation" class="section-heading">
│ │ │ │    <a href="#function-evaluation" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Function Evaluation</span>
│ │ │ │  </h2>
│ │ │ │  <p>When a function <code class="inline">M:F/N</code> is called, first the code for the function is located.
│ │ │ │  If the function cannot be found, an <code class="inline">undef</code> runtime error occurs. Notice that
│ │ │ │  the function must be exported to be visible outside the module it is defined in.</p><p>If the function is found, the function clauses are scanned sequentially until a
│ │ │ │  clause is found that fulfills both of the following two conditions:</p><ol><li>The patterns in the clause head can be successfully matched against the given
│ │ │ │  arguments.</li><li>The guard sequence, if any, is true.</li></ol><p>If such a clause cannot be found, a <code class="inline">function_clause</code> runtime error occurs.</p><p>If such a clause is found, the corresponding clause body is evaluated. That is,
│ │ │ │  the expressions in the body are evaluated sequentially and the value of the last
│ │ │ │ -expression is returned.</p><p>Consider the function <code class="inline">fact</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7139467893-1">(</span><span class="ss">mod</span><span class="p" data-group-id="7139467893-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7139467893-2">(</span><span class="p" data-group-id="7139467893-3">[</span><span class="ss">fact</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7139467893-3">]</span><span class="p" data-group-id="7139467893-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +expression is returned.</p><p>Consider the function <code class="inline">fact</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0968178690-1">(</span><span class="ss">mod</span><span class="p" data-group-id="0968178690-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0968178690-2">(</span><span class="p" data-group-id="0968178690-3">[</span><span class="ss">fact</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0968178690-3">]</span><span class="p" data-group-id="0968178690-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="7139467893-4">(</span><span class="n">N</span><span class="p" data-group-id="7139467893-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="7139467893-5">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="7139467893-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="7139467893-6">(</span><span class="mi">0</span><span class="p" data-group-id="7139467893-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="0968178690-4">(</span><span class="n">N</span><span class="p" data-group-id="0968178690-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="0968178690-5">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="0968178690-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="0968178690-6">(</span><span class="mi">0</span><span class="p" data-group-id="0968178690-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="mi">1</span><span class="p">.</span></code></pre><p>Assume that you want to calculate the factorial for 1:</p><pre><code class="text">1&gt; mod:fact(1).</code></pre><p>Evaluation starts at the first clause. The pattern <code class="inline">N</code> is matched against
│ │ │ │  argument 1. The matching succeeds and the guard (<code class="inline">N &gt; 0</code>) is true, thus <code class="inline">N</code> is
│ │ │ │ -bound to 1, and the corresponding body is evaluated:</p><pre><code class="makeup erlang" translate="no"><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="3726212700-1">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="3726212700-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3726212700-2">(</span><span class="n">N</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">bound</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="3726212700-2">)</span><span class="w">
│ │ │ │ -</span><span class="mi">1</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="3726212700-3">(</span><span class="mi">0</span><span class="p" data-group-id="3726212700-3">)</span></code></pre><p>Now, <code class="inline">fact(0)</code> is called, and the function clauses are scanned
│ │ │ │ +bound to 1, and the corresponding body is evaluated:</p><pre><code class="makeup erlang" translate="no"><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="5638175402-1">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="5638175402-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5638175402-2">(</span><span class="n">N</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">bound</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="5638175402-2">)</span><span class="w">
│ │ │ │ +</span><span class="mi">1</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="5638175402-3">(</span><span class="mi">0</span><span class="p" data-group-id="5638175402-3">)</span></code></pre><p>Now, <code class="inline">fact(0)</code> is called, and the function clauses are scanned
│ │ │ │  sequentially again. First, the pattern <code class="inline">N</code> is matched against 0. The
│ │ │ │  matching succeeds, but the guard (<code class="inline">N &gt; 0</code>) is false. Second, the
│ │ │ │  pattern <code class="inline">0</code> is matched against the argument <code class="inline">0</code>. The matching succeeds
│ │ │ │  and the body is evaluated:</p><pre><code class="text">1 * fact(0) =&gt;
│ │ │ │  1 * 1 =&gt;
│ │ │ │  1</code></pre><p>Evaluation has succeeded and <code class="inline">mod:fact(1)</code> returns 1.</p><p>If <code class="inline">mod:fact/1</code> is called with a negative number as argument, no clause head
│ │ │ │  matches. A <code class="inline">function_clause</code> runtime error occurs.</p><h2 id="tail-recursion" class="section-heading">
│ │ │ │ @@ -78,17 +78,17 @@
│ │ │ │    </a>
│ │ │ │    <span class="text">Tail recursion</span>
│ │ │ │  </h2>
│ │ │ │  <p>If the last expression of a function body is a function call, a
│ │ │ │  <em>tail-recursive call</em> is done. This is to ensure that no system
│ │ │ │  resources, for example, call stack, are consumed. This means that an
│ │ │ │  infinite loop using tail-recursive calls will not exhaust the call
│ │ │ │ -stack and can (in principle) run forever.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="8221537468-1">(</span><span class="n">N</span><span class="p" data-group-id="8221537468-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8221537468-2">(</span><span class="s">&quot;</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8221537468-3">[</span><span class="n">N</span><span class="p" data-group-id="8221537468-3">]</span><span class="p" data-group-id="8221537468-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="8221537468-4">(</span><span class="n">N</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="8221537468-4">)</span><span class="p">.</span></code></pre><p>The earlier factorial example is a counter-example. It is not
│ │ │ │ +stack and can (in principle) run forever.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="2371634863-1">(</span><span class="n">N</span><span class="p" data-group-id="2371634863-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2371634863-2">(</span><span class="s">&quot;</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2371634863-3">[</span><span class="n">N</span><span class="p" data-group-id="2371634863-3">]</span><span class="p" data-group-id="2371634863-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="2371634863-4">(</span><span class="n">N</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="2371634863-4">)</span><span class="p">.</span></code></pre><p>The earlier factorial example is a counter-example. It is not
│ │ │ │  tail-recursive, since a multiplication is done on the result of the recursive
│ │ │ │  call to <code class="inline">fact(N-1)</code>.</p><h2 id="built-in-functions-bifs" class="section-heading">
│ │ │ │    <a href="#built-in-functions-bifs" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Built-In Functions (BIFs)</span>
│ │ │ │  </h2>
│ │ │ │ @@ -96,14 +96,14 @@
│ │ │ │  system. BIFs do things that are difficult or impossible to implement
│ │ │ │  in Erlang. Most of the BIFs belong to module <a href="../../../lib/../erts/doc/html/erlang.html"><code class="inline">erlang</code></a>, but there
│ │ │ │  are also BIFs belonging to a few other modules, for example <a href="../../../lib/stdlib/doc/html/lists.html"><code class="inline">lists</code></a>
│ │ │ │  and <a href="../../../lib/stdlib/doc/html/ets.html"><code class="inline">ets</code></a>.</p><p>The most commonly used BIFs belonging to <a href="../../../lib/../erts/doc/html/erlang.html"><code class="inline">erlang</code></a> are <em>auto-imported</em>. They do
│ │ │ │  not need to be prefixed with the module name. Which BIFs are auto-imported
│ │ │ │  is specified in the <a href="../../../lib/../erts/doc/html/erlang.html"><code class="inline">erlang</code></a> module in ERTS. For example, standard-type
│ │ │ │  conversion BIFs like <code class="inline">atom_to_list</code> and BIFs allowed in guards can be called
│ │ │ │ -without specifying the module name.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="9766068674-1">(</span><span class="p" data-group-id="9766068674-2">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="9766068674-2">}</span><span class="p" data-group-id="9766068674-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +without specifying the module name.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="6140397059-1">(</span><span class="p" data-group-id="6140397059-2">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6140397059-2">}</span><span class="p" data-group-id="6140397059-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="9766068674-3">(</span><span class="ss">&#39;Erlang&#39;</span><span class="p" data-group-id="9766068674-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="6140397059-3">(</span><span class="ss">&#39;Erlang&#39;</span><span class="p" data-group-id="6140397059-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;Erlang&quot;</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/records_macros.xhtml
│ │ │ │ @@ -29,40 +29,40 @@
│ │ │ │  </h2>
│ │ │ │  <p>To illustrate this, the messenger example from the previous section is divided
│ │ │ │  into the following five files:</p><ul><li><p><code class="inline">mess_config.hrl</code></p><p>Header file for configuration data</p></li><li><p><code class="inline">mess_interface.hrl</code></p><p>Interface definitions between the client and the messenger</p></li><li><p><code class="inline">user_interface.erl</code></p><p>Functions for the user interface</p></li><li><p><code class="inline">mess_client.erl</code></p><p>Functions for the client side of the messenger</p></li><li><p><code class="inline">mess_server.erl</code></p><p>Functions for the server side of the messenger</p></li></ul><p>While doing this, the message passing interface between the shell, the client,
│ │ │ │  and the server is cleaned up and is defined using <em>records</em>. Also, <em>macros</em> are
│ │ │ │  introduced:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE mess_config.hrl----</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Configure the location of the server node,</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="1507048018-1">(</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="1507048018-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2246568599-1">(</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="2246568599-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%%----END FILE-----</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE mess_interface.hrl----</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Message interface between client and server and client shell for</span><span class="w">
│ │ │ │  </span><span class="c1">%%% messenger program</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%%Messages from Client to server received in server/1 function.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4766496406-1">(</span><span class="ss">logon</span><span class="p">,</span><span class="p" data-group-id="4766496406-2">{</span><span class="ss">client_pid</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="p" data-group-id="4766496406-2">}</span><span class="p" data-group-id="4766496406-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4766496406-3">(</span><span class="ss">message</span><span class="p">,</span><span class="p" data-group-id="4766496406-4">{</span><span class="ss">client_pid</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="4766496406-4">}</span><span class="p" data-group-id="4766496406-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="3989205287-1">(</span><span class="ss">logon</span><span class="p">,</span><span class="p" data-group-id="3989205287-2">{</span><span class="ss">client_pid</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="p" data-group-id="3989205287-2">}</span><span class="p" data-group-id="3989205287-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="3989205287-3">(</span><span class="ss">message</span><span class="p">,</span><span class="p" data-group-id="3989205287-4">{</span><span class="ss">client_pid</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="3989205287-4">}</span><span class="p" data-group-id="3989205287-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%% {&#39;EXIT&#39;, ClientPid, Reason}  (client terminated or unreachable.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Messages from Server to Client, received in await_result/0 function</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4766496406-5">(</span><span class="ss">abort_client</span><span class="p">,</span><span class="p" data-group-id="4766496406-6">{</span><span class="ss">message</span><span class="p" data-group-id="4766496406-6">}</span><span class="p" data-group-id="4766496406-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="3989205287-5">(</span><span class="ss">abort_client</span><span class="p">,</span><span class="p" data-group-id="3989205287-6">{</span><span class="ss">message</span><span class="p" data-group-id="3989205287-6">}</span><span class="p" data-group-id="3989205287-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%% Messages are: user_exists_at_other_node,</span><span class="w">
│ │ │ │  </span><span class="c1">%%%               you_are_not_logged_on</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4766496406-7">(</span><span class="ss">server_reply</span><span class="p">,</span><span class="p" data-group-id="4766496406-8">{</span><span class="ss">message</span><span class="p" data-group-id="4766496406-8">}</span><span class="p" data-group-id="4766496406-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="3989205287-7">(</span><span class="ss">server_reply</span><span class="p">,</span><span class="p" data-group-id="3989205287-8">{</span><span class="ss">message</span><span class="p" data-group-id="3989205287-8">}</span><span class="p" data-group-id="3989205287-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%% Messages are: logged_on</span><span class="w">
│ │ │ │  </span><span class="c1">%%%               receiver_not_found</span><span class="w">
│ │ │ │  </span><span class="c1">%%%               sent  (Message has been sent (no guarantee)</span><span class="w">
│ │ │ │  </span><span class="c1">%%% Messages from Server to Client received in client/1 function</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4766496406-9">(</span><span class="ss">message_from</span><span class="p">,</span><span class="p" data-group-id="4766496406-10">{</span><span class="ss">from_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="4766496406-10">}</span><span class="p" data-group-id="4766496406-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="3989205287-9">(</span><span class="ss">message_from</span><span class="p">,</span><span class="p" data-group-id="3989205287-10">{</span><span class="ss">from_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="3989205287-10">}</span><span class="p" data-group-id="3989205287-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Messages from shell to Client received in client/1 function</span><span class="w">
│ │ │ │  </span><span class="c1">%%% spawn(mess_client, client, [server_node(), Name])</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4766496406-11">(</span><span class="ss">message_to</span><span class="p">,</span><span class="p" data-group-id="4766496406-12">{</span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="4766496406-12">}</span><span class="p" data-group-id="4766496406-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="3989205287-11">(</span><span class="ss">message_to</span><span class="p">,</span><span class="p" data-group-id="3989205287-12">{</span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="3989205287-12">}</span><span class="p" data-group-id="3989205287-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%% logoff</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%%----END FILE-----</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE user_interface.erl----</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% User interface to the messenger program</span><span class="w">
│ │ │ │  </span><span class="c1">%%% login(Name)</span><span class="w">
│ │ │ │  </span><span class="c1">%%%     One user at a time can log in from each Erlang node in the</span><span class="w">
│ │ │ │ @@ -75,177 +75,177 @@
│ │ │ │  </span><span class="c1">%%%     Logs off anybody at that node</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% message(ToName, Message)</span><span class="w">
│ │ │ │  </span><span class="c1">%%%     sends Message to ToName. Error messages if the user of this</span><span class="w">
│ │ │ │  </span><span class="c1">%%%     function is not logged on or if ToName is not logged on at</span><span class="w">
│ │ │ │  </span><span class="c1">%%%     any node.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8151574643-1">(</span><span class="ss">user_interface</span><span class="p" data-group-id="8151574643-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8151574643-2">(</span><span class="p" data-group-id="8151574643-3">[</span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8151574643-3">]</span><span class="p" data-group-id="8151574643-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="8151574643-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="8151574643-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="8151574643-5">(</span><span class="s">&quot;mess_config.hrl&quot;</span><span class="p" data-group-id="8151574643-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5362511341-1">(</span><span class="ss">user_interface</span><span class="p" data-group-id="5362511341-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5362511341-2">(</span><span class="p" data-group-id="5362511341-3">[</span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5362511341-3">]</span><span class="p" data-group-id="5362511341-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="5362511341-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="5362511341-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="5362511341-5">(</span><span class="s">&quot;mess_config.hrl&quot;</span><span class="p" data-group-id="5362511341-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">logon</span><span class="p" data-group-id="8151574643-6">(</span><span class="n">Name</span><span class="p" data-group-id="8151574643-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="8151574643-7">(</span><span class="ss">mess_client</span><span class="p" data-group-id="8151574643-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">logon</span><span class="p" data-group-id="5362511341-6">(</span><span class="n">Name</span><span class="p" data-group-id="5362511341-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="5362511341-7">(</span><span class="ss">mess_client</span><span class="p" data-group-id="5362511341-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">register</span><span class="p" data-group-id="8151574643-8">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ │ -                     </span><span class="nf">spawn</span><span class="p" data-group-id="8151574643-9">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8151574643-10">[</span><span class="o">?</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="8151574643-10">]</span><span class="p" data-group-id="8151574643-9">)</span><span class="p" data-group-id="8151574643-8">)</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="nf">register</span><span class="p" data-group-id="5362511341-8">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ │ +                     </span><span class="nf">spawn</span><span class="p" data-group-id="5362511341-9">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5362511341-10">[</span><span class="o">?</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5362511341-10">]</span><span class="p" data-group-id="5362511341-9">)</span><span class="p" data-group-id="5362511341-8">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">already_logged_on</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">logoff</span><span class="p" data-group-id="8151574643-11">(</span><span class="p" data-group-id="8151574643-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">logoff</span><span class="p" data-group-id="5362511341-11">(</span><span class="p" data-group-id="5362511341-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">logoff</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">message</span><span class="p" data-group-id="8151574643-12">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="8151574643-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="8151574643-13">(</span><span class="ss">mess_client</span><span class="p" data-group-id="8151574643-13">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ │ +</span><span class="nf">message</span><span class="p" data-group-id="5362511341-12">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5362511341-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="5362511341-13">(</span><span class="ss">mess_client</span><span class="p" data-group-id="5362511341-13">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">not_logged_on</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="8151574643-14">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="8151574643-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="5362511341-14">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="5362511341-14">}</span><span class="p">,</span><span class="w">
│ │ │ │               </span><span class="ss">ok</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%%----END FILE-----</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE mess_client.erl----</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% The client process which runs on each user node</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6837012182-1">(</span><span class="ss">mess_client</span><span class="p" data-group-id="6837012182-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6837012182-2">(</span><span class="p" data-group-id="6837012182-3">[</span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6837012182-3">]</span><span class="p" data-group-id="6837012182-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="6837012182-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="6837012182-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="6837012182-5">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6837012182-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6837012182-6">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="6837012182-6">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">logon</span><span class="p" data-group-id="6837012182-7">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="nf">self</span><span class="p" data-group-id="6837012182-8">(</span><span class="p" data-group-id="6837012182-8">)</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="o">=</span><span class="n">Name</span><span class="p" data-group-id="6837012182-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">await_result</span><span class="p" data-group-id="6837012182-9">(</span><span class="p" data-group-id="6837012182-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="6837012182-10">(</span><span class="n">Server_Node</span><span class="p" data-group-id="6837012182-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5803861654-1">(</span><span class="ss">mess_client</span><span class="p" data-group-id="5803861654-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5803861654-2">(</span><span class="p" data-group-id="5803861654-3">[</span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5803861654-3">]</span><span class="p" data-group-id="5803861654-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="5803861654-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="5803861654-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="5803861654-5">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5803861654-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5803861654-6">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="5803861654-6">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">logon</span><span class="p" data-group-id="5803861654-7">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="nf">self</span><span class="p" data-group-id="5803861654-8">(</span><span class="p" data-group-id="5803861654-8">)</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="o">=</span><span class="n">Name</span><span class="p" data-group-id="5803861654-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">await_result</span><span class="p" data-group-id="5803861654-9">(</span><span class="p" data-group-id="5803861654-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="5803861654-10">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5803861654-10">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="6837012182-11">(</span><span class="n">Server_Node</span><span class="p" data-group-id="6837012182-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="5803861654-11">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5803861654-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">logoff</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="6837012182-12">(</span><span class="ss">normal</span><span class="p" data-group-id="6837012182-12">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="6837012182-13">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="6837012182-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="6837012182-14">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="6837012182-14">}</span><span class="w"> </span><span class="o">!</span><span class="w">
│ │ │ │ -                </span><span class="o">#</span><span class="ss">message</span><span class="p" data-group-id="6837012182-15">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="nf">self</span><span class="p" data-group-id="6837012182-16">(</span><span class="p" data-group-id="6837012182-16">)</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="6837012182-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">await_result</span><span class="p" data-group-id="6837012182-17">(</span><span class="p" data-group-id="6837012182-17">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6837012182-18">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6837012182-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6837012182-19">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6837012182-20">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6837012182-20">]</span><span class="p" data-group-id="6837012182-19">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="5803861654-12">(</span><span class="ss">normal</span><span class="p" data-group-id="5803861654-12">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="5803861654-13">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="5803861654-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="5803861654-14">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="5803861654-14">}</span><span class="w"> </span><span class="o">!</span><span class="w">
│ │ │ │ +                </span><span class="o">#</span><span class="ss">message</span><span class="p" data-group-id="5803861654-15">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="nf">self</span><span class="p" data-group-id="5803861654-16">(</span><span class="p" data-group-id="5803861654-16">)</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="5803861654-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">await_result</span><span class="p" data-group-id="5803861654-17">(</span><span class="p" data-group-id="5803861654-17">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="5803861654-18">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5803861654-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5803861654-19">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5803861654-20">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5803861654-20">]</span><span class="p" data-group-id="5803861654-19">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="6837012182-21">(</span><span class="n">Server_Node</span><span class="p" data-group-id="6837012182-21">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="5803861654-21">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5803861654-21">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% wait for a response from the server</span><span class="w">
│ │ │ │ -</span><span class="nf">await_result</span><span class="p" data-group-id="6837012182-22">(</span><span class="p" data-group-id="6837012182-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">await_result</span><span class="p" data-group-id="5803861654-22">(</span><span class="p" data-group-id="5803861654-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="6837012182-23">{</span><span class="ss">message</span><span class="o">=</span><span class="n">Why</span><span class="p" data-group-id="6837012182-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6837012182-24">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6837012182-25">[</span><span class="n">Why</span><span class="p" data-group-id="6837012182-25">]</span><span class="p" data-group-id="6837012182-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="6837012182-26">(</span><span class="ss">normal</span><span class="p" data-group-id="6837012182-26">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="6837012182-27">{</span><span class="ss">message</span><span class="o">=</span><span class="n">What</span><span class="p" data-group-id="6837012182-27">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6837012182-28">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6837012182-29">[</span><span class="n">What</span><span class="p" data-group-id="6837012182-29">]</span><span class="p" data-group-id="6837012182-28">)</span><span class="w">
│ │ │ │ +        </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="5803861654-23">{</span><span class="ss">message</span><span class="o">=</span><span class="n">Why</span><span class="p" data-group-id="5803861654-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5803861654-24">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5803861654-25">[</span><span class="n">Why</span><span class="p" data-group-id="5803861654-25">]</span><span class="p" data-group-id="5803861654-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="5803861654-26">(</span><span class="ss">normal</span><span class="p" data-group-id="5803861654-26">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="5803861654-27">{</span><span class="ss">message</span><span class="o">=</span><span class="n">What</span><span class="p" data-group-id="5803861654-27">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5803861654-28">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5803861654-29">[</span><span class="n">What</span><span class="p" data-group-id="5803861654-29">]</span><span class="p" data-group-id="5803861654-28">)</span><span class="w">
│ │ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6837012182-30">(</span><span class="s">&quot;No response from server</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6837012182-31">[</span><span class="p" data-group-id="6837012182-31">]</span><span class="p" data-group-id="6837012182-30">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="6837012182-32">(</span><span class="ss">timeout</span><span class="p" data-group-id="6837012182-32">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5803861654-30">(</span><span class="s">&quot;No response from server</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5803861654-31">[</span><span class="p" data-group-id="5803861654-31">]</span><span class="p" data-group-id="5803861654-30">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="5803861654-32">(</span><span class="ss">timeout</span><span class="p" data-group-id="5803861654-32">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%%----END FILE----</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE mess_server.erl----</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% This is the server process of the messenger service</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2641973896-1">(</span><span class="ss">mess_server</span><span class="p" data-group-id="2641973896-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2641973896-2">(</span><span class="p" data-group-id="2641973896-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2641973896-3">]</span><span class="p" data-group-id="2641973896-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="2641973896-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="2641973896-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="2641973896-5">(</span><span class="p" data-group-id="2641973896-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="2641973896-6">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="2641973896-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">server</span><span class="p" data-group-id="2641973896-7">(</span><span class="p" data-group-id="2641973896-8">[</span><span class="p" data-group-id="2641973896-8">]</span><span class="p" data-group-id="2641973896-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3313248870-1">(</span><span class="ss">mess_server</span><span class="p" data-group-id="3313248870-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3313248870-2">(</span><span class="p" data-group-id="3313248870-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3313248870-3">]</span><span class="p" data-group-id="3313248870-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="3313248870-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="3313248870-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="3313248870-5">(</span><span class="p" data-group-id="3313248870-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="3313248870-6">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3313248870-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">server</span><span class="p" data-group-id="3313248870-7">(</span><span class="p" data-group-id="3313248870-8">[</span><span class="p" data-group-id="3313248870-8">]</span><span class="p" data-group-id="3313248870-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% the user list has the format [{ClientPid1, Name1},{ClientPid2, Name2},...]</span><span class="w">
│ │ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="2641973896-9">(</span><span class="n">User_List</span><span class="p" data-group-id="2641973896-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2641973896-10">(</span><span class="s">&quot;User list = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2641973896-11">[</span><span class="n">User_List</span><span class="p" data-group-id="2641973896-11">]</span><span class="p" data-group-id="2641973896-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="3313248870-9">(</span><span class="n">User_List</span><span class="p" data-group-id="3313248870-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3313248870-10">(</span><span class="s">&quot;User list = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3313248870-11">[</span><span class="n">User_List</span><span class="p" data-group-id="3313248870-11">]</span><span class="p" data-group-id="3313248870-10">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="o">#</span><span class="ss">logon</span><span class="p" data-group-id="2641973896-12">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="o">=</span><span class="n">Name</span><span class="p" data-group-id="2641973896-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="2641973896-13">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="2641973896-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="2641973896-14">(</span><span class="n">New_User_List</span><span class="p" data-group-id="2641973896-14">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="2641973896-15">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="2641973896-15">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="2641973896-16">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="2641973896-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="2641973896-17">(</span><span class="n">New_User_List</span><span class="p" data-group-id="2641973896-17">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="o">#</span><span class="ss">message</span><span class="p" data-group-id="2641973896-18">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="2641973896-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="2641973896-19">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="2641973896-19">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="2641973896-20">(</span><span class="n">User_List</span><span class="p" data-group-id="2641973896-20">)</span><span class="w">
│ │ │ │ +        </span><span class="o">#</span><span class="ss">logon</span><span class="p" data-group-id="3313248870-12">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="o">=</span><span class="n">Name</span><span class="p" data-group-id="3313248870-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="3313248870-13">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3313248870-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="3313248870-14">(</span><span class="n">New_User_List</span><span class="p" data-group-id="3313248870-14">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3313248870-15">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="3313248870-15">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="3313248870-16">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3313248870-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="3313248870-17">(</span><span class="n">New_User_List</span><span class="p" data-group-id="3313248870-17">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="o">#</span><span class="ss">message</span><span class="p" data-group-id="3313248870-18">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="3313248870-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="3313248870-19">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3313248870-19">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="3313248870-20">(</span><span class="n">User_List</span><span class="p" data-group-id="3313248870-20">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Start the server</span><span class="w">
│ │ │ │ -</span><span class="nf">start_server</span><span class="p" data-group-id="2641973896-21">(</span><span class="p" data-group-id="2641973896-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="2641973896-22">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="2641973896-23">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2641973896-24">[</span><span class="p" data-group-id="2641973896-24">]</span><span class="p" data-group-id="2641973896-23">)</span><span class="p" data-group-id="2641973896-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_server</span><span class="p" data-group-id="3313248870-21">(</span><span class="p" data-group-id="3313248870-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="3313248870-22">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="3313248870-23">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3313248870-24">[</span><span class="p" data-group-id="3313248870-24">]</span><span class="p" data-group-id="3313248870-23">)</span><span class="p" data-group-id="3313248870-22">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server adds a new user to the user list</span><span class="w">
│ │ │ │ -</span><span class="nf">server_logon</span><span class="p" data-group-id="2641973896-25">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="2641973896-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_logon</span><span class="p" data-group-id="3313248870-25">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3313248870-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% check if logged on anywhere else</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="2641973896-26">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="2641973896-26">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="3313248870-26">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3313248870-26">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="2641973896-27">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="2641973896-27">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="3313248870-27">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="3313248870-27">}</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">User_List</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="2641973896-28">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">logged_on</span><span class="p" data-group-id="2641973896-28">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">link</span><span class="p" data-group-id="2641973896-29">(</span><span class="n">From</span><span class="p" data-group-id="2641973896-29">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="2641973896-30">[</span><span class="p" data-group-id="2641973896-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="2641973896-31">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="2641973896-30">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="3313248870-28">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">logged_on</span><span class="p" data-group-id="3313248870-28">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">link</span><span class="p" data-group-id="3313248870-29">(</span><span class="n">From</span><span class="p" data-group-id="3313248870-29">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="3313248870-30">[</span><span class="p" data-group-id="3313248870-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3313248870-31">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3313248870-30">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server deletes a user from the user list</span><span class="w">
│ │ │ │ -</span><span class="nf">server_logoff</span><span class="p" data-group-id="2641973896-32">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="2641973896-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="2641973896-33">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="2641973896-33">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">server_logoff</span><span class="p" data-group-id="3313248870-32">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3313248870-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="3313248870-33">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3313248870-33">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server transfers a message between users</span><span class="w">
│ │ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="2641973896-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="2641973896-34">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="3313248870-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3313248870-34">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% check that the user is logged on and who he is</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="2641973896-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="2641973896-35">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="3313248870-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3313248870-35">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="2641973896-36">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="2641973896-36">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="2641973896-37">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="2641973896-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="2641973896-38">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="2641973896-38">)</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="3313248870-36">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="3313248870-36">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3313248870-37">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3313248870-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="3313248870-38">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3313248870-38">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%% If the user exists, send the message</span><span class="w">
│ │ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="2641973896-39">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="2641973896-39">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="3313248870-39">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3313248870-39">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Find the receiver and send the message</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="2641973896-40">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="2641973896-40">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="3313248870-40">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3313248870-40">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="2641973896-41">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">receiver_not_found</span><span class="p" data-group-id="2641973896-41">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="2641973896-42">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="2641973896-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">message_from</span><span class="p" data-group-id="2641973896-43">{</span><span class="ss">from_name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="2641973896-43">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w">  </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="2641973896-44">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">sent</span><span class="p" data-group-id="2641973896-44">}</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="3313248870-41">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">receiver_not_found</span><span class="p" data-group-id="3313248870-41">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3313248870-42">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="3313248870-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">message_from</span><span class="p" data-group-id="3313248870-43">{</span><span class="ss">from_name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="3313248870-43">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w">  </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="3313248870-44">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">sent</span><span class="p" data-group-id="3313248870-44">}</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%%----END FILE----</span></code></pre><h2 id="header-files" class="section-heading">
│ │ │ │    <a href="#header-files" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Header Files</span>
│ │ │ │  </h2>
│ │ │ │  <p>As shown above, some files have extension <code class="inline">.hrl</code>. These are header files that
│ │ │ │ -are included in the <code class="inline">.erl</code> files by:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="2970686334-1">(</span><span class="s">&quot;File_Name&quot;</span><span class="p" data-group-id="2970686334-1">)</span><span class="p">.</span></code></pre><p>for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="8967148910-1">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="8967148910-1">)</span><span class="p">.</span></code></pre><p>In the case above the file is fetched from the same directory as all the other
│ │ │ │ +are included in the <code class="inline">.erl</code> files by:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="5967152604-1">(</span><span class="s">&quot;File_Name&quot;</span><span class="p" data-group-id="5967152604-1">)</span><span class="p">.</span></code></pre><p>for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="1217008668-1">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="1217008668-1">)</span><span class="p">.</span></code></pre><p>In the case above the file is fetched from the same directory as all the other
│ │ │ │  files in the messenger example. (<em>manual</em>)</p><p>.hrl files can contain any valid Erlang code but are most often used for record
│ │ │ │  and macro definitions.</p><h2 id="records" class="section-heading">
│ │ │ │    <a href="#records" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Records</span>
│ │ │ │  </h2>
│ │ │ │ -<p>A record is defined as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6808184300-1">(</span><span class="ss">name_of_record</span><span class="p">,</span><span class="p" data-group-id="6808184300-2">{</span><span class="ss">field_name1</span><span class="p">,</span><span class="w"> </span><span class="ss">field_name2</span><span class="p">,</span><span class="w"> </span><span class="ss">field_name3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6808184300-2">}</span><span class="p" data-group-id="6808184300-1">)</span><span class="p">.</span></code></pre><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6056392736-1">(</span><span class="ss">message_to</span><span class="p">,</span><span class="p" data-group-id="6056392736-2">{</span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="6056392736-2">}</span><span class="p" data-group-id="6056392736-1">)</span><span class="p">.</span></code></pre><p>This is equivalent to:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6782050176-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To_Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6782050176-1">}</span></code></pre><p>Creating a record is best illustrated by an example:</p><pre><code class="makeup erlang" translate="no"><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="7861118748-1">{</span><span class="ss">message</span><span class="o">=</span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="ss">fred</span><span class="p" data-group-id="7861118748-1">}</span></code></pre><p>This creates:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5164499950-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="5164499950-1">}</span></code></pre><p>Notice that you do not have to worry about the order in which you assign values to the
│ │ │ │ +<p>A record is defined as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6283991773-1">(</span><span class="ss">name_of_record</span><span class="p">,</span><span class="p" data-group-id="6283991773-2">{</span><span class="ss">field_name1</span><span class="p">,</span><span class="w"> </span><span class="ss">field_name2</span><span class="p">,</span><span class="w"> </span><span class="ss">field_name3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6283991773-2">}</span><span class="p" data-group-id="6283991773-1">)</span><span class="p">.</span></code></pre><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0412696160-1">(</span><span class="ss">message_to</span><span class="p">,</span><span class="p" data-group-id="0412696160-2">{</span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="0412696160-2">}</span><span class="p" data-group-id="0412696160-1">)</span><span class="p">.</span></code></pre><p>This is equivalent to:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4298533253-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To_Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="4298533253-1">}</span></code></pre><p>Creating a record is best illustrated by an example:</p><pre><code class="makeup erlang" translate="no"><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="2721277808-1">{</span><span class="ss">message</span><span class="o">=</span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="ss">fred</span><span class="p" data-group-id="2721277808-1">}</span></code></pre><p>This creates:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1453959757-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1453959757-1">}</span></code></pre><p>Notice that you do not have to worry about the order in which you assign values to the
│ │ │ │  various parts of a record when you create it. The advantage of using records
│ │ │ │  is that by placing their definitions in header files you can conveniently define
│ │ │ │  interfaces that are easy to change. For example, if you want to add a new field
│ │ │ │  to the record, you only have to change the code where the new field is used and
│ │ │ │  not at every place the record is referred to. If you leave out a field when
│ │ │ │  creating a record, it gets the value of the atom <code class="inline">undefined</code>. (<em>manual</em>)</p><p>Pattern matching with records is very similar to creating records. For example,
│ │ │ │ -inside a <code class="inline">case</code> or <code class="inline">receive</code>:</p><pre><code class="makeup erlang" translate="no"><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="2421011508-1">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="2421011508-1">}</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>This is the same as:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9098503461-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9098503461-1">}</span></code></pre><h2 id="macros" class="section-heading">
│ │ │ │ +inside a <code class="inline">case</code> or <code class="inline">receive</code>:</p><pre><code class="makeup erlang" translate="no"><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="7311764081-1">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="7311764081-1">}</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>This is the same as:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6462283487-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6462283487-1">}</span></code></pre><h2 id="macros" class="section-heading">
│ │ │ │    <a href="#macros" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Macros</span>
│ │ │ │  </h2>
│ │ │ │  <p>Another thing that has been added to the messenger is a macro. The file
│ │ │ │  <code class="inline">mess_config.hrl</code> contains the definition:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%%% Configure the location of the server node,</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3424619869-1">(</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="3424619869-1">)</span><span class="p">.</span></code></pre><p>This file is included in <code class="inline">mess_server.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="4347101618-1">(</span><span class="s">&quot;mess_config.hrl&quot;</span><span class="p" data-group-id="4347101618-1">)</span><span class="p">.</span></code></pre><p>Every occurrence of <code class="inline">?server_node</code> in <code class="inline">mess_server.erl</code> is now replaced by
│ │ │ │ -<code class="inline">messenger@super</code>.</p><p>A macro is also used when spawning the server process:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="2512662028-1">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2512662028-2">[</span><span class="p" data-group-id="2512662028-2">]</span><span class="p" data-group-id="2512662028-1">)</span></code></pre><p>This is a standard macro (that is, defined by the system, not by the user).
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9499557116-1">(</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="9499557116-1">)</span><span class="p">.</span></code></pre><p>This file is included in <code class="inline">mess_server.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="2165336194-1">(</span><span class="s">&quot;mess_config.hrl&quot;</span><span class="p" data-group-id="2165336194-1">)</span><span class="p">.</span></code></pre><p>Every occurrence of <code class="inline">?server_node</code> in <code class="inline">mess_server.erl</code> is now replaced by
│ │ │ │ +<code class="inline">messenger@super</code>.</p><p>A macro is also used when spawning the server process:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="4750307103-1">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4750307103-2">[</span><span class="p" data-group-id="4750307103-2">]</span><span class="p" data-group-id="4750307103-1">)</span></code></pre><p>This is a standard macro (that is, defined by the system, not by the user).
│ │ │ │  <code class="inline">?MODULE</code> is always replaced by the name of the current module (that is, the
│ │ │ │  <code class="inline">-module</code> definition near the start of the file). There are more advanced ways
│ │ │ │  of using macros with, for example, <a href="macros.xhtml#defining-and-using-macros">parameters</a>.</p><p>The three Erlang (<code class="inline">.erl</code>) files in the messenger example are individually
│ │ │ │  compiled into object code files (<code class="inline">.beam</code>). The Erlang system loads and links
│ │ │ │  these files into the system when they are referred to during execution of the
│ │ │ │  code. In this case, they are simply put in our current working directory (that
│ │ │ │  is, the place you have done &quot;cd&quot; to). There are ways of putting the <code class="inline">.beam</code>
│ │ │ ├── OEBPS/prog_ex_records.xhtml
│ │ │ │ @@ -27,105 +27,105 @@
│ │ │ │    <span class="text">Records and Tuples</span>
│ │ │ │  </h2>
│ │ │ │  <p>The main advantage of using records rather than tuples is that fields in a
│ │ │ │  record are accessed by name, whereas fields in a tuple are accessed by position.
│ │ │ │  To illustrate these differences, suppose that you want to represent a person
│ │ │ │  with the tuple <code class="inline">{Name, Address, Phone}</code>.</p><p>To write functions that manipulate this data, remember the following:</p><ul><li>The <code class="inline">Name</code> field is the first element of the tuple.</li><li>The <code class="inline">Address</code> field is the second element.</li><li>The <code class="inline">Phone</code> field is the third element.</li></ul><p>For example, to extract data from a variable <code class="inline">P</code> that contains such a tuple, you
│ │ │ │  can write the following code and then use pattern matching to extract the
│ │ │ │ -relevant fields:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">element</span><span class="p" data-group-id="2108837666-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">P</span><span class="p" data-group-id="2108837666-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">element</span><span class="p" data-group-id="2108837666-2">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">P</span><span class="p" data-group-id="2108837666-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +relevant fields:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">element</span><span class="p" data-group-id="0245275427-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">P</span><span class="p" data-group-id="0245275427-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">element</span><span class="p" data-group-id="0245275427-2">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">P</span><span class="p" data-group-id="0245275427-2">)</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Such code is difficult to read and understand, and errors occur if the numbering
│ │ │ │  of the elements in the tuple is wrong. If the data representation of the fields
│ │ │ │  is changed, by re-ordering, adding, or removing fields, all references to the
│ │ │ │  person tuple must be checked and possibly modified.</p><p>Records allow references to the fields by name, instead of by position. In the
│ │ │ │ -following example, a record instead of a tuple is used to store the data:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1981791948-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1981791948-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="1981791948-2">}</span><span class="p" data-group-id="1981791948-1">)</span><span class="p">.</span></code></pre><p>This enables references to the fields of the record by name. For example, if <code class="inline">P</code>
│ │ │ │ +following example, a record instead of a tuple is used to store the data:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9428465912-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9428465912-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="9428465912-2">}</span><span class="p" data-group-id="9428465912-1">)</span><span class="p">.</span></code></pre><p>This enables references to the fields of the record by name. For example, if <code class="inline">P</code>
│ │ │ │  is a variable whose value is a <code class="inline">person</code> record, the following code accesses the
│ │ │ │  name and address fields of the record:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="n">Address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">address</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Internally, records are represented using tagged tuples:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2661685970-1">{</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="n">Address</span><span class="p" data-group-id="2661685970-1">}</span></code></pre><h2 id="defining-a-record" class="section-heading">
│ │ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Internally, records are represented using tagged tuples:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0536409867-1">{</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="n">Address</span><span class="p" data-group-id="0536409867-1">}</span></code></pre><h2 id="defining-a-record" class="section-heading">
│ │ │ │    <a href="#defining-a-record" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Defining a Record</span>
│ │ │ │  </h2>
│ │ │ │  <p>The following definition of a <code class="inline">person</code> is used in several examples in this
│ │ │ │  section. Three fields are included, <code class="inline">name</code>, <code class="inline">phone</code>, and <code class="inline">address</code>. The default
│ │ │ │  values for <code class="inline">name</code> and <code class="inline">phone</code> are &quot;&quot; and [], respectively. The default value for
│ │ │ │  <code class="inline">address</code> is the atom <code class="inline">undefined</code>, since no default value is supplied for this
│ │ │ │ -field:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0893991856-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0893991856-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0893991856-3">[</span><span class="p" data-group-id="0893991856-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="0893991856-2">}</span><span class="p" data-group-id="0893991856-1">)</span><span class="p">.</span></code></pre><p>The record must be defined in the shell to enable use of the record syntax in
│ │ │ │ -the examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">rd</span><span class="p" data-group-id="4659974480-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4659974480-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4659974480-3">[</span><span class="p" data-group-id="4659974480-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="4659974480-2">}</span><span class="p" data-group-id="4659974480-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +field:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0320845763-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0320845763-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0320845763-3">[</span><span class="p" data-group-id="0320845763-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="0320845763-2">}</span><span class="p" data-group-id="0320845763-1">)</span><span class="p">.</span></code></pre><p>The record must be defined in the shell to enable use of the record syntax in
│ │ │ │ +the examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">rd</span><span class="p" data-group-id="1479806778-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1479806778-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1479806778-3">[</span><span class="p" data-group-id="1479806778-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="1479806778-2">}</span><span class="p" data-group-id="1479806778-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">person</span></code></pre><p>This is because record definitions are only available at compile time, not at
│ │ │ │  runtime. For details on records in the shell, see the <a href="../../../lib/stdlib/doc/html/shell.html"><code class="inline">shell</code></a> manual page in
│ │ │ │  STDLIB.</p><h2 id="creating-a-record" class="section-heading">
│ │ │ │    <a href="#creating-a-record" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Creating a Record</span>
│ │ │ │  </h2>
│ │ │ │ -<p>A new <code class="inline">person</code> record is created as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6838529546-1">{</span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="6838529546-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6838529546-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p" data-group-id="6838529546-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6838529546-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6838529546-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6838529546-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">undefined</span><span class="p" data-group-id="6838529546-3">}</span></code></pre><p>As the <code class="inline">address</code> field was omitted, its default value is used.</p><p>From Erlang 5.1/OTP R8B, a value to all fields in a record can be set with the
│ │ │ │ -special field <code class="inline">_</code>. <code class="inline">_</code> means &quot;all fields not explicitly specified&quot;.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9872481385-1">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Jakob&quot;</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="9872481385-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9872481385-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Jakob&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="9872481385-2">}</span></code></pre><p>It is primarily intended to be used in <a href="../../../lib/stdlib/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a> and
│ │ │ │ +<p>A new <code class="inline">person</code> record is created as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7498686608-1">{</span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="7498686608-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7498686608-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p" data-group-id="7498686608-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7498686608-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7498686608-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7498686608-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">undefined</span><span class="p" data-group-id="7498686608-3">}</span></code></pre><p>As the <code class="inline">address</code> field was omitted, its default value is used.</p><p>From Erlang 5.1/OTP R8B, a value to all fields in a record can be set with the
│ │ │ │ +special field <code class="inline">_</code>. <code class="inline">_</code> means &quot;all fields not explicitly specified&quot;.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2973810700-1">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Jakob&quot;</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="2973810700-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2973810700-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Jakob&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="2973810700-2">}</span></code></pre><p>It is primarily intended to be used in <a href="../../../lib/stdlib/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a> and
│ │ │ │  <a href="../../../lib/mnesia/doc/html/mnesia.html#match_object/3"><code class="inline">mnesia:match_object/3</code></a>, to set record fields to the atom <code class="inline">'_'</code>. (This is a
│ │ │ │  wildcard in <a href="../../../lib/stdlib/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a>.)</p><h2 id="accessing-a-record-field" class="section-heading">
│ │ │ │    <a href="#accessing-a-record-field" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Accessing a Record Field</span>
│ │ │ │  </h2>
│ │ │ │ -<p>The following example shows how to access a record field:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2852178848-1">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2852178848-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2852178848-2">]</span><span class="p" data-group-id="2852178848-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2852178848-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2852178848-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2852178848-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">undefined</span><span class="p" data-group-id="2852178848-3">}</span><span class="w">
│ │ │ │ +<p>The following example shows how to access a record field:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="4805327132-1">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4805327132-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4805327132-2">]</span><span class="p" data-group-id="4805327132-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="4805327132-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4805327132-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4805327132-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">undefined</span><span class="p" data-group-id="4805327132-3">}</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">&gt; </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;Joe&quot;</span></code></pre><h2 id="updating-a-record" class="section-heading">
│ │ │ │    <a href="#updating-a-record" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Updating a Record</span>
│ │ │ │  </h2>
│ │ │ │ -<p>The following example shows how to update a record:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6522112384-1">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="6522112384-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6522112384-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="o">=</span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="6522112384-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6522112384-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6522112384-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6522112384-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="6522112384-3">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">P2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P1</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6522112384-5">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p" data-group-id="6522112384-5">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6522112384-6">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6522112384-7">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6522112384-7">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="6522112384-6">}</span></code></pre><h2 id="type-testing" class="section-heading">
│ │ │ │ +<p>The following example shows how to update a record:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3318343441-1">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="3318343441-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3318343441-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="o">=</span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="3318343441-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3318343441-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3318343441-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3318343441-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="3318343441-3">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">P2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P1</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3318343441-5">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p" data-group-id="3318343441-5">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3318343441-6">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3318343441-7">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3318343441-7">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="3318343441-6">}</span></code></pre><h2 id="type-testing" class="section-heading">
│ │ │ │    <a href="#type-testing" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Type Testing</span>
│ │ │ │  </h2>
│ │ │ │  <p>The following example shows that the guard succeeds if <code class="inline">P</code> is a record of type
│ │ │ │ -<code class="inline">person</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="2188566719-1">(</span><span class="n">P</span><span class="p" data-group-id="2188566719-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="2188566719-2">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="2188566719-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">a_person</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="2188566719-3">(</span><span class="p">_</span><span class="p" data-group-id="2188566719-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">not_a_person</span><span class="p">.</span></code></pre><h2 id="pattern-matching" class="section-heading">
│ │ │ │ +<code class="inline">person</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="5625501144-1">(</span><span class="n">P</span><span class="p" data-group-id="5625501144-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="5625501144-2">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="5625501144-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">a_person</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="5625501144-3">(</span><span class="p">_</span><span class="p" data-group-id="5625501144-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">not_a_person</span><span class="p">.</span></code></pre><h2 id="pattern-matching" class="section-heading">
│ │ │ │    <a href="#pattern-matching" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Pattern Matching</span>
│ │ │ │  </h2>
│ │ │ │  <p>Matching can be used in combination with records, as shown in the following
│ │ │ │ -example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8813644822-1">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="8813644822-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="8813644822-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="o">=</span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="8813644822-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8813644822-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8813644822-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="8813644822-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="8813644822-3">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8813644822-5">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="8813644822-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P3</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">.</span><span class="w">
│ │ │ │ +example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5877316125-1">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="5877316125-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="5877316125-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="o">=</span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="5877316125-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5877316125-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5877316125-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="5877316125-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="5877316125-3">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5877316125-5">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5877316125-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P3</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;Joe&quot;</span></code></pre><p>The following function takes a list of <code class="inline">person</code> records and searches for the
│ │ │ │ -phone number of a person with a particular name:</p><pre><code class="makeup erlang" translate="no"><span class="nf">find_phone</span><span class="p" data-group-id="6282107381-1">(</span><span class="p" data-group-id="6282107381-2">[</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6282107381-3">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="n">Phone</span><span class="p" data-group-id="6282107381-3">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="6282107381-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6282107381-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6282107381-4">{</span><span class="ss">found</span><span class="p">,</span><span class="w">  </span><span class="n">Phone</span><span class="p" data-group-id="6282107381-4">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">find_phone</span><span class="p" data-group-id="6282107381-5">(</span><span class="p" data-group-id="6282107381-6">[</span><span class="p">_</span><span class="p">|</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="6282107381-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6282107381-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">find_phone</span><span class="p" data-group-id="6282107381-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6282107381-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">find_phone</span><span class="p" data-group-id="6282107381-8">(</span><span class="p" data-group-id="6282107381-9">[</span><span class="p" data-group-id="6282107381-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6282107381-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +phone number of a person with a particular name:</p><pre><code class="makeup erlang" translate="no"><span class="nf">find_phone</span><span class="p" data-group-id="5341987234-1">(</span><span class="p" data-group-id="5341987234-2">[</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5341987234-3">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="n">Phone</span><span class="p" data-group-id="5341987234-3">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="5341987234-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5341987234-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5341987234-4">{</span><span class="ss">found</span><span class="p">,</span><span class="w">  </span><span class="n">Phone</span><span class="p" data-group-id="5341987234-4">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">find_phone</span><span class="p" data-group-id="5341987234-5">(</span><span class="p" data-group-id="5341987234-6">[</span><span class="p">_</span><span class="p">|</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="5341987234-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5341987234-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">find_phone</span><span class="p" data-group-id="5341987234-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5341987234-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">find_phone</span><span class="p" data-group-id="5341987234-8">(</span><span class="p" data-group-id="5341987234-9">[</span><span class="p" data-group-id="5341987234-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5341987234-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">not_found</span><span class="p">.</span></code></pre><p>The fields referred to in the pattern can be given in any order.</p><h2 id="nested-records" class="section-heading">
│ │ │ │    <a href="#nested-records" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Nested Records</span>
│ │ │ │  </h2>
│ │ │ │  <p>The value of a field in a record can be an instance of a record. Retrieval of
│ │ │ │  nested data can be done stepwise, or in a single step, as shown in the following
│ │ │ │ -example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9301052604-1">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9301052604-2">{</span><span class="ss">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">last</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Ericsson&quot;</span><span class="p" data-group-id="9301052604-2">}</span><span class="p" data-group-id="9301052604-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9301052604-3">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9301052604-4">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">name</span><span class="p" data-group-id="9301052604-5">{</span><span class="p" data-group-id="9301052604-5">}</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p" data-group-id="9301052604-4">}</span><span class="p" data-group-id="9301052604-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8922526375-1">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8922526375-2">{</span><span class="ss">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">last</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Ericsson&quot;</span><span class="p" data-group-id="8922526375-2">}</span><span class="p" data-group-id="8922526375-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8922526375-3">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8922526375-4">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">name</span><span class="p" data-group-id="8922526375-5">{</span><span class="p" data-group-id="8922526375-5">}</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p" data-group-id="8922526375-4">}</span><span class="p" data-group-id="8922526375-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">demo</span><span class="p" data-group-id="9301052604-6">(</span><span class="p" data-group-id="9301052604-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -  </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9301052604-7">{</span><span class="ss">name</span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">name</span><span class="p" data-group-id="9301052604-8">{</span><span class="ss">first</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">last</span><span class="o">=</span><span class="s">&quot;Virding&quot;</span><span class="p" data-group-id="9301052604-8">}</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="mi">123</span><span class="p" data-group-id="9301052604-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="n">First</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9301052604-9">(</span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="9301052604-9">)</span><span class="o">#</span><span class="ss">name</span><span class="p">.</span><span class="ss">first</span><span class="p">.</span></code></pre><p>Here, <code class="inline">demo()</code> evaluates to <code class="inline">&quot;Robert&quot;</code>.</p><h2 id="a-longer-example" class="section-heading">
│ │ │ │ +</span><span class="nf">demo</span><span class="p" data-group-id="8922526375-6">(</span><span class="p" data-group-id="8922526375-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8922526375-7">{</span><span class="ss">name</span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">name</span><span class="p" data-group-id="8922526375-8">{</span><span class="ss">first</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">last</span><span class="o">=</span><span class="s">&quot;Virding&quot;</span><span class="p" data-group-id="8922526375-8">}</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="mi">123</span><span class="p" data-group-id="8922526375-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="n">First</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8922526375-9">(</span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="8922526375-9">)</span><span class="o">#</span><span class="ss">name</span><span class="p">.</span><span class="ss">first</span><span class="p">.</span></code></pre><p>Here, <code class="inline">demo()</code> evaluates to <code class="inline">&quot;Robert&quot;</code>.</p><h2 id="a-longer-example" class="section-heading">
│ │ │ │    <a href="#a-longer-example" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">A Longer Example</span>
│ │ │ │  </h2>
│ │ │ │  <p>Comments are embedded in the following example:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% File: person.hrl</span><span class="w">
│ │ │ │  
│ │ │ │ @@ -135,44 +135,44 @@
│ │ │ │  </span><span class="c1">%%    name:  A string (default is undefined).</span><span class="w">
│ │ │ │  </span><span class="c1">%%    age:   An integer (default is undefined).</span><span class="w">
│ │ │ │  </span><span class="c1">%%    phone: A list of integers (default is []).</span><span class="w">
│ │ │ │  </span><span class="c1">%%    dict:  A dictionary containing various information</span><span class="w">
│ │ │ │  </span><span class="c1">%%           about the person.</span><span class="w">
│ │ │ │  </span><span class="c1">%%           A {Key, Value} list (default is the empty list).</span><span class="w">
│ │ │ │  </span><span class="c1">%%------------------------------------------------------------</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5535421328-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5535421328-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5535421328-3">[</span><span class="p" data-group-id="5535421328-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5535421328-4">[</span><span class="p" data-group-id="5535421328-4">]</span><span class="p" data-group-id="5535421328-2">}</span><span class="p" data-group-id="5535421328-1">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9615411262-1">(</span><span class="ss">person</span><span class="p" data-group-id="9615411262-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="9615411262-2">(</span><span class="s">&quot;person.hrl&quot;</span><span class="p" data-group-id="9615411262-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="9615411262-3">(</span><span class="ss">export_all</span><span class="p" data-group-id="9615411262-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% For test purposes only.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5702750950-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5702750950-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5702750950-3">[</span><span class="p" data-group-id="5702750950-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5702750950-4">[</span><span class="p" data-group-id="5702750950-4">]</span><span class="p" data-group-id="5702750950-2">}</span><span class="p" data-group-id="5702750950-1">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7102748942-1">(</span><span class="ss">person</span><span class="p" data-group-id="7102748942-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="7102748942-2">(</span><span class="s">&quot;person.hrl&quot;</span><span class="p" data-group-id="7102748942-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="7102748942-3">(</span><span class="ss">export_all</span><span class="p" data-group-id="7102748942-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% For test purposes only.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% This creates an instance of a person.</span><span class="w">
│ │ │ │  </span><span class="c1">%%   Note: The phone number is not supplied so the</span><span class="w">
│ │ │ │  </span><span class="c1">%%         default value [] will be used.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">make_hacker_without_phone</span><span class="p" data-group-id="9615411262-4">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="9615411262-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9615411262-5">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w">
│ │ │ │ -           </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9615411262-6">[</span><span class="p" data-group-id="9615411262-7">{</span><span class="ss">computer_knowledge</span><span class="p">,</span><span class="w"> </span><span class="ss">excellent</span><span class="p" data-group-id="9615411262-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                   </span><span class="p" data-group-id="9615411262-8">{</span><span class="ss">drinks</span><span class="p">,</span><span class="w"> </span><span class="ss">coke</span><span class="p" data-group-id="9615411262-8">}</span><span class="p" data-group-id="9615411262-6">]</span><span class="p" data-group-id="9615411262-5">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">make_hacker_without_phone</span><span class="p" data-group-id="7102748942-4">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="7102748942-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7102748942-5">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w">
│ │ │ │ +           </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7102748942-6">[</span><span class="p" data-group-id="7102748942-7">{</span><span class="ss">computer_knowledge</span><span class="p">,</span><span class="w"> </span><span class="ss">excellent</span><span class="p" data-group-id="7102748942-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                   </span><span class="p" data-group-id="7102748942-8">{</span><span class="ss">drinks</span><span class="p">,</span><span class="w"> </span><span class="ss">coke</span><span class="p" data-group-id="7102748942-8">}</span><span class="p" data-group-id="7102748942-6">]</span><span class="p" data-group-id="7102748942-5">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% This demonstrates matching in arguments</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">print</span><span class="p" data-group-id="9615411262-9">(</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9615411262-10">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dict</span><span class="p" data-group-id="9615411262-10">}</span><span class="p" data-group-id="9615411262-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9615411262-11">(</span><span class="s">&quot;Name: </span><span class="si">~s</span><span class="s">, Age: </span><span class="si">~w</span><span class="s">, Phone: </span><span class="si">~w</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="w">
│ │ │ │ -            </span><span class="s">&quot;Dictionary: </span><span class="si">~w</span><span class="s">.</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9615411262-12">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="n">Dict</span><span class="p" data-group-id="9615411262-12">]</span><span class="p" data-group-id="9615411262-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">print</span><span class="p" data-group-id="7102748942-9">(</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7102748942-10">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dict</span><span class="p" data-group-id="7102748942-10">}</span><span class="p" data-group-id="7102748942-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7102748942-11">(</span><span class="s">&quot;Name: </span><span class="si">~s</span><span class="s">, Age: </span><span class="si">~w</span><span class="s">, Phone: </span><span class="si">~w</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="w">
│ │ │ │ +            </span><span class="s">&quot;Dictionary: </span><span class="si">~w</span><span class="s">.</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7102748942-12">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="n">Dict</span><span class="p" data-group-id="7102748942-12">]</span><span class="p" data-group-id="7102748942-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% Demonstrates type testing, selector, updating.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">birthday</span><span class="p" data-group-id="9615411262-13">(</span><span class="n">P</span><span class="p" data-group-id="9615411262-13">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="9615411262-14">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="9615411262-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9615411262-15">{</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="9615411262-15">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">birthday</span><span class="p" data-group-id="7102748942-13">(</span><span class="n">P</span><span class="p" data-group-id="7102748942-13">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="7102748942-14">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="7102748942-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7102748942-15">{</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="7102748942-15">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">register_two_hackers</span><span class="p" data-group-id="9615411262-16">(</span><span class="p" data-group-id="9615411262-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="n">Hacker1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_hacker_without_phone</span><span class="p" data-group-id="9615411262-17">(</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">29</span><span class="p" data-group-id="9615411262-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="n">OldHacker</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">birthday</span><span class="p" data-group-id="9615411262-18">(</span><span class="n">Hacker1</span><span class="p" data-group-id="9615411262-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">register_two_hackers</span><span class="p" data-group-id="7102748942-16">(</span><span class="p" data-group-id="7102748942-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="n">Hacker1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_hacker_without_phone</span><span class="p" data-group-id="7102748942-17">(</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">29</span><span class="p" data-group-id="7102748942-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="n">OldHacker</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">birthday</span><span class="p" data-group-id="7102748942-18">(</span><span class="n">Hacker1</span><span class="p" data-group-id="7102748942-18">)</span><span class="p">,</span><span class="w">
│ │ │ │     </span><span class="c1">% The central_register_server should have</span><span class="w">
│ │ │ │     </span><span class="c1">% an interface function for this.</span><span class="w">
│ │ │ │ -   </span><span class="ss">central_register_server</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9615411262-19">{</span><span class="ss">register_person</span><span class="p">,</span><span class="w"> </span><span class="n">Hacker1</span><span class="p" data-group-id="9615411262-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="ss">central_register_server</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9615411262-20">{</span><span class="ss">register_person</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="n">OldHacker</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9615411262-21">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -                              </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9615411262-22">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9615411262-22">]</span><span class="p" data-group-id="9615411262-21">}</span><span class="p" data-group-id="9615411262-20">}</span><span class="p">.</span></code></pre>
│ │ │ │ +   </span><span class="ss">central_register_server</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7102748942-19">{</span><span class="ss">register_person</span><span class="p">,</span><span class="w"> </span><span class="n">Hacker1</span><span class="p" data-group-id="7102748942-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="ss">central_register_server</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7102748942-20">{</span><span class="ss">register_person</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="n">OldHacker</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7102748942-21">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +                              </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7102748942-22">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="7102748942-22">]</span><span class="p" data-group-id="7102748942-21">}</span><span class="p" data-group-id="7102748942-20">}</span><span class="p">.</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/patterns.xhtml
│ │ │ │ @@ -33,16 +33,16 @@
│ │ │ │  succeeds, any unbound variables in the pattern become bound. If the matching
│ │ │ │  fails, an exception is raised.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** 1:1: variable &#39;X&#39; is unbound **</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">2</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">3&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="p" data-group-id="0306154154-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0306154154-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0306154154-2">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0306154154-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="p" data-group-id="0557462357-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0557462357-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0557462357-2">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0557462357-2">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no match of right hand side value {1,2}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="0306154154-3">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0306154154-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0306154154-4">{</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="0306154154-4">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0306154154-5">{</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0306154154-5">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="0557462357-3">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0557462357-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0557462357-4">{</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="0557462357-4">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0557462357-5">{</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0557462357-5">}</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">6&gt; </span><span class="n">Y</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/otp-patch-apply.xhtml
│ │ │ │ @@ -106,13 +106,13 @@
│ │ │ │    </a>
│ │ │ │    <span class="text">Sanity check</span>
│ │ │ │  </h2>
│ │ │ │  <p>The application dependencies can be checked using the Erlang shell.
│ │ │ │  Application dependencies are verified among installed applications by
│ │ │ │  <code class="inline">otp_patch_apply</code>, but these are not necessarily those actually loaded.
│ │ │ │  By calling <code class="inline">system_information:sanity_check()</code> one can validate
│ │ │ │ -dependencies among applications actually loaded.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">system_information</span><span class="p">:</span><span class="nf">sanity_check</span><span class="p" data-group-id="0433084684-1">(</span><span class="p" data-group-id="0433084684-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +dependencies among applications actually loaded.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">system_information</span><span class="p">:</span><span class="nf">sanity_check</span><span class="p" data-group-id="9490383800-1">(</span><span class="p" data-group-id="9490383800-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>Please take a look at the reference of <a href="../../../lib/runtime_tools/doc/html/system_information.html#sanity_check/0" title="">sanity_check()</a> for more
│ │ │ │  information.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/opaques.xhtml
│ │ │ │ @@ -29,24 +29,24 @@
│ │ │ │  <p>The main use case for opacity in Erlang is to hide the implementation of a data
│ │ │ │  type, enabling evolving the API while minimizing the risk of breaking consumers.
│ │ │ │  The runtime does not check opacity. Dialyzer provides some opacity-checking, but
│ │ │ │  the rest is up to convention.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Since Erlang/OTP 28, Dialyzer checks opaques in their defining module in the
│ │ │ │  same way as nominals. Outside of the defining module, Dialyzer checks
│ │ │ │  opaques for opacity violations.</p></section><p>This document explains what Erlang opacity is (and the trade-offs involved) via
│ │ │ │  the example of the <a href="../../../lib/stdlib/doc/html/sets.html#t:set/0"><code class="inline">sets:set()</code></a> data type. This type <em>was</em>
│ │ │ │ -defined in the <code class="inline">sets</code> module like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">set</span><span class="p" data-group-id="4728285444-1">(</span><span class="n">Element</span><span class="p" data-group-id="4728285444-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">set</span><span class="p" data-group-id="4728285444-2">{</span><span class="ss">segs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">segs</span><span class="p" data-group-id="4728285444-3">(</span><span class="n">Element</span><span class="p" data-group-id="4728285444-3">)</span><span class="p" data-group-id="4728285444-2">}</span><span class="p">.</span></code></pre><p>OTP 24 changed the definition to the following in
│ │ │ │ -<a href="https://github.com/erlang/otp/commit/e66941e8d7c47b973dff94c0308ea85a6be1958e">this commit</a>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">set</span><span class="p" data-group-id="6181180224-1">(</span><span class="n">Element</span><span class="p" data-group-id="6181180224-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">set</span><span class="p" data-group-id="6181180224-2">{</span><span class="ss">segs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">segs</span><span class="p" data-group-id="6181180224-3">(</span><span class="n">Element</span><span class="p" data-group-id="6181180224-3">)</span><span class="p" data-group-id="6181180224-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="6181180224-4">#{</span><span class="n">Element</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VALUE</span><span class="p" data-group-id="6181180224-4">}</span><span class="p">.</span></code></pre><p>And this change was safer and more backwards-compatible than if the type had
│ │ │ │ +defined in the <code class="inline">sets</code> module like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">set</span><span class="p" data-group-id="6387963394-1">(</span><span class="n">Element</span><span class="p" data-group-id="6387963394-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">set</span><span class="p" data-group-id="6387963394-2">{</span><span class="ss">segs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">segs</span><span class="p" data-group-id="6387963394-3">(</span><span class="n">Element</span><span class="p" data-group-id="6387963394-3">)</span><span class="p" data-group-id="6387963394-2">}</span><span class="p">.</span></code></pre><p>OTP 24 changed the definition to the following in
│ │ │ │ +<a href="https://github.com/erlang/otp/commit/e66941e8d7c47b973dff94c0308ea85a6be1958e">this commit</a>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">set</span><span class="p" data-group-id="0586235978-1">(</span><span class="n">Element</span><span class="p" data-group-id="0586235978-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">set</span><span class="p" data-group-id="0586235978-2">{</span><span class="ss">segs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">segs</span><span class="p" data-group-id="0586235978-3">(</span><span class="n">Element</span><span class="p" data-group-id="0586235978-3">)</span><span class="p" data-group-id="0586235978-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="0586235978-4">#{</span><span class="n">Element</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VALUE</span><span class="p" data-group-id="0586235978-4">}</span><span class="p">.</span></code></pre><p>And this change was safer and more backwards-compatible than if the type had
│ │ │ │  been defined with <code class="inline">-type</code> instead of <code class="inline">-opaque</code>. Here is why: when a module
│ │ │ │  defines an <code class="inline">-opaque</code>, the contract is that only the defining module should rely
│ │ │ │  on the definition of the type: no other modules should rely on the definition.</p><p>This means that code that pattern-matched on <code class="inline">set</code> as a record/tuple technically
│ │ │ │  broke the contract, and opted in to being potentially broken when the definition
│ │ │ │  of <code class="inline">set()</code> changed. Before OTP 24, this code printed <code class="inline">ok</code>. In OTP 24 it may
│ │ │ │ -error:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">sets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="0217016894-1">(</span><span class="p" data-group-id="0217016894-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="n">Set</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_tuple</span><span class="p" data-group-id="0217016894-2">(</span><span class="n">Set</span><span class="p" data-group-id="0217016894-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0217016894-3">(</span><span class="s">&quot;ok&quot;</span><span class="p" data-group-id="0217016894-3">)</span><span class="w">
│ │ │ │ +error:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">sets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="2262540726-1">(</span><span class="p" data-group-id="2262540726-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="n">Set</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_tuple</span><span class="p" data-group-id="2262540726-2">(</span><span class="n">Set</span><span class="p" data-group-id="2262540726-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2262540726-3">(</span><span class="s">&quot;ok&quot;</span><span class="p" data-group-id="2262540726-3">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p><strong>When working with an opaque defined in another module, here are some
│ │ │ │  recommendations:</strong></p><ul><li>Don't examine the underlying type using pattern-matching, guards, or functions
│ │ │ │  that reveal the type, such as <a href="../../../lib/../erts/doc/html/erlang.html#tuple_size/1"><code class="inline">tuple_size/1</code></a>. One exception
│ │ │ │  is that <code class="inline">=:=</code> and <code class="inline">=/=</code> can be used between two opaques with the same name, or
│ │ │ │  between an opaque and <code class="inline">any()</code>, as those comparisons do not reveal underlying
│ │ │ │  types.</li><li>Use functions provided by the module for working with the type. For
│ │ │ │  example, the <code class="inline">sets</code> module provides <a href="../../../lib/stdlib/doc/html/sets.html#new/0"><code class="inline">sets:new/0</code></a>, <a href="../../../lib/stdlib/doc/html/sets.html#add_element/2"><code class="inline">sets:add_element/2</code></a>,
│ │ │ ├── OEBPS/nominals.xhtml
│ │ │ │ @@ -28,55 +28,55 @@
│ │ │ │  </h2>
│ │ │ │  <p>For <a href="typespec.xhtml#type-declarations-of-user-defined-types">user-defined types</a>
│ │ │ │  defined with <code class="inline">-type</code>, the Erlang compiler will ignore their type names. This
│ │ │ │  means the Erlang compiler uses a structural type system. Two types are seen as
│ │ │ │  equivalent if their structures are the same. Type comparison is based on the
│ │ │ │  structures of the types, not on how the user explicitly defines them. In the
│ │ │ │  following example, <code class="inline">meter()</code> and <code class="inline">foot()</code> are equivalent, and neither differs
│ │ │ │ -from the basic type <code class="inline">integer()</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">meter</span><span class="p" data-group-id="7413349838-1">(</span><span class="p" data-group-id="7413349838-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="7413349838-2">(</span><span class="p" data-group-id="7413349838-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">foot</span><span class="p" data-group-id="7413349838-3">(</span><span class="p" data-group-id="7413349838-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="7413349838-4">(</span><span class="p" data-group-id="7413349838-4">)</span><span class="p">.</span></code></pre><p>Nominal typing is an alternative type system. Two nominal types are equivalent
│ │ │ │ +from the basic type <code class="inline">integer()</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">meter</span><span class="p" data-group-id="4011908018-1">(</span><span class="p" data-group-id="4011908018-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="4011908018-2">(</span><span class="p" data-group-id="4011908018-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">foot</span><span class="p" data-group-id="4011908018-3">(</span><span class="p" data-group-id="4011908018-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="4011908018-4">(</span><span class="p" data-group-id="4011908018-4">)</span><span class="p">.</span></code></pre><p>Nominal typing is an alternative type system. Two nominal types are equivalent
│ │ │ │  if and only if they are declared with the same type name. The syntax for
│ │ │ │  declaring nominal types is <code class="inline">-nominal</code>.</p><p>If <code class="inline">meter()</code> and <code class="inline">foot()</code> are defined as nominal types, they will no longer be
│ │ │ │  compatible. When a function expects type <code class="inline">meter()</code>, passing in type <code class="inline">foot()</code>
│ │ │ │ -will result in a warning raised by the type checker.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">meter</span><span class="p" data-group-id="3991933819-1">(</span><span class="p" data-group-id="3991933819-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3991933819-2">(</span><span class="p" data-group-id="3991933819-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">foot</span><span class="p" data-group-id="3991933819-3">(</span><span class="p" data-group-id="3991933819-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3991933819-4">(</span><span class="p" data-group-id="3991933819-4">)</span><span class="p">.</span></code></pre><p>The main use case of nominal types is to prevent accidental misuse of types with
│ │ │ │ +will result in a warning raised by the type checker.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">meter</span><span class="p" data-group-id="2628484010-1">(</span><span class="p" data-group-id="2628484010-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="2628484010-2">(</span><span class="p" data-group-id="2628484010-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">foot</span><span class="p" data-group-id="2628484010-3">(</span><span class="p" data-group-id="2628484010-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="2628484010-4">(</span><span class="p" data-group-id="2628484010-4">)</span><span class="p">.</span></code></pre><p>The main use case of nominal types is to prevent accidental misuse of types with
│ │ │ │  the same structure. Within OTP, nominal type-checking is done in Dialyzer. The
│ │ │ │  Erlang compiler does not perform nominal type-checking.</p><h2 id="nominal-type-checking-rules" class="section-heading">
│ │ │ │    <a href="#nominal-type-checking-rules" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Nominal Type-Checking Rules</span>
│ │ │ │  </h2>
│ │ │ │  <p>In general, if two nominal types have different names, and one is not derived
│ │ │ │  from the other, they are not compatible. Dialyzer's nominal type-checking
│ │ │ │ -aligns with the examples' expected results in this section.</p><p>If we continue from the example above:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">int_to_meter</span><span class="p" data-group-id="5976799922-1">(</span><span class="nf">integer</span><span class="p" data-group-id="5976799922-2">(</span><span class="p" data-group-id="5976799922-2">)</span><span class="p" data-group-id="5976799922-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">meter</span><span class="p" data-group-id="5976799922-3">(</span><span class="p" data-group-id="5976799922-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">int_to_meter</span><span class="p" data-group-id="5976799922-4">(</span><span class="n">X</span><span class="p" data-group-id="5976799922-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │ │ +aligns with the examples' expected results in this section.</p><p>If we continue from the example above:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">int_to_meter</span><span class="p" data-group-id="8643452909-1">(</span><span class="nf">integer</span><span class="p" data-group-id="8643452909-2">(</span><span class="p" data-group-id="8643452909-2">)</span><span class="p" data-group-id="8643452909-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">meter</span><span class="p" data-group-id="8643452909-3">(</span><span class="p" data-group-id="8643452909-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">int_to_meter</span><span class="p" data-group-id="8643452909-4">(</span><span class="n">X</span><span class="p" data-group-id="8643452909-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="5976799922-5">(</span><span class="p" data-group-id="5976799922-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">foot</span><span class="p" data-group-id="5976799922-6">(</span><span class="p" data-group-id="5976799922-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="5976799922-7">(</span><span class="p" data-group-id="5976799922-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">int_to_meter</span><span class="p" data-group-id="5976799922-8">(</span><span class="mi">24</span><span class="p" data-group-id="5976799922-8">)</span><span class="p">.</span></code></pre><p>A type checker that performs nominal type-checking should raise a warning.
│ │ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="8643452909-5">(</span><span class="p" data-group-id="8643452909-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">foot</span><span class="p" data-group-id="8643452909-6">(</span><span class="p" data-group-id="8643452909-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="8643452909-7">(</span><span class="p" data-group-id="8643452909-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">int_to_meter</span><span class="p" data-group-id="8643452909-8">(</span><span class="mi">24</span><span class="p" data-group-id="8643452909-8">)</span><span class="p">.</span></code></pre><p>A type checker that performs nominal type-checking should raise a warning.
│ │ │ │  According to the specification, <code class="inline">foo/0</code> should return a <code class="inline">foot()</code> type. However,
│ │ │ │  the function <code class="inline">int_to_meter/1</code> returns a <code class="inline">meter()</code> type, so <code class="inline">foo/0</code> will also
│ │ │ │  return a <code class="inline">meter()</code> type. Because <code class="inline">meter()</code> and <code class="inline">foot()</code> are incompatible
│ │ │ │  nominal types, Dialyzer raises the following warning for <code class="inline">foo/0</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">Invalid</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="ss">specification</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">function</span><span class="w"> </span><span class="ss">foo</span><span class="p">/</span><span class="mi">0</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="n">The</span><span class="w"> </span><span class="ss">success</span><span class="w"> </span><span class="ss">typing</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="1440105876-1">(</span><span class="p" data-group-id="1440105876-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1440105876-2">(</span><span class="nf">meter</span><span class="p" data-group-id="1440105876-3">(</span><span class="p" data-group-id="1440105876-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="1440105876-4">(</span><span class="p" data-group-id="1440105876-4">)</span><span class="p" data-group-id="1440105876-2">)</span><span class="w">
│ │ │ │ -</span><span class="n">But</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">spec</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="1440105876-5">(</span><span class="p" data-group-id="1440105876-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">foot</span><span class="p" data-group-id="1440105876-6">(</span><span class="p" data-group-id="1440105876-6">)</span><span class="w">
│ │ │ │ +</span><span class="n">The</span><span class="w"> </span><span class="ss">success</span><span class="w"> </span><span class="ss">typing</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="8256507495-1">(</span><span class="p" data-group-id="8256507495-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8256507495-2">(</span><span class="nf">meter</span><span class="p" data-group-id="8256507495-3">(</span><span class="p" data-group-id="8256507495-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="8256507495-4">(</span><span class="p" data-group-id="8256507495-4">)</span><span class="p" data-group-id="8256507495-2">)</span><span class="w">
│ │ │ │ +</span><span class="n">But</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">spec</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="8256507495-5">(</span><span class="p" data-group-id="8256507495-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">foot</span><span class="p" data-group-id="8256507495-6">(</span><span class="p" data-group-id="8256507495-6">)</span><span class="w">
│ │ │ │  </span><span class="n">The</span><span class="w"> </span><span class="ss">return</span><span class="w"> </span><span class="ss">types</span><span class="w"> </span><span class="ss">do</span><span class="w"> </span><span class="ow">not</span><span class="w"> </span><span class="ss">overlap</span></code></pre><p>On the other hand, a nominal type is compatible with a non-opaque, non-nominal
│ │ │ │  type with the same structure. This compatibility goes both ways, meaning that
│ │ │ │  passing a structural type when a nominal type is expected is allowed, and
│ │ │ │ -vice versa.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">qaz</span><span class="p" data-group-id="3333705593-1">(</span><span class="p" data-group-id="3333705593-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3333705593-2">(</span><span class="p" data-group-id="3333705593-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">qaz</span><span class="p" data-group-id="3333705593-3">(</span><span class="p" data-group-id="3333705593-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">int_to_meter</span><span class="p" data-group-id="3333705593-4">(</span><span class="mi">24</span><span class="p" data-group-id="3333705593-4">)</span><span class="p">.</span></code></pre><p>A type checker that performs nominal type-checking should not raise a warning
│ │ │ │ +vice versa.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">qaz</span><span class="p" data-group-id="3503824290-1">(</span><span class="p" data-group-id="3503824290-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3503824290-2">(</span><span class="p" data-group-id="3503824290-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">qaz</span><span class="p" data-group-id="3503824290-3">(</span><span class="p" data-group-id="3503824290-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">int_to_meter</span><span class="p" data-group-id="3503824290-4">(</span><span class="mi">24</span><span class="p" data-group-id="3503824290-4">)</span><span class="p">.</span></code></pre><p>A type checker that performs nominal type-checking should not raise a warning
│ │ │ │  in this case. The specification says that <code class="inline">qaz/0</code> should return an <code class="inline">integer()</code>
│ │ │ │  type. However, the function <code class="inline">int_to_meter/1</code> returns a <code class="inline">meter()</code> type, so
│ │ │ │  <code class="inline">qaz/0</code> will also return a <code class="inline">meter()</code> type. <code class="inline">integer()</code> is not a nominal type.
│ │ │ │  The structure of <code class="inline">meter()</code> is compatible with <code class="inline">integer()</code>. Dialyzer can
│ │ │ │  analyze the function above without raising a warning.</p><p>There is one exception where two nominal types with different names can be
│ │ │ │  compatible: when one is derived from the other. For nominal types <code class="inline">s()</code> and
│ │ │ │ -<code class="inline">t()</code>, <code class="inline">s()</code> can be derived from <code class="inline">t()</code> in the two following ways:</p><ol><li>If <code class="inline">s()</code> is directly derived from <code class="inline">t()</code>.</li></ol><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">s</span><span class="p" data-group-id="0784756074-1">(</span><span class="p" data-group-id="0784756074-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">t</span><span class="p" data-group-id="0784756074-2">(</span><span class="p" data-group-id="0784756074-2">)</span><span class="p">.</span></code></pre><ol start="2"><li>If <code class="inline">s()</code> is derived from other nominal types, which are derived from <code class="inline">t()</code>.</li></ol><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">s</span><span class="p" data-group-id="2581381738-1">(</span><span class="p" data-group-id="2581381738-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">nominal_1</span><span class="p" data-group-id="2581381738-2">(</span><span class="p" data-group-id="2581381738-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">nominal_1</span><span class="p" data-group-id="2581381738-3">(</span><span class="p" data-group-id="2581381738-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">nominal_2</span><span class="p" data-group-id="2581381738-4">(</span><span class="p" data-group-id="2581381738-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">nominal_2</span><span class="p" data-group-id="2581381738-5">(</span><span class="p" data-group-id="2581381738-5">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">t</span><span class="p" data-group-id="2581381738-6">(</span><span class="p" data-group-id="2581381738-6">)</span><span class="p">.</span></code></pre><p>In both cases, <code class="inline">s()</code> and <code class="inline">t()</code> are compatible nominal types even though they
│ │ │ │ +<code class="inline">t()</code>, <code class="inline">s()</code> can be derived from <code class="inline">t()</code> in the two following ways:</p><ol><li>If <code class="inline">s()</code> is directly derived from <code class="inline">t()</code>.</li></ol><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">s</span><span class="p" data-group-id="0656987912-1">(</span><span class="p" data-group-id="0656987912-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">t</span><span class="p" data-group-id="0656987912-2">(</span><span class="p" data-group-id="0656987912-2">)</span><span class="p">.</span></code></pre><ol start="2"><li>If <code class="inline">s()</code> is derived from other nominal types, which are derived from <code class="inline">t()</code>.</li></ol><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">s</span><span class="p" data-group-id="3313217332-1">(</span><span class="p" data-group-id="3313217332-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">nominal_1</span><span class="p" data-group-id="3313217332-2">(</span><span class="p" data-group-id="3313217332-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">nominal_1</span><span class="p" data-group-id="3313217332-3">(</span><span class="p" data-group-id="3313217332-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">nominal_2</span><span class="p" data-group-id="3313217332-4">(</span><span class="p" data-group-id="3313217332-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">nominal_2</span><span class="p" data-group-id="3313217332-5">(</span><span class="p" data-group-id="3313217332-5">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">t</span><span class="p" data-group-id="3313217332-6">(</span><span class="p" data-group-id="3313217332-6">)</span><span class="p">.</span></code></pre><p>In both cases, <code class="inline">s()</code> and <code class="inline">t()</code> are compatible nominal types even though they
│ │ │ │  have different names. Defining them in different modules does not affect
│ │ │ │  compatibility.</p><p>In summary, nominal type-checking rules are as follows:</p><p>A function that has a <code class="inline">-spec</code> that states an argument or a return type to be
│ │ │ │  nominal type <code class="inline">a/0</code> (or any other arity), accepts or may return:</p><ul><li>Nominal type <code class="inline">a/0</code></li><li>A compatible nominal type <code class="inline">b/0</code></li><li>A compatible structural type</li></ul><p>A function that has a <code class="inline">-spec</code> that states an argument or a return type to be a
│ │ │ │  structural type <code class="inline">b/0</code> (or any other arity), accepts or may return:</p><ul><li>A compatible structural type</li><li>A compatible nominal type</li></ul><p><strong>When deciding if a type should be nominal, here are some suggestions:</strong></p><ul><li>If there are other types in the same module with the same structure, and they
│ │ │ │  should never be mixed, all of them can benefit from being nominal types.</li><li>If a type represents a unit like meter, second, byte, and so on, defining it
│ │ │ │  as a nominal type is always more useful than <code class="inline">-type</code>. You get the nice
│ │ │ │  guarantee that you cannot mix them up with other units defined as nominal
│ │ │ ├── OEBPS/nif.xhtml
│ │ │ │ @@ -38,26 +38,26 @@
│ │ │ │    <span class="text">Erlang Program</span>
│ │ │ │  </h2>
│ │ │ │  <p>Even if all functions of a module are NIFs, an Erlang module is still needed for
│ │ │ │  two reasons:</p><ul><li>The NIF library must be explicitly loaded by Erlang code in the same module.</li><li>All NIFs of a module must have an Erlang implementation as well.</li></ul><p>Normally these are minimal stub implementations that throw an exception. But
│ │ │ │  they can also be used as fallback implementations for functions that do not have
│ │ │ │  native implementations on some architectures.</p><p>NIF libraries are loaded by calling <a href="../../../lib/../erts/doc/html/erlang.html#load_nif/2"><code class="inline">erlang:load_nif/2</code></a>, with the name of the
│ │ │ │  shared library as argument. The second argument can be any term that will be
│ │ │ │ -passed on to the library and used for initialization:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5113396171-1">(</span><span class="ss">complex6</span><span class="p" data-group-id="5113396171-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5113396171-2">(</span><span class="p" data-group-id="5113396171-3">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5113396171-3">]</span><span class="p" data-group-id="5113396171-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">nifs</span><span class="p" data-group-id="5113396171-4">(</span><span class="p" data-group-id="5113396171-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5113396171-5">]</span><span class="p" data-group-id="5113396171-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="5113396171-6">(</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5113396171-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="5113396171-7">(</span><span class="p" data-group-id="5113396171-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="5113396171-8">(</span><span class="s">&quot;./complex6_nif&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="5113396171-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="5113396171-9">(</span><span class="p">_</span><span class="n">X</span><span class="p" data-group-id="5113396171-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="5113396171-10">(</span><span class="ss">nif_library_not_loaded</span><span class="p" data-group-id="5113396171-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="5113396171-11">(</span><span class="p">_</span><span class="n">Y</span><span class="p" data-group-id="5113396171-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="5113396171-12">(</span><span class="ss">nif_library_not_loaded</span><span class="p" data-group-id="5113396171-12">)</span><span class="p">.</span></code></pre><p>Here, the directive <code class="inline">on_load</code> is used to get function <code class="inline">init</code> to be automatically
│ │ │ │ +passed on to the library and used for initialization:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4409946755-1">(</span><span class="ss">complex6</span><span class="p" data-group-id="4409946755-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4409946755-2">(</span><span class="p" data-group-id="4409946755-3">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4409946755-3">]</span><span class="p" data-group-id="4409946755-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">nifs</span><span class="p" data-group-id="4409946755-4">(</span><span class="p" data-group-id="4409946755-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4409946755-5">]</span><span class="p" data-group-id="4409946755-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="4409946755-6">(</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4409946755-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="4409946755-7">(</span><span class="p" data-group-id="4409946755-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="4409946755-8">(</span><span class="s">&quot;./complex6_nif&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="4409946755-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="4409946755-9">(</span><span class="p">_</span><span class="n">X</span><span class="p" data-group-id="4409946755-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="4409946755-10">(</span><span class="ss">nif_library_not_loaded</span><span class="p" data-group-id="4409946755-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="4409946755-11">(</span><span class="p">_</span><span class="n">Y</span><span class="p" data-group-id="4409946755-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="4409946755-12">(</span><span class="ss">nif_library_not_loaded</span><span class="p" data-group-id="4409946755-12">)</span><span class="p">.</span></code></pre><p>Here, the directive <code class="inline">on_load</code> is used to get function <code class="inline">init</code> to be automatically
│ │ │ │  called when the module is loaded. If <code class="inline">init</code> returns anything other than <code class="inline">ok</code>,
│ │ │ │  such when the loading of the NIF library fails in this example, the module is
│ │ │ │  unloaded and calls to functions within it, fail.</p><p>Loading the NIF library overrides the stub implementations and cause calls to
│ │ │ │  <code class="inline">foo</code> and <code class="inline">bar</code> to be dispatched to the NIF implementations instead.</p><h2 id="nif-library-code" class="section-heading">
│ │ │ │    <a href="#nif-library-code" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │ @@ -114,22 +114,22 @@
│ │ │ │    <a href="#running-the-example" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Running the Example</span>
│ │ │ │  </h2>
│ │ │ │  <p><em>Step 1.</em> Compile the C code:</p><pre><code class="text">unix&gt; gcc -o complex6_nif.so -fpic -shared complex.c complex6_nif.c
│ │ │ │  windows&gt; cl -LD -MD -Fe complex6_nif.dll complex.c complex6_nif.c</code></pre><p><em>Step 2:</em> Start Erlang and compile the Erlang code:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="ss">erl</span><span class="w">
│ │ │ │ -</span><span class="n">Erlang</span><span class="w"> </span><span class="n">R13B04</span><span class="w"> </span><span class="p" data-group-id="5582214221-1">(</span><span class="ss">erts</span><span class="o">-</span><span class="mf">5.7</span><span class="p">.</span><span class="mi">5</span><span class="p" data-group-id="5582214221-1">)</span><span class="w"> </span><span class="p" data-group-id="5582214221-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="5582214221-2">]</span><span class="w"> </span><span class="p" data-group-id="5582214221-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="5582214221-3">]</span><span class="w"> </span><span class="p" data-group-id="5582214221-4">[</span><span class="nc">rq</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="5582214221-4">]</span><span class="w"> </span><span class="p" data-group-id="5582214221-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="5582214221-5">]</span><span class="w"> </span><span class="p" data-group-id="5582214221-6">[</span><span class="ss">kernel</span><span class="o">-</span><span class="nc">poll</span><span class="p">:</span><span class="ss">false</span><span class="p" data-group-id="5582214221-6">]</span><span class="w">
│ │ │ │ +</span><span class="n">Erlang</span><span class="w"> </span><span class="n">R13B04</span><span class="w"> </span><span class="p" data-group-id="7077352246-1">(</span><span class="ss">erts</span><span class="o">-</span><span class="mf">5.7</span><span class="p">.</span><span class="mi">5</span><span class="p" data-group-id="7077352246-1">)</span><span class="w"> </span><span class="p" data-group-id="7077352246-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="7077352246-2">]</span><span class="w"> </span><span class="p" data-group-id="7077352246-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="7077352246-3">]</span><span class="w"> </span><span class="p" data-group-id="7077352246-4">[</span><span class="nc">rq</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="7077352246-4">]</span><span class="w"> </span><span class="p" data-group-id="7077352246-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="7077352246-5">]</span><span class="w"> </span><span class="p" data-group-id="7077352246-6">[</span><span class="ss">kernel</span><span class="o">-</span><span class="nc">poll</span><span class="p">:</span><span class="ss">false</span><span class="p" data-group-id="7077352246-6">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">7.5</span><span class="w">  </span><span class="p" data-group-id="5582214221-7">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="5582214221-7">)</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="5582214221-8">(</span><span class="ss">complex6</span><span class="p" data-group-id="5582214221-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5582214221-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex6</span><span class="p" data-group-id="5582214221-9">}</span></code></pre><p><em>Step 3:</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="0796141049-1">(</span><span class="mi">3</span><span class="p" data-group-id="0796141049-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">7.5</span><span class="w">  </span><span class="p" data-group-id="7077352246-7">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="7077352246-7">)</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="7077352246-8">(</span><span class="ss">complex6</span><span class="p" data-group-id="7077352246-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7077352246-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex6</span><span class="p" data-group-id="7077352246-9">}</span></code></pre><p><em>Step 3:</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="4970656048-1">(</span><span class="mi">3</span><span class="p" data-group-id="4970656048-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="0796141049-2">(</span><span class="mi">5</span><span class="p" data-group-id="0796141049-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="4970656048-2">(</span><span class="mi">5</span><span class="p" data-group-id="4970656048-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">10</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="0796141049-3">(</span><span class="s">&quot;not an integer&quot;</span><span class="p" data-group-id="0796141049-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="4970656048-3">(</span><span class="s">&quot;not an integer&quot;</span><span class="p" data-group-id="4970656048-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: bad argument
│ │ │ │       in function  complex6:foo/1
│ │ │ │          called as comlpex6:foo(&quot;not an integer&quot;)</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/modules.xhtml
│ │ │ │ @@ -23,20 +23,20 @@
│ │ │ │  <h2 id="module-syntax" class="section-heading">
│ │ │ │    <a href="#module-syntax" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Module Syntax</span>
│ │ │ │  </h2>
│ │ │ │  <p>Erlang code is divided into <em>modules</em>. A module consists of a sequence of
│ │ │ │ -attributes and function declarations, each terminated by a period (<code class="inline">.</code>).</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9039371184-1">(</span><span class="ss">m</span><span class="p" data-group-id="9039371184-1">)</span><span class="p">.</span><span class="w">          </span><span class="c1">% module attribute</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9039371184-2">(</span><span class="p" data-group-id="9039371184-3">[</span><span class="ss">fact</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9039371184-3">]</span><span class="p" data-group-id="9039371184-2">)</span><span class="p">.</span><span class="w">   </span><span class="c1">% module attribute</span><span class="w">
│ │ │ │ +attributes and function declarations, each terminated by a period (<code class="inline">.</code>).</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9637737765-1">(</span><span class="ss">m</span><span class="p" data-group-id="9637737765-1">)</span><span class="p">.</span><span class="w">          </span><span class="c1">% module attribute</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9637737765-2">(</span><span class="p" data-group-id="9637737765-3">[</span><span class="ss">fact</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9637737765-3">]</span><span class="p" data-group-id="9637737765-2">)</span><span class="p">.</span><span class="w">   </span><span class="c1">% module attribute</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="9039371184-4">(</span><span class="n">N</span><span class="p" data-group-id="9039371184-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="o">&gt;</span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% beginning of function declaration</span><span class="w">
│ │ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="9039371184-5">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="9039371184-5">)</span><span class="p">;</span><span class="w">   </span><span class="c1">%  |</span><span class="w">
│ │ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="9039371184-6">(</span><span class="mi">0</span><span class="p" data-group-id="9039371184-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">           </span><span class="c1">%  |</span><span class="w">
│ │ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="9637737765-4">(</span><span class="n">N</span><span class="p" data-group-id="9637737765-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="o">&gt;</span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% beginning of function declaration</span><span class="w">
│ │ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="9637737765-5">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="9637737765-5">)</span><span class="p">;</span><span class="w">   </span><span class="c1">%  |</span><span class="w">
│ │ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="9637737765-6">(</span><span class="mi">0</span><span class="p" data-group-id="9637737765-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">           </span><span class="c1">%  |</span><span class="w">
│ │ │ │      </span><span class="mi">1</span><span class="p">.</span><span class="w">               </span><span class="c1">% end of function declaration</span></code></pre><p>For a description of function declarations, see
│ │ │ │  <a href="ref_man_functions.xhtml">Function Declaration Syntax</a>.</p><h2 id="module-attributes" class="section-heading">
│ │ │ │    <a href="#module-attributes" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Module Attributes</span>
│ │ │ │  </h2>
│ │ │ │ @@ -81,71 +81,71 @@
│ │ │ │  meaning.</p></section></li></ul><h3 id="behaviour-module-attribute" class="section-heading">
│ │ │ │    <a href="#behaviour-module-attribute" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Behaviour Module Attribute</span>
│ │ │ │  </h3>
│ │ │ │  <p>It is possible to specify that the module is the callback module for a
│ │ │ │ -<em>behaviour</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="1043112993-1">(</span><span class="n">Behaviour</span><span class="p" data-group-id="1043112993-1">)</span><span class="p">.</span></code></pre><p>The atom <code class="inline">Behaviour</code> gives the name of the behaviour, which can be a
│ │ │ │ +<em>behaviour</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="4336374880-1">(</span><span class="n">Behaviour</span><span class="p" data-group-id="4336374880-1">)</span><span class="p">.</span></code></pre><p>The atom <code class="inline">Behaviour</code> gives the name of the behaviour, which can be a
│ │ │ │  user-defined behaviour or one of the following OTP standard behaviours:</p><ul><li><code class="inline">gen_server</code></li><li><code class="inline">gen_statem</code></li><li><code class="inline">gen_event</code></li><li><code class="inline">supervisor</code></li></ul><p>The spelling <code class="inline">behavior</code> is also accepted.</p><p>The callback functions of the module can be specified either directly by the
│ │ │ │ -exported function <code class="inline">behaviour_info/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">behaviour_info</span><span class="p" data-group-id="9841467886-1">(</span><span class="ss">callbacks</span><span class="p" data-group-id="9841467886-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Callbacks</span><span class="p">.</span></code></pre><p>or by a <code class="inline">-callback</code> attribute for each callback function:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="7970299491-1">(</span><span class="n">Arguments</span><span class="p" data-group-id="7970299491-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Result</span><span class="p">.</span></code></pre><p>Here, <code class="inline">Arguments</code> is a list of zero or more arguments. The <code class="inline">-callback</code> attribute
│ │ │ │ +exported function <code class="inline">behaviour_info/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">behaviour_info</span><span class="p" data-group-id="5755029876-1">(</span><span class="ss">callbacks</span><span class="p" data-group-id="5755029876-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Callbacks</span><span class="p">.</span></code></pre><p>or by a <code class="inline">-callback</code> attribute for each callback function:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="7348696095-1">(</span><span class="n">Arguments</span><span class="p" data-group-id="7348696095-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Result</span><span class="p">.</span></code></pre><p>Here, <code class="inline">Arguments</code> is a list of zero or more arguments. The <code class="inline">-callback</code> attribute
│ │ │ │  is to be preferred since the extra type information can be used by tools to
│ │ │ │  produce documentation or find discrepancies.</p><p>Read more about behaviours and callback modules in
│ │ │ │  <a href="../../../lib/../system/doc/html/design_principles.xhtml#behaviours">OTP Design Principles</a>.</p><h3 id="record-definitions" class="section-heading">
│ │ │ │    <a href="#record-definitions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Record Definitions</span>
│ │ │ │  </h3>
│ │ │ │ -<p>The same syntax as for module attributes is used for record definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8614425771-1">(</span><span class="n">Record</span><span class="p">,</span><span class="w"> </span><span class="n">Fields</span><span class="p" data-group-id="8614425771-1">)</span><span class="p">.</span></code></pre><p>Record definitions are allowed anywhere in a module, also among the function
│ │ │ │ +<p>The same syntax as for module attributes is used for record definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6799292401-1">(</span><span class="n">Record</span><span class="p">,</span><span class="w"> </span><span class="n">Fields</span><span class="p" data-group-id="6799292401-1">)</span><span class="p">.</span></code></pre><p>Record definitions are allowed anywhere in a module, also among the function
│ │ │ │  declarations. Read more in <a href="ref_man_records.xhtml">Records</a>.</p><h3 id="preprocessor" class="section-heading">
│ │ │ │    <a href="#preprocessor" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Preprocessor</span>
│ │ │ │  </h3>
│ │ │ │  <p>The same syntax as for module attributes is used by the preprocessor, which
│ │ │ │ -supports file inclusion, macros, and conditional compilation:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="4383023589-1">(</span><span class="s">&quot;SomeFile.hrl&quot;</span><span class="p" data-group-id="4383023589-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4383023589-2">(</span><span class="n">Macro</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="4383023589-2">)</span><span class="p">.</span></code></pre><p>Read more in <a href="macros.xhtml">Preprocessor</a>.</p><h3 id="setting-file-and-line" class="section-heading">
│ │ │ │ +supports file inclusion, macros, and conditional compilation:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="4889338055-1">(</span><span class="s">&quot;SomeFile.hrl&quot;</span><span class="p" data-group-id="4889338055-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4889338055-2">(</span><span class="n">Macro</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="4889338055-2">)</span><span class="p">.</span></code></pre><p>Read more in <a href="macros.xhtml">Preprocessor</a>.</p><h3 id="setting-file-and-line" class="section-heading">
│ │ │ │    <a href="#setting-file-and-line" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Setting File and Line</span>
│ │ │ │  </h3>
│ │ │ │  <p>The same syntax as for module attributes is used for changing the pre-defined
│ │ │ │ -macros <code class="inline">?FILE</code> and <code class="inline">?LINE</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">file</span><span class="p" data-group-id="7232167904-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">Line</span><span class="p" data-group-id="7232167904-1">)</span><span class="p">.</span></code></pre><p>This attribute is used by tools, such as Yecc, to inform the compiler that the
│ │ │ │ +macros <code class="inline">?FILE</code> and <code class="inline">?LINE</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">file</span><span class="p" data-group-id="8599835315-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">Line</span><span class="p" data-group-id="8599835315-1">)</span><span class="p">.</span></code></pre><p>This attribute is used by tools, such as Yecc, to inform the compiler that the
│ │ │ │  source program is generated by another tool. It also indicates the
│ │ │ │  correspondence of source files to lines of the original user-written file, from
│ │ │ │  which the source program is produced.</p><h3 id="types-and-function-specifications" class="section-heading">
│ │ │ │    <a href="#types-and-function-specifications" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Types and function specifications</span>
│ │ │ │  </h3>
│ │ │ │  <p>A syntax similar to that for module attributes is used for specifying types and
│ │ │ │ -function specifications:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">my_type</span><span class="p" data-group-id="5413466368-1">(</span><span class="p" data-group-id="5413466368-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="5413466368-2">(</span><span class="p" data-group-id="5413466368-2">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="5413466368-3">(</span><span class="p" data-group-id="5413466368-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">my_function</span><span class="p" data-group-id="5413466368-4">(</span><span class="nf">integer</span><span class="p" data-group-id="5413466368-5">(</span><span class="p" data-group-id="5413466368-5">)</span><span class="p" data-group-id="5413466368-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="5413466368-6">(</span><span class="p" data-group-id="5413466368-6">)</span><span class="p">.</span></code></pre><p>Read more in <a href="typespec.xhtml">Types and Function specifications</a>.</p><p>The description is based on
│ │ │ │ +function specifications:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">my_type</span><span class="p" data-group-id="3501393616-1">(</span><span class="p" data-group-id="3501393616-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="3501393616-2">(</span><span class="p" data-group-id="3501393616-2">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3501393616-3">(</span><span class="p" data-group-id="3501393616-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">my_function</span><span class="p" data-group-id="3501393616-4">(</span><span class="nf">integer</span><span class="p" data-group-id="3501393616-5">(</span><span class="p" data-group-id="3501393616-5">)</span><span class="p" data-group-id="3501393616-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3501393616-6">(</span><span class="p" data-group-id="3501393616-6">)</span><span class="p">.</span></code></pre><p>Read more in <a href="typespec.xhtml">Types and Function specifications</a>.</p><p>The description is based on
│ │ │ │  <a href="http://www.erlang.org/eeps/eep-0008.html">EEP8 - Types and function specifications</a>,
│ │ │ │  which is not to be further updated.</p><h3 id="documentation-attributes" class="section-heading">
│ │ │ │    <a href="#documentation-attributes" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Documentation attributes</span>
│ │ │ │  </h3>
│ │ │ │  <p>The module attribute <code class="inline">-doc(Documentation)</code> is used to provide user documentation
│ │ │ │ -for a function/type/callback:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="2541666232-1">(</span><span class="s">&quot;Example documentation&quot;</span><span class="p" data-group-id="2541666232-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">example</span><span class="p" data-group-id="2541666232-2">(</span><span class="p" data-group-id="2541666232-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The attribute should be placed just before the entity it documents. The
│ │ │ │ +for a function/type/callback:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="8632194463-1">(</span><span class="s">&quot;Example documentation&quot;</span><span class="p" data-group-id="8632194463-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">example</span><span class="p" data-group-id="8632194463-2">(</span><span class="p" data-group-id="8632194463-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The attribute should be placed just before the entity it documents. The
│ │ │ │  parentheses are optional around <code class="inline">Documentation</code>. The allowed values for
│ │ │ │  <code class="inline">Documentation</code> are:</p><ul><li><p><strong><a href="data_types.xhtml#string">literal string</a> or
│ │ │ │  <a href="expressions.xhtml#unicode-segments">utf-8 encoded binary string</a></strong> - The string
│ │ │ │  documenting the entity. Any literal string is allowed, so both
│ │ │ │  <a href="data_types.xhtml#tqstring">triple quoted strings</a> and
│ │ │ │  <a href="data_types.xhtml#sigil">sigils</a> that translate to literal strings can be used.
│ │ │ │ -The following examples are equivalent:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="2381405846-1">(</span><span class="s">&quot;Example \&quot;docs\&quot;&quot;</span><span class="p" data-group-id="2381405846-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="2381405846-2">(</span><span class="p" data-group-id="2381405846-3">&lt;&lt;</span><span class="s">&quot;Example \&quot;docs\&quot;&quot;</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="2381405846-3">&gt;&gt;</span><span class="p" data-group-id="2381405846-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +The following examples are equivalent:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="6095787827-1">(</span><span class="s">&quot;Example \&quot;docs\&quot;&quot;</span><span class="p" data-group-id="6095787827-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="6095787827-2">(</span><span class="p" data-group-id="6095787827-3">&lt;&lt;</span><span class="s">&quot;Example \&quot;docs\&quot;&quot;</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="6095787827-3">&gt;&gt;</span><span class="p" data-group-id="6095787827-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">~S/Example &quot;docs&quot;/</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="s">&quot;
│ │ │ │     Example &quot;</span><span class="ss">docs</span><span class="s">&quot;
│ │ │ │     &quot;</span><span class="s">&quot;&quot;</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">~B|Example &quot;docs&quot;|</span><span class="p">.</span></code></pre><p>For clarity it is recommended to use either normal <code class="inline">&quot;strings&quot;</code> or triple
│ │ │ │  quoted strings for documentation attributes.</p></li><li><p><strong><code class="inline">{file,</code> <a href="../../../lib/kernel/doc/html/file.html#t:name/0"><code class="inline">file:name/0</code></a> <code class="inline">}</code></strong> - Read the contents of filename and use
│ │ │ │  that as the documentation string.</p></li><li><p><strong><code class="inline">false</code></strong> - Set the current entity as hidden, that is, it should not be
│ │ │ │ @@ -158,15 +158,15 @@
│ │ │ │    <a href="#the-feature-directive" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">The feature directive</span>
│ │ │ │  </h2>
│ │ │ │  <p>While not a module attribute, but rather a directive (since it might affect
│ │ │ │  syntax), there is the <code class="inline">-feature(..)</code> directive used for enabling and disabling
│ │ │ │ -<a href="../../../lib/../system/doc/html/features.xhtml#features">features</a>.</p><p>The syntax is similar to that of an attribute, but has two arguments:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">feature</span><span class="p" data-group-id="7472463287-1">(</span><span class="n">FeatureName</span><span class="p">,</span><span class="w"> </span><span class="ss">enable</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">disable</span><span class="p" data-group-id="7472463287-1">)</span><span class="p">.</span></code></pre><p>Note that the <a href="macros.xhtml#feature-directive">feature directive</a> can only appear
│ │ │ │ +<a href="../../../lib/../system/doc/html/features.xhtml#features">features</a>.</p><p>The syntax is similar to that of an attribute, but has two arguments:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">feature</span><span class="p" data-group-id="1196351780-1">(</span><span class="n">FeatureName</span><span class="p">,</span><span class="w"> </span><span class="ss">enable</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">disable</span><span class="p" data-group-id="1196351780-1">)</span><span class="p">.</span></code></pre><p>Note that the <a href="macros.xhtml#feature-directive">feature directive</a> can only appear
│ │ │ │  in a prefix of the module.</p><h2 id="comments" class="section-heading">
│ │ │ │    <a href="#comments" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Comments</span>
│ │ │ │  </h2>
│ │ │ │  <p>Comments can be placed anywhere in a module except within strings and
│ │ │ ├── OEBPS/maps.xhtml
│ │ │ │ @@ -53,16 +53,16 @@
│ │ │ │  single function that constructs the map using the map syntax and always use
│ │ │ │  it.</p></li><li><p>Always update the map using the <code class="inline">:=</code> operator (that is, requiring that an
│ │ │ │  element with that key already exists). The <code class="inline">:=</code> operator is slightly more
│ │ │ │  efficient, and it helps catch misspellings of keys.</p></li><li><p>Whenever possible, match multiple map elements at once.</p></li><li><p>Whenever possible, update multiple map elements at once.</p></li><li><p>Avoid default values and the <a href="../../../lib/stdlib/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a> function. If there are default
│ │ │ │  values, sharing of keys between different instances of the map will be less
│ │ │ │  effective, and it is not possible to match multiple elements having default
│ │ │ │  values in one go.</p></li><li><p>To avoid having to deal with a map that may lack some keys, <a href="../../../lib/stdlib/doc/html/maps.html#merge/2"><code class="inline">maps:merge/2</code></a> can
│ │ │ │ -efficiently add multiple default values. For example:</p><pre><code class="makeup erlang" translate="no"><span class="n">DefaultMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0271028008-1">#{</span><span class="ss">shoe_size</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w"> </span><span class="ss">editor</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">emacs</span><span class="p" data-group-id="0271028008-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">MapWithDefaultsApplied</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">merge</span><span class="p" data-group-id="0271028008-2">(</span><span class="n">DefaultMap</span><span class="p">,</span><span class="w"> </span><span class="n">OtherMap</span><span class="p" data-group-id="0271028008-2">)</span></code></pre></li></ul><h2 id="using-maps-as-dictionaries" class="section-heading">
│ │ │ │ +efficiently add multiple default values. For example:</p><pre><code class="makeup erlang" translate="no"><span class="n">DefaultMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9194698261-1">#{</span><span class="ss">shoe_size</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w"> </span><span class="ss">editor</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">emacs</span><span class="p" data-group-id="9194698261-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">MapWithDefaultsApplied</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">merge</span><span class="p" data-group-id="9194698261-2">(</span><span class="n">DefaultMap</span><span class="p">,</span><span class="w"> </span><span class="n">OtherMap</span><span class="p" data-group-id="9194698261-2">)</span></code></pre></li></ul><h2 id="using-maps-as-dictionaries" class="section-heading">
│ │ │ │    <a href="#using-maps-as-dictionaries" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Using Maps as Dictionaries</span>
│ │ │ │  </h2>
│ │ │ │  <p>Using a map as a dictionary implies the following usage pattern:</p><ul><li>Keys are usually variables not known at compile-time.</li><li>There can be any number of elements in the map.</li><li>Usually, no more than one element is looked up or updated at once.</li></ul><p>Given that usage pattern, the difference in performance between using the map
│ │ │ │  syntax and the maps module is usually small. Therefore, which one to use is
│ │ │ │ @@ -72,18 +72,18 @@
│ │ │ │  choice.</li></ul><h2 id="using-maps-as-sets" class="section-heading">
│ │ │ │    <a href="#using-maps-as-sets" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Using Maps as Sets</span>
│ │ │ │  </h2>
│ │ │ │  <p>Starting in OTP 24, the <a href="../../../lib/stdlib/doc/html/sets.html"><code class="inline">sets</code></a> module has an option to represent sets as maps.
│ │ │ │ -Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">sets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="1307664855-1">(</span><span class="p" data-group-id="1307664855-2">[</span><span class="p" data-group-id="1307664855-3">{</span><span class="ss">version</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1307664855-3">}</span><span class="p" data-group-id="1307664855-2">]</span><span class="p" data-group-id="1307664855-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1307664855-4">#{</span><span class="p" data-group-id="1307664855-4">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">sets</span><span class="p">:</span><span class="nf">from_list</span><span class="p" data-group-id="1307664855-5">(</span><span class="p" data-group-id="1307664855-6">[</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="1307664855-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1307664855-7">[</span><span class="p" data-group-id="1307664855-8">{</span><span class="ss">version</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1307664855-8">}</span><span class="p" data-group-id="1307664855-7">]</span><span class="p" data-group-id="1307664855-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1307664855-9">#{</span><span class="ss">x</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1307664855-10">[</span><span class="p" data-group-id="1307664855-10">]</span><span class="p">,</span><span class="ss">y</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1307664855-11">[</span><span class="p" data-group-id="1307664855-11">]</span><span class="p">,</span><span class="ss">z</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1307664855-12">[</span><span class="p" data-group-id="1307664855-12">]</span><span class="p" data-group-id="1307664855-9">}</span></code></pre><p><code class="inline">sets</code> backed by maps is generally the most efficient set representation, with a
│ │ │ │ +Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">sets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="1178419318-1">(</span><span class="p" data-group-id="1178419318-2">[</span><span class="p" data-group-id="1178419318-3">{</span><span class="ss">version</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1178419318-3">}</span><span class="p" data-group-id="1178419318-2">]</span><span class="p" data-group-id="1178419318-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1178419318-4">#{</span><span class="p" data-group-id="1178419318-4">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">sets</span><span class="p">:</span><span class="nf">from_list</span><span class="p" data-group-id="1178419318-5">(</span><span class="p" data-group-id="1178419318-6">[</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="1178419318-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1178419318-7">[</span><span class="p" data-group-id="1178419318-8">{</span><span class="ss">version</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1178419318-8">}</span><span class="p" data-group-id="1178419318-7">]</span><span class="p" data-group-id="1178419318-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1178419318-9">#{</span><span class="ss">x</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1178419318-10">[</span><span class="p" data-group-id="1178419318-10">]</span><span class="p">,</span><span class="ss">y</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1178419318-11">[</span><span class="p" data-group-id="1178419318-11">]</span><span class="p">,</span><span class="ss">z</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1178419318-12">[</span><span class="p" data-group-id="1178419318-12">]</span><span class="p" data-group-id="1178419318-9">}</span></code></pre><p><code class="inline">sets</code> backed by maps is generally the most efficient set representation, with a
│ │ │ │  few possible exceptions:</p><ul><li><a href="../../../lib/stdlib/doc/html/ordsets.html#intersection/2"><code class="inline">ordsets:intersection/2</code></a> can be more efficient than <a href="../../../lib/stdlib/doc/html/sets.html#intersection/2"><code class="inline">sets:intersection/2</code></a>. If
│ │ │ │  the intersection operation is frequently used and operations that operate on a
│ │ │ │  single element in a set (such as <code class="inline">is_element/2</code>) are avoided, <a href="../../../lib/stdlib/doc/html/ordsets.html"><code class="inline">ordsets</code></a> can
│ │ │ │  be a better choice than <a href="../../../lib/stdlib/doc/html/sets.html"><code class="inline">sets</code></a>.</li><li>If the intersection operation is frequently used and operations that operate
│ │ │ │  on a single element in a set (such as <code class="inline">is_element/2</code>) must also be efficient,
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gb_sets.html"><code class="inline">gb_sets</code></a> can potentially be a better choice than <a href="../../../lib/stdlib/doc/html/sets.html"><code class="inline">sets</code></a>.</li><li>If the elements of the set are integers in a fairly compact range, the set can
│ │ │ │  be represented as an integer where each bit represents an element in the set.
│ │ │ │ @@ -108,18 +108,18 @@
│ │ │ │  for the runtime system).</p></li><li><p><strong>N</strong> - The number of elements in the map.</p></li><li><p><strong>Keys</strong> - A tuple with keys of the map: <code class="inline">{Key1,...,KeyN}</code>. The keys are
│ │ │ │  sorted.</p></li><li><p><strong>Value1</strong> - The value corresponding to the first key in the key tuple.</p></li><li><p><strong>ValueN</strong> - The value corresponding to the last key in the key tuple.</p></li></ul><p>As an example, let us look at how the map <code class="inline">#{a =&gt; foo, z =&gt; bar}</code> is
│ │ │ │  represented:</p><table><thead><tr><th style="text-align: center;">0</th><th style="text-align: left;">1</th><th style="text-align: center;">2</th><th style="text-align: center;">3</th><th style="text-align: left;">4</th></tr></thead><tbody><tr><td style="text-align: center;"><strong>FLATMAP</strong></td><td style="text-align: left;">2</td><td style="text-align: center;"><code class="inline">{a,z}</code></td><td style="text-align: center;"><code class="inline">foo</code></td><td style="text-align: left;"><code class="inline">bar</code></td></tr></tbody></table><p><em>Table: #{a =&gt; foo, z =&gt; bar}</em></p><p>Let us update the map: <code class="inline">M#{q =&gt; baz}</code>. The map now looks like this:</p><table><thead><tr><th style="text-align: center;">0</th><th style="text-align: left;">1</th><th style="text-align: center;">2</th><th style="text-align: center;">3</th><th style="text-align: center;">4</th><th style="text-align: center;">5</th></tr></thead><tbody><tr><td style="text-align: center;"><strong>FLATMAP</strong></td><td style="text-align: left;">3</td><td style="text-align: center;"><code class="inline">{a,q,z}</code></td><td style="text-align: center;"><code class="inline">foo</code></td><td style="text-align: center;"><code class="inline">baz</code></td><td style="text-align: center;"><code class="inline">bar</code></td></tr></tbody></table><p><em>Table: #{a =&gt; foo, q =&gt; baz, z =&gt; bar}</em></p><p>Finally, change the value of one element: <code class="inline">M#{z := bird}</code>. The map now looks
│ │ │ │  like this:</p><table><thead><tr><th style="text-align: center;">0</th><th style="text-align: left;">1</th><th style="text-align: center;">2</th><th style="text-align: center;">3</th><th style="text-align: center;">4</th><th style="text-align: center;">5</th></tr></thead><tbody><tr><td style="text-align: center;"><strong>FLATMAP</strong></td><td style="text-align: left;">3</td><td style="text-align: center;"><code class="inline">{a,q,z}</code></td><td style="text-align: center;"><code class="inline">foo</code></td><td style="text-align: center;"><code class="inline">baz</code></td><td style="text-align: center;"><code class="inline">bird</code></td></tr></tbody></table><p><em>Table: #{a =&gt; foo, q =&gt; baz, z =&gt; bird}</em></p><p>When the value for an existing key is updated, the key tuple is not updated,
│ │ │ │  allowing the key tuple to be shared with other instances of the map that have
│ │ │ │  the same keys. In fact, the key tuple can be shared between all maps with the
│ │ │ │  same keys with some care. To arrange that, define a function that returns a map.
│ │ │ │ -For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">new</span><span class="p" data-group-id="5330021407-1">(</span><span class="p" data-group-id="5330021407-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5330021407-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p" data-group-id="5330021407-2">}</span><span class="p">.</span></code></pre><p>Defined like this, the key tuple <code class="inline">{a,b,c}</code> will be a global literal. To ensure
│ │ │ │ +For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">new</span><span class="p" data-group-id="8743050349-1">(</span><span class="p" data-group-id="8743050349-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8743050349-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p" data-group-id="8743050349-2">}</span><span class="p">.</span></code></pre><p>Defined like this, the key tuple <code class="inline">{a,b,c}</code> will be a global literal. To ensure
│ │ │ │  that the key tuple is shared when creating an instance of the map, always call
│ │ │ │ -<code class="inline">new()</code> and modify the returned map:</p><pre><code class="makeup erlang" translate="no"><span class="w">    </span><span class="p" data-group-id="9691728397-1">(</span><span class="n">SOME_MODULE</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="9691728397-2">(</span><span class="p" data-group-id="9691728397-2">)</span><span class="p" data-group-id="9691728397-1">)</span><span class="p" data-group-id="9691728397-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="9691728397-3">}</span><span class="p">.</span></code></pre><p>Using the map syntax with small maps is particularly efficient. As long as the
│ │ │ │ +<code class="inline">new()</code> and modify the returned map:</p><pre><code class="makeup erlang" translate="no"><span class="w">    </span><span class="p" data-group-id="8977687594-1">(</span><span class="n">SOME_MODULE</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="8977687594-2">(</span><span class="p" data-group-id="8977687594-2">)</span><span class="p" data-group-id="8977687594-1">)</span><span class="p" data-group-id="8977687594-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="8977687594-3">}</span><span class="p">.</span></code></pre><p>Using the map syntax with small maps is particularly efficient. As long as the
│ │ │ │  keys are known at compile-time, the map is updated in one go, making the time to
│ │ │ │  update a map essentially constant regardless of the number of keys updated. The
│ │ │ │  same goes for matching. (When the keys are variables, one or more of the keys
│ │ │ │  could be identical, so the operations need to be performed sequentially from
│ │ │ │  left to right.)</p><p>The memory size for a small map is the size of all keys and values plus 5 words.
│ │ │ │  See <a href="memory.xhtml">Memory</a> for more information about memory sizes.</p><h3 id="how-large-maps-are-implemented" class="section-heading">
│ │ │ │    <a href="#how-large-maps-are-implemented" class="hover-link">
│ │ │ │ @@ -146,21 +146,21 @@
│ │ │ │    <a href="#using-the-map-syntax" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Using the Map Syntax</span>
│ │ │ │  </h2>
│ │ │ │  <p>Using the map syntax is usually slightly more efficient than using the
│ │ │ │  corresponding function in the <a href="../../../lib/stdlib/doc/html/maps.html"><code class="inline">maps</code></a> module.</p><p>The gain in efficiency for the map syntax is more noticeable for the following
│ │ │ │ -operations that can only be achieved using the map syntax:</p><ul><li>Matching multiple literal keys</li><li>Updating multiple literal keys</li><li>Adding multiple literal keys to a map</li></ul><p>For example:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="7949661976-1">#{</span><span class="ss">x</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="ss">z</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="7949661976-1">}</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="4812508462-1">(</span><span class="ss">x</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="4812508462-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Map3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="4812508462-2">(</span><span class="ss">y</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="4812508462-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="4812508462-3">(</span><span class="ss">z</span><span class="p">,</span><span class="w"> </span><span class="n">Z</span><span class="p">,</span><span class="w"> </span><span class="n">Map3</span><span class="p" data-group-id="4812508462-3">)</span></code></pre><p>If the map is a small map, the first example runs roughly three times as fast.</p><p>Note that for variable keys, the elements are updated sequentially from left to
│ │ │ │ -right. For example, given the following update with variable keys:</p><pre><code class="makeup erlang" translate="no"><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="0335926840-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Key3</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="0335926840-1">}</span></code></pre><p>the compiler rewrites it like this to ensure that the updates are applied from
│ │ │ │ -left to right:</p><pre><code class="makeup erlang" translate="no"><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="9940929681-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9940929681-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Map3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="9940929681-2">#{</span><span class="n">Key2</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9940929681-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map3</span><span class="p" data-group-id="9940929681-3">#{</span><span class="n">Key3</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="9940929681-3">}</span></code></pre><p>If a key is known to exist in a map, using the <code class="inline">:=</code> operator is slightly more
│ │ │ │ +operations that can only be achieved using the map syntax:</p><ul><li>Matching multiple literal keys</li><li>Updating multiple literal keys</li><li>Adding multiple literal keys to a map</li></ul><p>For example:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="8745756480-1">#{</span><span class="ss">x</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="ss">z</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="8745756480-1">}</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="7669781837-1">(</span><span class="ss">x</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="7669781837-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Map3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="7669781837-2">(</span><span class="ss">y</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="7669781837-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="7669781837-3">(</span><span class="ss">z</span><span class="p">,</span><span class="w"> </span><span class="n">Z</span><span class="p">,</span><span class="w"> </span><span class="n">Map3</span><span class="p" data-group-id="7669781837-3">)</span></code></pre><p>If the map is a small map, the first example runs roughly three times as fast.</p><p>Note that for variable keys, the elements are updated sequentially from left to
│ │ │ │ +right. For example, given the following update with variable keys:</p><pre><code class="makeup erlang" translate="no"><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="3616583606-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Key3</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="3616583606-1">}</span></code></pre><p>the compiler rewrites it like this to ensure that the updates are applied from
│ │ │ │ +left to right:</p><pre><code class="makeup erlang" translate="no"><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="6566024656-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="6566024656-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Map3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="6566024656-2">#{</span><span class="n">Key2</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6566024656-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map3</span><span class="p" data-group-id="6566024656-3">#{</span><span class="n">Key3</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="6566024656-3">}</span></code></pre><p>If a key is known to exist in a map, using the <code class="inline">:=</code> operator is slightly more
│ │ │ │  efficient than using the <code class="inline">=&gt;</code> operator for a small map.</p><h2 id="using-the-functions-in-the-maps-module" class="section-heading">
│ │ │ │    <a href="#using-the-functions-in-the-maps-module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Using the Functions in the maps Module</span>
│ │ │ │  </h2>
│ │ │ │  <p>Here follows some notes about most of the functions in the <code class="inline">maps</code> module. For
│ │ │ │ @@ -211,23 +211,23 @@
│ │ │ │    <a href="#maps-get-3" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">maps:get/3</span>
│ │ │ │  </h3>
│ │ │ │  <p>As an optimization, the compiler will rewrite a call to <a href="../../../lib/stdlib/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a> to Erlang
│ │ │ │  code similar to the following:</p><pre><code class="makeup erlang" translate="no"><span class="n">Result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">Map</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="3288802230-1">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="3288802230-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Value</span><span class="p">;</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="3288802230-2">#{</span><span class="p" data-group-id="3288802230-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Default</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="7840314789-1">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="7840314789-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Value</span><span class="p">;</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="7840314789-2">#{</span><span class="p" data-group-id="7840314789-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Default</span><span class="w">
│ │ │ │           </span><span class="k">end</span></code></pre><p>This is reasonably efficient, but if a small map is used as an alternative to
│ │ │ │  using a record it is often better not to rely on default values as it prevents
│ │ │ │  sharing of keys, which may in the end use more memory than what you save from
│ │ │ │  not storing default values in the map.</p><p>If default values are nevertheless required, instead of calling <a href="../../../lib/stdlib/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a>
│ │ │ │  multiple times, consider putting the default values in a map and merging that
│ │ │ │ -map with the other map:</p><pre><code class="makeup erlang" translate="no"><span class="n">DefaultMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5212442160-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Value2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Value2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">KeyN</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">ValueN</span><span class="p" data-group-id="5212442160-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">MapWithDefaultsApplied</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">merge</span><span class="p" data-group-id="5212442160-2">(</span><span class="n">DefaultMap</span><span class="p">,</span><span class="w"> </span><span class="n">OtherMap</span><span class="p" data-group-id="5212442160-2">)</span></code></pre><p>This helps share keys between the default map and the one you applied defaults
│ │ │ │ +map with the other map:</p><pre><code class="makeup erlang" translate="no"><span class="n">DefaultMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1703192623-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Value2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Value2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">KeyN</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">ValueN</span><span class="p" data-group-id="1703192623-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">MapWithDefaultsApplied</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">merge</span><span class="p" data-group-id="1703192623-2">(</span><span class="n">DefaultMap</span><span class="p">,</span><span class="w"> </span><span class="n">OtherMap</span><span class="p" data-group-id="1703192623-2">)</span></code></pre><p>This helps share keys between the default map and the one you applied defaults
│ │ │ │  to, as long as the default map contains <em>all</em> the keys that will ever be used
│ │ │ │  and not just the ones with default values. Whether this is faster than calling
│ │ │ │  <a href="../../../lib/stdlib/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a> multiple times depends on the size of the map and the number of
│ │ │ │  default values.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before OTP 26.0 <a href="../../../lib/stdlib/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a> was implemented by calling the function instead
│ │ │ │  of rewriting it as an Erlang expression. It is now slightly faster but can no
│ │ │ │  longer be traced.</p></section><h3 id="maps-intersect-2-maps-intersect_with-3" class="section-heading">
│ │ │ │    <a href="#maps-intersect-2-maps-intersect_with-3" class="hover-link">
│ │ │ │ @@ -315,29 +315,29 @@
│ │ │ │    <a href="#maps-put-3" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">maps:put/3</span>
│ │ │ │  </h3>
│ │ │ │  <p><a href="../../../lib/stdlib/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a> is implemented in C.</p><p>If the key is known to already exist in the map, <a href="../../../lib/stdlib/doc/html/maps.html#update/3"><code class="inline">maps:update/3</code></a> is slightly
│ │ │ │  more efficient than <a href="../../../lib/stdlib/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a>.</p><p>If the compiler can determine that the third argument is always a map, it
│ │ │ │ -will rewrite the call to <a href="../../../lib/stdlib/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a> to use the map syntax for updating the map.</p><p>For example, consider the following function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_to_known_map</span><span class="p" data-group-id="3218220567-1">(</span><span class="n">Map0</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="3218220567-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_map</span><span class="p" data-group-id="3218220567-2">(</span><span class="n">Map0</span><span class="p" data-group-id="3218220567-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Map1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="3218220567-3">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">Map0</span><span class="p" data-group-id="3218220567-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="3218220567-4">(</span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="3218220567-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="3218220567-5">(</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="3218220567-5">)</span><span class="p">.</span></code></pre><p>The compiler first rewrites each call to <a href="../../../lib/stdlib/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a> to use the map
│ │ │ │ +will rewrite the call to <a href="../../../lib/stdlib/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a> to use the map syntax for updating the map.</p><p>For example, consider the following function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_to_known_map</span><span class="p" data-group-id="9100219170-1">(</span><span class="n">Map0</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="9100219170-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_map</span><span class="p" data-group-id="9100219170-2">(</span><span class="n">Map0</span><span class="p" data-group-id="9100219170-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Map1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="9100219170-3">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">Map0</span><span class="p" data-group-id="9100219170-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="9100219170-4">(</span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="9100219170-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="9100219170-5">(</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="9100219170-5">)</span><span class="p">.</span></code></pre><p>The compiler first rewrites each call to <a href="../../../lib/stdlib/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a> to use the map
│ │ │ │  syntax, and subsequently combines the three update operations to a
│ │ │ │ -single update operation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_to_known_map</span><span class="p" data-group-id="5776428455-1">(</span><span class="n">Map0</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="5776428455-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_map</span><span class="p" data-group-id="5776428455-2">(</span><span class="n">Map0</span><span class="p" data-group-id="5776428455-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Map0</span><span class="p" data-group-id="5776428455-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="5776428455-3">}</span><span class="p">.</span></code></pre><p>If the compiler cannot determine that the third argument is always a
│ │ │ │ +single update operation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_to_known_map</span><span class="p" data-group-id="3403354567-1">(</span><span class="n">Map0</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="3403354567-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_map</span><span class="p" data-group-id="3403354567-2">(</span><span class="n">Map0</span><span class="p" data-group-id="3403354567-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Map0</span><span class="p" data-group-id="3403354567-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="3403354567-3">}</span><span class="p">.</span></code></pre><p>If the compiler cannot determine that the third argument is always a
│ │ │ │  map, it retains the <a href="../../../lib/stdlib/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a> call. For example, given this
│ │ │ │ -function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_to_map</span><span class="p" data-group-id="1365279866-1">(</span><span class="n">Map0</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="1365279866-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Map1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="1365279866-2">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">Map0</span><span class="p" data-group-id="1365279866-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="1365279866-3">(</span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="1365279866-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="1365279866-4">(</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="1365279866-4">)</span><span class="p">.</span></code></pre><p>the compiler keeps the first call to <a href="../../../lib/stdlib/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a>, but rewrites
│ │ │ │ -and combines the other two calls:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_to_map</span><span class="p" data-group-id="3895245215-1">(</span><span class="n">Map0</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="3895245215-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Map1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="3895245215-2">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">Map0</span><span class="p" data-group-id="3895245215-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Map1</span><span class="p" data-group-id="3895245215-3">#{</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="3895245215-3">}</span><span class="p">.</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>The rewriting of <a href="../../../lib/stdlib/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a> to the map syntax was introduced in
│ │ │ │ +function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_to_map</span><span class="p" data-group-id="6768946492-1">(</span><span class="n">Map0</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="6768946492-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Map1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="6768946492-2">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">Map0</span><span class="p" data-group-id="6768946492-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="6768946492-3">(</span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="6768946492-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="6768946492-4">(</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="6768946492-4">)</span><span class="p">.</span></code></pre><p>the compiler keeps the first call to <a href="../../../lib/stdlib/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a>, but rewrites
│ │ │ │ +and combines the other two calls:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_to_map</span><span class="p" data-group-id="7280330482-1">(</span><span class="n">Map0</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="7280330482-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Map1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="7280330482-2">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">Map0</span><span class="p" data-group-id="7280330482-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Map1</span><span class="p" data-group-id="7280330482-3">#{</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="7280330482-3">}</span><span class="p">.</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>The rewriting of <a href="../../../lib/stdlib/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a> to the map syntax was introduced in
│ │ │ │  Erlang/OTP 28.</p></section><h3 id="maps-remove-2" class="section-heading">
│ │ │ │    <a href="#maps-remove-2" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">maps:remove/2</span>
│ │ │ │  </h3>
│ │ │ │  <p><a href="../../../lib/stdlib/doc/html/maps.html#remove/2"><code class="inline">maps:remove/2</code></a> is implemented in C.</p><h3 id="maps-size-1" class="section-heading">
│ │ │ ├── OEBPS/macros.xhtml
│ │ │ │ @@ -22,56 +22,56 @@
│ │ │ │      </h1>
│ │ │ │  <h2 id="file-inclusion" class="section-heading">
│ │ │ │    <a href="#file-inclusion" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">File Inclusion</span>
│ │ │ │  </h2>
│ │ │ │ -<p>A file can be included as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="5496291253-1">(</span><span class="n">File</span><span class="p" data-group-id="5496291253-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="5496291253-2">(</span><span class="n">File</span><span class="p" data-group-id="5496291253-2">)</span><span class="p">.</span></code></pre><p><code class="inline">File</code>, a string, is to point out a file. The contents of this file are included
│ │ │ │ +<p>A file can be included as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0224000266-1">(</span><span class="n">File</span><span class="p" data-group-id="0224000266-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="0224000266-2">(</span><span class="n">File</span><span class="p" data-group-id="0224000266-2">)</span><span class="p">.</span></code></pre><p><code class="inline">File</code>, a string, is to point out a file. The contents of this file are included
│ │ │ │  as is, at the position of the directive.</p><p>Include files are typically used for record and macro definitions that are
│ │ │ │  shared by several modules. It is recommended to use the file name extension
│ │ │ │  <code class="inline">.hrl</code> for include files.</p><p><code class="inline">File</code> can start with a path component <code class="inline">$VAR</code>, for some string <code class="inline">VAR</code>. If that is
│ │ │ │  the case, the value of the environment variable <code class="inline">VAR</code> as returned by
│ │ │ │  <code class="inline">os:getenv(VAR)</code> is substituted for <code class="inline">$VAR</code>. If <code class="inline">os:getenv(VAR)</code> returns <code class="inline">false</code>,
│ │ │ │  <code class="inline">$VAR</code> is left as is.</p><p>If the filename <code class="inline">File</code> is absolute (possibly after variable substitution), the
│ │ │ │  include file with that name is included. Otherwise, the specified file is
│ │ │ │  searched for in the following directories, and in this order:</p><ol><li>The current working directory</li><li>The directory where the module is being compiled</li><li>The directories given by the <code class="inline">include</code> option</li></ol><p>For details, see <a href="../../../lib/../erts/doc/html/erlc_cmd.xhtml">erlc</a> in ERTS and
│ │ │ │ -<a href="../../../lib/compiler/doc/html/compile.html"><code class="inline">compile</code></a> in Compiler.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0343053660-1">(</span><span class="s">&quot;my_records.hrl&quot;</span><span class="p" data-group-id="0343053660-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0343053660-2">(</span><span class="s">&quot;incdir/my_records.hrl&quot;</span><span class="p" data-group-id="0343053660-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0343053660-3">(</span><span class="s">&quot;/home/user/proj/my_records.hrl&quot;</span><span class="p" data-group-id="0343053660-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0343053660-4">(</span><span class="s">&quot;$PROJ_ROOT/my_records.hrl&quot;</span><span class="p" data-group-id="0343053660-4">)</span><span class="p">.</span></code></pre><p><code class="inline">include_lib</code> is similar to <code class="inline">include</code>, but is not to point out an absolute file.
│ │ │ │ +<a href="../../../lib/compiler/doc/html/compile.html"><code class="inline">compile</code></a> in Compiler.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="8576479032-1">(</span><span class="s">&quot;my_records.hrl&quot;</span><span class="p" data-group-id="8576479032-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="8576479032-2">(</span><span class="s">&quot;incdir/my_records.hrl&quot;</span><span class="p" data-group-id="8576479032-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="8576479032-3">(</span><span class="s">&quot;/home/user/proj/my_records.hrl&quot;</span><span class="p" data-group-id="8576479032-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="8576479032-4">(</span><span class="s">&quot;$PROJ_ROOT/my_records.hrl&quot;</span><span class="p" data-group-id="8576479032-4">)</span><span class="p">.</span></code></pre><p><code class="inline">include_lib</code> is similar to <code class="inline">include</code>, but is not to point out an absolute file.
│ │ │ │  Instead, the first path component (possibly after variable substitution) is
│ │ │ │ -assumed to be the name of an application.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="0997159422-1">(</span><span class="s">&quot;kernel/include/file.hrl&quot;</span><span class="p" data-group-id="0997159422-1">)</span><span class="p">.</span></code></pre><p>The code server uses <code class="inline">code:lib_dir(kernel)</code> to find the directory of the current
│ │ │ │ +assumed to be the name of an application.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="0150491820-1">(</span><span class="s">&quot;kernel/include/file.hrl&quot;</span><span class="p" data-group-id="0150491820-1">)</span><span class="p">.</span></code></pre><p>The code server uses <code class="inline">code:lib_dir(kernel)</code> to find the directory of the current
│ │ │ │  (latest) version of Kernel, and then the subdirectory <code class="inline">include</code> is searched for
│ │ │ │  the file <code class="inline">file.hrl</code>.</p><h2 id="defining-and-using-macros" class="section-heading">
│ │ │ │    <a href="#defining-and-using-macros" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Defining and Using Macros</span>
│ │ │ │  </h2>
│ │ │ │ -<p>A macro is defined as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8477588377-1">(</span><span class="n">Const</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="8477588377-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8477588377-2">(</span><span class="n">Func</span><span class="p" data-group-id="8477588377-3">(</span><span class="n">Var1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">VarN</span><span class="p" data-group-id="8477588377-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="8477588377-2">)</span><span class="p">.</span></code></pre><p>A macro definition can be placed anywhere among the attributes and function
│ │ │ │ +<p>A macro is defined as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5994290045-1">(</span><span class="n">Const</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="5994290045-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5994290045-2">(</span><span class="n">Func</span><span class="p" data-group-id="5994290045-3">(</span><span class="n">Var1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">VarN</span><span class="p" data-group-id="5994290045-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="5994290045-2">)</span><span class="p">.</span></code></pre><p>A macro definition can be placed anywhere among the attributes and function
│ │ │ │  declarations of a module, but the definition must come before any usage of the
│ │ │ │  macro.</p><p>If a macro is used in several modules, it is recommended that the macro
│ │ │ │  definition is placed in an include file.</p><p>A macro is used as follows:</p><pre><code class="text">?Const
│ │ │ │  ?Func(Arg1,...,ArgN)</code></pre><p>Macros are expanded during compilation. A simple macro <code class="inline">?Const</code> is replaced with
│ │ │ │ -<code class="inline">Replacement</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3814761911-1">(</span><span class="n">TIMEOUT</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p" data-group-id="3814761911-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">Replacement</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2284454109-1">(</span><span class="n">TIMEOUT</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p" data-group-id="2284454109-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">call</span><span class="p" data-group-id="3814761911-2">(</span><span class="n">Request</span><span class="p" data-group-id="3814761911-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="3814761911-3">(</span><span class="ss">refserver</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">TIMEOUT</span><span class="p" data-group-id="3814761911-3">)</span><span class="p">.</span></code></pre><p>This is expanded to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">call</span><span class="p" data-group-id="9516217775-1">(</span><span class="n">Request</span><span class="p" data-group-id="9516217775-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="9516217775-2">(</span><span class="ss">refserver</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p" data-group-id="9516217775-2">)</span><span class="p">.</span></code></pre><p>A macro <code class="inline">?Func(Arg1,...,ArgN)</code> is replaced with <code class="inline">Replacement</code>, where all
│ │ │ │ +</span><span class="nf">call</span><span class="p" data-group-id="2284454109-2">(</span><span class="n">Request</span><span class="p" data-group-id="2284454109-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="2284454109-3">(</span><span class="ss">refserver</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">TIMEOUT</span><span class="p" data-group-id="2284454109-3">)</span><span class="p">.</span></code></pre><p>This is expanded to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">call</span><span class="p" data-group-id="6575908692-1">(</span><span class="n">Request</span><span class="p" data-group-id="6575908692-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="6575908692-2">(</span><span class="ss">refserver</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p" data-group-id="6575908692-2">)</span><span class="p">.</span></code></pre><p>A macro <code class="inline">?Func(Arg1,...,ArgN)</code> is replaced with <code class="inline">Replacement</code>, where all
│ │ │ │  occurrences of a variable <code class="inline">Var</code> from the macro definition are replaced with the
│ │ │ │ -corresponding argument <code class="inline">Arg</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0265813427-1">(</span><span class="n">MACRO1</span><span class="p" data-group-id="0265813427-2">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0265813427-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0265813427-3">{</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0265813427-3">}</span><span class="p" data-group-id="0265813427-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +corresponding argument <code class="inline">Arg</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="1396374918-1">(</span><span class="n">MACRO1</span><span class="p" data-group-id="1396374918-2">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1396374918-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1396374918-3">{</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1396374918-3">}</span><span class="p" data-group-id="1396374918-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="0265813427-4">(</span><span class="n">X</span><span class="p" data-group-id="0265813427-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="o">?</span><span class="n">MACRO1</span><span class="p" data-group-id="0265813427-5">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="0265813427-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="o">?</span><span class="n">MACRO1</span><span class="p" data-group-id="0265813427-6">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="mi">123</span><span class="p" data-group-id="0265813427-6">)</span></code></pre><p>This is expanded to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="1608606469-1">(</span><span class="n">X</span><span class="p" data-group-id="1608606469-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1608606469-2">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1608606469-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1608606469-3">{</span><span class="ss">a</span><span class="p">,</span><span class="n">X</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">123</span><span class="p" data-group-id="1608606469-3">}</span><span class="p">.</span></code></pre><p>It is good programming practice, but not mandatory, to ensure that a macro
│ │ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="1396374918-4">(</span><span class="n">X</span><span class="p" data-group-id="1396374918-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="o">?</span><span class="n">MACRO1</span><span class="p" data-group-id="1396374918-5">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1396374918-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="o">?</span><span class="n">MACRO1</span><span class="p" data-group-id="1396374918-6">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="mi">123</span><span class="p" data-group-id="1396374918-6">)</span></code></pre><p>This is expanded to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="0672204299-1">(</span><span class="n">X</span><span class="p" data-group-id="0672204299-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0672204299-2">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="0672204299-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0672204299-3">{</span><span class="ss">a</span><span class="p">,</span><span class="n">X</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">123</span><span class="p" data-group-id="0672204299-3">}</span><span class="p">.</span></code></pre><p>It is good programming practice, but not mandatory, to ensure that a macro
│ │ │ │  definition is a valid Erlang syntactic form.</p><p>To view the result of macro expansion, a module can be compiled with the <code class="inline">'P'</code>
│ │ │ │  option. <code class="inline">compile:file(File, ['P'])</code>. This produces a listing of the parsed code
│ │ │ │  after preprocessing and parse transforms, in the file <code class="inline">File.P</code>.</p><h2 id="predefined-macros" class="section-heading">
│ │ │ │    <a href="#predefined-macros" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Predefined Macros</span>
│ │ │ │ @@ -90,29 +90,29 @@
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Macro Overloading</span>
│ │ │ │  </h2>
│ │ │ │  <p>It is possible to overload macros, except for predefined macros. An overloaded
│ │ │ │  macro has more than one definition, each with a different number of arguments.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Support for overloading of macros was added in Erlang 5.7.5/OTP R13B04.</p></section><p>A macro <code class="inline">?Func(Arg1,...,ArgN)</code> with a (possibly empty) list of arguments results
│ │ │ │  in an error message if there is at least one definition of <code class="inline">Func</code> with
│ │ │ │ -arguments, but none with N arguments.</p><p>Assuming these definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6317993280-1">(</span><span class="n">F0</span><span class="p" data-group-id="6317993280-2">(</span><span class="p" data-group-id="6317993280-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="6317993280-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6317993280-3">(</span><span class="n">F1</span><span class="p" data-group-id="6317993280-4">(</span><span class="n">A</span><span class="p" data-group-id="6317993280-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="6317993280-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6317993280-5">(</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="nc">m</span><span class="p">:</span><span class="ss">f</span><span class="p" data-group-id="6317993280-5">)</span><span class="p">.</span></code></pre><p>the following does not work:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f0</span><span class="p" data-group-id="0930805407-1">(</span><span class="p" data-group-id="0930805407-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +arguments, but none with N arguments.</p><p>Assuming these definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5952491926-1">(</span><span class="n">F0</span><span class="p" data-group-id="5952491926-2">(</span><span class="p" data-group-id="5952491926-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="5952491926-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5952491926-3">(</span><span class="n">F1</span><span class="p" data-group-id="5952491926-4">(</span><span class="n">A</span><span class="p" data-group-id="5952491926-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="5952491926-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5952491926-5">(</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="nc">m</span><span class="p">:</span><span class="ss">f</span><span class="p" data-group-id="5952491926-5">)</span><span class="p">.</span></code></pre><p>the following does not work:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f0</span><span class="p" data-group-id="6396624833-1">(</span><span class="p" data-group-id="6396624833-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="o">?</span><span class="n">F0</span><span class="p">.</span><span class="w"> </span><span class="c1">% No, an empty list of arguments expected.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">f1</span><span class="p" data-group-id="0930805407-2">(</span><span class="n">A</span><span class="p" data-group-id="0930805407-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="o">?</span><span class="n">F1</span><span class="p" data-group-id="0930805407-3">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="0930805407-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% No, exactly one argument expected.</span></code></pre><p>On the other hand,</p><pre><code class="text">f() -&gt;
│ │ │ │ -    ?C().</code></pre><p>is expanded to</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="1251094204-1">(</span><span class="p" data-group-id="1251094204-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">m</span><span class="p">:</span><span class="nf">f</span><span class="p" data-group-id="1251094204-2">(</span><span class="p" data-group-id="1251094204-2">)</span><span class="p">.</span></code></pre><h2 id="removing-a-macro-definition" class="section-heading">
│ │ │ │ +</span><span class="nf">f1</span><span class="p" data-group-id="6396624833-2">(</span><span class="n">A</span><span class="p" data-group-id="6396624833-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="o">?</span><span class="n">F1</span><span class="p" data-group-id="6396624833-3">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="6396624833-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% No, exactly one argument expected.</span></code></pre><p>On the other hand,</p><pre><code class="text">f() -&gt;
│ │ │ │ +    ?C().</code></pre><p>is expanded to</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="6315347078-1">(</span><span class="p" data-group-id="6315347078-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">m</span><span class="p">:</span><span class="nf">f</span><span class="p" data-group-id="6315347078-2">(</span><span class="p" data-group-id="6315347078-2">)</span><span class="p">.</span></code></pre><h2 id="removing-a-macro-definition" class="section-heading">
│ │ │ │    <a href="#removing-a-macro-definition" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Removing a macro definition</span>
│ │ │ │  </h2>
│ │ │ │ -<p>A definition of a macro can be removed as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">undef</span><span class="p" data-group-id="4326422737-1">(</span><span class="n">Macro</span><span class="p" data-group-id="4326422737-1">)</span><span class="p">.</span></code></pre><h2 id="conditional-compilation" class="section-heading">
│ │ │ │ +<p>A definition of a macro can be removed as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">undef</span><span class="p" data-group-id="6828394622-1">(</span><span class="n">Macro</span><span class="p" data-group-id="6828394622-1">)</span><span class="p">.</span></code></pre><h2 id="conditional-compilation" class="section-heading">
│ │ │ │    <a href="#conditional-compilation" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Conditional Compilation</span>
│ │ │ │  </h2>
│ │ │ │  <p>The following macro directives support conditional compilation:</p><ul><li><p><strong><code class="inline">-ifdef(Macro).</code></strong> - Evaluate the following lines only if <code class="inline">Macro</code> is
│ │ │ │  defined.</p></li><li><p><strong><code class="inline">-ifndef(Macro).</code></strong> - Evaluate the following lines only if <code class="inline">Macro</code> is not
│ │ │ │ @@ -124,43 +124,43 @@
│ │ │ │  true, and the <code class="inline">Condition</code> evaluates to true, the lines following the <code class="inline">elif</code>
│ │ │ │  are evaluated instead.</p></li><li><p><strong><code class="inline">-endif.</code></strong> - Specifies the end of a series of control flow directives.</p></li></ul><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Macro directives cannot be used inside functions.</p></section><p>Syntactically, the <code class="inline">Condition</code> in <code class="inline">if</code> and <code class="inline">elif</code> must be a
│ │ │ │  <a href="expressions.xhtml#guard-expressions">guard expression</a>. Other constructs (such as
│ │ │ │  a <code class="inline">case</code> expression) result in a compilation error.</p><p>As opposed to the standard guard expressions, an expression in an <code class="inline">if</code> and
│ │ │ │  <code class="inline">elif</code> also supports calling the pseudo-function <code class="inline">defined(Name)</code>, which tests
│ │ │ │  whether the <code class="inline">Name</code> argument is the name of a previously defined macro.
│ │ │ │  <code class="inline">defined(Name)</code> evaluates to <code class="inline">true</code> if the macro is defined and <code class="inline">false</code>
│ │ │ │ -otherwise. An attempt to call other functions results in a compilation error.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4615608935-1">(</span><span class="ss">m</span><span class="p" data-group-id="4615608935-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +otherwise. An attempt to call other functions results in a compilation error.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4077713333-1">(</span><span class="ss">m</span><span class="p" data-group-id="4077713333-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">ifdef</span><span class="p" data-group-id="4615608935-2">(</span><span class="ss">debug</span><span class="p" data-group-id="4615608935-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4615608935-3">(</span><span class="n">LOG</span><span class="p" data-group-id="4615608935-4">(</span><span class="n">X</span><span class="p" data-group-id="4615608935-4">)</span><span class="p">,</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4615608935-5">(</span><span class="s">&quot;{</span><span class="si">~p</span><span class="s">,</span><span class="si">~p</span><span class="s">}: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4615608935-6">[</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="o">?</span><span class="n">LINE</span><span class="p">,</span><span class="n">X</span><span class="p" data-group-id="4615608935-6">]</span><span class="p" data-group-id="4615608935-5">)</span><span class="p" data-group-id="4615608935-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">ifdef</span><span class="p" data-group-id="4077713333-2">(</span><span class="ss">debug</span><span class="p" data-group-id="4077713333-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4077713333-3">(</span><span class="n">LOG</span><span class="p" data-group-id="4077713333-4">(</span><span class="n">X</span><span class="p" data-group-id="4077713333-4">)</span><span class="p">,</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4077713333-5">(</span><span class="s">&quot;{</span><span class="si">~p</span><span class="s">,</span><span class="si">~p</span><span class="s">}: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4077713333-6">[</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="o">?</span><span class="n">LINE</span><span class="p">,</span><span class="n">X</span><span class="p" data-group-id="4077713333-6">]</span><span class="p" data-group-id="4077713333-5">)</span><span class="p" data-group-id="4077713333-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">else</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4615608935-7">(</span><span class="n">LOG</span><span class="p" data-group-id="4615608935-8">(</span><span class="n">X</span><span class="p" data-group-id="4615608935-8">)</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4615608935-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4077713333-7">(</span><span class="n">LOG</span><span class="p" data-group-id="4077713333-8">(</span><span class="n">X</span><span class="p" data-group-id="4077713333-8">)</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4077713333-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>When trace output is desired, <code class="inline">debug</code> is to be defined when the module <code class="inline">m</code> is
│ │ │ │  compiled:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erlc -Ddebug m.erl</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="ow">or</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">c</span><span class="p" data-group-id="4248131231-1">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4248131231-2">{</span><span class="ss">d</span><span class="p">,</span><span class="w"> </span><span class="ss">debug</span><span class="p" data-group-id="4248131231-2">}</span><span class="p" data-group-id="4248131231-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4248131231-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">m</span><span class="p" data-group-id="4248131231-3">}</span></code></pre><p><code class="inline">?LOG(Arg)</code> is then expanded to a call to <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> and provides the user
│ │ │ │ -with some simple trace output.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0447172116-1">(</span><span class="ss">m</span><span class="p" data-group-id="0447172116-1">)</span><span class="w">
│ │ │ │ +</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">c</span><span class="p" data-group-id="5789008374-1">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5789008374-2">{</span><span class="ss">d</span><span class="p">,</span><span class="w"> </span><span class="ss">debug</span><span class="p" data-group-id="5789008374-2">}</span><span class="p" data-group-id="5789008374-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5789008374-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">m</span><span class="p" data-group-id="5789008374-3">}</span></code></pre><p><code class="inline">?LOG(Arg)</code> is then expanded to a call to <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> and provides the user
│ │ │ │ +with some simple trace output.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3769574926-1">(</span><span class="ss">m</span><span class="p" data-group-id="3769574926-1">)</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">if</span><span class="p" data-group-id="0447172116-2">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">26</span><span class="p" data-group-id="0447172116-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">if</span><span class="p" data-group-id="3769574926-2">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">26</span><span class="p" data-group-id="3769574926-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% Code that will work in OTP 26 or higher</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">elif</span><span class="p" data-group-id="0447172116-3">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">25</span><span class="p" data-group-id="0447172116-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">elif</span><span class="p" data-group-id="3769574926-3">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">25</span><span class="p" data-group-id="3769574926-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% Code that will work in OTP 25 or higher</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">else</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% Code that will work in OTP 24 or lower.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>This code uses the <code class="inline">OTP_RELEASE</code> macro to conditionally select code depending on
│ │ │ │ -release.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1488272313-1">(</span><span class="ss">m</span><span class="p" data-group-id="1488272313-1">)</span><span class="w">
│ │ │ │ +release.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0073867681-1">(</span><span class="ss">m</span><span class="p" data-group-id="0073867681-1">)</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">if</span><span class="p" data-group-id="1488272313-2">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">defined</span><span class="p" data-group-id="1488272313-3">(</span><span class="ss">debug</span><span class="p" data-group-id="1488272313-3">)</span><span class="p" data-group-id="1488272313-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">if</span><span class="p" data-group-id="0073867681-2">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">defined</span><span class="p" data-group-id="0073867681-3">(</span><span class="ss">debug</span><span class="p" data-group-id="0073867681-3">)</span><span class="p" data-group-id="0073867681-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% Debugging code that requires OTP 26 or later.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">else</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% Non-debug code that works in any release.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>This code uses the <code class="inline">OTP_RELEASE</code> macro and <code class="inline">defined(debug)</code> to compile debug
│ │ │ │  code only for OTP 26 or later.</p><h2 id="the-feature-directive" class="section-heading">
│ │ │ │    <a href="#the-feature-directive" class="hover-link">
│ │ │ │ @@ -175,40 +175,40 @@
│ │ │ │  used. In practice this means it should appear before any <code class="inline">-export(..)</code> or record
│ │ │ │  definitions.</p><h2 id="error-and-warning-directives" class="section-heading">
│ │ │ │    <a href="#error-and-warning-directives" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">-error() and -warning() directives</span>
│ │ │ │  </h2>
│ │ │ │ -<p>The directive <code class="inline">-error(Term)</code> causes a compilation error.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5161325547-1">(</span><span class="ss">t</span><span class="p" data-group-id="5161325547-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5161325547-2">(</span><span class="p" data-group-id="5161325547-3">[</span><span class="ss">version</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5161325547-3">]</span><span class="p" data-group-id="5161325547-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>The directive <code class="inline">-error(Term)</code> causes a compilation error.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2187958359-1">(</span><span class="ss">t</span><span class="p" data-group-id="2187958359-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2187958359-2">(</span><span class="p" data-group-id="2187958359-3">[</span><span class="ss">version</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2187958359-3">]</span><span class="p" data-group-id="2187958359-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">ifdef</span><span class="p" data-group-id="5161325547-4">(</span><span class="n">VERSION</span><span class="p" data-group-id="5161325547-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">version</span><span class="p" data-group-id="5161325547-5">(</span><span class="p" data-group-id="5161325547-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VERSION</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">ifdef</span><span class="p" data-group-id="2187958359-4">(</span><span class="n">VERSION</span><span class="p" data-group-id="2187958359-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">version</span><span class="p" data-group-id="2187958359-5">(</span><span class="p" data-group-id="2187958359-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VERSION</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">else</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">error</span><span class="p" data-group-id="5161325547-6">(</span><span class="s">&quot;Macro VERSION must be defined.&quot;</span><span class="p" data-group-id="5161325547-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">version</span><span class="p" data-group-id="5161325547-7">(</span><span class="p" data-group-id="5161325547-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">error</span><span class="p" data-group-id="2187958359-6">(</span><span class="s">&quot;Macro VERSION must be defined.&quot;</span><span class="p" data-group-id="2187958359-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">version</span><span class="p" data-group-id="2187958359-7">(</span><span class="p" data-group-id="2187958359-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span></code></pre><p>The error message will look like this:</p><pre><code class="text">% erlc t.erl
│ │ │ │ -t.erl:7: -error(&quot;Macro VERSION must be defined.&quot;).</code></pre><p>The directive <code class="inline">-warning(Term)</code> causes a compilation warning.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7326204238-1">(</span><span class="ss">t</span><span class="p" data-group-id="7326204238-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7326204238-2">(</span><span class="p" data-group-id="7326204238-3">[</span><span class="ss">version</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7326204238-3">]</span><span class="p" data-group-id="7326204238-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +t.erl:7: -error(&quot;Macro VERSION must be defined.&quot;).</code></pre><p>The directive <code class="inline">-warning(Term)</code> causes a compilation warning.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0352796459-1">(</span><span class="ss">t</span><span class="p" data-group-id="0352796459-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0352796459-2">(</span><span class="p" data-group-id="0352796459-3">[</span><span class="ss">version</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0352796459-3">]</span><span class="p" data-group-id="0352796459-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">ifndef</span><span class="p" data-group-id="7326204238-4">(</span><span class="n">VERSION</span><span class="p" data-group-id="7326204238-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">warning</span><span class="p" data-group-id="7326204238-5">(</span><span class="s">&quot;Macro VERSION not defined -- using default version.&quot;</span><span class="p" data-group-id="7326204238-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7326204238-6">(</span><span class="n">VERSION</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;0&quot;</span><span class="p" data-group-id="7326204238-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">ifndef</span><span class="p" data-group-id="0352796459-4">(</span><span class="n">VERSION</span><span class="p" data-group-id="0352796459-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">warning</span><span class="p" data-group-id="0352796459-5">(</span><span class="s">&quot;Macro VERSION not defined -- using default version.&quot;</span><span class="p" data-group-id="0352796459-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0352796459-6">(</span><span class="n">VERSION</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;0&quot;</span><span class="p" data-group-id="0352796459-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">version</span><span class="p" data-group-id="7326204238-7">(</span><span class="p" data-group-id="7326204238-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VERSION</span><span class="p">.</span></code></pre><p>The warning message will look like this:</p><pre><code class="text">% erlc t.erl
│ │ │ │ +</span><span class="nf">version</span><span class="p" data-group-id="0352796459-7">(</span><span class="p" data-group-id="0352796459-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VERSION</span><span class="p">.</span></code></pre><p>The warning message will look like this:</p><pre><code class="text">% erlc t.erl
│ │ │ │  t.erl:5: Warning: -warning(&quot;Macro VERSION not defined -- using default version.&quot;).</code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>The <code class="inline">-error()</code> and <code class="inline">-warning()</code> directives were added in Erlang/OTP 19.</p></section><h2 id="stringifying-macro-arguments" class="section-heading">
│ │ │ │    <a href="#stringifying-macro-arguments" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Stringifying Macro Arguments</span>
│ │ │ │  </h2>
│ │ │ │  <p>The construction <code class="inline">??Arg</code>, where <code class="inline">Arg</code> is a macro argument, is expanded to a
│ │ │ │  string containing the tokens of the argument. This is similar to the <code class="inline">#arg</code>
│ │ │ │ -stringifying construction in C.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9644952405-1">(</span><span class="n">TESTCALL</span><span class="p" data-group-id="9644952405-2">(</span><span class="n">Call</span><span class="p" data-group-id="9644952405-2">)</span><span class="p">,</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9644952405-3">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9644952405-4">[</span><span class="o">?</span><span class="o">?</span><span class="n">Call</span><span class="p">,</span><span class="w"> </span><span class="n">Call</span><span class="p" data-group-id="9644952405-4">]</span><span class="p" data-group-id="9644952405-3">)</span><span class="p" data-group-id="9644952405-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +stringifying construction in C.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2834057004-1">(</span><span class="n">TESTCALL</span><span class="p" data-group-id="2834057004-2">(</span><span class="n">Call</span><span class="p" data-group-id="2834057004-2">)</span><span class="p">,</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2834057004-3">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2834057004-4">[</span><span class="o">?</span><span class="o">?</span><span class="n">Call</span><span class="p">,</span><span class="w"> </span><span class="n">Call</span><span class="p" data-group-id="2834057004-4">]</span><span class="p" data-group-id="2834057004-3">)</span><span class="p" data-group-id="2834057004-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="o">?</span><span class="n">TESTCALL</span><span class="p" data-group-id="9644952405-5">(</span><span class="nf">myfunction</span><span class="p" data-group-id="9644952405-6">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9644952405-6">)</span><span class="p" data-group-id="9644952405-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="o">?</span><span class="n">TESTCALL</span><span class="p" data-group-id="9644952405-7">(</span><span class="nc">you</span><span class="p">:</span><span class="nf">function</span><span class="p" data-group-id="9644952405-8">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9644952405-8">)</span><span class="p" data-group-id="9644952405-7">)</span><span class="p">.</span></code></pre><p>results in</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6675920694-1">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="6675920694-2">[</span><span class="s">&quot;myfunction ( 1 , 2 )&quot;</span><span class="p">,</span><span class="nf">myfunction</span><span class="p" data-group-id="6675920694-3">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6675920694-3">)</span><span class="p" data-group-id="6675920694-2">]</span><span class="p" data-group-id="6675920694-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6675920694-4">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="6675920694-5">[</span><span class="s">&quot;you : function ( 2 , 1 )&quot;</span><span class="p">,</span><span class="nc">you</span><span class="p">:</span><span class="nf">function</span><span class="p" data-group-id="6675920694-6">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6675920694-6">)</span><span class="p" data-group-id="6675920694-5">]</span><span class="p" data-group-id="6675920694-4">)</span><span class="p">.</span></code></pre><p>That is, a trace output, with both the function called and the resulting value.</p>
│ │ │ │ +</span><span class="o">?</span><span class="n">TESTCALL</span><span class="p" data-group-id="2834057004-5">(</span><span class="nf">myfunction</span><span class="p" data-group-id="2834057004-6">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2834057004-6">)</span><span class="p" data-group-id="2834057004-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="o">?</span><span class="n">TESTCALL</span><span class="p" data-group-id="2834057004-7">(</span><span class="nc">you</span><span class="p">:</span><span class="nf">function</span><span class="p" data-group-id="2834057004-8">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2834057004-8">)</span><span class="p" data-group-id="2834057004-7">)</span><span class="p">.</span></code></pre><p>results in</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8519883890-1">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="8519883890-2">[</span><span class="s">&quot;myfunction ( 1 , 2 )&quot;</span><span class="p">,</span><span class="nf">myfunction</span><span class="p" data-group-id="8519883890-3">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8519883890-3">)</span><span class="p" data-group-id="8519883890-2">]</span><span class="p" data-group-id="8519883890-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8519883890-4">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="8519883890-5">[</span><span class="s">&quot;you : function ( 2 , 1 )&quot;</span><span class="p">,</span><span class="nc">you</span><span class="p">:</span><span class="nf">function</span><span class="p" data-group-id="8519883890-6">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="8519883890-6">)</span><span class="p" data-group-id="8519883890-5">]</span><span class="p" data-group-id="8519883890-4">)</span><span class="p">.</span></code></pre><p>That is, a trace output, with both the function called and the resulting value.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/listhandling.xhtml
│ │ │ │ @@ -25,101 +25,101 @@
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Creating a List</span>
│ │ │ │  </h2>
│ │ │ │  <p>Lists can only be built starting from the end and attaching list elements at the
│ │ │ │  beginning. If you use the <code class="inline">++</code> operator as follows, a new list is created that
│ │ │ │  is a copy of the elements in <code class="inline">List1</code>, followed by <code class="inline">List2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">List1</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">List2</span></code></pre><p>Looking at how <a href="../../../lib/stdlib/doc/html/lists.html#append/2"><code class="inline">lists:append/2</code></a> or <code class="inline">++</code> would be implemented in plain Erlang,
│ │ │ │ -clearly the first list is copied:</p><pre><code class="makeup erlang" translate="no"><span class="nf">append</span><span class="p" data-group-id="9153627016-1">(</span><span class="p" data-group-id="9153627016-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9153627016-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="9153627016-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9153627016-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">append</span><span class="p" data-group-id="9153627016-4">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="9153627016-4">)</span><span class="p" data-group-id="9153627016-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">append</span><span class="p" data-group-id="9153627016-5">(</span><span class="p" data-group-id="9153627016-6">[</span><span class="p" data-group-id="9153627016-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="9153627016-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +clearly the first list is copied:</p><pre><code class="makeup erlang" translate="no"><span class="nf">append</span><span class="p" data-group-id="5331364097-1">(</span><span class="p" data-group-id="5331364097-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5331364097-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="5331364097-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5331364097-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">append</span><span class="p" data-group-id="5331364097-4">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="5331364097-4">)</span><span class="p" data-group-id="5331364097-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">append</span><span class="p" data-group-id="5331364097-5">(</span><span class="p" data-group-id="5331364097-6">[</span><span class="p" data-group-id="5331364097-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="5331364097-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Tail</span><span class="p">.</span></code></pre><p>When recursing and building a list, it is important to ensure that you attach
│ │ │ │  the new elements to the beginning of the list. In this way, you will build <em>one</em>
│ │ │ │ -list, not hundreds or thousands of copies of the growing result list.</p><p>Let us first see how it is not to be done:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">bad_fib</span><span class="p" data-group-id="3790806780-1">(</span><span class="n">N</span><span class="p" data-group-id="3790806780-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">bad_fib</span><span class="p" data-group-id="3790806780-2">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3790806780-3">[</span><span class="p" data-group-id="3790806780-3">]</span><span class="p" data-group-id="3790806780-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +list, not hundreds or thousands of copies of the growing result list.</p><p>Let us first see how it is not to be done:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">bad_fib</span><span class="p" data-group-id="8491600123-1">(</span><span class="n">N</span><span class="p" data-group-id="8491600123-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">bad_fib</span><span class="p" data-group-id="8491600123-2">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8491600123-3">[</span><span class="p" data-group-id="8491600123-3">]</span><span class="p" data-group-id="8491600123-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">bad_fib</span><span class="p" data-group-id="3790806780-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="3790806780-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">bad_fib</span><span class="p" data-group-id="8491600123-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="8491600123-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Fibs</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">bad_fib</span><span class="p" data-group-id="3790806780-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="3790806780-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">bad_fib</span><span class="p" data-group-id="3790806780-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="3790806780-7">[</span><span class="n">Current</span><span class="p" data-group-id="3790806780-7">]</span><span class="p" data-group-id="3790806780-6">)</span><span class="p">.</span></code></pre><p>Here more than one list is built. In each iteration step a new list is created
│ │ │ │ +</span><span class="nf">bad_fib</span><span class="p" data-group-id="8491600123-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="8491600123-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">bad_fib</span><span class="p" data-group-id="8491600123-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="8491600123-7">[</span><span class="n">Current</span><span class="p" data-group-id="8491600123-7">]</span><span class="p" data-group-id="8491600123-6">)</span><span class="p">.</span></code></pre><p>Here more than one list is built. In each iteration step a new list is created
│ │ │ │  that is one element longer than the new previous list.</p><p>To avoid copying the result in each iteration, build the list in reverse order
│ │ │ │ -and reverse the list when you are done:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="1437092688-1">(</span><span class="n">N</span><span class="p" data-group-id="1437092688-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="1437092688-2">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1437092688-3">[</span><span class="p" data-group-id="1437092688-3">]</span><span class="p" data-group-id="1437092688-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +and reverse the list when you are done:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="7892064745-1">(</span><span class="n">N</span><span class="p" data-group-id="7892064745-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="7892064745-2">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7892064745-3">[</span><span class="p" data-group-id="7892064745-3">]</span><span class="p" data-group-id="7892064745-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="1437092688-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="1437092688-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="1437092688-5">(</span><span class="n">Fibs</span><span class="p" data-group-id="1437092688-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="1437092688-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="1437092688-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="1437092688-7">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1437092688-8">[</span><span class="n">Current</span><span class="p">|</span><span class="n">Fibs</span><span class="p" data-group-id="1437092688-8">]</span><span class="p" data-group-id="1437092688-7">)</span><span class="p">.</span></code></pre><h2 id="list-comprehensions" class="section-heading">
│ │ │ │ +</span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="7892064745-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="7892064745-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="7892064745-5">(</span><span class="n">Fibs</span><span class="p" data-group-id="7892064745-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="7892064745-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="7892064745-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="7892064745-7">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7892064745-8">[</span><span class="n">Current</span><span class="p">|</span><span class="n">Fibs</span><span class="p" data-group-id="7892064745-8">]</span><span class="p" data-group-id="7892064745-7">)</span><span class="p">.</span></code></pre><h2 id="list-comprehensions" class="section-heading">
│ │ │ │    <a href="#list-comprehensions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">List Comprehensions</span>
│ │ │ │  </h2>
│ │ │ │ -<p>A list comprehension:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3873733291-1">[</span><span class="n">Expr</span><span class="p" data-group-id="3873733291-2">(</span><span class="n">E</span><span class="p" data-group-id="3873733291-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="3873733291-1">]</span></code></pre><p>is basically translated to a local function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="8593983376-1">(</span><span class="p" data-group-id="8593983376-2">[</span><span class="n">E</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="8593983376-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="8593983376-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8593983376-3">[</span><span class="n">Expr</span><span class="p" data-group-id="8593983376-4">(</span><span class="n">E</span><span class="p" data-group-id="8593983376-4">)</span><span class="p">|</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="8593983376-5">(</span><span class="n">Tail</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="8593983376-5">)</span><span class="p" data-group-id="8593983376-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="8593983376-6">(</span><span class="p" data-group-id="8593983376-7">[</span><span class="p" data-group-id="8593983376-7">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Expr</span><span class="p" data-group-id="8593983376-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8593983376-8">[</span><span class="p" data-group-id="8593983376-8">]</span><span class="p">.</span></code></pre><p>If the result of the list comprehension will <em>obviously</em> not be used, a list
│ │ │ │ -will not be constructed. For example, in this code:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1731052255-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="1731052255-2">(</span><span class="n">E</span><span class="p" data-group-id="1731052255-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="1731052255-1">]</span><span class="p">,</span><span class="w">
│ │ │ │ +<p>A list comprehension:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4951384427-1">[</span><span class="n">Expr</span><span class="p" data-group-id="4951384427-2">(</span><span class="n">E</span><span class="p" data-group-id="4951384427-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="4951384427-1">]</span></code></pre><p>is basically translated to a local function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="5462767498-1">(</span><span class="p" data-group-id="5462767498-2">[</span><span class="n">E</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="5462767498-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="5462767498-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5462767498-3">[</span><span class="n">Expr</span><span class="p" data-group-id="5462767498-4">(</span><span class="n">E</span><span class="p" data-group-id="5462767498-4">)</span><span class="p">|</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="5462767498-5">(</span><span class="n">Tail</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="5462767498-5">)</span><span class="p" data-group-id="5462767498-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="5462767498-6">(</span><span class="p" data-group-id="5462767498-7">[</span><span class="p" data-group-id="5462767498-7">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Expr</span><span class="p" data-group-id="5462767498-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5462767498-8">[</span><span class="p" data-group-id="5462767498-8">]</span><span class="p">.</span></code></pre><p>If the result of the list comprehension will <em>obviously</em> not be used, a list
│ │ │ │ +will not be constructed. For example, in this code:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0518612730-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="0518612730-2">(</span><span class="n">E</span><span class="p" data-group-id="0518612730-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="0518612730-1">]</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>or in this code:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="n">Var</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="2349348839-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="2349348839-2">(</span><span class="n">E</span><span class="p" data-group-id="2349348839-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="2349348839-1">]</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="5885838100-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="5885838100-2">(</span><span class="n">E</span><span class="p" data-group-id="5885838100-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="5885838100-1">]</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nf">some_function</span><span class="p" data-group-id="2349348839-3">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2349348839-3">)</span><span class="p">,</span></code></pre><p>the value is not assigned to a variable, not passed to another function, and not
│ │ │ │ +</span><span class="nf">some_function</span><span class="p" data-group-id="5885838100-3">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="5885838100-3">)</span><span class="p">,</span></code></pre><p>the value is not assigned to a variable, not passed to another function, and not
│ │ │ │  returned. This means that there is no need to construct a list and the compiler
│ │ │ │ -will simplify the code for the list comprehension to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="3921681512-1">(</span><span class="p" data-group-id="3921681512-2">[</span><span class="n">E</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="3921681512-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="3921681512-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Expr</span><span class="p" data-group-id="3921681512-3">(</span><span class="n">E</span><span class="p" data-group-id="3921681512-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="3921681512-4">(</span><span class="n">Tail</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="3921681512-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="3921681512-5">(</span><span class="p" data-group-id="3921681512-6">[</span><span class="p" data-group-id="3921681512-6">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Expr</span><span class="p" data-group-id="3921681512-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3921681512-7">[</span><span class="p" data-group-id="3921681512-7">]</span><span class="p">.</span></code></pre><p>The compiler also understands that assigning to <code class="inline">_</code> means that the value will
│ │ │ │ -not be used. Therefore, the code in the following example will also be optimized:</p><pre><code class="makeup erlang" translate="no"><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0332882328-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="0332882328-2">(</span><span class="n">E</span><span class="p" data-group-id="0332882328-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="0332882328-1">]</span><span class="p">,</span><span class="w">
│ │ │ │ +will simplify the code for the list comprehension to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="2916382629-1">(</span><span class="p" data-group-id="2916382629-2">[</span><span class="n">E</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="2916382629-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="2916382629-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Expr</span><span class="p" data-group-id="2916382629-3">(</span><span class="n">E</span><span class="p" data-group-id="2916382629-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="2916382629-4">(</span><span class="n">Tail</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="2916382629-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="2916382629-5">(</span><span class="p" data-group-id="2916382629-6">[</span><span class="p" data-group-id="2916382629-6">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Expr</span><span class="p" data-group-id="2916382629-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2916382629-7">[</span><span class="p" data-group-id="2916382629-7">]</span><span class="p">.</span></code></pre><p>The compiler also understands that assigning to <code class="inline">_</code> means that the value will
│ │ │ │ +not be used. Therefore, the code in the following example will also be optimized:</p><pre><code class="makeup erlang" translate="no"><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9071775303-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="9071775303-2">(</span><span class="n">E</span><span class="p" data-group-id="9071775303-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9071775303-1">]</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="p">.</span></code></pre><h2 id="deep-and-flat-lists" class="section-heading">
│ │ │ │    <a href="#deep-and-flat-lists" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Deep and Flat Lists</span>
│ │ │ │  </h2>
│ │ │ │  <p><a href="../../../lib/stdlib/doc/html/lists.html#flatten/1"><code class="inline">lists:flatten/1</code></a> builds an entirely new list. It is therefore expensive, and
│ │ │ │  even <em>more</em> expensive than the <code class="inline">++</code> operator (which copies its left argument,
│ │ │ │  but not its right argument).</p><p>In the following situations it is unnecessary to call <a href="../../../lib/stdlib/doc/html/lists.html#flatten/1"><code class="inline">lists:flatten/1</code></a>:</p><ul><li>When sending data to a port. Ports understand deep lists so there is no reason
│ │ │ │  to flatten the list before sending it to the port.</li><li>When calling BIFs that accept deep lists, such as
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#list_to_binary/1"><code class="inline">list_to_binary/1</code></a> or
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#iolist_to_binary/1"><code class="inline">iolist_to_binary/1</code></a>.</li><li>When you know that your list is only one level deep. Use <a href="../../../lib/stdlib/doc/html/lists.html#append/1"><code class="inline">lists:append/1</code></a>
│ │ │ │ -instead.</li></ul><p><em>Examples:</em></p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">port_command</span><span class="p" data-group-id="0392060563-1">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">DeepList</span><span class="p" data-group-id="0392060563-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">port_command</span><span class="p" data-group-id="0815637663-1">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">flatten</span><span class="p" data-group-id="0815637663-2">(</span><span class="n">DeepList</span><span class="p" data-group-id="0815637663-2">)</span><span class="p" data-group-id="0815637663-1">)</span></code></pre><p>A common way to send a zero-terminated string to a port is the following:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TerminatedStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="2329531482-1">[</span><span class="mi">0</span><span class="p" data-group-id="2329531482-1">]</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nf">port_command</span><span class="p" data-group-id="2329531482-2">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">TerminatedStr</span><span class="p" data-group-id="2329531482-2">)</span></code></pre><p>Instead:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TerminatedStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0345764374-1">[</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="0345764374-1">]</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nf">port_command</span><span class="p" data-group-id="0345764374-2">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">TerminatedStr</span><span class="p" data-group-id="0345764374-2">)</span></code></pre><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">append</span><span class="p" data-group-id="2636278285-1">(</span><span class="p" data-group-id="2636278285-2">[</span><span class="p" data-group-id="2636278285-3">[</span><span class="mi">1</span><span class="p" data-group-id="2636278285-3">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2636278285-4">[</span><span class="mi">2</span><span class="p" data-group-id="2636278285-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2636278285-5">[</span><span class="mi">3</span><span class="p" data-group-id="2636278285-5">]</span><span class="p" data-group-id="2636278285-2">]</span><span class="p" data-group-id="2636278285-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2636278285-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2636278285-6">]</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">flatten</span><span class="p" data-group-id="3019942738-1">(</span><span class="p" data-group-id="3019942738-2">[</span><span class="p" data-group-id="3019942738-3">[</span><span class="mi">1</span><span class="p" data-group-id="3019942738-3">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3019942738-4">[</span><span class="mi">2</span><span class="p" data-group-id="3019942738-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3019942738-5">[</span><span class="mi">3</span><span class="p" data-group-id="3019942738-5">]</span><span class="p" data-group-id="3019942738-2">]</span><span class="p" data-group-id="3019942738-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3019942738-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3019942738-6">]</span></code></pre><h2 id="recursive-list-functions" class="section-heading">
│ │ │ │ +instead.</li></ul><p><em>Examples:</em></p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">port_command</span><span class="p" data-group-id="9044717638-1">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">DeepList</span><span class="p" data-group-id="9044717638-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">port_command</span><span class="p" data-group-id="6972396824-1">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">flatten</span><span class="p" data-group-id="6972396824-2">(</span><span class="n">DeepList</span><span class="p" data-group-id="6972396824-2">)</span><span class="p" data-group-id="6972396824-1">)</span></code></pre><p>A common way to send a zero-terminated string to a port is the following:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TerminatedStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="2970082012-1">[</span><span class="mi">0</span><span class="p" data-group-id="2970082012-1">]</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">port_command</span><span class="p" data-group-id="2970082012-2">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">TerminatedStr</span><span class="p" data-group-id="2970082012-2">)</span></code></pre><p>Instead:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TerminatedStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7498517243-1">[</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="7498517243-1">]</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">port_command</span><span class="p" data-group-id="7498517243-2">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">TerminatedStr</span><span class="p" data-group-id="7498517243-2">)</span></code></pre><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">append</span><span class="p" data-group-id="1019232307-1">(</span><span class="p" data-group-id="1019232307-2">[</span><span class="p" data-group-id="1019232307-3">[</span><span class="mi">1</span><span class="p" data-group-id="1019232307-3">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1019232307-4">[</span><span class="mi">2</span><span class="p" data-group-id="1019232307-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1019232307-5">[</span><span class="mi">3</span><span class="p" data-group-id="1019232307-5">]</span><span class="p" data-group-id="1019232307-2">]</span><span class="p" data-group-id="1019232307-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1019232307-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1019232307-6">]</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">flatten</span><span class="p" data-group-id="9966022521-1">(</span><span class="p" data-group-id="9966022521-2">[</span><span class="p" data-group-id="9966022521-3">[</span><span class="mi">1</span><span class="p" data-group-id="9966022521-3">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9966022521-4">[</span><span class="mi">2</span><span class="p" data-group-id="9966022521-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9966022521-5">[</span><span class="mi">3</span><span class="p" data-group-id="9966022521-5">]</span><span class="p" data-group-id="9966022521-2">]</span><span class="p" data-group-id="9966022521-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9966022521-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9966022521-6">]</span></code></pre><h2 id="recursive-list-functions" class="section-heading">
│ │ │ │    <a href="#recursive-list-functions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Recursive List Functions</span>
│ │ │ │  </h2>
│ │ │ │  <p>There are two basic ways to write a function that traverses a list and
│ │ │ │  produces a new list.</p><p>The first way is writing a <em>body-recursive</em> function:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% Add 42 to each integer in the list.</span><span class="w">
│ │ │ │ -</span><span class="nf">add_42_body</span><span class="p" data-group-id="5351324992-1">(</span><span class="p" data-group-id="5351324992-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5351324992-2">]</span><span class="p" data-group-id="5351324992-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5351324992-3">[</span><span class="n">H</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">add_42_body</span><span class="p" data-group-id="5351324992-4">(</span><span class="n">T</span><span class="p" data-group-id="5351324992-4">)</span><span class="p" data-group-id="5351324992-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">add_42_body</span><span class="p" data-group-id="5351324992-5">(</span><span class="p" data-group-id="5351324992-6">[</span><span class="p" data-group-id="5351324992-6">]</span><span class="p" data-group-id="5351324992-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5351324992-7">[</span><span class="p" data-group-id="5351324992-7">]</span><span class="p">.</span></code></pre><p>The second way is writing a <em>tail-recursive</em> function:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% Add 42 to each integer in the list.</span><span class="w">
│ │ │ │ -</span><span class="nf">add_42_tail</span><span class="p" data-group-id="0093087899-1">(</span><span class="n">List</span><span class="p" data-group-id="0093087899-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">add_42_tail</span><span class="p" data-group-id="0093087899-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0093087899-3">[</span><span class="p" data-group-id="0093087899-3">]</span><span class="p" data-group-id="0093087899-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add_42_body</span><span class="p" data-group-id="3585249508-1">(</span><span class="p" data-group-id="3585249508-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3585249508-2">]</span><span class="p" data-group-id="3585249508-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3585249508-3">[</span><span class="n">H</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">add_42_body</span><span class="p" data-group-id="3585249508-4">(</span><span class="n">T</span><span class="p" data-group-id="3585249508-4">)</span><span class="p" data-group-id="3585249508-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">add_42_body</span><span class="p" data-group-id="3585249508-5">(</span><span class="p" data-group-id="3585249508-6">[</span><span class="p" data-group-id="3585249508-6">]</span><span class="p" data-group-id="3585249508-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3585249508-7">[</span><span class="p" data-group-id="3585249508-7">]</span><span class="p">.</span></code></pre><p>The second way is writing a <em>tail-recursive</em> function:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% Add 42 to each integer in the list.</span><span class="w">
│ │ │ │ +</span><span class="nf">add_42_tail</span><span class="p" data-group-id="6414671962-1">(</span><span class="n">List</span><span class="p" data-group-id="6414671962-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">add_42_tail</span><span class="p" data-group-id="6414671962-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6414671962-3">[</span><span class="p" data-group-id="6414671962-3">]</span><span class="p" data-group-id="6414671962-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">add_42_tail</span><span class="p" data-group-id="0093087899-4">(</span><span class="p" data-group-id="0093087899-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0093087899-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="0093087899-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">add_42_tail</span><span class="p" data-group-id="0093087899-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0093087899-7">[</span><span class="n">H</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="0093087899-7">]</span><span class="p" data-group-id="0093087899-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">add_42_tail</span><span class="p" data-group-id="0093087899-8">(</span><span class="p" data-group-id="0093087899-9">[</span><span class="p" data-group-id="0093087899-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="0093087899-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="0093087899-10">(</span><span class="n">Acc</span><span class="p" data-group-id="0093087899-10">)</span><span class="p">.</span></code></pre><p>In early versions of Erlang the tail-recursive function would typically
│ │ │ │ +</span><span class="nf">add_42_tail</span><span class="p" data-group-id="6414671962-4">(</span><span class="p" data-group-id="6414671962-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6414671962-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6414671962-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">add_42_tail</span><span class="p" data-group-id="6414671962-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6414671962-7">[</span><span class="n">H</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6414671962-7">]</span><span class="p" data-group-id="6414671962-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">add_42_tail</span><span class="p" data-group-id="6414671962-8">(</span><span class="p" data-group-id="6414671962-9">[</span><span class="p" data-group-id="6414671962-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6414671962-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="6414671962-10">(</span><span class="n">Acc</span><span class="p" data-group-id="6414671962-10">)</span><span class="p">.</span></code></pre><p>In early versions of Erlang the tail-recursive function would typically
│ │ │ │  be more efficient. In modern versions of Erlang, there is usually not
│ │ │ │  much difference in performance between a body-recursive list function and
│ │ │ │  tail-recursive function that reverses the list at the end. Therefore,
│ │ │ │  concentrate on writing beautiful code and forget about the performance
│ │ │ │  of your list functions. In the time-critical parts of your code,
│ │ │ │  <em>measure</em> before rewriting your code.</p><p>For a thorough discussion about tail and body recursion, see
│ │ │ │  <a href="http://ferd.ca/erlang-s-tail-recursion-is-not-a-silver-bullet.html">Erlang's Tail Recursion is Not a Silver Bullet</a>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>This section is about list functions that <em>construct</em> lists. A tail-recursive
│ │ │ │  function that does not construct a list runs in constant space, while the
│ │ │ │  corresponding body-recursive function uses stack space proportional to the
│ │ │ │  length of the list.</p></section><p>For example, a function that sums a list of integers, is <em>not</em> to be written as
│ │ │ │ -follows:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">recursive_sum</span><span class="p" data-group-id="2238260542-1">(</span><span class="p" data-group-id="2238260542-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2238260542-2">]</span><span class="p" data-group-id="2238260542-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">H</span><span class="o">+</span><span class="nf">recursive_sum</span><span class="p" data-group-id="2238260542-3">(</span><span class="n">T</span><span class="p" data-group-id="2238260542-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">recursive_sum</span><span class="p" data-group-id="2238260542-4">(</span><span class="p" data-group-id="2238260542-5">[</span><span class="p" data-group-id="2238260542-5">]</span><span class="p" data-group-id="2238260542-4">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p">.</span></code></pre><p>Instead:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">sum</span><span class="p" data-group-id="9605592997-1">(</span><span class="n">L</span><span class="p" data-group-id="9605592997-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">sum</span><span class="p" data-group-id="9605592997-2">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="9605592997-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +follows:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">recursive_sum</span><span class="p" data-group-id="2344823205-1">(</span><span class="p" data-group-id="2344823205-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2344823205-2">]</span><span class="p" data-group-id="2344823205-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">H</span><span class="o">+</span><span class="nf">recursive_sum</span><span class="p" data-group-id="2344823205-3">(</span><span class="n">T</span><span class="p" data-group-id="2344823205-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">recursive_sum</span><span class="p" data-group-id="2344823205-4">(</span><span class="p" data-group-id="2344823205-5">[</span><span class="p" data-group-id="2344823205-5">]</span><span class="p" data-group-id="2344823205-4">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p">.</span></code></pre><p>Instead:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">sum</span><span class="p" data-group-id="5922059289-1">(</span><span class="n">L</span><span class="p" data-group-id="5922059289-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">sum</span><span class="p" data-group-id="5922059289-2">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="5922059289-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">sum</span><span class="p" data-group-id="9605592997-3">(</span><span class="p" data-group-id="9605592997-4">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9605592997-4">]</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="9605592997-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">sum</span><span class="p" data-group-id="9605592997-5">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">H</span><span class="p" data-group-id="9605592997-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">sum</span><span class="p" data-group-id="9605592997-6">(</span><span class="p" data-group-id="9605592997-7">[</span><span class="p" data-group-id="9605592997-7">]</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="9605592997-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Sum</span><span class="p">.</span></code></pre>
│ │ │ │ +</span><span class="nf">sum</span><span class="p" data-group-id="5922059289-3">(</span><span class="p" data-group-id="5922059289-4">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5922059289-4">]</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="5922059289-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">sum</span><span class="p" data-group-id="5922059289-5">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">H</span><span class="p" data-group-id="5922059289-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">sum</span><span class="p" data-group-id="5922059289-6">(</span><span class="p" data-group-id="5922059289-7">[</span><span class="p" data-group-id="5922059289-7">]</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="5922059289-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Sum</span><span class="p">.</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/list_comprehensions.xhtml
│ │ │ │ @@ -22,37 +22,37 @@
│ │ │ │      </h1>
│ │ │ │  <h2 id="simple-examples" class="section-heading">
│ │ │ │    <a href="#simple-examples" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Simple Examples</span>
│ │ │ │  </h2>
│ │ │ │ -<p>This section starts with a simple example, showing a generator and a filter:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="3972889382-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="3972889382-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3972889382-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3972889382-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3972889382-3">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3972889382-3">]</span></code></pre><p>This is read as follows: The list of X such that X is taken from the list
│ │ │ │ +<p>This section starts with a simple example, showing a generator and a filter:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="9926322055-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="9926322055-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="9926322055-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="9926322055-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9926322055-3">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="9926322055-3">]</span></code></pre><p>This is read as follows: The list of X such that X is taken from the list
│ │ │ │  <code class="inline">[1,2,a,...]</code> and X is greater than 3.</p><p>The notation <code class="inline">X &lt;:- [1,2,a,...]</code> is a generator and the expression <code class="inline">X &gt; 3</code> is a
│ │ │ │  filter.</p><p>An additional filter, <a href="../../../lib/../erts/doc/html/erlang.html#is_integer/1"><code class="inline">is_integer(X)</code></a>, can be added to
│ │ │ │ -restrict the result to integers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="3372111688-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="3372111688-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3372111688-2">]</span><span class="p">,</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="3372111688-3">(</span><span class="n">X</span><span class="p" data-group-id="3372111688-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3372111688-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3372111688-4">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3372111688-4">]</span></code></pre><p>Generators can be combined in two ways. For example, the Cartesian product of
│ │ │ │ -two lists can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="1143022627-1">[</span><span class="p" data-group-id="1143022627-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1143022627-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="1143022627-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1143022627-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="1143022627-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1143022627-4">]</span><span class="p" data-group-id="1143022627-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1143022627-5">[</span><span class="p" data-group-id="1143022627-6">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1143022627-6">}</span><span class="p">,</span><span class="p" data-group-id="1143022627-7">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1143022627-7">}</span><span class="p">,</span><span class="p" data-group-id="1143022627-8">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1143022627-8">}</span><span class="p">,</span><span class="p" data-group-id="1143022627-9">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1143022627-9">}</span><span class="p">,</span><span class="p" data-group-id="1143022627-10">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1143022627-10">}</span><span class="p">,</span><span class="p" data-group-id="1143022627-11">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1143022627-11">}</span><span class="p" data-group-id="1143022627-5">]</span></code></pre><p>Alternatively, two lists can be zipped together using a zip generator as
│ │ │ │ -follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="9157288982-1">[</span><span class="p" data-group-id="9157288982-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9157288982-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="9157288982-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9157288982-3">]</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="9157288982-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="9157288982-4">]</span><span class="p" data-group-id="9157288982-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9157288982-5">[</span><span class="p" data-group-id="9157288982-6">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="9157288982-6">}</span><span class="p">,</span><span class="p" data-group-id="9157288982-7">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9157288982-7">}</span><span class="p">,</span><span class="p" data-group-id="9157288982-8">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="9157288982-8">}</span><span class="p" data-group-id="9157288982-5">]</span></code></pre><p>Finally, multiple elements can be emitted by the list comprehension in each iteration:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="9825573730-1">[</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">100</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="9825573730-2">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="9825573730-2">]</span><span class="p" data-group-id="9825573730-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9825573730-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">102</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">103</span><span class="p" data-group-id="9825573730-3">]</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Strict generators are used by default in the examples. More details and
│ │ │ │ +restrict the result to integers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="8772494827-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="8772494827-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8772494827-2">]</span><span class="p">,</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="8772494827-3">(</span><span class="n">X</span><span class="p" data-group-id="8772494827-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="8772494827-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8772494827-4">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8772494827-4">]</span></code></pre><p>Generators can be combined in two ways. For example, the Cartesian product of
│ │ │ │ +two lists can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="7674423670-1">[</span><span class="p" data-group-id="7674423670-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7674423670-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="7674423670-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7674423670-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="7674423670-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7674423670-4">]</span><span class="p" data-group-id="7674423670-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7674423670-5">[</span><span class="p" data-group-id="7674423670-6">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="7674423670-6">}</span><span class="p">,</span><span class="p" data-group-id="7674423670-7">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7674423670-7">}</span><span class="p">,</span><span class="p" data-group-id="7674423670-8">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="7674423670-8">}</span><span class="p">,</span><span class="p" data-group-id="7674423670-9">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7674423670-9">}</span><span class="p">,</span><span class="p" data-group-id="7674423670-10">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="7674423670-10">}</span><span class="p">,</span><span class="p" data-group-id="7674423670-11">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7674423670-11">}</span><span class="p" data-group-id="7674423670-5">]</span></code></pre><p>Alternatively, two lists can be zipped together using a zip generator as
│ │ │ │ +follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="3298925320-1">[</span><span class="p" data-group-id="3298925320-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3298925320-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="3298925320-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3298925320-3">]</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="3298925320-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3298925320-4">]</span><span class="p" data-group-id="3298925320-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3298925320-5">[</span><span class="p" data-group-id="3298925320-6">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="3298925320-6">}</span><span class="p">,</span><span class="p" data-group-id="3298925320-7">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3298925320-7">}</span><span class="p">,</span><span class="p" data-group-id="3298925320-8">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3298925320-8">}</span><span class="p" data-group-id="3298925320-5">]</span></code></pre><p>Finally, multiple elements can be emitted by the list comprehension in each iteration:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="3542192589-1">[</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">100</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="3542192589-2">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3542192589-2">]</span><span class="p" data-group-id="3542192589-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3542192589-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">102</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">103</span><span class="p" data-group-id="3542192589-3">]</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Strict generators are used by default in the examples. More details and
│ │ │ │  comparisons can be found in <a href="#strict-and-relaxed-generators">Strict and Relaxed Generators</a>.</p></section><h2 id="quick-sort" class="section-heading">
│ │ │ │    <a href="#quick-sort" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Quick Sort</span>
│ │ │ │  </h2>
│ │ │ │ -<p>The well-known quick sort routine can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">sort</span><span class="p" data-group-id="5489158152-1">(</span><span class="p" data-group-id="5489158152-2">[</span><span class="p" data-group-id="5489158152-2">]</span><span class="p" data-group-id="5489158152-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5489158152-3">[</span><span class="p" data-group-id="5489158152-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">sort</span><span class="p" data-group-id="5489158152-4">(</span><span class="p" data-group-id="5489158152-5">[</span><span class="p">_</span><span class="p" data-group-id="5489158152-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="5489158152-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">L</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">sort</span><span class="p" data-group-id="5489158152-6">(</span><span class="p" data-group-id="5489158152-7">[</span><span class="n">Pivot</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5489158152-7">]</span><span class="p" data-group-id="5489158152-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">sort</span><span class="p" data-group-id="5489158152-8">(</span><span class="p" data-group-id="5489158152-9">[</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Pivot</span><span class="p" data-group-id="5489158152-9">]</span><span class="p" data-group-id="5489158152-8">)</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5489158152-10">[</span><span class="n">Pivot</span><span class="p" data-group-id="5489158152-10">]</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ │ -    </span><span class="nf">sort</span><span class="p" data-group-id="5489158152-11">(</span><span class="p" data-group-id="5489158152-12">[</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">Pivot</span><span class="p" data-group-id="5489158152-12">]</span><span class="p" data-group-id="5489158152-11">)</span><span class="p">.</span></code></pre><p>The expression <code class="inline">[X || X &lt;:- T, X &lt; Pivot]</code> is the list of all elements in <code class="inline">T</code>
│ │ │ │ +<p>The well-known quick sort routine can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">sort</span><span class="p" data-group-id="4333803238-1">(</span><span class="p" data-group-id="4333803238-2">[</span><span class="p" data-group-id="4333803238-2">]</span><span class="p" data-group-id="4333803238-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4333803238-3">[</span><span class="p" data-group-id="4333803238-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">sort</span><span class="p" data-group-id="4333803238-4">(</span><span class="p" data-group-id="4333803238-5">[</span><span class="p">_</span><span class="p" data-group-id="4333803238-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4333803238-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">L</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">sort</span><span class="p" data-group-id="4333803238-6">(</span><span class="p" data-group-id="4333803238-7">[</span><span class="n">Pivot</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4333803238-7">]</span><span class="p" data-group-id="4333803238-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">sort</span><span class="p" data-group-id="4333803238-8">(</span><span class="p" data-group-id="4333803238-9">[</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Pivot</span><span class="p" data-group-id="4333803238-9">]</span><span class="p" data-group-id="4333803238-8">)</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4333803238-10">[</span><span class="n">Pivot</span><span class="p" data-group-id="4333803238-10">]</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ │ +    </span><span class="nf">sort</span><span class="p" data-group-id="4333803238-11">(</span><span class="p" data-group-id="4333803238-12">[</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">Pivot</span><span class="p" data-group-id="4333803238-12">]</span><span class="p" data-group-id="4333803238-11">)</span><span class="p">.</span></code></pre><p>The expression <code class="inline">[X || X &lt;:- T, X &lt; Pivot]</code> is the list of all elements in <code class="inline">T</code>
│ │ │ │  that are less than <code class="inline">Pivot</code>.</p><p><code class="inline">[X || X &lt;:- T, X &gt;= Pivot]</code> is the list of all elements in <code class="inline">T</code> that are greater
│ │ │ │  than or equal to <code class="inline">Pivot</code>.</p><p>With the algorithm above, a list is sorted as follows:</p><ul><li>A list with zero or one element is trivially sorted.</li><li>For lists with more than one element:<ol><li>The first element in the list is isolated as the pivot element.</li><li>The remaining list is partitioned into two sublists, such that:</li></ol><ul><li>The first sublist contains all elements that are smaller than the pivot
│ │ │ │  element.</li><li>The second sublist contains all elements that are greater than or equal to
│ │ │ │  the pivot element.</li></ul><ol><li>The sublists are recursively sorted by the same algorithm and the results
│ │ │ │  are combined, resulting in a list consisting of:</li></ol><ul><li>All elements from the first sublist, that is all elements smaller than the
│ │ │ │  pivot element, in sorted order.</li><li>The pivot element.</li><li>All elements from the second sublist, that is all elements greater than or
│ │ │ │  equal to the pivot element, in sorted order.</li></ul></li></ul><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>While the sorting algorithm as shown above serves as a nice example to
│ │ │ │ @@ -60,127 +60,127 @@
│ │ │ │  <a href="../../../lib/stdlib/doc/html/lists.html"><code class="inline">lists</code></a> module contains sorting functions that are implemented in a more
│ │ │ │  efficient way.</p></section><h2 id="permutations" class="section-heading">
│ │ │ │    <a href="#permutations" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Permutations</span>
│ │ │ │  </h2>
│ │ │ │ -<p>The following example generates all permutations of the elements in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">perms</span><span class="p" data-group-id="2854791261-1">(</span><span class="p" data-group-id="2854791261-2">[</span><span class="p" data-group-id="2854791261-2">]</span><span class="p" data-group-id="2854791261-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2854791261-3">[</span><span class="p" data-group-id="2854791261-4">[</span><span class="p" data-group-id="2854791261-4">]</span><span class="p" data-group-id="2854791261-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">perms</span><span class="p" data-group-id="2854791261-5">(</span><span class="n">L</span><span class="p" data-group-id="2854791261-5">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2854791261-6">[</span><span class="p" data-group-id="2854791261-7">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2854791261-7">]</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">H</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nf">perms</span><span class="p" data-group-id="2854791261-8">(</span><span class="n">L</span><span class="o">--</span><span class="p" data-group-id="2854791261-9">[</span><span class="n">H</span><span class="p" data-group-id="2854791261-9">]</span><span class="p" data-group-id="2854791261-8">)</span><span class="p" data-group-id="2854791261-6">]</span><span class="p">.</span></code></pre><p>This takes <code class="inline">H</code> from <code class="inline">L</code> in all possible ways. The result is the set of all lists
│ │ │ │ +<p>The following example generates all permutations of the elements in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">perms</span><span class="p" data-group-id="9888493556-1">(</span><span class="p" data-group-id="9888493556-2">[</span><span class="p" data-group-id="9888493556-2">]</span><span class="p" data-group-id="9888493556-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9888493556-3">[</span><span class="p" data-group-id="9888493556-4">[</span><span class="p" data-group-id="9888493556-4">]</span><span class="p" data-group-id="9888493556-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">perms</span><span class="p" data-group-id="9888493556-5">(</span><span class="n">L</span><span class="p" data-group-id="9888493556-5">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9888493556-6">[</span><span class="p" data-group-id="9888493556-7">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9888493556-7">]</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">H</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nf">perms</span><span class="p" data-group-id="9888493556-8">(</span><span class="n">L</span><span class="o">--</span><span class="p" data-group-id="9888493556-9">[</span><span class="n">H</span><span class="p" data-group-id="9888493556-9">]</span><span class="p" data-group-id="9888493556-8">)</span><span class="p" data-group-id="9888493556-6">]</span><span class="p">.</span></code></pre><p>This takes <code class="inline">H</code> from <code class="inline">L</code> in all possible ways. The result is the set of all lists
│ │ │ │  <code class="inline">[H|T]</code>, where <code class="inline">T</code> is the set of all possible permutations of <code class="inline">L</code>, with <code class="inline">H</code>
│ │ │ │ -removed:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">perms</span><span class="p" data-group-id="5443670437-1">(</span><span class="p" data-group-id="5443670437-2">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="5443670437-2">]</span><span class="p" data-group-id="5443670437-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5443670437-3">[</span><span class="p" data-group-id="5443670437-4">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="5443670437-4">]</span><span class="p">,</span><span class="p" data-group-id="5443670437-5">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">g</span><span class="p">,</span><span class="ss">u</span><span class="p" data-group-id="5443670437-5">]</span><span class="p">,</span><span class="p" data-group-id="5443670437-6">[</span><span class="ss">u</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="5443670437-6">]</span><span class="p">,</span><span class="p" data-group-id="5443670437-7">[</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="5443670437-7">]</span><span class="p">,</span><span class="p" data-group-id="5443670437-8">[</span><span class="ss">g</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p" data-group-id="5443670437-8">]</span><span class="p">,</span><span class="p" data-group-id="5443670437-9">[</span><span class="ss">g</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="5443670437-9">]</span><span class="p" data-group-id="5443670437-3">]</span></code></pre><h2 id="pythagorean-triplets" class="section-heading">
│ │ │ │ +removed:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">perms</span><span class="p" data-group-id="7418384964-1">(</span><span class="p" data-group-id="7418384964-2">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="7418384964-2">]</span><span class="p" data-group-id="7418384964-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7418384964-3">[</span><span class="p" data-group-id="7418384964-4">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="7418384964-4">]</span><span class="p">,</span><span class="p" data-group-id="7418384964-5">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">g</span><span class="p">,</span><span class="ss">u</span><span class="p" data-group-id="7418384964-5">]</span><span class="p">,</span><span class="p" data-group-id="7418384964-6">[</span><span class="ss">u</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="7418384964-6">]</span><span class="p">,</span><span class="p" data-group-id="7418384964-7">[</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7418384964-7">]</span><span class="p">,</span><span class="p" data-group-id="7418384964-8">[</span><span class="ss">g</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p" data-group-id="7418384964-8">]</span><span class="p">,</span><span class="p" data-group-id="7418384964-9">[</span><span class="ss">g</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7418384964-9">]</span><span class="p" data-group-id="7418384964-3">]</span></code></pre><h2 id="pythagorean-triplets" class="section-heading">
│ │ │ │    <a href="#pythagorean-triplets" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Pythagorean Triplets</span>
│ │ │ │  </h2>
│ │ │ │  <p>Pythagorean triplets are sets of integers <code class="inline">{A,B,C}</code> such that
│ │ │ │  <code class="inline">A**2 + B**2 = C**2</code>.</p><p>The function <code class="inline">pyth(N)</code> generates a list of all tuples <code class="inline">{A,B,C}</code> such that
│ │ │ │  <code class="inline">A**2 + B**2 = C**2</code> and where the sum of the sides is equal to, or less than,
│ │ │ │ -<code class="inline">N</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pyth</span><span class="p" data-group-id="2319829646-1">(</span><span class="n">N</span><span class="p" data-group-id="2319829646-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2319829646-2">[</span><span class="w"> </span><span class="p" data-group-id="2319829646-3">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p" data-group-id="2319829646-3">}</span><span class="w"> </span><span class="p">||</span><span class="w">
│ │ │ │ -        </span><span class="n">A</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="2319829646-4">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="2319829646-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="n">B</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="2319829646-5">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="2319829646-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="n">C</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="2319829646-6">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="2319829646-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +<code class="inline">N</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pyth</span><span class="p" data-group-id="8692727271-1">(</span><span class="n">N</span><span class="p" data-group-id="8692727271-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8692727271-2">[</span><span class="w"> </span><span class="p" data-group-id="8692727271-3">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p" data-group-id="8692727271-3">}</span><span class="w"> </span><span class="p">||</span><span class="w">
│ │ │ │ +        </span><span class="n">A</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="8692727271-4">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="8692727271-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="n">B</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="8692727271-5">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="8692727271-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="n">C</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="8692727271-6">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="8692727271-6">)</span><span class="p">,</span><span class="w">
│ │ │ │          </span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">+</span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w">
│ │ │ │          </span><span class="n">A</span><span class="o">*</span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">*</span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">C</span><span class="o">*</span><span class="n">C</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2319829646-2">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="7229429211-1">(</span><span class="mi">3</span><span class="p" data-group-id="7229429211-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7229429211-2">[</span><span class="p" data-group-id="7229429211-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="7229429211-3">(</span><span class="mi">11</span><span class="p" data-group-id="7229429211-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7229429211-4">[</span><span class="p" data-group-id="7229429211-4">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="7229429211-5">(</span><span class="mi">12</span><span class="p" data-group-id="7229429211-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7229429211-6">[</span><span class="p" data-group-id="7229429211-7">{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7229429211-7">}</span><span class="p">,</span><span class="p" data-group-id="7229429211-8">{</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7229429211-8">}</span><span class="p" data-group-id="7229429211-6">]</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="7229429211-9">(</span><span class="mi">50</span><span class="p" data-group-id="7229429211-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7229429211-10">[</span><span class="p" data-group-id="7229429211-11">{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7229429211-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7229429211-12">{</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7229429211-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7229429211-13">{</span><span class="mi">5</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="7229429211-13">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7229429211-14">{</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="7229429211-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7229429211-15">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="7229429211-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7229429211-16">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">15</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="7229429211-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7229429211-17">{</span><span class="mi">9</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="7229429211-17">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7229429211-18">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="7229429211-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7229429211-19">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="7229429211-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7229429211-20">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">16</span><span class="p">,</span><span class="mi">20</span><span class="p" data-group-id="7229429211-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7229429211-21">{</span><span class="mi">15</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="7229429211-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7229429211-22">{</span><span class="mi">16</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">20</span><span class="p" data-group-id="7229429211-22">}</span><span class="p" data-group-id="7229429211-10">]</span></code></pre><p>The following code reduces the search space and is more efficient:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pyth1</span><span class="p" data-group-id="4085222075-1">(</span><span class="n">N</span><span class="p" data-group-id="4085222075-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="4085222075-2">[</span><span class="p" data-group-id="4085222075-3">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p" data-group-id="4085222075-3">}</span><span class="w"> </span><span class="p">||</span><span class="w">
│ │ │ │ -       </span><span class="n">A</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="4085222075-4">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="4085222075-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -       </span><span class="n">B</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="4085222075-5">(</span><span class="n">A</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="4085222075-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -       </span><span class="n">C</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="4085222075-6">(</span><span class="n">B</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="4085222075-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8692727271-2">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="6753423996-1">(</span><span class="mi">3</span><span class="p" data-group-id="6753423996-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6753423996-2">[</span><span class="p" data-group-id="6753423996-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="6753423996-3">(</span><span class="mi">11</span><span class="p" data-group-id="6753423996-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6753423996-4">[</span><span class="p" data-group-id="6753423996-4">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="6753423996-5">(</span><span class="mi">12</span><span class="p" data-group-id="6753423996-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6753423996-6">[</span><span class="p" data-group-id="6753423996-7">{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="6753423996-7">}</span><span class="p">,</span><span class="p" data-group-id="6753423996-8">{</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="6753423996-8">}</span><span class="p" data-group-id="6753423996-6">]</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="6753423996-9">(</span><span class="mi">50</span><span class="p" data-group-id="6753423996-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6753423996-10">[</span><span class="p" data-group-id="6753423996-11">{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="6753423996-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6753423996-12">{</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="6753423996-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6753423996-13">{</span><span class="mi">5</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="6753423996-13">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6753423996-14">{</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="6753423996-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6753423996-15">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="6753423996-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6753423996-16">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">15</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="6753423996-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6753423996-17">{</span><span class="mi">9</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="6753423996-17">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6753423996-18">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="6753423996-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6753423996-19">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="6753423996-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6753423996-20">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">16</span><span class="p">,</span><span class="mi">20</span><span class="p" data-group-id="6753423996-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6753423996-21">{</span><span class="mi">15</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="6753423996-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6753423996-22">{</span><span class="mi">16</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">20</span><span class="p" data-group-id="6753423996-22">}</span><span class="p" data-group-id="6753423996-10">]</span></code></pre><p>The following code reduces the search space and is more efficient:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pyth1</span><span class="p" data-group-id="6397112353-1">(</span><span class="n">N</span><span class="p" data-group-id="6397112353-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="6397112353-2">[</span><span class="p" data-group-id="6397112353-3">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p" data-group-id="6397112353-3">}</span><span class="w"> </span><span class="p">||</span><span class="w">
│ │ │ │ +       </span><span class="n">A</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="6397112353-4">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="6397112353-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +       </span><span class="n">B</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="6397112353-5">(</span><span class="n">A</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="6397112353-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +       </span><span class="n">C</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="6397112353-6">(</span><span class="n">B</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="6397112353-6">)</span><span class="p">,</span><span class="w">
│ │ │ │         </span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">+</span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w">
│ │ │ │ -       </span><span class="n">A</span><span class="o">*</span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">*</span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">C</span><span class="o">*</span><span class="n">C</span><span class="w"> </span><span class="p" data-group-id="4085222075-2">]</span><span class="p">.</span></code></pre><h2 id="simplifications-with-list-comprehensions" class="section-heading">
│ │ │ │ +       </span><span class="n">A</span><span class="o">*</span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">*</span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">C</span><span class="o">*</span><span class="n">C</span><span class="w"> </span><span class="p" data-group-id="6397112353-2">]</span><span class="p">.</span></code></pre><h2 id="simplifications-with-list-comprehensions" class="section-heading">
│ │ │ │    <a href="#simplifications-with-list-comprehensions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Simplifications With List Comprehensions</span>
│ │ │ │  </h2>
│ │ │ │  <p>As an example, list comprehensions can be used to simplify some of the functions
│ │ │ │ -in <code class="inline">lists.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">append</span><span class="p" data-group-id="3710109801-1">(</span><span class="n">L</span><span class="p" data-group-id="3710109801-1">)</span><span class="w">   </span><span class="p">-&gt;</span><span class="w">  </span><span class="p" data-group-id="3710109801-2">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">L1</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L1</span><span class="p" data-group-id="3710109801-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="3710109801-3">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="3710109801-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3710109801-4">[</span><span class="n">Fun</span><span class="p" data-group-id="3710109801-5">(</span><span class="n">X</span><span class="p" data-group-id="3710109801-5">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="3710109801-4">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">filter</span><span class="p" data-group-id="3710109801-6">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="3710109801-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3710109801-7">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="3710109801-8">(</span><span class="n">X</span><span class="p" data-group-id="3710109801-8">)</span><span class="p" data-group-id="3710109801-7">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">zip</span><span class="p" data-group-id="3710109801-9">(</span><span class="n">L1</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="3710109801-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3710109801-10">[</span><span class="p" data-group-id="3710109801-11">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p" data-group-id="3710109801-11">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L1</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="3710109801-10">]</span><span class="p">.</span></code></pre><h2 id="variable-bindings-in-list-comprehensions" class="section-heading">
│ │ │ │ +in <code class="inline">lists.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">append</span><span class="p" data-group-id="0903257636-1">(</span><span class="n">L</span><span class="p" data-group-id="0903257636-1">)</span><span class="w">   </span><span class="p">-&gt;</span><span class="w">  </span><span class="p" data-group-id="0903257636-2">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">L1</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L1</span><span class="p" data-group-id="0903257636-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="0903257636-3">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0903257636-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0903257636-4">[</span><span class="n">Fun</span><span class="p" data-group-id="0903257636-5">(</span><span class="n">X</span><span class="p" data-group-id="0903257636-5">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0903257636-4">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">filter</span><span class="p" data-group-id="0903257636-6">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0903257636-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0903257636-7">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="0903257636-8">(</span><span class="n">X</span><span class="p" data-group-id="0903257636-8">)</span><span class="p" data-group-id="0903257636-7">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">zip</span><span class="p" data-group-id="0903257636-9">(</span><span class="n">L1</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="0903257636-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0903257636-10">[</span><span class="p" data-group-id="0903257636-11">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p" data-group-id="0903257636-11">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L1</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="0903257636-10">]</span><span class="p">.</span></code></pre><h2 id="variable-bindings-in-list-comprehensions" class="section-heading">
│ │ │ │    <a href="#variable-bindings-in-list-comprehensions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Variable Bindings in List Comprehensions</span>
│ │ │ │  </h2>
│ │ │ │  <p>The scope rules for variables that occur in list comprehensions are as follows:</p><ul><li>All variables that occur in a generator pattern are assumed to be &quot;fresh&quot;
│ │ │ │  variables.</li><li>Any variables that are defined before the list comprehension, and that are
│ │ │ │  used in filters, have the values they had before the list comprehension.</li><li>Variables cannot be exported from a list comprehension.</li><li>Within a zip generator, binding of all variables happens at the same time.</li></ul><p>As an example of these rules, suppose you want to write the function <code class="inline">select</code>,
│ │ │ │  which selects certain elements from a list of tuples. Suppose you write
│ │ │ │  <code class="inline">select(X, L) -&gt; [Y || {X, Y} &lt;- L].</code> with the intention of extracting all
│ │ │ │  tuples from <code class="inline">L</code>, where the first item is <code class="inline">X</code>.</p><p>Compiling this gives the following diagnostic:</p><pre><code class="text">./FileName.erl:Line: Warning: variable 'X' shadowed in generate</code></pre><p>This diagnostic warns that the variable <code class="inline">X</code> in the pattern is not the same as
│ │ │ │ -the variable <code class="inline">X</code> that occurs in the function head.</p><p>Evaluating <code class="inline">select</code> gives the following result:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">select</span><span class="p" data-group-id="1053675739-1">(</span><span class="ss">b</span><span class="p">,</span><span class="p" data-group-id="1053675739-2">[</span><span class="p" data-group-id="1053675739-3">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="1053675739-3">}</span><span class="p">,</span><span class="p" data-group-id="1053675739-4">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1053675739-4">}</span><span class="p">,</span><span class="p" data-group-id="1053675739-5">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1053675739-5">}</span><span class="p">,</span><span class="p" data-group-id="1053675739-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="1053675739-6">}</span><span class="p" data-group-id="1053675739-2">]</span><span class="p" data-group-id="1053675739-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1053675739-7">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="1053675739-7">]</span></code></pre><p>This is not the wanted result. To achieve the desired effect, <code class="inline">select</code> must be
│ │ │ │ -written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">select</span><span class="p" data-group-id="9076961507-1">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="9076961507-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="p" data-group-id="9076961507-2">[</span><span class="n">Y</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="9076961507-3">{</span><span class="n">X1</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9076961507-3">}</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">X1</span><span class="p" data-group-id="9076961507-2">]</span><span class="p">.</span></code></pre><p>The generator now contains unbound variables and the test has been moved into
│ │ │ │ -the filter.</p><p>This now works as expected:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">select</span><span class="p" data-group-id="1938060107-1">(</span><span class="ss">b</span><span class="p">,</span><span class="p" data-group-id="1938060107-2">[</span><span class="p" data-group-id="1938060107-3">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="1938060107-3">}</span><span class="p">,</span><span class="p" data-group-id="1938060107-4">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1938060107-4">}</span><span class="p">,</span><span class="p" data-group-id="1938060107-5">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1938060107-5">}</span><span class="p">,</span><span class="p" data-group-id="1938060107-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="1938060107-6">}</span><span class="p" data-group-id="1938060107-2">]</span><span class="p" data-group-id="1938060107-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1938060107-7">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="1938060107-7">]</span></code></pre><p>Also note that a variable in a generator pattern will shadow a variable with the
│ │ │ │ -same name bound in a previous generator pattern. For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="7821846570-1">[</span><span class="p" data-group-id="7821846570-2">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p" data-group-id="7821846570-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="7821846570-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7821846570-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="o">=</span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="7821846570-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="7821846570-4">]</span><span class="p" data-group-id="7821846570-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7821846570-5">[</span><span class="p" data-group-id="7821846570-6">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="7821846570-6">}</span><span class="p">,</span><span class="p" data-group-id="7821846570-7">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7821846570-7">}</span><span class="p">,</span><span class="p" data-group-id="7821846570-8">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="7821846570-8">}</span><span class="p">,</span><span class="p" data-group-id="7821846570-9">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="7821846570-9">}</span><span class="p">,</span><span class="p" data-group-id="7821846570-10">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7821846570-10">}</span><span class="p">,</span><span class="p" data-group-id="7821846570-11">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="7821846570-11">}</span><span class="p">,</span><span class="p" data-group-id="7821846570-12">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="7821846570-12">}</span><span class="p">,</span><span class="p" data-group-id="7821846570-13">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7821846570-13">}</span><span class="p">,</span><span class="p" data-group-id="7821846570-14">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="7821846570-14">}</span><span class="p" data-group-id="7821846570-5">]</span></code></pre><p>A consequence of the rules for importing variables into a list comprehension is
│ │ │ │ +the variable <code class="inline">X</code> that occurs in the function head.</p><p>Evaluating <code class="inline">select</code> gives the following result:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">select</span><span class="p" data-group-id="4267584778-1">(</span><span class="ss">b</span><span class="p">,</span><span class="p" data-group-id="4267584778-2">[</span><span class="p" data-group-id="4267584778-3">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4267584778-3">}</span><span class="p">,</span><span class="p" data-group-id="4267584778-4">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4267584778-4">}</span><span class="p">,</span><span class="p" data-group-id="4267584778-5">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4267584778-5">}</span><span class="p">,</span><span class="p" data-group-id="4267584778-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="4267584778-6">}</span><span class="p" data-group-id="4267584778-2">]</span><span class="p" data-group-id="4267584778-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4267584778-7">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="4267584778-7">]</span></code></pre><p>This is not the wanted result. To achieve the desired effect, <code class="inline">select</code> must be
│ │ │ │ +written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">select</span><span class="p" data-group-id="0702597633-1">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0702597633-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="p" data-group-id="0702597633-2">[</span><span class="n">Y</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="0702597633-3">{</span><span class="n">X1</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0702597633-3">}</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">X1</span><span class="p" data-group-id="0702597633-2">]</span><span class="p">.</span></code></pre><p>The generator now contains unbound variables and the test has been moved into
│ │ │ │ +the filter.</p><p>This now works as expected:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">select</span><span class="p" data-group-id="1913536214-1">(</span><span class="ss">b</span><span class="p">,</span><span class="p" data-group-id="1913536214-2">[</span><span class="p" data-group-id="1913536214-3">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="1913536214-3">}</span><span class="p">,</span><span class="p" data-group-id="1913536214-4">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1913536214-4">}</span><span class="p">,</span><span class="p" data-group-id="1913536214-5">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1913536214-5">}</span><span class="p">,</span><span class="p" data-group-id="1913536214-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="1913536214-6">}</span><span class="p" data-group-id="1913536214-2">]</span><span class="p" data-group-id="1913536214-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1913536214-7">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="1913536214-7">]</span></code></pre><p>Also note that a variable in a generator pattern will shadow a variable with the
│ │ │ │ +same name bound in a previous generator pattern. For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="0292205217-1">[</span><span class="p" data-group-id="0292205217-2">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p" data-group-id="0292205217-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="0292205217-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0292205217-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="o">=</span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="0292205217-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="0292205217-4">]</span><span class="p" data-group-id="0292205217-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0292205217-5">[</span><span class="p" data-group-id="0292205217-6">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="0292205217-6">}</span><span class="p">,</span><span class="p" data-group-id="0292205217-7">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="0292205217-7">}</span><span class="p">,</span><span class="p" data-group-id="0292205217-8">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="0292205217-8">}</span><span class="p">,</span><span class="p" data-group-id="0292205217-9">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="0292205217-9">}</span><span class="p">,</span><span class="p" data-group-id="0292205217-10">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="0292205217-10">}</span><span class="p">,</span><span class="p" data-group-id="0292205217-11">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="0292205217-11">}</span><span class="p">,</span><span class="p" data-group-id="0292205217-12">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="0292205217-12">}</span><span class="p">,</span><span class="p" data-group-id="0292205217-13">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="0292205217-13">}</span><span class="p">,</span><span class="p" data-group-id="0292205217-14">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="0292205217-14">}</span><span class="p" data-group-id="0292205217-5">]</span></code></pre><p>A consequence of the rules for importing variables into a list comprehension is
│ │ │ │  that certain pattern matching operations must be moved into the filters and
│ │ │ │ -cannot be written directly in the generators.</p><p>To illustrate this, do <em>not</em> write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="4062699492-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4062699492-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +cannot be written directly in the generators.</p><p>To illustrate this, do <em>not</em> write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="8031124743-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8031124743-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4062699492-2">[</span><span class="w"> </span><span class="n">Expression</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">PatternInvolving</span><span class="w"> </span><span class="n">Y</span><span class="w">  </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Expr</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4062699492-2">]</span><span class="w">
│ │ │ │ -    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Instead, write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="4435404868-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4435404868-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8031124743-2">[</span><span class="w"> </span><span class="n">Expression</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">PatternInvolving</span><span class="w"> </span><span class="n">Y</span><span class="w">  </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Expr</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8031124743-2">]</span><span class="w">
│ │ │ │ +    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Instead, write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="2274294599-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2274294599-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4435404868-2">[</span><span class="w"> </span><span class="n">Expression</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">PatternInvolving</span><span class="w"> </span><span class="n">Y1</span><span class="w">  </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Expr</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Y1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4435404868-2">]</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2274294599-2">[</span><span class="w"> </span><span class="n">Expression</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">PatternInvolving</span><span class="w"> </span><span class="n">Y1</span><span class="w">  </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Expr</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Y1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2274294599-2">]</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="strict-and-relaxed-generators" class="section-heading">
│ │ │ │    <a href="#strict-and-relaxed-generators" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Strict and Relaxed Generators</span>
│ │ │ │  </h2>
│ │ │ │  <p>Strict and relaxed generators have different behaviors when the right-hand
│ │ │ │  side expression does not match the left-hand side pattern. A relaxed generator
│ │ │ │  ignores that term and continues on. A strict generator fails with an exception.</p><p>Their difference can be shown in the following example. The generator
│ │ │ │  expects a two-tuple pattern. If a relaxed generator is used, <code class="inline">b</code> will be
│ │ │ │  silently skipped. If a strict generator is used, an exception will be raised
│ │ │ │ -when the pattern matching fails with <code class="inline">b</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4435491763-1">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4435491763-1">}</span><span class="w"> </span><span class="o">&lt;-</span><span class="w">  </span><span class="p" data-group-id="4435491763-2">[</span><span class="p" data-group-id="4435491763-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="4435491763-3">}</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="4435491763-2">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4435491763-4">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4435491763-4">}</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="4435491763-5">[</span><span class="p" data-group-id="4435491763-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="4435491763-6">}</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="4435491763-5">]</span></code></pre><p>Semantically, strict or relaxed generators convey different intentions from
│ │ │ │ +when the pattern matching fails with <code class="inline">b</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6364934704-1">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6364934704-1">}</span><span class="w"> </span><span class="o">&lt;-</span><span class="w">  </span><span class="p" data-group-id="6364934704-2">[</span><span class="p" data-group-id="6364934704-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="6364934704-3">}</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="6364934704-2">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6364934704-4">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6364934704-4">}</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="6364934704-5">[</span><span class="p" data-group-id="6364934704-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="6364934704-6">}</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="6364934704-5">]</span></code></pre><p>Semantically, strict or relaxed generators convey different intentions from
│ │ │ │  the programmer. Strict generators are used when unexpected elements in the
│ │ │ │  input data should not be tolerated. Any element not conforming to specific
│ │ │ │  patterns should immediately crash the comprehension, because the program may
│ │ │ │  not be prepared to handle it.</p><p>For example, the following comprehension is rewritten from one in the Erlang
│ │ │ │  linter. It extracts arities from all defined functions. All elements in the
│ │ │ │  list <code class="inline">DefinedFuns</code> are two-tuples, containing name and arity for functions.
│ │ │ │  If any of them differs from this pattern, it means that something has added
│ │ │ │  an invalid item into the list of defined functions. It is better for the linter
│ │ │ │  to crash in the comprehension than to skip the invalid item and continue
│ │ │ │  running. Using a strict generator here is correct, because the linter should
│ │ │ │ -not hide the presence of an internal inconsistency.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5642245818-1">[</span><span class="n">Arity</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="5642245818-2">{</span><span class="p">_</span><span class="n">FunName</span><span class="p">,</span><span class="w"> </span><span class="n">Arity</span><span class="p" data-group-id="5642245818-2">}</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">DefinedFuns</span><span class="p" data-group-id="5642245818-1">]</span></code></pre><p>In contrast, relaxed generators are used when unexpected elements in the input
│ │ │ │ +not hide the presence of an internal inconsistency.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7717437248-1">[</span><span class="n">Arity</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="7717437248-2">{</span><span class="p">_</span><span class="n">FunName</span><span class="p">,</span><span class="w"> </span><span class="n">Arity</span><span class="p" data-group-id="7717437248-2">}</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">DefinedFuns</span><span class="p" data-group-id="7717437248-1">]</span></code></pre><p>In contrast, relaxed generators are used when unexpected elements in the input
│ │ │ │  data should be <em>filtered out</em>. The programmer is aware that some elements
│ │ │ │  may not conform to specific patterns. Those elements can be safely excluded
│ │ │ │  from the comprehension result.</p><p>For example, the following comprehension is from a compiler module that
│ │ │ │  transforms normal Erlang code to Core Erlang. It finds all defined functions
│ │ │ │  from an abstract form, and outputs them in two-tuples, each containing name and
│ │ │ │  arity of a function. Not all forms are function declarations. All the forms
│ │ │ │  that are not function declarations should be ignored by this comprehension.
│ │ │ │  Using a relaxed generator here is correct, because the programmer intends to
│ │ │ │ -exclude all elements with other patterns.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6866733841-1">[</span><span class="p" data-group-id="6866733841-2">{</span><span class="n">Name</span><span class="p">,</span><span class="n">Arity</span><span class="p" data-group-id="6866733841-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="6866733841-3">{</span><span class="ss">function</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="n">Name</span><span class="p">,</span><span class="n">Arity</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6866733841-3">}</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Forms</span><span class="p" data-group-id="6866733841-1">]</span></code></pre><p>Strict and relaxed generators don't always have distinct use cases. When the
│ │ │ │ +exclude all elements with other patterns.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3341047035-1">[</span><span class="p" data-group-id="3341047035-2">{</span><span class="n">Name</span><span class="p">,</span><span class="n">Arity</span><span class="p" data-group-id="3341047035-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="3341047035-3">{</span><span class="ss">function</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="n">Name</span><span class="p">,</span><span class="n">Arity</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="3341047035-3">}</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Forms</span><span class="p" data-group-id="3341047035-1">]</span></code></pre><p>Strict and relaxed generators don't always have distinct use cases. When the
│ │ │ │  left-hand side pattern of a generator is a fresh variable, pattern matching
│ │ │ │  cannot fail. Using either strict or relaxed generators leads to the same
│ │ │ │  behavior. While the preference and use cases might be individual, it is
│ │ │ │  recommended to use strict generators when either can be used. Using strict
│ │ │ │  generators by default aligns with Erlang's &quot;Let it crash&quot; philosophy.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ ├── OEBPS/install-win32.xhtml
│ │ │ │ @@ -200,15 +200,15 @@
│ │ │ │  </span><span class="gp unselectable">$ </span><span class="">cd erts/emulator
│ │ │ │  </span><span class="gp unselectable">$ </span><span class="">make debug
│ │ │ │  </span><span class="gp unselectable">$ </span><span class="">cd ../etc
│ │ │ │  </span><span class="gp unselectable">$ </span><span class="">make debug
│ │ │ │  </span></code></pre><p>and sometimes</p><pre><code class="makeup shell" translate="no"><span class="gp unselectable">$ </span><span class="">cd $ERL_TOP
│ │ │ │  </span><span class="gp unselectable">$ </span><span class="">make local_setup
│ │ │ │  </span></code></pre><p>So now when you run <code class="inline">$ERL_TOP/erl.exe</code>, you should have a debug compiled
│ │ │ │ -emulator, which you will see if you do a:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="7765093235-1">(</span><span class="ss">system_version</span><span class="p" data-group-id="7765093235-1">)</span><span class="p">.</span></code></pre><p>in the erlang shell. If the returned string contains <code class="inline">[debug]</code>, you
│ │ │ │ +emulator, which you will see if you do a:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="9345007572-1">(</span><span class="ss">system_version</span><span class="p" data-group-id="9345007572-1">)</span><span class="p">.</span></code></pre><p>in the erlang shell. If the returned string contains <code class="inline">[debug]</code>, you
│ │ │ │  got a debug compiled emulator.</p><p>To hack the erlang libraries, you simply do a <code class="inline">make opt</code> in the
│ │ │ │  specific &quot;applications&quot; directory, like:</p><pre><code class="makeup shell" translate="no"><span class="gp unselectable">$ </span><span class="">cd $ERL_TOP/lib/stdlib
│ │ │ │  </span><span class="gp unselectable">$ </span><span class="">make opt
│ │ │ │  </span></code></pre><p>or even in the source directory...</p><pre><code class="makeup shell" translate="no"><span class="gp unselectable">$ </span><span class="">cd $ERL_TOP/lib/stdlib/src
│ │ │ │  </span><span class="gp unselectable">$ </span><span class="">make opt
│ │ │ │  </span></code></pre><p>Note that you're expected to have a fresh Erlang in your path when
│ │ │ │  doing this, preferably the plain 29 you have built in the previous
│ │ │ │ @@ -223,19 +223,19 @@
│ │ │ │  </span><span class="">:$ERL_TOP/erts/etc/win32/wsl_tools:$ERL_TOP/bootstrap/bin:$PATH
│ │ │ │  </span></code></pre><p>That should make it possible to rebuild any library without hassle...</p><p>If you want to copy a library (an application) newly built, to a
│ │ │ │  release area, you do like with the emulator:</p><pre><code class="makeup shell" translate="no"><span class="gp unselectable">$ </span><span class="">cd $ERL_TOP/lib/stdlib
│ │ │ │  </span><span class="gp unselectable">$ </span><span class="">make TESTROOT=/tmp/erlang_release release
│ │ │ │  </span></code></pre><p>Remember that:</p><ul><li><p>  Windows specific C-code goes in the <code class="inline">$ERL_TOP/erts/emulator/sys/win32</code>,
│ │ │ │  <code class="inline">$ERL_TOP/erts/emulator/drivers/win32</code> or <code class="inline">$ERL_TOP/erts/etc/win32</code>.</p></li><li><p>  Windows specific erlang code should be used conditionally and the
│ │ │ │  host OS tested in <em>runtime</em>, the exactly same beam files should be
│ │ │ │ -distributed for every platform! So write code like:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">os</span><span class="p">:</span><span class="nf">type</span><span class="p" data-group-id="9645913801-1">(</span><span class="p" data-group-id="9645913801-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9645913801-2">{</span><span class="ss">win32</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9645913801-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nf">do_windows_specific</span><span class="p" data-group-id="9645913801-3">(</span><span class="p" data-group-id="9645913801-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +distributed for every platform! So write code like:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">os</span><span class="p">:</span><span class="nf">type</span><span class="p" data-group-id="0649624484-1">(</span><span class="p" data-group-id="0649624484-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0649624484-2">{</span><span class="ss">win32</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0649624484-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nf">do_windows_specific</span><span class="p" data-group-id="0649624484-3">(</span><span class="p" data-group-id="0649624484-3">)</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="n">Other</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nf">do_fallback_or_exit</span><span class="p" data-group-id="9645913801-4">(</span><span class="p" data-group-id="9645913801-4">)</span><span class="w">
│ │ │ │ +        </span><span class="nf">do_fallback_or_exit</span><span class="p" data-group-id="0649624484-4">(</span><span class="p" data-group-id="0649624484-4">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">,</span></code></pre></li></ul><p>That's basically all you need to get going.</p><h2 id="frequently-asked-questions" class="section-heading">
│ │ │ │    <a href="#frequently-asked-questions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Frequently Asked Questions</span>
│ │ │ │  </h2>
│ │ │ │  <ul><li><p>  Q: So, now I can build Erlang using GCC on Windows?</p><p>A: No, unfortunately not. You'll need Microsoft's Visual C++
│ │ │ ├── OEBPS/included_applications.xhtml
│ │ │ │ @@ -78,72 +78,72 @@
│ │ │ │  belonging to the primary application.</p><h2 id="specifying-included-applications" class="section-heading">
│ │ │ │    <a href="#specifying-included-applications" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Specifying Included Applications</span>
│ │ │ │  </h2>
│ │ │ │  <p>Which applications to include is defined by the <code class="inline">included_applications</code> key in
│ │ │ │ -the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6545800599-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="6545800599-2">[</span><span class="p" data-group-id="6545800599-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Tree application&quot;</span><span class="p" data-group-id="6545800599-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6545800599-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="6545800599-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6545800599-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6545800599-6">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_server</span><span class="p" data-group-id="6545800599-6">]</span><span class="p" data-group-id="6545800599-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6545800599-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6545800599-8">[</span><span class="ss">prim_app_server</span><span class="p" data-group-id="6545800599-8">]</span><span class="p" data-group-id="6545800599-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6545800599-9">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6545800599-10">[</span><span class="ss">incl_app</span><span class="p" data-group-id="6545800599-10">]</span><span class="p" data-group-id="6545800599-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6545800599-11">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6545800599-12">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="6545800599-12">]</span><span class="p" data-group-id="6545800599-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6545800599-13">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6545800599-14">{</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="p" data-group-id="6545800599-15">[</span><span class="p" data-group-id="6545800599-15">]</span><span class="p" data-group-id="6545800599-14">}</span><span class="p" data-group-id="6545800599-13">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6545800599-16">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6545800599-17">[</span><span class="p" data-group-id="6545800599-18">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="6545800599-18">}</span><span class="p" data-group-id="6545800599-17">]</span><span class="p" data-group-id="6545800599-16">}</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="6545800599-2">]</span><span class="p" data-group-id="6545800599-1">}</span><span class="p">.</span></code></pre><h2 id="synchronizing-processes-during-startup" class="section-heading">
│ │ │ │ +the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0016310520-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0016310520-2">[</span><span class="p" data-group-id="0016310520-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Tree application&quot;</span><span class="p" data-group-id="0016310520-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0016310520-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="0016310520-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0016310520-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0016310520-6">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_server</span><span class="p" data-group-id="0016310520-6">]</span><span class="p" data-group-id="0016310520-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0016310520-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0016310520-8">[</span><span class="ss">prim_app_server</span><span class="p" data-group-id="0016310520-8">]</span><span class="p" data-group-id="0016310520-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0016310520-9">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0016310520-10">[</span><span class="ss">incl_app</span><span class="p" data-group-id="0016310520-10">]</span><span class="p" data-group-id="0016310520-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0016310520-11">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0016310520-12">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="0016310520-12">]</span><span class="p" data-group-id="0016310520-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0016310520-13">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0016310520-14">{</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="p" data-group-id="0016310520-15">[</span><span class="p" data-group-id="0016310520-15">]</span><span class="p" data-group-id="0016310520-14">}</span><span class="p" data-group-id="0016310520-13">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0016310520-16">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0016310520-17">[</span><span class="p" data-group-id="0016310520-18">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="0016310520-18">}</span><span class="p" data-group-id="0016310520-17">]</span><span class="p" data-group-id="0016310520-16">}</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0016310520-2">]</span><span class="p" data-group-id="0016310520-1">}</span><span class="p">.</span></code></pre><h2 id="synchronizing-processes-during-startup" class="section-heading">
│ │ │ │    <a href="#synchronizing-processes-during-startup" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Synchronizing Processes during Startup</span>
│ │ │ │  </h2>
│ │ │ │  <p>The supervisor tree of an included application is started as part of the
│ │ │ │  supervisor tree of the including application. If there is a need for
│ │ │ │  synchronization between processes in the including and included applications,
│ │ │ │  this can be achieved by using <em>start phases</em>.</p><p>Start phases are defined by the <code class="inline">start_phases</code> key in the <code class="inline">.app</code> file as a list
│ │ │ │  of tuples <code class="inline">{Phase,PhaseArgs}</code>, where <code class="inline">Phase</code> is an atom and <code class="inline">PhaseArgs</code> is a
│ │ │ │  term.</p><p>The value of the <code class="inline">mod</code> key of the including application must be set to
│ │ │ │  <code class="inline">{application_starter,[Module,StartArgs]}</code>, where <code class="inline">Module</code> as usual is the
│ │ │ │  application callback module. <code class="inline">StartArgs</code> is a term provided as argument to the
│ │ │ │ -callback function <code class="inline">Module:start/2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3136798907-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3136798907-2">[</span><span class="p" data-group-id="3136798907-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Tree application&quot;</span><span class="p" data-group-id="3136798907-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3136798907-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="3136798907-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3136798907-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3136798907-6">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_server</span><span class="p" data-group-id="3136798907-6">]</span><span class="p" data-group-id="3136798907-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3136798907-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3136798907-8">[</span><span class="ss">prim_app_server</span><span class="p" data-group-id="3136798907-8">]</span><span class="p" data-group-id="3136798907-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3136798907-9">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3136798907-10">[</span><span class="ss">incl_app</span><span class="p" data-group-id="3136798907-10">]</span><span class="p" data-group-id="3136798907-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3136798907-11">{</span><span class="ss">start_phases</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3136798907-12">[</span><span class="p" data-group-id="3136798907-13">{</span><span class="ss">init</span><span class="p">,</span><span class="p" data-group-id="3136798907-14">[</span><span class="p" data-group-id="3136798907-14">]</span><span class="p" data-group-id="3136798907-13">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3136798907-15">{</span><span class="ss">go</span><span class="p">,</span><span class="p" data-group-id="3136798907-16">[</span><span class="p" data-group-id="3136798907-16">]</span><span class="p" data-group-id="3136798907-15">}</span><span class="p" data-group-id="3136798907-12">]</span><span class="p" data-group-id="3136798907-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3136798907-17">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3136798907-18">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="3136798907-18">]</span><span class="p" data-group-id="3136798907-17">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3136798907-19">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3136798907-20">{</span><span class="ss">application_starter</span><span class="p">,</span><span class="p" data-group-id="3136798907-21">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="p" data-group-id="3136798907-22">[</span><span class="p" data-group-id="3136798907-22">]</span><span class="p" data-group-id="3136798907-21">]</span><span class="p" data-group-id="3136798907-20">}</span><span class="p" data-group-id="3136798907-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3136798907-23">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3136798907-24">[</span><span class="p" data-group-id="3136798907-25">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="3136798907-25">}</span><span class="p" data-group-id="3136798907-24">]</span><span class="p" data-group-id="3136798907-23">}</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3136798907-2">]</span><span class="p" data-group-id="3136798907-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +callback function <code class="inline">Module:start/2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0505302836-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0505302836-2">[</span><span class="p" data-group-id="0505302836-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Tree application&quot;</span><span class="p" data-group-id="0505302836-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0505302836-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="0505302836-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0505302836-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0505302836-6">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_server</span><span class="p" data-group-id="0505302836-6">]</span><span class="p" data-group-id="0505302836-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0505302836-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0505302836-8">[</span><span class="ss">prim_app_server</span><span class="p" data-group-id="0505302836-8">]</span><span class="p" data-group-id="0505302836-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0505302836-9">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0505302836-10">[</span><span class="ss">incl_app</span><span class="p" data-group-id="0505302836-10">]</span><span class="p" data-group-id="0505302836-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0505302836-11">{</span><span class="ss">start_phases</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0505302836-12">[</span><span class="p" data-group-id="0505302836-13">{</span><span class="ss">init</span><span class="p">,</span><span class="p" data-group-id="0505302836-14">[</span><span class="p" data-group-id="0505302836-14">]</span><span class="p" data-group-id="0505302836-13">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0505302836-15">{</span><span class="ss">go</span><span class="p">,</span><span class="p" data-group-id="0505302836-16">[</span><span class="p" data-group-id="0505302836-16">]</span><span class="p" data-group-id="0505302836-15">}</span><span class="p" data-group-id="0505302836-12">]</span><span class="p" data-group-id="0505302836-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0505302836-17">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0505302836-18">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="0505302836-18">]</span><span class="p" data-group-id="0505302836-17">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0505302836-19">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0505302836-20">{</span><span class="ss">application_starter</span><span class="p">,</span><span class="p" data-group-id="0505302836-21">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="p" data-group-id="0505302836-22">[</span><span class="p" data-group-id="0505302836-22">]</span><span class="p" data-group-id="0505302836-21">]</span><span class="p" data-group-id="0505302836-20">}</span><span class="p" data-group-id="0505302836-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0505302836-23">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0505302836-24">[</span><span class="p" data-group-id="0505302836-25">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="0505302836-25">}</span><span class="p" data-group-id="0505302836-24">]</span><span class="p" data-group-id="0505302836-23">}</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0505302836-2">]</span><span class="p" data-group-id="0505302836-1">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="p" data-group-id="3136798907-26">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3136798907-27">[</span><span class="p" data-group-id="3136798907-28">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Included application&quot;</span><span class="p" data-group-id="3136798907-28">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3136798907-29">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="3136798907-29">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3136798907-30">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3136798907-31">[</span><span class="ss">incl_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app_server</span><span class="p" data-group-id="3136798907-31">]</span><span class="p" data-group-id="3136798907-30">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3136798907-32">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3136798907-33">[</span><span class="p" data-group-id="3136798907-33">]</span><span class="p" data-group-id="3136798907-32">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3136798907-34">{</span><span class="ss">start_phases</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3136798907-35">[</span><span class="p" data-group-id="3136798907-36">{</span><span class="ss">go</span><span class="p">,</span><span class="p" data-group-id="3136798907-37">[</span><span class="p" data-group-id="3136798907-37">]</span><span class="p" data-group-id="3136798907-36">}</span><span class="p" data-group-id="3136798907-35">]</span><span class="p" data-group-id="3136798907-34">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3136798907-38">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3136798907-39">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="3136798907-39">]</span><span class="p" data-group-id="3136798907-38">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3136798907-40">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3136798907-41">{</span><span class="ss">incl_app_cb</span><span class="p">,</span><span class="p" data-group-id="3136798907-42">[</span><span class="p" data-group-id="3136798907-42">]</span><span class="p" data-group-id="3136798907-41">}</span><span class="p" data-group-id="3136798907-40">}</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3136798907-27">]</span><span class="p" data-group-id="3136798907-26">}</span><span class="p">.</span></code></pre><p>When starting a primary application with included applications, the primary
│ │ │ │ +</span><span class="p" data-group-id="0505302836-26">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0505302836-27">[</span><span class="p" data-group-id="0505302836-28">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Included application&quot;</span><span class="p" data-group-id="0505302836-28">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0505302836-29">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="0505302836-29">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0505302836-30">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0505302836-31">[</span><span class="ss">incl_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app_server</span><span class="p" data-group-id="0505302836-31">]</span><span class="p" data-group-id="0505302836-30">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0505302836-32">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0505302836-33">[</span><span class="p" data-group-id="0505302836-33">]</span><span class="p" data-group-id="0505302836-32">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0505302836-34">{</span><span class="ss">start_phases</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0505302836-35">[</span><span class="p" data-group-id="0505302836-36">{</span><span class="ss">go</span><span class="p">,</span><span class="p" data-group-id="0505302836-37">[</span><span class="p" data-group-id="0505302836-37">]</span><span class="p" data-group-id="0505302836-36">}</span><span class="p" data-group-id="0505302836-35">]</span><span class="p" data-group-id="0505302836-34">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0505302836-38">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0505302836-39">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="0505302836-39">]</span><span class="p" data-group-id="0505302836-38">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0505302836-40">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0505302836-41">{</span><span class="ss">incl_app_cb</span><span class="p">,</span><span class="p" data-group-id="0505302836-42">[</span><span class="p" data-group-id="0505302836-42">]</span><span class="p" data-group-id="0505302836-41">}</span><span class="p" data-group-id="0505302836-40">}</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0505302836-27">]</span><span class="p" data-group-id="0505302836-26">}</span><span class="p">.</span></code></pre><p>When starting a primary application with included applications, the primary
│ │ │ │  application is started the normal way, that is:</p><ul><li>The application controller creates an application master for the application</li><li>The application master calls <code class="inline">Module:start(normal, StartArgs)</code> to start the
│ │ │ │  top supervisor.</li></ul><p>Then, for the primary application and each included application in top-down,
│ │ │ │  left-to-right order, the application master calls
│ │ │ │  <code class="inline">Module:start_phase(Phase, Type, PhaseArgs)</code> for each phase defined for the
│ │ │ │  primary application, in that order. If a phase is not defined for an included
│ │ │ │  application, the function is not called for this phase and application.</p><p>The following requirements apply to the <code class="inline">.app</code> file for an included application:</p><ul><li>The <code class="inline">{mod, {Module,StartArgs}}</code> option must be included. This option is used
│ │ │ │  to find the callback module <code class="inline">Module</code> of the application. <code class="inline">StartArgs</code> is
│ │ │ │  ignored, as <code class="inline">Module:start/2</code> is called only for the primary application.</li><li>If the included application itself contains included applications, instead the
│ │ │ │  <code class="inline">{mod, {application_starter, [Module,StartArgs]}}</code> option must be included.</li><li>The <code class="inline">{start_phases, [{Phase,PhaseArgs}]}</code> option must be included, and the set
│ │ │ │  of specified phases must be a subset of the set of phases specified for the
│ │ │ │  primary application.</li></ul><p>When starting <code class="inline">prim_app</code> as defined above, the application controller calls the
│ │ │ │  following callback functions before <code class="inline">application:start(prim_app)</code> returns a
│ │ │ │ -value:</p><pre><code class="makeup erlang" translate="no"><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="4974649885-1">(</span><span class="ss">prim_app</span><span class="p" data-group-id="4974649885-1">)</span><span class="w">
│ │ │ │ - </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="4974649885-2">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4974649885-3">[</span><span class="p" data-group-id="4974649885-3">]</span><span class="p" data-group-id="4974649885-2">)</span><span class="w">
│ │ │ │ - </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="4974649885-4">(</span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4974649885-5">[</span><span class="p" data-group-id="4974649885-5">]</span><span class="p" data-group-id="4974649885-4">)</span><span class="w">
│ │ │ │ - </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="4974649885-6">(</span><span class="ss">go</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4974649885-7">[</span><span class="p" data-group-id="4974649885-7">]</span><span class="p" data-group-id="4974649885-6">)</span><span class="w">
│ │ │ │ - </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">incl_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="4974649885-8">(</span><span class="ss">go</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4974649885-9">[</span><span class="p" data-group-id="4974649885-9">]</span><span class="p" data-group-id="4974649885-8">)</span><span class="w">
│ │ │ │ +value:</p><pre><code class="makeup erlang" translate="no"><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="3780379043-1">(</span><span class="ss">prim_app</span><span class="p" data-group-id="3780379043-1">)</span><span class="w">
│ │ │ │ + </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="3780379043-2">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3780379043-3">[</span><span class="p" data-group-id="3780379043-3">]</span><span class="p" data-group-id="3780379043-2">)</span><span class="w">
│ │ │ │ + </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="3780379043-4">(</span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3780379043-5">[</span><span class="p" data-group-id="3780379043-5">]</span><span class="p" data-group-id="3780379043-4">)</span><span class="w">
│ │ │ │ + </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="3780379043-6">(</span><span class="ss">go</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3780379043-7">[</span><span class="p" data-group-id="3780379043-7">]</span><span class="p" data-group-id="3780379043-6">)</span><span class="w">
│ │ │ │ + </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">incl_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="3780379043-8">(</span><span class="ss">go</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3780379043-9">[</span><span class="p" data-group-id="3780379043-9">]</span><span class="p" data-group-id="3780379043-8">)</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/gen_server_concepts.xhtml
│ │ │ │ @@ -62,63 +62,63 @@
│ │ │ │    <a href="#example" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Example</span>
│ │ │ │  </h2>
│ │ │ │  <p>An example of a simple server written in plain Erlang is provided in
│ │ │ │  <a href="design_principles.xhtml#ch1">Overview</a>. The server can be reimplemented using
│ │ │ │ -<code class="inline">gen_server</code>, resulting in this callback module:</p><p><a href="" id="ex"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9613980509-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="9613980509-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="9613980509-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="9613980509-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">gen_server</code>, resulting in this callback module:</p><p><a href="" id="ex"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9317903949-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="9317903949-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="9317903949-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="9317903949-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9613980509-3">(</span><span class="p" data-group-id="9613980509-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9613980509-4">]</span><span class="p" data-group-id="9613980509-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9613980509-5">(</span><span class="p" data-group-id="9613980509-6">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9613980509-6">]</span><span class="p" data-group-id="9613980509-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9613980509-7">(</span><span class="p" data-group-id="9613980509-8">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9613980509-8">]</span><span class="p" data-group-id="9613980509-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9317903949-3">(</span><span class="p" data-group-id="9317903949-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9317903949-4">]</span><span class="p" data-group-id="9317903949-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9317903949-5">(</span><span class="p" data-group-id="9317903949-6">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9317903949-6">]</span><span class="p" data-group-id="9317903949-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9317903949-7">(</span><span class="p" data-group-id="9317903949-8">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9317903949-8">]</span><span class="p" data-group-id="9317903949-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="9613980509-9">(</span><span class="p" data-group-id="9613980509-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="9613980509-10">(</span><span class="p" data-group-id="9613980509-11">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="9613980509-11">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9613980509-12">[</span><span class="p" data-group-id="9613980509-12">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9613980509-13">[</span><span class="p" data-group-id="9613980509-13">]</span><span class="p" data-group-id="9613980509-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="9317903949-9">(</span><span class="p" data-group-id="9317903949-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="9317903949-10">(</span><span class="p" data-group-id="9317903949-11">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="9317903949-11">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9317903949-12">[</span><span class="p" data-group-id="9317903949-12">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9317903949-13">[</span><span class="p" data-group-id="9317903949-13">]</span><span class="p" data-group-id="9317903949-10">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="9613980509-14">(</span><span class="p" data-group-id="9613980509-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="9613980509-15">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="9613980509-15">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="9317903949-14">(</span><span class="p" data-group-id="9317903949-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="9317903949-15">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="9317903949-15">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="9613980509-16">(</span><span class="n">Ch</span><span class="p" data-group-id="9613980509-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="9613980509-17">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9613980509-18">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9613980509-18">}</span><span class="p" data-group-id="9613980509-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="9317903949-16">(</span><span class="n">Ch</span><span class="p" data-group-id="9317903949-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="9317903949-17">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9317903949-18">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9317903949-18">}</span><span class="p" data-group-id="9317903949-17">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="9613980509-19">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="9613980509-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9613980509-20">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="9613980509-21">(</span><span class="p" data-group-id="9613980509-21">)</span><span class="p" data-group-id="9613980509-20">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="9317903949-19">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="9317903949-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9317903949-20">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="9317903949-21">(</span><span class="p" data-group-id="9317903949-21">)</span><span class="p" data-group-id="9317903949-20">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="9613980509-22">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9613980509-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9613980509-23">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9613980509-23">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="9613980509-24">(</span><span class="n">Chs</span><span class="p" data-group-id="9613980509-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9613980509-25">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9613980509-25">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="9317903949-22">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9317903949-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9317903949-23">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9317903949-23">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="9317903949-24">(</span><span class="n">Chs</span><span class="p" data-group-id="9317903949-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9317903949-25">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9317903949-25">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="9613980509-26">(</span><span class="p" data-group-id="9613980509-27">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9613980509-27">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9613980509-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="9613980509-28">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9613980509-28">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9613980509-29">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9613980509-29">}</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><h2 id="starting-a-gen_server" class="section-heading">
│ │ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="9317903949-26">(</span><span class="p" data-group-id="9317903949-27">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9317903949-27">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9317903949-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="9317903949-28">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9317903949-28">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9317903949-29">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9317903949-29">}</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><h2 id="starting-a-gen_server" class="section-heading">
│ │ │ │    <a href="#starting-a-gen_server" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Starting a Gen_Server</span>
│ │ │ │  </h2>
│ │ │ │  <p>In the example in the previous section, <code class="inline">gen_server</code> is started by calling
│ │ │ │ -<code class="inline">ch3:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="0504949932-1">(</span><span class="p" data-group-id="0504949932-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="0504949932-2">(</span><span class="p" data-group-id="0504949932-3">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="0504949932-3">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0504949932-4">[</span><span class="p" data-group-id="0504949932-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0504949932-5">[</span><span class="p" data-group-id="0504949932-5">]</span><span class="p" data-group-id="0504949932-2">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="0504949932-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="0504949932-6">}</span></code></pre><p><code class="inline">start_link/0</code> calls function <a href="../../../lib/stdlib/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a>.  This function
│ │ │ │ +<code class="inline">ch3:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="5759738214-1">(</span><span class="p" data-group-id="5759738214-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="5759738214-2">(</span><span class="p" data-group-id="5759738214-3">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="5759738214-3">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5759738214-4">[</span><span class="p" data-group-id="5759738214-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5759738214-5">[</span><span class="p" data-group-id="5759738214-5">]</span><span class="p" data-group-id="5759738214-2">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5759738214-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="5759738214-6">}</span></code></pre><p><code class="inline">start_link/0</code> calls function <a href="../../../lib/stdlib/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a>.  This function
│ │ │ │  spawns and links to a new process, a <code class="inline">gen_server</code>.</p><ul><li><p>The first argument, <code class="inline">{local, ch3}</code>, specifies the name.
│ │ │ │  The gen_server is then locally registered as <code class="inline">ch3</code>.</p><p>If the name is omitted, the <code class="inline">gen_server</code> is not registered. Instead its pid
│ │ │ │  must be used. The name can also be given as <code class="inline">{global, Name}</code>, in which case
│ │ │ │  the <code class="inline">gen_server</code> is registered using <a href="../../../lib/kernel/doc/html/global.html#register_name/2"><code class="inline">global:register_name/2</code></a>.</p></li><li><p>The second argument, <code class="inline">ch3</code>, is the name of the callback module, which is
│ │ │ │  the module where the callback functions are located.</p><p>The interface functions (<code class="inline">start_link/0</code>, <code class="inline">alloc/0</code>, and <code class="inline">free/1</code>) are located
│ │ │ │  in the same module as the callback functions (<code class="inline">init/1</code>, <code class="inline">handle_call/3</code>, and
│ │ │ │  <code class="inline">handle_cast/2</code>). It is usually good programming practice to have the code
│ │ │ │  corresponding to one process contained in a single module.</p></li><li><p>The third argument, <code class="inline">[]</code>, is a term that is passed as is to the callback
│ │ │ │  function <code class="inline">init</code>. Here, <code class="inline">init</code> does not need any indata and ignores the
│ │ │ │  argument.</p></li><li><p>The fourth argument, <code class="inline">[]</code>, is a list of options. See <a href="../../../lib/stdlib/doc/html/gen_server.html"><code class="inline">gen_server</code></a>
│ │ │ │  for the available options.</p></li></ul><p>If name registration succeeds, the new <code class="inline">gen_server</code> process calls the callback
│ │ │ │  function <code class="inline">ch3:init([])</code>. <code class="inline">init</code> is expected to return <code class="inline">{ok, State}</code>, where
│ │ │ │  <code class="inline">State</code> is the internal state of the <code class="inline">gen_server</code>. In this case, the state is
│ │ │ │ -the available channels.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="1723878011-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="1723878011-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1723878011-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="1723878011-3">(</span><span class="p" data-group-id="1723878011-3">)</span><span class="p" data-group-id="1723878011-2">}</span><span class="p">.</span></code></pre><p><a href="../../../lib/stdlib/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a> is synchronous. It does not return until the
│ │ │ │ +the available channels.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="7160413549-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="7160413549-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7160413549-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="7160413549-3">(</span><span class="p" data-group-id="7160413549-3">)</span><span class="p" data-group-id="7160413549-2">}</span><span class="p">.</span></code></pre><p><a href="../../../lib/stdlib/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a> is synchronous. It does not return until the
│ │ │ │  <code class="inline">gen_server</code> has been initialized and is ready to receive requests.</p><p><a href="../../../lib/stdlib/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a> must be used if the <code class="inline">gen_server</code> is part of
│ │ │ │  a supervision tree, meaning that it was started by a supervisor. There
│ │ │ │  is another function, <a href="../../../lib/stdlib/doc/html/gen_server.html#start/4"><code class="inline">gen_server:start/4</code></a>, to start a standalone
│ │ │ │  <code class="inline">gen_server</code> that is not part of a supervision tree.</p><h2 id="synchronous-requests-call" class="section-heading">
│ │ │ │    <a href="#synchronous-requests-call" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │ @@ -126,32 +126,32 @@
│ │ │ │  </h2>
│ │ │ │  <p>The synchronous request <code class="inline">alloc()</code> is implemented using <a href="../../../lib/stdlib/doc/html/gen_server.html#call/2"><code class="inline">gen_server:call/2</code></a>:</p><pre><code class="text">alloc() -&gt;
│ │ │ │      gen_server:call(ch3, alloc).</code></pre><p><code class="inline">ch3</code> is the name of the <code class="inline">gen_server</code> and must agree with the name
│ │ │ │  used to start it. <code class="inline">alloc</code> is the actual request.</p><p>The request is made into a message and sent to the <code class="inline">gen_server</code>.
│ │ │ │  When the request is received, the <code class="inline">gen_server</code> calls
│ │ │ │  <code class="inline">handle_call(Request, From, State)</code>, which is expected to return
│ │ │ │  a tuple <code class="inline">{reply,Reply,State1}</code>. <code class="inline">Reply</code> is the reply that is to be sent back
│ │ │ │ -to the client, and <code class="inline">State1</code> is a new value for the state of the <code class="inline">gen_server</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_call</span><span class="p" data-group-id="9578547053-1">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9578547053-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9578547053-2">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9578547053-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="9578547053-3">(</span><span class="n">Chs</span><span class="p" data-group-id="9578547053-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9578547053-4">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9578547053-4">}</span><span class="p">.</span></code></pre><p>In this case, the reply is the allocated channel <code class="inline">Ch</code> and the new state is the
│ │ │ │ +to the client, and <code class="inline">State1</code> is a new value for the state of the <code class="inline">gen_server</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_call</span><span class="p" data-group-id="7013050052-1">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="7013050052-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7013050052-2">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="7013050052-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="7013050052-3">(</span><span class="n">Chs</span><span class="p" data-group-id="7013050052-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7013050052-4">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="7013050052-4">}</span><span class="p">.</span></code></pre><p>In this case, the reply is the allocated channel <code class="inline">Ch</code> and the new state is the
│ │ │ │  set of remaining available channels <code class="inline">Chs2</code>.</p><p>Thus, the call <code class="inline">ch3:alloc()</code> returns the allocated channel <code class="inline">Ch</code> and the
│ │ │ │  <code class="inline">gen_server</code> then waits for new requests, now with an updated list of
│ │ │ │  available channels.</p><h2 id="asynchronous-requests-cast" class="section-heading">
│ │ │ │    <a href="#asynchronous-requests-cast" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Asynchronous Requests - Cast</span>
│ │ │ │  </h2>
│ │ │ │ -<p>The asynchronous request <code class="inline">free(Ch)</code> is implemented using <a href="../../../lib/stdlib/doc/html/gen_server.html#cast/2"><code class="inline">gen_server:cast/2</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">free</span><span class="p" data-group-id="3842345965-1">(</span><span class="n">Ch</span><span class="p" data-group-id="3842345965-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="3842345965-2">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3842345965-3">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3842345965-3">}</span><span class="p" data-group-id="3842345965-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch3</code> is the name of the <code class="inline">gen_server</code>. <code class="inline">{free, Ch}</code> is the actual request.</p><p>The request is made into a message and sent to the <code class="inline">gen_server</code>.
│ │ │ │ +<p>The asynchronous request <code class="inline">free(Ch)</code> is implemented using <a href="../../../lib/stdlib/doc/html/gen_server.html#cast/2"><code class="inline">gen_server:cast/2</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">free</span><span class="p" data-group-id="9168091655-1">(</span><span class="n">Ch</span><span class="p" data-group-id="9168091655-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="9168091655-2">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9168091655-3">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9168091655-3">}</span><span class="p" data-group-id="9168091655-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch3</code> is the name of the <code class="inline">gen_server</code>. <code class="inline">{free, Ch}</code> is the actual request.</p><p>The request is made into a message and sent to the <code class="inline">gen_server</code>.
│ │ │ │  <code class="inline">cast</code>, and thus <code class="inline">free</code>, then returns <code class="inline">ok</code>.</p><p>When the request is received, the <code class="inline">gen_server</code> calls
│ │ │ │  <code class="inline">handle_cast(Request, State)</code>, which is expected to return a tuple
│ │ │ │ -<code class="inline">{noreply,State1}</code>. <code class="inline">State1</code> is a new value for the state of the <code class="inline">gen_server</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_cast</span><span class="p" data-group-id="2661217150-1">(</span><span class="p" data-group-id="2661217150-2">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2661217150-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2661217150-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="2661217150-3">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2661217150-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2661217150-4">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="2661217150-4">}</span><span class="p">.</span></code></pre><p>In this case, the new state is the updated list of available channels <code class="inline">Chs2</code>.
│ │ │ │ +<code class="inline">{noreply,State1}</code>. <code class="inline">State1</code> is a new value for the state of the <code class="inline">gen_server</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_cast</span><span class="p" data-group-id="0342941502-1">(</span><span class="p" data-group-id="0342941502-2">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="0342941502-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="0342941502-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="0342941502-3">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="0342941502-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0342941502-4">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="0342941502-4">}</span><span class="p">.</span></code></pre><p>In this case, the new state is the updated list of available channels <code class="inline">Chs2</code>.
│ │ │ │  The <code class="inline">gen_server</code> is now ready for new requests.</p><h2 id="stopping" class="section-heading">
│ │ │ │    <a href="#stopping" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Stopping</span>
│ │ │ │  </h2>
│ │ │ │  <h3 id="in-a-supervision-tree" class="section-heading">
│ │ │ │ @@ -162,65 +162,65 @@
│ │ │ │  </h3>
│ │ │ │  <p>If the <code class="inline">gen_server</code> is part of a supervision tree, no stop function is needed.
│ │ │ │  The <code class="inline">gen_server</code> is automatically terminated by its supervisor.  Exactly how
│ │ │ │  this is done is defined by a <a href="sup_princ.xhtml#shutdown">shutdown strategy</a>
│ │ │ │  set in the supervisor.</p><p>If it is necessary to clean up before termination, the shutdown strategy
│ │ │ │  must be a time-out value and the <code class="inline">gen_server</code> must be set to trap exit signals
│ │ │ │  in function <code class="inline">init</code>. When ordered to shut down, the <code class="inline">gen_server</code> then calls
│ │ │ │ -the callback function <code class="inline">terminate(shutdown, State)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="5848975880-1">(</span><span class="n">Args</span><span class="p" data-group-id="5848975880-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +the callback function <code class="inline">terminate(shutdown, State)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="3771648232-1">(</span><span class="n">Args</span><span class="p" data-group-id="3771648232-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="5848975880-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="5848975880-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="3771648232-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3771648232-2">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5848975880-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5848975880-3">}</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3771648232-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="3771648232-3">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="5848975880-4">(</span><span class="ss">shutdown</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5848975880-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="3771648232-4">(</span><span class="ss">shutdown</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="3771648232-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Code for cleaning up here</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><h3 id="standalone-gen_servers" class="section-heading">
│ │ │ │    <a href="#standalone-gen_servers" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Standalone Gen_Servers</span>
│ │ │ │  </h3>
│ │ │ │  <p>If the <code class="inline">gen_server</code> is not part of a supervision tree, a stop function
│ │ │ │  can be useful, for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8241130017-1">(</span><span class="p" data-group-id="8241130017-2">[</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8241130017-2">]</span><span class="p" data-group-id="8241130017-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6971791752-1">(</span><span class="p" data-group-id="6971791752-2">[</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6971791752-2">]</span><span class="p" data-group-id="6971791752-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="8241130017-3">(</span><span class="p" data-group-id="8241130017-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="8241130017-4">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p" data-group-id="8241130017-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="6971791752-3">(</span><span class="p" data-group-id="6971791752-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="6971791752-4">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p" data-group-id="6971791752-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="8241130017-5">(</span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8241130017-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8241130017-6">{</span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8241130017-6">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="8241130017-7">(</span><span class="p" data-group-id="8241130017-8">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="8241130017-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8241130017-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="6971791752-5">(</span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="6971791752-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6971791752-6">{</span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="6971791752-6">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="6971791752-7">(</span><span class="p" data-group-id="6971791752-8">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="6971791752-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="6971791752-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="8241130017-9">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8241130017-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="6971791752-9">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="6971791752-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The callback function handling the <code class="inline">stop</code> request returns a tuple
│ │ │ │  <code class="inline">{stop,normal,State1}</code>, where <code class="inline">normal</code> specifies that it is
│ │ │ │  a normal termination and <code class="inline">State1</code> is a new value for the state
│ │ │ │  of the <code class="inline">gen_server</code>.  This causes the <code class="inline">gen_server</code> to call
│ │ │ │  <code class="inline">terminate(normal, State1)</code> and then it terminates gracefully.</p><h2 id="handling-other-messages" class="section-heading">
│ │ │ │    <a href="#handling-other-messages" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Handling Other Messages</span>
│ │ │ │  </h2>
│ │ │ │  <p>If the <code class="inline">gen_server</code> is to be able to receive other messages than requests,
│ │ │ │  the callback function <code class="inline">handle_info(Info, State)</code> must be implemented
│ │ │ │  to handle them.  Examples of other messages are exit messages,
│ │ │ │  if the <code class="inline">gen_server</code> is linked to other processes than the supervisor
│ │ │ │ -and it is trapping exit signals.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_info</span><span class="p" data-group-id="2082406383-1">(</span><span class="p" data-group-id="2082406383-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="2082406383-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2082406383-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +and it is trapping exit signals.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_info</span><span class="p" data-group-id="0051028877-1">(</span><span class="p" data-group-id="0051028877-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="0051028877-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0051028877-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Code to handle exits here.</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2082406383-3">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="2082406383-3">}</span><span class="p">.</span></code></pre><p>The final function to implement is <code class="inline">code_change/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="5883334843-1">(</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="5883334843-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0051028877-3">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="0051028877-3">}</span><span class="p">.</span></code></pre><p>The final function to implement is <code class="inline">code_change/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="4128669365-1">(</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="4128669365-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Code to convert state (and more) during code change.</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5883334843-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NewState</span><span class="p" data-group-id="5883334843-2">}</span><span class="p">.</span></code></pre>
│ │ │ │ +    </span><span class="p" data-group-id="4128669365-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NewState</span><span class="p" data-group-id="4128669365-2">}</span><span class="p">.</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/funs.xhtml
│ │ │ │ @@ -22,399 +22,399 @@
│ │ │ │      </h1>
│ │ │ │  <h2 id="map" class="section-heading">
│ │ │ │    <a href="#map" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">map</span>
│ │ │ │  </h2>
│ │ │ │ -<p>The following function, <code class="inline">double</code>, doubles every element in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">double</span><span class="p" data-group-id="0989623000-1">(</span><span class="p" data-group-id="0989623000-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0989623000-2">]</span><span class="p" data-group-id="0989623000-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0989623000-3">[</span><span class="mi">2</span><span class="o">*</span><span class="n">H</span><span class="p">|</span><span class="nf">double</span><span class="p" data-group-id="0989623000-4">(</span><span class="n">T</span><span class="p" data-group-id="0989623000-4">)</span><span class="p" data-group-id="0989623000-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">double</span><span class="p" data-group-id="0989623000-5">(</span><span class="p" data-group-id="0989623000-6">[</span><span class="p" data-group-id="0989623000-6">]</span><span class="p" data-group-id="0989623000-5">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0989623000-7">[</span><span class="p" data-group-id="0989623000-7">]</span><span class="p">.</span></code></pre><p>Hence, the argument entered as input is doubled as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">double</span><span class="p" data-group-id="9418133081-1">(</span><span class="p" data-group-id="9418133081-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9418133081-2">]</span><span class="p" data-group-id="9418133081-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9418133081-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p" data-group-id="9418133081-3">]</span></code></pre><p>The following function, <code class="inline">add_one</code>, adds one to every element in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_one</span><span class="p" data-group-id="4733386257-1">(</span><span class="p" data-group-id="4733386257-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4733386257-2">]</span><span class="p" data-group-id="4733386257-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4733386257-3">[</span><span class="n">H</span><span class="o">+</span><span class="mi">1</span><span class="p">|</span><span class="nf">add_one</span><span class="p" data-group-id="4733386257-4">(</span><span class="n">T</span><span class="p" data-group-id="4733386257-4">)</span><span class="p" data-group-id="4733386257-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">add_one</span><span class="p" data-group-id="4733386257-5">(</span><span class="p" data-group-id="4733386257-6">[</span><span class="p" data-group-id="4733386257-6">]</span><span class="p" data-group-id="4733386257-5">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4733386257-7">[</span><span class="p" data-group-id="4733386257-7">]</span><span class="p">.</span></code></pre><p>The functions <code class="inline">double</code> and <code class="inline">add_one</code> have a similar structure. This can be used
│ │ │ │ -by writing a function <code class="inline">map</code> that expresses this similarity:</p><pre><code class="makeup erlang" translate="no"><span class="nf">map</span><span class="p" data-group-id="6984548818-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6984548818-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6984548818-2">]</span><span class="p" data-group-id="6984548818-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6984548818-3">[</span><span class="n">F</span><span class="p" data-group-id="6984548818-4">(</span><span class="n">H</span><span class="p" data-group-id="6984548818-4">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="6984548818-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="6984548818-5">)</span><span class="p" data-group-id="6984548818-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="6984548818-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6984548818-7">[</span><span class="p" data-group-id="6984548818-7">]</span><span class="p" data-group-id="6984548818-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6984548818-8">[</span><span class="p" data-group-id="6984548818-8">]</span><span class="p">.</span></code></pre><p>The functions <code class="inline">double</code> and <code class="inline">add_one</code> can now be expressed in terms of <code class="inline">map</code> as
│ │ │ │ -follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">double</span><span class="p" data-group-id="5764420654-1">(</span><span class="n">L</span><span class="p" data-group-id="5764420654-1">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="5764420654-2">(</span><span class="nf">fun</span><span class="p" data-group-id="5764420654-3">(</span><span class="n">X</span><span class="p" data-group-id="5764420654-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="o">*</span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="5764420654-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add_one</span><span class="p" data-group-id="5764420654-4">(</span><span class="n">L</span><span class="p" data-group-id="5764420654-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="5764420654-5">(</span><span class="nf">fun</span><span class="p" data-group-id="5764420654-6">(</span><span class="n">X</span><span class="p" data-group-id="5764420654-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="5764420654-5">)</span><span class="p">.</span></code></pre><p><code class="inline">map(F, List)</code> is a function that takes a function <code class="inline">F</code> and a list <code class="inline">L</code> as
│ │ │ │ +<p>The following function, <code class="inline">double</code>, doubles every element in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">double</span><span class="p" data-group-id="9966933380-1">(</span><span class="p" data-group-id="9966933380-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9966933380-2">]</span><span class="p" data-group-id="9966933380-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9966933380-3">[</span><span class="mi">2</span><span class="o">*</span><span class="n">H</span><span class="p">|</span><span class="nf">double</span><span class="p" data-group-id="9966933380-4">(</span><span class="n">T</span><span class="p" data-group-id="9966933380-4">)</span><span class="p" data-group-id="9966933380-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">double</span><span class="p" data-group-id="9966933380-5">(</span><span class="p" data-group-id="9966933380-6">[</span><span class="p" data-group-id="9966933380-6">]</span><span class="p" data-group-id="9966933380-5">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9966933380-7">[</span><span class="p" data-group-id="9966933380-7">]</span><span class="p">.</span></code></pre><p>Hence, the argument entered as input is doubled as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">double</span><span class="p" data-group-id="9234271294-1">(</span><span class="p" data-group-id="9234271294-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9234271294-2">]</span><span class="p" data-group-id="9234271294-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9234271294-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p" data-group-id="9234271294-3">]</span></code></pre><p>The following function, <code class="inline">add_one</code>, adds one to every element in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_one</span><span class="p" data-group-id="6045251051-1">(</span><span class="p" data-group-id="6045251051-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6045251051-2">]</span><span class="p" data-group-id="6045251051-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6045251051-3">[</span><span class="n">H</span><span class="o">+</span><span class="mi">1</span><span class="p">|</span><span class="nf">add_one</span><span class="p" data-group-id="6045251051-4">(</span><span class="n">T</span><span class="p" data-group-id="6045251051-4">)</span><span class="p" data-group-id="6045251051-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">add_one</span><span class="p" data-group-id="6045251051-5">(</span><span class="p" data-group-id="6045251051-6">[</span><span class="p" data-group-id="6045251051-6">]</span><span class="p" data-group-id="6045251051-5">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6045251051-7">[</span><span class="p" data-group-id="6045251051-7">]</span><span class="p">.</span></code></pre><p>The functions <code class="inline">double</code> and <code class="inline">add_one</code> have a similar structure. This can be used
│ │ │ │ +by writing a function <code class="inline">map</code> that expresses this similarity:</p><pre><code class="makeup erlang" translate="no"><span class="nf">map</span><span class="p" data-group-id="3809759575-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3809759575-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3809759575-2">]</span><span class="p" data-group-id="3809759575-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3809759575-3">[</span><span class="n">F</span><span class="p" data-group-id="3809759575-4">(</span><span class="n">H</span><span class="p" data-group-id="3809759575-4">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="3809759575-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="3809759575-5">)</span><span class="p" data-group-id="3809759575-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="3809759575-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3809759575-7">[</span><span class="p" data-group-id="3809759575-7">]</span><span class="p" data-group-id="3809759575-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3809759575-8">[</span><span class="p" data-group-id="3809759575-8">]</span><span class="p">.</span></code></pre><p>The functions <code class="inline">double</code> and <code class="inline">add_one</code> can now be expressed in terms of <code class="inline">map</code> as
│ │ │ │ +follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">double</span><span class="p" data-group-id="8392088181-1">(</span><span class="n">L</span><span class="p" data-group-id="8392088181-1">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="8392088181-2">(</span><span class="nf">fun</span><span class="p" data-group-id="8392088181-3">(</span><span class="n">X</span><span class="p" data-group-id="8392088181-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="o">*</span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="8392088181-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add_one</span><span class="p" data-group-id="8392088181-4">(</span><span class="n">L</span><span class="p" data-group-id="8392088181-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="8392088181-5">(</span><span class="nf">fun</span><span class="p" data-group-id="8392088181-6">(</span><span class="n">X</span><span class="p" data-group-id="8392088181-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="8392088181-5">)</span><span class="p">.</span></code></pre><p><code class="inline">map(F, List)</code> is a function that takes a function <code class="inline">F</code> and a list <code class="inline">L</code> as
│ │ │ │  arguments and returns a new list, obtained by applying <code class="inline">F</code> to each of the
│ │ │ │  elements in <code class="inline">L</code>.</p><p>The process of abstracting out the common features of a number of different
│ │ │ │  programs is called <em>procedural abstraction</em>. Procedural abstraction can be used
│ │ │ │  to write several different functions that have a similar structure, but differ
│ │ │ │  in some minor detail. This is done as follows:</p><ol><li><em>Step 1.</em> Write one function that represents the common features of these
│ │ │ │  functions.</li><li><em>Step 2.</em> Parameterize the difference in terms of functions that are passed
│ │ │ │  as arguments to the common function.</li></ol><h2 id="foreach" class="section-heading">
│ │ │ │    <a href="#foreach" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">foreach</span>
│ │ │ │  </h2>
│ │ │ │  <p>This section illustrates procedural abstraction. Initially, the following two
│ │ │ │ -examples are written as conventional functions.</p><p>This function prints all elements of a list onto a stream:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="7623556314-1">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7623556314-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7623556314-2">]</span><span class="p" data-group-id="7623556314-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7623556314-3">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7623556314-4">[</span><span class="n">H</span><span class="p" data-group-id="7623556314-4">]</span><span class="p" data-group-id="7623556314-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">print_list</span><span class="p" data-group-id="7623556314-5">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7623556314-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">print_list</span><span class="p" data-group-id="7623556314-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7623556314-7">[</span><span class="p" data-group-id="7623556314-7">]</span><span class="p" data-group-id="7623556314-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">true</span><span class="p">.</span></code></pre><p>This function broadcasts a message to a list of processes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">broadcast</span><span class="p" data-group-id="0208410853-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0208410853-2">[</span><span class="n">Pid</span><span class="p">|</span><span class="n">Pids</span><span class="p" data-group-id="0208410853-2">]</span><span class="p" data-group-id="0208410853-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +examples are written as conventional functions.</p><p>This function prints all elements of a list onto a stream:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="7163455625-1">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7163455625-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7163455625-2">]</span><span class="p" data-group-id="7163455625-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7163455625-3">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7163455625-4">[</span><span class="n">H</span><span class="p" data-group-id="7163455625-4">]</span><span class="p" data-group-id="7163455625-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">print_list</span><span class="p" data-group-id="7163455625-5">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7163455625-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">print_list</span><span class="p" data-group-id="7163455625-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7163455625-7">[</span><span class="p" data-group-id="7163455625-7">]</span><span class="p" data-group-id="7163455625-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">true</span><span class="p">.</span></code></pre><p>This function broadcasts a message to a list of processes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">broadcast</span><span class="p" data-group-id="3545546503-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3545546503-2">[</span><span class="n">Pid</span><span class="p">|</span><span class="n">Pids</span><span class="p" data-group-id="3545546503-2">]</span><span class="p" data-group-id="3545546503-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Msg</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">broadcast</span><span class="p" data-group-id="0208410853-3">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">Pids</span><span class="p" data-group-id="0208410853-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">broadcast</span><span class="p" data-group-id="0208410853-4">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0208410853-5">[</span><span class="p" data-group-id="0208410853-5">]</span><span class="p" data-group-id="0208410853-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">broadcast</span><span class="p" data-group-id="3545546503-3">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">Pids</span><span class="p" data-group-id="3545546503-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">broadcast</span><span class="p" data-group-id="3545546503-4">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3545546503-5">[</span><span class="p" data-group-id="3545546503-5">]</span><span class="p" data-group-id="3545546503-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">true</span><span class="p">.</span></code></pre><p>These two functions have a similar structure. They both iterate over a list and
│ │ │ │  do something to each element in the list. The &quot;something&quot; is passed on as an
│ │ │ │ -extra argument to the function that does this.</p><p>The function <code class="inline">foreach</code> expresses this similarity:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="4477983863-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4477983863-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4477983863-2">]</span><span class="p" data-group-id="4477983863-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">F</span><span class="p" data-group-id="4477983863-3">(</span><span class="n">H</span><span class="p" data-group-id="4477983863-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="4477983863-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="4477983863-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">foreach</span><span class="p" data-group-id="4477983863-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4477983863-6">[</span><span class="p" data-group-id="4477983863-6">]</span><span class="p" data-group-id="4477983863-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>Using the function <code class="inline">foreach</code>, the function <code class="inline">print_list</code> becomes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="0131287495-1">(</span><span class="nf">fun</span><span class="p" data-group-id="0131287495-2">(</span><span class="n">H</span><span class="p" data-group-id="0131287495-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0131287495-3">(</span><span class="n">S</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="0131287495-4">[</span><span class="n">H</span><span class="p" data-group-id="0131287495-4">]</span><span class="p" data-group-id="0131287495-3">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0131287495-1">)</span></code></pre><p>Using the function <code class="inline">foreach</code>, the function <code class="inline">broadcast</code> becomes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="6121385212-1">(</span><span class="nf">fun</span><span class="p" data-group-id="6121385212-2">(</span><span class="n">Pid</span><span class="p" data-group-id="6121385212-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="6121385212-1">)</span></code></pre><p><code class="inline">foreach</code> is evaluated for its side-effect and not its value. <code class="inline">foreach(Fun, L)</code>
│ │ │ │ +extra argument to the function that does this.</p><p>The function <code class="inline">foreach</code> expresses this similarity:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="8324892733-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8324892733-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8324892733-2">]</span><span class="p" data-group-id="8324892733-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">F</span><span class="p" data-group-id="8324892733-3">(</span><span class="n">H</span><span class="p" data-group-id="8324892733-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="8324892733-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="8324892733-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">foreach</span><span class="p" data-group-id="8324892733-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8324892733-6">[</span><span class="p" data-group-id="8324892733-6">]</span><span class="p" data-group-id="8324892733-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>Using the function <code class="inline">foreach</code>, the function <code class="inline">print_list</code> becomes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="8895918696-1">(</span><span class="nf">fun</span><span class="p" data-group-id="8895918696-2">(</span><span class="n">H</span><span class="p" data-group-id="8895918696-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8895918696-3">(</span><span class="n">S</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="8895918696-4">[</span><span class="n">H</span><span class="p" data-group-id="8895918696-4">]</span><span class="p" data-group-id="8895918696-3">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="8895918696-1">)</span></code></pre><p>Using the function <code class="inline">foreach</code>, the function <code class="inline">broadcast</code> becomes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="7738888640-1">(</span><span class="nf">fun</span><span class="p" data-group-id="7738888640-2">(</span><span class="n">Pid</span><span class="p" data-group-id="7738888640-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="7738888640-1">)</span></code></pre><p><code class="inline">foreach</code> is evaluated for its side-effect and not its value. <code class="inline">foreach(Fun, L)</code>
│ │ │ │  calls <code class="inline">Fun(X)</code> for each element <code class="inline">X</code> in <code class="inline">L</code> and the processing occurs in the
│ │ │ │  order that the elements were defined in <code class="inline">L</code>. <code class="inline">map</code> does not define the order in
│ │ │ │  which its elements are processed.</p><h2 id="syntax-of-funs" class="section-heading">
│ │ │ │    <a href="#syntax-of-funs" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Syntax of Funs</span>
│ │ │ │  </h2>
│ │ │ │  <p>Funs are written with the following syntax (see
│ │ │ │ -<a href="../../../lib/../system/doc/html/expressions.xhtml#fun-expressions">Fun Expressions</a> for full description):</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8790760210-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="w"> </span><span class="n">Arg2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">ArgN</span><span class="p" data-group-id="8790760210-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +<a href="../../../lib/../system/doc/html/expressions.xhtml#fun-expressions">Fun Expressions</a> for full description):</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="3586909633-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="w"> </span><span class="n">Arg2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">ArgN</span><span class="p" data-group-id="3586909633-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │      </span><span class="k">end</span></code></pre><p>This creates an anonymous function of <code class="inline">N</code> arguments and binds it to the variable
│ │ │ │  <code class="inline">F</code>.</p><p>Another function, <code class="inline">FunctionName</code>, written in the same module, can be passed as
│ │ │ │  an argument, using the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">FunctionName</span><span class="o">/</span><span class="n">Arity</span></code></pre><p>With this form of function reference, the function that is referred to does not
│ │ │ │  need to be exported from the module.</p><p>It is also possible to refer to a function defined in a different module, with
│ │ │ │ -the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">Module</span><span class="p">:</span><span class="n">FunctionName</span><span class="o">/</span><span class="n">Arity</span></code></pre><p>In this case, the function must be exported from the module in question.</p><p>The following program illustrates the different ways of creating funs:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4333592614-1">(</span><span class="ss">fun_test</span><span class="p" data-group-id="4333592614-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4333592614-2">(</span><span class="p" data-group-id="4333592614-3">[</span><span class="ss">t1</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">t2</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4333592614-3">]</span><span class="p" data-group-id="4333592614-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">import</span><span class="p" data-group-id="4333592614-4">(</span><span class="ss">lists</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4333592614-5">[</span><span class="ss">map</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4333592614-5">]</span><span class="p" data-group-id="4333592614-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">Module</span><span class="p">:</span><span class="n">FunctionName</span><span class="o">/</span><span class="n">Arity</span></code></pre><p>In this case, the function must be exported from the module in question.</p><p>The following program illustrates the different ways of creating funs:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0319047185-1">(</span><span class="ss">fun_test</span><span class="p" data-group-id="0319047185-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0319047185-2">(</span><span class="p" data-group-id="0319047185-3">[</span><span class="ss">t1</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">t2</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0319047185-3">]</span><span class="p" data-group-id="0319047185-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">import</span><span class="p" data-group-id="0319047185-4">(</span><span class="ss">lists</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0319047185-5">[</span><span class="ss">map</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0319047185-5">]</span><span class="p" data-group-id="0319047185-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">t1</span><span class="p" data-group-id="4333592614-6">(</span><span class="p" data-group-id="4333592614-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="4333592614-7">(</span><span class="nf">fun</span><span class="p" data-group-id="4333592614-8">(</span><span class="n">X</span><span class="p" data-group-id="4333592614-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4333592614-9">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="4333592614-9">]</span><span class="p" data-group-id="4333592614-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">t1</span><span class="p" data-group-id="0319047185-6">(</span><span class="p" data-group-id="0319047185-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="0319047185-7">(</span><span class="nf">fun</span><span class="p" data-group-id="0319047185-8">(</span><span class="n">X</span><span class="p" data-group-id="0319047185-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0319047185-9">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0319047185-9">]</span><span class="p" data-group-id="0319047185-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">t2</span><span class="p" data-group-id="4333592614-10">(</span><span class="p" data-group-id="4333592614-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="4333592614-11">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4333592614-12">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="4333592614-12">]</span><span class="p" data-group-id="4333592614-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">t2</span><span class="p" data-group-id="0319047185-10">(</span><span class="p" data-group-id="0319047185-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="0319047185-11">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0319047185-12">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0319047185-12">]</span><span class="p" data-group-id="0319047185-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">double</span><span class="p" data-group-id="4333592614-13">(</span><span class="n">X</span><span class="p" data-group-id="4333592614-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">2</span><span class="p">.</span></code></pre><p>The fun <code class="inline">F</code> can be evaluated with the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="p" data-group-id="8822641762-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="w"> </span><span class="n">Arg2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Argn</span><span class="p" data-group-id="8822641762-1">)</span></code></pre><p>To check whether a term is a fun, use the test
│ │ │ │ -<a href="../../../lib/../erts/doc/html/erlang.html#is_function/1"><code class="inline">is_function/1</code></a> in a guard.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="6360971790-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="6360971790-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_function</span><span class="p" data-group-id="6360971790-2">(</span><span class="n">F</span><span class="p" data-group-id="6360971790-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="nf">apply</span><span class="p" data-group-id="6360971790-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="6360971790-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="6360971790-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="6360971790-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="6360971790-5">(</span><span class="n">N</span><span class="p" data-group-id="6360971790-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">double</span><span class="p" data-group-id="0319047185-13">(</span><span class="n">X</span><span class="p" data-group-id="0319047185-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">2</span><span class="p">.</span></code></pre><p>The fun <code class="inline">F</code> can be evaluated with the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="p" data-group-id="3778873046-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="w"> </span><span class="n">Arg2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Argn</span><span class="p" data-group-id="3778873046-1">)</span></code></pre><p>To check whether a term is a fun, use the test
│ │ │ │ +<a href="../../../lib/../erts/doc/html/erlang.html#is_function/1"><code class="inline">is_function/1</code></a> in a guard.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="7624644776-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="7624644776-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_function</span><span class="p" data-group-id="7624644776-2">(</span><span class="n">F</span><span class="p" data-group-id="7624644776-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="nf">apply</span><span class="p" data-group-id="7624644776-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="7624644776-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="7624644776-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7624644776-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="7624644776-5">(</span><span class="n">N</span><span class="p" data-group-id="7624644776-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │     </span><span class="n">N</span><span class="p">.</span></code></pre><p>Funs are a distinct type. The BIFs <code class="inline">erlang:fun_info/1,2</code> can be used to retrieve
│ │ │ │  information about a fun, and the BIF <a href="../../../lib/../erts/doc/html/erlang.html#fun_to_list/1"><code class="inline">erlang:fun_to_list/1</code></a> returns a textual
│ │ │ │  representation of a fun. The <a href="../../../lib/../erts/doc/html/erlang.html#check_process_code/2"><code class="inline">check_process_code/2</code></a>
│ │ │ │  BIF returns <code class="inline">true</code> if the process contains funs that depend on the old version
│ │ │ │  of a module.</p><h2 id="variable-bindings-within-a-fun" class="section-heading">
│ │ │ │    <a href="#variable-bindings-within-a-fun" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Variable Bindings Within a Fun</span>
│ │ │ │  </h2>
│ │ │ │  <p>The scope rules for variables that occur in funs are as follows:</p><ul><li>All variables that occur in the head of a fun are assumed to be &quot;fresh&quot;
│ │ │ │  variables.</li><li>Variables that are defined before the fun, and that occur in function calls or
│ │ │ │ -guard tests within the fun, have the values they had outside the fun.</li><li>Variables cannot be exported from a fun.</li></ul><p>The following examples illustrate these rules:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="9271445966-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9271445966-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9271445966-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Stream</span><span class="p" data-group-id="9271445966-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="9271445966-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">write</span><span class="p" data-group-id="9271445966-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="9271445966-4">(</span><span class="nf">fun</span><span class="p" data-group-id="9271445966-5">(</span><span class="n">X</span><span class="p" data-group-id="9271445966-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9271445966-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="9271445966-7">[</span><span class="n">X</span><span class="p" data-group-id="9271445966-7">]</span><span class="p" data-group-id="9271445966-6">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9271445966-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="9271445966-8">(</span><span class="n">Stream</span><span class="p" data-group-id="9271445966-8">)</span><span class="p">.</span></code></pre><p>Here, the variable <code class="inline">X</code>, defined in the head of the fun, is a new variable. The
│ │ │ │ +guard tests within the fun, have the values they had outside the fun.</li><li>Variables cannot be exported from a fun.</li></ul><p>The following examples illustrate these rules:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="9562381358-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9562381358-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9562381358-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Stream</span><span class="p" data-group-id="9562381358-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="9562381358-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">write</span><span class="p" data-group-id="9562381358-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="9562381358-4">(</span><span class="nf">fun</span><span class="p" data-group-id="9562381358-5">(</span><span class="n">X</span><span class="p" data-group-id="9562381358-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9562381358-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="9562381358-7">[</span><span class="n">X</span><span class="p" data-group-id="9562381358-7">]</span><span class="p" data-group-id="9562381358-6">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9562381358-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="9562381358-8">(</span><span class="n">Stream</span><span class="p" data-group-id="9562381358-8">)</span><span class="p">.</span></code></pre><p>Here, the variable <code class="inline">X</code>, defined in the head of the fun, is a new variable. The
│ │ │ │  variable <code class="inline">Stream</code>, which is used within the fun, gets its value from the
│ │ │ │  <code class="inline">file:open</code> line.</p><p>As any variable that occurs in the head of a fun is considered a new variable,
│ │ │ │ -it is equally valid to write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="7088631053-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7088631053-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7088631053-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Stream</span><span class="p" data-group-id="7088631053-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="7088631053-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">write</span><span class="p" data-group-id="7088631053-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="7088631053-4">(</span><span class="nf">fun</span><span class="p" data-group-id="7088631053-5">(</span><span class="n">File</span><span class="p" data-group-id="7088631053-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7088631053-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="7088631053-7">[</span><span class="n">File</span><span class="p" data-group-id="7088631053-7">]</span><span class="p" data-group-id="7088631053-6">)</span><span class="w">
│ │ │ │ -            </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7088631053-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="7088631053-8">(</span><span class="n">Stream</span><span class="p" data-group-id="7088631053-8">)</span><span class="p">.</span></code></pre><p>Here, <code class="inline">File</code> is used as the new variable instead of <code class="inline">X</code>. This is not so wise
│ │ │ │ +it is equally valid to write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="7216412169-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7216412169-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7216412169-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Stream</span><span class="p" data-group-id="7216412169-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="7216412169-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">write</span><span class="p" data-group-id="7216412169-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="7216412169-4">(</span><span class="nf">fun</span><span class="p" data-group-id="7216412169-5">(</span><span class="n">File</span><span class="p" data-group-id="7216412169-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7216412169-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="7216412169-7">[</span><span class="n">File</span><span class="p" data-group-id="7216412169-7">]</span><span class="p" data-group-id="7216412169-6">)</span><span class="w">
│ │ │ │ +            </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7216412169-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="7216412169-8">(</span><span class="n">Stream</span><span class="p" data-group-id="7216412169-8">)</span><span class="p">.</span></code></pre><p>Here, <code class="inline">File</code> is used as the new variable instead of <code class="inline">X</code>. This is not so wise
│ │ │ │  because code in the fun body cannot refer to the variable <code class="inline">File</code>, which is
│ │ │ │  defined outside of the fun. Compiling this example gives the following
│ │ │ │  diagnostic:</p><pre><code class="text">./FileName.erl:Line: Warning: variable 'File'
│ │ │ │        shadowed in 'fun'</code></pre><p>This indicates that the variable <code class="inline">File</code>, which is defined inside the fun,
│ │ │ │  collides with the variable <code class="inline">File</code>, which is defined outside the fun.</p><p>The rules for importing variables into a fun have the consequence that certain
│ │ │ │  pattern matching operations must be moved into guard expressions and cannot be
│ │ │ │  written in the head of the fun. For example, you might write the following code
│ │ │ │  if you intend the first clause of <code class="inline">F</code> to be evaluated when the value of its
│ │ │ │ -argument is <code class="inline">Y</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="3910600642-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3910600642-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +argument is <code class="inline">Y</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="6957866805-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6957866805-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="nf">map</span><span class="p" data-group-id="3910600642-2">(</span><span class="nf">fun</span><span class="p" data-group-id="3910600642-3">(</span><span class="n">X</span><span class="p" data-group-id="3910600642-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">map</span><span class="p" data-group-id="6957866805-2">(</span><span class="nf">fun</span><span class="p" data-group-id="6957866805-3">(</span><span class="n">X</span><span class="p" data-group-id="6957866805-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │               </span><span class="p">;</span><span class="w">
│ │ │ │ -           </span><span class="p" data-group-id="3910600642-4">(</span><span class="p">_</span><span class="p" data-group-id="3910600642-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +           </span><span class="p" data-group-id="6957866805-4">(</span><span class="p">_</span><span class="p" data-group-id="6957866805-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │               </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -        </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3910600642-2">)</span><span class="w">
│ │ │ │ -    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>instead of writing the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="2720997201-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2720997201-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6957866805-2">)</span><span class="w">
│ │ │ │ +    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>instead of writing the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="0753616205-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0753616205-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="nf">map</span><span class="p" data-group-id="2720997201-2">(</span><span class="nf">fun</span><span class="p" data-group-id="2720997201-3">(</span><span class="n">Y</span><span class="p" data-group-id="2720997201-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">map</span><span class="p" data-group-id="0753616205-2">(</span><span class="nf">fun</span><span class="p" data-group-id="0753616205-3">(</span><span class="n">Y</span><span class="p" data-group-id="0753616205-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │               </span><span class="p">;</span><span class="w">
│ │ │ │ -           </span><span class="p" data-group-id="2720997201-4">(</span><span class="p">_</span><span class="p" data-group-id="2720997201-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +           </span><span class="p" data-group-id="0753616205-4">(</span><span class="p">_</span><span class="p" data-group-id="0753616205-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │               </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -        </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2720997201-2">)</span><span class="w">
│ │ │ │ +        </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0753616205-2">)</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="funs-and-module-lists" class="section-heading">
│ │ │ │    <a href="#funs-and-module-lists" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Funs and Module Lists</span>
│ │ │ │  </h2>
│ │ │ │  <p>The following examples show a dialogue with the Erlang shell. All the higher
│ │ │ │  order functions discussed are exported from the module <a href="../../../lib/stdlib/doc/html/lists.html"><code class="inline">lists</code></a>.</p><h3 id="map-1" class="section-heading">
│ │ │ │    <a href="#map-1" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">map</span>
│ │ │ │  </h3>
│ │ │ │ -<p><a href="../../../lib/stdlib/doc/html/lists.html#map/2"><code class="inline">lists:map/2</code></a> takes a function of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">map</span><span class="p" data-group-id="0007112096-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0007112096-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0007112096-2">]</span><span class="p" data-group-id="0007112096-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0007112096-3">[</span><span class="n">F</span><span class="p" data-group-id="0007112096-4">(</span><span class="n">H</span><span class="p" data-group-id="0007112096-4">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="0007112096-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="0007112096-5">)</span><span class="p" data-group-id="0007112096-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="0007112096-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0007112096-7">[</span><span class="p" data-group-id="0007112096-7">]</span><span class="p" data-group-id="0007112096-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0007112096-8">[</span><span class="p" data-group-id="0007112096-8">]</span><span class="p">.</span></code></pre><p>It returns the list obtained by applying the function to every argument in the
│ │ │ │ +<p><a href="../../../lib/stdlib/doc/html/lists.html#map/2"><code class="inline">lists:map/2</code></a> takes a function of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">map</span><span class="p" data-group-id="6407977031-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6407977031-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6407977031-2">]</span><span class="p" data-group-id="6407977031-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6407977031-3">[</span><span class="n">F</span><span class="p" data-group-id="6407977031-4">(</span><span class="n">H</span><span class="p" data-group-id="6407977031-4">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="6407977031-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="6407977031-5">)</span><span class="p" data-group-id="6407977031-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="6407977031-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6407977031-7">[</span><span class="p" data-group-id="6407977031-7">]</span><span class="p" data-group-id="6407977031-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6407977031-8">[</span><span class="p" data-group-id="6407977031-8">]</span><span class="p">.</span></code></pre><p>It returns the list obtained by applying the function to every argument in the
│ │ │ │  list.</p><p>When a new fun is defined in the shell, the value of the fun is printed as
│ │ │ │ -<code class="inline">Fun#&lt;erl_eval&gt;</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Double</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="1888739668-1">(</span><span class="n">X</span><span class="p" data-group-id="1888739668-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">Fun#&lt;erl_eval&gt;</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Double</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0948299395-1">(</span><span class="n">X</span><span class="p" data-group-id="0948299395-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="1888739668-2">(</span><span class="n">Double</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1888739668-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="1888739668-3">]</span><span class="p" data-group-id="1888739668-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1888739668-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="1888739668-4">]</span></code></pre><h3 id="any" class="section-heading">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="0948299395-2">(</span><span class="n">Double</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0948299395-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0948299395-3">]</span><span class="p" data-group-id="0948299395-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0948299395-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="0948299395-4">]</span></code></pre><h3 id="any" class="section-heading">
│ │ │ │    <a href="#any" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">any</span>
│ │ │ │  </h3>
│ │ │ │ -<p><a href="../../../lib/stdlib/doc/html/lists.html#any/2"><code class="inline">lists:any/2</code></a> takes a predicate <code class="inline">P</code> of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">any</span><span class="p" data-group-id="9217618536-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9217618536-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9217618536-2">]</span><span class="p" data-group-id="9217618536-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="9217618536-3">(</span><span class="n">H</span><span class="p" data-group-id="9217618536-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +<p><a href="../../../lib/stdlib/doc/html/lists.html#any/2"><code class="inline">lists:any/2</code></a> takes a predicate <code class="inline">P</code> of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">any</span><span class="p" data-group-id="6741198829-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6741198829-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6741198829-2">]</span><span class="p" data-group-id="6741198829-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="6741198829-3">(</span><span class="n">H</span><span class="p" data-group-id="6741198829-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">  </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="nf">any</span><span class="p" data-group-id="9217618536-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="9217618536-4">)</span><span class="w">
│ │ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="nf">any</span><span class="p" data-group-id="6741198829-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="6741198829-4">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">any</span><span class="p" data-group-id="9217618536-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9217618536-6">[</span><span class="p" data-group-id="9217618536-6">]</span><span class="p" data-group-id="9217618536-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">any</span><span class="p" data-group-id="6741198829-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6741198829-6">[</span><span class="p" data-group-id="6741198829-6">]</span><span class="p" data-group-id="6741198829-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">false</span><span class="p">.</span></code></pre><p>A predicate is a function that returns <code class="inline">true</code> or <code class="inline">false</code>. <code class="inline">any</code> is <code class="inline">true</code> if
│ │ │ │  there is a term <code class="inline">X</code> in the list such that <code class="inline">P(X)</code> is <code class="inline">true</code>.</p><p>A predicate <code class="inline">Big(X)</code> is defined, which is <code class="inline">true</code> if its argument is greater than
│ │ │ │ -10:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Big</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="nf">fun</span><span class="p" data-group-id="3512604645-1">(</span><span class="n">X</span><span class="p" data-group-id="3512604645-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">10</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">true</span><span class="p">;</span><span class="w"> </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">false</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +10:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Big</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="nf">fun</span><span class="p" data-group-id="4776572397-1">(</span><span class="n">X</span><span class="p" data-group-id="4776572397-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">10</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">true</span><span class="p">;</span><span class="w"> </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">false</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">any</span><span class="p" data-group-id="3512604645-2">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3512604645-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3512604645-3">]</span><span class="p" data-group-id="3512604645-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">any</span><span class="p" data-group-id="4776572397-2">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4776572397-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4776572397-3">]</span><span class="p" data-group-id="4776572397-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">any</span><span class="p" data-group-id="3512604645-4">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3512604645-5">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="3512604645-5">]</span><span class="p" data-group-id="3512604645-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">any</span><span class="p" data-group-id="4776572397-4">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4776572397-5">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="4776572397-5">]</span><span class="p" data-group-id="4776572397-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span></code></pre><h3 id="all" class="section-heading">
│ │ │ │    <a href="#all" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">all</span>
│ │ │ │  </h3>
│ │ │ │ -<p><a href="../../../lib/stdlib/doc/html/lists.html#all/2"><code class="inline">lists:all/2</code></a> has the same arguments as <code class="inline">any</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">all</span><span class="p" data-group-id="5960391457-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5960391457-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5960391457-2">]</span><span class="p" data-group-id="5960391457-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="5960391457-3">(</span><span class="n">H</span><span class="p" data-group-id="5960391457-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">  </span><span class="nf">all</span><span class="p" data-group-id="5960391457-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="5960391457-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +<p><a href="../../../lib/stdlib/doc/html/lists.html#all/2"><code class="inline">lists:all/2</code></a> has the same arguments as <code class="inline">any</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">all</span><span class="p" data-group-id="6803312728-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6803312728-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6803312728-2">]</span><span class="p" data-group-id="6803312728-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="6803312728-3">(</span><span class="n">H</span><span class="p" data-group-id="6803312728-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">  </span><span class="nf">all</span><span class="p" data-group-id="6803312728-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="6803312728-4">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="ss">false</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">all</span><span class="p" data-group-id="5960391457-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5960391457-6">[</span><span class="p" data-group-id="5960391457-6">]</span><span class="p" data-group-id="5960391457-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">true</span><span class="p">.</span></code></pre><p>It is <code class="inline">true</code> if the predicate applied to all elements in the list is <code class="inline">true</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">all</span><span class="p" data-group-id="8333819437-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8333819437-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8333819437-2">]</span><span class="p" data-group-id="8333819437-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">all</span><span class="p" data-group-id="6803312728-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6803312728-6">[</span><span class="p" data-group-id="6803312728-6">]</span><span class="p" data-group-id="6803312728-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">true</span><span class="p">.</span></code></pre><p>It is <code class="inline">true</code> if the predicate applied to all elements in the list is <code class="inline">true</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">all</span><span class="p" data-group-id="5625737992-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5625737992-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="5625737992-2">]</span><span class="p" data-group-id="5625737992-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">all</span><span class="p" data-group-id="8333819437-3">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8333819437-4">[</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p">,</span><span class="mi">14</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="8333819437-4">]</span><span class="p" data-group-id="8333819437-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">all</span><span class="p" data-group-id="5625737992-3">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5625737992-4">[</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p">,</span><span class="mi">14</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="5625737992-4">]</span><span class="p" data-group-id="5625737992-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span></code></pre><h3 id="foreach-1" class="section-heading">
│ │ │ │    <a href="#foreach-1" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">foreach</span>
│ │ │ │  </h3>
│ │ │ │ -<p><a href="../../../lib/stdlib/doc/html/lists.html#foreach/2"><code class="inline">lists:foreach/2</code></a> takes a function of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="3105158043-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3105158043-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3105158043-2">]</span><span class="p" data-group-id="3105158043-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">F</span><span class="p" data-group-id="3105158043-3">(</span><span class="n">H</span><span class="p" data-group-id="3105158043-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="3105158043-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="3105158043-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">foreach</span><span class="p" data-group-id="3105158043-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3105158043-6">[</span><span class="p" data-group-id="3105158043-6">]</span><span class="p" data-group-id="3105158043-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +<p><a href="../../../lib/stdlib/doc/html/lists.html#foreach/2"><code class="inline">lists:foreach/2</code></a> takes a function of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="0554502230-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0554502230-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0554502230-2">]</span><span class="p" data-group-id="0554502230-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">F</span><span class="p" data-group-id="0554502230-3">(</span><span class="n">H</span><span class="p" data-group-id="0554502230-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="0554502230-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="0554502230-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">foreach</span><span class="p" data-group-id="0554502230-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0554502230-6">[</span><span class="p" data-group-id="0554502230-6">]</span><span class="p" data-group-id="0554502230-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The function is applied to each argument in the list. <code class="inline">foreach</code> returns <code class="inline">ok</code>. It
│ │ │ │ -is only used for its side-effect:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="2781616013-1">(</span><span class="nf">fun</span><span class="p" data-group-id="2781616013-2">(</span><span class="n">X</span><span class="p" data-group-id="2781616013-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2781616013-3">(</span><span class="s">&quot;</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="2781616013-4">[</span><span class="n">X</span><span class="p" data-group-id="2781616013-4">]</span><span class="p" data-group-id="2781616013-3">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2781616013-5">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="2781616013-5">]</span><span class="p" data-group-id="2781616013-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +is only used for its side-effect:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="6364737661-1">(</span><span class="nf">fun</span><span class="p" data-group-id="6364737661-2">(</span><span class="n">X</span><span class="p" data-group-id="6364737661-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6364737661-3">(</span><span class="s">&quot;</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="6364737661-4">[</span><span class="n">X</span><span class="p" data-group-id="6364737661-4">]</span><span class="p" data-group-id="6364737661-3">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6364737661-5">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6364737661-5">]</span><span class="p" data-group-id="6364737661-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">1</span><span class="w">
│ │ │ │  </span><span class="mi">2</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ │  </span><span class="mi">4</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><h3 id="foldl" class="section-heading">
│ │ │ │    <a href="#foldl" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">foldl</span>
│ │ │ │  </h3>
│ │ │ │ -<p><a href="../../../lib/stdlib/doc/html/lists.html#foldl/3"><code class="inline">lists:foldl/3</code></a> takes a function of two arguments, an accumulator and a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foldl</span><span class="p" data-group-id="2627211295-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2627211295-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="2627211295-2">]</span><span class="p" data-group-id="2627211295-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">foldl</span><span class="p" data-group-id="2627211295-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="2627211295-4">(</span><span class="n">Hd</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p" data-group-id="2627211295-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="2627211295-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">foldl</span><span class="p" data-group-id="2627211295-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2627211295-6">[</span><span class="p" data-group-id="2627211295-6">]</span><span class="p" data-group-id="2627211295-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Accu</span><span class="p">.</span></code></pre><p>The function is called with two arguments. The first argument is the successive
│ │ │ │ +<p><a href="../../../lib/stdlib/doc/html/lists.html#foldl/3"><code class="inline">lists:foldl/3</code></a> takes a function of two arguments, an accumulator and a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foldl</span><span class="p" data-group-id="6704463082-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6704463082-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="6704463082-2">]</span><span class="p" data-group-id="6704463082-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">foldl</span><span class="p" data-group-id="6704463082-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="6704463082-4">(</span><span class="n">Hd</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p" data-group-id="6704463082-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="6704463082-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">foldl</span><span class="p" data-group-id="6704463082-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6704463082-6">[</span><span class="p" data-group-id="6704463082-6">]</span><span class="p" data-group-id="6704463082-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Accu</span><span class="p">.</span></code></pre><p>The function is called with two arguments. The first argument is the successive
│ │ │ │  elements in the list. The second argument is the accumulator. The function must
│ │ │ │  return a new accumulator, which is used the next time the function is called.</p><p>If you have a list of lists <code class="inline">L = [&quot;I&quot;,&quot;like&quot;,&quot;Erlang&quot;]</code>, then you can sum the
│ │ │ │ -lengths of all the strings in <code class="inline">L</code> as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7545445432-1">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="7545445432-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7545445432-2">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="7545445432-2">]</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">10&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="7545445432-3">(</span><span class="nf">fun</span><span class="p" data-group-id="7545445432-4">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="7545445432-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="7545445432-5">(</span><span class="n">X</span><span class="p" data-group-id="7545445432-5">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="7545445432-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="mi">11</span></code></pre><p><a href="../../../lib/stdlib/doc/html/lists.html#foldl/3"><code class="inline">lists:foldl/3</code></a> works like a <code class="inline">while</code> loop in an imperative language:</p><pre><code class="makeup erlang" translate="no"><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="p" data-group-id="1222612899-1">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="1222612899-1">]</span><span class="p">,</span><span class="w">
│ │ │ │ +lengths of all the strings in <code class="inline">L</code> as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5363185648-1">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="5363185648-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5363185648-2">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="5363185648-2">]</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">10&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="5363185648-3">(</span><span class="nf">fun</span><span class="p" data-group-id="5363185648-4">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="5363185648-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="5363185648-5">(</span><span class="n">X</span><span class="p" data-group-id="5363185648-5">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="5363185648-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="mi">11</span></code></pre><p><a href="../../../lib/stdlib/doc/html/lists.html#foldl/3"><code class="inline">lists:foldl/3</code></a> works like a <code class="inline">while</code> loop in an imperative language:</p><pre><code class="makeup erlang" translate="no"><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="p" data-group-id="6985221127-1">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="6985221127-1">]</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="n">Sum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nf">while</span><span class="p" data-group-id="1222612899-2">(</span><span class="w"> </span><span class="n">L</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1222612899-3">[</span><span class="p" data-group-id="1222612899-3">]</span><span class="p" data-group-id="1222612899-2">)</span><span class="p" data-group-id="1222612899-4">{</span><span class="w">
│ │ │ │ -    </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="1222612899-5">(</span><span class="nf">head</span><span class="p" data-group-id="1222612899-6">(</span><span class="n">L</span><span class="p" data-group-id="1222612899-6">)</span><span class="p" data-group-id="1222612899-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">tail</span><span class="p" data-group-id="1222612899-7">(</span><span class="n">L</span><span class="p" data-group-id="1222612899-7">)</span><span class="w">
│ │ │ │ +</span><span class="nf">while</span><span class="p" data-group-id="6985221127-2">(</span><span class="w"> </span><span class="n">L</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6985221127-3">[</span><span class="p" data-group-id="6985221127-3">]</span><span class="p" data-group-id="6985221127-2">)</span><span class="p" data-group-id="6985221127-4">{</span><span class="w">
│ │ │ │ +    </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="6985221127-5">(</span><span class="nf">head</span><span class="p" data-group-id="6985221127-6">(</span><span class="n">L</span><span class="p" data-group-id="6985221127-6">)</span><span class="p" data-group-id="6985221127-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">tail</span><span class="p" data-group-id="6985221127-7">(</span><span class="n">L</span><span class="p" data-group-id="6985221127-7">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><h3 id="mapfoldl" class="section-heading">
│ │ │ │    <a href="#mapfoldl" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">mapfoldl</span>
│ │ │ │  </h3>
│ │ │ │ -<p><a href="../../../lib/stdlib/doc/html/lists.html#mapfoldl/3"><code class="inline">lists:mapfoldl/3</code></a> simultaneously maps and folds over a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">mapfoldl</span><span class="p" data-group-id="2786564563-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu0</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2786564563-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="2786564563-2">]</span><span class="p" data-group-id="2786564563-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2786564563-3">{</span><span class="n">R</span><span class="p">,</span><span class="n">Accu1</span><span class="p" data-group-id="2786564563-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="2786564563-4">(</span><span class="n">Hd</span><span class="p">,</span><span class="w"> </span><span class="n">Accu0</span><span class="p" data-group-id="2786564563-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2786564563-5">{</span><span class="n">Rs</span><span class="p">,</span><span class="n">Accu2</span><span class="p" data-group-id="2786564563-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">mapfoldl</span><span class="p" data-group-id="2786564563-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu1</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="2786564563-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2786564563-7">{</span><span class="p" data-group-id="2786564563-8">[</span><span class="n">R</span><span class="p">|</span><span class="n">Rs</span><span class="p" data-group-id="2786564563-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Accu2</span><span class="p" data-group-id="2786564563-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">mapfoldl</span><span class="p" data-group-id="2786564563-9">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2786564563-10">[</span><span class="p" data-group-id="2786564563-10">]</span><span class="p" data-group-id="2786564563-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2786564563-11">{</span><span class="p" data-group-id="2786564563-12">[</span><span class="p" data-group-id="2786564563-12">]</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p" data-group-id="2786564563-11">}</span><span class="p">.</span></code></pre><p>The following example shows how to change all letters in <code class="inline">L</code> to upper case and
│ │ │ │ -then count them.</p><p>First the change to upper case:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Upcase</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="nf">fun</span><span class="p" data-group-id="3450241565-1">(</span><span class="n">X</span><span class="p" data-group-id="3450241565-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$a</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w">  </span><span class="n">X</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">$A</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="sc">$a</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3450241565-2">(</span><span class="n">X</span><span class="p" data-group-id="3450241565-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w">
│ │ │ │ +<p><a href="../../../lib/stdlib/doc/html/lists.html#mapfoldl/3"><code class="inline">lists:mapfoldl/3</code></a> simultaneously maps and folds over a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">mapfoldl</span><span class="p" data-group-id="8097346900-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu0</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8097346900-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="8097346900-2">]</span><span class="p" data-group-id="8097346900-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8097346900-3">{</span><span class="n">R</span><span class="p">,</span><span class="n">Accu1</span><span class="p" data-group-id="8097346900-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="8097346900-4">(</span><span class="n">Hd</span><span class="p">,</span><span class="w"> </span><span class="n">Accu0</span><span class="p" data-group-id="8097346900-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8097346900-5">{</span><span class="n">Rs</span><span class="p">,</span><span class="n">Accu2</span><span class="p" data-group-id="8097346900-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">mapfoldl</span><span class="p" data-group-id="8097346900-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu1</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="8097346900-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8097346900-7">{</span><span class="p" data-group-id="8097346900-8">[</span><span class="n">R</span><span class="p">|</span><span class="n">Rs</span><span class="p" data-group-id="8097346900-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Accu2</span><span class="p" data-group-id="8097346900-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">mapfoldl</span><span class="p" data-group-id="8097346900-9">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8097346900-10">[</span><span class="p" data-group-id="8097346900-10">]</span><span class="p" data-group-id="8097346900-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8097346900-11">{</span><span class="p" data-group-id="8097346900-12">[</span><span class="p" data-group-id="8097346900-12">]</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p" data-group-id="8097346900-11">}</span><span class="p">.</span></code></pre><p>The following example shows how to change all letters in <code class="inline">L</code> to upper case and
│ │ │ │ +then count them.</p><p>First the change to upper case:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Upcase</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="nf">fun</span><span class="p" data-group-id="1324972587-1">(</span><span class="n">X</span><span class="p" data-group-id="1324972587-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$a</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w">  </span><span class="n">X</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">$A</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="sc">$a</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1324972587-2">(</span><span class="n">X</span><span class="p" data-group-id="1324972587-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">&gt; </span><span class="n">Upcase_word</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │ -</span><span class="nf">fun</span><span class="p" data-group-id="3450241565-3">(</span><span class="n">X</span><span class="p" data-group-id="3450241565-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="3450241565-4">(</span><span class="n">Upcase</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="3450241565-4">)</span><span class="w">
│ │ │ │ +</span><span class="nf">fun</span><span class="p" data-group-id="1324972587-3">(</span><span class="n">X</span><span class="p" data-group-id="1324972587-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="1324972587-4">(</span><span class="n">Upcase</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1324972587-4">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">Upcase_word</span><span class="p" data-group-id="3450241565-5">(</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="3450241565-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">Upcase_word</span><span class="p" data-group-id="1324972587-5">(</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="1324972587-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;ERLANG&quot;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="3450241565-6">(</span><span class="n">Upcase_word</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="3450241565-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3450241565-7">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;LIKE&quot;</span><span class="p">,</span><span class="s">&quot;ERLANG&quot;</span><span class="p" data-group-id="3450241565-7">]</span></code></pre><p>Now, the fold and the map can be done at the same time:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">mapfoldl</span><span class="p" data-group-id="4275657967-1">(</span><span class="nf">fun</span><span class="p" data-group-id="4275657967-2">(</span><span class="n">Word</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="4275657967-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4275657967-3">{</span><span class="n">Upcase_word</span><span class="p" data-group-id="4275657967-4">(</span><span class="n">Word</span><span class="p" data-group-id="4275657967-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="4275657967-5">(</span><span class="n">Word</span><span class="p" data-group-id="4275657967-5">)</span><span class="p" data-group-id="4275657967-3">}</span><span class="w">
│ │ │ │ -</span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4275657967-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4275657967-6">{</span><span class="p" data-group-id="4275657967-7">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;LIKE&quot;</span><span class="p">,</span><span class="s">&quot;ERLANG&quot;</span><span class="p" data-group-id="4275657967-7">]</span><span class="p">,</span><span class="mi">11</span><span class="p" data-group-id="4275657967-6">}</span></code></pre><h3 id="filter" class="section-heading">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="1324972587-6">(</span><span class="n">Upcase_word</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="1324972587-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1324972587-7">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;LIKE&quot;</span><span class="p">,</span><span class="s">&quot;ERLANG&quot;</span><span class="p" data-group-id="1324972587-7">]</span></code></pre><p>Now, the fold and the map can be done at the same time:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">mapfoldl</span><span class="p" data-group-id="5376317797-1">(</span><span class="nf">fun</span><span class="p" data-group-id="5376317797-2">(</span><span class="n">Word</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="5376317797-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5376317797-3">{</span><span class="n">Upcase_word</span><span class="p" data-group-id="5376317797-4">(</span><span class="n">Word</span><span class="p" data-group-id="5376317797-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="5376317797-5">(</span><span class="n">Word</span><span class="p" data-group-id="5376317797-5">)</span><span class="p" data-group-id="5376317797-3">}</span><span class="w">
│ │ │ │ +</span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="5376317797-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5376317797-6">{</span><span class="p" data-group-id="5376317797-7">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;LIKE&quot;</span><span class="p">,</span><span class="s">&quot;ERLANG&quot;</span><span class="p" data-group-id="5376317797-7">]</span><span class="p">,</span><span class="mi">11</span><span class="p" data-group-id="5376317797-6">}</span></code></pre><h3 id="filter" class="section-heading">
│ │ │ │    <a href="#filter" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">filter</span>
│ │ │ │  </h3>
│ │ │ │  <p><a href="../../../lib/stdlib/doc/html/lists.html#filter/2"><code class="inline">lists:filter/2</code></a> takes a predicate of one argument and a list and returns all elements
│ │ │ │ -in the list that satisfy the predicate:</p><pre><code class="makeup erlang" translate="no"><span class="nf">filter</span><span class="p" data-group-id="1175483496-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1175483496-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1175483496-2">]</span><span class="p" data-group-id="1175483496-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="1175483496-3">(</span><span class="n">H</span><span class="p" data-group-id="1175483496-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1175483496-4">[</span><span class="n">H</span><span class="p">|</span><span class="nf">filter</span><span class="p" data-group-id="1175483496-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="1175483496-5">)</span><span class="p" data-group-id="1175483496-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">filter</span><span class="p" data-group-id="1175483496-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="1175483496-6">)</span><span class="w">
│ │ │ │ +in the list that satisfy the predicate:</p><pre><code class="makeup erlang" translate="no"><span class="nf">filter</span><span class="p" data-group-id="5564060006-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5564060006-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5564060006-2">]</span><span class="p" data-group-id="5564060006-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="5564060006-3">(</span><span class="n">H</span><span class="p" data-group-id="5564060006-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5564060006-4">[</span><span class="n">H</span><span class="p">|</span><span class="nf">filter</span><span class="p" data-group-id="5564060006-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="5564060006-5">)</span><span class="p" data-group-id="5564060006-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">filter</span><span class="p" data-group-id="5564060006-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="5564060006-6">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">filter</span><span class="p" data-group-id="1175483496-7">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1175483496-8">[</span><span class="p" data-group-id="1175483496-8">]</span><span class="p" data-group-id="1175483496-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1175483496-9">[</span><span class="p" data-group-id="1175483496-9">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="0071213280-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0071213280-2">[</span><span class="mi">500</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="0071213280-2">]</span><span class="p" data-group-id="0071213280-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0071213280-3">[</span><span class="mi">500</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="0071213280-3">]</span></code></pre><p>Combining maps and filters enables writing of very succinct code. For example,
│ │ │ │ +</span><span class="nf">filter</span><span class="p" data-group-id="5564060006-7">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5564060006-8">[</span><span class="p" data-group-id="5564060006-8">]</span><span class="p" data-group-id="5564060006-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5564060006-9">[</span><span class="p" data-group-id="5564060006-9">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="0672735444-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0672735444-2">[</span><span class="mi">500</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="0672735444-2">]</span><span class="p" data-group-id="0672735444-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0672735444-3">[</span><span class="mi">500</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="0672735444-3">]</span></code></pre><p>Combining maps and filters enables writing of very succinct code. For example,
│ │ │ │  to define a set difference function <code class="inline">diff(L1, L2)</code> to be the difference between
│ │ │ │ -the lists <code class="inline">L1</code> and <code class="inline">L2</code>, the code can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">diff</span><span class="p" data-group-id="9131037274-1">(</span><span class="n">L1</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="9131037274-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">filter</span><span class="p" data-group-id="9131037274-2">(</span><span class="nf">fun</span><span class="p" data-group-id="9131037274-3">(</span><span class="n">X</span><span class="p" data-group-id="9131037274-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ow">not</span><span class="w"> </span><span class="nf">member</span><span class="p" data-group-id="9131037274-4">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="9131037274-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L1</span><span class="p" data-group-id="9131037274-2">)</span><span class="p">.</span></code></pre><p>This gives the list of all elements in L1 that are not contained in L2.</p><p>The AND intersection of the lists <code class="inline">L1</code> and <code class="inline">L2</code> is also easily defined:</p><pre><code class="makeup erlang" translate="no"><span class="nf">intersection</span><span class="p" data-group-id="5978591380-1">(</span><span class="n">L1</span><span class="p">,</span><span class="n">L2</span><span class="p" data-group-id="5978591380-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">filter</span><span class="p" data-group-id="5978591380-2">(</span><span class="nf">fun</span><span class="p" data-group-id="5978591380-3">(</span><span class="n">X</span><span class="p" data-group-id="5978591380-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">member</span><span class="p" data-group-id="5978591380-4">(</span><span class="n">X</span><span class="p">,</span><span class="n">L1</span><span class="p" data-group-id="5978591380-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="5978591380-2">)</span><span class="p">.</span></code></pre><h3 id="takewhile" class="section-heading">
│ │ │ │ +the lists <code class="inline">L1</code> and <code class="inline">L2</code>, the code can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">diff</span><span class="p" data-group-id="7810990331-1">(</span><span class="n">L1</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="7810990331-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">filter</span><span class="p" data-group-id="7810990331-2">(</span><span class="nf">fun</span><span class="p" data-group-id="7810990331-3">(</span><span class="n">X</span><span class="p" data-group-id="7810990331-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ow">not</span><span class="w"> </span><span class="nf">member</span><span class="p" data-group-id="7810990331-4">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="7810990331-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L1</span><span class="p" data-group-id="7810990331-2">)</span><span class="p">.</span></code></pre><p>This gives the list of all elements in L1 that are not contained in L2.</p><p>The AND intersection of the lists <code class="inline">L1</code> and <code class="inline">L2</code> is also easily defined:</p><pre><code class="makeup erlang" translate="no"><span class="nf">intersection</span><span class="p" data-group-id="8209005553-1">(</span><span class="n">L1</span><span class="p">,</span><span class="n">L2</span><span class="p" data-group-id="8209005553-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">filter</span><span class="p" data-group-id="8209005553-2">(</span><span class="nf">fun</span><span class="p" data-group-id="8209005553-3">(</span><span class="n">X</span><span class="p" data-group-id="8209005553-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">member</span><span class="p" data-group-id="8209005553-4">(</span><span class="n">X</span><span class="p">,</span><span class="n">L1</span><span class="p" data-group-id="8209005553-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="8209005553-2">)</span><span class="p">.</span></code></pre><h3 id="takewhile" class="section-heading">
│ │ │ │    <a href="#takewhile" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">takewhile</span>
│ │ │ │  </h3>
│ │ │ │  <p><a href="../../../lib/stdlib/doc/html/lists.html#takewhile/2"><code class="inline">lists:takewhile/2</code></a> takes elements <code class="inline">X</code> from a list <code class="inline">L</code> as long as the predicate
│ │ │ │ -<code class="inline">P(X)</code> is true:</p><pre><code class="makeup erlang" translate="no"><span class="nf">takewhile</span><span class="p" data-group-id="0704238988-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0704238988-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0704238988-2">]</span><span class="p" data-group-id="0704238988-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="0704238988-3">(</span><span class="n">H</span><span class="p" data-group-id="0704238988-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0704238988-4">[</span><span class="n">H</span><span class="p">|</span><span class="nf">takewhile</span><span class="p" data-group-id="0704238988-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="0704238988-5">)</span><span class="p" data-group-id="0704238988-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0704238988-6">[</span><span class="p" data-group-id="0704238988-6">]</span><span class="w">
│ │ │ │ +<code class="inline">P(X)</code> is true:</p><pre><code class="makeup erlang" translate="no"><span class="nf">takewhile</span><span class="p" data-group-id="1678014776-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1678014776-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1678014776-2">]</span><span class="p" data-group-id="1678014776-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="1678014776-3">(</span><span class="n">H</span><span class="p" data-group-id="1678014776-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1678014776-4">[</span><span class="n">H</span><span class="p">|</span><span class="nf">takewhile</span><span class="p" data-group-id="1678014776-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="1678014776-5">)</span><span class="p" data-group-id="1678014776-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1678014776-6">[</span><span class="p" data-group-id="1678014776-6">]</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">takewhile</span><span class="p" data-group-id="0704238988-7">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0704238988-8">[</span><span class="p" data-group-id="0704238988-8">]</span><span class="p" data-group-id="0704238988-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0704238988-9">[</span><span class="p" data-group-id="0704238988-9">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">takewhile</span><span class="p" data-group-id="3241388190-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3241388190-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3241388190-2">]</span><span class="p" data-group-id="3241388190-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3241388190-3">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="3241388190-3">]</span></code></pre><h3 id="dropwhile" class="section-heading">
│ │ │ │ +</span><span class="nf">takewhile</span><span class="p" data-group-id="1678014776-7">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1678014776-8">[</span><span class="p" data-group-id="1678014776-8">]</span><span class="p" data-group-id="1678014776-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1678014776-9">[</span><span class="p" data-group-id="1678014776-9">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">takewhile</span><span class="p" data-group-id="0629376659-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0629376659-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="0629376659-2">]</span><span class="p" data-group-id="0629376659-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0629376659-3">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="0629376659-3">]</span></code></pre><h3 id="dropwhile" class="section-heading">
│ │ │ │    <a href="#dropwhile" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">dropwhile</span>
│ │ │ │  </h3>
│ │ │ │ -<p><a href="../../../lib/stdlib/doc/html/lists.html#dropwhile/2"><code class="inline">lists:dropwhile/2</code></a> is the complement of <code class="inline">takewhile</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">dropwhile</span><span class="p" data-group-id="6454064811-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6454064811-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6454064811-2">]</span><span class="p" data-group-id="6454064811-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="6454064811-3">(</span><span class="n">H</span><span class="p" data-group-id="6454064811-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">dropwhile</span><span class="p" data-group-id="6454064811-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="6454064811-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6454064811-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6454064811-5">]</span><span class="w">
│ │ │ │ +<p><a href="../../../lib/stdlib/doc/html/lists.html#dropwhile/2"><code class="inline">lists:dropwhile/2</code></a> is the complement of <code class="inline">takewhile</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">dropwhile</span><span class="p" data-group-id="9055996744-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9055996744-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9055996744-2">]</span><span class="p" data-group-id="9055996744-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="9055996744-3">(</span><span class="n">H</span><span class="p" data-group-id="9055996744-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">dropwhile</span><span class="p" data-group-id="9055996744-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="9055996744-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9055996744-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9055996744-5">]</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">dropwhile</span><span class="p" data-group-id="6454064811-6">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6454064811-7">[</span><span class="p" data-group-id="6454064811-7">]</span><span class="p" data-group-id="6454064811-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6454064811-8">[</span><span class="p" data-group-id="6454064811-8">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">dropwhile</span><span class="p" data-group-id="1488652958-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1488652958-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="1488652958-2">]</span><span class="p" data-group-id="1488652958-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1488652958-3">[</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="1488652958-3">]</span></code></pre><h3 id="splitwith" class="section-heading">
│ │ │ │ +</span><span class="nf">dropwhile</span><span class="p" data-group-id="9055996744-6">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9055996744-7">[</span><span class="p" data-group-id="9055996744-7">]</span><span class="p" data-group-id="9055996744-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9055996744-8">[</span><span class="p" data-group-id="9055996744-8">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">dropwhile</span><span class="p" data-group-id="9042556318-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9042556318-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="9042556318-2">]</span><span class="p" data-group-id="9042556318-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9042556318-3">[</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="9042556318-3">]</span></code></pre><h3 id="splitwith" class="section-heading">
│ │ │ │    <a href="#splitwith" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">splitwith</span>
│ │ │ │  </h3>
│ │ │ │  <p><a href="../../../lib/stdlib/doc/html/lists.html#splitwith/2"><code class="inline">lists:splitwith/2</code></a> splits the list <code class="inline">L</code> into the two sublists <code class="inline">{L1, L2}</code>, where
│ │ │ │ -<code class="inline">L1 = takewhile(P, L)</code> and <code class="inline">L2 = dropwhile(P, L)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">splitwith</span><span class="p" data-group-id="4775432573-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4775432573-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">splitwith</span><span class="p" data-group-id="4775432573-2">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4775432573-3">[</span><span class="p" data-group-id="4775432573-3">]</span><span class="p" data-group-id="4775432573-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">L1 = takewhile(P, L)</code> and <code class="inline">L2 = dropwhile(P, L)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">splitwith</span><span class="p" data-group-id="8112221511-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="8112221511-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">splitwith</span><span class="p" data-group-id="8112221511-2">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8112221511-3">[</span><span class="p" data-group-id="8112221511-3">]</span><span class="p" data-group-id="8112221511-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">splitwith</span><span class="p" data-group-id="4775432573-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4775432573-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4775432573-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4775432573-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="4775432573-6">(</span><span class="n">H</span><span class="p" data-group-id="4775432573-6">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">splitwith</span><span class="p" data-group-id="4775432573-7">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4775432573-8">[</span><span class="n">H</span><span class="p">|</span><span class="n">L</span><span class="p" data-group-id="4775432573-8">]</span><span class="p" data-group-id="4775432573-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4775432573-9">{</span><span class="nf">reverse</span><span class="p" data-group-id="4775432573-10">(</span><span class="n">L</span><span class="p" data-group-id="4775432573-10">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4775432573-11">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4775432573-11">]</span><span class="p" data-group-id="4775432573-9">}</span><span class="w">
│ │ │ │ +</span><span class="nf">splitwith</span><span class="p" data-group-id="8112221511-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8112221511-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8112221511-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="8112221511-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="8112221511-6">(</span><span class="n">H</span><span class="p" data-group-id="8112221511-6">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">splitwith</span><span class="p" data-group-id="8112221511-7">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8112221511-8">[</span><span class="n">H</span><span class="p">|</span><span class="n">L</span><span class="p" data-group-id="8112221511-8">]</span><span class="p" data-group-id="8112221511-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8112221511-9">{</span><span class="nf">reverse</span><span class="p" data-group-id="8112221511-10">(</span><span class="n">L</span><span class="p" data-group-id="8112221511-10">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8112221511-11">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8112221511-11">]</span><span class="p" data-group-id="8112221511-9">}</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">splitwith</span><span class="p" data-group-id="4775432573-12">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4775432573-13">[</span><span class="p" data-group-id="4775432573-13">]</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4775432573-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4775432573-14">{</span><span class="nf">reverse</span><span class="p" data-group-id="4775432573-15">(</span><span class="n">L</span><span class="p" data-group-id="4775432573-15">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4775432573-16">[</span><span class="p" data-group-id="4775432573-16">]</span><span class="p" data-group-id="4775432573-14">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">splitwith</span><span class="p" data-group-id="9492738653-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9492738653-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="9492738653-2">]</span><span class="p" data-group-id="9492738653-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9492738653-3">{</span><span class="p" data-group-id="9492738653-4">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="9492738653-4">]</span><span class="p">,</span><span class="p" data-group-id="9492738653-5">[</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="9492738653-5">]</span><span class="p" data-group-id="9492738653-3">}</span></code></pre><h2 id="funs-returning-funs" class="section-heading">
│ │ │ │ +</span><span class="nf">splitwith</span><span class="p" data-group-id="8112221511-12">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8112221511-13">[</span><span class="p" data-group-id="8112221511-13">]</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="8112221511-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8112221511-14">{</span><span class="nf">reverse</span><span class="p" data-group-id="8112221511-15">(</span><span class="n">L</span><span class="p" data-group-id="8112221511-15">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8112221511-16">[</span><span class="p" data-group-id="8112221511-16">]</span><span class="p" data-group-id="8112221511-14">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">splitwith</span><span class="p" data-group-id="6047849080-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6047849080-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="6047849080-2">]</span><span class="p" data-group-id="6047849080-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6047849080-3">{</span><span class="p" data-group-id="6047849080-4">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="6047849080-4">]</span><span class="p">,</span><span class="p" data-group-id="6047849080-5">[</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="6047849080-5">]</span><span class="p" data-group-id="6047849080-3">}</span></code></pre><h2 id="funs-returning-funs" class="section-heading">
│ │ │ │    <a href="#funs-returning-funs" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Funs Returning Funs</span>
│ │ │ │  </h2>
│ │ │ │  <p>So far, only functions that take funs as arguments have been described. More
│ │ │ │  powerful functions, that themselves return funs, can also be written. The
│ │ │ │  following examples illustrate these types of functions.</p><h3 id="simple-higher-order-functions" class="section-heading">
│ │ │ │    <a href="#simple-higher-order-functions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Simple Higher Order Functions</span>
│ │ │ │  </h3>
│ │ │ │  <p><code class="inline">Adder(X)</code> is a function that given <code class="inline">X</code>, returns a new function <code class="inline">G</code> such that
│ │ │ │ -<code class="inline">G(K)</code> returns <code class="inline">K + X</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Adder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="6571359503-1">(</span><span class="n">X</span><span class="p" data-group-id="6571359503-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="6571359503-2">(</span><span class="n">Y</span><span class="p" data-group-id="6571359503-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">G(K)</code> returns <code class="inline">K + X</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Adder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="1878582532-1">(</span><span class="n">X</span><span class="p" data-group-id="1878582532-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="1878582532-2">(</span><span class="n">Y</span><span class="p" data-group-id="1878582532-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">Add6</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Adder</span><span class="p" data-group-id="6571359503-3">(</span><span class="mi">6</span><span class="p" data-group-id="6571359503-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">Add6</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Adder</span><span class="p" data-group-id="1878582532-3">(</span><span class="mi">6</span><span class="p" data-group-id="1878582532-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">Add6</span><span class="p" data-group-id="6571359503-4">(</span><span class="mi">10</span><span class="p" data-group-id="6571359503-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">Add6</span><span class="p" data-group-id="1878582532-4">(</span><span class="mi">10</span><span class="p" data-group-id="1878582532-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">16</span></code></pre><h3 id="infinite-lists" class="section-heading">
│ │ │ │    <a href="#infinite-lists" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Infinite Lists</span>
│ │ │ │  </h3>
│ │ │ │ -<p>The idea is to write something like:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3930172062-1">(</span><span class="ss">lazy</span><span class="p" data-group-id="3930172062-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3930172062-2">(</span><span class="p" data-group-id="3930172062-3">[</span><span class="ss">ints_from</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3930172062-3">]</span><span class="p" data-group-id="3930172062-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">ints_from</span><span class="p" data-group-id="3930172062-4">(</span><span class="n">N</span><span class="p" data-group-id="3930172062-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">fun</span><span class="p" data-group-id="3930172062-5">(</span><span class="p" data-group-id="3930172062-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="3930172062-6">[</span><span class="n">N</span><span class="p">|</span><span class="nf">ints_from</span><span class="p" data-group-id="3930172062-7">(</span><span class="n">N</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="3930172062-7">)</span><span class="p" data-group-id="3930172062-6">]</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Then proceed as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">XX</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lazy</span><span class="p">:</span><span class="nf">ints_from</span><span class="p" data-group-id="5311181841-1">(</span><span class="mi">1</span><span class="p" data-group-id="5311181841-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>The idea is to write something like:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4472046006-1">(</span><span class="ss">lazy</span><span class="p" data-group-id="4472046006-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4472046006-2">(</span><span class="p" data-group-id="4472046006-3">[</span><span class="ss">ints_from</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4472046006-3">]</span><span class="p" data-group-id="4472046006-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">ints_from</span><span class="p" data-group-id="4472046006-4">(</span><span class="n">N</span><span class="p" data-group-id="4472046006-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">fun</span><span class="p" data-group-id="4472046006-5">(</span><span class="p" data-group-id="4472046006-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="4472046006-6">[</span><span class="n">N</span><span class="p">|</span><span class="nf">ints_from</span><span class="p" data-group-id="4472046006-7">(</span><span class="n">N</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="4472046006-7">)</span><span class="p" data-group-id="4472046006-6">]</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Then proceed as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">XX</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lazy</span><span class="p">:</span><span class="nf">ints_from</span><span class="p" data-group-id="3215321861-1">(</span><span class="mi">1</span><span class="p" data-group-id="3215321861-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">lazy</span><span class="p">.</span><span class="mf">0.29874839</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">XX</span><span class="p" data-group-id="5311181841-2">(</span><span class="p" data-group-id="5311181841-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5311181841-3">[</span><span class="mi">1</span><span class="p">|</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">lazy</span><span class="p">.</span><span class="mf">0.29874839</span><span class="o">&gt;</span><span class="p" data-group-id="5311181841-3">]</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nf">hd</span><span class="p" data-group-id="5311181841-4">(</span><span class="n">XX</span><span class="p" data-group-id="5311181841-5">(</span><span class="p" data-group-id="5311181841-5">)</span><span class="p" data-group-id="5311181841-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">XX</span><span class="p" data-group-id="3215321861-2">(</span><span class="p" data-group-id="3215321861-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3215321861-3">[</span><span class="mi">1</span><span class="p">|</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">lazy</span><span class="p">.</span><span class="mf">0.29874839</span><span class="o">&gt;</span><span class="p" data-group-id="3215321861-3">]</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nf">hd</span><span class="p" data-group-id="3215321861-4">(</span><span class="n">XX</span><span class="p" data-group-id="3215321861-5">(</span><span class="p" data-group-id="3215321861-5">)</span><span class="p" data-group-id="3215321861-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">1</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">tl</span><span class="p" data-group-id="5311181841-6">(</span><span class="n">XX</span><span class="p" data-group-id="5311181841-7">(</span><span class="p" data-group-id="5311181841-7">)</span><span class="p" data-group-id="5311181841-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">tl</span><span class="p" data-group-id="3215321861-6">(</span><span class="n">XX</span><span class="p" data-group-id="3215321861-7">(</span><span class="p" data-group-id="3215321861-7">)</span><span class="p" data-group-id="3215321861-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">lazy</span><span class="p">.</span><span class="mf">0.29874839</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nf">hd</span><span class="p" data-group-id="5311181841-8">(</span><span class="n">Y</span><span class="p" data-group-id="5311181841-9">(</span><span class="p" data-group-id="5311181841-9">)</span><span class="p" data-group-id="5311181841-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nf">hd</span><span class="p" data-group-id="3215321861-8">(</span><span class="n">Y</span><span class="p" data-group-id="3215321861-9">(</span><span class="p" data-group-id="3215321861-9">)</span><span class="p" data-group-id="3215321861-8">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">2</span></code></pre><p>And so on. This is an example of &quot;lazy embedding&quot;.</p><h3 id="parsing" class="section-heading">
│ │ │ │    <a href="#parsing" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Parsing</span>
│ │ │ │  </h3>
│ │ │ │ -<p>The following examples show parsers of the following type:</p><pre><code class="makeup erlang" translate="no"><span class="n">Parser</span><span class="p" data-group-id="8171536784-1">(</span><span class="n">Toks</span><span class="p" data-group-id="8171536784-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8171536784-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Tree</span><span class="p">,</span><span class="w"> </span><span class="n">Toks1</span><span class="p" data-group-id="8171536784-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">fail</span></code></pre><p><code class="inline">Toks</code> is the list of tokens to be parsed. A successful parse returns
│ │ │ │ +<p>The following examples show parsers of the following type:</p><pre><code class="makeup erlang" translate="no"><span class="n">Parser</span><span class="p" data-group-id="4402681915-1">(</span><span class="n">Toks</span><span class="p" data-group-id="4402681915-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4402681915-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Tree</span><span class="p">,</span><span class="w"> </span><span class="n">Toks1</span><span class="p" data-group-id="4402681915-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">fail</span></code></pre><p><code class="inline">Toks</code> is the list of tokens to be parsed. A successful parse returns
│ │ │ │  <code class="inline">{ok, Tree, Toks1}</code>.</p><ul><li><code class="inline">Tree</code> is a parse tree.</li><li><code class="inline">Toks1</code> is a tail of <code class="inline">Toks</code> that contains symbols encountered after the
│ │ │ │  structure that was correctly parsed.</li></ul><p>An unsuccessful parse returns <code class="inline">fail</code>.</p><p>The following example illustrates a simple, functional parser that parses the
│ │ │ │  grammar:</p><pre><code class="text">(a | b) &amp; (c | d)</code></pre><p>The following code defines a function <code class="inline">pconst(X)</code> in the module <code class="inline">funparse</code>,
│ │ │ │ -which returns a fun that parses a list of tokens:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pconst</span><span class="p" data-group-id="8683724209-1">(</span><span class="n">X</span><span class="p" data-group-id="8683724209-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8683724209-2">(</span><span class="n">T</span><span class="p" data-group-id="8683724209-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +which returns a fun that parses a list of tokens:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pconst</span><span class="p" data-group-id="3306705465-1">(</span><span class="n">X</span><span class="p" data-group-id="3306705465-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="3306705465-2">(</span><span class="n">T</span><span class="p" data-group-id="3306705465-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │         </span><span class="k">case</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -           </span><span class="p" data-group-id="8683724209-3">[</span><span class="n">X</span><span class="p">|</span><span class="n">T1</span><span class="p" data-group-id="8683724209-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8683724209-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8683724209-5">{</span><span class="ss">const</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="8683724209-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="8683724209-4">}</span><span class="p">;</span><span class="w">
│ │ │ │ +           </span><span class="p" data-group-id="3306705465-3">[</span><span class="n">X</span><span class="p">|</span><span class="n">T1</span><span class="p" data-group-id="3306705465-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3306705465-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3306705465-5">{</span><span class="ss">const</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="3306705465-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="3306705465-4">}</span><span class="p">;</span><span class="w">
│ │ │ │             </span><span class="p">_</span><span class="w">      </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">fail</span><span class="w">
│ │ │ │         </span><span class="k">end</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>This function can be used as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">pconst</span><span class="p" data-group-id="5515879322-1">(</span><span class="ss">a</span><span class="p" data-group-id="5515879322-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>This function can be used as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">pconst</span><span class="p" data-group-id="8900496212-1">(</span><span class="ss">a</span><span class="p" data-group-id="8900496212-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">funparse</span><span class="p">.</span><span class="mf">0.22674075</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="p" data-group-id="5515879322-2">(</span><span class="p" data-group-id="5515879322-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5515879322-3">]</span><span class="p" data-group-id="5515879322-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5515879322-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="5515879322-5">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="5515879322-5">}</span><span class="p">,</span><span class="p" data-group-id="5515879322-6">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5515879322-6">]</span><span class="p" data-group-id="5515879322-4">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="p" data-group-id="5515879322-7">(</span><span class="p" data-group-id="5515879322-8">[</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="5515879322-8">]</span><span class="p" data-group-id="5515879322-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="p" data-group-id="8900496212-2">(</span><span class="p" data-group-id="8900496212-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="8900496212-3">]</span><span class="p" data-group-id="8900496212-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8900496212-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="8900496212-5">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="8900496212-5">}</span><span class="p">,</span><span class="p" data-group-id="8900496212-6">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="8900496212-6">]</span><span class="p" data-group-id="8900496212-4">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="p" data-group-id="8900496212-7">(</span><span class="p" data-group-id="8900496212-8">[</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="8900496212-8">]</span><span class="p" data-group-id="8900496212-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">fail</span></code></pre><p>Next, the two higher order functions <code class="inline">pand</code> and <code class="inline">por</code> are defined. They combine
│ │ │ │ -primitive parsers to produce more complex parsers.</p><p>First <code class="inline">pand</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pand</span><span class="p" data-group-id="3419458336-1">(</span><span class="n">P1</span><span class="p">,</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="3419458336-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="3419458336-2">(</span><span class="n">T</span><span class="p" data-group-id="3419458336-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="k">case</span><span class="w"> </span><span class="n">P1</span><span class="p" data-group-id="3419458336-3">(</span><span class="n">T</span><span class="p" data-group-id="3419458336-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="3419458336-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="3419458336-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="k">case</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="3419458336-5">(</span><span class="n">T1</span><span class="p" data-group-id="3419458336-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -                    </span><span class="p" data-group-id="3419458336-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p" data-group-id="3419458336-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                        </span><span class="p" data-group-id="3419458336-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3419458336-8">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p" data-group-id="3419458336-8">}</span><span class="p" data-group-id="3419458336-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +primitive parsers to produce more complex parsers.</p><p>First <code class="inline">pand</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pand</span><span class="p" data-group-id="2852493106-1">(</span><span class="n">P1</span><span class="p">,</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="2852493106-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="2852493106-2">(</span><span class="n">T</span><span class="p" data-group-id="2852493106-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="k">case</span><span class="w"> </span><span class="n">P1</span><span class="p" data-group-id="2852493106-3">(</span><span class="n">T</span><span class="p" data-group-id="2852493106-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="2852493106-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="2852493106-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                </span><span class="k">case</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="2852493106-5">(</span><span class="n">T1</span><span class="p" data-group-id="2852493106-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +                    </span><span class="p" data-group-id="2852493106-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p" data-group-id="2852493106-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                        </span><span class="p" data-group-id="2852493106-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2852493106-8">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p" data-group-id="2852493106-8">}</span><span class="p" data-group-id="2852493106-7">}</span><span class="p">;</span><span class="w">
│ │ │ │                      </span><span class="ss">fail</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                          </span><span class="ss">fail</span><span class="w">
│ │ │ │                  </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │              </span><span class="ss">fail</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                  </span><span class="ss">fail</span><span class="w">
│ │ │ │          </span><span class="k">end</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Given a parser <code class="inline">P1</code> for grammar <code class="inline">G1</code>, and a parser <code class="inline">P2</code> for grammar <code class="inline">G2</code>,
│ │ │ │  <code class="inline">pand(P1, P2)</code> returns a parser for the grammar, which consists of sequences of
│ │ │ │  tokens that satisfy <code class="inline">G1</code>, followed by sequences of tokens that satisfy <code class="inline">G2</code>.</p><p><code class="inline">por(P1, P2)</code> returns a parser for the language described by the grammar <code class="inline">G1</code> or
│ │ │ │ -<code class="inline">G2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">por</span><span class="p" data-group-id="5237690494-1">(</span><span class="n">P1</span><span class="p">,</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="5237690494-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5237690494-2">(</span><span class="n">T</span><span class="p" data-group-id="5237690494-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="k">case</span><span class="w"> </span><span class="n">P1</span><span class="p" data-group-id="5237690494-3">(</span><span class="n">T</span><span class="p" data-group-id="5237690494-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="5237690494-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="5237690494-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="p" data-group-id="5237690494-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5237690494-6">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="n">R</span><span class="p" data-group-id="5237690494-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="5237690494-5">}</span><span class="p">;</span><span class="w">
│ │ │ │ +<code class="inline">G2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">por</span><span class="p" data-group-id="8325691161-1">(</span><span class="n">P1</span><span class="p">,</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="8325691161-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8325691161-2">(</span><span class="n">T</span><span class="p" data-group-id="8325691161-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="k">case</span><span class="w"> </span><span class="n">P1</span><span class="p" data-group-id="8325691161-3">(</span><span class="n">T</span><span class="p" data-group-id="8325691161-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="8325691161-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="8325691161-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                </span><span class="p" data-group-id="8325691161-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8325691161-6">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="n">R</span><span class="p" data-group-id="8325691161-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="8325691161-5">}</span><span class="p">;</span><span class="w">
│ │ │ │              </span><span class="ss">fail</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="k">case</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="5237690494-7">(</span><span class="n">T</span><span class="p" data-group-id="5237690494-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -                    </span><span class="p" data-group-id="5237690494-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="5237690494-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                        </span><span class="p" data-group-id="5237690494-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5237690494-10">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="n">R1</span><span class="p" data-group-id="5237690494-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="5237690494-9">}</span><span class="p">;</span><span class="w">
│ │ │ │ +                </span><span class="k">case</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="8325691161-7">(</span><span class="n">T</span><span class="p" data-group-id="8325691161-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +                    </span><span class="p" data-group-id="8325691161-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="8325691161-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                        </span><span class="p" data-group-id="8325691161-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8325691161-10">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="n">R1</span><span class="p" data-group-id="8325691161-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="8325691161-9">}</span><span class="p">;</span><span class="w">
│ │ │ │                      </span><span class="ss">fail</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                          </span><span class="ss">fail</span><span class="w">
│ │ │ │                  </span><span class="k">end</span><span class="w">
│ │ │ │          </span><span class="k">end</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The original problem was to parse the grammar <code class="inline">(a | b) &amp; (c | d)</code>. The following
│ │ │ │ -code addresses this problem:</p><pre><code class="makeup erlang" translate="no"><span class="nf">grammar</span><span class="p" data-group-id="9814971713-1">(</span><span class="p" data-group-id="9814971713-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">pand</span><span class="p" data-group-id="9814971713-2">(</span><span class="w">
│ │ │ │ -         </span><span class="nf">por</span><span class="p" data-group-id="9814971713-3">(</span><span class="nf">pconst</span><span class="p" data-group-id="9814971713-4">(</span><span class="ss">a</span><span class="p" data-group-id="9814971713-4">)</span><span class="p">,</span><span class="w"> </span><span class="nf">pconst</span><span class="p" data-group-id="9814971713-5">(</span><span class="ss">b</span><span class="p" data-group-id="9814971713-5">)</span><span class="p" data-group-id="9814971713-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="nf">por</span><span class="p" data-group-id="9814971713-6">(</span><span class="nf">pconst</span><span class="p" data-group-id="9814971713-7">(</span><span class="ss">c</span><span class="p" data-group-id="9814971713-7">)</span><span class="p">,</span><span class="w"> </span><span class="nf">pconst</span><span class="p" data-group-id="9814971713-8">(</span><span class="ss">d</span><span class="p" data-group-id="9814971713-8">)</span><span class="p" data-group-id="9814971713-6">)</span><span class="p" data-group-id="9814971713-2">)</span><span class="p">.</span></code></pre><p>The following code adds a parser interface to the grammar:</p><pre><code class="makeup erlang" translate="no"><span class="nf">parse</span><span class="p" data-group-id="7261161208-1">(</span><span class="n">List</span><span class="p" data-group-id="7261161208-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7261161208-2">(</span><span class="nf">grammar</span><span class="p" data-group-id="7261161208-3">(</span><span class="p" data-group-id="7261161208-3">)</span><span class="p" data-group-id="7261161208-2">)</span><span class="p" data-group-id="7261161208-4">(</span><span class="n">List</span><span class="p" data-group-id="7261161208-4">)</span><span class="p">.</span></code></pre><p>The parser can be tested as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="3561247233-1">(</span><span class="p" data-group-id="3561247233-2">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3561247233-2">]</span><span class="p" data-group-id="3561247233-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3561247233-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="3561247233-4">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="3561247233-5">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="3561247233-6">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="3561247233-6">}</span><span class="p" data-group-id="3561247233-5">}</span><span class="p">,</span><span class="p" data-group-id="3561247233-7">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="3561247233-8">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3561247233-8">}</span><span class="p" data-group-id="3561247233-7">}</span><span class="p" data-group-id="3561247233-4">}</span><span class="p" data-group-id="3561247233-3">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="3561247233-9">(</span><span class="p" data-group-id="3561247233-10">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="3561247233-10">]</span><span class="p" data-group-id="3561247233-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3561247233-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="3561247233-12">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="3561247233-13">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="3561247233-14">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="3561247233-14">}</span><span class="p" data-group-id="3561247233-13">}</span><span class="p">,</span><span class="p" data-group-id="3561247233-15">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="3561247233-16">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="3561247233-16">}</span><span class="p" data-group-id="3561247233-15">}</span><span class="p" data-group-id="3561247233-12">}</span><span class="p" data-group-id="3561247233-11">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="3561247233-17">(</span><span class="p" data-group-id="3561247233-18">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3561247233-18">]</span><span class="p" data-group-id="3561247233-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3561247233-19">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="3561247233-20">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="3561247233-21">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="3561247233-22">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3561247233-22">}</span><span class="p" data-group-id="3561247233-21">}</span><span class="p">,</span><span class="p" data-group-id="3561247233-23">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="3561247233-24">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3561247233-24">}</span><span class="p" data-group-id="3561247233-23">}</span><span class="p" data-group-id="3561247233-20">}</span><span class="p" data-group-id="3561247233-19">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="3561247233-25">(</span><span class="p" data-group-id="3561247233-26">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="3561247233-26">]</span><span class="p" data-group-id="3561247233-25">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3561247233-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="3561247233-28">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="3561247233-29">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="3561247233-30">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3561247233-30">}</span><span class="p" data-group-id="3561247233-29">}</span><span class="p">,</span><span class="p" data-group-id="3561247233-31">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="3561247233-32">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="3561247233-32">}</span><span class="p" data-group-id="3561247233-31">}</span><span class="p" data-group-id="3561247233-28">}</span><span class="p" data-group-id="3561247233-27">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="3561247233-33">(</span><span class="p" data-group-id="3561247233-34">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3561247233-34">]</span><span class="p" data-group-id="3561247233-33">)</span><span class="p">.</span><span class="w">
│ │ │ │ +code addresses this problem:</p><pre><code class="makeup erlang" translate="no"><span class="nf">grammar</span><span class="p" data-group-id="4138318125-1">(</span><span class="p" data-group-id="4138318125-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">pand</span><span class="p" data-group-id="4138318125-2">(</span><span class="w">
│ │ │ │ +         </span><span class="nf">por</span><span class="p" data-group-id="4138318125-3">(</span><span class="nf">pconst</span><span class="p" data-group-id="4138318125-4">(</span><span class="ss">a</span><span class="p" data-group-id="4138318125-4">)</span><span class="p">,</span><span class="w"> </span><span class="nf">pconst</span><span class="p" data-group-id="4138318125-5">(</span><span class="ss">b</span><span class="p" data-group-id="4138318125-5">)</span><span class="p" data-group-id="4138318125-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="nf">por</span><span class="p" data-group-id="4138318125-6">(</span><span class="nf">pconst</span><span class="p" data-group-id="4138318125-7">(</span><span class="ss">c</span><span class="p" data-group-id="4138318125-7">)</span><span class="p">,</span><span class="w"> </span><span class="nf">pconst</span><span class="p" data-group-id="4138318125-8">(</span><span class="ss">d</span><span class="p" data-group-id="4138318125-8">)</span><span class="p" data-group-id="4138318125-6">)</span><span class="p" data-group-id="4138318125-2">)</span><span class="p">.</span></code></pre><p>The following code adds a parser interface to the grammar:</p><pre><code class="makeup erlang" translate="no"><span class="nf">parse</span><span class="p" data-group-id="8996948772-1">(</span><span class="n">List</span><span class="p" data-group-id="8996948772-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8996948772-2">(</span><span class="nf">grammar</span><span class="p" data-group-id="8996948772-3">(</span><span class="p" data-group-id="8996948772-3">)</span><span class="p" data-group-id="8996948772-2">)</span><span class="p" data-group-id="8996948772-4">(</span><span class="n">List</span><span class="p" data-group-id="8996948772-4">)</span><span class="p">.</span></code></pre><p>The parser can be tested as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="6802965000-1">(</span><span class="p" data-group-id="6802965000-2">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6802965000-2">]</span><span class="p" data-group-id="6802965000-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6802965000-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="6802965000-4">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="6802965000-5">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="6802965000-6">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="6802965000-6">}</span><span class="p" data-group-id="6802965000-5">}</span><span class="p">,</span><span class="p" data-group-id="6802965000-7">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="6802965000-8">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6802965000-8">}</span><span class="p" data-group-id="6802965000-7">}</span><span class="p" data-group-id="6802965000-4">}</span><span class="p" data-group-id="6802965000-3">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="6802965000-9">(</span><span class="p" data-group-id="6802965000-10">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="6802965000-10">]</span><span class="p" data-group-id="6802965000-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6802965000-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="6802965000-12">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="6802965000-13">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="6802965000-14">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="6802965000-14">}</span><span class="p" data-group-id="6802965000-13">}</span><span class="p">,</span><span class="p" data-group-id="6802965000-15">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6802965000-16">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="6802965000-16">}</span><span class="p" data-group-id="6802965000-15">}</span><span class="p" data-group-id="6802965000-12">}</span><span class="p" data-group-id="6802965000-11">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="6802965000-17">(</span><span class="p" data-group-id="6802965000-18">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6802965000-18">]</span><span class="p" data-group-id="6802965000-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6802965000-19">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="6802965000-20">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="6802965000-21">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6802965000-22">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6802965000-22">}</span><span class="p" data-group-id="6802965000-21">}</span><span class="p">,</span><span class="p" data-group-id="6802965000-23">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="6802965000-24">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6802965000-24">}</span><span class="p" data-group-id="6802965000-23">}</span><span class="p" data-group-id="6802965000-20">}</span><span class="p" data-group-id="6802965000-19">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="6802965000-25">(</span><span class="p" data-group-id="6802965000-26">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="6802965000-26">]</span><span class="p" data-group-id="6802965000-25">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6802965000-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="6802965000-28">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="6802965000-29">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6802965000-30">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6802965000-30">}</span><span class="p" data-group-id="6802965000-29">}</span><span class="p">,</span><span class="p" data-group-id="6802965000-31">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6802965000-32">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="6802965000-32">}</span><span class="p" data-group-id="6802965000-31">}</span><span class="p" data-group-id="6802965000-28">}</span><span class="p" data-group-id="6802965000-27">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="6802965000-33">(</span><span class="p" data-group-id="6802965000-34">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6802965000-34">]</span><span class="p" data-group-id="6802965000-33">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">fail</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/expressions.xhtml
│ │ │ │ @@ -56,81 +56,81 @@
│ │ │ │  </span><span class="n">Phone_number</span><span class="w">
│ │ │ │  </span><span class="p">_</span><span class="w">
│ │ │ │  </span><span class="p">_</span><span class="n">Height</span><span class="w">
│ │ │ │  </span><span class="ss">name@node</span></code></pre><p>Variables are bound to values using <a href="patterns.xhtml">pattern matching</a>. Erlang uses
│ │ │ │  <em>single assignment</em>, that is, a variable can only be bound once.</p><p>The <em>anonymous variable</em> is denoted by underscore (_) and can be used when a
│ │ │ │  variable is required but its value can be ignored.</p><p><em>Example:</em></p><pre><code class="text">[H|_] = [1,2,3]</code></pre><p>Variables starting with underscore (<code class="inline">_</code>), for example, <code class="inline">_Height</code>, are normal
│ │ │ │  variables, not anonymous. However, they are ignored by the compiler in the sense
│ │ │ │ -that they do not generate warnings.</p><p><em>Example:</em></p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="3491485677-1">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3491485677-2">[</span><span class="p" data-group-id="3491485677-2">]</span><span class="p" data-group-id="3491485677-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3491485677-3">[</span><span class="p" data-group-id="3491485677-3">]</span><span class="p">.</span></code></pre><p>can be rewritten to be more readable:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="9587288443-1">(</span><span class="n">Elem</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9587288443-2">[</span><span class="p" data-group-id="9587288443-2">]</span><span class="p" data-group-id="9587288443-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9587288443-3">[</span><span class="p" data-group-id="9587288443-3">]</span><span class="p">.</span></code></pre><p>This causes a warning for an unused variable, <code class="inline">Elem</code>. To avoid the warning,
│ │ │ │ -the code can be rewritten to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="6147564919-1">(</span><span class="p">_</span><span class="n">Elem</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6147564919-2">[</span><span class="p" data-group-id="6147564919-2">]</span><span class="p" data-group-id="6147564919-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6147564919-3">[</span><span class="p" data-group-id="6147564919-3">]</span><span class="p">.</span></code></pre><p>Notice that since variables starting with an underscore are not anonymous, the
│ │ │ │ -following example matches:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4562290219-1">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4562290219-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4562290219-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4562290219-2">}</span></code></pre><p>But this example fails:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5090711266-1">{</span><span class="p">_</span><span class="n">N</span><span class="p">,</span><span class="p">_</span><span class="n">N</span><span class="p" data-group-id="5090711266-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5090711266-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5090711266-2">}</span></code></pre><p>The scope for a variable is its function clause. Variables bound in a branch of
│ │ │ │ +that they do not generate warnings.</p><p><em>Example:</em></p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="3213316673-1">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3213316673-2">[</span><span class="p" data-group-id="3213316673-2">]</span><span class="p" data-group-id="3213316673-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3213316673-3">[</span><span class="p" data-group-id="3213316673-3">]</span><span class="p">.</span></code></pre><p>can be rewritten to be more readable:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="6660536025-1">(</span><span class="n">Elem</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6660536025-2">[</span><span class="p" data-group-id="6660536025-2">]</span><span class="p" data-group-id="6660536025-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6660536025-3">[</span><span class="p" data-group-id="6660536025-3">]</span><span class="p">.</span></code></pre><p>This causes a warning for an unused variable, <code class="inline">Elem</code>. To avoid the warning,
│ │ │ │ +the code can be rewritten to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="8238280613-1">(</span><span class="p">_</span><span class="n">Elem</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8238280613-2">[</span><span class="p" data-group-id="8238280613-2">]</span><span class="p" data-group-id="8238280613-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8238280613-3">[</span><span class="p" data-group-id="8238280613-3">]</span><span class="p">.</span></code></pre><p>Notice that since variables starting with an underscore are not anonymous, the
│ │ │ │ +following example matches:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1032307999-1">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1032307999-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1032307999-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1032307999-2">}</span></code></pre><p>But this example fails:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7330804101-1">{</span><span class="p">_</span><span class="n">N</span><span class="p">,</span><span class="p">_</span><span class="n">N</span><span class="p" data-group-id="7330804101-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7330804101-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7330804101-2">}</span></code></pre><p>The scope for a variable is its function clause. Variables bound in a branch of
│ │ │ │  an <code class="inline">if</code>, <code class="inline">case</code>, or <code class="inline">receive</code> expression must be bound in all branches to have a
│ │ │ │  value outside the expression. Otherwise they are regarded as unsafe outside
│ │ │ │  the expression.</p><p>For the <code class="inline">try</code> expression, variable scoping is limited so that variables bound in
│ │ │ │  the expression are always unsafe outside the expression.</p><h2 id="patterns" class="section-heading">
│ │ │ │    <a href="#patterns" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Patterns</span>
│ │ │ │  </h2>
│ │ │ │  <p>A pattern has the same structure as a term but can contain unbound variables.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">Name1</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2915498450-1">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2915498450-1">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2915498450-2">{</span><span class="ss">error</span><span class="p">,</span><span class="n">Reason</span><span class="p" data-group-id="2915498450-2">}</span></code></pre><p>Patterns are allowed in clause heads, <a href="expressions.xhtml#case">case expressions</a>,
│ │ │ │ +</span><span class="p" data-group-id="1352718544-1">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1352718544-1">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1352718544-2">{</span><span class="ss">error</span><span class="p">,</span><span class="n">Reason</span><span class="p" data-group-id="1352718544-2">}</span></code></pre><p>Patterns are allowed in clause heads, <a href="expressions.xhtml#case">case expressions</a>,
│ │ │ │  <a href="expressions.xhtml#receive">receive expressions</a>, and
│ │ │ │  <a href="expressions.xhtml#the-match-operator">match expressions</a>.</p><h3 id="the-compound-pattern-operator" class="section-heading">
│ │ │ │    <a href="#the-compound-pattern-operator" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">The Compound Pattern Operator</span>
│ │ │ │  </h3>
│ │ │ │  <p>If <code class="inline">Pattern1</code> and <code class="inline">Pattern2</code> are valid patterns, the following is also a valid
│ │ │ │  pattern:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Pattern2</span></code></pre><p>When matched against a term, both <code class="inline">Pattern1</code> and <code class="inline">Pattern2</code> are matched against
│ │ │ │ -the term. The idea behind this feature is to avoid reconstruction of terms.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="9247277560-1">(</span><span class="p" data-group-id="9247277560-2">{</span><span class="ss">connect</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="n">Number</span><span class="p">,</span><span class="n">Options</span><span class="p" data-group-id="9247277560-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="9247277560-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Signal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9247277560-3">{</span><span class="ss">connect</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="n">Number</span><span class="p">,</span><span class="n">Options</span><span class="p" data-group-id="9247277560-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +the term. The idea behind this feature is to avoid reconstruction of terms.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="4189145878-1">(</span><span class="p" data-group-id="4189145878-2">{</span><span class="ss">connect</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="n">Number</span><span class="p">,</span><span class="n">Options</span><span class="p" data-group-id="4189145878-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="4189145878-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Signal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4189145878-3">{</span><span class="ss">connect</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="n">Number</span><span class="p">,</span><span class="n">Options</span><span class="p" data-group-id="4189145878-3">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="9247277560-4">(</span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="9247277560-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ignore</span><span class="p">.</span></code></pre><p>can instead be written as</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="3822180869-1">(</span><span class="p" data-group-id="3822180869-2">{</span><span class="ss">connect</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="3822180869-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="3822180869-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="4189145878-4">(</span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="4189145878-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ignore</span><span class="p">.</span></code></pre><p>can instead be written as</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="6578207280-1">(</span><span class="p" data-group-id="6578207280-2">{</span><span class="ss">connect</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6578207280-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="6578207280-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="3822180869-3">(</span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="3822180869-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="6578207280-3">(</span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="6578207280-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">ignore</span><span class="p">.</span></code></pre><p>The compound pattern operator does not imply that its operands are matched in
│ │ │ │  any particular order. That means that it is not legal to bind a variable in
│ │ │ │  <code class="inline">Pattern1</code> and use it in <code class="inline">Pattern2</code>, or vice versa.</p><h3 id="string-prefix-in-patterns" class="section-heading">
│ │ │ │    <a href="#string-prefix-in-patterns" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">String Prefix in Patterns</span>
│ │ │ │  </h3>
│ │ │ │ -<p>When matching strings, the following is a valid pattern:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="3501104362-1">(</span><span class="s">&quot;prefix&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Str</span><span class="p" data-group-id="3501104362-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>This is syntactic sugar for the equivalent, but harder to read:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="4877619259-1">(</span><span class="p" data-group-id="4877619259-2">[</span><span class="sc">$p</span><span class="p">,</span><span class="sc">$r</span><span class="p">,</span><span class="sc">$e</span><span class="p">,</span><span class="sc">$f</span><span class="p">,</span><span class="sc">$i</span><span class="p">,</span><span class="sc">$x</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Str</span><span class="p" data-group-id="4877619259-2">]</span><span class="p" data-group-id="4877619259-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h3 id="expressions-in-patterns" class="section-heading">
│ │ │ │ +<p>When matching strings, the following is a valid pattern:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="1217994678-1">(</span><span class="s">&quot;prefix&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Str</span><span class="p" data-group-id="1217994678-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>This is syntactic sugar for the equivalent, but harder to read:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="9070903799-1">(</span><span class="p" data-group-id="9070903799-2">[</span><span class="sc">$p</span><span class="p">,</span><span class="sc">$r</span><span class="p">,</span><span class="sc">$e</span><span class="p">,</span><span class="sc">$f</span><span class="p">,</span><span class="sc">$i</span><span class="p">,</span><span class="sc">$x</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Str</span><span class="p" data-group-id="9070903799-2">]</span><span class="p" data-group-id="9070903799-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h3 id="expressions-in-patterns" class="section-heading">
│ │ │ │    <a href="#expressions-in-patterns" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Expressions in Patterns</span>
│ │ │ │  </h3>
│ │ │ │  <p>An arithmetic expression can be used within a pattern if it meets both of the
│ │ │ │ -following two conditions:</p><ul><li>It uses only numeric or bitwise operators.</li><li>Its value can be evaluated to a constant when compiled.</li></ul><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="p" data-group-id="0246091785-1">{</span><span class="n">Value</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0246091785-1">}</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0246091785-2">{</span><span class="o">?</span><span class="n">THRESHOLD</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="0246091785-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="the-match-operator" class="section-heading">
│ │ │ │ +following two conditions:</p><ul><li>It uses only numeric or bitwise operators.</li><li>Its value can be evaluated to a constant when compiled.</li></ul><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="p" data-group-id="2747185092-1">{</span><span class="n">Value</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="2747185092-1">}</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2747185092-2">{</span><span class="o">?</span><span class="n">THRESHOLD</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="2747185092-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="the-match-operator" class="section-heading">
│ │ │ │    <a href="#the-match-operator" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">The Match Operator</span>
│ │ │ │  </h2>
│ │ │ │  <p>The following matches <code class="inline">Pattern</code> against <code class="inline">Expr</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expr</span></code></pre><p>If the matching succeeds, any unbound variable in the pattern becomes bound and
│ │ │ │  the value of <code class="inline">Expr</code> is returned.</p><p>If multiple match operators are applied in sequence, they will be evaluated from
│ │ │ │ -right to left.</p><p>If the matching fails, a <code class="inline">badmatch</code> run-time error occurs.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="0410472684-1">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0410472684-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0410472684-2">{</span><span class="ss">answer</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="0410472684-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0410472684-3">{</span><span class="ss">answer</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="0410472684-3">}</span><span class="w">
│ │ │ │ +right to left.</p><p>If the matching fails, a <code class="inline">badmatch</code> run-time error occurs.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="2305310084-1">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="2305310084-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2305310084-2">{</span><span class="ss">answer</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="2305310084-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2305310084-3">{</span><span class="ss">answer</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="2305310084-3">}</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">2&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">answer</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">3&gt; </span><span class="n">B</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">42</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">4&gt; </span><span class="n">T</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0410472684-4">{</span><span class="ss">answer</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="0410472684-4">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="0410472684-5">{</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="0410472684-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0410472684-6">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0410472684-6">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2305310084-4">{</span><span class="ss">answer</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="2305310084-4">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="2305310084-5">{</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="2305310084-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2305310084-6">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="2305310084-6">]</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no match of right-hand side value [1,2]</span></code></pre><p>Because multiple match operators are evaluated from right to left, it means
│ │ │ │  that:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Pattern2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">PatternN</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expression</span></code></pre><p>is equivalent to:</p><pre><code class="makeup erlang" translate="no"><span class="n">Temporary</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expression</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="n">PatternN</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Temporary</span><span class="p">,</span><span class="w">
│ │ │ │     </span><span class="p">.</span><span class="w">
│ │ │ │     </span><span class="p">.</span><span class="w">
│ │ │ │     </span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="n">Pattern2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Temporary</span><span class="p">,</span><span class="w">
│ │ │ │ @@ -144,30 +144,30 @@
│ │ │ │  can safely be skipped on a first reading.</p></section><p>The <code class="inline">=</code> character is used to denote two similar but distinct operators: the
│ │ │ │  match operator and the compound pattern operator. Which one is meant is
│ │ │ │  determined by context.</p><p>The <em>compound pattern operator</em> is used to construct a compound pattern from two
│ │ │ │  patterns. Compound patterns are accepted everywhere a pattern is accepted. A
│ │ │ │  compound pattern matches if all of its constituent patterns match. It is not
│ │ │ │  legal for a pattern that is part of a compound pattern to use variables (as keys
│ │ │ │  in map patterns or sizes in binary patterns) bound in other sub patterns of the
│ │ │ │ -same compound pattern.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">fun</span><span class="p" data-group-id="2225589475-1">(</span><span class="p" data-group-id="2225589475-2">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="2225589475-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2225589475-3">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="2225589475-3">}</span><span class="p" data-group-id="2225589475-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Value</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +same compound pattern.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">fun</span><span class="p" data-group-id="8603937272-1">(</span><span class="p" data-group-id="8603937272-2">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="8603937272-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8603937272-3">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="8603937272-3">}</span><span class="p" data-group-id="8603937272-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Value</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">* 1:7: variable &#39;Key&#39; is unbound</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="2225589475-4">(</span><span class="p" data-group-id="2225589475-5">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="2225589475-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">E</span><span class="p" data-group-id="2225589475-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2225589475-6">{</span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="2225589475-6">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="2225589475-7">(</span><span class="p" data-group-id="2225589475-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2225589475-8">}</span><span class="p" data-group-id="2225589475-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2225589475-9">{</span><span class="p" data-group-id="2225589475-10">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2225589475-10">}</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2225589475-9">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="n">G</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="2225589475-11">(</span><span class="p" data-group-id="2225589475-12">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">B</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="2225589475-12">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2225589475-13">&lt;&lt;</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="2225589475-13">&gt;&gt;</span><span class="p" data-group-id="2225589475-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2225589475-14">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="2225589475-14">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">G</span><span class="p" data-group-id="2225589475-15">(</span><span class="p" data-group-id="2225589475-16">&lt;&lt;</span><span class="mi">42</span><span class="p">,</span><span class="mi">43</span><span class="p" data-group-id="2225589475-16">&gt;&gt;</span><span class="p" data-group-id="2225589475-15">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2225589475-17">{</span><span class="mi">42</span><span class="p">,</span><span class="mi">43</span><span class="p">,</span><span class="mi">10795</span><span class="p" data-group-id="2225589475-17">}</span></code></pre><p>The <em>match operator</em> is allowed everywhere an expression is allowed. It is used
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="8603937272-4">(</span><span class="p" data-group-id="8603937272-5">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="8603937272-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">E</span><span class="p" data-group-id="8603937272-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8603937272-6">{</span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="8603937272-6">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="8603937272-7">(</span><span class="p" data-group-id="8603937272-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8603937272-8">}</span><span class="p" data-group-id="8603937272-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8603937272-9">{</span><span class="p" data-group-id="8603937272-10">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8603937272-10">}</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8603937272-9">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="n">G</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="8603937272-11">(</span><span class="p" data-group-id="8603937272-12">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">B</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="8603937272-12">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8603937272-13">&lt;&lt;</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="8603937272-13">&gt;&gt;</span><span class="p" data-group-id="8603937272-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8603937272-14">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="8603937272-14">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">G</span><span class="p" data-group-id="8603937272-15">(</span><span class="p" data-group-id="8603937272-16">&lt;&lt;</span><span class="mi">42</span><span class="p">,</span><span class="mi">43</span><span class="p" data-group-id="8603937272-16">&gt;&gt;</span><span class="p" data-group-id="8603937272-15">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8603937272-17">{</span><span class="mi">42</span><span class="p">,</span><span class="mi">43</span><span class="p">,</span><span class="mi">10795</span><span class="p" data-group-id="8603937272-17">}</span></code></pre><p>The <em>match operator</em> is allowed everywhere an expression is allowed. It is used
│ │ │ │  to match the value of an expression to a pattern. If multiple match operators
│ │ │ │ -are applied in sequence, they will be evaluated from right to left.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6807646530-1">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">key2</span><span class="p">,</span><span class="w"> </span><span class="ss">key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="6807646530-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6807646530-2">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">key2</span><span class="p">,</span><span class="ss">key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="6807646530-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">f</span><span class="p" data-group-id="6807646530-3">(</span><span class="n">Key</span><span class="p" data-group-id="6807646530-3">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6807646530-4">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="6807646530-4">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6807646530-5">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="6807646530-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ │ +are applied in sequence, they will be evaluated from right to left.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1111895279-1">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">key2</span><span class="p">,</span><span class="w"> </span><span class="ss">key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="1111895279-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1111895279-2">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">key2</span><span class="p">,</span><span class="ss">key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="1111895279-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">f</span><span class="p" data-group-id="1111895279-3">(</span><span class="n">Key</span><span class="p" data-group-id="1111895279-3">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1111895279-4">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="1111895279-4">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1111895279-5">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="1111895279-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">value</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">f</span><span class="p" data-group-id="6807646530-6">(</span><span class="n">Key</span><span class="p" data-group-id="6807646530-6">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6807646530-7">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="6807646530-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6807646530-8">(</span><span class="p" data-group-id="6807646530-9">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="6807646530-9">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p" data-group-id="6807646530-8">)</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">f</span><span class="p" data-group-id="1111895279-6">(</span><span class="n">Key</span><span class="p" data-group-id="1111895279-6">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1111895279-7">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="1111895279-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1111895279-8">(</span><span class="p" data-group-id="1111895279-9">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="1111895279-9">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p" data-group-id="1111895279-8">)</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">value</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nf">f</span><span class="p" data-group-id="6807646530-10">(</span><span class="n">Key</span><span class="p" data-group-id="6807646530-10">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6807646530-11">(</span><span class="p" data-group-id="6807646530-12">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="6807646530-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6807646530-13">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="6807646530-13">}</span><span class="p" data-group-id="6807646530-11">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nf">f</span><span class="p" data-group-id="1111895279-10">(</span><span class="n">Key</span><span class="p" data-group-id="1111895279-10">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1111895279-11">(</span><span class="p" data-group-id="1111895279-12">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="1111895279-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1111895279-13">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="1111895279-13">}</span><span class="p" data-group-id="1111895279-11">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">* 1:12: variable &#39;Key&#39; is unbound</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="6807646530-14">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">Y</span><span class="p" data-group-id="6807646530-14">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">begin</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6807646530-15">&lt;&lt;</span><span class="mi">42</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="6807646530-15">&gt;&gt;</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="1111895279-14">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">Y</span><span class="p" data-group-id="1111895279-14">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">begin</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1111895279-15">&lt;&lt;</span><span class="mi">42</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="1111895279-15">&gt;&gt;</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">42</span></code></pre><p>The expression at prompt <code class="inline">2&gt;</code> first matches the value of variable <code class="inline">M</code> against
│ │ │ │  pattern <code class="inline">#{key := Key}</code>, binding variable <code class="inline">Key</code>. It then matches the value of
│ │ │ │  <code class="inline">M</code> against pattern <code class="inline">#{Key := Value}</code> using variable <code class="inline">Key</code> as the key, binding
│ │ │ │  variable <code class="inline">Value</code>.</p><p>The expression at prompt <code class="inline">3&gt;</code> matches expression <code class="inline">(#{key := Key} = M)</code> against
│ │ │ │  pattern <code class="inline">#{Key := Value}</code>. The expression inside the parentheses is evaluated
│ │ │ │  first. That is, <code class="inline">M</code> is matched against <code class="inline">#{key := Key}</code>, and then the value of
│ │ │ │  <code class="inline">M</code> is matched against pattern <code class="inline">#{Key := Value}</code>. That is the same evaluation
│ │ │ │ @@ -181,30 +181,30 @@
│ │ │ │  binding variable <code class="inline">Y</code> and creating a binary. The binary is then matched against
│ │ │ │  pattern <code class="inline">&lt;&lt;X:Y&gt;&gt;</code> using the value of <code class="inline">Y</code> as the size of the segment.</p><h2 id="function-calls" class="section-heading">
│ │ │ │    <a href="#function-calls" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Function Calls</span>
│ │ │ │  </h2>
│ │ │ │ -<pre><code class="makeup erlang" translate="no"><span class="n">ExprM</span><span class="p">:</span><span class="n">ExprF</span><span class="p" data-group-id="4918339280-1">(</span><span class="n">Expr1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ExprN</span><span class="p" data-group-id="4918339280-1">)</span><span class="w">
│ │ │ │ -</span><span class="n">ExprF</span><span class="p" data-group-id="4918339280-2">(</span><span class="n">Expr1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ExprN</span><span class="p" data-group-id="4918339280-2">)</span></code></pre><p>In the first form of function calls, <code class="inline">ExprM:ExprF(Expr1,...,ExprN)</code>, each of
│ │ │ │ +<pre><code class="makeup erlang" translate="no"><span class="n">ExprM</span><span class="p">:</span><span class="n">ExprF</span><span class="p" data-group-id="6458456122-1">(</span><span class="n">Expr1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ExprN</span><span class="p" data-group-id="6458456122-1">)</span><span class="w">
│ │ │ │ +</span><span class="n">ExprF</span><span class="p" data-group-id="6458456122-2">(</span><span class="n">Expr1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ExprN</span><span class="p" data-group-id="6458456122-2">)</span></code></pre><p>In the first form of function calls, <code class="inline">ExprM:ExprF(Expr1,...,ExprN)</code>, each of
│ │ │ │  <code class="inline">ExprM</code> and <code class="inline">ExprF</code> must be an atom or an expression that evaluates to an atom.
│ │ │ │  The function is said to be called by using the <em>fully qualified function name</em>.
│ │ │ │ -This is often referred to as a <em>remote</em> or <em>external function call</em>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="5907005207-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="5907005207-1">)</span></code></pre><p>In the second form of function calls, <code class="inline">ExprF(Expr1,...,ExprN)</code>, <code class="inline">ExprF</code> must be
│ │ │ │ +This is often referred to as a <em>remote</em> or <em>external function call</em>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="6817026381-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="6817026381-1">)</span></code></pre><p>In the second form of function calls, <code class="inline">ExprF(Expr1,...,ExprN)</code>, <code class="inline">ExprF</code> must be
│ │ │ │  an atom or evaluate to a fun.</p><p>If <code class="inline">ExprF</code> is an atom, the function is said to be called by using the
│ │ │ │  <em>implicitly qualified function name</em>. If the function <code class="inline">ExprF</code> is locally
│ │ │ │  defined, it is called. Alternatively, if <code class="inline">ExprF</code> is explicitly imported from the
│ │ │ │  <code class="inline">M</code> module, <code class="inline">M:ExprF(Expr1,...,ExprN)</code> is called. If <code class="inline">ExprF</code> is neither declared
│ │ │ │  locally nor explicitly imported, <code class="inline">ExprF</code> must be the name of an automatically
│ │ │ │ -imported BIF.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle</span><span class="p" data-group-id="0243121003-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0243121003-1">)</span><span class="w">
│ │ │ │ -</span><span class="nf">spawn</span><span class="p" data-group-id="0243121003-2">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0243121003-3">[</span><span class="p" data-group-id="0243121003-3">]</span><span class="p" data-group-id="0243121003-2">)</span></code></pre><p><em>Examples</em> where <code class="inline">ExprF</code> is a fun:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="9869027030-1">(</span><span class="n">X</span><span class="p" data-group-id="9869027030-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Fun1</span><span class="p" data-group-id="9869027030-2">(</span><span class="mi">3</span><span class="p" data-group-id="9869027030-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +imported BIF.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle</span><span class="p" data-group-id="8898315290-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8898315290-1">)</span><span class="w">
│ │ │ │ +</span><span class="nf">spawn</span><span class="p" data-group-id="8898315290-2">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8898315290-3">[</span><span class="p" data-group-id="8898315290-3">]</span><span class="p" data-group-id="8898315290-2">)</span></code></pre><p><em>Examples</em> where <code class="inline">ExprF</code> is a fun:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="9721978994-1">(</span><span class="n">X</span><span class="p" data-group-id="9721978994-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Fun1</span><span class="p" data-group-id="9721978994-2">(</span><span class="mi">3</span><span class="p" data-group-id="9721978994-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="k">fun</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="ss">append</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9869027030-3">(</span><span class="p" data-group-id="9869027030-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9869027030-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9869027030-5">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9869027030-5">]</span><span class="p" data-group-id="9869027030-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9869027030-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9869027030-6">]</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="k">fun</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="ss">append</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9721978994-3">(</span><span class="p" data-group-id="9721978994-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9721978994-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9721978994-5">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9721978994-5">]</span><span class="p" data-group-id="9721978994-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9721978994-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9721978994-6">]</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="o">&gt;</span></code></pre><p>Notice that when calling a local function, there is a difference between using
│ │ │ │  the implicitly or fully qualified function name. The latter always refers to the
│ │ │ │  latest version of the module. See
│ │ │ │  <a href="code_loading.xhtml">Compilation and Code Loading</a> and
│ │ │ │  <a href="ref_man_functions.xhtml#eval">Function Evaluation</a>.</p><h3 id="local-function-names-clashing-with-auto-imported-bifs" class="section-heading">
│ │ │ │    <a href="#local-function-names-clashing-with-auto-imported-bifs" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │ @@ -221,40 +221,40 @@
│ │ │ │  called instead. This is to avoid that future additions to the set of
│ │ │ │  auto-imported BIFs silently change the behavior of old code.</p></section><p>However, to avoid old (pre R14) code changing its behavior when compiled
│ │ │ │  with Erlang/OTP version R14A or later, the following restriction applies: If you
│ │ │ │  override the name of a BIF that was auto-imported in OTP versions prior to R14A
│ │ │ │  (ERTS version 5.8) and have an implicitly qualified call to that function in
│ │ │ │  your code, you either need to explicitly remove the auto-import using a compiler
│ │ │ │  directive, or replace the call with a fully qualified function call. Otherwise
│ │ │ │ -you get a compilation error. See the following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1499083439-1">(</span><span class="p" data-group-id="1499083439-2">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">f</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1499083439-2">]</span><span class="p" data-group-id="1499083439-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +you get a compilation error. See the following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7437102323-1">(</span><span class="p" data-group-id="7437102323-2">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">f</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7437102323-2">]</span><span class="p" data-group-id="7437102323-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="1499083439-3">(</span><span class="p" data-group-id="1499083439-4">{</span><span class="ss">no_auto_import</span><span class="p">,</span><span class="p" data-group-id="1499083439-5">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1499083439-5">]</span><span class="p" data-group-id="1499083439-4">}</span><span class="p" data-group-id="1499083439-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% erlang:length/1 no longer autoimported</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="7437102323-3">(</span><span class="p" data-group-id="7437102323-4">{</span><span class="ss">no_auto_import</span><span class="p">,</span><span class="p" data-group-id="7437102323-5">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7437102323-5">]</span><span class="p" data-group-id="7437102323-4">}</span><span class="p" data-group-id="7437102323-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% erlang:length/1 no longer autoimported</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">length</span><span class="p" data-group-id="1499083439-6">(</span><span class="p" data-group-id="1499083439-7">[</span><span class="p" data-group-id="1499083439-7">]</span><span class="p" data-group-id="1499083439-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">length</span><span class="p" data-group-id="7437102323-6">(</span><span class="p" data-group-id="7437102323-7">[</span><span class="p" data-group-id="7437102323-7">]</span><span class="p" data-group-id="7437102323-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="mi">0</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">length</span><span class="p" data-group-id="1499083439-8">(</span><span class="p" data-group-id="1499083439-9">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1499083439-9">]</span><span class="p" data-group-id="1499083439-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="1499083439-10">(</span><span class="n">T</span><span class="p" data-group-id="1499083439-10">)</span><span class="p">.</span><span class="w"> </span><span class="c1">%% Calls the local function length/1</span><span class="w">
│ │ │ │ +</span><span class="nf">length</span><span class="p" data-group-id="7437102323-8">(</span><span class="p" data-group-id="7437102323-9">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7437102323-9">]</span><span class="p" data-group-id="7437102323-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="7437102323-10">(</span><span class="n">T</span><span class="p" data-group-id="7437102323-10">)</span><span class="p">.</span><span class="w"> </span><span class="c1">%% Calls the local function length/1</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="1499083439-11">(</span><span class="n">X</span><span class="p" data-group-id="1499083439-11">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="1499083439-12">(</span><span class="n">X</span><span class="p" data-group-id="1499083439-12">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">%% Calls erlang:length/1,</span><span class="w">
│ │ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="7437102323-11">(</span><span class="n">X</span><span class="p" data-group-id="7437102323-11">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="7437102323-12">(</span><span class="n">X</span><span class="p" data-group-id="7437102323-12">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">%% Calls erlang:length/1,</span><span class="w">
│ │ │ │                                    </span><span class="c1">%% which is allowed in guards</span><span class="w">
│ │ │ │      </span><span class="ss">long</span><span class="p">.</span></code></pre><p>The same logic applies to explicitly imported functions from other modules, as
│ │ │ │  to locally defined functions. It is not allowed to both import a function from
│ │ │ │ -another module and have the function declared in the module at the same time:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6102488438-1">(</span><span class="p" data-group-id="6102488438-2">[</span><span class="ss">f</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6102488438-2">]</span><span class="p" data-group-id="6102488438-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +another module and have the function declared in the module at the same time:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3907657136-1">(</span><span class="p" data-group-id="3907657136-2">[</span><span class="ss">f</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3907657136-2">]</span><span class="p" data-group-id="3907657136-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="6102488438-3">(</span><span class="p" data-group-id="6102488438-4">{</span><span class="ss">no_auto_import</span><span class="p">,</span><span class="p" data-group-id="6102488438-5">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6102488438-5">]</span><span class="p" data-group-id="6102488438-4">}</span><span class="p" data-group-id="6102488438-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% erlang:length/1 no longer autoimported</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="3907657136-3">(</span><span class="p" data-group-id="3907657136-4">{</span><span class="ss">no_auto_import</span><span class="p">,</span><span class="p" data-group-id="3907657136-5">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3907657136-5">]</span><span class="p" data-group-id="3907657136-4">}</span><span class="p" data-group-id="3907657136-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% erlang:length/1 no longer autoimported</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">import</span><span class="p" data-group-id="6102488438-6">(</span><span class="ss">mod</span><span class="p">,</span><span class="p" data-group-id="6102488438-7">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6102488438-7">]</span><span class="p" data-group-id="6102488438-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">import</span><span class="p" data-group-id="3907657136-6">(</span><span class="ss">mod</span><span class="p">,</span><span class="p" data-group-id="3907657136-7">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3907657136-7">]</span><span class="p" data-group-id="3907657136-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="6102488438-8">(</span><span class="n">X</span><span class="p" data-group-id="6102488438-8">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="6102488438-9">(</span><span class="n">X</span><span class="p" data-group-id="6102488438-9">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">33</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">%% Calls erlang:length/1,</span><span class="w">
│ │ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="3907657136-8">(</span><span class="n">X</span><span class="p" data-group-id="3907657136-8">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="3907657136-9">(</span><span class="n">X</span><span class="p" data-group-id="3907657136-9">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">33</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">%% Calls erlang:length/1,</span><span class="w">
│ │ │ │                                     </span><span class="c1">%% which is allowed in guards</span><span class="w">
│ │ │ │  
│ │ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="6102488438-10">(</span><span class="n">X</span><span class="p" data-group-id="6102488438-10">)</span><span class="p">;</span><span class="w">              </span><span class="c1">%% Explicit call to erlang:length in body</span><span class="w">
│ │ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="3907657136-10">(</span><span class="n">X</span><span class="p" data-group-id="3907657136-10">)</span><span class="p">;</span><span class="w">              </span><span class="c1">%% Explicit call to erlang:length in body</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="6102488438-11">(</span><span class="n">X</span><span class="p" data-group-id="6102488438-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">length</span><span class="p" data-group-id="6102488438-12">(</span><span class="n">X</span><span class="p" data-group-id="6102488438-12">)</span><span class="p">.</span><span class="w">                     </span><span class="c1">%% mod:length/1 is called</span></code></pre><p>For auto-imported BIFs added in Erlang/OTP R14A and thereafter, overriding the
│ │ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="3907657136-11">(</span><span class="n">X</span><span class="p" data-group-id="3907657136-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">length</span><span class="p" data-group-id="3907657136-12">(</span><span class="n">X</span><span class="p" data-group-id="3907657136-12">)</span><span class="p">.</span><span class="w">                     </span><span class="c1">%% mod:length/1 is called</span></code></pre><p>For auto-imported BIFs added in Erlang/OTP R14A and thereafter, overriding the
│ │ │ │  name with a local function or explicit import is always allowed. However, if the
│ │ │ │  <code class="inline">-compile({no_auto_import,[F/A]})</code> directive is not used, the compiler issues a
│ │ │ │  warning whenever the function is called in the module using the implicitly
│ │ │ │  qualified function name.</p><h2 id="if" class="section-heading">
│ │ │ │    <a href="#if" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │ @@ -266,40 +266,40 @@
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="n">GuardSeqN</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>The branches of an <code class="inline">if</code>-expression are scanned sequentially until a guard
│ │ │ │  sequence <code class="inline">GuardSeq</code> that evaluates to true is found. Then the corresponding
│ │ │ │  <code class="inline">Body</code> (a sequence of expressions separated by <code class="inline">,</code>) is evaluated.</p><p>The return value of <code class="inline">Body</code> is the return value of the <code class="inline">if</code> expression.</p><p>If no guard sequence is evaluated as true, an <code class="inline">if_clause</code> run-time error occurs.
│ │ │ │  If necessary, the guard expression <code class="inline">true</code> can be used in the last branch, as
│ │ │ │ -that guard sequence is always true.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_greater_than</span><span class="p" data-group-id="2493012059-1">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2493012059-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +that guard sequence is always true.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_greater_than</span><span class="p" data-group-id="5222605093-1">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5222605093-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% works as an &#39;else&#39; branch</span><span class="w">
│ │ │ │              </span><span class="ss">false</span><span class="w">
│ │ │ │      </span><span class="k">end</span></code></pre><h2 id="case" class="section-heading">
│ │ │ │    <a href="#case" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Case</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="n">Expr</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="6084994069-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="6084994069-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="1618920723-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="1618920723-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="6084994069-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="6084994069-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="1618920723-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="1618920723-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>The expression <code class="inline">Expr</code> is evaluated and the patterns <code class="inline">Pattern</code> are sequentially
│ │ │ │  matched against the result. If a match succeeds and the optional guard sequence
│ │ │ │  <code class="inline">GuardSeq</code> is true, the corresponding <code class="inline">Body</code> is evaluated.</p><p>The return value of <code class="inline">Body</code> is the return value of the <code class="inline">case</code> expression.</p><p>If there is no matching pattern with a true guard sequence, a <code class="inline">case_clause</code>
│ │ │ │ -run-time error occurs.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_valid_signal</span><span class="p" data-group-id="7982151371-1">(</span><span class="n">Signal</span><span class="p" data-group-id="7982151371-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +run-time error occurs.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_valid_signal</span><span class="p" data-group-id="5433265432-1">(</span><span class="n">Signal</span><span class="p" data-group-id="5433265432-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Signal</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="7982151371-2">{</span><span class="ss">signal</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">To</span><span class="p" data-group-id="7982151371-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="5433265432-2">{</span><span class="ss">signal</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">To</span><span class="p" data-group-id="5433265432-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="7982151371-3">{</span><span class="ss">signal</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">To</span><span class="p" data-group-id="7982151371-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="5433265432-3">{</span><span class="ss">signal</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">To</span><span class="p" data-group-id="5433265432-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="p">_</span><span class="n">Else</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">false</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><h2 id="maybe" class="section-heading">
│ │ │ │    <a href="#maybe" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │ @@ -317,57 +317,57 @@
│ │ │ │  the top-level of a <code class="inline">maybe</code> block. It matches the pattern <code class="inline">Expr1</code> against
│ │ │ │  <code class="inline">Expr2</code>. If the matching succeeds, any unbound variable in the pattern becomes
│ │ │ │  bound. If the expression is the last expression in the <code class="inline">maybe</code> block, it also
│ │ │ │  returns the value of <code class="inline">Expr2</code>. If the matching is unsuccessful, the rest of the
│ │ │ │  expressions in the <code class="inline">maybe</code> block are skipped and the return value of the <code class="inline">maybe</code>
│ │ │ │  block is <code class="inline">Expr2</code>.</p><p>None of the variables bound in a <code class="inline">maybe</code> block must be used in the code that
│ │ │ │  follows the block.</p><p>Here is an example:</p><pre><code class="makeup erlang" translate="no"><span class="k">maybe</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8038925561-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="8038925561-1">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="8038925561-2">(</span><span class="p" data-group-id="8038925561-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9173402042-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="9173402042-1">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="9173402042-2">(</span><span class="p" data-group-id="9173402042-2">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8038925561-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="8038925561-3">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="8038925561-4">(</span><span class="p" data-group-id="8038925561-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9173402042-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="9173402042-3">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="9173402042-4">(</span><span class="p" data-group-id="9173402042-4">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>Let us first assume that <code class="inline">a()</code> returns <code class="inline">{ok,42}</code> and <code class="inline">b()</code> returns <code class="inline">{ok,58}</code>.
│ │ │ │  With those return values, all of the match operators will succeed, and the
│ │ │ │  return value of the <code class="inline">maybe</code> block is <code class="inline">A + B</code>, which is equal to <code class="inline">42 + 58 = 100</code>.</p><p>Now let us assume that <code class="inline">a()</code> returns <code class="inline">error</code>. The conditional match operator in
│ │ │ │  <code class="inline">{ok, A} ?= a()</code> fails to match, and the return value of the <code class="inline">maybe</code> block is
│ │ │ │  the value of the expression that failed to match, namely <code class="inline">error</code>. Similarly, if
│ │ │ │  <code class="inline">b()</code> returns <code class="inline">wrong</code>, the return value of the <code class="inline">maybe</code> block is <code class="inline">wrong</code>.</p><p>Finally, let us assume that <code class="inline">a()</code> returns <code class="inline">{ok,-1}</code>. Because <code class="inline">true = A &gt;= 0</code> uses
│ │ │ │  the match operator <code class="inline">=</code>, a <code class="inline">{badmatch,false}</code> run-time error occurs when the
│ │ │ │ -expression fails to match the pattern.</p><p>The example can be written in a less succinct way using nested case expressions:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="5777251329-1">(</span><span class="p" data-group-id="5777251329-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5777251329-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="5777251329-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +expression fails to match the pattern.</p><p>The example can be written in a less succinct way using nested case expressions:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="0625864335-1">(</span><span class="p" data-group-id="0625864335-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0625864335-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="0625864335-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="k">case</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="5777251329-3">(</span><span class="p" data-group-id="5777251329-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="5777251329-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="5777251329-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="k">case</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="0625864335-3">(</span><span class="p" data-group-id="0625864335-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="0625864335-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0625864335-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                  </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p">;</span><span class="w">
│ │ │ │              </span><span class="n">Other1</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                  </span><span class="n">Other1</span><span class="w">
│ │ │ │          </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="n">Other2</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">Other2</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>The <code class="inline">maybe</code> block can be augmented with <code class="inline">else</code> clauses:</p><pre><code class="makeup erlang" translate="no"><span class="k">maybe</span><span class="w">
│ │ │ │      </span><span class="n">Expr1</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="n">ExprN</span><span class="w">
│ │ │ │  </span><span class="k">else</span><span class="w">
│ │ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="3897903534-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="3897903534-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="2646278257-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="2646278257-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="3897903534-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="3897903534-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="2646278257-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="2646278257-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>If a conditional match operator fails, the failed expression is matched against
│ │ │ │  the patterns in all clauses between the <code class="inline">else</code> and <code class="inline">end</code> keywords. If a match
│ │ │ │  succeeds and the optional guard sequence <code class="inline">GuardSeq</code> is true, the corresponding
│ │ │ │  <code class="inline">Body</code> is evaluated. The value returned from the body is the return value of the
│ │ │ │  <code class="inline">maybe</code> block.</p><p>If there is no matching pattern with a true guard sequence, an <code class="inline">else_clause</code>
│ │ │ │  run-time error occurs.</p><p>None of the variables bound in a <code class="inline">maybe</code> block must be used in the <code class="inline">else</code>
│ │ │ │  clauses. None of the variables bound in the <code class="inline">else</code> clauses must be used in the
│ │ │ │  code that follows the <code class="inline">maybe</code> block.</p><p>Here is the previous example augmented with <code class="inline">else</code> clauses:</p><pre><code class="makeup erlang" translate="no"><span class="k">maybe</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0897901502-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="0897901502-1">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="0897901502-2">(</span><span class="p" data-group-id="0897901502-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3123158866-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="3123158866-1">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="3123158866-2">(</span><span class="p" data-group-id="3123158866-2">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0897901502-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0897901502-3">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="0897901502-4">(</span><span class="p" data-group-id="0897901502-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3123158866-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="3123158866-3">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="3123158866-4">(</span><span class="p" data-group-id="3123158866-4">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="w">
│ │ │ │  </span><span class="k">else</span><span class="w">
│ │ │ │      </span><span class="ss">error</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">error</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="ss">wrong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">error</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>The <code class="inline">else</code> clauses translate the failing value from the conditional match
│ │ │ │  operators to the value <code class="inline">error</code>. If the failing value is not one of the
│ │ │ │  recognized values, an <code class="inline">else_clause</code> run-time error occurs.</p><h2 id="send" class="section-heading">
│ │ │ │ @@ -386,18 +386,18 @@
│ │ │ │  <code class="inline">{Name,Node}</code> (or a pid located at another node), also never fails.</li></ul><h2 id="receive" class="section-heading">
│ │ │ │    <a href="#receive" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Receive</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="0715766294-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="0715766294-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="7817961875-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="7817961875-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="0715766294-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="0715766294-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="7817961875-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="7817961875-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>The <code class="inline">receive</code> expression searches for a message in the message queue that matches
│ │ │ │  one of the patterns in the clauses of the <code class="inline">receive</code> expression. The patterns in
│ │ │ │  the clauses are matched against a message from top to bottom. The first message
│ │ │ │  from the start of the message queue that matches will be selected. Messages are
│ │ │ │  normally
│ │ │ │  <a href="ref_man_processes.xhtml#message-queue-order">enqueued in the message queue</a> in
│ │ │ │ @@ -414,27 +414,27 @@
│ │ │ │  specific messages and the message queue is huge, executing such a <code class="inline">receive</code>
│ │ │ │  expression might become very expensive.</p><p>One type of <code class="inline">receive</code> expressions matching on only specific patterns can,
│ │ │ │  however, be optimized by the compiler and runtime system, namely when
│ │ │ │  you create a <a href="../../../lib/../system/doc/html/data_types.xhtml#reference"><em>reference</em></a> and
│ │ │ │  match on it in all clauses of a <code class="inline">receive</code> expression <em>close</em> to where the
│ │ │ │  reference was created. In this case, only the messages received after
│ │ │ │  the reference was created need to be inspected. For more information see the
│ │ │ │ -<a href="../../../lib/../system/doc/html/eff_guide_processes.xhtml#fetching-received-messages"><em>Fetching Received Messages</em> section of the <em>Efficiency Guide</em></a>.</p></section><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">wait_for_onhook</span><span class="p" data-group-id="9533460456-1">(</span><span class="p" data-group-id="9533460456-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +<a href="../../../lib/../system/doc/html/eff_guide_processes.xhtml#fetching-received-messages"><em>Fetching Received Messages</em> section of the <em>Efficiency Guide</em></a>.</p></section><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">wait_for_onhook</span><span class="p" data-group-id="1715253545-1">(</span><span class="p" data-group-id="1715253545-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">onhook</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">disconnect</span><span class="p" data-group-id="9533460456-2">(</span><span class="p" data-group-id="9533460456-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">idle</span><span class="p" data-group-id="9533460456-3">(</span><span class="p" data-group-id="9533460456-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="9533460456-4">{</span><span class="ss">connect</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="9533460456-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">B</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9533460456-5">{</span><span class="ss">busy</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9533460456-6">(</span><span class="p" data-group-id="9533460456-6">)</span><span class="p" data-group-id="9533460456-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">wait_for_onhook</span><span class="p" data-group-id="9533460456-7">(</span><span class="p" data-group-id="9533460456-7">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">disconnect</span><span class="p" data-group-id="1715253545-2">(</span><span class="p" data-group-id="1715253545-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">idle</span><span class="p" data-group-id="1715253545-3">(</span><span class="p" data-group-id="1715253545-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="1715253545-4">{</span><span class="ss">connect</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="1715253545-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">B</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1715253545-5">{</span><span class="ss">busy</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1715253545-6">(</span><span class="p" data-group-id="1715253545-6">)</span><span class="p" data-group-id="1715253545-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">wait_for_onhook</span><span class="p" data-group-id="1715253545-7">(</span><span class="p" data-group-id="1715253545-7">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">receive</code> expression can be augmented with a timeout:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="9952615309-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="9952615309-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="4873940216-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="4873940216-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="9952615309-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="9952615309-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="4873940216-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="4873940216-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │ │  </span><span class="k">after</span><span class="w">
│ │ │ │      </span><span class="n">ExprT</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyT</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p><code class="inline">receive...after</code> works exactly as <code class="inline">receive</code>, except that if no matching message
│ │ │ │  has arrived within <code class="inline">ExprT</code> milliseconds, then <code class="inline">BodyT</code> is evaluated instead. The
│ │ │ │  return value of <code class="inline">BodyT</code> then becomes the return value of the <code class="inline">receive...after</code>
│ │ │ │ @@ -445,35 +445,35 @@
│ │ │ │  another short timeout) might be cheap since the timeout is short. This is
│ │ │ │  <em>not</em> necessarily the case. If the patterns in the clauses of the <code class="inline">receive</code>
│ │ │ │  expression only match specific messages and no such messages exist in the
│ │ │ │  message queue, the whole message queue needs to be inspected before the
│ │ │ │  timeout can occur. That is, the same caveat as in
│ │ │ │  <a href="#selective-receive-warning">the warning above</a> applies.</p></section><p>The atom <code class="inline">infinity</code> will make the process wait indefinitely for a matching
│ │ │ │  message. This is the same as not using a timeout. It can be useful for timeout
│ │ │ │ -values that are calculated at runtime.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">wait_for_onhook</span><span class="p" data-group-id="6506940042-1">(</span><span class="p" data-group-id="6506940042-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +values that are calculated at runtime.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">wait_for_onhook</span><span class="p" data-group-id="4568329028-1">(</span><span class="p" data-group-id="4568329028-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">onhook</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">disconnect</span><span class="p" data-group-id="6506940042-2">(</span><span class="p" data-group-id="6506940042-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">idle</span><span class="p" data-group-id="6506940042-3">(</span><span class="p" data-group-id="6506940042-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6506940042-4">{</span><span class="ss">connect</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="6506940042-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">B</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6506940042-5">{</span><span class="ss">busy</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6506940042-6">(</span><span class="p" data-group-id="6506940042-6">)</span><span class="p" data-group-id="6506940042-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">wait_for_onhook</span><span class="p" data-group-id="6506940042-7">(</span><span class="p" data-group-id="6506940042-7">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">disconnect</span><span class="p" data-group-id="4568329028-2">(</span><span class="p" data-group-id="4568329028-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">idle</span><span class="p" data-group-id="4568329028-3">(</span><span class="p" data-group-id="4568329028-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="4568329028-4">{</span><span class="ss">connect</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="4568329028-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">B</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4568329028-5">{</span><span class="ss">busy</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4568329028-6">(</span><span class="p" data-group-id="4568329028-6">)</span><span class="p" data-group-id="4568329028-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">wait_for_onhook</span><span class="p" data-group-id="4568329028-7">(</span><span class="p" data-group-id="4568329028-7">)</span><span class="w">
│ │ │ │      </span><span class="k">after</span><span class="w">
│ │ │ │          </span><span class="mi">60000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">disconnect</span><span class="p" data-group-id="6506940042-8">(</span><span class="p" data-group-id="6506940042-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">error</span><span class="p" data-group-id="6506940042-9">(</span><span class="p" data-group-id="6506940042-9">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">disconnect</span><span class="p" data-group-id="4568329028-8">(</span><span class="p" data-group-id="4568329028-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">error</span><span class="p" data-group-id="4568329028-9">(</span><span class="p" data-group-id="4568329028-9">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>It is legal to use a <code class="inline">receive...after</code> expression with no branches:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │  </span><span class="k">after</span><span class="w">
│ │ │ │      </span><span class="n">ExprT</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyT</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>This construction does not consume any messages, only suspends execution in the
│ │ │ │ -process for <code class="inline">ExprT</code> milliseconds. This can be used to implement simple timers.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">timer</span><span class="p" data-group-id="7657266349-1">(</span><span class="p" data-group-id="7657266349-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="7657266349-2">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">timer</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7657266349-3">[</span><span class="nf">self</span><span class="p" data-group-id="7657266349-4">(</span><span class="p" data-group-id="7657266349-4">)</span><span class="p" data-group-id="7657266349-3">]</span><span class="p" data-group-id="7657266349-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +process for <code class="inline">ExprT</code> milliseconds. This can be used to implement simple timers.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">timer</span><span class="p" data-group-id="8785989109-1">(</span><span class="p" data-group-id="8785989109-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="8785989109-2">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">timer</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8785989109-3">[</span><span class="nf">self</span><span class="p" data-group-id="8785989109-4">(</span><span class="p" data-group-id="8785989109-4">)</span><span class="p" data-group-id="8785989109-3">]</span><span class="p" data-group-id="8785989109-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">timer</span><span class="p" data-group-id="7657266349-5">(</span><span class="n">Pid</span><span class="p" data-group-id="7657266349-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">timer</span><span class="p" data-group-id="8785989109-5">(</span><span class="n">Pid</span><span class="p" data-group-id="8785989109-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │      </span><span class="k">after</span><span class="w">
│ │ │ │          </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">timeout</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>For more information on timers in Erlang in general, see the
│ │ │ │  <a href="../../../lib/../erts/doc/html/time_correction.xhtml#timers"><em>Timers</em></a> section of the
│ │ │ │  <a href="../../../lib/../erts/doc/html/time_correction.xhtml"><em>Time and Time Correction in Erlang</em></a>
│ │ │ │ @@ -515,21 +515,21 @@
│ │ │ │  </span><span class="ss">false</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">4&gt; </span><span class="mf">0.0</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="o">-</span><span class="mf">0.0</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">5&gt; </span><span class="mf">0.0</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="o">+</span><span class="mf">0.0</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">6&gt; </span><span class="mi">1</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">7&gt; </span><span class="p" data-group-id="9601005496-1">#{</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="9601005496-1">}</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="9601005496-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="9601005496-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">7&gt; </span><span class="p" data-group-id="2735617815-1">#{</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="2735617815-1">}</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="2735617815-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="2735617815-2">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">8&gt; </span><span class="p" data-group-id="9601005496-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="9601005496-3">}</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="p" data-group-id="9601005496-4">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">2.0</span><span class="p" data-group-id="9601005496-4">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">8&gt; </span><span class="p" data-group-id="2735617815-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="2735617815-3">}</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="p" data-group-id="2735617815-4">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">2.0</span><span class="p" data-group-id="2735617815-4">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">9&gt; </span><span class="p" data-group-id="9601005496-5">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">2</span><span class="p" data-group-id="9601005496-5">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p" data-group-id="9601005496-6">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="9601005496-6">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">9&gt; </span><span class="p" data-group-id="2735617815-5">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">2</span><span class="p" data-group-id="2735617815-5">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p" data-group-id="2735617815-6">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="2735617815-6">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">10&gt; </span><span class="p" data-group-id="9601005496-7">&lt;&lt;</span><span class="mi">3</span><span class="p">:</span><span class="mi">2</span><span class="p" data-group-id="9601005496-7">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p" data-group-id="9601005496-8">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="9601005496-8">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">10&gt; </span><span class="p" data-group-id="2735617815-7">&lt;&lt;</span><span class="mi">3</span><span class="p">:</span><span class="mi">2</span><span class="p" data-group-id="2735617815-7">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p" data-group-id="2735617815-8">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="2735617815-8">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Prior to OTP 27, the term equivalence operators considered <code class="inline">0.0</code>
│ │ │ │  and <code class="inline">-0.0</code> to be the same term.</p><p>This was changed in OTP 27 but legacy code may have expected them to be
│ │ │ │  considered the same. To help users catch errors that may arise from an
│ │ │ │  upgrade, the compiler raises a warning when <code class="inline">0.0</code> is pattern-matched or used
│ │ │ │  in a term equivalence test.</p><p>If you need to match <code class="inline">0.0</code> specifically, the warning can be silenced by
│ │ │ │  writing <code class="inline">+0.0</code> instead, which produces the same term but makes the compiler
│ │ │ │  interpret the match as being done on purpose.</p></section><h2 id="arithmetic-expressions" class="section-heading">
│ │ │ │ @@ -555,15 +555,15 @@
│ │ │ │  </span><span class="mi">0</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">8&gt; </span><span class="mi">2#10</span><span class="w"> </span><span class="ow">bor</span><span class="w"> </span><span class="mi">2#01</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">9&gt; </span><span class="ss">a</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">10</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: an error occurred when evaluating an arithmetic expression
│ │ │ │       in operator  +/2
│ │ │ │          called as a + 10</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">10&gt; </span><span class="mi">1</span><span class="w"> </span><span class="nf">bsl</span><span class="w"> </span><span class="p" data-group-id="3271582481-1">(</span><span class="mi">1</span><span class="w"> </span><span class="ow">bsl</span><span class="w"> </span><span class="mi">64</span><span class="p" data-group-id="3271582481-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">10&gt; </span><span class="mi">1</span><span class="w"> </span><span class="nf">bsl</span><span class="w"> </span><span class="p" data-group-id="2171111234-1">(</span><span class="mi">1</span><span class="w"> </span><span class="ow">bsl</span><span class="w"> </span><span class="mi">64</span><span class="p" data-group-id="2171111234-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: a system limit has been reached
│ │ │ │       in operator  bsl/2
│ │ │ │          called as 1 bsl 18446744073709551616</span></code></pre><h2 id="boolean-expressions" class="section-heading">
│ │ │ │    <a href="#boolean-expressions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Boolean Expressions</span>
│ │ │ │ @@ -582,136 +582,136 @@
│ │ │ │    <a href="#short-circuit-expressions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Short-Circuit Expressions</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="makeup erlang" translate="no"><span class="n">Expr1</span><span class="w"> </span><span class="ow">orelse</span><span class="w"> </span><span class="n">Expr2</span><span class="w">
│ │ │ │  </span><span class="n">Expr1</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">Expr2</span></code></pre><p><code class="inline">Expr2</code> is evaluated only if necessary. That is, <code class="inline">Expr2</code> is evaluated only if:</p><ul><li><code class="inline">Expr1</code> evaluates to <code class="inline">false</code> in an <code class="inline">orelse</code> expression.</li></ul><p>or</p><ul><li><code class="inline">Expr1</code> evaluates to <code class="inline">true</code> in an <code class="inline">andalso</code> expression.</li></ul><p>Returns either the value of <code class="inline">Expr1</code> (that is, <code class="inline">true</code> or <code class="inline">false</code>) or the value of
│ │ │ │ -<code class="inline">Expr2</code> (if <code class="inline">Expr2</code> is evaluated).</p><p><em>Example 1:</em></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="o">-</span><span class="mf">1.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nc">math</span><span class="p">:</span><span class="nf">sqrt</span><span class="p" data-group-id="8826510171-1">(</span><span class="n">A</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="8826510171-1">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="k">of</span></code></pre><p>This works even if <code class="inline">A</code> is less than <code class="inline">-1.0</code>, since in that case, <a href="../../../lib/stdlib/doc/html/math.html#sqrt/1"><code class="inline">math:sqrt/1</code></a> is
│ │ │ │ -never evaluated.</p><p><em>Example 2:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">OnlyOne</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">is_atom</span><span class="p" data-group-id="0578653634-1">(</span><span class="n">L</span><span class="p" data-group-id="0578653634-1">)</span><span class="w"> </span><span class="nf">orelse</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="0578653634-2">(</span><span class="nf">is_list</span><span class="p" data-group-id="0578653634-3">(</span><span class="n">L</span><span class="p" data-group-id="0578653634-3">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="0578653634-4">(</span><span class="n">L</span><span class="p" data-group-id="0578653634-4">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="0578653634-2">)</span><span class="p">,</span></code></pre><p><code class="inline">Expr2</code> is not required to evaluate to a Boolean value. Because of that,
│ │ │ │ -<code class="inline">andalso</code> and <code class="inline">orelse</code> are tail-recursive.</p><p><em>Example 3 (tail-recursive function):</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">all</span><span class="p" data-group-id="0147778213-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0147778213-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="0147778213-2">]</span><span class="p" data-group-id="0147778213-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Pred</span><span class="p" data-group-id="0147778213-3">(</span><span class="n">Hd</span><span class="p" data-group-id="0147778213-3">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">all</span><span class="p" data-group-id="0147778213-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="0147778213-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">all</span><span class="p" data-group-id="0147778213-5">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0147778213-6">[</span><span class="p" data-group-id="0147778213-6">]</span><span class="p" data-group-id="0147778213-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +<code class="inline">Expr2</code> (if <code class="inline">Expr2</code> is evaluated).</p><p><em>Example 1:</em></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="o">-</span><span class="mf">1.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nc">math</span><span class="p">:</span><span class="nf">sqrt</span><span class="p" data-group-id="3303262718-1">(</span><span class="n">A</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="3303262718-1">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="k">of</span></code></pre><p>This works even if <code class="inline">A</code> is less than <code class="inline">-1.0</code>, since in that case, <a href="../../../lib/stdlib/doc/html/math.html#sqrt/1"><code class="inline">math:sqrt/1</code></a> is
│ │ │ │ +never evaluated.</p><p><em>Example 2:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">OnlyOne</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">is_atom</span><span class="p" data-group-id="9471844120-1">(</span><span class="n">L</span><span class="p" data-group-id="9471844120-1">)</span><span class="w"> </span><span class="nf">orelse</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="9471844120-2">(</span><span class="nf">is_list</span><span class="p" data-group-id="9471844120-3">(</span><span class="n">L</span><span class="p" data-group-id="9471844120-3">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="9471844120-4">(</span><span class="n">L</span><span class="p" data-group-id="9471844120-4">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="9471844120-2">)</span><span class="p">,</span></code></pre><p><code class="inline">Expr2</code> is not required to evaluate to a Boolean value. Because of that,
│ │ │ │ +<code class="inline">andalso</code> and <code class="inline">orelse</code> are tail-recursive.</p><p><em>Example 3 (tail-recursive function):</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">all</span><span class="p" data-group-id="0280657772-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0280657772-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="0280657772-2">]</span><span class="p" data-group-id="0280657772-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pred</span><span class="p" data-group-id="0280657772-3">(</span><span class="n">Hd</span><span class="p" data-group-id="0280657772-3">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">all</span><span class="p" data-group-id="0280657772-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="0280657772-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">all</span><span class="p" data-group-id="0280657772-5">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0280657772-6">[</span><span class="p" data-group-id="0280657772-6">]</span><span class="p" data-group-id="0280657772-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">true</span><span class="p">.</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP R13A, <code class="inline">Expr2</code> was required to evaluate to a Boolean value,
│ │ │ │  and as a consequence, <code class="inline">andalso</code> and <code class="inline">orelse</code> were <strong>not</strong> tail-recursive.</p></section><h2 id="list-operations" class="section-heading">
│ │ │ │    <a href="#list-operations" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">List Operations</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="makeup erlang" translate="no"><span class="n">Expr1</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Expr2</span><span class="w">
│ │ │ │  </span><span class="n">Expr1</span><span class="w"> </span><span class="o">--</span><span class="w"> </span><span class="n">Expr2</span></code></pre><p>The list concatenation operator <code class="inline">++</code> appends its second argument to its first
│ │ │ │  and returns the resulting list.</p><p>The list subtraction operator <code class="inline">--</code> produces a list that is a copy of the first
│ │ │ │  argument. The procedure is as follows: for each element in the second argument,
│ │ │ │ -the first occurrence of this element (if any) is removed.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8806162535-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8806162535-1">]</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="8806162535-2">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8806162535-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8806162535-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8806162535-3">]</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="8806162535-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8806162535-4">]</span><span class="w"> </span><span class="o">--</span><span class="w"> </span><span class="p" data-group-id="8806162535-5">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8806162535-5">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8806162535-6">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8806162535-6">]</span></code></pre><h2 id="map-expressions" class="section-heading">
│ │ │ │ +the first occurrence of this element (if any) is removed.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8683411968-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8683411968-1">]</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="8683411968-2">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8683411968-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8683411968-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8683411968-3">]</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="8683411968-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8683411968-4">]</span><span class="w"> </span><span class="o">--</span><span class="w"> </span><span class="p" data-group-id="8683411968-5">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8683411968-5">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8683411968-6">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8683411968-6">]</span></code></pre><h2 id="map-expressions" class="section-heading">
│ │ │ │    <a href="#map-expressions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Map Expressions</span>
│ │ │ │  </h2>
│ │ │ │  <h3 id="creating-maps" class="section-heading">
│ │ │ │    <a href="#creating-maps" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Creating Maps</span>
│ │ │ │  </h3>
│ │ │ │  <p>Constructing a new map is done by letting an expression <code class="inline">K</code> be associated with
│ │ │ │ -another expression <code class="inline">V</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5609019153-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="5609019153-1">}</span></code></pre><p>New maps can include multiple associations at construction by listing every
│ │ │ │ -association:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1377951279-1">#{</span><span class="n">K1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Kn</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Vn</span><span class="p" data-group-id="1377951279-1">}</span></code></pre><p>An empty map is constructed by not associating any terms with each other:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9373036260-1">#{</span><span class="p" data-group-id="9373036260-1">}</span></code></pre><p>All keys and values in the map are terms. Any expression is first evaluated and
│ │ │ │ +another expression <code class="inline">V</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0517158312-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="0517158312-1">}</span></code></pre><p>New maps can include multiple associations at construction by listing every
│ │ │ │ +association:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0059120937-1">#{</span><span class="n">K1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Kn</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Vn</span><span class="p" data-group-id="0059120937-1">}</span></code></pre><p>An empty map is constructed by not associating any terms with each other:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3686355308-1">#{</span><span class="p" data-group-id="3686355308-1">}</span></code></pre><p>All keys and values in the map are terms. Any expression is first evaluated and
│ │ │ │  then the resulting terms are used as <em>key</em> and <em>value</em> respectively.</p><p>Keys and values are separated by the <code class="inline">=&gt;</code> arrow and associations are separated
│ │ │ │ -by a comma (<code class="inline">,</code>).</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">M0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2109584071-1">#{</span><span class="p" data-group-id="2109584071-1">}</span><span class="p">,</span><span class="w">                 </span><span class="c1">% empty map</span><span class="w">
│ │ │ │ -</span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2109584071-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2109584071-3">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="2109584071-3">&gt;&gt;</span><span class="p" data-group-id="2109584071-2">}</span><span class="p">,</span><span class="w"> </span><span class="c1">% single association with literals</span><span class="w">
│ │ │ │ -</span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2109584071-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="2109584071-4">}</span><span class="p">,</span><span class="w">   </span><span class="c1">% multiple associations with literals</span><span class="w">
│ │ │ │ -</span><span class="n">M3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2109584071-5">#{</span><span class="ss">k</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2109584071-6">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p" data-group-id="2109584071-6">}</span><span class="p" data-group-id="2109584071-5">}</span><span class="p">,</span><span class="w">       </span><span class="c1">% single association with variables</span><span class="w">
│ │ │ │ -</span><span class="n">M4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2109584071-7">#{</span><span class="p" data-group-id="2109584071-8">{</span><span class="s">&quot;w&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2109584071-8">}</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="2109584071-9">(</span><span class="p" data-group-id="2109584071-9">)</span><span class="p" data-group-id="2109584071-7">}</span><span class="p">.</span><span class="w">  </span><span class="c1">% compound key associated with an evaluated expression</span></code></pre><p>Here, <code class="inline">A</code> and <code class="inline">B</code> are any expressions and <code class="inline">M0</code> through <code class="inline">M4</code> are the resulting
│ │ │ │ -map terms.</p><p>If two matching keys are declared, the latter key takes precedence.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="1090615020-1">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1090615020-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1090615020-2">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p" data-group-id="1090615020-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="1090615020-3">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1090615020-3">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1090615020-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="1090615020-4">}</span></code></pre><p>The order in which the expressions constructing the keys (and their associated
│ │ │ │ +by a comma (<code class="inline">,</code>).</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">M0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1096500634-1">#{</span><span class="p" data-group-id="1096500634-1">}</span><span class="p">,</span><span class="w">                 </span><span class="c1">% empty map</span><span class="w">
│ │ │ │ +</span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1096500634-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1096500634-3">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1096500634-3">&gt;&gt;</span><span class="p" data-group-id="1096500634-2">}</span><span class="p">,</span><span class="w"> </span><span class="c1">% single association with literals</span><span class="w">
│ │ │ │ +</span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1096500634-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1096500634-4">}</span><span class="p">,</span><span class="w">   </span><span class="c1">% multiple associations with literals</span><span class="w">
│ │ │ │ +</span><span class="n">M3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1096500634-5">#{</span><span class="ss">k</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1096500634-6">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p" data-group-id="1096500634-6">}</span><span class="p" data-group-id="1096500634-5">}</span><span class="p">,</span><span class="w">       </span><span class="c1">% single association with variables</span><span class="w">
│ │ │ │ +</span><span class="n">M4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1096500634-7">#{</span><span class="p" data-group-id="1096500634-8">{</span><span class="s">&quot;w&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="1096500634-8">}</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="1096500634-9">(</span><span class="p" data-group-id="1096500634-9">)</span><span class="p" data-group-id="1096500634-7">}</span><span class="p">.</span><span class="w">  </span><span class="c1">% compound key associated with an evaluated expression</span></code></pre><p>Here, <code class="inline">A</code> and <code class="inline">B</code> are any expressions and <code class="inline">M0</code> through <code class="inline">M4</code> are the resulting
│ │ │ │ +map terms.</p><p>If two matching keys are declared, the latter key takes precedence.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5873238440-1">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="5873238440-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5873238440-2">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p" data-group-id="5873238440-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="5873238440-3">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="5873238440-3">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5873238440-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="5873238440-4">}</span></code></pre><p>The order in which the expressions constructing the keys (and their associated
│ │ │ │  values) are evaluated is not defined. The syntactic order of the key-value pairs
│ │ │ │  in the construction is of no relevance, except in the recently mentioned case of
│ │ │ │  two matching keys.</p><h3 id="updating-maps" class="section-heading">
│ │ │ │    <a href="#updating-maps" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Updating Maps</span>
│ │ │ │  </h3>
│ │ │ │  <p>Updating a map has a syntax similar to constructing it.</p><p>An expression defining the map to be updated is put in front of the expression
│ │ │ │ -defining the keys to be updated and their respective values:</p><pre><code class="makeup erlang" translate="no"><span class="n">M</span><span class="p" data-group-id="9163291187-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="9163291187-1">}</span></code></pre><p>Here <code class="inline">M</code> is a term of type map, and <code class="inline">K</code> and <code class="inline">V</code> can be any expression.</p><p>If key <code class="inline">K</code> does not match any existing key in the map, a new association is
│ │ │ │ +defining the keys to be updated and their respective values:</p><pre><code class="makeup erlang" translate="no"><span class="n">M</span><span class="p" data-group-id="0898971868-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="0898971868-1">}</span></code></pre><p>Here <code class="inline">M</code> is a term of type map, and <code class="inline">K</code> and <code class="inline">V</code> can be any expression.</p><p>If key <code class="inline">K</code> does not match any existing key in the map, a new association is
│ │ │ │  created from key <code class="inline">K</code> to value <code class="inline">V</code>.</p><p>If key <code class="inline">K</code> matches an existing key in map <code class="inline">M</code>, its associated value is replaced
│ │ │ │  by the new value <code class="inline">V</code>. In both cases, the evaluated map expression returns a new
│ │ │ │ -map.</p><p>If <code class="inline">M</code> is not of type map, an exception of type <code class="inline">badmap</code> is raised.</p><p>To only update an existing value, the following syntax is used:</p><pre><code class="makeup erlang" translate="no"><span class="n">M</span><span class="p" data-group-id="0494320326-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="0494320326-1">}</span></code></pre><p>Here <code class="inline">M</code> is a term of type map, <code class="inline">V</code> is an expression, and <code class="inline">K</code> is an expression
│ │ │ │ +map.</p><p>If <code class="inline">M</code> is not of type map, an exception of type <code class="inline">badmap</code> is raised.</p><p>To only update an existing value, the following syntax is used:</p><pre><code class="makeup erlang" translate="no"><span class="n">M</span><span class="p" data-group-id="8644290058-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="8644290058-1">}</span></code></pre><p>Here <code class="inline">M</code> is a term of type map, <code class="inline">V</code> is an expression, and <code class="inline">K</code> is an expression
│ │ │ │  that evaluates to an existing key in <code class="inline">M</code>.</p><p>If key <code class="inline">K</code> does not match any existing keys in map <code class="inline">M</code>, an exception of type
│ │ │ │  <code class="inline">badkey</code> is raised at runtime. If a matching key <code class="inline">K</code> is present in map <code class="inline">M</code>,
│ │ │ │  its associated value is replaced by the new value <code class="inline">V</code>, and the evaluated map
│ │ │ │ -expression returns a new map.</p><p>If <code class="inline">M</code> is not of type map, an exception of type <code class="inline">badmap</code> is raised.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">M0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3220418780-1">#{</span><span class="p" data-group-id="3220418780-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M0</span><span class="p" data-group-id="3220418780-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="3220418780-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="3220418780-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="3220418780-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">M3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M2</span><span class="p" data-group-id="3220418780-4">#{</span><span class="s">&quot;function&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3220418780-5">(</span><span class="p" data-group-id="3220418780-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="3220418780-6">(</span><span class="p" data-group-id="3220418780-6">)</span><span class="w"> </span><span class="k">end</span><span class="p" data-group-id="3220418780-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">M4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M3</span><span class="p" data-group-id="3220418780-7">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3220418780-7">}</span><span class="p">.</span><span class="w">  </span><span class="c1">% &#39;a&#39; and &#39;b&#39; were added in `M1` and `M2`.</span></code></pre><p>Here <code class="inline">M0</code> is any map. It follows that <code class="inline">M1</code> through <code class="inline">M4</code> are maps as well.</p><p><em>More examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6649654335-1">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="6649654335-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6649654335-2">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="p" data-group-id="6649654335-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">M</span><span class="p" data-group-id="6649654335-3">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="6649654335-3">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6649654335-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="6649654335-4">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="n">M</span><span class="p" data-group-id="6649654335-5">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="6649654335-5">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6649654335-6">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="6649654335-6">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="n">M</span><span class="p" data-group-id="6649654335-7">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="6649654335-7">}</span><span class="p">.</span><span class="w">
│ │ │ │ +expression returns a new map.</p><p>If <code class="inline">M</code> is not of type map, an exception of type <code class="inline">badmap</code> is raised.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">M0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4692674931-1">#{</span><span class="p" data-group-id="4692674931-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M0</span><span class="p" data-group-id="4692674931-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="4692674931-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="4692674931-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="4692674931-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">M3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M2</span><span class="p" data-group-id="4692674931-4">#{</span><span class="s">&quot;function&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="4692674931-5">(</span><span class="p" data-group-id="4692674931-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="4692674931-6">(</span><span class="p" data-group-id="4692674931-6">)</span><span class="w"> </span><span class="k">end</span><span class="p" data-group-id="4692674931-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">M4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M3</span><span class="p" data-group-id="4692674931-7">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="4692674931-7">}</span><span class="p">.</span><span class="w">  </span><span class="c1">% &#39;a&#39; and &#39;b&#39; were added in `M1` and `M2`.</span></code></pre><p>Here <code class="inline">M0</code> is any map. It follows that <code class="inline">M1</code> through <code class="inline">M4</code> are maps as well.</p><p><em>More examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1919714739-1">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="1919714739-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1919714739-2">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="p" data-group-id="1919714739-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">M</span><span class="p" data-group-id="1919714739-3">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1919714739-3">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1919714739-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1919714739-4">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="n">M</span><span class="p" data-group-id="1919714739-5">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1919714739-5">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1919714739-6">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1919714739-6">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="n">M</span><span class="p" data-group-id="1919714739-7">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1919714739-7">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: bad argument</span></code></pre><p>As in construction, the order in which the key and value expressions are
│ │ │ │  evaluated is not defined. The syntactic order of the key-value pairs in the
│ │ │ │  update is of no relevance, except in the case where two keys match. In that
│ │ │ │  case, the latter value is used.</p><h3 id="maps-in-patterns" class="section-heading">
│ │ │ │    <a href="#maps-in-patterns" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Maps in Patterns</span>
│ │ │ │  </h3>
│ │ │ │ -<p>Matching of key-value associations from maps is done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4133755987-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="4133755987-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>Here <code class="inline">M</code> is any map. The key <code class="inline">K</code> must be a
│ │ │ │ +<p>Matching of key-value associations from maps is done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0559557159-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="0559557159-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>Here <code class="inline">M</code> is any map. The key <code class="inline">K</code> must be a
│ │ │ │  <a href="expressions.xhtml#guard-expressions">guard expression</a>, with all variables already
│ │ │ │  bound. <code class="inline">V</code> can be any pattern with either bound or unbound variables.</p><p>If the variable <code class="inline">V</code> is unbound, it becomes bound to the value associated with
│ │ │ │  the key <code class="inline">K</code>, which must exist in the map <code class="inline">M</code>. If the variable <code class="inline">V</code> is bound, it
│ │ │ │  must match the value associated with <code class="inline">K</code> in <code class="inline">M</code>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 23, the expression defining the key <code class="inline">K</code> was restricted to be
│ │ │ │ -either a single variable or a literal.</p></section><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6777054892-1">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6777054892-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6777054892-2">}</span><span class="p" data-group-id="6777054892-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6777054892-3">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6777054892-4">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6777054892-4">}</span><span class="p" data-group-id="6777054892-3">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="6777054892-5">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="6777054892-6">{</span><span class="mi">1</span><span class="p">,</span><span class="n">B</span><span class="p" data-group-id="6777054892-6">}</span><span class="p" data-group-id="6777054892-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6777054892-7">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6777054892-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6777054892-8">}</span><span class="p" data-group-id="6777054892-7">}</span><span class="w">
│ │ │ │ +either a single variable or a literal.</p></section><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2453318427-1">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2453318427-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2453318427-2">}</span><span class="p" data-group-id="2453318427-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2453318427-3">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2453318427-4">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2453318427-4">}</span><span class="p" data-group-id="2453318427-3">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="2453318427-5">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="2453318427-6">{</span><span class="mi">1</span><span class="p">,</span><span class="n">B</span><span class="p" data-group-id="2453318427-6">}</span><span class="p" data-group-id="2453318427-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2453318427-7">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2453318427-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2453318427-8">}</span><span class="p" data-group-id="2453318427-7">}</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">3&gt; </span><span class="n">B</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="mi">2</span><span class="p">.</span></code></pre><p>This binds variable <code class="inline">B</code> to integer <code class="inline">2</code>.</p><p>Similarly, multiple values from the map can be matched:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5637878369-1">#{</span><span class="n">K1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Kn</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Vn</span><span class="p" data-group-id="5637878369-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>Here keys <code class="inline">K1</code> through <code class="inline">Kn</code> are any expressions with literals or bound
│ │ │ │ +</span><span class="mi">2</span><span class="p">.</span></code></pre><p>This binds variable <code class="inline">B</code> to integer <code class="inline">2</code>.</p><p>Similarly, multiple values from the map can be matched:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5974934078-1">#{</span><span class="n">K1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Kn</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Vn</span><span class="p" data-group-id="5974934078-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>Here keys <code class="inline">K1</code> through <code class="inline">Kn</code> are any expressions with literals or bound
│ │ │ │  variables. If all key expressions evaluate successfully and all keys
│ │ │ │  exist in map <code class="inline">M</code>, all variables in <code class="inline">V1 .. Vn</code> are matched to the
│ │ │ │  associated values of their respective keys.</p><p>If the matching conditions are not met, the match fails.</p><p>Note that when matching a map, only the <code class="inline">:=</code> operator (not the <code class="inline">=&gt;</code>) is allowed
│ │ │ │  as a delimiter for the associations.</p><p>The order in which keys are declared in matching has no relevance.</p><p>Duplicate keys are allowed in matching and match each pattern associated with the
│ │ │ │ -keys:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1602878870-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V2</span><span class="p" data-group-id="1602878870-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>The empty map literal (<code class="inline">#{}</code>) matches any map when used as a pattern:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7629234720-1">#{</span><span class="p" data-group-id="7629234720-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expr</span></code></pre><p>This expression matches if the expression <code class="inline">Expr</code> is of type map; otherwise, it
│ │ │ │ -fails with an exception <code class="inline">badmatch</code>.</p><p>Here the key to be retrieved is constructed from an expression:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3350291248-1">#{</span><span class="p" data-group-id="3350291248-2">{</span><span class="ss">tag</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="3350291248-3">(</span><span class="n">List</span><span class="p" data-group-id="3350291248-3">)</span><span class="p" data-group-id="3350291248-2">}</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="3350291248-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map</span></code></pre><p><code class="inline">List</code> must be an already bound variable.</p><h4>Matching Syntax</h4><p>Matching of literals as keys is allowed in function heads:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% only start if not_started</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="7819898186-1">(</span><span class="ss">start</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7819898186-2">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">not_started</span><span class="p" data-group-id="7819898186-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="7819898186-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +keys:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0170911264-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V2</span><span class="p" data-group-id="0170911264-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>The empty map literal (<code class="inline">#{}</code>) matches any map when used as a pattern:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8586108054-1">#{</span><span class="p" data-group-id="8586108054-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expr</span></code></pre><p>This expression matches if the expression <code class="inline">Expr</code> is of type map; otherwise, it
│ │ │ │ +fails with an exception <code class="inline">badmatch</code>.</p><p>Here the key to be retrieved is constructed from an expression:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8673656837-1">#{</span><span class="p" data-group-id="8673656837-2">{</span><span class="ss">tag</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="8673656837-3">(</span><span class="n">List</span><span class="p" data-group-id="8673656837-3">)</span><span class="p" data-group-id="8673656837-2">}</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="8673656837-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map</span></code></pre><p><code class="inline">List</code> must be an already bound variable.</p><h4>Matching Syntax</h4><p>Matching of literals as keys is allowed in function heads:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% only start if not_started</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="5487776210-1">(</span><span class="ss">start</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5487776210-2">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">not_started</span><span class="p" data-group-id="5487776210-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="5487776210-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7819898186-3">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="7819898186-4">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">start</span><span class="p" data-group-id="7819898186-4">}</span><span class="p" data-group-id="7819898186-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5487776210-3">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="5487776210-4">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">start</span><span class="p" data-group-id="5487776210-4">}</span><span class="p" data-group-id="5487776210-3">}</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% only change if started</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="7819898186-5">(</span><span class="ss">change</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7819898186-6">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">start</span><span class="p" data-group-id="7819898186-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="7819898186-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="5487776210-5">(</span><span class="ss">change</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5487776210-6">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">start</span><span class="p" data-group-id="5487776210-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="5487776210-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7819898186-7">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="7819898186-8">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">changed</span><span class="p" data-group-id="7819898186-8">}</span><span class="p" data-group-id="7819898186-7">}</span><span class="p">;</span></code></pre><h3 id="maps-in-guards" class="section-heading">
│ │ │ │ +    </span><span class="p" data-group-id="5487776210-7">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="5487776210-8">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">changed</span><span class="p" data-group-id="5487776210-8">}</span><span class="p" data-group-id="5487776210-7">}</span><span class="p">;</span></code></pre><h3 id="maps-in-guards" class="section-heading">
│ │ │ │    <a href="#maps-in-guards" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Maps in Guards</span>
│ │ │ │  </h3>
│ │ │ │  <p>Maps are allowed in guards as long as all subexpressions are valid guard
│ │ │ │  expressions.</p><p>The following guard BIFs handle maps:</p><ul><li><a href="../../../lib/../erts/doc/html/erlang.html#is_map/1">is_map/1</a> in the <code class="inline">erlang</code> module</li><li><a href="../../../lib/../erts/doc/html/erlang.html#is_map_key/2">is_map_key/2</a> in the <code class="inline">erlang</code> module</li><li><a href="../../../lib/../erts/doc/html/erlang.html#map_get/2">map_get/2</a> in the <code class="inline">erlang</code> module</li><li><a href="../../../lib/../erts/doc/html/erlang.html#map_size/1">map_size/1</a> in the <code class="inline">erlang</code> module</li></ul><h2 id="bit-syntax-expressions" class="section-heading">
│ │ │ │    <a href="#bit-syntax-expressions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Bit Syntax Expressions</span>
│ │ │ │  </h2>
│ │ │ │  <p>The bit syntax operates on <em>bit strings</em>. A bit string is a sequence of bits
│ │ │ │ -ordered from the most significant bit to the least significant bit.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7381272284-1">&lt;&lt;</span><span class="p" data-group-id="7381272284-1">&gt;&gt;</span><span class="w">  </span><span class="c1">% The empty bit string, zero length</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7381272284-2">&lt;&lt;</span><span class="n">E1</span><span class="p" data-group-id="7381272284-2">&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7381272284-3">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">En</span><span class="p" data-group-id="7381272284-3">&gt;&gt;</span></code></pre><p>Each element <code class="inline">Ei</code> specifies a <em>segment</em> of the bit string. The segments are
│ │ │ │ +ordered from the most significant bit to the least significant bit.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3388392390-1">&lt;&lt;</span><span class="p" data-group-id="3388392390-1">&gt;&gt;</span><span class="w">  </span><span class="c1">% The empty bit string, zero length</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3388392390-2">&lt;&lt;</span><span class="n">E1</span><span class="p" data-group-id="3388392390-2">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3388392390-3">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">En</span><span class="p" data-group-id="3388392390-3">&gt;&gt;</span></code></pre><p>Each element <code class="inline">Ei</code> specifies a <em>segment</em> of the bit string. The segments are
│ │ │ │  ordered left to right from the most significant bit to the least significant bit
│ │ │ │  of the bit string.</p><p>Each segment specification <code class="inline">Ei</code> is a value, whose default type is <code class="inline">integer</code>,
│ │ │ │  followed by an optional <em>size expression</em> and an optional <em>type specifier list</em>.</p><pre><code class="makeup erlang" translate="no"><span class="n">Ei</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Value</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │ │       </span><span class="n">Value</span><span class="p">:</span><span class="n">Size</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │ │       </span><span class="n">Value</span><span class="o">/</span><span class="n">TypeSpecifierList</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │ │       </span><span class="n">Value</span><span class="p">:</span><span class="n">Size</span><span class="o">/</span><span class="n">TypeSpecifierList</span></code></pre><p>When used in a bit string construction, <code class="inline">Value</code> is an expression that is to
│ │ │ │  evaluate to an integer, float, or bit string. If the expression is not a single
│ │ │ │ @@ -722,34 +722,34 @@
│ │ │ │  <a href="expressions.xhtml#guard-expressions">guard expression</a> that evaluates to an
│ │ │ │  integer. All variables in the guard expression must be already bound.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 23, <code class="inline">Size</code> was restricted to be an integer or a variable
│ │ │ │  bound to an integer.</p></section><p>The value of <code class="inline">Size</code> specifies the size of the segment in units (see below). The
│ │ │ │  default value depends on the type (see below):</p><ul><li>For <code class="inline">integer</code> it is 8.</li><li>For <code class="inline">float</code> it is 64.</li><li>For <code class="inline">binary</code> and <code class="inline">bitstring</code> it is the whole binary or bit string.</li></ul><p>In matching, the default value for a binary or bit string segment is only valid
│ │ │ │  for the last element. All other bit string or binary elements in the matching
│ │ │ │  must have a size specification.</p><p><a href="" id="binaries"></a></p><p><strong>Binaries</strong></p><p>A bit string with a length that is a multiple of 8 bits is known as a <em>binary</em>,
│ │ │ │  which is the most common and useful type of bit string.</p><p>A binary has a canonical representation in memory. Here follows a sequence of
│ │ │ │ -bytes where each byte's value is its sequence number:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7990318899-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="mi">10</span><span class="p" data-group-id="7990318899-1">&gt;&gt;</span></code></pre><p>Bit strings are a later generalization of binaries, so many texts and much
│ │ │ │ -information about binaries apply just as well to bit strings.</p><p><strong>Example:</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4099735872-1">&lt;&lt;</span><span class="n">A</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4099735872-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4099735872-2">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="4099735872-2">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +bytes where each byte's value is its sequence number:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7057337429-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="mi">10</span><span class="p" data-group-id="7057337429-1">&gt;&gt;</span></code></pre><p>Bit strings are a later generalization of binaries, so many texts and much
│ │ │ │ +information about binaries apply just as well to bit strings.</p><p><strong>Example:</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3134800687-1">&lt;&lt;</span><span class="n">A</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3134800687-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3134800687-2">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="3134800687-2">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">* 1:3: a binary field without size is only allowed at the end of a binary pattern</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="4099735872-3">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">3</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4099735872-3">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4099735872-4">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="4099735872-4">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4099735872-5">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="4099735872-5">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="3134800687-3">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">3</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3134800687-3">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3134800687-4">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="3134800687-4">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3134800687-5">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="3134800687-5">&gt;&gt;</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">3&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4099735872-6">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="4099735872-6">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3134800687-6">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="3134800687-6">&gt;&gt;</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">4&gt; </span><span class="n">B</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4099735872-7">&lt;&lt;</span><span class="s">&quot;de&quot;</span><span class="p" data-group-id="4099735872-7">&gt;&gt;</span></code></pre><p>For the <code class="inline">utf8</code>, <code class="inline">utf16</code>, and <code class="inline">utf32</code> types, <code class="inline">Size</code> must not be given. The size
│ │ │ │ +</span><span class="p" data-group-id="3134800687-7">&lt;&lt;</span><span class="s">&quot;de&quot;</span><span class="p" data-group-id="3134800687-7">&gt;&gt;</span></code></pre><p>For the <code class="inline">utf8</code>, <code class="inline">utf16</code>, and <code class="inline">utf32</code> types, <code class="inline">Size</code> must not be given. The size
│ │ │ │  of the segment is implicitly determined by the type and value itself.</p><p><code class="inline">TypeSpecifierList</code> is a list of type specifiers, in any order, separated by
│ │ │ │  hyphens (-). Default values are used for any omitted type specifiers.</p><ul><li><p><strong><code class="inline">Type</code>= <code class="inline">integer</code> | <code class="inline">float</code> | <code class="inline">binary</code> | <code class="inline">bytes</code> | <code class="inline">bitstring</code> | <code class="inline">bits</code> |
│ │ │ │  <code class="inline">utf8</code> | <code class="inline">utf16</code> | <code class="inline">utf32</code></strong> - The default is <code class="inline">integer</code>. <code class="inline">bytes</code> is a
│ │ │ │  shorthand for <code class="inline">binary</code> and <code class="inline">bits</code> is a shorthand for <code class="inline">bitstring</code>. See below
│ │ │ │  for more information about the <code class="inline">utf</code> types.</p></li><li><p><strong><code class="inline">Signedness</code>= <code class="inline">signed</code> | <code class="inline">unsigned</code></strong> - Only matters for matching and when
│ │ │ │  the type is <code class="inline">integer</code>. The default is <code class="inline">unsigned</code>.</p></li><li><p><strong><code class="inline">Endianness</code>= <code class="inline">big</code> | <code class="inline">little</code> | <code class="inline">native</code></strong> - Specifies byte level (octet
│ │ │ │  level) endianness (byte order). Native-endian means that the endianness is
│ │ │ │  resolved at load time to be either big-endian or little-endian, depending on
│ │ │ │  what is native for the CPU that the Erlang machine is run on. Endianness only
│ │ │ │  matters when the <strong>Type</strong> is either <code class="inline">integer</code>, <code class="inline">utf16</code>, <code class="inline">utf32</code>, or <code class="inline">float</code>. The
│ │ │ │ -default is <code class="inline">big</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6033316247-1">&lt;&lt;</span><span class="mi">16#1234</span><span class="p">:</span><span class="mi">16</span><span class="o">/</span><span class="ss">little</span><span class="p" data-group-id="6033316247-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6033316247-2">&lt;&lt;</span><span class="mi">16#3412</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="6033316247-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6033316247-3">&lt;&lt;</span><span class="mi">16#34</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">16#12</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="6033316247-3">&gt;&gt;</span></code></pre></li><li><p><strong><code class="inline">Unit</code>= <code class="inline">unit:IntegerLiteral</code></strong> - The allowed range is 1 through 256.
│ │ │ │ +default is <code class="inline">big</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6563388875-1">&lt;&lt;</span><span class="mi">16#1234</span><span class="p">:</span><span class="mi">16</span><span class="o">/</span><span class="ss">little</span><span class="p" data-group-id="6563388875-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6563388875-2">&lt;&lt;</span><span class="mi">16#3412</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="6563388875-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6563388875-3">&lt;&lt;</span><span class="mi">16#34</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">16#12</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="6563388875-3">&gt;&gt;</span></code></pre></li><li><p><strong><code class="inline">Unit</code>= <code class="inline">unit:IntegerLiteral</code></strong> - The allowed range is 1 through 256.
│ │ │ │  Defaults to 1 for <code class="inline">integer</code>, <code class="inline">float</code>, and <code class="inline">bitstring</code>, and to 8 for <code class="inline">binary</code>.
│ │ │ │  For types <code class="inline">bitstring</code>, <code class="inline">bits</code>, and <code class="inline">bytes</code>, it is not allowed to specify a
│ │ │ │  unit value different from the default value. No unit specifier must be given
│ │ │ │  for the types <code class="inline">utf8</code>, <code class="inline">utf16</code>, and <code class="inline">utf32</code>.</p></li></ul><h3 id="integer-segments" class="section-heading">
│ │ │ │    <a href="#integer-segments" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │ @@ -774,41 +774,41 @@
│ │ │ │    </a>
│ │ │ │    <span class="text">Binary segments</span>
│ │ │ │  </h3>
│ │ │ │  <p>In this section, the phrase &quot;binary segment&quot; refers to any one of the segment
│ │ │ │  types <code class="inline">binary</code>, <code class="inline">bitstring</code>, <code class="inline">bytes</code>, and <code class="inline">bits</code>.</p><p>See also the paragraphs about <a href="expressions.xhtml#binaries">Binaries</a>.</p><p>When constructing binaries and no size is specified for a binary segment, the
│ │ │ │  entire binary value is interpolated into the binary being constructed. However,
│ │ │ │  the size in bits of the binary being interpolated must be evenly divisible by
│ │ │ │ -the unit value for the segment; otherwise an exception is raised.</p><p>For example, the following examples all succeed:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="1103372731-1">&lt;&lt;</span><span class="p" data-group-id="1103372731-2">(</span><span class="p" data-group-id="1103372731-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1103372731-3">&gt;&gt;</span><span class="p" data-group-id="1103372731-2">)</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="1103372731-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1103372731-4">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1103372731-4">&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="1103372731-5">&lt;&lt;</span><span class="p" data-group-id="1103372731-6">(</span><span class="p" data-group-id="1103372731-7">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1103372731-7">&gt;&gt;</span><span class="p" data-group-id="1103372731-6">)</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1103372731-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1103372731-8">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1103372731-8">&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="1103372731-9">&lt;&lt;</span><span class="p" data-group-id="1103372731-10">(</span><span class="p" data-group-id="1103372731-11">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1103372731-11">&gt;&gt;</span><span class="p" data-group-id="1103372731-10">)</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1103372731-9">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1103372731-12">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1103372731-12">&gt;&gt;</span></code></pre><p>The first two examples have a unit value of 1 for the segment, while the third
│ │ │ │ +the unit value for the segment; otherwise an exception is raised.</p><p>For example, the following examples all succeed:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="6623767655-1">&lt;&lt;</span><span class="p" data-group-id="6623767655-2">(</span><span class="p" data-group-id="6623767655-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="6623767655-3">&gt;&gt;</span><span class="p" data-group-id="6623767655-2">)</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="6623767655-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6623767655-4">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="6623767655-4">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="6623767655-5">&lt;&lt;</span><span class="p" data-group-id="6623767655-6">(</span><span class="p" data-group-id="6623767655-7">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="6623767655-7">&gt;&gt;</span><span class="p" data-group-id="6623767655-6">)</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="6623767655-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6623767655-8">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="6623767655-8">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="6623767655-9">&lt;&lt;</span><span class="p" data-group-id="6623767655-10">(</span><span class="p" data-group-id="6623767655-11">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="6623767655-11">&gt;&gt;</span><span class="p" data-group-id="6623767655-10">)</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6623767655-9">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6623767655-12">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="6623767655-12">&gt;&gt;</span></code></pre><p>The first two examples have a unit value of 1 for the segment, while the third
│ │ │ │  segment has a unit value of 8.</p><p>Attempting to interpolate a bit string of size 1 into a binary segment with unit
│ │ │ │ -8 (the default unit for <code class="inline">binary</code>) fails as shown in this example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="1153128355-1">&lt;&lt;</span><span class="p" data-group-id="1153128355-2">(</span><span class="p" data-group-id="1153128355-3">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1153128355-3">&gt;&gt;</span><span class="p" data-group-id="1153128355-2">)</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1153128355-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="gt">** exception error: bad argument</span></code></pre><p>For the construction to succeed, the unit value of the segment must be 1:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="4428147136-1">&lt;&lt;</span><span class="p" data-group-id="4428147136-2">(</span><span class="p" data-group-id="4428147136-3">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4428147136-3">&gt;&gt;</span><span class="p" data-group-id="4428147136-2">)</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="4428147136-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4428147136-4">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4428147136-4">&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="4428147136-5">&lt;&lt;</span><span class="p" data-group-id="4428147136-6">(</span><span class="p" data-group-id="4428147136-7">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4428147136-7">&gt;&gt;</span><span class="p" data-group-id="4428147136-6">)</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4428147136-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4428147136-8">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4428147136-8">&gt;&gt;</span></code></pre><p>Similarly, when matching a binary segment with no size specified, the match
│ │ │ │ +8 (the default unit for <code class="inline">binary</code>) fails as shown in this example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="6895774621-1">&lt;&lt;</span><span class="p" data-group-id="6895774621-2">(</span><span class="p" data-group-id="6895774621-3">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="6895774621-3">&gt;&gt;</span><span class="p" data-group-id="6895774621-2">)</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6895774621-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gt">** exception error: bad argument</span></code></pre><p>For the construction to succeed, the unit value of the segment must be 1:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="0314768925-1">&lt;&lt;</span><span class="p" data-group-id="0314768925-2">(</span><span class="p" data-group-id="0314768925-3">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="0314768925-3">&gt;&gt;</span><span class="p" data-group-id="0314768925-2">)</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="0314768925-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0314768925-4">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="0314768925-4">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="0314768925-5">&lt;&lt;</span><span class="p" data-group-id="0314768925-6">(</span><span class="p" data-group-id="0314768925-7">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="0314768925-7">&gt;&gt;</span><span class="p" data-group-id="0314768925-6">)</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="0314768925-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0314768925-8">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="0314768925-8">&gt;&gt;</span></code></pre><p>Similarly, when matching a binary segment with no size specified, the match
│ │ │ │  succeeds if and only if the size in bits of the rest of the binary is evenly
│ │ │ │ -divisible by the unit value:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3292080503-1">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="3292080503-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3292080503-2">&lt;&lt;</span><span class="s">&quot;&quot;</span><span class="p" data-group-id="3292080503-2">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3292080503-3">&lt;&lt;</span><span class="p" data-group-id="3292080503-3">&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="3292080503-4">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="3292080503-4">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3292080503-5">&lt;&lt;</span><span class="s">&quot;a&quot;</span><span class="p" data-group-id="3292080503-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +divisible by the unit value:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="0899019217-1">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="0899019217-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0899019217-2">&lt;&lt;</span><span class="s">&quot;&quot;</span><span class="p" data-group-id="0899019217-2">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0899019217-3">&lt;&lt;</span><span class="p" data-group-id="0899019217-3">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="0899019217-4">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="0899019217-4">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0899019217-5">&lt;&lt;</span><span class="s">&quot;a&quot;</span><span class="p" data-group-id="0899019217-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no match of right hand side value &lt;&lt;&quot;a&quot;&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="3292080503-6">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="3292080503-6">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3292080503-7">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="3292080503-7">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3292080503-8">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="3292080503-8">&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="p" data-group-id="3292080503-9">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="3292080503-9">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3292080503-10">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="3292080503-10">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="0899019217-6">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="0899019217-6">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0899019217-7">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="0899019217-7">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0899019217-8">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="0899019217-8">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="p" data-group-id="0899019217-9">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="0899019217-9">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0899019217-10">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="0899019217-10">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no match of right hand side value &lt;&lt;&quot;abc&quot;&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="3292080503-11">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="3292080503-11">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3292080503-12">&lt;&lt;</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="3292080503-12">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3292080503-13">&lt;&lt;</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="3292080503-13">&gt;&gt;</span></code></pre><p>When a size is explicitly specified for a binary segment, the segment size in
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="0899019217-11">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="0899019217-11">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0899019217-12">&lt;&lt;</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="0899019217-12">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0899019217-13">&lt;&lt;</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="0899019217-13">&gt;&gt;</span></code></pre><p>When a size is explicitly specified for a binary segment, the segment size in
│ │ │ │  bits is the value of <code class="inline">Size</code> multiplied by the default or explicit unit value.</p><p>When constructing binaries, the size of the binary being interpolated into the
│ │ │ │ -constructed binary must be at least as large as the size of the binary segment.</p><p><strong>Examples:</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4626709987-1">&lt;&lt;</span><span class="p" data-group-id="4626709987-2">(</span><span class="p" data-group-id="4626709987-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="4626709987-3">&gt;&gt;</span><span class="p" data-group-id="4626709987-2">)</span><span class="p">:</span><span class="mi">2</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4626709987-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4626709987-4">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="4626709987-4">&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="4626709987-5">&lt;&lt;</span><span class="p" data-group-id="4626709987-6">(</span><span class="p" data-group-id="4626709987-7">&lt;&lt;</span><span class="s">&quot;a&quot;</span><span class="p" data-group-id="4626709987-7">&gt;&gt;</span><span class="p" data-group-id="4626709987-6">)</span><span class="p">:</span><span class="mi">2</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4626709987-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +constructed binary must be at least as large as the size of the binary segment.</p><p><strong>Examples:</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7529608903-1">&lt;&lt;</span><span class="p" data-group-id="7529608903-2">(</span><span class="p" data-group-id="7529608903-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="7529608903-3">&gt;&gt;</span><span class="p" data-group-id="7529608903-2">)</span><span class="p">:</span><span class="mi">2</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7529608903-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7529608903-4">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="7529608903-4">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="7529608903-5">&lt;&lt;</span><span class="p" data-group-id="7529608903-6">(</span><span class="p" data-group-id="7529608903-7">&lt;&lt;</span><span class="s">&quot;a&quot;</span><span class="p" data-group-id="7529608903-7">&gt;&gt;</span><span class="p" data-group-id="7529608903-6">)</span><span class="p">:</span><span class="mi">2</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7529608903-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: construction of binary failed
│ │ │ │          *** segment 1 of type &#39;binary&#39;: the value &lt;&lt;&quot;a&quot;&gt;&gt; is shorter than the size of the segment</span></code></pre><h3 id="unicode-segments" class="section-heading">
│ │ │ │    <a href="#unicode-segments" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Unicode segments</span>
│ │ │ │  </h3>
│ │ │ │ @@ -824,78 +824,78 @@
│ │ │ │  range <code class="inline">0</code> through <code class="inline">16#D7FF</code> or <code class="inline">16#E000</code> through <code class="inline">16#10FFFF</code>. The match fails if the
│ │ │ │  returned value falls outside those ranges.</p><p>A segment of type <code class="inline">utf8</code> matches 1-4 bytes in the bit string, if the bit string
│ │ │ │  at the match position contains a valid UTF-8 sequence. (See RFC-3629 or the
│ │ │ │  Unicode standard.)</p><p>A segment of type <code class="inline">utf16</code> can match 2 or 4 bytes in the bit string. The match
│ │ │ │  fails if the bit string at the match position does not contain a legal UTF-16
│ │ │ │  encoding of a Unicode code point. (See RFC-2781 or the Unicode standard.)</p><p>A segment of type <code class="inline">utf32</code> can match 4 bytes in the bit string in the same way as
│ │ │ │  an <code class="inline">integer</code> segment matches 32 bits. The match fails if the resulting integer
│ │ │ │ -is outside the legal ranges previously mentioned.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8230710456-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="8230710456-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8230710456-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="8230710456-2">&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8230710456-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="8230710456-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8230710456-4">&lt;&lt;</span><span class="mi">97</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="8230710456-4">&gt;&gt;</span><span class="w">
│ │ │ │ +is outside the legal ranges previously mentioned.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1504609037-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="1504609037-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1504609037-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="1504609037-2">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1504609037-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1504609037-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1504609037-4">&lt;&lt;</span><span class="mi">97</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="1504609037-4">&gt;&gt;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8230710456-5">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="8230710456-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8230710456-6">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="8230710456-6">&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="p" data-group-id="8230710456-7">&lt;&lt;</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="8230710456-7">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8230710456-8">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="8230710456-8">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8230710456-9">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="8230710456-9">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1504609037-5">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="1504609037-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1504609037-6">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="1504609037-6">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="p" data-group-id="1504609037-7">&lt;&lt;</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="1504609037-7">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1504609037-8">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="1504609037-8">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1504609037-9">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="1504609037-9">&gt;&gt;</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">5&gt; </span><span class="n">C</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">42</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="p" data-group-id="8230710456-10">&lt;&lt;</span><span class="n">D</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="n">E</span><span class="p">,</span><span class="n">F</span><span class="p" data-group-id="8230710456-10">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8230710456-11">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="8230710456-11">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8230710456-12">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="8230710456-12">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="p" data-group-id="1504609037-10">&lt;&lt;</span><span class="n">D</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="n">E</span><span class="p">,</span><span class="n">F</span><span class="p" data-group-id="1504609037-10">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1504609037-11">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="1504609037-11">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1504609037-12">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="1504609037-12">&gt;&gt;</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">7&gt; </span><span class="n">D</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">273</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">8&gt; </span><span class="n">F</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">42</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">9&gt; </span><span class="p" data-group-id="8230710456-13">&lt;&lt;</span><span class="n">G</span><span class="p">,</span><span class="n">H</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8230710456-13">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8230710456-14">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="8230710456-14">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8230710456-15">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="8230710456-15">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">9&gt; </span><span class="p" data-group-id="1504609037-13">&lt;&lt;</span><span class="n">G</span><span class="p">,</span><span class="n">H</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1504609037-13">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1504609037-14">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="1504609037-14">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1504609037-15">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="1504609037-15">&gt;&gt;</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">10&gt; </span><span class="n">H</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8230710456-16">&lt;&lt;</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="8230710456-16">&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">11&gt; </span><span class="p" data-group-id="8230710456-17">&lt;&lt;</span><span class="n">G</span><span class="p">,</span><span class="n">J</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="8230710456-17">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8230710456-18">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">12</span><span class="p" data-group-id="8230710456-18">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8230710456-19">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">10</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="8230710456-19">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1504609037-16">&lt;&lt;</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="1504609037-16">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">11&gt; </span><span class="p" data-group-id="1504609037-17">&lt;&lt;</span><span class="n">G</span><span class="p">,</span><span class="n">J</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="1504609037-17">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1504609037-18">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">12</span><span class="p" data-group-id="1504609037-18">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1504609037-19">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">10</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="1504609037-19">&gt;&gt;</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">12&gt; </span><span class="n">J</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8230710456-20">&lt;&lt;</span><span class="mi">17</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">10</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="8230710456-20">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1504609037-20">&lt;&lt;</span><span class="mi">17</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">10</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="1504609037-20">&gt;&gt;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="mi">13</span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="8230710456-21">&lt;&lt;</span><span class="mi">1024</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="8230710456-21">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8230710456-22">&lt;&lt;</span><span class="mi">208</span><span class="p">,</span><span class="mi">128</span><span class="p" data-group-id="8230710456-22">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="mi">13</span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="1504609037-21">&lt;&lt;</span><span class="mi">1024</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="1504609037-21">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1504609037-22">&lt;&lt;</span><span class="mi">208</span><span class="p">,</span><span class="mi">128</span><span class="p" data-group-id="1504609037-22">&gt;&gt;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="mi">14</span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="8230710456-23">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">:</span><span class="mi">7</span><span class="p" data-group-id="8230710456-23">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8230710456-24">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="8230710456-24">&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">15&gt; </span><span class="p" data-group-id="8230710456-25">&lt;&lt;</span><span class="mi">16#123</span><span class="p">:</span><span class="mi">12</span><span class="o">/</span><span class="ss">little</span><span class="p" data-group-id="8230710456-25">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8230710456-26">&lt;&lt;</span><span class="mi">16#231</span><span class="p">:</span><span class="mi">12</span><span class="p" data-group-id="8230710456-26">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8230710456-27">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="8230710456-27">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8230710456-28">&lt;&lt;</span><span class="mi">35</span><span class="p">,</span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="8230710456-28">&gt;&gt;</span></code></pre><p>Notice that bit string patterns cannot be nested.</p><p>Notice also that &quot;<code class="inline">B=&lt;&lt;1&gt;&gt;</code>&quot; is interpreted as &quot;<code class="inline">B =&lt; &lt;1&gt;&gt;</code>&quot; which is a syntax
│ │ │ │ +</span><span class="mi">14</span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="1504609037-23">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">:</span><span class="mi">7</span><span class="p" data-group-id="1504609037-23">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1504609037-24">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="1504609037-24">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">15&gt; </span><span class="p" data-group-id="1504609037-25">&lt;&lt;</span><span class="mi">16#123</span><span class="p">:</span><span class="mi">12</span><span class="o">/</span><span class="ss">little</span><span class="p" data-group-id="1504609037-25">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1504609037-26">&lt;&lt;</span><span class="mi">16#231</span><span class="p">:</span><span class="mi">12</span><span class="p" data-group-id="1504609037-26">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1504609037-27">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="1504609037-27">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1504609037-28">&lt;&lt;</span><span class="mi">35</span><span class="p">,</span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="1504609037-28">&gt;&gt;</span></code></pre><p>Notice that bit string patterns cannot be nested.</p><p>Notice also that &quot;<code class="inline">B=&lt;&lt;1&gt;&gt;</code>&quot; is interpreted as &quot;<code class="inline">B =&lt; &lt;1&gt;&gt;</code>&quot; which is a syntax
│ │ │ │  error. The correct way is to write a space after <code class="inline">=</code>: <code class="inline">B = &lt;&lt;1&gt;&gt;</code>.</p><p>More examples are provided in <a href="../../../lib/../system/doc/html/bit_syntax.xhtml">Programming Examples</a>.</p><h2 id="fun-expressions" class="section-heading">
│ │ │ │    <a href="#fun-expressions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Fun Expressions</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">fun</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0766370771-1">[</span><span class="n">Name</span><span class="p" data-group-id="0766370771-1">]</span><span class="p" data-group-id="0766370771-2">(</span><span class="n">Pattern11</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">Pattern1N</span><span class="p" data-group-id="0766370771-2">)</span><span class="w"> </span><span class="p" data-group-id="0766370771-3">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="0766370771-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6668491659-1">[</span><span class="n">Name</span><span class="p" data-group-id="6668491659-1">]</span><span class="p" data-group-id="6668491659-2">(</span><span class="n">Pattern11</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">Pattern1N</span><span class="p" data-group-id="6668491659-2">)</span><span class="w"> </span><span class="p" data-group-id="6668491659-3">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="6668491659-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0766370771-4">[</span><span class="n">Name</span><span class="p" data-group-id="0766370771-4">]</span><span class="p" data-group-id="0766370771-5">(</span><span class="n">PatternK1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">PatternKN</span><span class="p" data-group-id="0766370771-5">)</span><span class="w"> </span><span class="p" data-group-id="0766370771-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqK</span><span class="p" data-group-id="0766370771-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6668491659-4">[</span><span class="n">Name</span><span class="p" data-group-id="6668491659-4">]</span><span class="p" data-group-id="6668491659-5">(</span><span class="n">PatternK1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">PatternKN</span><span class="p" data-group-id="6668491659-5">)</span><span class="w"> </span><span class="p" data-group-id="6668491659-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqK</span><span class="p" data-group-id="6668491659-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                </span><span class="n">BodyK</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>A fun expression begins with the keyword <code class="inline">fun</code> and ends with the keyword <code class="inline">end</code>.
│ │ │ │  Between them is to be a function declaration, similar to a
│ │ │ │  <a href="ref_man_functions.xhtml#function-declaration-syntax">regular function declaration</a>,
│ │ │ │  except that the function name is optional and is to be a variable, if any.</p><p>Variables in a fun head shadow the function name and both shadow variables in
│ │ │ │  the function clause surrounding the fun expression. Variables bound in a fun
│ │ │ │ -body are local to the fun body.</p><p>The return value of the expression is the resulting fun.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5444851359-1">(</span><span class="n">X</span><span class="p" data-group-id="5444851359-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +body are local to the fun body.</p><p>The return value of the expression is the resulting fun.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="2840258451-1">(</span><span class="n">X</span><span class="p" data-group-id="2840258451-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.39074546</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">Fun1</span><span class="p" data-group-id="5444851359-2">(</span><span class="mi">2</span><span class="p" data-group-id="5444851359-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">Fun1</span><span class="p" data-group-id="2840258451-2">(</span><span class="mi">2</span><span class="p" data-group-id="2840258451-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="n">Fun2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5444851359-3">(</span><span class="n">X</span><span class="p" data-group-id="5444851359-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="o">&gt;=</span><span class="mi">5</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">gt</span><span class="p">;</span><span class="w"> </span><span class="p" data-group-id="5444851359-4">(</span><span class="n">X</span><span class="p" data-group-id="5444851359-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">lt</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="n">Fun2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="2840258451-3">(</span><span class="n">X</span><span class="p" data-group-id="2840258451-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="o">&gt;=</span><span class="mi">5</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">gt</span><span class="p">;</span><span class="w"> </span><span class="p" data-group-id="2840258451-4">(</span><span class="n">X</span><span class="p" data-group-id="2840258451-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">lt</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.39074546</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="n">Fun2</span><span class="p" data-group-id="5444851359-5">(</span><span class="mi">7</span><span class="p" data-group-id="5444851359-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="n">Fun2</span><span class="p" data-group-id="2840258451-5">(</span><span class="mi">7</span><span class="p" data-group-id="2840258451-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">gt</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="n">Fun3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="5444851359-6">(</span><span class="mi">1</span><span class="p" data-group-id="5444851359-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="5444851359-7">(</span><span class="n">X</span><span class="p" data-group-id="5444851359-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="5444851359-8">(</span><span class="n">X</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="5444851359-8">)</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="n">Fun3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="2840258451-6">(</span><span class="mi">1</span><span class="p" data-group-id="2840258451-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="2840258451-7">(</span><span class="n">X</span><span class="p" data-group-id="2840258451-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="2840258451-8">(</span><span class="n">X</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2840258451-8">)</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.39074546</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="n">Fun3</span><span class="p" data-group-id="5444851359-9">(</span><span class="mi">4</span><span class="p" data-group-id="5444851359-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="n">Fun3</span><span class="p" data-group-id="2840258451-9">(</span><span class="mi">4</span><span class="p" data-group-id="2840258451-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">24</span></code></pre><p>The following fun expressions are also allowed:</p><pre><code class="makeup erlang" translate="no"><span class="k">fun</span><span class="w"> </span><span class="n">Name</span><span class="o">/</span><span class="n">Arity</span><span class="w">
│ │ │ │  </span><span class="k">fun</span><span class="w"> </span><span class="n">Module</span><span class="p">:</span><span class="n">Name</span><span class="o">/</span><span class="n">Arity</span></code></pre><p>In <code class="inline">Name/Arity</code>, <code class="inline">Name</code> is an atom and <code class="inline">Arity</code> is an integer. <code class="inline">Name/Arity</code> must
│ │ │ │ -specify an existing local function. The expression is syntactic sugar for:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="6122705024-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="6122705024-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6122705024-2">(</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="6122705024-2">)</span><span class="w"> </span><span class="k">end</span></code></pre><p>In <code class="inline">Module:Name/Arity</code>, <code class="inline">Module</code> and <code class="inline">Name</code> are atoms and <code class="inline">Arity</code> is an
│ │ │ │ +specify an existing local function. The expression is syntactic sugar for:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="7434968938-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="7434968938-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="7434968938-2">(</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="7434968938-2">)</span><span class="w"> </span><span class="k">end</span></code></pre><p>In <code class="inline">Module:Name/Arity</code>, <code class="inline">Module</code> and <code class="inline">Name</code> are atoms and <code class="inline">Arity</code> is an
│ │ │ │  integer. <code class="inline">Module</code>, <code class="inline">Name</code>, and <code class="inline">Arity</code> can also be variables. A fun defined in
│ │ │ │  this way refers to the function <code class="inline">Name</code> with arity <code class="inline">Arity</code> in the <em>latest</em>
│ │ │ │  version of module <code class="inline">Module</code>. A fun defined in this way is not dependent on the
│ │ │ │  code for the module in which it is defined.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP R15, <code class="inline">Module</code>, <code class="inline">Name</code>, and <code class="inline">Arity</code> were not allowed to be
│ │ │ │  variables.</p></section><p>More examples are provided in <a href="../../../lib/../system/doc/html/funs.xhtml">Programming Examples</a>.</p><h2 id="catch-and-throw" class="section-heading">
│ │ │ │    <a href="#catch-and-throw" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │ @@ -905,35 +905,35 @@
│ │ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">catch</span><span class="w"> </span><span class="n">Expr</span></code></pre><p>Returns the value of <code class="inline">Expr</code> unless an exception is raised during the evaluation. In
│ │ │ │  that case, the exception is caught. The return value depends on the class of the
│ │ │ │  exception:</p><ul><li><p><strong><code class="inline">error</code></strong> (a run-time error or the code called <a href="../../../lib/../erts/doc/html/erlang.html#error/1"><code class="inline">error(Term)</code></a>) -
│ │ │ │  <code class="inline">{'EXIT',{Reason,Stack}}</code> is returned.</p></li><li><p><strong><code class="inline">exit</code></strong> (the code called <a href="../../../lib/../erts/doc/html/erlang.html#exit/1"><code class="inline">exit(Term)</code></a>) - <code class="inline">{'EXIT',Term}</code> is returned.</p></li><li><p><strong><code class="inline">throw</code></strong> (the code called <a href="../../../lib/../erts/doc/html/erlang.html#throw/1"><code class="inline">throw(Term)</code></a>) - <code class="inline">Term</code> is returned.</p></li></ul><p><code class="inline">Reason</code> depends on the type of error that occurred, and <code class="inline">Stack</code> is the stack of
│ │ │ │  recent function calls, see <a href="errors.xhtml#exit_reasons">Exit Reasons</a>.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="k">catch</span><span class="w"> </span><span class="mi">1</span><span class="o">+</span><span class="mi">2</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">2&gt; </span><span class="k">catch</span><span class="w"> </span><span class="mi">1</span><span class="o">+</span><span class="ss">a</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1462495227-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="1462495227-2">{</span><span class="ss">badarith</span><span class="p">,</span><span class="p" data-group-id="1462495227-3">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1462495227-3">]</span><span class="p" data-group-id="1462495227-2">}</span><span class="p" data-group-id="1462495227-1">}</span></code></pre><p>The BIF <a href="../../../lib/../erts/doc/html/erlang.html#throw/1"><code class="inline">throw(Any)</code></a> can be used for non-local return from a
│ │ │ │ -function. It must be evaluated within a <code class="inline">catch</code>, which returns the value <code class="inline">Any</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="9802305455-1">(</span><span class="ss">hello</span><span class="p" data-group-id="9802305455-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9900301663-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="9900301663-2">{</span><span class="ss">badarith</span><span class="p">,</span><span class="p" data-group-id="9900301663-3">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="9900301663-3">]</span><span class="p" data-group-id="9900301663-2">}</span><span class="p" data-group-id="9900301663-1">}</span></code></pre><p>The BIF <a href="../../../lib/../erts/doc/html/erlang.html#throw/1"><code class="inline">throw(Any)</code></a> can be used for non-local return from a
│ │ │ │ +function. It must be evaluated within a <code class="inline">catch</code>, which returns the value <code class="inline">Any</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="9601135854-1">(</span><span class="ss">hello</span><span class="p" data-group-id="9601135854-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span></code></pre><p>If <a href="../../../lib/../erts/doc/html/erlang.html#throw/1"><code class="inline">throw/1</code></a> is not evaluated within a catch, a <code class="inline">nocatch</code> run-time
│ │ │ │  error occurs.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 24, the <code class="inline">catch</code> operator had the lowest precedence, making
│ │ │ │ -it necessary to add parentheses when combining it with the <code class="inline">match</code> operator:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3504721329-1">(</span><span class="k">catch</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="3504721329-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +it necessary to add parentheses when combining it with the <code class="inline">match</code> operator:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3558896155-1">(</span><span class="k">catch</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="3558896155-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">42</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">2&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">42</span></code></pre><p>Starting from Erlang/OTP 24, the parentheses can be omitted:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="mi">42</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">42</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">2&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">42</span></code></pre></section><h2 id="try" class="section-heading">
│ │ │ │    <a href="#try" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Try</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w">
│ │ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ │ -    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="4944317928-1">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="4944317928-1">]</span><span class="w"> </span><span class="p" data-group-id="4944317928-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="4944317928-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="5819724485-1">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="5819724485-1">]</span><span class="w"> </span><span class="p" data-group-id="5819724485-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="5819724485-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">ExceptionBody1</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="4944317928-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="4944317928-3">]</span><span class="w"> </span><span class="p" data-group-id="4944317928-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="4944317928-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="5819724485-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="5819724485-3">]</span><span class="w"> </span><span class="p" data-group-id="5819724485-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="5819724485-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">ExceptionBodyN</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>This is an enhancement of <a href="expressions.xhtml#catch-and-throw">catch</a>. It gives the
│ │ │ │  possibility to:</p><ul><li>Distinguish between different exception classes.</li><li>Choose to handle only the desired ones.</li><li>Pass the others on to an enclosing <code class="inline">try</code> or <code class="inline">catch</code>, or to default error
│ │ │ │  handling.</li></ul><p>Notice that although the keyword <code class="inline">catch</code> is used in the <code class="inline">try</code> expression, there
│ │ │ │  is not a <code class="inline">catch</code> expression within the <code class="inline">try</code> expression.</p><p>It returns the value of <code class="inline">Exprs</code> (a sequence of expressions <code class="inline">Expr1, ..., ExprN</code>)
│ │ │ │  unless an exception occurs during the evaluation. In that case the exception is
│ │ │ │  caught and the patterns <code class="inline">ExceptionPattern</code> with the right exception class
│ │ │ │ @@ -943,47 +943,47 @@
│ │ │ │  stack trace is bound to the variable when the corresponding <code class="inline">ExceptionPattern</code>
│ │ │ │  matches.</p><p>If an exception occurs during evaluation of <code class="inline">Exprs</code> but there is no matching
│ │ │ │  <code class="inline">ExceptionPattern</code> of the right <code class="inline">Class</code> with a true guard sequence, the
│ │ │ │  exception is passed on as if <code class="inline">Exprs</code> had not been enclosed in a <code class="inline">try</code>
│ │ │ │  expression.</p><p>If an exception occurs during evaluation of <code class="inline">ExceptionBody</code>, it is not caught.</p><p>It is allowed to omit <code class="inline">Class</code> and <code class="inline">Stacktrace</code>. An omitted <code class="inline">Class</code> is shorthand
│ │ │ │  for <code class="inline">throw</code>:</p><pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w">
│ │ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ │ -    </span><span class="n">ExceptionPattern1</span><span class="w"> </span><span class="p" data-group-id="9221344688-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="9221344688-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">ExceptionPattern1</span><span class="w"> </span><span class="p" data-group-id="5118910489-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="5118910489-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">ExceptionBody1</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">ExceptionPatternN</span><span class="w"> </span><span class="p" data-group-id="9221344688-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="9221344688-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">ExceptionPatternN</span><span class="w"> </span><span class="p" data-group-id="5118910489-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="5118910489-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">ExceptionBodyN</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>The <code class="inline">try</code> expression can have an <code class="inline">of</code> section:</p><pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="4898325881-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="4898325881-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="2491990701-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="2491990701-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="4898325881-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="4898325881-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="2491990701-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="2491990701-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ │ -    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="4898325881-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="4898325881-3">]</span><span class="w"> </span><span class="p" data-group-id="4898325881-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="4898325881-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="2491990701-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="2491990701-3">]</span><span class="w"> </span><span class="p" data-group-id="2491990701-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="2491990701-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">ExceptionBody1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="4898325881-5">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="4898325881-5">]</span><span class="w"> </span><span class="p" data-group-id="4898325881-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="4898325881-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="2491990701-5">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="2491990701-5">]</span><span class="w"> </span><span class="p" data-group-id="2491990701-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="2491990701-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">ExceptionBodyN</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>If the evaluation of <code class="inline">Exprs</code> succeeds without an exception, the patterns
│ │ │ │  <code class="inline">Pattern</code> are sequentially matched against the result in the same way as for a
│ │ │ │  <a href="expressions.xhtml#case">case</a> expression, except that if the matching fails, a
│ │ │ │  <code class="inline">try_clause</code> run-time error occurs instead of a <code class="inline">case_clause</code>.</p><p>Only exceptions occurring during the evaluation of <code class="inline">Exprs</code> can be caught by the
│ │ │ │  <code class="inline">catch</code> section. Exceptions occurring in a <code class="inline">Body</code> or due to a failed match are
│ │ │ │  not caught.</p><p>The <code class="inline">try</code> expression can also be augmented with an <code class="inline">after</code> section, intended to
│ │ │ │  be used for cleanup with side effects:</p><pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="0511252880-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="0511252880-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="7046091004-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="7046091004-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="0511252880-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="0511252880-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="7046091004-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="7046091004-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ │ -    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="0511252880-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="0511252880-3">]</span><span class="w"> </span><span class="p" data-group-id="0511252880-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="0511252880-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="7046091004-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="7046091004-3">]</span><span class="w"> </span><span class="p" data-group-id="7046091004-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="7046091004-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">ExceptionBody1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="0511252880-5">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="0511252880-5">]</span><span class="w"> </span><span class="p" data-group-id="0511252880-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="0511252880-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="7046091004-5">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="7046091004-5">]</span><span class="w"> </span><span class="p" data-group-id="7046091004-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="7046091004-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">ExceptionBodyN</span><span class="w">
│ │ │ │  </span><span class="k">after</span><span class="w">
│ │ │ │      </span><span class="n">AfterBody</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p><code class="inline">AfterBody</code> is evaluated after either <code class="inline">Body</code> or <code class="inline">ExceptionBody</code>, no matter which
│ │ │ │  one. The evaluated value of <code class="inline">AfterBody</code> is lost; the return value of the <code class="inline">try</code>
│ │ │ │  expression is the same with an <code class="inline">after</code> section as without.</p><p>Even if an exception occurs during evaluation of <code class="inline">Body</code> or <code class="inline">ExceptionBody</code>,
│ │ │ │  <code class="inline">AfterBody</code> is evaluated. In this case the exception is passed on after
│ │ │ │ @@ -1006,40 +1006,40 @@
│ │ │ │          </span><span class="n">ExceptionBody</span><span class="w">
│ │ │ │  </span><span class="k">after</span><span class="w">
│ │ │ │      </span><span class="n">AfterBody</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w"> </span><span class="k">after</span><span class="w"> </span><span class="n">AfterBody</span><span class="w"> </span><span class="k">end</span></code></pre><p>Next is an example of using <code class="inline">after</code>. This closes the file, even in the event of
│ │ │ │  exceptions in <a href="../../../lib/kernel/doc/html/file.html#read/2"><code class="inline">file:read/2</code></a> or in <a href="../../../lib/../erts/doc/html/erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a>. The
│ │ │ │ -exceptions are the same as without the <code class="inline">try</code>...<code class="inline">after</code>...<code class="inline">end</code> expression:</p><pre><code class="makeup erlang" translate="no"><span class="nf">termize_file</span><span class="p" data-group-id="3351084535-1">(</span><span class="n">Name</span><span class="p" data-group-id="3351084535-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3351084535-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="n">F</span><span class="p" data-group-id="3351084535-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="3351084535-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3351084535-4">[</span><span class="ss">read</span><span class="p">,</span><span class="ss">binary</span><span class="p" data-group-id="3351084535-4">]</span><span class="p" data-group-id="3351084535-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +exceptions are the same as without the <code class="inline">try</code>...<code class="inline">after</code>...<code class="inline">end</code> expression:</p><pre><code class="makeup erlang" translate="no"><span class="nf">termize_file</span><span class="p" data-group-id="9358619083-1">(</span><span class="n">Name</span><span class="p" data-group-id="9358619083-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9358619083-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="n">F</span><span class="p" data-group-id="9358619083-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="9358619083-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9358619083-4">[</span><span class="ss">read</span><span class="p">,</span><span class="ss">binary</span><span class="p" data-group-id="9358619083-4">]</span><span class="p" data-group-id="9358619083-3">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">try</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3351084535-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="n">Bin</span><span class="p" data-group-id="3351084535-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="3351084535-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">1024</span><span class="o">*</span><span class="mi">1024</span><span class="p" data-group-id="3351084535-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="nf">binary_to_term</span><span class="p" data-group-id="3351084535-7">(</span><span class="n">Bin</span><span class="p" data-group-id="3351084535-7">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9358619083-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="n">Bin</span><span class="p" data-group-id="9358619083-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="9358619083-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">1024</span><span class="o">*</span><span class="mi">1024</span><span class="p" data-group-id="9358619083-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="nf">binary_to_term</span><span class="p" data-group-id="9358619083-7">(</span><span class="n">Bin</span><span class="p" data-group-id="9358619083-7">)</span><span class="w">
│ │ │ │      </span><span class="k">after</span><span class="w">
│ │ │ │ -        </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="3351084535-8">(</span><span class="n">F</span><span class="p" data-group-id="3351084535-8">)</span><span class="w">
│ │ │ │ +        </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="9358619083-8">(</span><span class="n">F</span><span class="p" data-group-id="9358619083-8">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Next is an example of using <code class="inline">try</code> to emulate <code class="inline">catch Expr</code>:</p><pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Expr</span><span class="w">
│ │ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ │      </span><span class="nc">throw</span><span class="p">:</span><span class="n">Term</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Term</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="nc">exit</span><span class="p">:</span><span class="n">Reason</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7986475628-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="n">Reason</span><span class="p" data-group-id="7986475628-1">}</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="nc">error</span><span class="p">:</span><span class="n">Reason</span><span class="p">:</span><span class="n">Stk</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7986475628-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="7986475628-3">{</span><span class="n">Reason</span><span class="p">,</span><span class="n">Stk</span><span class="p" data-group-id="7986475628-3">}</span><span class="p" data-group-id="7986475628-2">}</span><span class="w">
│ │ │ │ +    </span><span class="nc">exit</span><span class="p">:</span><span class="n">Reason</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0618668422-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="n">Reason</span><span class="p" data-group-id="0618668422-1">}</span><span class="p">;</span><span class="w">
│ │ │ │ +    </span><span class="nc">error</span><span class="p">:</span><span class="n">Reason</span><span class="p">:</span><span class="n">Stk</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0618668422-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="0618668422-3">{</span><span class="n">Reason</span><span class="p">,</span><span class="n">Stk</span><span class="p" data-group-id="0618668422-3">}</span><span class="p" data-group-id="0618668422-2">}</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>Variables bound in the various parts of these expressions have different scopes.
│ │ │ │  Variables bound just after the <code class="inline">try</code> keyword are:</p><ul><li>bound in the <code class="inline">of</code> section</li><li>unsafe in both the <code class="inline">catch</code> and <code class="inline">after</code> sections, as well as after the whole
│ │ │ │  construct</li></ul><p>Variables bound in the <code class="inline">of</code> section are:</p><ul><li>unbound in the <code class="inline">catch</code> section</li><li>unsafe in the <code class="inline">after</code> section, as well as after the whole construct</li></ul><p>Variables bound in the <code class="inline">catch</code> section are unsafe in the <code class="inline">after</code> section, as
│ │ │ │  well as after the whole construct.</p><p>Variables bound in the <code class="inline">after</code> section are unsafe after the whole construct.</p><h2 id="parenthesized-expressions" class="section-heading">
│ │ │ │    <a href="#parenthesized-expressions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Parenthesized Expressions</span>
│ │ │ │  </h2>
│ │ │ │ -<pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0157969140-1">(</span><span class="n">Expr</span><span class="p" data-group-id="0157969140-1">)</span></code></pre><p>Parenthesized expressions are useful to override
│ │ │ │ +<pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2872821682-1">(</span><span class="n">Expr</span><span class="p" data-group-id="2872821682-1">)</span></code></pre><p>Parenthesized expressions are useful to override
│ │ │ │  <a href="expressions.xhtml#prec">operator precedences</a>, for example, in arithmetic
│ │ │ │  expressions:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">7</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="5030826327-1">(</span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="5030826327-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="7369142205-1">(</span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="7369142205-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">9</span></code></pre><h2 id="block-expressions" class="section-heading">
│ │ │ │    <a href="#block-expressions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Block Expressions</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">begin</span><span class="w">
│ │ │ │ @@ -1051,82 +1051,82 @@
│ │ │ │    <a href="#comprehensions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Comprehensions</span>
│ │ │ │  </h2>
│ │ │ │  <p>Comprehensions provide a succinct notation for iterating over one or more terms
│ │ │ │  and constructing a new term. Comprehensions come in three different flavors,
│ │ │ │ -depending on the type of term they build.</p><p>List comprehensions construct lists. They have the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6761020264-1">[</span><span class="n">Expr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="p" data-group-id="6761020264-1">]</span></code></pre><p>Here, <code class="inline">Expr</code> is an arbitrary expression, and each <code class="inline">Qualifier</code> is either a
│ │ │ │ +depending on the type of term they build.</p><p>List comprehensions construct lists. They have the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4217799627-1">[</span><span class="n">Expr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="p" data-group-id="4217799627-1">]</span></code></pre><p>Here, <code class="inline">Expr</code> is an arbitrary expression, and each <code class="inline">Qualifier</code> is either a
│ │ │ │  <strong>generator</strong> or a <strong>filter</strong>.</p><p>Bit string comprehensions construct bit strings or binaries. They have the
│ │ │ │ -following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3599794798-1">&lt;&lt;</span><span class="w"> </span><span class="n">BitStringExpr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="w"> </span><span class="p" data-group-id="3599794798-1">&gt;&gt;</span></code></pre><p><code class="inline">BitStringExpr</code> is an expression that evaluates to a bit string. If
│ │ │ │ +following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7316104734-1">&lt;&lt;</span><span class="w"> </span><span class="n">BitStringExpr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="w"> </span><span class="p" data-group-id="7316104734-1">&gt;&gt;</span></code></pre><p><code class="inline">BitStringExpr</code> is an expression that evaluates to a bit string. If
│ │ │ │  <code class="inline">BitStringExpr</code> is a function call, it must be enclosed in parentheses. Each
│ │ │ │ -<code class="inline">Qualifier</code> is either a <strong>generator</strong> or a <strong>filter</strong>.</p><p>Map comprehensions construct maps. They have the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5190403458-1">#{</span><span class="n">KeyExpr</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">ValueExpr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="p" data-group-id="5190403458-1">}</span></code></pre><p>Here, <code class="inline">KeyExpr</code> and <code class="inline">ValueExpr</code> are arbitrary expressions, and each <code class="inline">Qualifier</code>
│ │ │ │ +<code class="inline">Qualifier</code> is either a <strong>generator</strong> or a <strong>filter</strong>.</p><p>Map comprehensions construct maps. They have the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5967475414-1">#{</span><span class="n">KeyExpr</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">ValueExpr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="p" data-group-id="5967475414-1">}</span></code></pre><p>Here, <code class="inline">KeyExpr</code> and <code class="inline">ValueExpr</code> are arbitrary expressions, and each <code class="inline">Qualifier</code>
│ │ │ │  is either a <strong>generator</strong> or a <strong>filter</strong>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Map comprehensions and map generators were introduced in Erlang/OTP 26.</p></section><p>There are four kinds of generators. Three of them have a relaxed and a strict
│ │ │ │  variant. The fourth kind of generator, zip generator, is composed of two or
│ │ │ │  more non-zip generators.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Strict generators and zip generators were introduced in Erlang/OTP 28.
│ │ │ │  Using strict generators is a better practice when either strict or relaxed
│ │ │ │  generators work. More details are in
│ │ │ │  <a href="../../../lib/../system/doc/html/list_comprehensions.xhtml">Programming Examples</a>.</p></section><p>A <em>list generator</em> has the following syntax for relaxed:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">ListExpr</span></code></pre><p>and strict variant:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">ListExpr</span></code></pre><p>where <code class="inline">ListExpr</code> is an expression that evaluates to a list of terms.</p><p>A <em>bit string generator</em> has the following syntax for relaxed:</p><pre><code class="makeup erlang" translate="no"><span class="n">BitstringPattern</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">BitStringExpr</span></code></pre><p>and strict variant:</p><pre><code class="makeup erlang" translate="no"><span class="n">BitstringPattern</span><span class="w"> </span><span class="o">&lt;:=</span><span class="w"> </span><span class="n">BitStringExpr</span></code></pre><p>where <code class="inline">BitStringExpr</code> is an expression that evaluates to a bit string.</p><p>A <em>map generator</em> has the following syntax for relaxed:</p><pre><code class="makeup erlang" translate="no"><span class="n">KeyPattern</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">ValuePattern</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">MapExpression</span></code></pre><p>and strict variant:</p><pre><code class="makeup erlang" translate="no"><span class="n">KeyPattern</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">ValuePattern</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">MapExpression</span></code></pre><p>where <code class="inline">MapExpression</code> is an expression that evaluates to a map or a map iterator
│ │ │ │  obtained by calling <a href="../../../lib/stdlib/doc/html/maps.html#iterator/1"><code class="inline">maps:iterator/1</code></a> or <a href="../../../lib/stdlib/doc/html/maps.html#iterator/2"><code class="inline">maps:iterator/2</code></a>.</p><p>A <em>zip generator</em> has the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">Generator_1</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Generator_n</span></code></pre><p>where every <code class="inline">Generator_i</code> is a non-zip generator. Generators within a zip
│ │ │ │  generator are treated as one generator and evaluated in parallel.</p><p>A <em>filter</em> is an expression that evaluates to <code class="inline">true</code> or <code class="inline">false</code>.</p><p>The variables in the generator patterns shadow previously bound variables,
│ │ │ │  including variables bound in a previous generator pattern.</p><p>Variables bound in a generator expression are not visible outside the
│ │ │ │ -expression:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="1571584754-1">[</span><span class="p" data-group-id="1571584754-2">{</span><span class="n">E</span><span class="p">,</span><span class="n">L</span><span class="p" data-group-id="1571584754-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="o">=</span><span class="p" data-group-id="1571584754-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1571584754-3">]</span><span class="p" data-group-id="1571584754-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +expression:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8080301446-1">[</span><span class="p" data-group-id="8080301446-2">{</span><span class="n">E</span><span class="p">,</span><span class="n">L</span><span class="p" data-group-id="8080301446-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="o">=</span><span class="p" data-group-id="8080301446-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8080301446-3">]</span><span class="p" data-group-id="8080301446-1">]</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">* 1:5: variable &#39;L&#39; is unbound</span></code></pre><p>A <strong>list comprehension</strong> returns a list, where the list elements are the result
│ │ │ │  of evaluating <code class="inline">Expr</code> for each combination of generator elements for which all
│ │ │ │  filters are true.</p><p>A <strong>bit string comprehension</strong> returns a bit string, which is created by
│ │ │ │  concatenating the results of evaluating <code class="inline">BitStringExpr</code> for each combination of
│ │ │ │  bit string generator elements for which all filters are true.</p><p>A <strong>map comprehension</strong> returns a map, where the map elements are the result of
│ │ │ │  evaluating <code class="inline">KeyExpr</code> and <code class="inline">ValueExpr</code> for each combination of generator elements
│ │ │ │  for which all filters are true. If the key expressions are not unique, the last
│ │ │ │ -occurrence is stored in the map.</p><p><strong>Examples:</strong></p><p>Multiplying each element in a list by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="6620051876-1">[</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="6620051876-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6620051876-2">]</span><span class="p" data-group-id="6620051876-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6620051876-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="6620051876-3">]</span></code></pre><p>Multiplying each byte in a binary by two, returning a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4490142268-1">[</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="4490142268-2">&lt;&lt;</span><span class="n">X</span><span class="p" data-group-id="4490142268-2">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;:=</span><span class="w"> </span><span class="p" data-group-id="4490142268-3">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4490142268-3">&gt;&gt;</span><span class="p" data-group-id="4490142268-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4490142268-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="4490142268-4">]</span></code></pre><p>Multiplying each byte in a binary by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="6243886792-1">&lt;&lt;</span><span class="w"> </span><span class="p" data-group-id="6243886792-2">&lt;&lt;</span><span class="p" data-group-id="6243886792-3">(</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="p" data-group-id="6243886792-3">)</span><span class="p" data-group-id="6243886792-2">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="6243886792-4">&lt;&lt;</span><span class="n">X</span><span class="p" data-group-id="6243886792-4">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;:=</span><span class="w"> </span><span class="p" data-group-id="6243886792-5">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6243886792-5">&gt;&gt;</span><span class="w"> </span><span class="p" data-group-id="6243886792-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6243886792-6">&lt;&lt;</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="6243886792-6">&gt;&gt;</span></code></pre><p>Multiplying each element in a list by two, returning a binary:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9053598098-1">&lt;&lt;</span><span class="w"> </span><span class="p" data-group-id="9053598098-2">&lt;&lt;</span><span class="p" data-group-id="9053598098-3">(</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="p" data-group-id="9053598098-3">)</span><span class="p" data-group-id="9053598098-2">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="9053598098-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9053598098-4">]</span><span class="w"> </span><span class="p" data-group-id="9053598098-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9053598098-5">&lt;&lt;</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="9053598098-5">&gt;&gt;</span></code></pre><p>Creating a mapping from an integer to its square:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8022392440-1">#{</span><span class="n">X</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">*</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="8022392440-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8022392440-2">]</span><span class="p" data-group-id="8022392440-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8022392440-3">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="8022392440-3">}</span></code></pre><p>Multiplying the value of each element in a map by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="6411500220-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="o">*</span><span class="n">V</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="6411500220-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="6411500220-2">}</span><span class="p" data-group-id="6411500220-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6411500220-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p" data-group-id="6411500220-3">}</span></code></pre><p>Filtering a list, keeping odd numbers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="1088306500-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="1088306500-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="1088306500-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="1088306500-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1088306500-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="1088306500-3">]</span></code></pre><p>Filtering a list, keeping only elements that match:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9311732297-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="9311732297-2">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9311732297-2">}</span><span class="o">=</span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="9311732297-3">[</span><span class="p" data-group-id="9311732297-4">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9311732297-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9311732297-5">[</span><span class="ss">a</span><span class="p" data-group-id="9311732297-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9311732297-6">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="9311732297-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9311732297-7">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9311732297-7">}</span><span class="p" data-group-id="9311732297-3">]</span><span class="p" data-group-id="9311732297-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9311732297-8">[</span><span class="p" data-group-id="9311732297-9">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9311732297-9">}</span><span class="p">,</span><span class="p" data-group-id="9311732297-10">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9311732297-10">}</span><span class="p" data-group-id="9311732297-8">]</span></code></pre><p>Filtering a list, crashing when the element is not a 2-tuple:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="2477425725-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="2477425725-2">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="2477425725-2">}</span><span class="o">=</span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="2477425725-3">[</span><span class="p" data-group-id="2477425725-4">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="2477425725-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2477425725-5">[</span><span class="ss">a</span><span class="p" data-group-id="2477425725-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2477425725-6">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="2477425725-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2477425725-7">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2477425725-7">}</span><span class="p" data-group-id="2477425725-3">]</span><span class="p" data-group-id="2477425725-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="gt">** exception error: no match of right hand side value [a]</span></code></pre><p>Combining elements from two list generators:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3432076982-1">[</span><span class="p" data-group-id="3432076982-2">{</span><span class="n">P</span><span class="p">,</span><span class="n">Q</span><span class="p" data-group-id="3432076982-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="3432076982-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3432076982-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="3432076982-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3432076982-4">]</span><span class="p" data-group-id="3432076982-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3432076982-5">[</span><span class="p" data-group-id="3432076982-6">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3432076982-6">}</span><span class="p">,</span><span class="p" data-group-id="3432076982-7">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3432076982-7">}</span><span class="p">,</span><span class="p" data-group-id="3432076982-8">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3432076982-8">}</span><span class="p">,</span><span class="p" data-group-id="3432076982-9">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3432076982-9">}</span><span class="p">,</span><span class="p" data-group-id="3432076982-10">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3432076982-10">}</span><span class="p">,</span><span class="p" data-group-id="3432076982-11">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3432076982-11">}</span><span class="p" data-group-id="3432076982-5">]</span></code></pre><p>Combining elements from two list generators, using a zip generator:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="0745074674-1">[</span><span class="p" data-group-id="0745074674-2">{</span><span class="n">P</span><span class="p">,</span><span class="n">Q</span><span class="p" data-group-id="0745074674-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="0745074674-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="0745074674-3">]</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="0745074674-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0745074674-4">]</span><span class="p" data-group-id="0745074674-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0745074674-5">[</span><span class="p" data-group-id="0745074674-6">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0745074674-6">}</span><span class="p">,</span><span class="p" data-group-id="0745074674-7">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0745074674-7">}</span><span class="p">,</span><span class="p" data-group-id="0745074674-8">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0745074674-8">}</span><span class="p" data-group-id="0745074674-5">]</span></code></pre><p>Combining elements from two list generators using a zip generator, filtering
│ │ │ │ -out odd numbers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8563639229-1">[</span><span class="p" data-group-id="8563639229-2">{</span><span class="n">P</span><span class="p">,</span><span class="n">Q</span><span class="p" data-group-id="8563639229-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="8563639229-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="8563639229-3">]</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="8563639229-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8563639229-4">]</span><span class="p">,</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="8563639229-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8563639229-5">[</span><span class="p" data-group-id="8563639229-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8563639229-6">}</span><span class="p" data-group-id="8563639229-5">]</span></code></pre><p>Filtering out non-matching elements from two lists.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7358883717-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="7358883717-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7358883717-2">]</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="7358883717-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7358883717-3">]</span><span class="p" data-group-id="7358883717-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7358883717-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7358883717-4">]</span></code></pre><p>More examples are provided in
│ │ │ │ +occurrence is stored in the map.</p><p><strong>Examples:</strong></p><p>Multiplying each element in a list by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4382582229-1">[</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="4382582229-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4382582229-2">]</span><span class="p" data-group-id="4382582229-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4382582229-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="4382582229-3">]</span></code></pre><p>Multiplying each byte in a binary by two, returning a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="6023515905-1">[</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="6023515905-2">&lt;&lt;</span><span class="n">X</span><span class="p" data-group-id="6023515905-2">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;:=</span><span class="w"> </span><span class="p" data-group-id="6023515905-3">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6023515905-3">&gt;&gt;</span><span class="p" data-group-id="6023515905-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6023515905-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="6023515905-4">]</span></code></pre><p>Multiplying each byte in a binary by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7356007993-1">&lt;&lt;</span><span class="w"> </span><span class="p" data-group-id="7356007993-2">&lt;&lt;</span><span class="p" data-group-id="7356007993-3">(</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="p" data-group-id="7356007993-3">)</span><span class="p" data-group-id="7356007993-2">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="7356007993-4">&lt;&lt;</span><span class="n">X</span><span class="p" data-group-id="7356007993-4">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;:=</span><span class="w"> </span><span class="p" data-group-id="7356007993-5">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7356007993-5">&gt;&gt;</span><span class="w"> </span><span class="p" data-group-id="7356007993-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7356007993-6">&lt;&lt;</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7356007993-6">&gt;&gt;</span></code></pre><p>Multiplying each element in a list by two, returning a binary:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="0046715536-1">&lt;&lt;</span><span class="w"> </span><span class="p" data-group-id="0046715536-2">&lt;&lt;</span><span class="p" data-group-id="0046715536-3">(</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="p" data-group-id="0046715536-3">)</span><span class="p" data-group-id="0046715536-2">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="0046715536-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0046715536-4">]</span><span class="w"> </span><span class="p" data-group-id="0046715536-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0046715536-5">&lt;&lt;</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="0046715536-5">&gt;&gt;</span></code></pre><p>Creating a mapping from an integer to its square:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="6486526880-1">#{</span><span class="n">X</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">*</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="6486526880-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6486526880-2">]</span><span class="p" data-group-id="6486526880-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6486526880-3">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="6486526880-3">}</span></code></pre><p>Multiplying the value of each element in a map by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5879323853-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="o">*</span><span class="n">V</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="5879323853-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="5879323853-2">}</span><span class="p" data-group-id="5879323853-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5879323853-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p" data-group-id="5879323853-3">}</span></code></pre><p>Filtering a list, keeping odd numbers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="1349545769-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="1349545769-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="1349545769-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="1349545769-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1349545769-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="1349545769-3">]</span></code></pre><p>Filtering a list, keeping only elements that match:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="6755103854-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="6755103854-2">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6755103854-2">}</span><span class="o">=</span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="6755103854-3">[</span><span class="p" data-group-id="6755103854-4">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6755103854-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6755103854-5">[</span><span class="ss">a</span><span class="p" data-group-id="6755103854-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6755103854-6">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="6755103854-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6755103854-7">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6755103854-7">}</span><span class="p" data-group-id="6755103854-3">]</span><span class="p" data-group-id="6755103854-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6755103854-8">[</span><span class="p" data-group-id="6755103854-9">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6755103854-9">}</span><span class="p">,</span><span class="p" data-group-id="6755103854-10">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6755103854-10">}</span><span class="p" data-group-id="6755103854-8">]</span></code></pre><p>Filtering a list, crashing when the element is not a 2-tuple:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7379709126-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="7379709126-2">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="7379709126-2">}</span><span class="o">=</span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="7379709126-3">[</span><span class="p" data-group-id="7379709126-4">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7379709126-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7379709126-5">[</span><span class="ss">a</span><span class="p" data-group-id="7379709126-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7379709126-6">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="7379709126-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7379709126-7">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7379709126-7">}</span><span class="p" data-group-id="7379709126-3">]</span><span class="p" data-group-id="7379709126-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gt">** exception error: no match of right hand side value [a]</span></code></pre><p>Combining elements from two list generators:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7517220495-1">[</span><span class="p" data-group-id="7517220495-2">{</span><span class="n">P</span><span class="p">,</span><span class="n">Q</span><span class="p" data-group-id="7517220495-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="7517220495-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="7517220495-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="7517220495-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7517220495-4">]</span><span class="p" data-group-id="7517220495-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7517220495-5">[</span><span class="p" data-group-id="7517220495-6">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="7517220495-6">}</span><span class="p">,</span><span class="p" data-group-id="7517220495-7">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7517220495-7">}</span><span class="p">,</span><span class="p" data-group-id="7517220495-8">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="7517220495-8">}</span><span class="p">,</span><span class="p" data-group-id="7517220495-9">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7517220495-9">}</span><span class="p">,</span><span class="p" data-group-id="7517220495-10">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="7517220495-10">}</span><span class="p">,</span><span class="p" data-group-id="7517220495-11">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7517220495-11">}</span><span class="p" data-group-id="7517220495-5">]</span></code></pre><p>Combining elements from two list generators, using a zip generator:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7571966828-1">[</span><span class="p" data-group-id="7571966828-2">{</span><span class="n">P</span><span class="p">,</span><span class="n">Q</span><span class="p" data-group-id="7571966828-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="7571966828-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="7571966828-3">]</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="7571966828-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7571966828-4">]</span><span class="p" data-group-id="7571966828-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7571966828-5">[</span><span class="p" data-group-id="7571966828-6">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="7571966828-6">}</span><span class="p">,</span><span class="p" data-group-id="7571966828-7">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7571966828-7">}</span><span class="p">,</span><span class="p" data-group-id="7571966828-8">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7571966828-8">}</span><span class="p" data-group-id="7571966828-5">]</span></code></pre><p>Combining elements from two list generators using a zip generator, filtering
│ │ │ │ +out odd numbers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9668898957-1">[</span><span class="p" data-group-id="9668898957-2">{</span><span class="n">P</span><span class="p">,</span><span class="n">Q</span><span class="p" data-group-id="9668898957-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="9668898957-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="9668898957-3">]</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="9668898957-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9668898957-4">]</span><span class="p">,</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="9668898957-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9668898957-5">[</span><span class="p" data-group-id="9668898957-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9668898957-6">}</span><span class="p" data-group-id="9668898957-5">]</span></code></pre><p>Filtering out non-matching elements from two lists.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="6184080003-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="6184080003-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="6184080003-2">]</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="6184080003-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="6184080003-3">]</span><span class="p" data-group-id="6184080003-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6184080003-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6184080003-4">]</span></code></pre><p>More examples are provided in
│ │ │ │  <a href="../../../lib/../system/doc/html/list_comprehensions.xhtml">Programming Examples</a>.</p><p>When there are no generators, a comprehension returns either a term constructed
│ │ │ │  from a single element (the result of evaluating <code class="inline">Expr</code>) if all filters are true,
│ │ │ │  or a term constructed from no elements (that is, <code class="inline">[]</code> for list comprehension,
│ │ │ │ -<code class="inline">&lt;&lt;&gt;&gt;</code> for a bit string comprehension, and <code class="inline">#{}</code> for a map comprehension).</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="1986737007-1">[</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="1986737007-2">(</span><span class="mi">2</span><span class="p" data-group-id="1986737007-2">)</span><span class="p" data-group-id="1986737007-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1986737007-3">[</span><span class="mi">2</span><span class="p" data-group-id="1986737007-3">]</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="1986737007-4">[</span><span class="ss">x</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="1986737007-5">(</span><span class="ss">x</span><span class="p" data-group-id="1986737007-5">)</span><span class="p" data-group-id="1986737007-4">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1986737007-6">[</span><span class="p" data-group-id="1986737007-6">]</span></code></pre><p>What happens when the filter expression does not evaluate to a boolean value
│ │ │ │ +<code class="inline">&lt;&lt;&gt;&gt;</code> for a bit string comprehension, and <code class="inline">#{}</code> for a map comprehension).</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7831481668-1">[</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="7831481668-2">(</span><span class="mi">2</span><span class="p" data-group-id="7831481668-2">)</span><span class="p" data-group-id="7831481668-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7831481668-3">[</span><span class="mi">2</span><span class="p" data-group-id="7831481668-3">]</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="7831481668-4">[</span><span class="ss">x</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="7831481668-5">(</span><span class="ss">x</span><span class="p" data-group-id="7831481668-5">)</span><span class="p" data-group-id="7831481668-4">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7831481668-6">[</span><span class="p" data-group-id="7831481668-6">]</span></code></pre><p>What happens when the filter expression does not evaluate to a boolean value
│ │ │ │  depends on the expression:</p><ul><li>If the expression is a <a href="expressions.xhtml#guard-expressions">guard expression</a>,
│ │ │ │  failure to evaluate or evaluating to a non-boolean value is equivalent to
│ │ │ │  evaluating to <code class="inline">false</code>.</li><li>If the expression is not a guard expression and evaluates to a non-Boolean
│ │ │ │  value <code class="inline">Val</code>, an exception <code class="inline">{bad_filter, Val}</code> is triggered at runtime. If the
│ │ │ │  evaluation of the expression raises an exception, it is not caught by the
│ │ │ │ -comprehension.</li></ul><p><strong>Examples</strong> (using a guard expression as filter):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7261770075-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="7261770075-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7261770075-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="7261770075-2">]</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="7261770075-3">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="7261770075-3">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7261770075-4">[</span><span class="p" data-group-id="7261770075-4">]</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="7261770075-5">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="7261770075-5">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7261770075-6">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="7261770075-6">]</span></code></pre><p><strong>Examples</strong> (using a non-guard expression as filter):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2208635149-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="2208635149-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2208635149-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="2208635149-2">]</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">FaultyIsEven</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="2208635149-3">(</span><span class="n">E</span><span class="p" data-group-id="2208635149-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +comprehension.</li></ul><p><strong>Examples</strong> (using a guard expression as filter):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1529975345-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="1529975345-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1529975345-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="1529975345-2">]</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="1529975345-3">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1529975345-3">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1529975345-4">[</span><span class="p" data-group-id="1529975345-4">]</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="1529975345-5">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="1529975345-5">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1529975345-6">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="1529975345-6">]</span></code></pre><p><strong>Examples</strong> (using a non-guard expression as filter):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7393795437-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="7393795437-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7393795437-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="7393795437-2">]</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">FaultyIsEven</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="7393795437-3">(</span><span class="n">E</span><span class="p" data-group-id="7393795437-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">42.17316486</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="2208635149-4">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">FaultyIsEven</span><span class="p" data-group-id="2208635149-5">(</span><span class="n">E</span><span class="p" data-group-id="2208635149-5">)</span><span class="p" data-group-id="2208635149-4">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="7393795437-4">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">FaultyIsEven</span><span class="p" data-group-id="7393795437-5">(</span><span class="n">E</span><span class="p" data-group-id="7393795437-5">)</span><span class="p" data-group-id="7393795437-4">]</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: bad filter 1</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="n">IsEven</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="2208635149-6">(</span><span class="n">E</span><span class="p" data-group-id="2208635149-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="n">IsEven</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="7393795437-6">(</span><span class="n">E</span><span class="p" data-group-id="7393795437-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">42.17316486</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="2208635149-7">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">IsEven</span><span class="p" data-group-id="2208635149-8">(</span><span class="n">E</span><span class="p" data-group-id="2208635149-8">)</span><span class="p" data-group-id="2208635149-7">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="7393795437-7">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">IsEven</span><span class="p" data-group-id="7393795437-8">(</span><span class="n">E</span><span class="p" data-group-id="7393795437-8">)</span><span class="p" data-group-id="7393795437-7">]</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: an error occurred when evaluating an arithmetic expression
│ │ │ │       in operator  rem/2
│ │ │ │          called as a rem 2</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="p" data-group-id="2208635149-9">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="2208635149-10">(</span><span class="n">E</span><span class="p" data-group-id="2208635149-10">)</span><span class="p">,</span><span class="w"> </span><span class="n">IsEven</span><span class="p" data-group-id="2208635149-11">(</span><span class="n">E</span><span class="p" data-group-id="2208635149-11">)</span><span class="p" data-group-id="2208635149-9">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2208635149-12">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="2208635149-12">]</span></code></pre><p><a href="" id="guards"></a></p><h2 id="guard-sequences" class="section-heading">
│ │ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="p" data-group-id="7393795437-9">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="7393795437-10">(</span><span class="n">E</span><span class="p" data-group-id="7393795437-10">)</span><span class="p">,</span><span class="w"> </span><span class="n">IsEven</span><span class="p" data-group-id="7393795437-11">(</span><span class="n">E</span><span class="p" data-group-id="7393795437-11">)</span><span class="p" data-group-id="7393795437-9">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7393795437-12">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="7393795437-12">]</span></code></pre><p><a href="" id="guards"></a></p><h2 id="guard-sequences" class="section-heading">
│ │ │ │    <a href="#guard-sequences" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Guard Sequences</span>
│ │ │ │  </h2>
│ │ │ │  <p>A <em>guard sequence</em> is a sequence of guards, separated by semicolon (<code class="inline">;</code>). The
│ │ │ │  guard sequence is true if at least one of the guards is true. (The remaining
│ │ │ ├── OEBPS/example.xhtml
│ │ │ │ @@ -36,14 +36,14 @@
│ │ │ │  
│ │ │ │  int bar(int y) {
│ │ │ │    return y*2;
│ │ │ │  }</code></pre><p>The functions are deliberately kept as simple as possible, for readability
│ │ │ │  reasons.</p><p>From an Erlang perspective, it is preferable to be able to call <code class="inline">foo</code> and <code class="inline">bar</code>
│ │ │ │  without having to bother about that they are C functions:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% Erlang code</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="n">Res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">complex</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="9290611118-1">(</span><span class="n">X</span><span class="p" data-group-id="9290611118-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">complex</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="1878503723-1">(</span><span class="n">X</span><span class="p" data-group-id="1878503723-1">)</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Here, the communication with C is hidden in the implementation of <code class="inline">complex.erl</code>.
│ │ │ │  In the following sections, it is shown how this module can be implemented using
│ │ │ │  the different interoperability mechanisms.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/events.xhtml
│ │ │ │ @@ -40,43 +40,43 @@
│ │ │ │  event handler.</p><h2 id="example" class="section-heading">
│ │ │ │    <a href="#example" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Example</span>
│ │ │ │  </h2>
│ │ │ │  <p>The callback module for the event handler writing error messages to the terminal
│ │ │ │ -can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6894933906-1">(</span><span class="ss">terminal_logger</span><span class="p" data-group-id="6894933906-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="6894933906-2">(</span><span class="ss">gen_event</span><span class="p" data-group-id="6894933906-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1063436283-1">(</span><span class="ss">terminal_logger</span><span class="p" data-group-id="1063436283-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="1063436283-2">(</span><span class="ss">gen_event</span><span class="p" data-group-id="1063436283-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6894933906-3">(</span><span class="p" data-group-id="6894933906-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6894933906-4">]</span><span class="p" data-group-id="6894933906-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1063436283-3">(</span><span class="p" data-group-id="1063436283-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1063436283-4">]</span><span class="p" data-group-id="1063436283-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="6894933906-5">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="6894933906-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6894933906-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6894933906-7">[</span><span class="p" data-group-id="6894933906-7">]</span><span class="p" data-group-id="6894933906-6">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="1063436283-5">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="1063436283-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1063436283-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1063436283-7">[</span><span class="p" data-group-id="1063436283-7">]</span><span class="p" data-group-id="1063436283-6">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="6894933906-8">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="6894933906-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6894933906-9">(</span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6894933906-10">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="6894933906-10">]</span><span class="p" data-group-id="6894933906-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6894933906-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="6894933906-11">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1063436283-8">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="1063436283-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1063436283-9">(</span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1063436283-10">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="1063436283-10">]</span><span class="p" data-group-id="1063436283-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1063436283-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="1063436283-11">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="6894933906-12">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="6894933906-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="1063436283-12">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="1063436283-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The callback module for the event handler writing error messages to a file can
│ │ │ │ -look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5274104397-1">(</span><span class="ss">file_logger</span><span class="p" data-group-id="5274104397-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="5274104397-2">(</span><span class="ss">gen_event</span><span class="p" data-group-id="5274104397-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3720418929-1">(</span><span class="ss">file_logger</span><span class="p" data-group-id="3720418929-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="3720418929-2">(</span><span class="ss">gen_event</span><span class="p" data-group-id="3720418929-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5274104397-3">(</span><span class="p" data-group-id="5274104397-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5274104397-4">]</span><span class="p" data-group-id="5274104397-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3720418929-3">(</span><span class="p" data-group-id="3720418929-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3720418929-4">]</span><span class="p" data-group-id="3720418929-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="5274104397-5">(</span><span class="n">File</span><span class="p" data-group-id="5274104397-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5274104397-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="5274104397-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="5274104397-7">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">read</span><span class="p" data-group-id="5274104397-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5274104397-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="5274104397-8">}</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="5274104397-9">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="5274104397-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5274104397-10">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5274104397-11">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="5274104397-11">]</span><span class="p" data-group-id="5274104397-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5274104397-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="5274104397-12">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="3720418929-5">(</span><span class="n">File</span><span class="p" data-group-id="3720418929-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3720418929-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="3720418929-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="3720418929-7">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">read</span><span class="p" data-group-id="3720418929-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3720418929-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="3720418929-8">}</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="3720418929-9">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="3720418929-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3720418929-10">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3720418929-11">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="3720418929-11">]</span><span class="p" data-group-id="3720418929-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3720418929-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="3720418929-12">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="5274104397-13">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="5274104397-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="5274104397-14">(</span><span class="n">Fd</span><span class="p" data-group-id="5274104397-14">)</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><p><a href="" id="mgr"></a></p><h2 id="starting-an-event-manager" class="section-heading">
│ │ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="3720418929-13">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="3720418929-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="3720418929-14">(</span><span class="n">Fd</span><span class="p" data-group-id="3720418929-14">)</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><p><a href="" id="mgr"></a></p><h2 id="starting-an-event-manager" class="section-heading">
│ │ │ │    <a href="#starting-an-event-manager" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Starting an Event Manager</span>
│ │ │ │  </h2>
│ │ │ │  <p>To start an event manager for handling errors, as described in the previous
│ │ │ │  example, call the following function:</p><pre><code class="text">gen_event:start_link({local, error_man})</code></pre><p><a href="../../../lib/stdlib/doc/html/gen_event.html#start_link/1"><code class="inline">gen_event:start_link/1</code></a> spawns and links to a new event manager process.</p><p>The argument, <code class="inline">{local, error_man}</code>, specifies the name under which the
│ │ │ │ @@ -89,57 +89,57 @@
│ │ │ │  manager that is not part of a supervision tree.</p><h2 id="adding-an-event-handler" class="section-heading">
│ │ │ │    <a href="#adding-an-event-handler" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Adding an Event Handler</span>
│ │ │ │  </h2>
│ │ │ │  <p>The following example shows how to start an event manager and add an event
│ │ │ │ -handler to it by using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="3934450264-1">(</span><span class="p" data-group-id="3934450264-2">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">error_man</span><span class="p" data-group-id="3934450264-2">}</span><span class="p" data-group-id="3934450264-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3934450264-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.31</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="3934450264-3">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">add_handler</span><span class="p" data-group-id="3934450264-4">(</span><span class="ss">error_man</span><span class="p">,</span><span class="w"> </span><span class="ss">terminal_logger</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3934450264-5">[</span><span class="p" data-group-id="3934450264-5">]</span><span class="p" data-group-id="3934450264-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +handler to it by using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="9858497625-1">(</span><span class="p" data-group-id="9858497625-2">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">error_man</span><span class="p" data-group-id="9858497625-2">}</span><span class="p" data-group-id="9858497625-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9858497625-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.31</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="9858497625-3">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">add_handler</span><span class="p" data-group-id="9858497625-4">(</span><span class="ss">error_man</span><span class="p">,</span><span class="w"> </span><span class="ss">terminal_logger</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9858497625-5">[</span><span class="p" data-group-id="9858497625-5">]</span><span class="p" data-group-id="9858497625-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>This function sends a message to the event manager registered as <code class="inline">error_man</code>,
│ │ │ │  telling it to add the event handler <code class="inline">terminal_logger</code>. The event manager calls
│ │ │ │  the callback function <code class="inline">terminal_logger:init([])</code>, where the argument <code class="inline">[]</code> is the
│ │ │ │  third argument to <code class="inline">add_handler</code>. <code class="inline">init/1</code> is expected to return <code class="inline">{ok, State}</code>,
│ │ │ │ -where <code class="inline">State</code> is the internal state of the event handler.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="4897504834-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="4897504834-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4897504834-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4897504834-3">[</span><span class="p" data-group-id="4897504834-3">]</span><span class="p" data-group-id="4897504834-2">}</span><span class="p">.</span></code></pre><p>Here, <code class="inline">init/1</code> does not need any input data and ignores its argument. For
│ │ │ │ +where <code class="inline">State</code> is the internal state of the event handler.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="3771953486-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="3771953486-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3771953486-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3771953486-3">[</span><span class="p" data-group-id="3771953486-3">]</span><span class="p" data-group-id="3771953486-2">}</span><span class="p">.</span></code></pre><p>Here, <code class="inline">init/1</code> does not need any input data and ignores its argument. For
│ │ │ │  <code class="inline">terminal_logger</code>, the internal state is not used. For <code class="inline">file_logger</code>, the
│ │ │ │ -internal state is used to save the open file descriptor.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="9859940420-1">(</span><span class="n">File</span><span class="p" data-group-id="9859940420-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9859940420-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="9859940420-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="9859940420-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">read</span><span class="p" data-group-id="9859940420-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9859940420-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="9859940420-4">}</span><span class="p">.</span></code></pre><h2 id="notifying-about-events" class="section-heading">
│ │ │ │ +internal state is used to save the open file descriptor.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="3664686875-1">(</span><span class="n">File</span><span class="p" data-group-id="3664686875-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3664686875-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="3664686875-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="3664686875-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">read</span><span class="p" data-group-id="3664686875-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3664686875-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="3664686875-4">}</span><span class="p">.</span></code></pre><h2 id="notifying-about-events" class="section-heading">
│ │ │ │    <a href="#notifying-about-events" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Notifying about Events</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="text">3&gt; gen_event:notify(error_man, no_reply).
│ │ │ │  ***Error*** no_reply
│ │ │ │  ok</code></pre><p><code class="inline">error_man</code> is the name of the event manager and <code class="inline">no_reply</code> is the event.</p><p>The event is made into a message and sent to the event manager. When the event
│ │ │ │  is received, the event manager calls <code class="inline">handle_event(Event, State)</code> for each
│ │ │ │  installed event handler, in the same order as they were added. The function is
│ │ │ │  expected to return a tuple <code class="inline">{ok,State1}</code>, where <code class="inline">State1</code> is a new value for the
│ │ │ │ -state of the event handler.</p><p>In <code class="inline">terminal_logger</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_event</span><span class="p" data-group-id="3150812796-1">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="3150812796-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3150812796-2">(</span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3150812796-3">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="3150812796-3">]</span><span class="p" data-group-id="3150812796-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3150812796-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="3150812796-4">}</span><span class="p">.</span></code></pre><p>In <code class="inline">file_logger</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_event</span><span class="p" data-group-id="6077363149-1">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="6077363149-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6077363149-2">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6077363149-3">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="6077363149-3">]</span><span class="p" data-group-id="6077363149-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6077363149-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="6077363149-4">}</span><span class="p">.</span></code></pre><h2 id="deleting-an-event-handler" class="section-heading">
│ │ │ │ +state of the event handler.</p><p>In <code class="inline">terminal_logger</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_event</span><span class="p" data-group-id="0403189584-1">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0403189584-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0403189584-2">(</span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0403189584-3">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="0403189584-3">]</span><span class="p" data-group-id="0403189584-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0403189584-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0403189584-4">}</span><span class="p">.</span></code></pre><p>In <code class="inline">file_logger</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_event</span><span class="p" data-group-id="6935111549-1">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="6935111549-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6935111549-2">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6935111549-3">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="6935111549-3">]</span><span class="p" data-group-id="6935111549-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6935111549-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="6935111549-4">}</span><span class="p">.</span></code></pre><h2 id="deleting-an-event-handler" class="section-heading">
│ │ │ │    <a href="#deleting-an-event-handler" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Deleting an Event Handler</span>
│ │ │ │  </h2>
│ │ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">delete_handler</span><span class="p" data-group-id="5282159329-1">(</span><span class="ss">error_man</span><span class="p">,</span><span class="w"> </span><span class="ss">terminal_logger</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5282159329-2">[</span><span class="p" data-group-id="5282159329-2">]</span><span class="p" data-group-id="5282159329-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">delete_handler</span><span class="p" data-group-id="1253186083-1">(</span><span class="ss">error_man</span><span class="p">,</span><span class="w"> </span><span class="ss">terminal_logger</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1253186083-2">[</span><span class="p" data-group-id="1253186083-2">]</span><span class="p" data-group-id="1253186083-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>This function sends a message to the event manager registered as <code class="inline">error_man</code>,
│ │ │ │  telling it to delete the event handler <code class="inline">terminal_logger</code>. The event manager
│ │ │ │  calls the callback function <code class="inline">terminal_logger:terminate([], State)</code>, where the
│ │ │ │  argument <code class="inline">[]</code> is the third argument to <code class="inline">delete_handler</code>. <code class="inline">terminate/2</code> is to be
│ │ │ │  the opposite of <code class="inline">init/1</code> and do any necessary cleaning up. Its return value is
│ │ │ │ -ignored.</p><p>For <code class="inline">terminal_logger</code>, no cleaning up is necessary:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="3886713952-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="3886713952-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>For <code class="inline">file_logger</code>, the file descriptor opened in <code class="inline">init</code> must be closed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="3446377108-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="3446377108-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="3446377108-2">(</span><span class="n">Fd</span><span class="p" data-group-id="3446377108-2">)</span><span class="p">.</span></code></pre><h2 id="stopping" class="section-heading">
│ │ │ │ +ignored.</p><p>For <code class="inline">terminal_logger</code>, no cleaning up is necessary:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="8559342947-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="8559342947-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>For <code class="inline">file_logger</code>, the file descriptor opened in <code class="inline">init</code> must be closed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="1895248149-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="1895248149-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="1895248149-2">(</span><span class="n">Fd</span><span class="p" data-group-id="1895248149-2">)</span><span class="p">.</span></code></pre><h2 id="stopping" class="section-heading">
│ │ │ │    <a href="#stopping" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Stopping</span>
│ │ │ │  </h2>
│ │ │ │  <p>When an event manager is stopped, it gives each of the installed event handlers
│ │ │ │  the chance to clean up by calling <code class="inline">terminate/2</code>, the same way as when deleting a
│ │ │ │ @@ -154,29 +154,29 @@
│ │ │ │  this is done is defined by a <a href="sup_princ.xhtml#shutdown">shutdown strategy</a> set in
│ │ │ │  the supervisor.</p><h3 id="standalone-event-managers" class="section-heading">
│ │ │ │    <a href="#standalone-event-managers" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Standalone Event Managers</span>
│ │ │ │  </h3>
│ │ │ │ -<p>An event manager can also be stopped by calling:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="2071507889-1">(</span><span class="ss">error_man</span><span class="p" data-group-id="2071507889-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>An event manager can also be stopped by calling:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="6538719200-1">(</span><span class="ss">error_man</span><span class="p" data-group-id="6538719200-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><h2 id="handling-other-messages" class="section-heading">
│ │ │ │    <a href="#handling-other-messages" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Handling Other Messages</span>
│ │ │ │  </h2>
│ │ │ │  <p>If the <code class="inline">gen_event</code> process is to be able to receive other messages
│ │ │ │  than events, the callback function <code class="inline">handle_info(Info, State)</code> must be
│ │ │ │  implemented to handle them. Examples of other messages are exit
│ │ │ │  messages if the event manager is linked to other processes than the
│ │ │ │  supervisor (for example via <a href="../../../lib/stdlib/doc/html/gen_event.html#add_sup_handler/3"><code class="inline">gen_event:add_sup_handler/3</code></a>) and is
│ │ │ │ -trapping exit signals.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_info</span><span class="p" data-group-id="7399537144-1">(</span><span class="p" data-group-id="7399537144-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="7399537144-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="7399537144-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +trapping exit signals.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_info</span><span class="p" data-group-id="9075634613-1">(</span><span class="p" data-group-id="9075634613-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="9075634613-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="9075634613-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Code to handle exits here.</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7399537144-3">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="7399537144-3">}</span><span class="p">.</span></code></pre><p>The final function to implement is <code class="inline">code_change/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="4855594638-1">(</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="4855594638-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9075634613-3">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="9075634613-3">}</span><span class="p">.</span></code></pre><p>The final function to implement is <code class="inline">code_change/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="8446253002-1">(</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="8446253002-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Code to convert state (and more) during code change.</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4855594638-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NewState</span><span class="p" data-group-id="4855594638-2">}</span><span class="p">.</span></code></pre>
│ │ │ │ +    </span><span class="p" data-group-id="8446253002-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NewState</span><span class="p" data-group-id="8446253002-2">}</span><span class="p">.</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/errors.xhtml
│ │ │ │ @@ -56,22 +56,22 @@
│ │ │ │  classes, with different origins. The <a href="expressions.xhtml#try">try</a> expression can
│ │ │ │  distinguish between the different classes, whereas the
│ │ │ │  <a href="expressions.xhtml#catch-and-throw">catch</a> expression cannot. <code class="inline">try</code> and <code class="inline">catch</code> are described
│ │ │ │  in <a href="expressions.xhtml">Expressions</a>.</p><table><thead><tr><th style="text-align: left;">Class</th><th style="text-align: left;">Origin</th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">error</code></td><td style="text-align: left;">Run-time error, for example, <code class="inline">1+a</code>, or the process called <a href="../../../lib/../erts/doc/html/erlang.html#error/1"><code class="inline">error/1</code></a></td></tr><tr><td style="text-align: left;"><code class="inline">exit</code></td><td style="text-align: left;">The process called <a href="../../../lib/../erts/doc/html/erlang.html#exit/1"><code class="inline">exit/1</code></a></td></tr><tr><td style="text-align: left;"><code class="inline">throw</code></td><td style="text-align: left;">The process called <a href="../../../lib/../erts/doc/html/erlang.html#throw/1"><code class="inline">throw/1</code></a></td></tr></tbody></table><p><em>Table: Exception Classes.</em></p><p>All of the above exceptions can also be generated by calling <a href="../../../lib/../erts/doc/html/erlang.html#raise/3"><code class="inline">erlang:raise/3</code></a>.</p><p>An exception consists of its class, an exit reason (see
│ │ │ │  <a href="errors.xhtml#exit_reasons">Exit Reason</a>), and a stack trace (which aids in finding
│ │ │ │  the code location of the exception).</p><p>The stack trace can be bound to a variable from within a <code class="inline">try</code> expression for
│ │ │ │  any exception class, or as part of the exit reason when a run-time error is
│ │ │ │ -caught by a <code class="inline">catch</code>. Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="3940435099-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="3940435099-2">{</span><span class="ss">test</span><span class="p">,</span><span class="n">Stacktrace</span><span class="p" data-group-id="3940435099-2">}</span><span class="p" data-group-id="3940435099-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3940435099-3">(</span><span class="k">catch</span><span class="w"> </span><span class="nf">error</span><span class="p" data-group-id="3940435099-4">(</span><span class="ss">test</span><span class="p" data-group-id="3940435099-4">)</span><span class="p" data-group-id="3940435099-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Stacktrace</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3940435099-5">[</span><span class="p" data-group-id="3940435099-6">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="3940435099-7">[</span><span class="p" data-group-id="3940435099-7">]</span><span class="p" data-group-id="3940435099-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3940435099-8">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="3940435099-9">[</span><span class="p" data-group-id="3940435099-9">]</span><span class="p" data-group-id="3940435099-8">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3940435099-5">]</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">&gt; </span><span class="k">try</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="3940435099-10">(</span><span class="ss">test</span><span class="p" data-group-id="3940435099-10">)</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="n">Class</span><span class="p">:</span><span class="n">Reason</span><span class="p">:</span><span class="n">Stacktrace</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Stacktrace</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3940435099-11">[</span><span class="p" data-group-id="3940435099-12">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="3940435099-13">[</span><span class="p" data-group-id="3940435099-13">]</span><span class="p" data-group-id="3940435099-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3940435099-14">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="3940435099-15">[</span><span class="p" data-group-id="3940435099-15">]</span><span class="p" data-group-id="3940435099-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3940435099-11">]</span></code></pre><p><a href="" id="stacktrace"></a></p><h3 id="the-call-stack-backtrace-stacktrace" class="section-heading">
│ │ │ │ +caught by a <code class="inline">catch</code>. Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="4961400300-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="4961400300-2">{</span><span class="ss">test</span><span class="p">,</span><span class="n">Stacktrace</span><span class="p" data-group-id="4961400300-2">}</span><span class="p" data-group-id="4961400300-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4961400300-3">(</span><span class="k">catch</span><span class="w"> </span><span class="nf">error</span><span class="p" data-group-id="4961400300-4">(</span><span class="ss">test</span><span class="p" data-group-id="4961400300-4">)</span><span class="p" data-group-id="4961400300-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Stacktrace</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4961400300-5">[</span><span class="p" data-group-id="4961400300-6">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="4961400300-7">[</span><span class="p" data-group-id="4961400300-7">]</span><span class="p" data-group-id="4961400300-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="4961400300-8">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="4961400300-9">[</span><span class="p" data-group-id="4961400300-9">]</span><span class="p" data-group-id="4961400300-8">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4961400300-5">]</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">&gt; </span><span class="k">try</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="4961400300-10">(</span><span class="ss">test</span><span class="p" data-group-id="4961400300-10">)</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="n">Class</span><span class="p">:</span><span class="n">Reason</span><span class="p">:</span><span class="n">Stacktrace</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Stacktrace</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4961400300-11">[</span><span class="p" data-group-id="4961400300-12">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="4961400300-13">[</span><span class="p" data-group-id="4961400300-13">]</span><span class="p" data-group-id="4961400300-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="4961400300-14">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="4961400300-15">[</span><span class="p" data-group-id="4961400300-15">]</span><span class="p" data-group-id="4961400300-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4961400300-11">]</span></code></pre><p><a href="" id="stacktrace"></a></p><h3 id="the-call-stack-backtrace-stacktrace" class="section-heading">
│ │ │ │    <a href="#the-call-stack-backtrace-stacktrace" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">The call-stack backtrace (stacktrace)</span>
│ │ │ │  </h3>
│ │ │ │  <p>The stack backtrace (<a href="../../../lib/../erts/doc/html/erlang.html#t:stacktrace/0"><em>stacktrace</em></a>) is a list that
│ │ │ │  contains <code class="inline">{Module, Function, Arity, ExtraInfo}</code> and/or <code class="inline">{Fun, Arity, ExtraInfo}</code>
│ │ │ ├── OEBPS/erl_interface.xhtml
│ │ │ │ @@ -25,119 +25,119 @@
│ │ │ │  to read the port example in <a href="c_port.xhtml">Ports</a> before reading this section.</p><h2 id="erlang-program" class="section-heading">
│ │ │ │    <a href="#erlang-program" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Erlang Program</span>
│ │ │ │  </h2>
│ │ │ │  <p>The following example shows an Erlang program communicating with a C program
│ │ │ │ -over a plain port with home made encoding:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0094190037-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="0094190037-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0094190037-2">(</span><span class="p" data-group-id="0094190037-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0094190037-3">]</span><span class="p" data-group-id="0094190037-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0094190037-4">(</span><span class="p" data-group-id="0094190037-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0094190037-5">]</span><span class="p" data-group-id="0094190037-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="0094190037-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="0094190037-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="0094190037-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0094190037-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="0094190037-8">]</span><span class="p" data-group-id="0094190037-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="0094190037-9">(</span><span class="p" data-group-id="0094190037-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +over a plain port with home made encoding:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0347870446-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="0347870446-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0347870446-2">(</span><span class="p" data-group-id="0347870446-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0347870446-3">]</span><span class="p" data-group-id="0347870446-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0347870446-4">(</span><span class="p" data-group-id="0347870446-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0347870446-5">]</span><span class="p" data-group-id="0347870446-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="0347870446-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="0347870446-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="0347870446-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0347870446-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="0347870446-8">]</span><span class="p" data-group-id="0347870446-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="0347870446-9">(</span><span class="p" data-group-id="0347870446-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">stop</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="0094190037-10">(</span><span class="n">X</span><span class="p" data-group-id="0094190037-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="0094190037-11">(</span><span class="p" data-group-id="0094190037-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0094190037-12">}</span><span class="p" data-group-id="0094190037-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="0094190037-13">(</span><span class="n">Y</span><span class="p" data-group-id="0094190037-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="0094190037-14">(</span><span class="p" data-group-id="0094190037-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0094190037-15">}</span><span class="p" data-group-id="0094190037-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="0347870446-10">(</span><span class="n">X</span><span class="p" data-group-id="0347870446-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="0347870446-11">(</span><span class="p" data-group-id="0347870446-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0347870446-12">}</span><span class="p" data-group-id="0347870446-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="0347870446-13">(</span><span class="n">Y</span><span class="p" data-group-id="0347870446-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="0347870446-14">(</span><span class="p" data-group-id="0347870446-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0347870446-15">}</span><span class="p" data-group-id="0347870446-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="0094190037-16">(</span><span class="n">Msg</span><span class="p" data-group-id="0094190037-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0094190037-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0094190037-18">(</span><span class="p" data-group-id="0094190037-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0094190037-17">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="0347870446-16">(</span><span class="n">Msg</span><span class="p" data-group-id="0347870446-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0347870446-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0347870446-18">(</span><span class="p" data-group-id="0347870446-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0347870446-17">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="0094190037-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0094190037-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="0347870446-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0347870446-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  	    </span><span class="n">Result</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="0094190037-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="0094190037-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="0094190037-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0094190037-22">(</span><span class="p" data-group-id="0094190037-22">)</span><span class="p" data-group-id="0094190037-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="0094190037-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0094190037-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="0094190037-24">(</span><span class="p" data-group-id="0094190037-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="0094190037-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0094190037-26">[</span><span class="p" data-group-id="0094190037-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0094190037-27">}</span><span class="p" data-group-id="0094190037-26">]</span><span class="p" data-group-id="0094190037-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="0094190037-28">(</span><span class="n">Port</span><span class="p" data-group-id="0094190037-28">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="0347870446-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="0347870446-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="0347870446-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0347870446-22">(</span><span class="p" data-group-id="0347870446-22">)</span><span class="p" data-group-id="0347870446-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="0347870446-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0347870446-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="0347870446-24">(</span><span class="p" data-group-id="0347870446-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="0347870446-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0347870446-26">[</span><span class="p" data-group-id="0347870446-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0347870446-27">}</span><span class="p" data-group-id="0347870446-26">]</span><span class="p" data-group-id="0347870446-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="0347870446-28">(</span><span class="n">Port</span><span class="p" data-group-id="0347870446-28">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="0094190037-29">(</span><span class="n">Port</span><span class="p" data-group-id="0094190037-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="0347870446-29">(</span><span class="n">Port</span><span class="p" data-group-id="0347870446-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="0094190037-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0094190037-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0094190037-31">{</span><span class="nf">self</span><span class="p" data-group-id="0094190037-32">(</span><span class="p" data-group-id="0094190037-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0094190037-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="0094190037-34">(</span><span class="n">Msg</span><span class="p" data-group-id="0094190037-34">)</span><span class="p" data-group-id="0094190037-33">}</span><span class="p" data-group-id="0094190037-31">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="0347870446-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0347870446-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0347870446-31">{</span><span class="nf">self</span><span class="p" data-group-id="0347870446-32">(</span><span class="p" data-group-id="0347870446-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0347870446-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="0347870446-34">(</span><span class="n">Msg</span><span class="p" data-group-id="0347870446-34">)</span><span class="p" data-group-id="0347870446-33">}</span><span class="p" data-group-id="0347870446-31">}</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="0094190037-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0094190037-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0094190037-36">}</span><span class="p" data-group-id="0094190037-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0094190037-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="0094190037-38">(</span><span class="n">Data</span><span class="p" data-group-id="0094190037-38">)</span><span class="p" data-group-id="0094190037-37">}</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="0347870446-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0347870446-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0347870446-36">}</span><span class="p" data-group-id="0347870446-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0347870446-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="0347870446-38">(</span><span class="n">Data</span><span class="p" data-group-id="0347870446-38">)</span><span class="p" data-group-id="0347870446-37">}</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -	    </span><span class="nf">loop</span><span class="p" data-group-id="0094190037-39">(</span><span class="n">Port</span><span class="p" data-group-id="0094190037-39">)</span><span class="p">;</span><span class="w">
│ │ │ │ +	    </span><span class="nf">loop</span><span class="p" data-group-id="0347870446-39">(</span><span class="n">Port</span><span class="p" data-group-id="0347870446-39">)</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">stop</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0094190037-40">{</span><span class="nf">self</span><span class="p" data-group-id="0094190037-41">(</span><span class="p" data-group-id="0094190037-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="0094190037-40">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0347870446-40">{</span><span class="nf">self</span><span class="p" data-group-id="0347870446-41">(</span><span class="p" data-group-id="0347870446-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="0347870446-40">}</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="0094190037-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="0094190037-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="nf">exit</span><span class="p" data-group-id="0094190037-43">(</span><span class="ss">normal</span><span class="p" data-group-id="0094190037-43">)</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="0347870446-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="0347870446-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="nf">exit</span><span class="p" data-group-id="0347870446-43">(</span><span class="ss">normal</span><span class="p" data-group-id="0347870446-43">)</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="0094190037-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="0094190037-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="nf">exit</span><span class="p" data-group-id="0094190037-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="0094190037-45">)</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="0347870446-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="0347870446-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	    </span><span class="nf">exit</span><span class="p" data-group-id="0347870446-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="0347870446-45">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="0094190037-46">(</span><span class="p" data-group-id="0094190037-47">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0094190037-47">}</span><span class="p" data-group-id="0094190037-46">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0094190037-48">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0094190037-48">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="0094190037-49">(</span><span class="p" data-group-id="0094190037-50">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0094190037-50">}</span><span class="p" data-group-id="0094190037-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0094190037-51">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0094190037-51">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="0347870446-46">(</span><span class="p" data-group-id="0347870446-47">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0347870446-47">}</span><span class="p" data-group-id="0347870446-46">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0347870446-48">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0347870446-48">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="0347870446-49">(</span><span class="p" data-group-id="0347870446-50">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0347870446-50">}</span><span class="p" data-group-id="0347870446-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0347870446-51">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0347870446-51">]</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="0094190037-52">(</span><span class="p" data-group-id="0094190037-53">[</span><span class="n">Int</span><span class="p" data-group-id="0094190037-53">]</span><span class="p" data-group-id="0094190037-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>There are two differences when using Erl_Interface on the C side compared to the
│ │ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="0347870446-52">(</span><span class="p" data-group-id="0347870446-53">[</span><span class="n">Int</span><span class="p" data-group-id="0347870446-53">]</span><span class="p" data-group-id="0347870446-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>There are two differences when using Erl_Interface on the C side compared to the
│ │ │ │  example in <a href="c_port.xhtml">Ports</a>, using only the plain port:</p><ul><li>As Erl_Interface operates on the Erlang external term format, the port must be
│ │ │ │  set to use binaries.</li><li>Instead of inventing an encoding/decoding scheme, the
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#term_to_binary/1"><code class="inline">term_to_binary/1</code></a> and
│ │ │ │ -<a href="../../../lib/../erts/doc/html/erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a> BIFs are to be used.</li></ul><p>That is:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open_port</span><span class="p" data-group-id="4304825952-1">(</span><span class="p" data-group-id="4304825952-2">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="4304825952-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4304825952-3">[</span><span class="p" data-group-id="4304825952-4">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="4304825952-4">}</span><span class="p" data-group-id="4304825952-3">]</span><span class="p" data-group-id="4304825952-1">)</span></code></pre><p>is replaced with:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open_port</span><span class="p" data-group-id="0969574476-1">(</span><span class="p" data-group-id="0969574476-2">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="0969574476-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0969574476-3">[</span><span class="p" data-group-id="0969574476-4">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0969574476-4">}</span><span class="p">,</span><span class="w"> </span><span class="ss">binary</span><span class="p" data-group-id="0969574476-3">]</span><span class="p" data-group-id="0969574476-1">)</span></code></pre><p>And:</p><pre><code class="makeup erlang" translate="no"><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4442490758-1">{</span><span class="nf">self</span><span class="p" data-group-id="4442490758-2">(</span><span class="p" data-group-id="4442490758-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4442490758-3">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="4442490758-4">(</span><span class="n">Msg</span><span class="p" data-group-id="4442490758-4">)</span><span class="p" data-group-id="4442490758-3">}</span><span class="p" data-group-id="4442490758-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ +<a href="../../../lib/../erts/doc/html/erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a> BIFs are to be used.</li></ul><p>That is:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open_port</span><span class="p" data-group-id="3062156321-1">(</span><span class="p" data-group-id="3062156321-2">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="3062156321-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3062156321-3">[</span><span class="p" data-group-id="3062156321-4">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="3062156321-4">}</span><span class="p" data-group-id="3062156321-3">]</span><span class="p" data-group-id="3062156321-1">)</span></code></pre><p>is replaced with:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open_port</span><span class="p" data-group-id="6848065509-1">(</span><span class="p" data-group-id="6848065509-2">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="6848065509-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6848065509-3">[</span><span class="p" data-group-id="6848065509-4">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="6848065509-4">}</span><span class="p">,</span><span class="w"> </span><span class="ss">binary</span><span class="p" data-group-id="6848065509-3">]</span><span class="p" data-group-id="6848065509-1">)</span></code></pre><p>And:</p><pre><code class="makeup erlang" translate="no"><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9516945423-1">{</span><span class="nf">self</span><span class="p" data-group-id="9516945423-2">(</span><span class="p" data-group-id="9516945423-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9516945423-3">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="9516945423-4">(</span><span class="n">Msg</span><span class="p" data-group-id="9516945423-4">)</span><span class="p" data-group-id="9516945423-3">}</span><span class="p" data-group-id="9516945423-1">}</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="4442490758-5">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4442490758-6">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4442490758-6">}</span><span class="p" data-group-id="4442490758-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4442490758-7">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="4442490758-8">(</span><span class="n">Data</span><span class="p" data-group-id="4442490758-8">)</span><span class="p" data-group-id="4442490758-7">}</span><span class="w">
│ │ │ │ -</span><span class="k">end</span></code></pre><p>is replaced with:</p><pre><code class="makeup erlang" translate="no"><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1655019237-1">{</span><span class="nf">self</span><span class="p" data-group-id="1655019237-2">(</span><span class="p" data-group-id="1655019237-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1655019237-3">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="1655019237-4">(</span><span class="n">Msg</span><span class="p" data-group-id="1655019237-4">)</span><span class="p" data-group-id="1655019237-3">}</span><span class="p" data-group-id="1655019237-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="9516945423-5">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9516945423-6">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9516945423-6">}</span><span class="p" data-group-id="9516945423-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9516945423-7">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="9516945423-8">(</span><span class="n">Data</span><span class="p" data-group-id="9516945423-8">)</span><span class="p" data-group-id="9516945423-7">}</span><span class="w">
│ │ │ │ +</span><span class="k">end</span></code></pre><p>is replaced with:</p><pre><code class="makeup erlang" translate="no"><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9934031089-1">{</span><span class="nf">self</span><span class="p" data-group-id="9934031089-2">(</span><span class="p" data-group-id="9934031089-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9934031089-3">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="9934031089-4">(</span><span class="n">Msg</span><span class="p" data-group-id="9934031089-4">)</span><span class="p" data-group-id="9934031089-3">}</span><span class="p" data-group-id="9934031089-1">}</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="1655019237-5">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1655019237-6">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1655019237-6">}</span><span class="p" data-group-id="1655019237-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1655019237-7">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="1655019237-8">(</span><span class="n">Data</span><span class="p" data-group-id="1655019237-8">)</span><span class="p" data-group-id="1655019237-7">}</span><span class="w">
│ │ │ │ -</span><span class="k">end</span></code></pre><p>The resulting Erlang program is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6740567720-1">(</span><span class="ss">complex2</span><span class="p" data-group-id="6740567720-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6740567720-2">(</span><span class="p" data-group-id="6740567720-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6740567720-3">]</span><span class="p" data-group-id="6740567720-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6740567720-4">(</span><span class="p" data-group-id="6740567720-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6740567720-5">]</span><span class="p" data-group-id="6740567720-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="6740567720-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="6740567720-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="6740567720-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6740567720-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="6740567720-8">]</span><span class="p" data-group-id="6740567720-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="6740567720-9">(</span><span class="p" data-group-id="6740567720-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="9934031089-5">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9934031089-6">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9934031089-6">}</span><span class="p" data-group-id="9934031089-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9934031089-7">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="9934031089-8">(</span><span class="n">Data</span><span class="p" data-group-id="9934031089-8">)</span><span class="p" data-group-id="9934031089-7">}</span><span class="w">
│ │ │ │ +</span><span class="k">end</span></code></pre><p>The resulting Erlang program is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9725587070-1">(</span><span class="ss">complex2</span><span class="p" data-group-id="9725587070-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9725587070-2">(</span><span class="p" data-group-id="9725587070-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9725587070-3">]</span><span class="p" data-group-id="9725587070-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9725587070-4">(</span><span class="p" data-group-id="9725587070-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9725587070-5">]</span><span class="p" data-group-id="9725587070-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="9725587070-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="9725587070-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="9725587070-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9725587070-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="9725587070-8">]</span><span class="p" data-group-id="9725587070-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="9725587070-9">(</span><span class="p" data-group-id="9725587070-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">stop</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="6740567720-10">(</span><span class="n">X</span><span class="p" data-group-id="6740567720-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="6740567720-11">(</span><span class="p" data-group-id="6740567720-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="6740567720-12">}</span><span class="p" data-group-id="6740567720-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="6740567720-13">(</span><span class="n">Y</span><span class="p" data-group-id="6740567720-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="6740567720-14">(</span><span class="p" data-group-id="6740567720-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6740567720-15">}</span><span class="p" data-group-id="6740567720-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="9725587070-10">(</span><span class="n">X</span><span class="p" data-group-id="9725587070-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="9725587070-11">(</span><span class="p" data-group-id="9725587070-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9725587070-12">}</span><span class="p" data-group-id="9725587070-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="9725587070-13">(</span><span class="n">Y</span><span class="p" data-group-id="9725587070-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="9725587070-14">(</span><span class="p" data-group-id="9725587070-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9725587070-15">}</span><span class="p" data-group-id="9725587070-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="6740567720-16">(</span><span class="n">Msg</span><span class="p" data-group-id="6740567720-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6740567720-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6740567720-18">(</span><span class="p" data-group-id="6740567720-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="6740567720-17">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="9725587070-16">(</span><span class="n">Msg</span><span class="p" data-group-id="9725587070-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9725587070-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9725587070-18">(</span><span class="p" data-group-id="9725587070-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="9725587070-17">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="6740567720-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="6740567720-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="9725587070-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="9725587070-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  	    </span><span class="n">Result</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="6740567720-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="6740567720-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="6740567720-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6740567720-22">(</span><span class="p" data-group-id="6740567720-22">)</span><span class="p" data-group-id="6740567720-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="6740567720-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="6740567720-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="6740567720-24">(</span><span class="p" data-group-id="6740567720-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="6740567720-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6740567720-26">[</span><span class="p" data-group-id="6740567720-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="6740567720-27">}</span><span class="p">,</span><span class="w"> </span><span class="ss">binary</span><span class="p" data-group-id="6740567720-26">]</span><span class="p" data-group-id="6740567720-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="6740567720-28">(</span><span class="n">Port</span><span class="p" data-group-id="6740567720-28">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="9725587070-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="9725587070-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="9725587070-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9725587070-22">(</span><span class="p" data-group-id="9725587070-22">)</span><span class="p" data-group-id="9725587070-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="9725587070-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="9725587070-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="9725587070-24">(</span><span class="p" data-group-id="9725587070-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="9725587070-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9725587070-26">[</span><span class="p" data-group-id="9725587070-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="9725587070-27">}</span><span class="p">,</span><span class="w"> </span><span class="ss">binary</span><span class="p" data-group-id="9725587070-26">]</span><span class="p" data-group-id="9725587070-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="9725587070-28">(</span><span class="n">Port</span><span class="p" data-group-id="9725587070-28">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="6740567720-29">(</span><span class="n">Port</span><span class="p" data-group-id="6740567720-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="9725587070-29">(</span><span class="n">Port</span><span class="p" data-group-id="9725587070-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="6740567720-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="6740567720-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6740567720-31">{</span><span class="nf">self</span><span class="p" data-group-id="6740567720-32">(</span><span class="p" data-group-id="6740567720-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6740567720-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="6740567720-34">(</span><span class="n">Msg</span><span class="p" data-group-id="6740567720-34">)</span><span class="p" data-group-id="6740567720-33">}</span><span class="p" data-group-id="6740567720-31">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="9725587070-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="9725587070-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9725587070-31">{</span><span class="nf">self</span><span class="p" data-group-id="9725587070-32">(</span><span class="p" data-group-id="9725587070-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9725587070-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="9725587070-34">(</span><span class="n">Msg</span><span class="p" data-group-id="9725587070-34">)</span><span class="p" data-group-id="9725587070-33">}</span><span class="p" data-group-id="9725587070-31">}</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="6740567720-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6740567720-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6740567720-36">}</span><span class="p" data-group-id="6740567720-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6740567720-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="6740567720-38">(</span><span class="n">Data</span><span class="p" data-group-id="6740567720-38">)</span><span class="p" data-group-id="6740567720-37">}</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="9725587070-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9725587070-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9725587070-36">}</span><span class="p" data-group-id="9725587070-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9725587070-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="9725587070-38">(</span><span class="n">Data</span><span class="p" data-group-id="9725587070-38">)</span><span class="p" data-group-id="9725587070-37">}</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -	    </span><span class="nf">loop</span><span class="p" data-group-id="6740567720-39">(</span><span class="n">Port</span><span class="p" data-group-id="6740567720-39">)</span><span class="p">;</span><span class="w">
│ │ │ │ +	    </span><span class="nf">loop</span><span class="p" data-group-id="9725587070-39">(</span><span class="n">Port</span><span class="p" data-group-id="9725587070-39">)</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">stop</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6740567720-40">{</span><span class="nf">self</span><span class="p" data-group-id="6740567720-41">(</span><span class="p" data-group-id="6740567720-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="6740567720-40">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9725587070-40">{</span><span class="nf">self</span><span class="p" data-group-id="9725587070-41">(</span><span class="p" data-group-id="9725587070-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="9725587070-40">}</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="6740567720-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="6740567720-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="nf">exit</span><span class="p" data-group-id="6740567720-43">(</span><span class="ss">normal</span><span class="p" data-group-id="6740567720-43">)</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="9725587070-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="9725587070-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="nf">exit</span><span class="p" data-group-id="9725587070-43">(</span><span class="ss">normal</span><span class="p" data-group-id="9725587070-43">)</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="6740567720-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="6740567720-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="nf">exit</span><span class="p" data-group-id="6740567720-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="6740567720-45">)</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="9725587070-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="9725587070-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	    </span><span class="nf">exit</span><span class="p" data-group-id="9725587070-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="9725587070-45">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Notice that calling <code class="inline">complex2:foo/1</code> and <code class="inline">complex2:bar/1</code> results in the tuple
│ │ │ │  <code class="inline">{foo,X}</code> or <code class="inline">{bar,Y}</code> being sent to the <code class="inline">complex</code> process, which codes them as
│ │ │ │  binaries and sends them to the port. This means that the C program must be able
│ │ │ │  to handle these two tuples.</p><h2 id="c-program" class="section-heading">
│ │ │ │    <a href="#c-program" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │ @@ -267,24 +267,24 @@
│ │ │ │      -L/usr/local/otp/lib/erl_interface-3.9.2/lib \
│ │ │ │      complex.c erl_comm.c ei.c -lei -lpthread</code></pre><p>In Erlang/OTP R5B and later versions of OTP, the <code class="inline">include</code> and <code class="inline">lib</code> directories
│ │ │ │  are situated under <code class="inline">$OTPROOT/lib/erl_interface-VSN</code>, where <code class="inline">$OTPROOT</code> is the
│ │ │ │  root directory of the OTP installation (<code class="inline">/usr/local/otp</code> in the recent example)
│ │ │ │  and <code class="inline">VSN</code> is the version of the Erl_interface application (3.2.1 in the recent
│ │ │ │  example).</p><p>In R4B and earlier versions of OTP, <code class="inline">include</code> and <code class="inline">lib</code> are situated under
│ │ │ │  <code class="inline">$OTPROOT/usr</code>.</p><p><em>Step 2.</em> Start Erlang and compile the Erlang code:</p><pre><code class="makeup erlang" translate="no"><span class="sc">$ </span><span class="ss">erl</span><span class="w">
│ │ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="6653195922-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="6653195922-1">]</span><span class="w"> </span><span class="p" data-group-id="6653195922-2">[</span><span class="ss">source</span><span class="p" data-group-id="6653195922-2">]</span><span class="w"> </span><span class="p" data-group-id="6653195922-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="6653195922-3">]</span><span class="w"> </span><span class="p" data-group-id="6653195922-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="6653195922-4">]</span><span class="w"> </span><span class="p" data-group-id="6653195922-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="6653195922-5">]</span><span class="w"> </span><span class="p" data-group-id="6653195922-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="6653195922-6">]</span><span class="w"> </span><span class="p" data-group-id="6653195922-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="6653195922-7">]</span><span class="w">
│ │ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="4033370125-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="4033370125-1">]</span><span class="w"> </span><span class="p" data-group-id="4033370125-2">[</span><span class="ss">source</span><span class="p" data-group-id="4033370125-2">]</span><span class="w"> </span><span class="p" data-group-id="4033370125-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="4033370125-3">]</span><span class="w"> </span><span class="p" data-group-id="4033370125-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="4033370125-4">]</span><span class="w"> </span><span class="p" data-group-id="4033370125-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="4033370125-5">]</span><span class="w"> </span><span class="p" data-group-id="4033370125-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4033370125-6">]</span><span class="w"> </span><span class="p" data-group-id="4033370125-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="4033370125-7">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="6653195922-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="6653195922-9">(</span><span class="p" data-group-id="6653195922-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="6653195922-8">)</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="6653195922-10">(</span><span class="ss">complex2</span><span class="p" data-group-id="6653195922-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6653195922-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex2</span><span class="p" data-group-id="6653195922-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="7285264914-1">(</span><span class="s">&quot;./extprg&quot;</span><span class="p" data-group-id="7285264914-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="4033370125-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="4033370125-9">(</span><span class="p" data-group-id="4033370125-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="4033370125-8">)</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="4033370125-10">(</span><span class="ss">complex2</span><span class="p" data-group-id="4033370125-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4033370125-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex2</span><span class="p" data-group-id="4033370125-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8190170424-1">(</span><span class="s">&quot;./extprg&quot;</span><span class="p" data-group-id="8190170424-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">0.34</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="7285264914-2">(</span><span class="mi">3</span><span class="p" data-group-id="7285264914-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="8190170424-2">(</span><span class="mi">3</span><span class="p" data-group-id="8190170424-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="7285264914-3">(</span><span class="mi">5</span><span class="p" data-group-id="7285264914-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="8190170424-3">(</span><span class="mi">5</span><span class="p" data-group-id="8190170424-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">10</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="7285264914-4">(</span><span class="mi">352</span><span class="p" data-group-id="7285264914-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="8190170424-4">(</span><span class="mi">352</span><span class="p" data-group-id="8190170424-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">704</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="7285264914-5">(</span><span class="p" data-group-id="7285264914-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="8190170424-5">(</span><span class="p" data-group-id="8190170424-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">stop</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/eff_guide_processes.xhtml
│ │ │ │ @@ -24,45 +24,45 @@
│ │ │ │    <a href="#creating-an-erlang-process" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Creating an Erlang Process</span>
│ │ │ │  </h2>
│ │ │ │  <p>An Erlang process is lightweight compared to threads and processes in operating
│ │ │ │  systems.</p><p>A newly spawned Erlang process uses 327 words of memory. The size can be found
│ │ │ │ -as follows:</p><pre><code class="makeup erlang" translate="no"><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="3198035966-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p">.</span><span class="mi">3</span><span class="p" data-group-id="3198035966-1">]</span><span class="w"> </span><span class="p" data-group-id="3198035966-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="3198035966-2">]</span><span class="w"> </span><span class="p" data-group-id="3198035966-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="3198035966-3">]</span><span class="w"> </span><span class="p" data-group-id="3198035966-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="3198035966-4">]</span><span class="w"> </span><span class="p" data-group-id="3198035966-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="3198035966-5">]</span><span class="w"> </span><span class="p" data-group-id="3198035966-6">[</span><span class="ss">jit</span><span class="p" data-group-id="3198035966-6">]</span><span class="w">
│ │ │ │ +as follows:</p><pre><code class="makeup erlang" translate="no"><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="7300436490-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p">.</span><span class="mi">3</span><span class="p" data-group-id="7300436490-1">]</span><span class="w"> </span><span class="p" data-group-id="7300436490-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="7300436490-2">]</span><span class="w"> </span><span class="p" data-group-id="7300436490-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="7300436490-3">]</span><span class="w"> </span><span class="p" data-group-id="7300436490-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="7300436490-4">]</span><span class="w"> </span><span class="p" data-group-id="7300436490-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="7300436490-5">]</span><span class="w"> </span><span class="p" data-group-id="7300436490-6">[</span><span class="ss">jit</span><span class="p" data-group-id="7300436490-6">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mf">2.3</span><span class="w"> </span><span class="p" data-group-id="3198035966-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="3198035966-8">(</span><span class="p" data-group-id="3198035966-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="3198035966-7">)</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3198035966-9">(</span><span class="p" data-group-id="3198035966-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="k">after</span><span class="w"> </span><span class="ss">infinity</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mf">2.3</span><span class="w"> </span><span class="p" data-group-id="7300436490-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="7300436490-8">(</span><span class="p" data-group-id="7300436490-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="7300436490-7">)</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="7300436490-9">(</span><span class="p" data-group-id="7300436490-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="k">after</span><span class="w"> </span><span class="ss">infinity</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">43.39164016</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="3198035966-10">{</span><span class="p">_</span><span class="p">,</span><span class="n">Bytes</span><span class="p" data-group-id="3198035966-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">process_info</span><span class="p" data-group-id="3198035966-11">(</span><span class="nf">spawn</span><span class="p" data-group-id="3198035966-12">(</span><span class="n">Fun</span><span class="p" data-group-id="3198035966-12">)</span><span class="p">,</span><span class="w"> </span><span class="nb">memory</span><span class="p" data-group-id="3198035966-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3198035966-13">{</span><span class="nb">memory</span><span class="p">,</span><span class="mi">2616</span><span class="p" data-group-id="3198035966-13">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="n">Bytes</span><span class="w"> </span><span class="ow">div</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="3198035966-14">(</span><span class="ss">wordsize</span><span class="p" data-group-id="3198035966-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="7300436490-10">{</span><span class="p">_</span><span class="p">,</span><span class="n">Bytes</span><span class="p" data-group-id="7300436490-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">process_info</span><span class="p" data-group-id="7300436490-11">(</span><span class="nf">spawn</span><span class="p" data-group-id="7300436490-12">(</span><span class="n">Fun</span><span class="p" data-group-id="7300436490-12">)</span><span class="p">,</span><span class="w"> </span><span class="nb">memory</span><span class="p" data-group-id="7300436490-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7300436490-13">{</span><span class="nb">memory</span><span class="p">,</span><span class="mi">2616</span><span class="p" data-group-id="7300436490-13">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="n">Bytes</span><span class="w"> </span><span class="ow">div</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="7300436490-14">(</span><span class="ss">wordsize</span><span class="p" data-group-id="7300436490-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">327</span></code></pre><p>The size includes 233 words for the heap area (which includes the stack). The
│ │ │ │  garbage collector increases the heap as needed.</p><p>The main (outer) loop for a process <em>must</em> be tail-recursive. Otherwise, the
│ │ │ │ -stack grows until the process terminates.</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="4261023529-1">(</span><span class="p" data-group-id="4261023529-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +stack grows until the process terminates.</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="4828172441-1">(</span><span class="p" data-group-id="4828172441-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │    </span><span class="k">receive</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="4261023529-2">{</span><span class="ss">sys</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4261023529-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -         </span><span class="nf">handle_sys_msg</span><span class="p" data-group-id="4261023529-3">(</span><span class="n">Msg</span><span class="p" data-group-id="4261023529-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="nf">loop</span><span class="p" data-group-id="4261023529-4">(</span><span class="p" data-group-id="4261023529-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="4261023529-5">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4261023529-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -          </span><span class="n">Reply</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="4261023529-6">(</span><span class="n">Msg</span><span class="p" data-group-id="4261023529-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="4828172441-2">{</span><span class="ss">sys</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4828172441-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +         </span><span class="nf">handle_sys_msg</span><span class="p" data-group-id="4828172441-3">(</span><span class="n">Msg</span><span class="p" data-group-id="4828172441-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="nf">loop</span><span class="p" data-group-id="4828172441-4">(</span><span class="p" data-group-id="4828172441-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="4828172441-5">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4828172441-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +          </span><span class="n">Reply</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="4828172441-6">(</span><span class="n">Msg</span><span class="p" data-group-id="4828172441-6">)</span><span class="p">,</span><span class="w">
│ │ │ │            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Reply</span><span class="p">,</span><span class="w">
│ │ │ │ -          </span><span class="nf">loop</span><span class="p" data-group-id="4261023529-7">(</span><span class="p" data-group-id="4261023529-7">)</span><span class="w">
│ │ │ │ +          </span><span class="nf">loop</span><span class="p" data-group-id="4828172441-7">(</span><span class="p" data-group-id="4828172441-7">)</span><span class="w">
│ │ │ │    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4261023529-8">(</span><span class="s">&quot;Message is processed</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4261023529-9">[</span><span class="p" data-group-id="4261023529-9">]</span><span class="p" data-group-id="4261023529-8">)</span><span class="p">.</span></code></pre><p>The call to <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> will never be executed, but a return address will
│ │ │ │ +  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4828172441-8">(</span><span class="s">&quot;Message is processed</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4828172441-9">[</span><span class="p" data-group-id="4828172441-9">]</span><span class="p" data-group-id="4828172441-8">)</span><span class="p">.</span></code></pre><p>The call to <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> will never be executed, but a return address will
│ │ │ │  still be pushed to the stack each time <code class="inline">loop/0</code> is called recursively. The
│ │ │ │ -correct tail-recursive version of the function looks as follows:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="0901371901-1">(</span><span class="p" data-group-id="0901371901-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +correct tail-recursive version of the function looks as follows:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="4064229089-1">(</span><span class="p" data-group-id="4064229089-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │     </span><span class="k">receive</span><span class="w">
│ │ │ │ -      </span><span class="p" data-group-id="0901371901-2">{</span><span class="ss">sys</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0901371901-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -         </span><span class="nf">handle_sys_msg</span><span class="p" data-group-id="0901371901-3">(</span><span class="n">Msg</span><span class="p" data-group-id="0901371901-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="nf">loop</span><span class="p" data-group-id="0901371901-4">(</span><span class="p" data-group-id="0901371901-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -      </span><span class="p" data-group-id="0901371901-5">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0901371901-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -         </span><span class="n">Reply</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="0901371901-6">(</span><span class="n">Msg</span><span class="p" data-group-id="0901371901-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +      </span><span class="p" data-group-id="4064229089-2">{</span><span class="ss">sys</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4064229089-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +         </span><span class="nf">handle_sys_msg</span><span class="p" data-group-id="4064229089-3">(</span><span class="n">Msg</span><span class="p" data-group-id="4064229089-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="nf">loop</span><span class="p" data-group-id="4064229089-4">(</span><span class="p" data-group-id="4064229089-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +      </span><span class="p" data-group-id="4064229089-5">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4064229089-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +         </span><span class="n">Reply</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="4064229089-6">(</span><span class="n">Msg</span><span class="p" data-group-id="4064229089-6">)</span><span class="p">,</span><span class="w">
│ │ │ │           </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Reply</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="nf">loop</span><span class="p" data-group-id="0901371901-7">(</span><span class="p" data-group-id="0901371901-7">)</span><span class="w">
│ │ │ │ +         </span><span class="nf">loop</span><span class="p" data-group-id="4064229089-7">(</span><span class="p" data-group-id="4064229089-7">)</span><span class="w">
│ │ │ │   </span><span class="k">end</span><span class="p">.</span></code></pre><h3 id="initial-heap-size" class="section-heading">
│ │ │ │    <a href="#initial-heap-size" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Initial Heap Size</span>
│ │ │ │  </h3>
│ │ │ │  <p>The default initial heap size of 233 words is quite conservative to support
│ │ │ │ @@ -95,30 +95,30 @@
│ │ │ │    </a>
│ │ │ │    <span class="text">Fetching Received Messages</span>
│ │ │ │  </h2>
│ │ │ │  <p>The cost of fetching a received message from the message queue depends on how
│ │ │ │  complicated the <code class="inline">receive</code> expression is. A simple expression that matches any
│ │ │ │  message is very cheap because it retrieves the first message in the message
│ │ │ │  queue:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="n">Message</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="0716480488-1">(</span><span class="n">Message</span><span class="p" data-group-id="0716480488-1">)</span><span class="w">
│ │ │ │ +    </span><span class="n">Message</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="7387684088-1">(</span><span class="n">Message</span><span class="p" data-group-id="7387684088-1">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>However, this is not always convenient: we can receive a message that we do not
│ │ │ │  know how to handle at this point, so it is common to only match the messages we
│ │ │ │  expect:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3919504054-1">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3919504054-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="3919504054-2">(</span><span class="n">Message</span><span class="p" data-group-id="3919504054-2">)</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8885868178-1">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="8885868178-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="8885868178-2">(</span><span class="n">Message</span><span class="p" data-group-id="8885868178-2">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>While this is convenient it means that the entire message queue must be searched
│ │ │ │  until it finds a matching message. This is very expensive for processes with
│ │ │ │  long message queues, so there is an optimization for the common case of
│ │ │ │ -sending a request and waiting for a response shortly after:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">MRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="8240741496-1">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">Process</span><span class="p" data-group-id="8240741496-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8240741496-2">{</span><span class="nf">self</span><span class="p" data-group-id="8240741496-3">(</span><span class="p" data-group-id="8240741496-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="8240741496-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +sending a request and waiting for a response shortly after:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">MRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="6633358047-1">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">Process</span><span class="p" data-group-id="6633358047-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6633358047-2">{</span><span class="nf">self</span><span class="p" data-group-id="6633358047-3">(</span><span class="p" data-group-id="6633358047-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="6633358047-2">}</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8240741496-4">{</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="p" data-group-id="8240741496-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">demonitor</span><span class="p" data-group-id="8240741496-5">(</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8240741496-6">[</span><span class="ss">flush</span><span class="p" data-group-id="8240741496-6">]</span><span class="p" data-group-id="8240741496-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="nf">handle_reply</span><span class="p" data-group-id="8240741496-7">(</span><span class="n">Reply</span><span class="p" data-group-id="8240741496-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8240741496-8">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="8240741496-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nf">handle_error</span><span class="p" data-group-id="8240741496-9">(</span><span class="n">Reason</span><span class="p" data-group-id="8240741496-9">)</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6633358047-4">{</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="p" data-group-id="6633358047-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">demonitor</span><span class="p" data-group-id="6633358047-5">(</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6633358047-6">[</span><span class="ss">flush</span><span class="p" data-group-id="6633358047-6">]</span><span class="p" data-group-id="6633358047-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="nf">handle_reply</span><span class="p" data-group-id="6633358047-7">(</span><span class="n">Reply</span><span class="p" data-group-id="6633358047-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6633358047-8">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="6633358047-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nf">handle_error</span><span class="p" data-group-id="6633358047-9">(</span><span class="n">Reason</span><span class="p" data-group-id="6633358047-9">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>Since the compiler knows that the reference created by
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#monitor/2"><code class="inline">monitor/2</code></a> cannot exist before the call (since it is a globally
│ │ │ │  unique identifier), and that the <code class="inline">receive</code> only matches messages that contain
│ │ │ │  said reference, it will tell the emulator to search only the messages that
│ │ │ │  arrived after the call to <a href="../../../lib/../erts/doc/html/erlang.html#monitor/2"><code class="inline">monitor/2</code></a>.</p><p>The above is a simple example where one is guaranteed that the optimization
│ │ │ │  will take, but what about more complicated code?</p><p><a href="" id="recv_opt_info"></a></p><h3 id="option-recv_opt_info" class="section-heading">
│ │ │ │    <a href="#option-recv_opt_info" class="hover-link">
│ │ │ │ @@ -134,101 +134,101 @@
│ │ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">200</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">NOT</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">all</span><span class="w"> </span><span class="ss">clauses</span><span class="w"> </span><span class="ss">do</span><span class="w"> </span><span class="ow">not</span><span class="w"> </span><span class="ss">match</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="ss">suitable</span><span class="w"> </span><span class="ss">reference</span><span class="w">
│ │ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">206</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">reference</span><span class="w"> </span><span class="ss">used</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">mark</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="ss">message</span><span class="w"> </span><span class="ss">queue</span><span class="w"> </span><span class="ss">position</span><span class="w">
│ │ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">208</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">all</span><span class="w"> </span><span class="ss">clauses</span><span class="w"> </span><span class="ss">match</span><span class="w"> </span><span class="ss">reference</span><span class="w"> </span><span class="ss">created</span><span class="w"> </span><span class="ss">by</span><span class="w"> </span><span class="nb">monitor</span><span class="p">/</span><span class="mi">2</span><span class="w"> </span><span class="ss">at</span><span class="w"> </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">206</span><span class="w">
│ │ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">219</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">INFO</span><span class="p">:</span><span class="w"> </span><span class="ss">passing</span><span class="w"> </span><span class="ss">reference</span><span class="w"> </span><span class="ss">created</span><span class="w"> </span><span class="ss">by</span><span class="w"> </span><span class="ss">make_ref</span><span class="p">/</span><span class="mi">0</span><span class="w"> </span><span class="ss">at</span><span class="w"> </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">218</span><span class="w">
│ │ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">222</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">all</span><span class="w"> </span><span class="ss">clauses</span><span class="w"> </span><span class="ss">match</span><span class="w"> </span><span class="ss">reference</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">function</span><span class="w"> </span><span class="ss">parameter</span><span class="w"> </span><span class="mi">1</span></code></pre><p>To make it clearer exactly what code the warnings refer to, the warnings in the
│ │ │ │  following examples are inserted as comments after the clause they refer to, for
│ │ │ │  example:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="nf">simple_receive</span><span class="p" data-group-id="9468930989-1">(</span><span class="p" data-group-id="9468930989-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">simple_receive</span><span class="p" data-group-id="9520172333-1">(</span><span class="p" data-group-id="9520172333-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="c1">%% efficiency_guide.erl:194: Warning: INFO: not a selective receive, this is always fast</span><span class="w">
│ │ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="n">Message</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="9468930989-2">(</span><span class="n">Message</span><span class="p" data-group-id="9468930989-2">)</span><span class="w">
│ │ │ │ +    </span><span class="n">Message</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="9520172333-2">(</span><span class="n">Message</span><span class="p" data-group-id="9520172333-2">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO NOT, unless Tag is known to be a suitable reference: see</span><span class="w">
│ │ │ │  </span><span class="c1">%% cross_function_receive/0 further down.</span><span class="w">
│ │ │ │ -</span><span class="nf">selective_receive</span><span class="p" data-group-id="9468930989-3">(</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9468930989-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">selective_receive</span><span class="p" data-group-id="9520172333-3">(</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9520172333-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="c1">%% efficiency_guide.erl:200: Warning: NOT OPTIMIZED: all clauses do not match a suitable reference</span><span class="w">
│ │ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9468930989-4">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9468930989-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="9468930989-5">(</span><span class="n">Message</span><span class="p" data-group-id="9468930989-5">)</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9520172333-4">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9520172333-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="9520172333-5">(</span><span class="n">Message</span><span class="p" data-group-id="9520172333-5">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="nf">optimized_receive</span><span class="p" data-group-id="9468930989-6">(</span><span class="n">Process</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="9468930989-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">optimized_receive</span><span class="p" data-group-id="9520172333-6">(</span><span class="n">Process</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="9520172333-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="c1">%% efficiency_guide.erl:206: Warning: OPTIMIZED: reference used to mark a message queue position</span><span class="w">
│ │ │ │ -    </span><span class="n">MRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="9468930989-7">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">Process</span><span class="p" data-group-id="9468930989-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9468930989-8">{</span><span class="nf">self</span><span class="p" data-group-id="9468930989-9">(</span><span class="p" data-group-id="9468930989-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="9468930989-8">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">MRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="9520172333-7">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">Process</span><span class="p" data-group-id="9520172333-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9520172333-8">{</span><span class="nf">self</span><span class="p" data-group-id="9520172333-9">(</span><span class="p" data-group-id="9520172333-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="9520172333-8">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="c1">%% efficiency_guide.erl:208: Warning: OPTIMIZED: matches reference created by monitor/2 at efficiency_guide.erl:206</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="9468930989-10">{</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="p" data-group-id="9468930989-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">demonitor</span><span class="p" data-group-id="9468930989-11">(</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9468930989-12">[</span><span class="ss">flush</span><span class="p" data-group-id="9468930989-12">]</span><span class="p" data-group-id="9468930989-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="nf">handle_reply</span><span class="p" data-group-id="9468930989-13">(</span><span class="n">Reply</span><span class="p" data-group-id="9468930989-13">)</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9468930989-14">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="9468930989-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">handle_error</span><span class="p" data-group-id="9468930989-15">(</span><span class="n">Reason</span><span class="p" data-group-id="9468930989-15">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9520172333-10">{</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="p" data-group-id="9520172333-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">demonitor</span><span class="p" data-group-id="9520172333-11">(</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9520172333-12">[</span><span class="ss">flush</span><span class="p" data-group-id="9520172333-12">]</span><span class="p" data-group-id="9520172333-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="nf">handle_reply</span><span class="p" data-group-id="9520172333-13">(</span><span class="n">Reply</span><span class="p" data-group-id="9520172333-13">)</span><span class="p">;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9520172333-14">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="9520172333-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">handle_error</span><span class="p" data-group-id="9520172333-15">(</span><span class="n">Reason</span><span class="p" data-group-id="9520172333-15">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="nf">cross_function_receive</span><span class="p" data-group-id="9468930989-16">(</span><span class="p" data-group-id="9468930989-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">cross_function_receive</span><span class="p" data-group-id="9520172333-16">(</span><span class="p" data-group-id="9520172333-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% efficiency_guide.erl:218: Warning: OPTIMIZED: reference used to mark a message queue position</span><span class="w">
│ │ │ │ -    </span><span class="n">Ref</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="9468930989-17">(</span><span class="p" data-group-id="9468930989-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Ref</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="9520172333-17">(</span><span class="p" data-group-id="9520172333-17">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="c1">%% efficiency_guide.erl:219: Warning: INFO: passing reference created by make_ref/0 at efficiency_guide.erl:218</span><span class="w">
│ │ │ │ -    </span><span class="nf">cross_function_receive</span><span class="p" data-group-id="9468930989-18">(</span><span class="n">Ref</span><span class="p" data-group-id="9468930989-18">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">cross_function_receive</span><span class="p" data-group-id="9520172333-18">(</span><span class="n">Ref</span><span class="p" data-group-id="9520172333-18">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">cross_function_receive</span><span class="p" data-group-id="9468930989-19">(</span><span class="n">Ref</span><span class="p" data-group-id="9468930989-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">cross_function_receive</span><span class="p" data-group-id="9520172333-19">(</span><span class="n">Ref</span><span class="p" data-group-id="9520172333-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% efficiency_guide.erl:222: Warning: OPTIMIZED: all clauses match reference in function parameter 1</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="9468930989-20">{</span><span class="n">Ref</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9468930989-20">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="9468930989-21">(</span><span class="n">Message</span><span class="p" data-group-id="9468930989-21">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9520172333-20">{</span><span class="n">Ref</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9520172333-20">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="9520172333-21">(</span><span class="n">Message</span><span class="p" data-group-id="9520172333-21">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><h2 id="literal-pool" class="section-heading">
│ │ │ │    <a href="#literal-pool" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Literal Pool</span>
│ │ │ │  </h2>
│ │ │ │  <p>Constant Erlang terms (hereafter called <em>literals</em>) are kept in <em>literal pools</em>;
│ │ │ │  each loaded module has its own pool. The following function does not build the
│ │ │ │  tuple every time it is called (only to have it discarded the next time the
│ │ │ │  garbage collector was run), but the tuple is located in the module's literal
│ │ │ │ -pool:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">days_in_month</span><span class="p" data-group-id="1104551875-1">(</span><span class="n">M</span><span class="p" data-group-id="1104551875-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">element</span><span class="p" data-group-id="1104551875-2">(</span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1104551875-3">{</span><span class="mi">31</span><span class="p">,</span><span class="mi">28</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p" data-group-id="1104551875-3">}</span><span class="p" data-group-id="1104551875-2">)</span><span class="p">.</span></code></pre><p>If a literal, or a term that contains a literal, is inserted into an Ets table,
│ │ │ │ +pool:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">days_in_month</span><span class="p" data-group-id="4908682197-1">(</span><span class="n">M</span><span class="p" data-group-id="4908682197-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">element</span><span class="p" data-group-id="4908682197-2">(</span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4908682197-3">{</span><span class="mi">31</span><span class="p">,</span><span class="mi">28</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p" data-group-id="4908682197-3">}</span><span class="p" data-group-id="4908682197-2">)</span><span class="p">.</span></code></pre><p>If a literal, or a term that contains a literal, is inserted into an Ets table,
│ │ │ │  it is <em>copied</em>. The reason is that the module containing the literal can be
│ │ │ │  unloaded in the future.</p><p>When a literal is sent to another process, it is <em>not</em> copied. When a module
│ │ │ │  holding a literal is unloaded, the literal will be copied to the heap of all
│ │ │ │  processes that hold references to that literal.</p><p>There also exists a global literal pool that is managed by the
│ │ │ │  <a href="../../../lib/../erts/doc/html/persistent_term.html"><code class="inline">persistent_term</code></a> module.</p><p>By default, 1 GB of virtual address space is reserved for all literal pools (in
│ │ │ │  BEAM code and persistent terms). The amount of virtual address space reserved
│ │ │ │  for literals can be changed by using the
│ │ │ │  <a href="../../../lib/../erts/doc/html/erts_alloc.xhtml#MIscs"><code class="inline">+MIscs option</code></a> when starting the emulator.</p><p>Here is an example of how the reserved virtual address space for literals can be
│ │ │ │  raised to 2 GB (2048 MB):</p><pre><code class="text">erl +MIscs 2048</code></pre><h2 id="loss-of-sharing" class="section-heading">
│ │ │ │    <a href="#loss-of-sharing" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Loss of Sharing</span>
│ │ │ │  </h2>
│ │ │ │ -<p>An Erlang term can have shared subterms. Here is a simple example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8839667532-1">{</span><span class="n">SubTerm</span><span class="p">,</span><span class="w"> </span><span class="n">SubTerm</span><span class="p" data-group-id="8839667532-1">}</span></code></pre><p>Shared subterms are <em>not</em> preserved in the following cases:</p><ul><li>When a term is sent to another process</li><li>When a term is passed as the initial process arguments in the <code class="inline">spawn</code> call</li><li>When a term is stored in an Ets table</li></ul><p>That is an optimization. Most applications do not send messages with shared
│ │ │ │ -subterms.</p><p>The following example shows how a shared subterm can be created:</p><pre><code class="makeup erlang" translate="no"><span class="nf">kilo_byte</span><span class="p" data-group-id="5856961638-1">(</span><span class="p" data-group-id="5856961638-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">kilo_byte</span><span class="p" data-group-id="5856961638-2">(</span><span class="mi">10</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5856961638-3">[</span><span class="mi">42</span><span class="p" data-group-id="5856961638-3">]</span><span class="p" data-group-id="5856961638-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>An Erlang term can have shared subterms. Here is a simple example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9557966023-1">{</span><span class="n">SubTerm</span><span class="p">,</span><span class="w"> </span><span class="n">SubTerm</span><span class="p" data-group-id="9557966023-1">}</span></code></pre><p>Shared subterms are <em>not</em> preserved in the following cases:</p><ul><li>When a term is sent to another process</li><li>When a term is passed as the initial process arguments in the <code class="inline">spawn</code> call</li><li>When a term is stored in an Ets table</li></ul><p>That is an optimization. Most applications do not send messages with shared
│ │ │ │ +subterms.</p><p>The following example shows how a shared subterm can be created:</p><pre><code class="makeup erlang" translate="no"><span class="nf">kilo_byte</span><span class="p" data-group-id="5065647422-1">(</span><span class="p" data-group-id="5065647422-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">kilo_byte</span><span class="p" data-group-id="5065647422-2">(</span><span class="mi">10</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5065647422-3">[</span><span class="mi">42</span><span class="p" data-group-id="5065647422-3">]</span><span class="p" data-group-id="5065647422-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">kilo_byte</span><span class="p" data-group-id="5856961638-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5856961638-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">kilo_byte</span><span class="p" data-group-id="5065647422-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5065647422-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Acc</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">kilo_byte</span><span class="p" data-group-id="5856961638-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5856961638-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">kilo_byte</span><span class="p" data-group-id="5856961638-6">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5856961638-7">[</span><span class="n">Acc</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="5856961638-7">]</span><span class="p" data-group-id="5856961638-6">)</span><span class="p">.</span></code></pre><p><code class="inline">kilo_byte/1</code> creates a deep list. If <a href="../../../lib/../erts/doc/html/erlang.html#list_to_binary/1"><code class="inline">list_to_binary/1</code></a>
│ │ │ │ +</span><span class="nf">kilo_byte</span><span class="p" data-group-id="5065647422-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5065647422-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">kilo_byte</span><span class="p" data-group-id="5065647422-6">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5065647422-7">[</span><span class="n">Acc</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="5065647422-7">]</span><span class="p" data-group-id="5065647422-6">)</span><span class="p">.</span></code></pre><p><code class="inline">kilo_byte/1</code> creates a deep list. If <a href="../../../lib/../erts/doc/html/erlang.html#list_to_binary/1"><code class="inline">list_to_binary/1</code></a>
│ │ │ │  is called, the deep list can be converted to a binary of 1024 bytes:</p><pre><code class="text">1&gt; byte_size(list_to_binary(efficiency_guide:kilo_byte())).
│ │ │ │  1024</code></pre><p>Using the <code class="inline">erts_debug:size/1</code> BIF, it can be seen that the deep list only
│ │ │ │ -requires 22 words of heap space:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">size</span><span class="p" data-group-id="5626278029-1">(</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="5626278029-2">(</span><span class="p" data-group-id="5626278029-2">)</span><span class="p" data-group-id="5626278029-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +requires 22 words of heap space:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">size</span><span class="p" data-group-id="9193756042-1">(</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="9193756042-2">(</span><span class="p" data-group-id="9193756042-2">)</span><span class="p" data-group-id="9193756042-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">22</span></code></pre><p>Using the <code class="inline">erts_debug:flat_size/1</code> BIF, the size of the deep list can be
│ │ │ │  calculated if sharing is ignored. It becomes the size of the list when it has
│ │ │ │ -been sent to another process or stored in an Ets table:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">flat_size</span><span class="p" data-group-id="4880332663-1">(</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="4880332663-2">(</span><span class="p" data-group-id="4880332663-2">)</span><span class="p" data-group-id="4880332663-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +been sent to another process or stored in an Ets table:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">flat_size</span><span class="p" data-group-id="8347619699-1">(</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="8347619699-2">(</span><span class="p" data-group-id="8347619699-2">)</span><span class="p" data-group-id="8347619699-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4094</span></code></pre><p>It can be verified that sharing will be lost if the data is inserted into an Ets
│ │ │ │ -table:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="n">T</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="1229942618-1">(</span><span class="ss">tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1229942618-2">[</span><span class="p" data-group-id="1229942618-2">]</span><span class="p" data-group-id="1229942618-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +table:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="n">T</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="9374389607-1">(</span><span class="ss">tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9374389607-2">[</span><span class="p" data-group-id="9374389607-2">]</span><span class="p" data-group-id="9374389607-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Ref</span><span class="o">&lt;</span><span class="mf">0.1662103692</span><span class="p">.</span><span class="mf">2407923716.214181</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">ets</span><span class="p">:</span><span class="nf">insert</span><span class="p" data-group-id="1229942618-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1229942618-4">{</span><span class="ss">key</span><span class="p">,</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="1229942618-5">(</span><span class="p" data-group-id="1229942618-5">)</span><span class="p" data-group-id="1229942618-4">}</span><span class="p" data-group-id="1229942618-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">ets</span><span class="p">:</span><span class="nf">insert</span><span class="p" data-group-id="9374389607-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9374389607-4">{</span><span class="ss">key</span><span class="p">,</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="9374389607-5">(</span><span class="p" data-group-id="9374389607-5">)</span><span class="p" data-group-id="9374389607-4">}</span><span class="p" data-group-id="9374389607-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">size</span><span class="p" data-group-id="1229942618-6">(</span><span class="nf">element</span><span class="p" data-group-id="1229942618-7">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="nf">hd</span><span class="p" data-group-id="1229942618-8">(</span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1229942618-9">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="ss">key</span><span class="p" data-group-id="1229942618-9">)</span><span class="p" data-group-id="1229942618-8">)</span><span class="p" data-group-id="1229942618-7">)</span><span class="p" data-group-id="1229942618-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">size</span><span class="p" data-group-id="9374389607-6">(</span><span class="nf">element</span><span class="p" data-group-id="9374389607-7">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="nf">hd</span><span class="p" data-group-id="9374389607-8">(</span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="9374389607-9">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="ss">key</span><span class="p" data-group-id="9374389607-9">)</span><span class="p" data-group-id="9374389607-8">)</span><span class="p" data-group-id="9374389607-7">)</span><span class="p" data-group-id="9374389607-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4094</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">7&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">flat_size</span><span class="p" data-group-id="1229942618-10">(</span><span class="nf">element</span><span class="p" data-group-id="1229942618-11">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="nf">hd</span><span class="p" data-group-id="1229942618-12">(</span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1229942618-13">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="ss">key</span><span class="p" data-group-id="1229942618-13">)</span><span class="p" data-group-id="1229942618-12">)</span><span class="p" data-group-id="1229942618-11">)</span><span class="p" data-group-id="1229942618-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">7&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">flat_size</span><span class="p" data-group-id="9374389607-10">(</span><span class="nf">element</span><span class="p" data-group-id="9374389607-11">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="nf">hd</span><span class="p" data-group-id="9374389607-12">(</span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="9374389607-13">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="ss">key</span><span class="p" data-group-id="9374389607-13">)</span><span class="p" data-group-id="9374389607-12">)</span><span class="p" data-group-id="9374389607-11">)</span><span class="p" data-group-id="9374389607-10">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4094</span></code></pre><p>When the data has passed through an Ets table, <code class="inline">erts_debug:size/1</code> and
│ │ │ │  <code class="inline">erts_debug:flat_size/1</code> return the same value. Sharing has been lost.</p><p>It is possible to build an <em>experimental</em> variant of the runtime system that
│ │ │ │  will preserve sharing when copying terms by giving the
│ │ │ │  <code class="inline">--enable-sharing-preserving</code> option to the <code class="inline">configure</code> script.</p><h2 id="smp-run-time-system" class="section-heading">
│ │ │ │    <a href="#smp-run-time-system" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ ├── OEBPS/eff_guide_functions.xhtml
│ │ │ │ @@ -27,67 +27,67 @@
│ │ │ │    <span class="text">Pattern Matching</span>
│ │ │ │  </h2>
│ │ │ │  <p>Pattern matching in function head as well as in <code class="inline">case</code> and <code class="inline">receive</code> clauses is
│ │ │ │  optimized by the compiler. With a few exceptions, there is nothing to gain by
│ │ │ │  rearranging clauses.</p><p>One exception is pattern matching of binaries. The compiler does not rearrange
│ │ │ │  clauses that match binaries. Placing the clause that matches against the empty
│ │ │ │  binary <em>last</em> is usually slightly faster than placing it <em>first</em>.</p><p>The following is a rather unnatural example to show another exception where
│ │ │ │ -rearranging clauses is beneficial:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map1</span><span class="p" data-group-id="9386000826-1">(</span><span class="ss">one</span><span class="p" data-group-id="9386000826-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9386000826-2">(</span><span class="ss">two</span><span class="p" data-group-id="9386000826-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9386000826-3">(</span><span class="ss">three</span><span class="p" data-group-id="9386000826-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9386000826-4">(</span><span class="n">Int</span><span class="p" data-group-id="9386000826-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="9386000826-5">(</span><span class="n">Int</span><span class="p" data-group-id="9386000826-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9386000826-6">(</span><span class="ss">four</span><span class="p" data-group-id="9386000826-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9386000826-7">(</span><span class="ss">five</span><span class="p" data-group-id="9386000826-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9386000826-8">(</span><span class="ss">six</span><span class="p" data-group-id="9386000826-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span></code></pre><p>The problem is the clause with the variable <code class="inline">Int</code>. As a variable can match
│ │ │ │ +rearranging clauses is beneficial:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map1</span><span class="p" data-group-id="9212899057-1">(</span><span class="ss">one</span><span class="p" data-group-id="9212899057-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="9212899057-2">(</span><span class="ss">two</span><span class="p" data-group-id="9212899057-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="9212899057-3">(</span><span class="ss">three</span><span class="p" data-group-id="9212899057-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="9212899057-4">(</span><span class="n">Int</span><span class="p" data-group-id="9212899057-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="9212899057-5">(</span><span class="n">Int</span><span class="p" data-group-id="9212899057-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="9212899057-6">(</span><span class="ss">four</span><span class="p" data-group-id="9212899057-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="9212899057-7">(</span><span class="ss">five</span><span class="p" data-group-id="9212899057-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="9212899057-8">(</span><span class="ss">six</span><span class="p" data-group-id="9212899057-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span></code></pre><p>The problem is the clause with the variable <code class="inline">Int</code>. As a variable can match
│ │ │ │  anything, including the atoms <code class="inline">four</code>, <code class="inline">five</code>, and <code class="inline">six</code>, which the following
│ │ │ │  clauses also match, the compiler must generate suboptimal code that executes as
│ │ │ │  follows:</p><ul><li>First, the input value is compared to <code class="inline">one</code>, <code class="inline">two</code>, and <code class="inline">three</code> (using a
│ │ │ │  single instruction that does a binary search; thus, quite efficient even if
│ │ │ │  there are many values) to select which one of the first three clauses to
│ │ │ │  execute (if any).</li><li>If none of the first three clauses match, the fourth clause matches as a
│ │ │ │  variable always matches.</li><li>If the guard test <a href="../../../lib/../erts/doc/html/erlang.html#is_integer/1"><code class="inline">is_integer(Int)</code></a> succeeds, the fourth
│ │ │ │  clause is executed.</li><li>If the guard test fails, the input value is compared to <code class="inline">four</code>, <code class="inline">five</code>, and
│ │ │ │  <code class="inline">six</code>, and the appropriate clause is selected. (There is a <code class="inline">function_clause</code>
│ │ │ │ -exception if none of the values matched.)</li></ul><p>Rewriting to either:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map2</span><span class="p" data-group-id="8673097043-1">(</span><span class="ss">one</span><span class="p" data-group-id="8673097043-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="8673097043-2">(</span><span class="ss">two</span><span class="p" data-group-id="8673097043-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="8673097043-3">(</span><span class="ss">three</span><span class="p" data-group-id="8673097043-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="8673097043-4">(</span><span class="ss">four</span><span class="p" data-group-id="8673097043-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="8673097043-5">(</span><span class="ss">five</span><span class="p" data-group-id="8673097043-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="8673097043-6">(</span><span class="ss">six</span><span class="p" data-group-id="8673097043-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="8673097043-7">(</span><span class="n">Int</span><span class="p" data-group-id="8673097043-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="8673097043-8">(</span><span class="n">Int</span><span class="p" data-group-id="8673097043-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>or:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map3</span><span class="p" data-group-id="4071014576-1">(</span><span class="n">Int</span><span class="p" data-group-id="4071014576-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="4071014576-2">(</span><span class="n">Int</span><span class="p" data-group-id="4071014576-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="4071014576-3">(</span><span class="ss">one</span><span class="p" data-group-id="4071014576-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="4071014576-4">(</span><span class="ss">two</span><span class="p" data-group-id="4071014576-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="4071014576-5">(</span><span class="ss">three</span><span class="p" data-group-id="4071014576-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="4071014576-6">(</span><span class="ss">four</span><span class="p" data-group-id="4071014576-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="4071014576-7">(</span><span class="ss">five</span><span class="p" data-group-id="4071014576-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="4071014576-8">(</span><span class="ss">six</span><span class="p" data-group-id="4071014576-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span></code></pre><p>gives slightly more efficient matching code.</p><p>Another example:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">map_pairs1</span><span class="p" data-group-id="1868750687-1">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1868750687-2">[</span><span class="p" data-group-id="1868750687-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="1868750687-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +exception if none of the values matched.)</li></ul><p>Rewriting to either:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map2</span><span class="p" data-group-id="3272936207-1">(</span><span class="ss">one</span><span class="p" data-group-id="3272936207-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="3272936207-2">(</span><span class="ss">two</span><span class="p" data-group-id="3272936207-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="3272936207-3">(</span><span class="ss">three</span><span class="p" data-group-id="3272936207-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="3272936207-4">(</span><span class="ss">four</span><span class="p" data-group-id="3272936207-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="3272936207-5">(</span><span class="ss">five</span><span class="p" data-group-id="3272936207-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="3272936207-6">(</span><span class="ss">six</span><span class="p" data-group-id="3272936207-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="3272936207-7">(</span><span class="n">Int</span><span class="p" data-group-id="3272936207-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="3272936207-8">(</span><span class="n">Int</span><span class="p" data-group-id="3272936207-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>or:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map3</span><span class="p" data-group-id="5166376614-1">(</span><span class="n">Int</span><span class="p" data-group-id="5166376614-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="5166376614-2">(</span><span class="n">Int</span><span class="p" data-group-id="5166376614-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="5166376614-3">(</span><span class="ss">one</span><span class="p" data-group-id="5166376614-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="5166376614-4">(</span><span class="ss">two</span><span class="p" data-group-id="5166376614-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="5166376614-5">(</span><span class="ss">three</span><span class="p" data-group-id="5166376614-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="5166376614-6">(</span><span class="ss">four</span><span class="p" data-group-id="5166376614-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="5166376614-7">(</span><span class="ss">five</span><span class="p" data-group-id="5166376614-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="5166376614-8">(</span><span class="ss">six</span><span class="p" data-group-id="5166376614-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span></code></pre><p>gives slightly more efficient matching code.</p><p>Another example:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">map_pairs1</span><span class="p" data-group-id="4751666214-1">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4751666214-2">[</span><span class="p" data-group-id="4751666214-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="4751666214-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Ys</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">map_pairs1</span><span class="p" data-group-id="1868750687-3">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1868750687-4">[</span><span class="p" data-group-id="1868750687-4">]</span><span class="p" data-group-id="1868750687-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">map_pairs1</span><span class="p" data-group-id="4751666214-3">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4751666214-4">[</span><span class="p" data-group-id="4751666214-4">]</span><span class="p" data-group-id="4751666214-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Xs</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">map_pairs1</span><span class="p" data-group-id="1868750687-5">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1868750687-6">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="1868750687-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1868750687-7">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="1868750687-7">]</span><span class="p" data-group-id="1868750687-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1868750687-8">[</span><span class="n">Map</span><span class="p" data-group-id="1868750687-9">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1868750687-9">)</span><span class="p">|</span><span class="nf">map_pairs1</span><span class="p" data-group-id="1868750687-10">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="1868750687-10">)</span><span class="p" data-group-id="1868750687-8">]</span><span class="p">.</span></code></pre><p>The first argument is <em>not</em> a problem. It is variable, but it is a variable in
│ │ │ │ +</span><span class="nf">map_pairs1</span><span class="p" data-group-id="4751666214-5">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4751666214-6">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="4751666214-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4751666214-7">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="4751666214-7">]</span><span class="p" data-group-id="4751666214-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4751666214-8">[</span><span class="n">Map</span><span class="p" data-group-id="4751666214-9">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4751666214-9">)</span><span class="p">|</span><span class="nf">map_pairs1</span><span class="p" data-group-id="4751666214-10">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="4751666214-10">)</span><span class="p" data-group-id="4751666214-8">]</span><span class="p">.</span></code></pre><p>The first argument is <em>not</em> a problem. It is variable, but it is a variable in
│ │ │ │  all clauses. The problem is the variable in the second argument, <code class="inline">Xs</code>, in the
│ │ │ │  middle clause. Because the variable can match anything, the compiler is not
│ │ │ │  allowed to rearrange the clauses, but must generate code that matches them in
│ │ │ │  the order written.</p><p>If the function is rewritten as follows, the compiler is free to rearrange the
│ │ │ │ -clauses:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">map_pairs2</span><span class="p" data-group-id="7664117604-1">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7664117604-2">[</span><span class="p" data-group-id="7664117604-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="7664117604-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +clauses:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">map_pairs2</span><span class="p" data-group-id="3237882446-1">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3237882446-2">[</span><span class="p" data-group-id="3237882446-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="3237882446-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Ys</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">map_pairs2</span><span class="p" data-group-id="7664117604-3">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7664117604-4">[</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="7664117604-4">]</span><span class="o">=</span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7664117604-5">[</span><span class="p" data-group-id="7664117604-5">]</span><span class="w"> </span><span class="p" data-group-id="7664117604-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">map_pairs2</span><span class="p" data-group-id="3237882446-3">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3237882446-4">[</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="3237882446-4">]</span><span class="o">=</span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3237882446-5">[</span><span class="p" data-group-id="3237882446-5">]</span><span class="w"> </span><span class="p" data-group-id="3237882446-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Xs</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">map_pairs2</span><span class="p" data-group-id="7664117604-6">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7664117604-7">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="7664117604-7">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7664117604-8">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="7664117604-8">]</span><span class="p" data-group-id="7664117604-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7664117604-9">[</span><span class="n">Map</span><span class="p" data-group-id="7664117604-10">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7664117604-10">)</span><span class="p">|</span><span class="nf">map_pairs2</span><span class="p" data-group-id="7664117604-11">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="7664117604-11">)</span><span class="p" data-group-id="7664117604-9">]</span><span class="p">.</span></code></pre><p>The compiler will generate code similar to this:</p><p><strong>DO NOT (already done by the compiler)</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">explicit_map_pairs</span><span class="p" data-group-id="9338495428-1">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs0</span><span class="p">,</span><span class="w"> </span><span class="n">Ys0</span><span class="p" data-group-id="9338495428-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">map_pairs2</span><span class="p" data-group-id="3237882446-6">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3237882446-7">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="3237882446-7">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3237882446-8">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="3237882446-8">]</span><span class="p" data-group-id="3237882446-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3237882446-9">[</span><span class="n">Map</span><span class="p" data-group-id="3237882446-10">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3237882446-10">)</span><span class="p">|</span><span class="nf">map_pairs2</span><span class="p" data-group-id="3237882446-11">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="3237882446-11">)</span><span class="p" data-group-id="3237882446-9">]</span><span class="p">.</span></code></pre><p>The compiler will generate code similar to this:</p><p><strong>DO NOT (already done by the compiler)</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">explicit_map_pairs</span><span class="p" data-group-id="1792275293-1">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs0</span><span class="p">,</span><span class="w"> </span><span class="n">Ys0</span><span class="p" data-group-id="1792275293-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Xs0</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="9338495428-2">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="9338495428-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="1792275293-2">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="1792275293-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  	    </span><span class="k">case</span><span class="w"> </span><span class="n">Ys0</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="9338495428-3">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="9338495428-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="p" data-group-id="9338495428-4">[</span><span class="n">Map</span><span class="p" data-group-id="9338495428-5">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9338495428-5">)</span><span class="p">|</span><span class="nf">explicit_map_pairs</span><span class="p" data-group-id="9338495428-6">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="9338495428-6">)</span><span class="p" data-group-id="9338495428-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="9338495428-7">[</span><span class="p" data-group-id="9338495428-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="1792275293-3">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="1792275293-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="p" data-group-id="1792275293-4">[</span><span class="n">Map</span><span class="p" data-group-id="1792275293-5">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1792275293-5">)</span><span class="p">|</span><span class="nf">explicit_map_pairs</span><span class="p" data-group-id="1792275293-6">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="1792275293-6">)</span><span class="p" data-group-id="1792275293-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="1792275293-7">[</span><span class="p" data-group-id="1792275293-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  		    </span><span class="n">Xs0</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="9338495428-8">[</span><span class="p" data-group-id="9338495428-8">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="1792275293-8">[</span><span class="p" data-group-id="1792275293-8">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  	    </span><span class="n">Ys0</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>This is slightly faster for probably the most common case that the input lists
│ │ │ │  are not empty or very short. (Another advantage is that Dialyzer can deduce a
│ │ │ │  better type for the <code class="inline">Xs</code> variable.)</p><h2 id="function-calls" class="section-heading">
│ │ │ │    <a href="#function-calls" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ ├── OEBPS/drivers.xhtml
│ │ │ │ @@ -27,23 +27,23 @@
│ │ │ │    <span class="text">Drivers and Concurrency</span>
│ │ │ │  </h2>
│ │ │ │  <p>The runtime system always takes a lock before running any code in a driver.</p><p>By default, that lock is at the driver level, that is, if several ports have
│ │ │ │  been opened to the same driver, only code for one port can be running
│ │ │ │  at the same time.</p><p>A driver can be configured to have one lock for each port instead.</p><p>If a driver is used in a functional way (that is, holds no state, but only does
│ │ │ │  some heavy calculation and returns a result), several ports with registered
│ │ │ │  names can be opened beforehand, and the port to be used can be chosen based on
│ │ │ │ -the scheduler ID as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2657217213-1">(</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="2657217213-2">(</span><span class="p" data-group-id="2657217213-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="2657217213-3">{</span><span class="ss">some_driver_01</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_02</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_03</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_04</span><span class="p">,</span><span class="w">
│ │ │ │ +the scheduler ID as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6216309076-1">(</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="6216309076-2">(</span><span class="p" data-group-id="6216309076-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="6216309076-3">{</span><span class="ss">some_driver_01</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_02</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_03</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_04</span><span class="p">,</span><span class="w">
│ │ │ │  	 </span><span class="ss">some_driver_05</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_06</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_07</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_08</span><span class="p">,</span><span class="w">
│ │ │ │  	 </span><span class="ss">some_driver_09</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_10</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_11</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_12</span><span class="p">,</span><span class="w">
│ │ │ │ -	 </span><span class="ss">some_driver_13</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_14</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_15</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_16</span><span class="p" data-group-id="2657217213-3">}</span><span class="p" data-group-id="2657217213-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +	 </span><span class="ss">some_driver_13</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_14</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_15</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_16</span><span class="p" data-group-id="6216309076-3">}</span><span class="p" data-group-id="6216309076-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">client_port</span><span class="p" data-group-id="2657217213-4">(</span><span class="p" data-group-id="2657217213-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">element</span><span class="p" data-group-id="2657217213-5">(</span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="2657217213-6">(</span><span class="ss">scheduler_id</span><span class="p" data-group-id="2657217213-6">)</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="nf">tuple_size</span><span class="p" data-group-id="2657217213-7">(</span><span class="o">?</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="2657217213-8">(</span><span class="p" data-group-id="2657217213-8">)</span><span class="p" data-group-id="2657217213-7">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w">
│ │ │ │ -	    </span><span class="o">?</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="2657217213-9">(</span><span class="p" data-group-id="2657217213-9">)</span><span class="p" data-group-id="2657217213-5">)</span><span class="p">.</span></code></pre><p>As long as there are no more than 16 schedulers, there will never be any lock
│ │ │ │ +</span><span class="nf">client_port</span><span class="p" data-group-id="6216309076-4">(</span><span class="p" data-group-id="6216309076-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">element</span><span class="p" data-group-id="6216309076-5">(</span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="6216309076-6">(</span><span class="ss">scheduler_id</span><span class="p" data-group-id="6216309076-6">)</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="nf">tuple_size</span><span class="p" data-group-id="6216309076-7">(</span><span class="o">?</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="6216309076-8">(</span><span class="p" data-group-id="6216309076-8">)</span><span class="p" data-group-id="6216309076-7">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w">
│ │ │ │ +	    </span><span class="o">?</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="6216309076-9">(</span><span class="p" data-group-id="6216309076-9">)</span><span class="p" data-group-id="6216309076-5">)</span><span class="p">.</span></code></pre><p>As long as there are no more than 16 schedulers, there will never be any lock
│ │ │ │  contention on the port lock for the driver.</p><h2 id="avoiding-copying-binaries-when-calling-a-driver" class="section-heading">
│ │ │ │    <a href="#avoiding-copying-binaries-when-calling-a-driver" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Avoiding Copying Binaries When Calling a Driver</span>
│ │ │ │  </h2>
│ │ │ │  <p>There are basically two ways to avoid copying a binary that is sent to a driver:</p><ul><li><p>If the <code class="inline">Data</code> argument for <a href="../../../lib/../erts/doc/html/erlang.html#port_control/3"><code class="inline">port_control/3</code></a> is a
│ │ │ ├── OEBPS/documentation.xhtml
│ │ │ │ @@ -17,23 +17,23 @@
│ │ │ │    </head>
│ │ │ │    <body class="content-inner">
│ │ │ │  
│ │ │ │      <h1 id="content">
│ │ │ │  Documentation
│ │ │ │      </h1>
│ │ │ │  <p>Documentation in Erlang is done through the <code class="inline">-moduledoc</code> and <code class="inline">-doc</code>
│ │ │ │ -<a href="modules.xhtml#module-attributes">attributes</a>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4279099336-1">(</span><span class="ss">arith</span><span class="p" data-group-id="4279099336-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<a href="modules.xhtml#module-attributes">attributes</a>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8616111284-1">(</span><span class="ss">arith</span><span class="p" data-group-id="8616111284-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │ │  A module for basic arithmetic.
│ │ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4279099336-2">(</span><span class="p" data-group-id="4279099336-3">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4279099336-3">]</span><span class="p" data-group-id="4279099336-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8616111284-2">(</span><span class="p" data-group-id="8616111284-3">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8616111284-3">]</span><span class="p" data-group-id="8616111284-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;Adds two numbers.&quot;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="4279099336-4">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="4279099336-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>The <code class="inline">-moduledoc</code> attribute has to be located before the first <code class="inline">-doc</code> attribute
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="8616111284-4">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="8616111284-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>The <code class="inline">-moduledoc</code> attribute has to be located before the first <code class="inline">-doc</code> attribute
│ │ │ │  or function declaration. It documents the overall purpose of the module.</p><p>The <code class="inline">-doc</code> attribute always precedes the <a href="ref_man_functions.xhtml">function</a> or
│ │ │ │  <a href="modules.xhtml#module-attributes">attribute</a> it documents. The
│ │ │ │  attributes that can be documented are
│ │ │ │  <a href="typespec.xhtml#type-declarations-of-user-defined-types">user-defined types</a>
│ │ │ │  (<code class="inline">-type</code> and <code class="inline">-opaque</code>) and
│ │ │ │  <a href="modules.xhtml#behaviour-module-attribute">behaviour module attributes</a>
│ │ │ │  (<code class="inline">-callback</code>).</p><p>By default, the format used for documentation attributes is
│ │ │ │ @@ -45,55 +45,55 @@
│ │ │ │  <a href="modules.xhtml#documentation-attributes">Documentation Attributes</a>.</p><p><code class="inline">-doc</code> attributes have been available since Erlang/OTP 27.</p><h2 id="documentation-metadata" class="section-heading">
│ │ │ │    <a href="#documentation-metadata" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Documentation metadata</span>
│ │ │ │  </h2>
│ │ │ │  <p>It is possible to add metadata to the documentation entry. You do this by adding
│ │ │ │ -a <code class="inline">-moduledoc</code> or <code class="inline">-doc</code> attribute with a map as argument. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5414433015-1">(</span><span class="ss">arith</span><span class="p" data-group-id="5414433015-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +a <code class="inline">-moduledoc</code> or <code class="inline">-doc</code> attribute with a map as argument. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0721434647-1">(</span><span class="ss">arith</span><span class="p" data-group-id="0721434647-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │ │  A module for basic arithmetic.
│ │ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="5414433015-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="5414433015-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="0721434647-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="0721434647-2">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5414433015-3">(</span><span class="p" data-group-id="5414433015-4">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5414433015-4">]</span><span class="p" data-group-id="5414433015-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0721434647-3">(</span><span class="p" data-group-id="0721434647-4">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0721434647-4">]</span><span class="p" data-group-id="0721434647-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;Adds two numbers.&quot;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="5414433015-5">(</span><span class="p" data-group-id="5414433015-6">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="5414433015-6">}</span><span class="p" data-group-id="5414433015-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="5414433015-7">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="5414433015-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>The metadata is used by documentation tools to provide extra information to the
│ │ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="0721434647-5">(</span><span class="p" data-group-id="0721434647-6">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="0721434647-6">}</span><span class="p" data-group-id="0721434647-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="0721434647-7">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="0721434647-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>The metadata is used by documentation tools to provide extra information to the
│ │ │ │  user. There can be multiple metadata documentation entries, in which case the
│ │ │ │  maps will be merged with the latest taking precedence if there are duplicate
│ │ │ │  keys. Example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;Adds two numbers.&quot;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="4574088350-1">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">author</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p" data-group-id="4574088350-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="4574088350-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="4574088350-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="4574088350-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="4574088350-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>This will result in a metadata entry of <code class="inline">#{since =&gt; &quot;2.0&quot;, author =&gt; &quot;Joe&quot;}</code>.</p><p>The keys and values in the metadata map can be any type, but it is recommended
│ │ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="1143954344-1">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">author</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p" data-group-id="1143954344-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="1143954344-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="1143954344-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="1143954344-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="1143954344-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>This will result in a metadata entry of <code class="inline">#{since =&gt; &quot;2.0&quot;, author =&gt; &quot;Joe&quot;}</code>.</p><p>The keys and values in the metadata map can be any type, but it is recommended
│ │ │ │  that only <a href="data_types.xhtml#atom">atoms</a> are used for keys and
│ │ │ │  <a href="data_types.xhtml#string">strings</a> for the values.</p><h2 id="external-documentation-files" class="section-heading">
│ │ │ │    <a href="#external-documentation-files" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">External documentation files</span>
│ │ │ │  </h2>
│ │ │ │  <p>The <code class="inline">-moduledoc</code> and <code class="inline">-doc</code> attributes can also be placed in external files. To do so, use
│ │ │ │  <code class="inline">-doc {file, &quot;path/to/doc.md&quot;}</code> to point to the documentation. The path used is
│ │ │ │  relative to the file where the <code class="inline">-doc</code> attribute is located. For example:</p><pre><code class="markdown">%% doc/add.md
│ │ │ │  Adds two numbers.</code></pre><p>and</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% src/arith.erl</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="5437707573-1">(</span><span class="p" data-group-id="5437707573-2">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;../doc/add.md&quot;</span><span class="p" data-group-id="5437707573-2">}</span><span class="p" data-group-id="5437707573-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="5437707573-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="5437707573-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><h2 id="documenting-a-module" class="section-heading">
│ │ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="5592583644-1">(</span><span class="p" data-group-id="5592583644-2">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;../doc/add.md&quot;</span><span class="p" data-group-id="5592583644-2">}</span><span class="p" data-group-id="5592583644-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="5592583644-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="5592583644-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><h2 id="documenting-a-module" class="section-heading">
│ │ │ │    <a href="#documenting-a-module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Documenting a module</span>
│ │ │ │  </h2>
│ │ │ │  <p>The module description should include details on how to use the API and examples
│ │ │ │  of the different functions working together. Here is a good place to use images
│ │ │ │  and other diagrams to better show the usage of the module. Instead of writing a
│ │ │ │  long text in the <code class="inline">-moduledoc</code> attribute, it could be better to break it out into
│ │ │ │  an external page.</p><p>The <code class="inline">-moduledoc</code> attribute should start with a short paragraph describing the
│ │ │ │ -module and then go into greater detail. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7779413301-1">(</span><span class="ss">arith</span><span class="p" data-group-id="7779413301-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +module and then go into greater detail. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7015644763-1">(</span><span class="ss">arith</span><span class="p" data-group-id="7015644763-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="s">&quot;
│ │ │ │     A module for basic arithmetic.
│ │ │ │  
│ │ │ │     This module can be used to add and subtract values. For example:
│ │ │ │  
│ │ │ │     ```erlang
│ │ │ │     1&gt; arith:subtract(arith:add(2, 3), 1).
│ │ │ │ @@ -108,96 +108,96 @@
│ │ │ │  <p>There are three reserved metadata keys for <code class="inline">-moduledoc</code>:</p><ul><li><code class="inline">since =&gt; unicode:chardata()</code> - Shows in which version of the application the module was added.
│ │ │ │  If this is added, all functions, types, and callbacks within will also receive
│ │ │ │  the same <code class="inline">since</code> value unless specified in the metadata of the function, type
│ │ │ │  or callback.</li><li><code class="inline">deprecated =&gt; unicode:chardata()</code> - Shows a text in the documentation explaining that it is
│ │ │ │  deprecated and what to use instead.</li><li><code class="inline">format =&gt; unicode:chardata()</code> - The format to use for all documentation in this module. The
│ │ │ │  default is <code class="inline">text/markdown</code>. It should be written using the
│ │ │ │  <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types">mime type</a>
│ │ │ │ -of the format.</li></ul><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="4433939441-1">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;../doc/arith.asciidoc&quot;</span><span class="p" data-group-id="4433939441-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="4433939441-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;0.1&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">format</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;text/asciidoc&quot;</span><span class="p" data-group-id="4433939441-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="4433939441-3">#{</span><span class="ss">deprecated</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;Use the Erlang arithmetic operators instead.&quot;</span><span class="p" data-group-id="4433939441-3">}</span><span class="p">.</span></code></pre><h2 id="documenting-functions-user-defined-types-and-callbacks" class="section-heading">
│ │ │ │ +of the format.</li></ul><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="9041169601-1">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;../doc/arith.asciidoc&quot;</span><span class="p" data-group-id="9041169601-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="9041169601-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;0.1&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">format</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;text/asciidoc&quot;</span><span class="p" data-group-id="9041169601-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="9041169601-3">#{</span><span class="ss">deprecated</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;Use the Erlang arithmetic operators instead.&quot;</span><span class="p" data-group-id="9041169601-3">}</span><span class="p">.</span></code></pre><h2 id="documenting-functions-user-defined-types-and-callbacks" class="section-heading">
│ │ │ │    <a href="#documenting-functions-user-defined-types-and-callbacks" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Documenting functions, user-defined types, and callbacks</span>
│ │ │ │  </h2>
│ │ │ │  <p>Functions, types, and callbacks can be documented using the <code class="inline">-doc</code> attribute.
│ │ │ │  Each entry should start with a short paragraph describing the purpose of the entity,
│ │ │ │  and then go into greater detail if needed.</p><p>It is not recommended to include images or diagrams in this documentation as it
│ │ │ │  is used by IDEs and <a href="../../../lib/stdlib/doc/html/c.html#h/1"><code class="inline">c:h/1</code></a> to show the documentation to the user.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │ │  A number that can be used by the arith module.
│ │ │ │  
│ │ │ │  We use a special number here so that we know
│ │ │ │  that this number comes from this module.
│ │ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="3396094162-1">(</span><span class="p" data-group-id="3396094162-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="3396094162-2">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">number</span><span class="p" data-group-id="3396094162-3">(</span><span class="p" data-group-id="3396094162-3">)</span><span class="p" data-group-id="3396094162-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="7720545107-1">(</span><span class="p" data-group-id="7720545107-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="7720545107-2">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">number</span><span class="p" data-group-id="7720545107-3">(</span><span class="p" data-group-id="7720545107-3">)</span><span class="p" data-group-id="7720545107-2">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │ │  Adds two numbers.
│ │ │ │  
│ │ │ │  ### Example:
│ │ │ │  
│ │ │ │  ```
│ │ │ │  1&gt; arith:add(arith:number(1), arith:number(2)). {arith, 3}
│ │ │ │  ```
│ │ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="3396094162-4">(</span><span class="nf">number</span><span class="p" data-group-id="3396094162-5">(</span><span class="p" data-group-id="3396094162-5">)</span><span class="p">,</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="3396094162-6">(</span><span class="p" data-group-id="3396094162-6">)</span><span class="p" data-group-id="3396094162-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="3396094162-7">(</span><span class="p" data-group-id="3396094162-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="3396094162-8">(</span><span class="p" data-group-id="3396094162-9">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="n">One</span><span class="p" data-group-id="3396094162-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3396094162-10">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="3396094162-10">}</span><span class="p" data-group-id="3396094162-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3396094162-11">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="3396094162-11">}</span><span class="p">.</span></code></pre><p>Examples in documentation can be tested using <a href="../../../lib/common_test/doc/html/ct_doctest.html"><code class="inline">ct_doctest</code></a>.</p><h3 id="doc-metadata" class="section-heading">
│ │ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="7720545107-4">(</span><span class="nf">number</span><span class="p" data-group-id="7720545107-5">(</span><span class="p" data-group-id="7720545107-5">)</span><span class="p">,</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="7720545107-6">(</span><span class="p" data-group-id="7720545107-6">)</span><span class="p" data-group-id="7720545107-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="7720545107-7">(</span><span class="p" data-group-id="7720545107-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="7720545107-8">(</span><span class="p" data-group-id="7720545107-9">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="n">One</span><span class="p" data-group-id="7720545107-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7720545107-10">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="7720545107-10">}</span><span class="p" data-group-id="7720545107-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7720545107-11">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="7720545107-11">}</span><span class="p">.</span></code></pre><p>Examples in documentation can be tested using <a href="../../../lib/common_test/doc/html/ct_doctest.html"><code class="inline">ct_doctest</code></a>.</p><h3 id="doc-metadata" class="section-heading">
│ │ │ │    <a href="#doc-metadata" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Doc metadata</span>
│ │ │ │  </h3>
│ │ │ │  <p>There are four reserved metadata keys for <code class="inline">-doc</code>:</p><ul><li><p><code class="inline">since =&gt; unicode:chardata()</code> - Shows in which version of the application the
│ │ │ │  function, type, or callback was added.</p></li><li><p><code class="inline">deprecated =&gt; unicode:chardata()</code> - Shows a text in the documentation
│ │ │ │  explaining that it is deprecated and what to use instead. The compiler will
│ │ │ │  automatically insert this key if there is a <code class="inline">-deprecated</code> attribute marking a
│ │ │ │  function as deprecated.</p></li><li><p><code class="inline">group =&gt; unicode:chardata()</code> - A group that the function, type, or callback belongs to.
│ │ │ │  It allows tooling, such as shell autocompletion and documentation generators, to list all
│ │ │ │  entries within the same group together, often using the group name as an indicator.</p></li><li><p><code class="inline">equiv =&gt; unicode:chardata() | F/A | F(...)</code> - Notes that this function is equivalent to
│ │ │ │  another function in this module. The equivalence can be described using either
│ │ │ │ -<code class="inline">Func/Arity</code>, <code class="inline">Func(Args)</code> or a <a href="../../../lib/stdlib/doc/html/unicode.html#t:chardata/0">unicode string</a>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="2595140639-1">#{</span><span class="ss">equiv</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">add</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="2595140639-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="2595140639-2">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="2595140639-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="2595140639-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2595140639-4">[</span><span class="p" data-group-id="2595140639-4">]</span><span class="p" data-group-id="2595140639-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="2595140639-5">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="2595140639-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>or</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="3983689770-1">#{</span><span class="ss">equiv</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="3983689770-2">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3983689770-3">[</span><span class="p" data-group-id="3983689770-3">]</span><span class="p" data-group-id="3983689770-2">)</span><span class="p" data-group-id="3983689770-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="3983689770-4">(</span><span class="n">One</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="3983689770-5">(</span><span class="p" data-group-id="3983689770-5">)</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="3983689770-6">(</span><span class="p" data-group-id="3983689770-6">)</span><span class="p" data-group-id="3983689770-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="3983689770-7">(</span><span class="p" data-group-id="3983689770-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="3983689770-8">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="3983689770-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="3983689770-9">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3983689770-10">[</span><span class="p" data-group-id="3983689770-10">]</span><span class="p" data-group-id="3983689770-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="3983689770-11">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="3983689770-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>The entry into the <a href="../../../lib/kernel/doc/html/eep48_chapter.xhtml">EEP-48</a> doc chunk metadata is
│ │ │ │ +<code class="inline">Func/Arity</code>, <code class="inline">Func(Args)</code> or a <a href="../../../lib/stdlib/doc/html/unicode.html#t:chardata/0">unicode string</a>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="2707729850-1">#{</span><span class="ss">equiv</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">add</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="2707729850-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="2707729850-2">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="2707729850-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="2707729850-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2707729850-4">[</span><span class="p" data-group-id="2707729850-4">]</span><span class="p" data-group-id="2707729850-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="2707729850-5">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="2707729850-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>or</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="2426004870-1">#{</span><span class="ss">equiv</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="2426004870-2">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2426004870-3">[</span><span class="p" data-group-id="2426004870-3">]</span><span class="p" data-group-id="2426004870-2">)</span><span class="p" data-group-id="2426004870-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="2426004870-4">(</span><span class="n">One</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="2426004870-5">(</span><span class="p" data-group-id="2426004870-5">)</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="2426004870-6">(</span><span class="p" data-group-id="2426004870-6">)</span><span class="p" data-group-id="2426004870-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="2426004870-7">(</span><span class="p" data-group-id="2426004870-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="2426004870-8">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="2426004870-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="2426004870-9">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2426004870-10">[</span><span class="p" data-group-id="2426004870-10">]</span><span class="p" data-group-id="2426004870-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="2426004870-11">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="2426004870-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>The entry into the <a href="../../../lib/kernel/doc/html/eep48_chapter.xhtml">EEP-48</a> doc chunk metadata is
│ │ │ │  the value converted to a string.</p></li><li><p><code class="inline">exported =&gt; boolean()</code> - A <a href="../../../lib/../erts/doc/html/erlang.html#t:boolean/0"><code class="inline">boolean/0</code></a> signifying if the entry is <code class="inline">exported</code>
│ │ │ │  or not. This value is automatically set by the compiler and should not be set
│ │ │ │  by the user.</p></li></ul><h3 id="doc-signatures" class="section-heading">
│ │ │ │    <a href="#doc-signatures" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Doc signatures</span>
│ │ │ │  </h3>
│ │ │ │  <p>The doc signature is a short text shown to describe the function and its arguments.
│ │ │ │  By default, it is determined by looking at the names of the arguments in the
│ │ │ │ -<code class="inline">-spec</code> or function. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add</span><span class="p" data-group-id="6767701657-1">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="6767701657-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">-spec</code> or function. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add</span><span class="p" data-group-id="9302457282-1">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="9302457282-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">sub</span><span class="p" data-group-id="6767701657-2">(</span><span class="n">One</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="6767701657-3">(</span><span class="p" data-group-id="6767701657-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="6767701657-4">(</span><span class="p" data-group-id="6767701657-4">)</span><span class="p" data-group-id="6767701657-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="6767701657-5">(</span><span class="p" data-group-id="6767701657-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">sub</span><span class="p" data-group-id="6767701657-6">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6767701657-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">Y</span><span class="p">.</span></code></pre><p>will have a signature of <code class="inline">add(One, Two)</code> and <code class="inline">sub(One, Two)</code>.</p><p>For types or callbacks, the signature is derived from the type or callback
│ │ │ │ -specification. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0250879186-1">(</span><span class="n">Value</span><span class="p" data-group-id="0250879186-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0250879186-2">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="0250879186-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">sub</span><span class="p" data-group-id="9302457282-2">(</span><span class="n">One</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="9302457282-3">(</span><span class="p" data-group-id="9302457282-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="9302457282-4">(</span><span class="p" data-group-id="9302457282-4">)</span><span class="p" data-group-id="9302457282-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="9302457282-5">(</span><span class="p" data-group-id="9302457282-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">sub</span><span class="p" data-group-id="9302457282-6">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9302457282-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">Y</span><span class="p">.</span></code></pre><p>will have a signature of <code class="inline">add(One, Two)</code> and <code class="inline">sub(One, Two)</code>.</p><p>For types or callbacks, the signature is derived from the type or callback
│ │ │ │ +specification. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9098425450-1">(</span><span class="n">Value</span><span class="p" data-group-id="9098425450-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="9098425450-2">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="9098425450-2">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% signature will be `number(Value)`</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0250879186-3">(</span><span class="p" data-group-id="0250879186-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0250879186-4">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0250879186-5">(</span><span class="p" data-group-id="0250879186-5">)</span><span class="p" data-group-id="0250879186-4">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9098425450-3">(</span><span class="p" data-group-id="9098425450-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="9098425450-4">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9098425450-5">(</span><span class="p" data-group-id="9098425450-5">)</span><span class="p" data-group-id="9098425450-4">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% signature will be `number()`</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">increment</span><span class="p" data-group-id="0250879186-6">(</span><span class="n">In</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0250879186-7">(</span><span class="p" data-group-id="0250879186-7">)</span><span class="p" data-group-id="0250879186-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Out</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">increment</span><span class="p" data-group-id="9098425450-6">(</span><span class="n">In</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9098425450-7">(</span><span class="p" data-group-id="9098425450-7">)</span><span class="p" data-group-id="9098425450-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Out</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% signature will be `increment(In)`</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">increment</span><span class="p" data-group-id="0250879186-8">(</span><span class="n">In</span><span class="p" data-group-id="0250879186-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Out</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">In</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0250879186-9">(</span><span class="p" data-group-id="0250879186-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">increment</span><span class="p" data-group-id="9098425450-8">(</span><span class="n">In</span><span class="p" data-group-id="9098425450-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Out</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">In</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9098425450-9">(</span><span class="p" data-group-id="9098425450-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% signature will be `increment(In)`</span></code></pre><p>If it is not possible to &quot;easily&quot; figure out a nice signature from the code, the
│ │ │ │  MFA syntax is used instead. For example: <code class="inline">add/2</code>, <code class="inline">number/1</code>, <code class="inline">increment/1</code>.</p><p>It is possible to supply a custom signature by placing it as the first line of the
│ │ │ │  <code class="inline">-doc</code> attribute. The provided signature must be in the form of a function
│ │ │ │  declaration up until the <code class="inline">-&gt;</code>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │ │  add(One, Two)
│ │ │ │  
│ │ │ │  Adds two numbers.
│ │ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="7475584750-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="7475584750-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p">.</span></code></pre><p>This will create the signature <code class="inline">add(One, Two)</code>. The signature will be removed from the
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="0536294252-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0536294252-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p">.</span></code></pre><p>This will create the signature <code class="inline">add(One, Two)</code>. The signature will be removed from the
│ │ │ │  documentation string, so in the example above only the text <code class="inline">&quot;Adds two numbers&quot;</code>
│ │ │ │  will be part of the documentation. This works for functions, types, and
│ │ │ │  callbacks.</p><h2 id="links-in-markdown" class="section-heading">
│ │ │ │    <a href="#links-in-markdown" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Links in Markdown</span>
│ │ │ │ @@ -235,28 +235,28 @@
│ │ │ │  modules. That is, modules that should be used by other applications and modules
│ │ │ │  that should not. By default, all modules in an application are visible, but by
│ │ │ │  setting <code class="inline">-moduledoc false.</code>, specific modules can be hidden from being listed as
│ │ │ │  part of the available API.</p><p>An Erlang <a href="modules.xhtml">module</a> consists of public and private functions and type
│ │ │ │  attributes. By default, all exported functions, exported types and callbacks are
│ │ │ │  considered visible and part of the module's public API. In addition, any
│ │ │ │  non-exported type that is referred to by any other visible type attribute is
│ │ │ │ -also visible, but not considered to be part of the public API. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8553019925-1">(</span><span class="p" data-group-id="8553019925-2">[</span><span class="ss">example</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8553019925-2">]</span><span class="p" data-group-id="8553019925-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +also visible, but not considered to be part of the public API. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1340456173-1">(</span><span class="p" data-group-id="1340456173-2">[</span><span class="ss">example</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1340456173-2">]</span><span class="p" data-group-id="1340456173-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="8553019925-3">(</span><span class="p" data-group-id="8553019925-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">example</span><span class="p" data-group-id="8553019925-4">(</span><span class="p" data-group-id="8553019925-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="8553019925-5">(</span><span class="p" data-group-id="8553019925-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">example</span><span class="p" data-group-id="8553019925-6">(</span><span class="p" data-group-id="8553019925-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span></code></pre><p>In the code above, the function <code class="inline">example/0</code> is exported and references the
│ │ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="1340456173-3">(</span><span class="p" data-group-id="1340456173-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">example</span><span class="p" data-group-id="1340456173-4">(</span><span class="p" data-group-id="1340456173-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="1340456173-5">(</span><span class="p" data-group-id="1340456173-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">example</span><span class="p" data-group-id="1340456173-6">(</span><span class="p" data-group-id="1340456173-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span></code></pre><p>In the code above, the function <code class="inline">example/0</code> is exported and references the
│ │ │ │  unexported type <code class="inline">private/0</code>. Therefore both <code class="inline">example/0</code> and <code class="inline">private/0</code> will be
│ │ │ │  marked as visible. The <code class="inline">private/0</code> type will have the metadata field <code class="inline">exported</code>
│ │ │ │  set to <code class="inline">false</code> to show that it is not part of the public API.</p><p>If you want to make a visible entity hidden, you need to set the <code class="inline">-doc</code> attribute
│ │ │ │ -to <code class="inline">false</code>. Let us revisit our previous example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2353007029-1">(</span><span class="p" data-group-id="2353007029-2">[</span><span class="ss">example</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2353007029-2">]</span><span class="p" data-group-id="2353007029-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +to <code class="inline">false</code>. Let us revisit our previous example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1523389887-1">(</span><span class="p" data-group-id="1523389887-2">[</span><span class="ss">example</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1523389887-2">]</span><span class="p" data-group-id="1523389887-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="2353007029-3">(</span><span class="p" data-group-id="2353007029-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">example</span><span class="p" data-group-id="2353007029-4">(</span><span class="p" data-group-id="2353007029-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="2353007029-5">(</span><span class="p" data-group-id="2353007029-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="1523389887-3">(</span><span class="p" data-group-id="1523389887-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">example</span><span class="p" data-group-id="1523389887-4">(</span><span class="p" data-group-id="1523389887-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="1523389887-5">(</span><span class="p" data-group-id="1523389887-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="ss">false</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">example</span><span class="p" data-group-id="2353007029-6">(</span><span class="p" data-group-id="2353007029-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span></code></pre><p>The function <code class="inline">example/0</code> is exported but explicitly marked as hidden; therefore
│ │ │ │ +</span><span class="nf">example</span><span class="p" data-group-id="1523389887-6">(</span><span class="p" data-group-id="1523389887-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span></code></pre><p>The function <code class="inline">example/0</code> is exported but explicitly marked as hidden; therefore
│ │ │ │  both <code class="inline">example/0</code> and <code class="inline">private/0</code> will be hidden.</p><p>Any documentation added to an automatically hidden entity (non-exported function
│ │ │ │  or type) is ignored and will generate a warning. Such functions can be
│ │ │ │  documented using comments.</p><h2 id="compiling-and-getting-documentation" class="section-heading">
│ │ │ │    <a href="#compiling-and-getting-documentation" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Compiling and getting documentation</span>
│ │ │ │ @@ -282,21 +282,21 @@
│ │ │ │    <span class="text">Using ExDoc to generate HTML/ePub documentation</span>
│ │ │ │  </h2>
│ │ │ │  <p><a href="https://hexdocs.pm/ex_doc/">ExDoc</a> has built-in support to generate
│ │ │ │  documentation from Markdown. The simplest way is by using the
│ │ │ │  <a href="https://hexdocs.pm/rebar3_ex_doc">rebar3_ex_doc</a> plugin. To set up a
│ │ │ │  rebar3 project to use <a href="https://hexdocs.pm/ex_doc/">ExDoc</a> to generate
│ │ │ │  documentation, add the following to your <code class="inline">rebar3.config</code>.</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% Enable the plugin</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6098065048-1">{</span><span class="ss">plugins</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6098065048-2">[</span><span class="ss">rebar3_ex_doc</span><span class="p" data-group-id="6098065048-2">]</span><span class="p" data-group-id="6098065048-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7417962766-1">{</span><span class="ss">plugins</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7417962766-2">[</span><span class="ss">rebar3_ex_doc</span><span class="p" data-group-id="7417962766-2">]</span><span class="p" data-group-id="7417962766-1">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="p" data-group-id="6098065048-3">{</span><span class="ss">ex_doc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6098065048-4">[</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6098065048-5">{</span><span class="ss">extras</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6098065048-6">[</span><span class="s">&quot;README.md&quot;</span><span class="p" data-group-id="6098065048-6">]</span><span class="p" data-group-id="6098065048-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6098065048-7">{</span><span class="ss">main</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;README.md&quot;</span><span class="p" data-group-id="6098065048-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6098065048-8">{</span><span class="ss">source_url</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;https://github.com/namespace/your_app&quot;</span><span class="p" data-group-id="6098065048-8">}</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6098065048-4">]</span><span class="p" data-group-id="6098065048-3">}</span><span class="p">.</span></code></pre><p>When configured, you can run <code class="inline">rebar3 ex_doc</code> to generate the
│ │ │ │ +</span><span class="p" data-group-id="7417962766-3">{</span><span class="ss">ex_doc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7417962766-4">[</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="7417962766-5">{</span><span class="ss">extras</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7417962766-6">[</span><span class="s">&quot;README.md&quot;</span><span class="p" data-group-id="7417962766-6">]</span><span class="p" data-group-id="7417962766-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="7417962766-7">{</span><span class="ss">main</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;README.md&quot;</span><span class="p" data-group-id="7417962766-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="7417962766-8">{</span><span class="ss">source_url</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;https://github.com/namespace/your_app&quot;</span><span class="p" data-group-id="7417962766-8">}</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7417962766-4">]</span><span class="p" data-group-id="7417962766-3">}</span><span class="p">.</span></code></pre><p>When configured, you can run <code class="inline">rebar3 ex_doc</code> to generate the
│ │ │ │  documentation to <code class="inline">doc/index.html</code>. For more details and options, see
│ │ │ │  the <a href="https://hexdocs.pm/rebar3_ex_doc">rebar3_ex_doc</a> documentation.</p><p>You can also download the
│ │ │ │  <a href="https://github.com/elixir/ex_doc/releases/latest">release escript bundle</a> from
│ │ │ │  GitHub and run it from the command line. The documentation for using the escript
│ │ │ │  is found by running <code class="inline">ex_doc --help</code>.</p><p>If you are writing documentation that will be using
│ │ │ │  <a href="https://hexdocs.pm/ex_doc/">ExDoc</a> to generate HTML/ePub, it is highly
│ │ │ │  recommended to read its documentation.</p>
│ │ │ ├── OEBPS/distributed_applications.xhtml
│ │ │ │ @@ -55,36 +55,36 @@
│ │ │ │  (within the time-out specified by <code class="inline">sync_nodes_timeout</code>).</li><li><p><code class="inline">sync_nodes_timeout = integer() | infinity</code> - Specifies how many milliseconds
│ │ │ │  to wait for the other nodes to start.</p></li></ul><p>When started, the node waits for all nodes specified by <code class="inline">sync_nodes_mandatory</code>
│ │ │ │  and <code class="inline">sync_nodes_optional</code> to come up. When all nodes are up, or when all
│ │ │ │  mandatory nodes are up and the time specified by <code class="inline">sync_nodes_timeout</code> has
│ │ │ │  elapsed, all applications start. If not all mandatory nodes are up, the node
│ │ │ │  terminates.</p><p><em>Example:</em></p><p>An application <code class="inline">myapp</code> is to run at the node <code class="inline">cp1@cave</code>. If this node goes down,
│ │ │ │  <code class="inline">myapp</code> is to be restarted at <code class="inline">cp2@cave</code> or <code class="inline">cp3@cave</code>. A system configuration
│ │ │ │ -file <code class="inline">cp1.config</code> for <code class="inline">cp1@cave</code> can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9512478463-1">[</span><span class="p" data-group-id="9512478463-2">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="9512478463-3">[</span><span class="p" data-group-id="9512478463-4">{</span><span class="ss">distributed</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9512478463-5">[</span><span class="p" data-group-id="9512478463-6">{</span><span class="ss">myapp</span><span class="p">,</span><span class="w"> </span><span class="mi">5000</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9512478463-7">[</span><span class="ss">cp1@cave</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9512478463-8">{</span><span class="ss">cp2@cave</span><span class="p">,</span><span class="w"> </span><span class="ss">cp3@cave</span><span class="p" data-group-id="9512478463-8">}</span><span class="p" data-group-id="9512478463-7">]</span><span class="p" data-group-id="9512478463-6">}</span><span class="p" data-group-id="9512478463-5">]</span><span class="p" data-group-id="9512478463-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="9512478463-9">{</span><span class="ss">sync_nodes_mandatory</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9512478463-10">[</span><span class="ss">cp2@cave</span><span class="p">,</span><span class="w"> </span><span class="ss">cp3@cave</span><span class="p" data-group-id="9512478463-10">]</span><span class="p" data-group-id="9512478463-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="9512478463-11">{</span><span class="ss">sync_nodes_timeout</span><span class="p">,</span><span class="w"> </span><span class="mi">5000</span><span class="p" data-group-id="9512478463-11">}</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="9512478463-3">]</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9512478463-2">}</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9512478463-1">]</span><span class="p">.</span></code></pre><p>The system configuration files for <code class="inline">cp2@cave</code> and <code class="inline">cp3@cave</code> are identical,
│ │ │ │ +file <code class="inline">cp1.config</code> for <code class="inline">cp1@cave</code> can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5292882265-1">[</span><span class="p" data-group-id="5292882265-2">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="5292882265-3">[</span><span class="p" data-group-id="5292882265-4">{</span><span class="ss">distributed</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5292882265-5">[</span><span class="p" data-group-id="5292882265-6">{</span><span class="ss">myapp</span><span class="p">,</span><span class="w"> </span><span class="mi">5000</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5292882265-7">[</span><span class="ss">cp1@cave</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5292882265-8">{</span><span class="ss">cp2@cave</span><span class="p">,</span><span class="w"> </span><span class="ss">cp3@cave</span><span class="p" data-group-id="5292882265-8">}</span><span class="p" data-group-id="5292882265-7">]</span><span class="p" data-group-id="5292882265-6">}</span><span class="p" data-group-id="5292882265-5">]</span><span class="p" data-group-id="5292882265-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="5292882265-9">{</span><span class="ss">sync_nodes_mandatory</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5292882265-10">[</span><span class="ss">cp2@cave</span><span class="p">,</span><span class="w"> </span><span class="ss">cp3@cave</span><span class="p" data-group-id="5292882265-10">]</span><span class="p" data-group-id="5292882265-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="5292882265-11">{</span><span class="ss">sync_nodes_timeout</span><span class="p">,</span><span class="w"> </span><span class="mi">5000</span><span class="p" data-group-id="5292882265-11">}</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="5292882265-3">]</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5292882265-2">}</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5292882265-1">]</span><span class="p">.</span></code></pre><p>The system configuration files for <code class="inline">cp2@cave</code> and <code class="inline">cp3@cave</code> are identical,
│ │ │ │  except for the list of mandatory nodes, which is to be <code class="inline">[cp1@cave, cp3@cave]</code>
│ │ │ │  for <code class="inline">cp2@cave</code> and <code class="inline">[cp1@cave, cp2@cave]</code> for <code class="inline">cp3@cave</code>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>All involved nodes must have the same value for <code class="inline">distributed</code> and
│ │ │ │  <code class="inline">sync_nodes_timeout</code>. Otherwise the system behavior is undefined.</p></section><h2 id="starting-and-stopping-distributed-applications" class="section-heading">
│ │ │ │    <a href="#starting-and-stopping-distributed-applications" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Starting and Stopping Distributed Applications</span>
│ │ │ │  </h2>
│ │ │ │  <p>When all involved (mandatory) nodes have been started, the distributed
│ │ │ │  application can be started by calling <code class="inline">application:start(Application)</code> at <em>all
│ │ │ │  of these nodes.</em></p><p>A boot script (see <a href="release_structure.xhtml">Releases</a>) can be used that
│ │ │ │  automatically starts the application.</p><p>The application is started at the first operational node that is listed in the
│ │ │ │  list of nodes in the <code class="inline">distributed</code> configuration parameter. The application is
│ │ │ │  started as usual. That is, an application master is created and calls the
│ │ │ │ -application callback function:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="5365765278-1">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="5365765278-1">)</span></code></pre><p>Example:</p><p>Continuing the example from the previous section, the three nodes are started,
│ │ │ │ +application callback function:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="6455411701-1">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="6455411701-1">)</span></code></pre><p>Example:</p><p>Continuing the example from the previous section, the three nodes are started,
│ │ │ │  specifying the system configuration file:</p><pre><code class="text">&gt; erl -sname cp1 -config cp1
│ │ │ │  &gt; erl -sname cp2 -config cp2
│ │ │ │  &gt; erl -sname cp3 -config cp3</code></pre><p>When all nodes are operational, <code class="inline">myapp</code> can be started. This is achieved by
│ │ │ │  calling <code class="inline">application:start(myapp)</code> at all three nodes. It is then started at
│ │ │ │  <code class="inline">cp1</code>, as shown in the following figure:</p><p><a href="" id="dist1"></a></p><p><img src="assets/dist1.gif" alt="Application myapp - Situation 1" title="Application myapp - Situation 1"/></p><p>Similarly, the application must be stopped by calling
│ │ │ │  <code class="inline">application:stop(Application)</code> at all involved nodes.</p><h2 id="failover" class="section-heading">
│ │ │ │    <a href="#failover" class="hover-link">
│ │ │ │ @@ -92,30 +92,30 @@
│ │ │ │    </a>
│ │ │ │    <span class="text">Failover</span>
│ │ │ │  </h2>
│ │ │ │  <p>If the node where the application is running goes down, the application is
│ │ │ │  restarted (after the specified time-out) at the first operational node that is
│ │ │ │  listed in the list of nodes in the <code class="inline">distributed</code> configuration parameter. This
│ │ │ │  is called a <em>failover</em>.</p><p>The application is started the normal way at the new node, that is, by the
│ │ │ │ -application master calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="4204425771-1">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="4204425771-1">)</span></code></pre><p>An exception is if the application has the <code class="inline">start_phases</code> key defined (see
│ │ │ │ +application master calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="0615306163-1">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="0615306163-1">)</span></code></pre><p>An exception is if the application has the <code class="inline">start_phases</code> key defined (see
│ │ │ │  <a href="included_applications.xhtml">Included Applications</a>). The application is then
│ │ │ │ -instead started by calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="7002316872-1">(</span><span class="p" data-group-id="7002316872-2">{</span><span class="ss">failover</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="7002316872-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="7002316872-1">)</span></code></pre><p>Here <code class="inline">Node</code> is the terminated node.</p><p><em>Example:</em></p><p>If <code class="inline">cp1</code> goes down, the system checks which one of the other nodes, <code class="inline">cp2</code> or
│ │ │ │ +instead started by calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="5363385252-1">(</span><span class="p" data-group-id="5363385252-2">{</span><span class="ss">failover</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="5363385252-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="5363385252-1">)</span></code></pre><p>Here <code class="inline">Node</code> is the terminated node.</p><p><em>Example:</em></p><p>If <code class="inline">cp1</code> goes down, the system checks which one of the other nodes, <code class="inline">cp2</code> or
│ │ │ │  <code class="inline">cp3</code>, has the least number of running applications, but waits for 5 seconds for
│ │ │ │  <code class="inline">cp1</code> to restart. If <code class="inline">cp1</code> does not restart and <code class="inline">cp2</code> runs fewer applications
│ │ │ │  than <code class="inline">cp3</code>, <code class="inline">myapp</code> is restarted on <code class="inline">cp2</code>.</p><p><a href="" id="dist2"></a></p><p><img src="assets/dist2.gif" alt="Application myapp - Situation 2" title="Application myapp - Situation 2"/></p><p>Suppose now that <code class="inline">cp2</code> goes also down and does not restart within 5 seconds.
│ │ │ │  <code class="inline">myapp</code> is now restarted on <code class="inline">cp3</code>.</p><p><a href="" id="dist3"></a></p><p><img src="assets/dist3.gif" alt="Application myapp - Situation 3" title="Application myapp - Situation 3"/></p><h2 id="takeover" class="section-heading">
│ │ │ │    <a href="#takeover" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Takeover</span>
│ │ │ │  </h2>
│ │ │ │  <p>If a node is started, which has higher priority according to <code class="inline">distributed</code> than
│ │ │ │  the node where a distributed application is running, the application is
│ │ │ │  restarted at the new node and stopped at the old node. This is called a
│ │ │ │ -<em>takeover</em>.</p><p>The application is started by the application master calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="9941704248-1">(</span><span class="p" data-group-id="9941704248-2">{</span><span class="ss">takeover</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="9941704248-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="9941704248-1">)</span></code></pre><p>Here <code class="inline">Node</code> is the old node.</p><p><em>Example:</em></p><p>If <code class="inline">myapp</code> is running at <code class="inline">cp3</code>, and if <code class="inline">cp2</code> now restarts, it does not restart
│ │ │ │ +<em>takeover</em>.</p><p>The application is started by the application master calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2627478310-1">(</span><span class="p" data-group-id="2627478310-2">{</span><span class="ss">takeover</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="2627478310-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="2627478310-1">)</span></code></pre><p>Here <code class="inline">Node</code> is the old node.</p><p><em>Example:</em></p><p>If <code class="inline">myapp</code> is running at <code class="inline">cp3</code>, and if <code class="inline">cp2</code> now restarts, it does not restart
│ │ │ │  <code class="inline">myapp</code>, as the order between the <code class="inline">cp2</code> and <code class="inline">cp3</code> nodes is undefined.</p><p><a href="" id="dist4"></a></p><p><img src="assets/dist4.gif" alt="Application myapp - Situation 4" title="Application myapp - Situation 4"/></p><p>However, if <code class="inline">cp1</code> also restarts, the function <a href="../../../lib/kernel/doc/html/application.html#takeover/2"><code class="inline">application:takeover/2</code></a> moves
│ │ │ │  <code class="inline">myapp</code> to <code class="inline">cp1</code>, as <code class="inline">cp1</code> has a higher priority than <code class="inline">cp3</code> for this
│ │ │ │  application. In this case, <code class="inline">Module:start({takeover, cp3@cave}, StartArgs)</code> is
│ │ │ │  executed at <code class="inline">cp1</code> to start the application.</p><p><a href="" id="dist5"></a></p><p><img src="assets/dist5.gif" alt="Application myapp - Situation 5" title="Application myapp - Situation 5"/></p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/distributed.xhtml
│ │ │ │ @@ -48,25 +48,25 @@
│ │ │ │  <p>A <em>node</em> is an executing Erlang runtime system that has been given a name, using
│ │ │ │  the command-line flag <a href="../../../lib/../erts/doc/html/erl_cmd.xhtml#name"><code class="inline">-name</code></a> (long names) or
│ │ │ │  <a href="../../../lib/../erts/doc/html/erl_cmd.xhtml#sname"><code class="inline">-sname</code></a> (short names).</p><p>The format of the node name is an atom <code class="inline">name@host</code>. <code class="inline">name</code> is the name given by
│ │ │ │  the user, and consists of alphanumerics, <code class="inline">-</code>, <code class="inline">_</code>, and <code class="inline">\</code>.
│ │ │ │  <code class="inline">host</code> is the full host name if long names are used, or the first part
│ │ │ │  of the host name if short names are used. Function <a href="../../../lib/../erts/doc/html/erlang.html#node/0"><code class="inline">node()</code></a>
│ │ │ │  returns the name of the node.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -name dilbert</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5015751045-1">(</span><span class="ss">dilbert@uab</span><span class="p">.</span><span class="ss">ericsson</span><span class="p">.</span><span class="ss">se</span><span class="p" data-group-id="5015751045-1">)</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">node</span><span class="p" data-group-id="5015751045-2">(</span><span class="p" data-group-id="5015751045-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3670261832-1">(</span><span class="ss">dilbert@uab</span><span class="p">.</span><span class="ss">ericsson</span><span class="p">.</span><span class="ss">se</span><span class="p" data-group-id="3670261832-1">)</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">node</span><span class="p" data-group-id="3670261832-2">(</span><span class="p" data-group-id="3670261832-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">&#39;dilbert@uab.ericsson.se&#39;</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">% erl -sname dilbert</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">(dilbert@uab)1&gt; </span><span class="nf">node</span><span class="p" data-group-id="5015751045-3">(</span><span class="p" data-group-id="5015751045-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">(dilbert@uab)1&gt; </span><span class="nf">node</span><span class="p" data-group-id="3670261832-3">(</span><span class="p" data-group-id="3670261832-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">dilbert@uab</span></code></pre><p>The node name can also be given at runtime by calling <a href="../../../lib/kernel/doc/html/net_kernel.html#start/1"><code class="inline">net_kernel:start/1</code></a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nf">node</span><span class="p" data-group-id="8887223348-1">(</span><span class="p" data-group-id="8887223348-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nf">node</span><span class="p" data-group-id="6360522870-1">(</span><span class="p" data-group-id="6360522870-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">nonode@nohost</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">net_kernel</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8887223348-2">(</span><span class="p" data-group-id="8887223348-3">[</span><span class="ss">dilbert</span><span class="p">,</span><span class="ss">shortnames</span><span class="p" data-group-id="8887223348-3">]</span><span class="p" data-group-id="8887223348-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8887223348-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.102</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="8887223348-4">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">(dilbert@uab)3&gt; </span><span class="nf">node</span><span class="p" data-group-id="8887223348-5">(</span><span class="p" data-group-id="8887223348-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">net_kernel</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="6360522870-2">(</span><span class="p" data-group-id="6360522870-3">[</span><span class="ss">dilbert</span><span class="p">,</span><span class="ss">shortnames</span><span class="p" data-group-id="6360522870-3">]</span><span class="p" data-group-id="6360522870-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6360522870-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.102</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="6360522870-4">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">(dilbert@uab)3&gt; </span><span class="nf">node</span><span class="p" data-group-id="6360522870-5">(</span><span class="p" data-group-id="6360522870-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">dilbert@uab</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>A node with a long node name cannot communicate with a node with a short node
│ │ │ │  name.</p></section><h2 id="node-connections" class="section-heading">
│ │ │ │    <a href="#node-connections" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Node Connections</span>
│ │ │ │  </h2>
│ │ │ ├── OEBPS/design_principles.xhtml
│ │ │ │ @@ -57,135 +57,135 @@
│ │ │ │  the code for a process in a generic part (a behaviour module) and a specific
│ │ │ │  part (a <em>callback module</em>).</p><p>The behaviour module is part of Erlang/OTP. To implement a process such as a
│ │ │ │  supervisor, the user only needs to implement the callback module, which is to
│ │ │ │  export a pre-defined set of functions, the <em>callback functions</em>.</p><p>The following example illustrates how code can be divided into a generic and a
│ │ │ │  specific part. Consider the following code (written in plain Erlang) for a
│ │ │ │  simple server, which keeps track of a number of &quot;channels&quot;. Other processes can
│ │ │ │  allocate and free the channels by calling the functions <code class="inline">alloc/0</code> and <code class="inline">free/1</code>,
│ │ │ │ -respectively.</p><p><a href="" id="ch1"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8071823877-1">(</span><span class="ss">ch1</span><span class="p" data-group-id="8071823877-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8071823877-2">(</span><span class="p" data-group-id="8071823877-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8071823877-3">]</span><span class="p" data-group-id="8071823877-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8071823877-4">(</span><span class="p" data-group-id="8071823877-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8071823877-5">]</span><span class="p" data-group-id="8071823877-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8071823877-6">(</span><span class="p" data-group-id="8071823877-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8071823877-7">]</span><span class="p" data-group-id="8071823877-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +respectively.</p><p><a href="" id="ch1"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3861586989-1">(</span><span class="ss">ch1</span><span class="p" data-group-id="3861586989-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3861586989-2">(</span><span class="p" data-group-id="3861586989-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3861586989-3">]</span><span class="p" data-group-id="3861586989-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3861586989-4">(</span><span class="p" data-group-id="3861586989-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3861586989-5">]</span><span class="p" data-group-id="3861586989-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3861586989-6">(</span><span class="p" data-group-id="3861586989-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3861586989-7">]</span><span class="p" data-group-id="3861586989-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="8071823877-8">(</span><span class="p" data-group-id="8071823877-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="8071823877-9">(</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8071823877-10">[</span><span class="p" data-group-id="8071823877-10">]</span><span class="p" data-group-id="8071823877-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="3861586989-8">(</span><span class="p" data-group-id="3861586989-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="3861586989-9">(</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3861586989-10">[</span><span class="p" data-group-id="3861586989-10">]</span><span class="p" data-group-id="3861586989-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="8071823877-11">(</span><span class="p" data-group-id="8071823877-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ch1</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8071823877-12">{</span><span class="nf">self</span><span class="p" data-group-id="8071823877-13">(</span><span class="p" data-group-id="8071823877-13">)</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="8071823877-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="3861586989-11">(</span><span class="p" data-group-id="3861586989-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ch1</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3861586989-12">{</span><span class="nf">self</span><span class="p" data-group-id="3861586989-13">(</span><span class="p" data-group-id="3861586989-13">)</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="3861586989-12">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8071823877-14">{</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="8071823877-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3861586989-14">{</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="3861586989-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="n">Res</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="8071823877-15">(</span><span class="n">Ch</span><span class="p" data-group-id="8071823877-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ch1</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8071823877-16">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="8071823877-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="3861586989-15">(</span><span class="n">Ch</span><span class="p" data-group-id="3861586989-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ch1</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3861586989-16">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3861586989-16">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="8071823877-17">(</span><span class="p" data-group-id="8071823877-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="8071823877-18">(</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8071823877-19">(</span><span class="p" data-group-id="8071823877-19">)</span><span class="p" data-group-id="8071823877-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Chs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="8071823877-20">(</span><span class="p" data-group-id="8071823877-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="8071823877-21">(</span><span class="n">Chs</span><span class="p" data-group-id="8071823877-21">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="3861586989-17">(</span><span class="p" data-group-id="3861586989-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="3861586989-18">(</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3861586989-19">(</span><span class="p" data-group-id="3861586989-19">)</span><span class="p" data-group-id="3861586989-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Chs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="3861586989-20">(</span><span class="p" data-group-id="3861586989-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="3861586989-21">(</span><span class="n">Chs</span><span class="p" data-group-id="3861586989-21">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="8071823877-22">(</span><span class="n">Chs</span><span class="p" data-group-id="8071823877-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="3861586989-22">(</span><span class="n">Chs</span><span class="p" data-group-id="3861586989-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8071823877-23">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="8071823877-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="8071823877-24">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="8071823877-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="8071823877-25">(</span><span class="n">Chs</span><span class="p" data-group-id="8071823877-25">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8071823877-26">{</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="8071823877-26">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="8071823877-27">(</span><span class="n">Chs2</span><span class="p" data-group-id="8071823877-27">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8071823877-28">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="8071823877-28">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="8071823877-29">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="8071823877-29">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="8071823877-30">(</span><span class="n">Chs2</span><span class="p" data-group-id="8071823877-30">)</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>The code for the server can be rewritten into a generic part <code class="inline">server.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8334112450-1">(</span><span class="ss">server</span><span class="p" data-group-id="8334112450-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8334112450-2">(</span><span class="p" data-group-id="8334112450-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8334112450-3">]</span><span class="p" data-group-id="8334112450-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8334112450-4">(</span><span class="p" data-group-id="8334112450-5">[</span><span class="ss">call</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8334112450-5">]</span><span class="p" data-group-id="8334112450-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8334112450-6">(</span><span class="p" data-group-id="8334112450-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8334112450-7">]</span><span class="p" data-group-id="8334112450-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3861586989-23">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="3861586989-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="3861586989-24">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="3861586989-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="3861586989-25">(</span><span class="n">Chs</span><span class="p" data-group-id="3861586989-25">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3861586989-26">{</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3861586989-26">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="3861586989-27">(</span><span class="n">Chs2</span><span class="p" data-group-id="3861586989-27">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3861586989-28">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3861586989-28">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="3861586989-29">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3861586989-29">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="3861586989-30">(</span><span class="n">Chs2</span><span class="p" data-group-id="3861586989-30">)</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>The code for the server can be rewritten into a generic part <code class="inline">server.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4655706906-1">(</span><span class="ss">server</span><span class="p" data-group-id="4655706906-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4655706906-2">(</span><span class="p" data-group-id="4655706906-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4655706906-3">]</span><span class="p" data-group-id="4655706906-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4655706906-4">(</span><span class="p" data-group-id="4655706906-5">[</span><span class="ss">call</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4655706906-5">]</span><span class="p" data-group-id="4655706906-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4655706906-6">(</span><span class="p" data-group-id="4655706906-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4655706906-7">]</span><span class="p" data-group-id="4655706906-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="8334112450-8">(</span><span class="n">Mod</span><span class="p" data-group-id="8334112450-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="8334112450-9">(</span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8334112450-10">[</span><span class="n">Mod</span><span class="p" data-group-id="8334112450-10">]</span><span class="p" data-group-id="8334112450-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="4655706906-8">(</span><span class="n">Mod</span><span class="p" data-group-id="4655706906-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="4655706906-9">(</span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4655706906-10">[</span><span class="n">Mod</span><span class="p" data-group-id="4655706906-10">]</span><span class="p" data-group-id="4655706906-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">call</span><span class="p" data-group-id="8334112450-11">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="8334112450-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Name</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8334112450-12">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8334112450-13">(</span><span class="p" data-group-id="8334112450-13">)</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="8334112450-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">call</span><span class="p" data-group-id="4655706906-11">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="4655706906-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Name</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4655706906-12">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4655706906-13">(</span><span class="p" data-group-id="4655706906-13">)</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="4655706906-12">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8334112450-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="8334112450-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="4655706906-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="4655706906-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="n">Res</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">cast</span><span class="p" data-group-id="8334112450-15">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="8334112450-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Name</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8334112450-16">{</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="8334112450-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">cast</span><span class="p" data-group-id="4655706906-15">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="4655706906-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Name</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4655706906-16">{</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="4655706906-16">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="8334112450-17">(</span><span class="n">Mod</span><span class="p" data-group-id="8334112450-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="8334112450-18">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8334112450-19">(</span><span class="p" data-group-id="8334112450-19">)</span><span class="p" data-group-id="8334112450-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">init</span><span class="p" data-group-id="8334112450-20">(</span><span class="p" data-group-id="8334112450-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="8334112450-21">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8334112450-21">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="4655706906-17">(</span><span class="n">Mod</span><span class="p" data-group-id="4655706906-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="4655706906-18">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4655706906-19">(</span><span class="p" data-group-id="4655706906-19">)</span><span class="p" data-group-id="4655706906-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">init</span><span class="p" data-group-id="4655706906-20">(</span><span class="p" data-group-id="4655706906-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="4655706906-21">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4655706906-21">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="8334112450-22">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8334112450-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="4655706906-22">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4655706906-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8334112450-23">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="8334112450-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="8334112450-24">{</span><span class="n">Res</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="8334112450-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">handle_call</span><span class="p" data-group-id="8334112450-25">(</span><span class="n">Req</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8334112450-25">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8334112450-26">{</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="8334112450-26">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="8334112450-27">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="8334112450-27">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8334112450-28">{</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="8334112450-28">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">State2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">handle_cast</span><span class="p" data-group-id="8334112450-29">(</span><span class="n">Req</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8334112450-29">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="8334112450-30">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="8334112450-30">)</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>And a callback module <code class="inline">ch2.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1645126566-1">(</span><span class="ss">ch2</span><span class="p" data-group-id="1645126566-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1645126566-2">(</span><span class="p" data-group-id="1645126566-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1645126566-3">]</span><span class="p" data-group-id="1645126566-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1645126566-4">(</span><span class="p" data-group-id="1645126566-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1645126566-5">]</span><span class="p" data-group-id="1645126566-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1645126566-6">(</span><span class="p" data-group-id="1645126566-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1645126566-7">]</span><span class="p" data-group-id="1645126566-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="1645126566-8">(</span><span class="p" data-group-id="1645126566-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1645126566-9">(</span><span class="ss">ch2</span><span class="p" data-group-id="1645126566-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="1645126566-10">(</span><span class="p" data-group-id="1645126566-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="1645126566-11">(</span><span class="ss">ch2</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="1645126566-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="1645126566-12">(</span><span class="n">Ch</span><span class="p" data-group-id="1645126566-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="1645126566-13">(</span><span class="ss">ch2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1645126566-14">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1645126566-14">}</span><span class="p" data-group-id="1645126566-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="4655706906-23">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="4655706906-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="4655706906-24">{</span><span class="n">Res</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="4655706906-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">handle_call</span><span class="p" data-group-id="4655706906-25">(</span><span class="n">Req</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4655706906-25">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4655706906-26">{</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="4655706906-26">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="4655706906-27">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="4655706906-27">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="4655706906-28">{</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="4655706906-28">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">State2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">handle_cast</span><span class="p" data-group-id="4655706906-29">(</span><span class="n">Req</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4655706906-29">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="4655706906-30">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="4655706906-30">)</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>And a callback module <code class="inline">ch2.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2529883903-1">(</span><span class="ss">ch2</span><span class="p" data-group-id="2529883903-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2529883903-2">(</span><span class="p" data-group-id="2529883903-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2529883903-3">]</span><span class="p" data-group-id="2529883903-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2529883903-4">(</span><span class="p" data-group-id="2529883903-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2529883903-5">]</span><span class="p" data-group-id="2529883903-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2529883903-6">(</span><span class="p" data-group-id="2529883903-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2529883903-7">]</span><span class="p" data-group-id="2529883903-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="2529883903-8">(</span><span class="p" data-group-id="2529883903-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2529883903-9">(</span><span class="ss">ch2</span><span class="p" data-group-id="2529883903-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="2529883903-10">(</span><span class="p" data-group-id="2529883903-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="2529883903-11">(</span><span class="ss">ch2</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="2529883903-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="2529883903-12">(</span><span class="n">Ch</span><span class="p" data-group-id="2529883903-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="2529883903-13">(</span><span class="ss">ch2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2529883903-14">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2529883903-14">}</span><span class="p" data-group-id="2529883903-13">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="1645126566-15">(</span><span class="p" data-group-id="1645126566-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">channels</span><span class="p" data-group-id="1645126566-16">(</span><span class="p" data-group-id="1645126566-16">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="2529883903-15">(</span><span class="p" data-group-id="2529883903-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">channels</span><span class="p" data-group-id="2529883903-16">(</span><span class="p" data-group-id="2529883903-16">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="1645126566-17">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1645126566-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">alloc</span><span class="p" data-group-id="1645126566-18">(</span><span class="n">Chs</span><span class="p" data-group-id="1645126566-18">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% =&gt; {Ch,Chs2}</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="2529883903-17">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2529883903-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">alloc</span><span class="p" data-group-id="2529883903-18">(</span><span class="n">Chs</span><span class="p" data-group-id="2529883903-18">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% =&gt; {Ch,Chs2}</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="1645126566-19">(</span><span class="p" data-group-id="1645126566-20">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1645126566-20">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1645126566-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">free</span><span class="p" data-group-id="1645126566-21">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1645126566-21">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% =&gt; Chs2</span></code></pre><p>Notice the following:</p><ul><li>The code in <code class="inline">server</code> can be reused to build many different servers.</li><li>The server name, in this example the atom <code class="inline">ch2</code>, is hidden from the users of
│ │ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="2529883903-19">(</span><span class="p" data-group-id="2529883903-20">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2529883903-20">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2529883903-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">free</span><span class="p" data-group-id="2529883903-21">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2529883903-21">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% =&gt; Chs2</span></code></pre><p>Notice the following:</p><ul><li>The code in <code class="inline">server</code> can be reused to build many different servers.</li><li>The server name, in this example the atom <code class="inline">ch2</code>, is hidden from the users of
│ │ │ │  the client functions. This means that the name can be changed without
│ │ │ │  affecting them.</li><li>The protocol (messages sent to and received from the server) is also hidden.
│ │ │ │  This is good programming practice and allows one to change the protocol
│ │ │ │  without changing the code using the interface functions.</li><li>The functionality of <code class="inline">server</code> can be extended without having to change <code class="inline">ch2</code>
│ │ │ │  or any other callback module.</li></ul><p>In <code class="inline">ch1.erl</code> and <code class="inline">ch2.erl</code> above, the implementation of <code class="inline">channels/0</code>, <code class="inline">alloc/1</code>,
│ │ │ │  and <code class="inline">free/2</code> has been intentionally left out, as it is not relevant to the
│ │ │ │  example. For completeness, one way to write these functions is given below. This
│ │ │ │  is an example only, a realistic implementation must be able to handle situations
│ │ │ │ -like running out of channels to allocate, and so on.</p><p><a href="" id="channels-implementation"></a></p><pre><code class="makeup erlang" translate="no"><span class="nf">channels</span><span class="p" data-group-id="9015384866-1">(</span><span class="p" data-group-id="9015384866-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="9015384866-2">{</span><span class="p">_</span><span class="n">Allocated</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9015384866-3">[</span><span class="p" data-group-id="9015384866-3">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Free</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="9015384866-4">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">100</span><span class="p" data-group-id="9015384866-4">)</span><span class="p" data-group-id="9015384866-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +like running out of channels to allocate, and so on.</p><p><a href="" id="channels-implementation"></a></p><pre><code class="makeup erlang" translate="no"><span class="nf">channels</span><span class="p" data-group-id="8759555796-1">(</span><span class="p" data-group-id="8759555796-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="8759555796-2">{</span><span class="p">_</span><span class="n">Allocated</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8759555796-3">[</span><span class="p" data-group-id="8759555796-3">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Free</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="8759555796-4">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">100</span><span class="p" data-group-id="8759555796-4">)</span><span class="p" data-group-id="8759555796-2">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="9015384866-5">(</span><span class="p" data-group-id="9015384866-6">{</span><span class="n">Allocated</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9015384866-7">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9015384866-7">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">_</span><span class="n">Free</span><span class="p" data-group-id="9015384866-6">}</span><span class="p" data-group-id="9015384866-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="9015384866-8">{</span><span class="n">H</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9015384866-9">{</span><span class="p" data-group-id="9015384866-10">[</span><span class="n">H</span><span class="p">|</span><span class="n">Allocated</span><span class="p" data-group-id="9015384866-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="9015384866-9">}</span><span class="p" data-group-id="9015384866-8">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="8759555796-5">(</span><span class="p" data-group-id="8759555796-6">{</span><span class="n">Allocated</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8759555796-7">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8759555796-7">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">_</span><span class="n">Free</span><span class="p" data-group-id="8759555796-6">}</span><span class="p" data-group-id="8759555796-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="8759555796-8">{</span><span class="n">H</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8759555796-9">{</span><span class="p" data-group-id="8759555796-10">[</span><span class="n">H</span><span class="p">|</span><span class="n">Allocated</span><span class="p" data-group-id="8759555796-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="8759555796-9">}</span><span class="p" data-group-id="8759555796-8">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="9015384866-11">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9015384866-12">{</span><span class="n">Alloc</span><span class="p">,</span><span class="w"> </span><span class="n">Free</span><span class="p" data-group-id="9015384866-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Channels</span><span class="p" data-group-id="9015384866-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="9015384866-13">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="9015384866-13">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="8759555796-11">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8759555796-12">{</span><span class="n">Alloc</span><span class="p">,</span><span class="w"> </span><span class="n">Free</span><span class="p" data-group-id="8759555796-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Channels</span><span class="p" data-group-id="8759555796-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="8759555796-13">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="8759555796-13">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │        </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="9015384866-14">{</span><span class="nc">lists</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="9015384866-15">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="9015384866-15">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9015384866-16">[</span><span class="n">Ch</span><span class="p">|</span><span class="n">Free</span><span class="p" data-group-id="9015384866-16">]</span><span class="p" data-group-id="9015384866-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="8759555796-14">{</span><span class="nc">lists</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="8759555796-15">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="8759555796-15">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8759555796-16">[</span><span class="n">Ch</span><span class="p">|</span><span class="n">Free</span><span class="p" data-group-id="8759555796-16">]</span><span class="p" data-group-id="8759555796-14">}</span><span class="p">;</span><span class="w">
│ │ │ │        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │           </span><span class="n">Channels</span><span class="w">
│ │ │ │     </span><span class="k">end</span><span class="p">.</span></code></pre><p>Code written without using behaviours can be more efficient, but the increased
│ │ │ │  efficiency is at the expense of generality. The ability to manage all
│ │ │ │  applications in the system in a consistent manner is important.</p><p>Using behaviours also makes it easier to read and understand code written by
│ │ │ │  other programmers. Improvised programming structures, while possibly more
│ │ │ │  efficient, are always more difficult to understand.</p><p>The <code class="inline">server</code> module corresponds, greatly simplified, to the Erlang/OTP behaviour
│ │ │ │  <code class="inline">gen_server</code>.</p><p>The standard Erlang/OTP behaviours are:</p><ul><li><p><a href="gen_server_concepts.xhtml">gen_server</a></p><p>For implementing the server of a client-server relation</p></li><li><p><a href="statem.xhtml">gen_statem</a></p><p>For implementing state machines</p></li><li><p><a href="events.xhtml">gen_event</a></p><p>For implementing event handling functionality</p></li><li><p><a href="sup_princ.xhtml">supervisor</a></p><p>For implementing a supervisor in a supervision tree</p></li></ul><p>The compiler understands the module attribute <code class="inline">-behaviour(Behaviour)</code> and issues
│ │ │ │ -warnings about missing callback functions, for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4503952849-1">(</span><span class="ss">chs3</span><span class="p" data-group-id="4503952849-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="4503952849-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="4503952849-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +warnings about missing callback functions, for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4112446088-1">(</span><span class="ss">chs3</span><span class="p" data-group-id="4112446088-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="4112446088-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="4112446088-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">c</span><span class="p" data-group-id="4503952849-3">(</span><span class="ss">chs3</span><span class="p" data-group-id="4503952849-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">c</span><span class="p" data-group-id="4112446088-3">(</span><span class="ss">chs3</span><span class="p" data-group-id="4112446088-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="o">/</span><span class="ss">chs3</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">10</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="ss">undefined</span><span class="w"> </span><span class="ss">call</span><span class="o">-</span><span class="ss">back</span><span class="w"> </span><span class="ss">function</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4503952849-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">chs3</span><span class="p" data-group-id="4503952849-4">}</span></code></pre><h2 id="applications" class="section-heading">
│ │ │ │ +</span><span class="p" data-group-id="4112446088-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">chs3</span><span class="p" data-group-id="4112446088-4">}</span></code></pre><h2 id="applications" class="section-heading">
│ │ │ │    <a href="#applications" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Applications</span>
│ │ │ │  </h2>
│ │ │ │  <p>Erlang/OTP comes with a number of components, each implementing some specific
│ │ │ │  functionality. Components are with Erlang/OTP terminology called <em>applications</em>.
│ │ │ ├── OEBPS/data_types.xhtml
│ │ │ │ @@ -104,18 +104,18 @@
│ │ │ │    </a>
│ │ │ │    <span class="text">Representation of Floating-Point Numbers</span>
│ │ │ │  </h3>
│ │ │ │  <p>When working with floats, you may not see what you expect when printing or doing
│ │ │ │  arithmetic operations. This is because floats are represented by a fixed number
│ │ │ │  of bits in a base-2 system while printed floats are represented with a base-10
│ │ │ │  system. Erlang uses 64-bit floats. Here are examples of this phenomenon:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="mf">0.1</span><span class="o">+</span><span class="mf">0.2</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="mf">0.30000000000000004</span></code></pre><p>The real numbers <code class="inline">0.1</code> and <code class="inline">0.2</code> cannot be represented exactly as floats.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5317144039-1">{</span><span class="mf">36028797018963968.0</span><span class="p">,</span><span class="w"> </span><span class="mi">36028797018963968</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mf">36028797018963968.0</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="mf">36028797018963970.0</span><span class="p">,</span><span class="w"> </span><span class="mi">36028797018963970</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mf">36028797018963970.0</span><span class="p" data-group-id="5317144039-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5317144039-2">{</span><span class="mf">3.602879701896397e16</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="mf">3.602879701896397e16</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="5317144039-2">}</span><span class="p">.</span></code></pre><p>The value <code class="inline">36028797018963968</code> can be represented exactly as a float value but
│ │ │ │ +</span><span class="mf">0.30000000000000004</span></code></pre><p>The real numbers <code class="inline">0.1</code> and <code class="inline">0.2</code> cannot be represented exactly as floats.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9750850984-1">{</span><span class="mf">36028797018963968.0</span><span class="p">,</span><span class="w"> </span><span class="mi">36028797018963968</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mf">36028797018963968.0</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="mf">36028797018963970.0</span><span class="p">,</span><span class="w"> </span><span class="mi">36028797018963970</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mf">36028797018963970.0</span><span class="p" data-group-id="9750850984-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9750850984-2">{</span><span class="mf">3.602879701896397e16</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="mf">3.602879701896397e16</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="9750850984-2">}</span><span class="p">.</span></code></pre><p>The value <code class="inline">36028797018963968</code> can be represented exactly as a float value but
│ │ │ │  Erlang's pretty printer rounds <code class="inline">36028797018963968.0</code> to <code class="inline">3.602879701896397e16</code>
│ │ │ │  (<code class="inline">=36028797018963970.0</code>) as all values in the range
│ │ │ │  <code class="inline">[36028797018963966.0, 36028797018963972.0]</code> are represented by
│ │ │ │  <code class="inline">36028797018963968.0</code>.</p><p>For more information about floats and issues with them, see:</p><ul><li><a href="https://floating-point-gui.de/">What Every Programmer Should Know About Floating-Point Arithmetic</a></li><li><a href="https://0.30000000000000004.com/">0.30000000000000004.com/</a></li><li><a href="https://docs.python.org/3/tutorial/floatingpoint.html">Floating Point Arithmetic: Issues and Limitations</a></li></ul><p>If you need to work with exact decimal fractions, for instance to represent
│ │ │ │  money, it is recommended to use a library that handles that, or work in
│ │ │ │  cents instead of dollars or euros so that decimal fractions are not needed.</p><p>Also note that Erlang's floats do not exactly match IEEE 754 floats,
│ │ │ │  in that neither <em>Inf</em> nor <em>NaN</em> are supported in Erlang. Any
│ │ │ │ @@ -149,52 +149,52 @@
│ │ │ │  by eight are called <em>binaries</em>.</p><p><em>Examples:</em></p><pre><code class="text">1&gt; &lt;&lt;10,20&gt;&gt;.
│ │ │ │  &lt;&lt;10,20&gt;&gt;
│ │ │ │  2&gt; &lt;&lt;&quot;ABC&quot;&gt;&gt;.
│ │ │ │  &lt;&lt;&quot;ABC&quot;&gt;&gt;
│ │ │ │  3&gt; &lt;&lt;1:1,0:1&gt;&gt;.
│ │ │ │  &lt;&lt;2:2&gt;&gt;</code></pre><p>The <a href="../../../lib/../erts/doc/html/erlang.html#is_bitstring/1"><code class="inline">is_bitstring/1</code></a> BIF tests whether a
│ │ │ │  term is a bit string, and the <a href="../../../lib/../erts/doc/html/erlang.html#is_binary/1"><code class="inline">is_binary/1</code></a>
│ │ │ │ -BIF tests whether a term is a binary.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">is_bitstring</span><span class="p" data-group-id="7573650644-1">(</span><span class="p" data-group-id="7573650644-2">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="7573650644-2">&gt;&gt;</span><span class="p" data-group-id="7573650644-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +BIF tests whether a term is a binary.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">is_bitstring</span><span class="p" data-group-id="2626024698-1">(</span><span class="p" data-group-id="2626024698-2">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="2626024698-2">&gt;&gt;</span><span class="p" data-group-id="2626024698-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">is_binary</span><span class="p" data-group-id="7573650644-3">(</span><span class="p" data-group-id="7573650644-4">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="7573650644-4">&gt;&gt;</span><span class="p" data-group-id="7573650644-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">is_binary</span><span class="p" data-group-id="2626024698-3">(</span><span class="p" data-group-id="2626024698-4">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="2626024698-4">&gt;&gt;</span><span class="p" data-group-id="2626024698-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">is_binary</span><span class="p" data-group-id="7573650644-5">(</span><span class="p" data-group-id="7573650644-6">&lt;&lt;</span><span class="mi">42</span><span class="p" data-group-id="7573650644-6">&gt;&gt;</span><span class="p" data-group-id="7573650644-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">is_binary</span><span class="p" data-group-id="2626024698-5">(</span><span class="p" data-group-id="2626024698-6">&lt;&lt;</span><span class="mi">42</span><span class="p" data-group-id="2626024698-6">&gt;&gt;</span><span class="p" data-group-id="2626024698-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │  </span></code></pre><p>For more examples, see <a href="../../../lib/../system/doc/html/bit_syntax.xhtml">Programming Examples</a>.</p><h2 id="reference" class="section-heading">
│ │ │ │    <a href="#reference" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Reference</span>
│ │ │ │  </h2>
│ │ │ │  <p>A term that is <a href="../../../lib/../system/doc/html/system_limits.xhtml#unique_references">unique</a>
│ │ │ │  among connected nodes. A reference is created by calling the
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#make_ref/0"><code class="inline">make_ref/0</code></a> BIF. The
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#is_reference/1"><code class="inline">is_reference/1</code></a> BIF tests whether a term
│ │ │ │ -is a reference.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Ref</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="1928260779-1">(</span><span class="p" data-group-id="1928260779-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +is a reference.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Ref</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="2048595166-1">(</span><span class="p" data-group-id="2048595166-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Ref</span><span class="o">&lt;</span><span class="mf">0.76482849</span><span class="p">.</span><span class="mf">3801088007.198204</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">is_reference</span><span class="p" data-group-id="1928260779-2">(</span><span class="n">Ref</span><span class="p" data-group-id="1928260779-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">is_reference</span><span class="p" data-group-id="2048595166-2">(</span><span class="n">Ref</span><span class="p" data-group-id="2048595166-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span></code></pre><h2 id="fun" class="section-heading">
│ │ │ │    <a href="#fun" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Fun</span>
│ │ │ │  </h2>
│ │ │ │  <p>A fun is a functional object. Funs make it possible to create an anonymous
│ │ │ │  function and pass the function itself — not its name — as an argument to other
│ │ │ │ -functions.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5427462638-1">(</span><span class="n">X</span><span class="p" data-group-id="5427462638-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +functions.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="6600161369-1">(</span><span class="n">X</span><span class="p" data-group-id="6600161369-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.39074546</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">Fun1</span><span class="p" data-group-id="5427462638-2">(</span><span class="mi">2</span><span class="p" data-group-id="5427462638-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">Fun1</span><span class="p" data-group-id="6600161369-2">(</span><span class="mi">2</span><span class="p" data-group-id="6600161369-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span></code></pre><p>The <a href="../../../lib/../erts/doc/html/erlang.html#is_function/1"><code class="inline">is_function/1</code></a> and <a href="../../../lib/../erts/doc/html/erlang.html#is_function/2"><code class="inline">is_function/2</code></a>
│ │ │ │ -BIFs test whether a term is a fun.</p><p><em>Examples</em>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="7247435375-1">(</span><span class="p" data-group-id="7247435375-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +BIFs test whether a term is a fun.</p><p><em>Examples</em>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="2934134784-1">(</span><span class="p" data-group-id="2934134784-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">43.105768164</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="7247435375-2">(</span><span class="n">F</span><span class="p" data-group-id="7247435375-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="2934134784-2">(</span><span class="n">F</span><span class="p" data-group-id="2934134784-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="7247435375-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="7247435375-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="2934134784-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="2934134784-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="7247435375-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="7247435375-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="2934134784-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2934134784-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span></code></pre><p>Read more about funs in <a href="expressions.xhtml#fun-expressions">Fun Expressions</a>. For more
│ │ │ │  examples, see <a href="../../../lib/../system/doc/html/funs.xhtml">Programming Examples</a>.</p><h2 id="port-identifier" class="section-heading">
│ │ │ │    <a href="#port-identifier" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Port Identifier</span>
│ │ │ │  </h2>
│ │ │ │ @@ -212,94 +212,94 @@
│ │ │ │  for a new process after a while.</p><p>The BIF <a href="../../../lib/../erts/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a> returns the Pid of the calling process. When
│ │ │ │  <a href="ref_man_processes.xhtml#process-creation">creating a new process</a>, the parent
│ │ │ │  process will be able to get the Pid of the child process either via the return
│ │ │ │  value, as is the case when calling the <a href="../../../lib/../erts/doc/html/erlang.html#spawn/3"><code class="inline">spawn/3</code></a> BIF, or via
│ │ │ │  a message, which is the case when calling the
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#spawn_request/5"><code class="inline">spawn_request/5</code></a> BIF. A Pid is typically used
│ │ │ │  when sending a process a <a href="ref_man_processes.xhtml#signals">signal</a>. The
│ │ │ │ -<a href="../../../lib/../erts/doc/html/erlang.html#is_pid/1"><code class="inline">is_pid/1</code></a> BIF tests whether a term is a Pid.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1616066939-1">(</span><span class="ss">m</span><span class="p" data-group-id="1616066939-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1616066939-2">(</span><span class="p" data-group-id="1616066939-3">[</span><span class="ss">loop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1616066939-3">]</span><span class="p" data-group-id="1616066939-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<a href="../../../lib/../erts/doc/html/erlang.html#is_pid/1"><code class="inline">is_pid/1</code></a> BIF tests whether a term is a Pid.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6878599080-1">(</span><span class="ss">m</span><span class="p" data-group-id="6878599080-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6878599080-2">(</span><span class="p" data-group-id="6878599080-3">[</span><span class="ss">loop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6878599080-3">]</span><span class="p" data-group-id="6878599080-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="1616066939-4">(</span><span class="p" data-group-id="1616066939-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="6878599080-4">(</span><span class="p" data-group-id="6878599080-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">who_are_you</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1616066939-5">(</span><span class="s">&quot;I am </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1616066939-6">[</span><span class="nf">self</span><span class="p" data-group-id="1616066939-7">(</span><span class="p" data-group-id="1616066939-7">)</span><span class="p" data-group-id="1616066939-6">]</span><span class="p" data-group-id="1616066939-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="1616066939-8">(</span><span class="p" data-group-id="1616066939-8">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6878599080-5">(</span><span class="s">&quot;I am </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6878599080-6">[</span><span class="nf">self</span><span class="p" data-group-id="6878599080-7">(</span><span class="p" data-group-id="6878599080-7">)</span><span class="p" data-group-id="6878599080-6">]</span><span class="p" data-group-id="6878599080-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="6878599080-8">(</span><span class="p" data-group-id="6878599080-8">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="1616066939-9">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">loop</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1616066939-10">[</span><span class="p" data-group-id="1616066939-10">]</span><span class="p" data-group-id="1616066939-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="6878599080-9">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">loop</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6878599080-10">[</span><span class="p" data-group-id="6878599080-10">]</span><span class="p" data-group-id="6878599080-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">0.58</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">2&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">who_are_you</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="n">I</span><span class="w"> </span><span class="ss">am</span><span class="w"> </span><span class="o">&lt;</span><span class="mf">0.58</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ │  </span><span class="ss">who_are_you</span></code></pre><p>Read more about processes in <a href="ref_man_processes.xhtml">Processes</a>.</p><h2 id="tuple" class="section-heading">
│ │ │ │    <a href="#tuple" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Tuple</span>
│ │ │ │  </h2>
│ │ │ │  <p>A tuple is a compound data type with a fixed number of terms:</p><pre><code class="text">{Term1,...,TermN}</code></pre><p>Each term <code class="inline">Term</code> in the tuple is called an <em>element</em>. The number of elements is
│ │ │ │ -said to be the <em>size</em> of the tuple.</p><p>There are a number of BIFs to manipulate tuples.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2466307908-1">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">24</span><span class="p">,</span><span class="p" data-group-id="2466307908-2">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="2466307908-2">}</span><span class="p" data-group-id="2466307908-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2466307908-3">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">24</span><span class="p">,</span><span class="p" data-group-id="2466307908-4">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="2466307908-4">}</span><span class="p" data-group-id="2466307908-3">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">element</span><span class="p" data-group-id="2466307908-5">(</span><span class="mi">1</span><span class="p">,</span><span class="n">P</span><span class="p" data-group-id="2466307908-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +said to be the <em>size</em> of the tuple.</p><p>There are a number of BIFs to manipulate tuples.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4911235386-1">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">24</span><span class="p">,</span><span class="p" data-group-id="4911235386-2">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="4911235386-2">}</span><span class="p" data-group-id="4911235386-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4911235386-3">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">24</span><span class="p">,</span><span class="p" data-group-id="4911235386-4">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="4911235386-4">}</span><span class="p" data-group-id="4911235386-3">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">element</span><span class="p" data-group-id="4911235386-5">(</span><span class="mi">1</span><span class="p">,</span><span class="n">P</span><span class="p" data-group-id="4911235386-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">adam</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">element</span><span class="p" data-group-id="2466307908-6">(</span><span class="mi">3</span><span class="p">,</span><span class="n">P</span><span class="p" data-group-id="2466307908-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2466307908-7">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="2466307908-7">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="n">P2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="2466307908-8">(</span><span class="mi">2</span><span class="p">,</span><span class="n">P</span><span class="p">,</span><span class="mi">25</span><span class="p" data-group-id="2466307908-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2466307908-9">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">25</span><span class="p">,</span><span class="p" data-group-id="2466307908-10">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="2466307908-10">}</span><span class="p" data-group-id="2466307908-9">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="2466307908-11">(</span><span class="n">P</span><span class="p" data-group-id="2466307908-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">element</span><span class="p" data-group-id="4911235386-6">(</span><span class="mi">3</span><span class="p">,</span><span class="n">P</span><span class="p" data-group-id="4911235386-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4911235386-7">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="4911235386-7">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="n">P2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="4911235386-8">(</span><span class="mi">2</span><span class="p">,</span><span class="n">P</span><span class="p">,</span><span class="mi">25</span><span class="p" data-group-id="4911235386-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4911235386-9">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">25</span><span class="p">,</span><span class="p" data-group-id="4911235386-10">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="4911235386-10">}</span><span class="p" data-group-id="4911235386-9">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="4911235386-11">(</span><span class="n">P</span><span class="p" data-group-id="4911235386-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="2466307908-12">(</span><span class="p" data-group-id="2466307908-13">{</span><span class="p" data-group-id="2466307908-13">}</span><span class="p" data-group-id="2466307908-12">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="4911235386-12">(</span><span class="p" data-group-id="4911235386-13">{</span><span class="p" data-group-id="4911235386-13">}</span><span class="p" data-group-id="4911235386-12">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">0</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">7&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="2466307908-14">(</span><span class="p" data-group-id="2466307908-15">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="2466307908-15">}</span><span class="p" data-group-id="2466307908-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">7&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="4911235386-14">(</span><span class="p" data-group-id="4911235386-15">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4911235386-15">}</span><span class="p" data-group-id="4911235386-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span></code></pre><h2 id="map" class="section-heading">
│ │ │ │    <a href="#map" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Map</span>
│ │ │ │  </h2>
│ │ │ │  <p>A map is a compound data type with a variable number of key-value associations:</p><pre><code class="text">#{Key1 =&gt; Value1, ..., KeyN =&gt; ValueN}</code></pre><p>Each key-value association in the map is called an <em>association pair</em>. The key
│ │ │ │  and value parts of the pair are called <em>elements</em>. The number of association
│ │ │ │ -pairs is said to be the <em>size</em> of the map.</p><p>There are a number of BIFs to manipulate maps.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7994042917-1">#{</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">24</span><span class="p">,</span><span class="w"> </span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7994042917-2">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="7994042917-2">}</span><span class="p" data-group-id="7994042917-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7994042917-3">#{</span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">24</span><span class="p">,</span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7994042917-4">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="7994042917-4">}</span><span class="p">,</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p" data-group-id="7994042917-3">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">maps</span><span class="p">:</span><span class="nf">get</span><span class="p" data-group-id="7994042917-5">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="7994042917-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +pairs is said to be the <em>size</em> of the map.</p><p>There are a number of BIFs to manipulate maps.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1296054815-1">#{</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">24</span><span class="p">,</span><span class="w"> </span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1296054815-2">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="1296054815-2">}</span><span class="p" data-group-id="1296054815-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1296054815-3">#{</span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">24</span><span class="p">,</span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1296054815-4">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="1296054815-4">}</span><span class="p">,</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p" data-group-id="1296054815-3">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">maps</span><span class="p">:</span><span class="nf">get</span><span class="p" data-group-id="1296054815-5">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="1296054815-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">adam</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">maps</span><span class="p">:</span><span class="nf">get</span><span class="p" data-group-id="7994042917-6">(</span><span class="ss">date</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="7994042917-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7994042917-7">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="7994042917-7">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="7994042917-8">(</span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="mi">25</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="7994042917-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7994042917-9">#{</span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">25</span><span class="p">,</span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7994042917-10">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="7994042917-10">}</span><span class="p">,</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p" data-group-id="7994042917-9">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="7994042917-11">(</span><span class="n">M2</span><span class="p" data-group-id="7994042917-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">maps</span><span class="p">:</span><span class="nf">get</span><span class="p" data-group-id="1296054815-6">(</span><span class="ss">date</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="1296054815-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1296054815-7">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="1296054815-7">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="1296054815-8">(</span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="mi">25</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="1296054815-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1296054815-9">#{</span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">25</span><span class="p">,</span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1296054815-10">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="1296054815-10">}</span><span class="p">,</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p" data-group-id="1296054815-9">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="1296054815-11">(</span><span class="n">M2</span><span class="p" data-group-id="1296054815-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="7994042917-12">(</span><span class="p" data-group-id="7994042917-13">#{</span><span class="p" data-group-id="7994042917-13">}</span><span class="p" data-group-id="7994042917-12">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="1296054815-12">(</span><span class="p" data-group-id="1296054815-13">#{</span><span class="p" data-group-id="1296054815-13">}</span><span class="p" data-group-id="1296054815-12">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">0</span></code></pre><p>A collection of map-processing functions can be found in the module <a href="../../../lib/stdlib/doc/html/maps.html"><code class="inline">maps</code></a>
│ │ │ │  in STDLIB.</p><p>Read more about maps in <a href="expressions.xhtml#map-expressions">Map Expressions</a>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Maps were introduced as an experimental feature in Erlang/OTP R17. Their
│ │ │ │  functionality was extended and became fully supported in Erlang/OTP 18.</p></section><h2 id="list" class="section-heading">
│ │ │ │    <a href="#list" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">List</span>
│ │ │ │  </h2>
│ │ │ │  <p>A list is a compound data type with a variable number of terms.</p><pre><code class="text">[Term1,...,TermN]</code></pre><p>Each term <code class="inline">Term</code> in the list is called an <em>element</em>. The number of elements is
│ │ │ │  said to be the <em>length</em> of the list.</p><p>Formally, a list is either the empty list <code class="inline">[]</code> or consists of a <em>head</em> (first
│ │ │ │  element) and a <em>tail</em> (remainder of the list). The <em>tail</em> is also a list. The
│ │ │ │  latter can be expressed as <code class="inline">[H|T]</code>. The notation <code class="inline">[Term1,...,TermN]</code> above is
│ │ │ │  equivalent to the list <code class="inline">[Term1|[...|[TermN|[]]]]</code>.</p><p><em>Example:</em></p><p><code class="inline">[]</code> is a list, thus<br/><code class="inline">[c|[]]</code> is a list, thus<br/><code class="inline">[b|[c|[]]]</code> is a list, thus<br/><code class="inline">[a|[b|[c|[]]]]</code> is a list, or in short <code class="inline">[a,b,c]</code></p><p>A list where the tail is a list is sometimes called a <em>proper list</em>. It is
│ │ │ │  allowed to have a list where the tail is not a list, for example, <code class="inline">[a|b]</code>.
│ │ │ │ -However, this type of list is of little practical use.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">L1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5544787080-1">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="5544787080-2">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5544787080-2">}</span><span class="p" data-group-id="5544787080-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5544787080-3">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="5544787080-4">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5544787080-4">}</span><span class="p" data-group-id="5544787080-3">]</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="5544787080-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5544787080-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L1</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5544787080-6">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="5544787080-7">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5544787080-7">}</span><span class="p" data-group-id="5544787080-6">]</span><span class="w">
│ │ │ │ +However, this type of list is of little practical use.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">L1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0170406268-1">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="0170406268-2">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0170406268-2">}</span><span class="p" data-group-id="0170406268-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0170406268-3">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="0170406268-4">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0170406268-4">}</span><span class="p" data-group-id="0170406268-3">]</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="0170406268-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0170406268-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L1</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0170406268-6">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="0170406268-7">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0170406268-7">}</span><span class="p" data-group-id="0170406268-6">]</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">3&gt; </span><span class="n">H</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">a</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">4&gt; </span><span class="n">T</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5544787080-8">[</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="5544787080-9">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5544787080-9">}</span><span class="p" data-group-id="5544787080-8">]</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="n">L2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5544787080-10">[</span><span class="ss">d</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5544787080-10">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5544787080-11">[</span><span class="ss">d</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="5544787080-12">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5544787080-12">}</span><span class="p" data-group-id="5544787080-11">]</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nf">length</span><span class="p" data-group-id="5544787080-13">(</span><span class="n">L1</span><span class="p" data-group-id="5544787080-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0170406268-8">[</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="0170406268-9">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0170406268-9">}</span><span class="p" data-group-id="0170406268-8">]</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="n">L2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0170406268-10">[</span><span class="ss">d</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0170406268-10">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0170406268-11">[</span><span class="ss">d</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="0170406268-12">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0170406268-12">}</span><span class="p" data-group-id="0170406268-11">]</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nf">length</span><span class="p" data-group-id="0170406268-13">(</span><span class="n">L1</span><span class="p" data-group-id="0170406268-13">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">7&gt; </span><span class="nf">length</span><span class="p" data-group-id="5544787080-14">(</span><span class="p" data-group-id="5544787080-15">[</span><span class="p" data-group-id="5544787080-15">]</span><span class="p" data-group-id="5544787080-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">7&gt; </span><span class="nf">length</span><span class="p" data-group-id="0170406268-14">(</span><span class="p" data-group-id="0170406268-15">[</span><span class="p" data-group-id="0170406268-15">]</span><span class="p" data-group-id="0170406268-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">0</span></code></pre><p>A collection of list-processing functions can be found in the module
│ │ │ │  <a href="../../../lib/stdlib/doc/html/lists.html"><code class="inline">lists</code></a> in STDLIB.</p><h2 id="string" class="section-heading">
│ │ │ │    <a href="#string" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">String</span>
│ │ │ │  </h2>
│ │ │ │ @@ -419,64 +419,64 @@
│ │ │ │    <span class="text">Record</span>
│ │ │ │  </h2>
│ │ │ │  <p>A record is a data structure for storing a fixed number of elements. It has
│ │ │ │  named fields and is similar to a struct in C. However, a record is not a true
│ │ │ │  data type. Instead, record expressions are translated to tuple expressions
│ │ │ │  during compilation. Therefore, record expressions are not understood by the
│ │ │ │  shell unless special actions are taken. For details, see module <a href="../../../lib/stdlib/doc/html/shell.html"><code class="inline">shell</code></a>
│ │ │ │ -in STDLIB.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4886197772-1">(</span><span class="ss">person</span><span class="p" data-group-id="4886197772-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4886197772-2">(</span><span class="p" data-group-id="4886197772-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4886197772-3">]</span><span class="p" data-group-id="4886197772-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +in STDLIB.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9091286953-1">(</span><span class="ss">person</span><span class="p" data-group-id="9091286953-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9091286953-2">(</span><span class="p" data-group-id="9091286953-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9091286953-3">]</span><span class="p" data-group-id="9091286953-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4886197772-4">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4886197772-5">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="4886197772-5">}</span><span class="p" data-group-id="4886197772-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9091286953-4">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9091286953-5">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="9091286953-5">}</span><span class="p" data-group-id="9091286953-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">new</span><span class="p" data-group-id="4886197772-6">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="4886197772-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="4886197772-7">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="o">=</span><span class="n">Age</span><span class="p" data-group-id="4886197772-7">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">new</span><span class="p" data-group-id="9091286953-6">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="9091286953-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9091286953-7">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="o">=</span><span class="n">Age</span><span class="p" data-group-id="9091286953-7">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nc">person</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="4886197772-8">(</span><span class="ss">ernie</span><span class="p">,</span><span class="w"> </span><span class="mi">44</span><span class="p" data-group-id="4886197772-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4886197772-9">{</span><span class="ss">person</span><span class="p">,</span><span class="ss">ernie</span><span class="p">,</span><span class="mi">44</span><span class="p" data-group-id="4886197772-9">}</span></code></pre><p>Read more about records in <a href="ref_man_records.xhtml">Records</a>. More examples are
│ │ │ │ +</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nc">person</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="9091286953-8">(</span><span class="ss">ernie</span><span class="p">,</span><span class="w"> </span><span class="mi">44</span><span class="p" data-group-id="9091286953-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9091286953-9">{</span><span class="ss">person</span><span class="p">,</span><span class="ss">ernie</span><span class="p">,</span><span class="mi">44</span><span class="p" data-group-id="9091286953-9">}</span></code></pre><p>Read more about records in <a href="ref_man_records.xhtml">Records</a>. More examples are
│ │ │ │  found in <a href="../../../lib/../system/doc/html/prog_ex_records.xhtml">Programming Examples</a>.</p><h2 id="native-record" class="section-heading">
│ │ │ │    <a href="#native-record" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Native Record</span>
│ │ │ │  </h2>
│ │ │ │  <p>A native record is a data structure for storing a fixed number
│ │ │ │  of elements. It is similar to the traditional <a href="#record">tuple-based records</a>,
│ │ │ │ -except that it is a true data type.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0819275338-1">(</span><span class="ss">person</span><span class="p" data-group-id="0819275338-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0819275338-2">(</span><span class="p" data-group-id="0819275338-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0819275338-3">]</span><span class="p" data-group-id="0819275338-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +except that it is a true data type.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8089350986-1">(</span><span class="ss">person</span><span class="p" data-group-id="8089350986-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8089350986-2">(</span><span class="p" data-group-id="8089350986-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8089350986-3">]</span><span class="p" data-group-id="8089350986-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="0819275338-4">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="0819275338-4">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8089350986-4">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="8089350986-4">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">new</span><span class="p" data-group-id="0819275338-5">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="0819275338-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="0819275338-6">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="o">=</span><span class="n">Age</span><span class="p" data-group-id="0819275338-6">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">person</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="2852549421-1">(</span><span class="ss">ernie</span><span class="p">,</span><span class="w"> </span><span class="mi">44</span><span class="p" data-group-id="2852549421-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">#</span><span class="nc">person</span><span class="p">:</span><span class="ss">person</span><span class="p" data-group-id="2852549421-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">ernie</span><span class="p">,</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">44</span><span class="p" data-group-id="2852549421-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">is_record</span><span class="p" data-group-id="2852549421-3">(</span><span class="n">P</span><span class="p" data-group-id="2852549421-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">new</span><span class="p" data-group-id="8089350986-5">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="8089350986-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8089350986-6">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="o">=</span><span class="n">Age</span><span class="p" data-group-id="8089350986-6">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">person</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="5920245228-1">(</span><span class="ss">ernie</span><span class="p">,</span><span class="w"> </span><span class="mi">44</span><span class="p" data-group-id="5920245228-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">#</span><span class="nc">person</span><span class="p">:</span><span class="ss">person</span><span class="p" data-group-id="5920245228-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">ernie</span><span class="p">,</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">44</span><span class="p" data-group-id="5920245228-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">is_record</span><span class="p" data-group-id="5920245228-3">(</span><span class="n">P</span><span class="p" data-group-id="5920245228-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="2852549421-4">(</span><span class="n">P</span><span class="p" data-group-id="2852549421-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="5920245228-4">(</span><span class="n">P</span><span class="p" data-group-id="5920245228-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nf">is_map</span><span class="p" data-group-id="2852549421-5">(</span><span class="n">P</span><span class="p" data-group-id="2852549421-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nf">is_map</span><span class="p" data-group-id="5920245228-5">(</span><span class="n">P</span><span class="p" data-group-id="5920245228-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span></code></pre><section role="note" class="admonition warning"><h4 class="admonition-title warning">Warning</h4><p>Native records are considered experimental in Erlang/OTP 29. This
│ │ │ │  means that their behavior may change, potentially requiring updates
│ │ │ │  to applications that use them.</p></section><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Native records were introduced in Erlang/OTP 29.</p></section><h2 id="boolean" class="section-heading">
│ │ │ │    <a href="#boolean" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Boolean</span>
│ │ │ │  </h2>
│ │ │ │  <p>There is no Boolean data type in Erlang. Instead, the atoms <code class="inline">true</code> and <code class="inline">false</code>
│ │ │ │  are used to denote Boolean values. The <a href="../../../lib/../erts/doc/html/erlang.html#is_boolean/1"><code class="inline">is_boolean/1</code></a>
│ │ │ │  BIF tests whether a term is a boolean.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="mi">2</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │  </span><span class="gp unselectable">2&gt; </span><span class="ss">true</span><span class="w"> </span><span class="ow">or</span><span class="w"> </span><span class="ss">false</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="0869552877-1">(</span><span class="ss">true</span><span class="p" data-group-id="0869552877-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="5326788011-1">(</span><span class="ss">true</span><span class="p" data-group-id="5326788011-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="0869552877-2">(</span><span class="ss">false</span><span class="p" data-group-id="0869552877-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="5326788011-2">(</span><span class="ss">false</span><span class="p" data-group-id="5326788011-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="0869552877-3">(</span><span class="ss">ok</span><span class="p" data-group-id="0869552877-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="5326788011-3">(</span><span class="ss">ok</span><span class="p" data-group-id="5326788011-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span></code></pre><h2 id="escape-sequences" class="section-heading">
│ │ │ │    <a href="#escape-sequences" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Escape Sequences</span>
│ │ │ │  </h2>
│ │ │ │  <p>Within strings (<code class="inline">&quot;</code>-delimited), quoted atoms, and the content of
│ │ │ │ @@ -494,44 +494,44 @@
│ │ │ │  <a href="data_types.xhtml#sigil"><code class="inline">~b</code> or <code class="inline">~s</code> sigils</a> the escape sequences for normal
│ │ │ │  strings, above, are used.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Triple-quoted strings and sigils were introduced in Erlang/OTP 27.</p></section><h2 id="type-conversions" class="section-heading">
│ │ │ │    <a href="#type-conversions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Type Conversions</span>
│ │ │ │  </h2>
│ │ │ │ -<p>There are a number of BIFs for type conversions.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="5287120301-1">(</span><span class="ss">hello</span><span class="p" data-group-id="5287120301-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>There are a number of BIFs for type conversions.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="1068752319-1">(</span><span class="ss">hello</span><span class="p" data-group-id="1068752319-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;hello&quot;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="5287120301-2">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="5287120301-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="1068752319-2">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1068752319-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="5287120301-3">(</span><span class="p" data-group-id="5287120301-4">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="5287120301-4">&gt;&gt;</span><span class="p" data-group-id="5287120301-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="1068752319-3">(</span><span class="p" data-group-id="1068752319-4">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1068752319-4">&gt;&gt;</span><span class="p" data-group-id="1068752319-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;hello&quot;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="5287120301-5">(</span><span class="p" data-group-id="5287120301-6">&lt;&lt;</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="5287120301-6">&gt;&gt;</span><span class="p" data-group-id="5287120301-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="1068752319-5">(</span><span class="p" data-group-id="1068752319-6">&lt;&lt;</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="1068752319-6">&gt;&gt;</span><span class="p" data-group-id="1068752319-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;hello&quot;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nf">list_to_binary</span><span class="p" data-group-id="5287120301-7">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="5287120301-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5287120301-8">&lt;&lt;</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="5287120301-8">&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="5287120301-9">(</span><span class="mf">7.0</span><span class="p" data-group-id="5287120301-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nf">list_to_binary</span><span class="p" data-group-id="1068752319-7">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1068752319-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1068752319-8">&lt;&lt;</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="1068752319-8">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="1068752319-9">(</span><span class="mf">7.0</span><span class="p" data-group-id="1068752319-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;7.00000000000000000000e+00&quot;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">7&gt; </span><span class="nf">list_to_float</span><span class="p" data-group-id="5287120301-10">(</span><span class="s">&quot;7.000e+00&quot;</span><span class="p" data-group-id="5287120301-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">7&gt; </span><span class="nf">list_to_float</span><span class="p" data-group-id="1068752319-10">(</span><span class="s">&quot;7.000e+00&quot;</span><span class="p" data-group-id="1068752319-10">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mf">7.0</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">8&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="5287120301-11">(</span><span class="mi">77</span><span class="p" data-group-id="5287120301-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">8&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="1068752319-11">(</span><span class="mi">77</span><span class="p" data-group-id="1068752319-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;77&quot;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">9&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="5287120301-12">(</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="5287120301-12">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">9&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="1068752319-12">(</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="1068752319-12">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">77</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">10&gt; </span><span class="nf">tuple_to_list</span><span class="p" data-group-id="5287120301-13">(</span><span class="p" data-group-id="5287120301-14">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5287120301-14">}</span><span class="p" data-group-id="5287120301-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5287120301-15">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5287120301-15">]</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">11&gt; </span><span class="nf">list_to_tuple</span><span class="p" data-group-id="5287120301-16">(</span><span class="p" data-group-id="5287120301-17">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5287120301-17">]</span><span class="p" data-group-id="5287120301-16">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5287120301-18">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5287120301-18">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">12&gt; </span><span class="nf">term_to_binary</span><span class="p" data-group-id="5287120301-19">(</span><span class="p" data-group-id="5287120301-20">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5287120301-20">}</span><span class="p" data-group-id="5287120301-19">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5287120301-21">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">97</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="5287120301-21">&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">13&gt; </span><span class="nf">binary_to_term</span><span class="p" data-group-id="5287120301-22">(</span><span class="p" data-group-id="5287120301-23">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">97</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="5287120301-23">&gt;&gt;</span><span class="p" data-group-id="5287120301-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5287120301-24">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5287120301-24">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">14&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="5287120301-25">(</span><span class="p" data-group-id="5287120301-26">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="5287120301-26">&gt;&gt;</span><span class="p" data-group-id="5287120301-25">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">10&gt; </span><span class="nf">tuple_to_list</span><span class="p" data-group-id="1068752319-13">(</span><span class="p" data-group-id="1068752319-14">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1068752319-14">}</span><span class="p" data-group-id="1068752319-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1068752319-15">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1068752319-15">]</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">11&gt; </span><span class="nf">list_to_tuple</span><span class="p" data-group-id="1068752319-16">(</span><span class="p" data-group-id="1068752319-17">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1068752319-17">]</span><span class="p" data-group-id="1068752319-16">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1068752319-18">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1068752319-18">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">12&gt; </span><span class="nf">term_to_binary</span><span class="p" data-group-id="1068752319-19">(</span><span class="p" data-group-id="1068752319-20">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1068752319-20">}</span><span class="p" data-group-id="1068752319-19">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1068752319-21">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">97</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="1068752319-21">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">13&gt; </span><span class="nf">binary_to_term</span><span class="p" data-group-id="1068752319-22">(</span><span class="p" data-group-id="1068752319-23">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">97</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="1068752319-23">&gt;&gt;</span><span class="p" data-group-id="1068752319-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1068752319-24">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1068752319-24">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">14&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="1068752319-25">(</span><span class="p" data-group-id="1068752319-26">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="1068752319-26">&gt;&gt;</span><span class="p" data-group-id="1068752319-25">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">77</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">15&gt; </span><span class="nf">integer_to_binary</span><span class="p" data-group-id="5287120301-27">(</span><span class="mi">77</span><span class="p" data-group-id="5287120301-27">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5287120301-28">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="5287120301-28">&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">16&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="5287120301-29">(</span><span class="mf">7.0</span><span class="p" data-group-id="5287120301-29">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5287120301-30">&lt;&lt;</span><span class="s">&quot;7.00000000000000000000e+00&quot;</span><span class="p" data-group-id="5287120301-30">&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">17&gt; </span><span class="nf">binary_to_float</span><span class="p" data-group-id="5287120301-31">(</span><span class="p" data-group-id="5287120301-32">&lt;&lt;</span><span class="s">&quot;7.000e+00&quot;</span><span class="p" data-group-id="5287120301-32">&gt;&gt;</span><span class="p" data-group-id="5287120301-31">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">15&gt; </span><span class="nf">integer_to_binary</span><span class="p" data-group-id="1068752319-27">(</span><span class="mi">77</span><span class="p" data-group-id="1068752319-27">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1068752319-28">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="1068752319-28">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">16&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="1068752319-29">(</span><span class="mf">7.0</span><span class="p" data-group-id="1068752319-29">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1068752319-30">&lt;&lt;</span><span class="s">&quot;7.00000000000000000000e+00&quot;</span><span class="p" data-group-id="1068752319-30">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">17&gt; </span><span class="nf">binary_to_float</span><span class="p" data-group-id="1068752319-31">(</span><span class="p" data-group-id="1068752319-32">&lt;&lt;</span><span class="s">&quot;7.000e+00&quot;</span><span class="p" data-group-id="1068752319-32">&gt;&gt;</span><span class="p" data-group-id="1068752319-31">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mf">7.0</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/create_target.xhtml
│ │ │ │ @@ -43,21 +43,21 @@
│ │ │ │    <span class="text">Creating a Target System</span>
│ │ │ │  </h2>
│ │ │ │  <p>It is assumed that you have a working Erlang/OTP system structured according to
│ │ │ │  the OTP design principles.</p><p><em>Step 1.</em> Create a <code class="inline">.rel</code> file (see the <a href="../../../lib/sasl/doc/html/rel.xhtml">rel(4)</a> manual page in
│ │ │ │  SASL), which specifies the ERTS version and lists all applications that are to
│ │ │ │  be included in the new basic target system. An example is the following
│ │ │ │  <code class="inline">mysystem.rel</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% mysystem.rel</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4679497971-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4679497971-2">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;FIRST&quot;</span><span class="p" data-group-id="4679497971-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4679497971-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.10.4&quot;</span><span class="p" data-group-id="4679497971-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4679497971-4">[</span><span class="p" data-group-id="4679497971-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.16.4&quot;</span><span class="p" data-group-id="4679497971-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="4679497971-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1.19.4&quot;</span><span class="p" data-group-id="4679497971-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="4679497971-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.3.4&quot;</span><span class="p" data-group-id="4679497971-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="4679497971-8">{</span><span class="ss">pea</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="4679497971-8">}</span><span class="p" data-group-id="4679497971-4">]</span><span class="p" data-group-id="4679497971-1">}</span><span class="p">.</span></code></pre><p>The listed applications are not only original Erlang/OTP applications but
│ │ │ │ +</span><span class="p" data-group-id="6322345271-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6322345271-2">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;FIRST&quot;</span><span class="p" data-group-id="6322345271-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6322345271-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.10.4&quot;</span><span class="p" data-group-id="6322345271-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6322345271-4">[</span><span class="p" data-group-id="6322345271-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.16.4&quot;</span><span class="p" data-group-id="6322345271-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6322345271-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1.19.4&quot;</span><span class="p" data-group-id="6322345271-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6322345271-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.3.4&quot;</span><span class="p" data-group-id="6322345271-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6322345271-8">{</span><span class="ss">pea</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="6322345271-8">}</span><span class="p" data-group-id="6322345271-4">]</span><span class="p" data-group-id="6322345271-1">}</span><span class="p">.</span></code></pre><p>The listed applications are not only original Erlang/OTP applications but
│ │ │ │  possibly also new applications that you have written (here exemplified by the
│ │ │ │  application Pea (<code class="inline">pea</code>)).</p><p><em>Step 2.</em> Start Erlang/OTP from the directory where the <code class="inline">mysystem.rel</code> file
│ │ │ │  resides:</p><pre><code class="text">% erl -pa /home/user/target_system/myapps/pea-1.0/ebin</code></pre><p>The <code class="inline">-pa</code> argument prepends the path to the <code class="inline">ebin</code> directory for
│ │ │ │  the Pea application to the code path.</p><p><em>Step 3.</em> Create the target system:</p><pre><code class="text">1&gt; target_system:create(&quot;mysystem&quot;).</code></pre><p>The function <code class="inline">target_system:create/1</code> performs the following:</p><ol><li><p>Reads the file <code class="inline">mysystem.rel</code> and creates a new file <code class="inline">plain.rel</code>.
│ │ │ │  The new file is identical to the original, except that it only
│ │ │ │  lists the Kernel and STDLIB applications.</p></li><li><p>From the files <code class="inline">mysystem.rel</code> and <code class="inline">plain.rel</code> creates the files
│ │ │ │  <code class="inline">mysystem.script</code>, <code class="inline">mysystem.boot</code>, <code class="inline">plain.script</code>, and <code class="inline">plain.boot</code>
│ │ │ │ @@ -147,25 +147,25 @@
│ │ │ │    <a href="#creating-the-next-version" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Creating the Next Version</span>
│ │ │ │  </h2>
│ │ │ │  <p>In this example the Pea application has been changed, and so have the
│ │ │ │  applications ERTS, Kernel, STDLIB and SASL.</p><p><em>Step 1.</em> Create the file <code class="inline">.rel</code>:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% mysystem2.rel</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6034629672-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="6034629672-2">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;SECOND&quot;</span><span class="p" data-group-id="6034629672-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="6034629672-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;6.0&quot;</span><span class="p" data-group-id="6034629672-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="6034629672-4">[</span><span class="p" data-group-id="6034629672-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;3.0&quot;</span><span class="p" data-group-id="6034629672-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6034629672-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="6034629672-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6034629672-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.4&quot;</span><span class="p" data-group-id="6034629672-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6034629672-8">{</span><span class="ss">pea</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="6034629672-8">}</span><span class="p" data-group-id="6034629672-4">]</span><span class="p" data-group-id="6034629672-1">}</span><span class="p">.</span></code></pre><p><em>Step 2.</em> Create the application upgrade file (see
│ │ │ │ +</span><span class="p" data-group-id="5755176471-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5755176471-2">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;SECOND&quot;</span><span class="p" data-group-id="5755176471-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5755176471-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;6.0&quot;</span><span class="p" data-group-id="5755176471-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5755176471-4">[</span><span class="p" data-group-id="5755176471-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;3.0&quot;</span><span class="p" data-group-id="5755176471-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="5755176471-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="5755176471-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="5755176471-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.4&quot;</span><span class="p" data-group-id="5755176471-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="5755176471-8">{</span><span class="ss">pea</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="5755176471-8">}</span><span class="p" data-group-id="5755176471-4">]</span><span class="p" data-group-id="5755176471-1">}</span><span class="p">.</span></code></pre><p><em>Step 2.</em> Create the application upgrade file (see
│ │ │ │  <a href="../../../lib/sasl/doc/html/appup.xhtml">appup</a> in SASL) for Pea, for example:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% pea.appup</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1593790980-1">{</span><span class="s">&quot;2.0&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1593790980-2">[</span><span class="p" data-group-id="1593790980-3">{</span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="p" data-group-id="1593790980-4">[</span><span class="p" data-group-id="1593790980-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="ss">pea_lib</span><span class="p" data-group-id="1593790980-5">}</span><span class="p" data-group-id="1593790980-4">]</span><span class="p" data-group-id="1593790980-3">}</span><span class="p" data-group-id="1593790980-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1593790980-6">[</span><span class="p" data-group-id="1593790980-7">{</span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="p" data-group-id="1593790980-8">[</span><span class="p" data-group-id="1593790980-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="ss">pea_lib</span><span class="p" data-group-id="1593790980-9">}</span><span class="p" data-group-id="1593790980-8">]</span><span class="p" data-group-id="1593790980-7">}</span><span class="p" data-group-id="1593790980-6">]</span><span class="p" data-group-id="1593790980-1">}</span><span class="p">.</span></code></pre><p><em>Step 3.</em> From the directory where the file <code class="inline">mysystem2.rel</code> resides, start the
│ │ │ │ +</span><span class="p" data-group-id="7909248493-1">{</span><span class="s">&quot;2.0&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7909248493-2">[</span><span class="p" data-group-id="7909248493-3">{</span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="p" data-group-id="7909248493-4">[</span><span class="p" data-group-id="7909248493-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="ss">pea_lib</span><span class="p" data-group-id="7909248493-5">}</span><span class="p" data-group-id="7909248493-4">]</span><span class="p" data-group-id="7909248493-3">}</span><span class="p" data-group-id="7909248493-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7909248493-6">[</span><span class="p" data-group-id="7909248493-7">{</span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="p" data-group-id="7909248493-8">[</span><span class="p" data-group-id="7909248493-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="ss">pea_lib</span><span class="p" data-group-id="7909248493-9">}</span><span class="p" data-group-id="7909248493-8">]</span><span class="p" data-group-id="7909248493-7">}</span><span class="p" data-group-id="7909248493-6">]</span><span class="p" data-group-id="7909248493-1">}</span><span class="p">.</span></code></pre><p><em>Step 3.</em> From the directory where the file <code class="inline">mysystem2.rel</code> resides, start the
│ │ │ │  Erlang/OTP system, giving the path to the new version of Pea:</p><pre><code class="text">% erl -pa /home/user/target_system/myapps/pea-2.0/ebin</code></pre><p><em>Step 4.</em> Create the release upgrade file (see <a href="../../../lib/sasl/doc/html/relup.xhtml">relup</a>
│ │ │ │  in SASL):</p><pre><code class="text">1&gt; systools:make_relup(&quot;mysystem2&quot;,[&quot;mysystem&quot;],[&quot;mysystem&quot;],
│ │ │ │      [{path,[&quot;/home/user/target_system/myapps/pea-1.0/ebin&quot;,
│ │ │ │      &quot;/my/old/erlang/lib/*/ebin&quot;]}]).</code></pre><p>Here <code class="inline">&quot;mysystem&quot;</code> is the base release and <code class="inline">&quot;mysystem2&quot;</code> is the release to
│ │ │ │  upgrade to.</p><p>The <code class="inline">path</code> option is used for pointing out the old version of all applications.
│ │ │ │  (The new versions are already in the code path - assuming of course that the
│ │ │ │  Erlang node on which this is executed is running the correct version of
│ │ │ │ @@ -197,287 +197,287 @@
│ │ │ │  {continue_after_restart,&quot;FIRST&quot;,[]}
│ │ │ │  heart: Tue Apr  1 12:15:10 2014: Erlang has closed.
│ │ │ │  heart: Tue Apr  1 12:15:11 2014: Executed &quot;/usr/local/erl-target/bin/start /usr/local/erl-target/releases/new_start_erl.data&quot; -&gt; 0. Terminating.
│ │ │ │  [End]</code></pre><p>The above return value and output after the call to
│ │ │ │  <a href="../../../lib/sasl/doc/html/release_handler.html#install_release/1"><code class="inline">release_handler:install_release/1</code></a> means that the <code class="inline">release_handler</code> has
│ │ │ │  restarted the node by using <code class="inline">heart</code>. This is always done when the upgrade
│ │ │ │  involves a change of the applications ERTS, Kernel, STDLIB, or SASL. For more
│ │ │ │ -information, see <a href="upgrade.xhtml">Upgrade when Erlang/OTP has Changed</a>.</p><p>The node is accessible through a new pipe:</p><pre><code class="text">% /usr/local/erl-target/bin/to_erl /tmp/erlang.pipe.2</code></pre><p>List the available releases in the system:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">which_releases</span><span class="p" data-group-id="9430546316-1">(</span><span class="p" data-group-id="9430546316-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9430546316-2">[</span><span class="p" data-group-id="9430546316-3">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;SECOND&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="9430546316-4">[</span><span class="s">&quot;kernel-3.0&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-2.0&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-2.0&quot;</span><span class="p" data-group-id="9430546316-4">]</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">current</span><span class="p" data-group-id="9430546316-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9430546316-5">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;FIRST&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="9430546316-6">[</span><span class="s">&quot;kernel-2.16.4&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-1.19.4&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.3.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-1.0&quot;</span><span class="p" data-group-id="9430546316-6">]</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">permanent</span><span class="p" data-group-id="9430546316-5">}</span><span class="p" data-group-id="9430546316-2">]</span></code></pre><p>Our new release, &quot;SECOND&quot;, is now the current release, but we can also see that
│ │ │ │ +information, see <a href="upgrade.xhtml">Upgrade when Erlang/OTP has Changed</a>.</p><p>The node is accessible through a new pipe:</p><pre><code class="text">% /usr/local/erl-target/bin/to_erl /tmp/erlang.pipe.2</code></pre><p>List the available releases in the system:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">which_releases</span><span class="p" data-group-id="8271875402-1">(</span><span class="p" data-group-id="8271875402-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8271875402-2">[</span><span class="p" data-group-id="8271875402-3">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;SECOND&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8271875402-4">[</span><span class="s">&quot;kernel-3.0&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-2.0&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-2.0&quot;</span><span class="p" data-group-id="8271875402-4">]</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="ss">current</span><span class="p" data-group-id="8271875402-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8271875402-5">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;FIRST&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8271875402-6">[</span><span class="s">&quot;kernel-2.16.4&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-1.19.4&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.3.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-1.0&quot;</span><span class="p" data-group-id="8271875402-6">]</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="ss">permanent</span><span class="p" data-group-id="8271875402-5">}</span><span class="p" data-group-id="8271875402-2">]</span></code></pre><p>Our new release, &quot;SECOND&quot;, is now the current release, but we can also see that
│ │ │ │  our &quot;FIRST&quot; release is still permanent. This means that if the node would be
│ │ │ │ -restarted now, it would come up running the &quot;FIRST&quot; release again.</p><p><em>Step 3.</em> Make the new release permanent:</p><pre><code class="text">2&gt; release_handler:make_permanent(&quot;SECOND&quot;).</code></pre><p>Check the releases again:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">which_releases</span><span class="p" data-group-id="8749950246-1">(</span><span class="p" data-group-id="8749950246-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8749950246-2">[</span><span class="p" data-group-id="8749950246-3">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;SECOND&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="8749950246-4">[</span><span class="s">&quot;kernel-3.0&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-2.0&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-2.0&quot;</span><span class="p" data-group-id="8749950246-4">]</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">permanent</span><span class="p" data-group-id="8749950246-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="8749950246-5">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;FIRST&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="8749950246-6">[</span><span class="s">&quot;kernel-2.16.4&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-1.19.4&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.3.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-1.0&quot;</span><span class="p" data-group-id="8749950246-6">]</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">old</span><span class="p" data-group-id="8749950246-5">}</span><span class="p" data-group-id="8749950246-2">]</span></code></pre><p>We see that the new release version is <code class="inline">permanent</code>, so it would be safe to
│ │ │ │ +restarted now, it would come up running the &quot;FIRST&quot; release again.</p><p><em>Step 3.</em> Make the new release permanent:</p><pre><code class="text">2&gt; release_handler:make_permanent(&quot;SECOND&quot;).</code></pre><p>Check the releases again:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">which_releases</span><span class="p" data-group-id="3476977046-1">(</span><span class="p" data-group-id="3476977046-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3476977046-2">[</span><span class="p" data-group-id="3476977046-3">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;SECOND&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="3476977046-4">[</span><span class="s">&quot;kernel-3.0&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-2.0&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-2.0&quot;</span><span class="p" data-group-id="3476977046-4">]</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="ss">permanent</span><span class="p" data-group-id="3476977046-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="3476977046-5">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;FIRST&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="3476977046-6">[</span><span class="s">&quot;kernel-2.16.4&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-1.19.4&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.3.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-1.0&quot;</span><span class="p" data-group-id="3476977046-6">]</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="ss">old</span><span class="p" data-group-id="3476977046-5">}</span><span class="p" data-group-id="3476977046-2">]</span></code></pre><p>We see that the new release version is <code class="inline">permanent</code>, so it would be safe to
│ │ │ │  restart the node.</p><p><a href="" id="listing-of-target-system"></a></p><h2 id="listing-of-target_system-erl" class="section-heading">
│ │ │ │    <a href="#listing-of-target_system-erl" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Listing of target_system.erl</span>
│ │ │ │  </h2>
│ │ │ │  <p>This module can also be found in the <code class="inline">examples</code> directory of the SASL
│ │ │ │  application.</p><pre><code class="makeup erlang" translate="no"><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7066557652-1">(</span><span class="ss">target_system</span><span class="p" data-group-id="7066557652-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7066557652-2">(</span><span class="p" data-group-id="7066557652-3">[</span><span class="ss">create</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">create</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">install</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7066557652-3">]</span><span class="p" data-group-id="7066557652-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4940317009-1">(</span><span class="ss">target_system</span><span class="p" data-group-id="4940317009-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4940317009-2">(</span><span class="p" data-group-id="4940317009-3">[</span><span class="ss">create</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">create</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">install</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4940317009-3">]</span><span class="p" data-group-id="4940317009-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% Note: RelFileName below is the *stem* without trailing .rel,</span><span class="w">
│ │ │ │  </span><span class="c1">%% .script etc.</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% create(RelFileName)</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │ -</span><span class="nf">create</span><span class="p" data-group-id="7066557652-4">(</span><span class="n">RelFileName</span><span class="p" data-group-id="7066557652-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">create</span><span class="p" data-group-id="7066557652-5">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="p" data-group-id="7066557652-6">[</span><span class="p" data-group-id="7066557652-6">]</span><span class="p" data-group-id="7066557652-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">create</span><span class="p" data-group-id="4940317009-4">(</span><span class="n">RelFileName</span><span class="p" data-group-id="4940317009-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">create</span><span class="p" data-group-id="4940317009-5">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="p" data-group-id="4940317009-6">[</span><span class="p" data-group-id="4940317009-6">]</span><span class="p" data-group-id="4940317009-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">create</span><span class="p" data-group-id="7066557652-7">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="7066557652-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">create</span><span class="p" data-group-id="4940317009-7">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="4940317009-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">RelFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.rel&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Dir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="7066557652-8">(</span><span class="n">RelFileName</span><span class="p" data-group-id="7066557652-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">PlainRelFileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-9">(</span><span class="n">Dir</span><span class="p">,</span><span class="s">&quot;plain&quot;</span><span class="p" data-group-id="7066557652-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Dir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="4940317009-8">(</span><span class="n">RelFileName</span><span class="p" data-group-id="4940317009-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">PlainRelFileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-9">(</span><span class="n">Dir</span><span class="p">,</span><span class="s">&quot;plain&quot;</span><span class="p" data-group-id="4940317009-9">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="n">PlainRelFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">PlainRelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.rel&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-10">(</span><span class="s">&quot;Reading file: ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-11">[</span><span class="n">RelFile</span><span class="p" data-group-id="7066557652-11">]</span><span class="p" data-group-id="7066557652-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7066557652-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-13">[</span><span class="n">RelSpec</span><span class="p" data-group-id="7066557652-13">]</span><span class="p" data-group-id="7066557652-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">consult</span><span class="p" data-group-id="7066557652-14">(</span><span class="n">RelFile</span><span class="p" data-group-id="7066557652-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-15">(</span><span class="s">&quot;Creating file: ~ts from ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="7066557652-16">[</span><span class="n">PlainRelFile</span><span class="p">,</span><span class="w"> </span><span class="n">RelFile</span><span class="p" data-group-id="7066557652-16">]</span><span class="p" data-group-id="7066557652-15">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7066557652-17">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="7066557652-18">{</span><span class="n">RelName</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="7066557652-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="7066557652-19">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p" data-group-id="7066557652-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="n">AppVsns</span><span class="p" data-group-id="7066557652-17">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelSpec</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">PlainRelSpec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7066557652-20">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="p" data-group-id="7066557652-21">{</span><span class="n">RelName</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="7066557652-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="p" data-group-id="7066557652-22">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p" data-group-id="7066557652-22">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="7066557652-23">(</span><span class="nf">fun</span><span class="p" data-group-id="7066557652-24">(</span><span class="p" data-group-id="7066557652-25">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7066557652-25">}</span><span class="p" data-group-id="7066557652-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-10">(</span><span class="s">&quot;Reading file: ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-11">[</span><span class="n">RelFile</span><span class="p" data-group-id="4940317009-11">]</span><span class="p" data-group-id="4940317009-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4940317009-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-13">[</span><span class="n">RelSpec</span><span class="p" data-group-id="4940317009-13">]</span><span class="p" data-group-id="4940317009-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">consult</span><span class="p" data-group-id="4940317009-14">(</span><span class="n">RelFile</span><span class="p" data-group-id="4940317009-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-15">(</span><span class="s">&quot;Creating file: ~ts from ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="4940317009-16">[</span><span class="n">PlainRelFile</span><span class="p">,</span><span class="w"> </span><span class="n">RelFile</span><span class="p" data-group-id="4940317009-16">]</span><span class="p" data-group-id="4940317009-15">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4940317009-17">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="4940317009-18">{</span><span class="n">RelName</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="4940317009-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="4940317009-19">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p" data-group-id="4940317009-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="n">AppVsns</span><span class="p" data-group-id="4940317009-17">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelSpec</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">PlainRelSpec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4940317009-20">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="p" data-group-id="4940317009-21">{</span><span class="n">RelName</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="4940317009-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="p" data-group-id="4940317009-22">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p" data-group-id="4940317009-22">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="4940317009-23">(</span><span class="nf">fun</span><span class="p" data-group-id="4940317009-24">(</span><span class="p" data-group-id="4940317009-25">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="4940317009-25">}</span><span class="p" data-group-id="4940317009-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                                           </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ │ -                                    </span><span class="p" data-group-id="7066557652-26">(</span><span class="p" data-group-id="7066557652-27">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7066557652-27">}</span><span class="p" data-group-id="7066557652-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                                    </span><span class="p" data-group-id="4940317009-26">(</span><span class="p" data-group-id="4940317009-27">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="4940317009-27">}</span><span class="p" data-group-id="4940317009-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                                           </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ │ -                                    </span><span class="p" data-group-id="7066557652-28">(</span><span class="p">_</span><span class="p" data-group-id="7066557652-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                                    </span><span class="p" data-group-id="4940317009-28">(</span><span class="p">_</span><span class="p" data-group-id="4940317009-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                                           </span><span class="ss">false</span><span class="w">
│ │ │ │ -                                 </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsns</span><span class="p" data-group-id="7066557652-23">)</span><span class="w">
│ │ │ │ -                   </span><span class="p" data-group-id="7066557652-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7066557652-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7066557652-29">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="7066557652-30">(</span><span class="n">PlainRelFile</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-31">[</span><span class="ss">write</span><span class="p" data-group-id="7066557652-31">]</span><span class="p" data-group-id="7066557652-30">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-32">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s">.</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-33">[</span><span class="n">PlainRelSpec</span><span class="p" data-group-id="7066557652-33">]</span><span class="p" data-group-id="7066557652-32">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="7066557652-34">(</span><span class="n">Fd</span><span class="p" data-group-id="7066557652-34">)</span><span class="p">,</span><span class="w">
│ │ │ │ -
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-35">(</span><span class="s">&quot;Making \&quot;~ts.script\&quot; and \&quot;~ts.boot\&quot; files ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -	      </span><span class="p" data-group-id="7066557652-36">[</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="n">PlainRelFileName</span><span class="p" data-group-id="7066557652-36">]</span><span class="p" data-group-id="7066557652-35">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">make_script</span><span class="p" data-group-id="7066557652-37">(</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="7066557652-37">)</span><span class="p">,</span><span class="w">
│ │ │ │ -
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-38">(</span><span class="s">&quot;Making \&quot;~ts.script\&quot; and \&quot;~ts.boot\&quot; files ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="7066557652-39">[</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="p" data-group-id="7066557652-39">]</span><span class="p" data-group-id="7066557652-38">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">make_script</span><span class="p" data-group-id="7066557652-40">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="7066557652-40">)</span><span class="p">,</span><span class="w">
│ │ │ │ +                                 </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsns</span><span class="p" data-group-id="4940317009-23">)</span><span class="w">
│ │ │ │ +                   </span><span class="p" data-group-id="4940317009-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4940317009-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="4940317009-29">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="4940317009-30">(</span><span class="n">PlainRelFile</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-31">[</span><span class="ss">write</span><span class="p" data-group-id="4940317009-31">]</span><span class="p" data-group-id="4940317009-30">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-32">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s">.</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-33">[</span><span class="n">PlainRelSpec</span><span class="p" data-group-id="4940317009-33">]</span><span class="p" data-group-id="4940317009-32">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="4940317009-34">(</span><span class="n">Fd</span><span class="p" data-group-id="4940317009-34">)</span><span class="p">,</span><span class="w">
│ │ │ │ +
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-35">(</span><span class="s">&quot;Making \&quot;~ts.script\&quot; and \&quot;~ts.boot\&quot; files ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +	      </span><span class="p" data-group-id="4940317009-36">[</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="n">PlainRelFileName</span><span class="p" data-group-id="4940317009-36">]</span><span class="p" data-group-id="4940317009-35">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">make_script</span><span class="p" data-group-id="4940317009-37">(</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="4940317009-37">)</span><span class="p">,</span><span class="w">
│ │ │ │ +
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-38">(</span><span class="s">&quot;Making \&quot;~ts.script\&quot; and \&quot;~ts.boot\&quot; files ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="4940317009-39">[</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="p" data-group-id="4940317009-39">]</span><span class="p" data-group-id="4940317009-38">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">make_script</span><span class="p" data-group-id="4940317009-40">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="4940317009-40">)</span><span class="p">,</span><span class="w">
│ │ │ │  
│ │ │ │      </span><span class="n">TarFileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.tar.gz&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-41">(</span><span class="s">&quot;Creating tar file ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-42">[</span><span class="n">TarFileName</span><span class="p" data-group-id="7066557652-42">]</span><span class="p" data-group-id="7066557652-41">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">make_tar</span><span class="p" data-group-id="7066557652-43">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="7066557652-43">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-41">(</span><span class="s">&quot;Creating tar file ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-42">[</span><span class="n">TarFileName</span><span class="p" data-group-id="4940317009-42">]</span><span class="p" data-group-id="4940317009-41">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">make_tar</span><span class="p" data-group-id="4940317009-43">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="4940317009-43">)</span><span class="p">,</span><span class="w">
│ │ │ │  
│ │ │ │ -    </span><span class="n">TmpDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-44">(</span><span class="n">Dir</span><span class="p">,</span><span class="s">&quot;tmp&quot;</span><span class="p" data-group-id="7066557652-44">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-45">(</span><span class="s">&quot;Creating directory ~tp ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="7066557652-46">[</span><span class="n">TmpDir</span><span class="p" data-group-id="7066557652-46">]</span><span class="p" data-group-id="7066557652-45">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="7066557652-47">(</span><span class="n">TmpDir</span><span class="p" data-group-id="7066557652-47">)</span><span class="p">,</span><span class="w">
│ │ │ │ -
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-48">(</span><span class="s">&quot;Extracting ~ts into directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-49">[</span><span class="n">TarFileName</span><span class="p">,</span><span class="n">TmpDir</span><span class="p" data-group-id="7066557652-49">]</span><span class="p" data-group-id="7066557652-48">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">extract_tar</span><span class="p" data-group-id="7066557652-50">(</span><span class="n">TarFileName</span><span class="p">,</span><span class="w"> </span><span class="n">TmpDir</span><span class="p" data-group-id="7066557652-50">)</span><span class="p">,</span><span class="w">
│ │ │ │ -
│ │ │ │ -    </span><span class="n">TmpBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-51">(</span><span class="p" data-group-id="7066557652-52">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="7066557652-52">]</span><span class="p" data-group-id="7066557652-51">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">ErtsBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-53">(</span><span class="p" data-group-id="7066557652-54">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="7066557652-54">]</span><span class="p" data-group-id="7066557652-53">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-55">(</span><span class="s">&quot;Deleting \&quot;erl\&quot; and \&quot;start\&quot; in directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="7066557652-56">[</span><span class="n">ErtsBinDir</span><span class="p" data-group-id="7066557652-56">]</span><span class="p" data-group-id="7066557652-55">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="7066557652-57">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-58">(</span><span class="p" data-group-id="7066557652-59">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erl&quot;</span><span class="p" data-group-id="7066557652-59">]</span><span class="p" data-group-id="7066557652-58">)</span><span class="p" data-group-id="7066557652-57">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="7066557652-60">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-61">(</span><span class="p" data-group-id="7066557652-62">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start&quot;</span><span class="p" data-group-id="7066557652-62">]</span><span class="p" data-group-id="7066557652-61">)</span><span class="p" data-group-id="7066557652-60">)</span><span class="p">,</span><span class="w">
│ │ │ │ -
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-63">(</span><span class="s">&quot;Creating temporary directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-64">[</span><span class="n">TmpBinDir</span><span class="p" data-group-id="7066557652-64">]</span><span class="p" data-group-id="7066557652-63">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="7066557652-65">(</span><span class="n">TmpBinDir</span><span class="p" data-group-id="7066557652-65">)</span><span class="p">,</span><span class="w">
│ │ │ │ -
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-66">(</span><span class="s">&quot;Copying file \&quot;~ts.boot\&quot; to ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="7066557652-67">[</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-68">(</span><span class="p" data-group-id="7066557652-69">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start.boot&quot;</span><span class="p" data-group-id="7066557652-69">]</span><span class="p" data-group-id="7066557652-68">)</span><span class="p" data-group-id="7066557652-67">]</span><span class="p" data-group-id="7066557652-66">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="7066557652-70">(</span><span class="n">PlainRelFileName</span><span class="o">++</span><span class="s">&quot;.boot&quot;</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-71">(</span><span class="p" data-group-id="7066557652-72">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start.boot&quot;</span><span class="p" data-group-id="7066557652-72">]</span><span class="p" data-group-id="7066557652-71">)</span><span class="p" data-group-id="7066557652-70">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">TmpDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-44">(</span><span class="n">Dir</span><span class="p">,</span><span class="s">&quot;tmp&quot;</span><span class="p" data-group-id="4940317009-44">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-45">(</span><span class="s">&quot;Creating directory ~tp ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="4940317009-46">[</span><span class="n">TmpDir</span><span class="p" data-group-id="4940317009-46">]</span><span class="p" data-group-id="4940317009-45">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="4940317009-47">(</span><span class="n">TmpDir</span><span class="p" data-group-id="4940317009-47">)</span><span class="p">,</span><span class="w">
│ │ │ │ +
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-48">(</span><span class="s">&quot;Extracting ~ts into directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-49">[</span><span class="n">TarFileName</span><span class="p">,</span><span class="n">TmpDir</span><span class="p" data-group-id="4940317009-49">]</span><span class="p" data-group-id="4940317009-48">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">extract_tar</span><span class="p" data-group-id="4940317009-50">(</span><span class="n">TarFileName</span><span class="p">,</span><span class="w"> </span><span class="n">TmpDir</span><span class="p" data-group-id="4940317009-50">)</span><span class="p">,</span><span class="w">
│ │ │ │ +
│ │ │ │ +    </span><span class="n">TmpBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-51">(</span><span class="p" data-group-id="4940317009-52">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="4940317009-52">]</span><span class="p" data-group-id="4940317009-51">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">ErtsBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-53">(</span><span class="p" data-group-id="4940317009-54">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="4940317009-54">]</span><span class="p" data-group-id="4940317009-53">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-55">(</span><span class="s">&quot;Deleting \&quot;erl\&quot; and \&quot;start\&quot; in directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="4940317009-56">[</span><span class="n">ErtsBinDir</span><span class="p" data-group-id="4940317009-56">]</span><span class="p" data-group-id="4940317009-55">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="4940317009-57">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-58">(</span><span class="p" data-group-id="4940317009-59">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erl&quot;</span><span class="p" data-group-id="4940317009-59">]</span><span class="p" data-group-id="4940317009-58">)</span><span class="p" data-group-id="4940317009-57">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="4940317009-60">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-61">(</span><span class="p" data-group-id="4940317009-62">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start&quot;</span><span class="p" data-group-id="4940317009-62">]</span><span class="p" data-group-id="4940317009-61">)</span><span class="p" data-group-id="4940317009-60">)</span><span class="p">,</span><span class="w">
│ │ │ │ +
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-63">(</span><span class="s">&quot;Creating temporary directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-64">[</span><span class="n">TmpBinDir</span><span class="p" data-group-id="4940317009-64">]</span><span class="p" data-group-id="4940317009-63">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="4940317009-65">(</span><span class="n">TmpBinDir</span><span class="p" data-group-id="4940317009-65">)</span><span class="p">,</span><span class="w">
│ │ │ │ +
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-66">(</span><span class="s">&quot;Copying file \&quot;~ts.boot\&quot; to ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="4940317009-67">[</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-68">(</span><span class="p" data-group-id="4940317009-69">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start.boot&quot;</span><span class="p" data-group-id="4940317009-69">]</span><span class="p" data-group-id="4940317009-68">)</span><span class="p" data-group-id="4940317009-67">]</span><span class="p" data-group-id="4940317009-66">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="4940317009-70">(</span><span class="n">PlainRelFileName</span><span class="o">++</span><span class="s">&quot;.boot&quot;</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-71">(</span><span class="p" data-group-id="4940317009-72">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start.boot&quot;</span><span class="p" data-group-id="4940317009-72">]</span><span class="p" data-group-id="4940317009-71">)</span><span class="p" data-group-id="4940317009-70">)</span><span class="p">,</span><span class="w">
│ │ │ │  
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-73">(</span><span class="s">&quot;Copying files \&quot;epmd\&quot;, \&quot;run_erl\&quot; and \&quot;to_erl\&quot; from \n&quot;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-73">(</span><span class="s">&quot;Copying files \&quot;epmd\&quot;, \&quot;run_erl\&quot; and \&quot;to_erl\&quot; from \n&quot;</span><span class="w">
│ │ │ │                </span><span class="s">&quot;~ts to ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="7066557652-74">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="n">TmpBinDir</span><span class="p" data-group-id="7066557652-74">]</span><span class="p" data-group-id="7066557652-73">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="7066557652-75">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-76">(</span><span class="p" data-group-id="7066557652-77">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;epmd&quot;</span><span class="p" data-group-id="7066557652-77">]</span><span class="p" data-group-id="7066557652-76">)</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-78">(</span><span class="p" data-group-id="7066557652-79">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;epmd&quot;</span><span class="p" data-group-id="7066557652-79">]</span><span class="p" data-group-id="7066557652-78">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-80">[</span><span class="ss">preserve</span><span class="p" data-group-id="7066557652-80">]</span><span class="p" data-group-id="7066557652-75">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="7066557652-81">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-82">(</span><span class="p" data-group-id="7066557652-83">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;run_erl&quot;</span><span class="p" data-group-id="7066557652-83">]</span><span class="p" data-group-id="7066557652-82">)</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-84">(</span><span class="p" data-group-id="7066557652-85">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;run_erl&quot;</span><span class="p" data-group-id="7066557652-85">]</span><span class="p" data-group-id="7066557652-84">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-86">[</span><span class="ss">preserve</span><span class="p" data-group-id="7066557652-86">]</span><span class="p" data-group-id="7066557652-81">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="7066557652-87">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-88">(</span><span class="p" data-group-id="7066557652-89">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;to_erl&quot;</span><span class="p" data-group-id="7066557652-89">]</span><span class="p" data-group-id="7066557652-88">)</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-90">(</span><span class="p" data-group-id="7066557652-91">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;to_erl&quot;</span><span class="p" data-group-id="7066557652-91">]</span><span class="p" data-group-id="7066557652-90">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-92">[</span><span class="ss">preserve</span><span class="p" data-group-id="7066557652-92">]</span><span class="p" data-group-id="7066557652-87">)</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="4940317009-74">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="n">TmpBinDir</span><span class="p" data-group-id="4940317009-74">]</span><span class="p" data-group-id="4940317009-73">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="4940317009-75">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-76">(</span><span class="p" data-group-id="4940317009-77">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;epmd&quot;</span><span class="p" data-group-id="4940317009-77">]</span><span class="p" data-group-id="4940317009-76">)</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-78">(</span><span class="p" data-group-id="4940317009-79">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;epmd&quot;</span><span class="p" data-group-id="4940317009-79">]</span><span class="p" data-group-id="4940317009-78">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-80">[</span><span class="ss">preserve</span><span class="p" data-group-id="4940317009-80">]</span><span class="p" data-group-id="4940317009-75">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="4940317009-81">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-82">(</span><span class="p" data-group-id="4940317009-83">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;run_erl&quot;</span><span class="p" data-group-id="4940317009-83">]</span><span class="p" data-group-id="4940317009-82">)</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-84">(</span><span class="p" data-group-id="4940317009-85">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;run_erl&quot;</span><span class="p" data-group-id="4940317009-85">]</span><span class="p" data-group-id="4940317009-84">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-86">[</span><span class="ss">preserve</span><span class="p" data-group-id="4940317009-86">]</span><span class="p" data-group-id="4940317009-81">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="4940317009-87">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-88">(</span><span class="p" data-group-id="4940317009-89">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;to_erl&quot;</span><span class="p" data-group-id="4940317009-89">]</span><span class="p" data-group-id="4940317009-88">)</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-90">(</span><span class="p" data-group-id="4940317009-91">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;to_erl&quot;</span><span class="p" data-group-id="4940317009-91">]</span><span class="p" data-group-id="4940317009-90">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-92">[</span><span class="ss">preserve</span><span class="p" data-group-id="4940317009-92">]</span><span class="p" data-group-id="4940317009-87">)</span><span class="p">,</span><span class="w">
│ │ │ │  
│ │ │ │      </span><span class="c1">%% This is needed if &#39;start&#39; script created from &#39;start.src&#39; shall</span><span class="w">
│ │ │ │      </span><span class="c1">%% be used as it points out this directory as log dir for &#39;run_erl&#39;</span><span class="w">
│ │ │ │ -    </span><span class="n">TmpLogDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-93">(</span><span class="p" data-group-id="7066557652-94">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;log&quot;</span><span class="p" data-group-id="7066557652-94">]</span><span class="p" data-group-id="7066557652-93">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-95">(</span><span class="s">&quot;Creating temporary directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-96">[</span><span class="n">TmpLogDir</span><span class="p" data-group-id="7066557652-96">]</span><span class="p" data-group-id="7066557652-95">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="7066557652-97">(</span><span class="n">TmpLogDir</span><span class="p" data-group-id="7066557652-97">)</span><span class="p">,</span><span class="w">
│ │ │ │ -
│ │ │ │ -    </span><span class="n">StartErlDataFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-98">(</span><span class="p" data-group-id="7066557652-99">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl.data&quot;</span><span class="p" data-group-id="7066557652-99">]</span><span class="p" data-group-id="7066557652-98">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-100">(</span><span class="s">&quot;Creating ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-101">[</span><span class="n">StartErlDataFile</span><span class="p" data-group-id="7066557652-101">]</span><span class="p" data-group-id="7066557652-100">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">StartErlData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">io_lib</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-102">(</span><span class="s">&quot;</span><span class="si">~s</span><span class="s"> </span><span class="si">~s</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-103">[</span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="7066557652-103">]</span><span class="p" data-group-id="7066557652-102">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">write_file</span><span class="p" data-group-id="7066557652-104">(</span><span class="n">StartErlDataFile</span><span class="p">,</span><span class="w"> </span><span class="n">StartErlData</span><span class="p" data-group-id="7066557652-104">)</span><span class="p">,</span><span class="w">
│ │ │ │ -
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-105">(</span><span class="s">&quot;Recreating tar file ~ts from contents in directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -	      </span><span class="p" data-group-id="7066557652-106">[</span><span class="n">TarFileName</span><span class="p">,</span><span class="n">TmpDir</span><span class="p" data-group-id="7066557652-106">]</span><span class="p" data-group-id="7066557652-105">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7066557652-107">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Tar</span><span class="p" data-group-id="7066557652-107">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="7066557652-108">(</span><span class="n">TarFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-109">[</span><span class="ss">write</span><span class="p">,</span><span class="w"> </span><span class="ss">compressed</span><span class="p" data-group-id="7066557652-109">]</span><span class="p" data-group-id="7066557652-108">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">TmpLogDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-93">(</span><span class="p" data-group-id="4940317009-94">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;log&quot;</span><span class="p" data-group-id="4940317009-94">]</span><span class="p" data-group-id="4940317009-93">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-95">(</span><span class="s">&quot;Creating temporary directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-96">[</span><span class="n">TmpLogDir</span><span class="p" data-group-id="4940317009-96">]</span><span class="p" data-group-id="4940317009-95">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="4940317009-97">(</span><span class="n">TmpLogDir</span><span class="p" data-group-id="4940317009-97">)</span><span class="p">,</span><span class="w">
│ │ │ │ +
│ │ │ │ +    </span><span class="n">StartErlDataFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-98">(</span><span class="p" data-group-id="4940317009-99">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl.data&quot;</span><span class="p" data-group-id="4940317009-99">]</span><span class="p" data-group-id="4940317009-98">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-100">(</span><span class="s">&quot;Creating ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-101">[</span><span class="n">StartErlDataFile</span><span class="p" data-group-id="4940317009-101">]</span><span class="p" data-group-id="4940317009-100">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">StartErlData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">io_lib</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-102">(</span><span class="s">&quot;</span><span class="si">~s</span><span class="s"> </span><span class="si">~s</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-103">[</span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="4940317009-103">]</span><span class="p" data-group-id="4940317009-102">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">write_file</span><span class="p" data-group-id="4940317009-104">(</span><span class="n">StartErlDataFile</span><span class="p">,</span><span class="w"> </span><span class="n">StartErlData</span><span class="p" data-group-id="4940317009-104">)</span><span class="p">,</span><span class="w">
│ │ │ │ +
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-105">(</span><span class="s">&quot;Recreating tar file ~ts from contents in directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +	      </span><span class="p" data-group-id="4940317009-106">[</span><span class="n">TarFileName</span><span class="p">,</span><span class="n">TmpDir</span><span class="p" data-group-id="4940317009-106">]</span><span class="p" data-group-id="4940317009-105">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4940317009-107">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Tar</span><span class="p" data-group-id="4940317009-107">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="4940317009-108">(</span><span class="n">TarFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-109">[</span><span class="ss">write</span><span class="p">,</span><span class="w"> </span><span class="ss">compressed</span><span class="p" data-group-id="4940317009-109">]</span><span class="p" data-group-id="4940317009-108">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="c1">%% {ok, Cwd} = file:get_cwd(),</span><span class="w">
│ │ │ │      </span><span class="c1">%% file:set_cwd(&quot;tmp&quot;),</span><span class="w">
│ │ │ │      </span><span class="n">ErtsDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="o">++</span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="7066557652-110">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-111">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="7066557652-111">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-112">[</span><span class="p" data-group-id="7066557652-112">]</span><span class="p" data-group-id="7066557652-110">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="7066557652-113">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-114">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="n">ErtsDir</span><span class="p" data-group-id="7066557652-114">)</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsDir</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-115">[</span><span class="p" data-group-id="7066557652-115">]</span><span class="p" data-group-id="7066557652-113">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="7066557652-116">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-117">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;releases&quot;</span><span class="p" data-group-id="7066557652-117">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-118">[</span><span class="p" data-group-id="7066557652-118">]</span><span class="p" data-group-id="7066557652-116">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="7066557652-119">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-120">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;lib&quot;</span><span class="p" data-group-id="7066557652-120">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;lib&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-121">[</span><span class="p" data-group-id="7066557652-121">]</span><span class="p" data-group-id="7066557652-119">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="7066557652-122">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-123">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;log&quot;</span><span class="p" data-group-id="7066557652-123">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;log&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-124">[</span><span class="p" data-group-id="7066557652-124">]</span><span class="p" data-group-id="7066557652-122">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="7066557652-125">(</span><span class="n">Tar</span><span class="p" data-group-id="7066557652-125">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="4940317009-110">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-111">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="4940317009-111">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-112">[</span><span class="p" data-group-id="4940317009-112">]</span><span class="p" data-group-id="4940317009-110">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="4940317009-113">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-114">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="n">ErtsDir</span><span class="p" data-group-id="4940317009-114">)</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsDir</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-115">[</span><span class="p" data-group-id="4940317009-115">]</span><span class="p" data-group-id="4940317009-113">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="4940317009-116">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-117">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;releases&quot;</span><span class="p" data-group-id="4940317009-117">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-118">[</span><span class="p" data-group-id="4940317009-118">]</span><span class="p" data-group-id="4940317009-116">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="4940317009-119">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-120">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;lib&quot;</span><span class="p" data-group-id="4940317009-120">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;lib&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-121">[</span><span class="p" data-group-id="4940317009-121">]</span><span class="p" data-group-id="4940317009-119">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="4940317009-122">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-123">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;log&quot;</span><span class="p" data-group-id="4940317009-123">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;log&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-124">[</span><span class="p" data-group-id="4940317009-124">]</span><span class="p" data-group-id="4940317009-122">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="4940317009-125">(</span><span class="n">Tar</span><span class="p" data-group-id="4940317009-125">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="c1">%% file:set_cwd(Cwd),</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-126">(</span><span class="s">&quot;Removing directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="7066557652-127">[</span><span class="n">TmpDir</span><span class="p" data-group-id="7066557652-127">]</span><span class="p" data-group-id="7066557652-126">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">remove_dir_tree</span><span class="p" data-group-id="7066557652-128">(</span><span class="n">TmpDir</span><span class="p" data-group-id="7066557652-128">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-126">(</span><span class="s">&quot;Removing directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="4940317009-127">[</span><span class="n">TmpDir</span><span class="p" data-group-id="4940317009-127">]</span><span class="p" data-group-id="4940317009-126">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">remove_dir_tree</span><span class="p" data-group-id="4940317009-128">(</span><span class="n">TmpDir</span><span class="p" data-group-id="4940317009-128">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  
│ │ │ │ -</span><span class="nf">install</span><span class="p" data-group-id="7066557652-129">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="7066557652-129">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">install</span><span class="p" data-group-id="4940317009-129">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="4940317009-129">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">TarFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.tar.gz&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-130">(</span><span class="s">&quot;Extracting ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-131">[</span><span class="n">TarFile</span><span class="p" data-group-id="7066557652-131">]</span><span class="p" data-group-id="7066557652-130">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">extract_tar</span><span class="p" data-group-id="7066557652-132">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="7066557652-132">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">StartErlDataFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-133">(</span><span class="p" data-group-id="7066557652-134">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl.data&quot;</span><span class="p" data-group-id="7066557652-134">]</span><span class="p" data-group-id="7066557652-133">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7066557652-135">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">StartErlData</span><span class="p" data-group-id="7066557652-135">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">read_txt_file</span><span class="p" data-group-id="7066557652-136">(</span><span class="n">StartErlDataFile</span><span class="p" data-group-id="7066557652-136">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7066557652-137">[</span><span class="n">ErlVsn</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">RelVsn</span><span class="p">|</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7066557652-137">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">string</span><span class="p">:</span><span class="nf">tokens</span><span class="p" data-group-id="7066557652-138">(</span><span class="n">StartErlData</span><span class="p">,</span><span class="w"> </span><span class="s">&quot; \n&quot;</span><span class="p" data-group-id="7066557652-138">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">ErtsBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-139">(</span><span class="p" data-group-id="7066557652-140">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">ErlVsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="7066557652-140">]</span><span class="p" data-group-id="7066557652-139">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">BinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-141">(</span><span class="p" data-group-id="7066557652-142">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="7066557652-142">]</span><span class="p" data-group-id="7066557652-141">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-143">(</span><span class="s">&quot;Substituting in erl.src, start.src and start_erl.src to &quot;</span><span class="w">
│ │ │ │ -              </span><span class="s">&quot;form erl, start and start_erl ...\n&quot;</span><span class="p" data-group-id="7066557652-143">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst_src_scripts</span><span class="p" data-group-id="7066557652-144">(</span><span class="p" data-group-id="7066557652-145">[</span><span class="s">&quot;erl&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl&quot;</span><span class="p" data-group-id="7066557652-145">]</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="n">BinDir</span><span class="p">,</span><span class="w">
│ │ │ │ -                      </span><span class="p" data-group-id="7066557652-146">[</span><span class="p" data-group-id="7066557652-147">{</span><span class="s">&quot;FINAL_ROOTDIR&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="7066557652-147">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-148">{</span><span class="s">&quot;EMU&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;beam&quot;</span><span class="p" data-group-id="7066557652-148">}</span><span class="p" data-group-id="7066557652-146">]</span><span class="p">,</span><span class="w">
│ │ │ │ -                      </span><span class="p" data-group-id="7066557652-149">[</span><span class="ss">preserve</span><span class="p" data-group-id="7066557652-149">]</span><span class="p" data-group-id="7066557652-144">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-130">(</span><span class="s">&quot;Extracting ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-131">[</span><span class="n">TarFile</span><span class="p" data-group-id="4940317009-131">]</span><span class="p" data-group-id="4940317009-130">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">extract_tar</span><span class="p" data-group-id="4940317009-132">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="4940317009-132">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">StartErlDataFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-133">(</span><span class="p" data-group-id="4940317009-134">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl.data&quot;</span><span class="p" data-group-id="4940317009-134">]</span><span class="p" data-group-id="4940317009-133">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4940317009-135">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">StartErlData</span><span class="p" data-group-id="4940317009-135">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">read_txt_file</span><span class="p" data-group-id="4940317009-136">(</span><span class="n">StartErlDataFile</span><span class="p" data-group-id="4940317009-136">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4940317009-137">[</span><span class="n">ErlVsn</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">RelVsn</span><span class="p">|</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="4940317009-137">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">string</span><span class="p">:</span><span class="nf">tokens</span><span class="p" data-group-id="4940317009-138">(</span><span class="n">StartErlData</span><span class="p">,</span><span class="w"> </span><span class="s">&quot; \n&quot;</span><span class="p" data-group-id="4940317009-138">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">ErtsBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-139">(</span><span class="p" data-group-id="4940317009-140">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">ErlVsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="4940317009-140">]</span><span class="p" data-group-id="4940317009-139">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">BinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-141">(</span><span class="p" data-group-id="4940317009-142">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="4940317009-142">]</span><span class="p" data-group-id="4940317009-141">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-143">(</span><span class="s">&quot;Substituting in erl.src, start.src and start_erl.src to &quot;</span><span class="w">
│ │ │ │ +              </span><span class="s">&quot;form erl, start and start_erl ...\n&quot;</span><span class="p" data-group-id="4940317009-143">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst_src_scripts</span><span class="p" data-group-id="4940317009-144">(</span><span class="p" data-group-id="4940317009-145">[</span><span class="s">&quot;erl&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl&quot;</span><span class="p" data-group-id="4940317009-145">]</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="n">BinDir</span><span class="p">,</span><span class="w">
│ │ │ │ +                      </span><span class="p" data-group-id="4940317009-146">[</span><span class="p" data-group-id="4940317009-147">{</span><span class="s">&quot;FINAL_ROOTDIR&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="4940317009-147">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-148">{</span><span class="s">&quot;EMU&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;beam&quot;</span><span class="p" data-group-id="4940317009-148">}</span><span class="p" data-group-id="4940317009-146">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                      </span><span class="p" data-group-id="4940317009-149">[</span><span class="ss">preserve</span><span class="p" data-group-id="4940317009-149">]</span><span class="p" data-group-id="4940317009-144">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="c1">%%! Workaround for pre OTP 17.0: start.src and start_erl.src did</span><span class="w">
│ │ │ │      </span><span class="c1">%%! not have correct permissions, so the above &#39;preserve&#39; option did not help</span><span class="w">
│ │ │ │ -    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">change_mode</span><span class="p" data-group-id="7066557652-150">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-151">(</span><span class="n">BinDir</span><span class="p">,</span><span class="s">&quot;start&quot;</span><span class="p" data-group-id="7066557652-151">)</span><span class="p">,</span><span class="mi">8#0755</span><span class="p" data-group-id="7066557652-150">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">change_mode</span><span class="p" data-group-id="7066557652-152">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-153">(</span><span class="n">BinDir</span><span class="p">,</span><span class="s">&quot;start_erl&quot;</span><span class="p" data-group-id="7066557652-153">)</span><span class="p">,</span><span class="mi">8#0755</span><span class="p" data-group-id="7066557652-152">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">change_mode</span><span class="p" data-group-id="4940317009-150">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-151">(</span><span class="n">BinDir</span><span class="p">,</span><span class="s">&quot;start&quot;</span><span class="p" data-group-id="4940317009-151">)</span><span class="p">,</span><span class="mi">8#0755</span><span class="p" data-group-id="4940317009-150">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">change_mode</span><span class="p" data-group-id="4940317009-152">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-153">(</span><span class="n">BinDir</span><span class="p">,</span><span class="s">&quot;start_erl&quot;</span><span class="p" data-group-id="4940317009-153">)</span><span class="p">,</span><span class="mi">8#0755</span><span class="p" data-group-id="4940317009-152">)</span><span class="p">,</span><span class="w">
│ │ │ │  
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7066557652-154">(</span><span class="s">&quot;Creating the RELEASES file ...\n&quot;</span><span class="p" data-group-id="7066557652-154">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">create_RELEASES</span><span class="p" data-group-id="7066557652-155">(</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-156">(</span><span class="p" data-group-id="7066557652-157">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -					    </span><span class="nc">filename</span><span class="p">:</span><span class="nf">basename</span><span class="p" data-group-id="7066557652-158">(</span><span class="n">RelFileName</span><span class="p" data-group-id="7066557652-158">)</span><span class="p" data-group-id="7066557652-157">]</span><span class="p" data-group-id="7066557652-156">)</span><span class="p" data-group-id="7066557652-155">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4940317009-154">(</span><span class="s">&quot;Creating the RELEASES file ...\n&quot;</span><span class="p" data-group-id="4940317009-154">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">create_RELEASES</span><span class="p" data-group-id="4940317009-155">(</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-156">(</span><span class="p" data-group-id="4940317009-157">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +					    </span><span class="nc">filename</span><span class="p">:</span><span class="nf">basename</span><span class="p" data-group-id="4940317009-158">(</span><span class="n">RelFileName</span><span class="p" data-group-id="4940317009-158">)</span><span class="p" data-group-id="4940317009-157">]</span><span class="p" data-group-id="4940317009-156">)</span><span class="p" data-group-id="4940317009-155">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% LOCALS</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% make_script(RelFileName,Opts)</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │ -</span><span class="nf">make_script</span><span class="p" data-group-id="7066557652-159">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">Opts</span><span class="p" data-group-id="7066557652-159">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="7066557652-160">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-161">[</span><span class="ss">no_module_tests</span><span class="p">,</span><span class="w">
│ │ │ │ -				       </span><span class="p" data-group-id="7066557652-162">{</span><span class="ss">outdir</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="7066557652-163">(</span><span class="n">RelFileName</span><span class="p" data-group-id="7066557652-163">)</span><span class="p" data-group-id="7066557652-162">}</span><span class="w">
│ │ │ │ -				       </span><span class="p">|</span><span class="n">Opts</span><span class="p" data-group-id="7066557652-161">]</span><span class="p" data-group-id="7066557652-160">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">make_script</span><span class="p" data-group-id="4940317009-159">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">Opts</span><span class="p" data-group-id="4940317009-159">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="4940317009-160">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-161">[</span><span class="ss">no_module_tests</span><span class="p">,</span><span class="w">
│ │ │ │ +				       </span><span class="p" data-group-id="4940317009-162">{</span><span class="ss">outdir</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="4940317009-163">(</span><span class="n">RelFileName</span><span class="p" data-group-id="4940317009-163">)</span><span class="p" data-group-id="4940317009-162">}</span><span class="w">
│ │ │ │ +				       </span><span class="p">|</span><span class="n">Opts</span><span class="p" data-group-id="4940317009-161">]</span><span class="p" data-group-id="4940317009-160">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% make_tar(RelFileName,Opts)</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │ -</span><span class="nf">make_tar</span><span class="p" data-group-id="7066557652-164">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">Opts</span><span class="p" data-group-id="7066557652-164">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">RootDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">code</span><span class="p">:</span><span class="nf">root_dir</span><span class="p" data-group-id="7066557652-165">(</span><span class="p" data-group-id="7066557652-165">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="7066557652-166">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-167">[</span><span class="p" data-group-id="7066557652-168">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="7066557652-168">}</span><span class="p">,</span><span class="w">
│ │ │ │ -				    </span><span class="p" data-group-id="7066557652-169">{</span><span class="ss">outdir</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="7066557652-170">(</span><span class="n">RelFileName</span><span class="p" data-group-id="7066557652-170">)</span><span class="p" data-group-id="7066557652-169">}</span><span class="w">
│ │ │ │ -				    </span><span class="p">|</span><span class="n">Opts</span><span class="p" data-group-id="7066557652-167">]</span><span class="p" data-group-id="7066557652-166">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">make_tar</span><span class="p" data-group-id="4940317009-164">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">Opts</span><span class="p" data-group-id="4940317009-164">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">RootDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">code</span><span class="p">:</span><span class="nf">root_dir</span><span class="p" data-group-id="4940317009-165">(</span><span class="p" data-group-id="4940317009-165">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="4940317009-166">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-167">[</span><span class="p" data-group-id="4940317009-168">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="4940317009-168">}</span><span class="p">,</span><span class="w">
│ │ │ │ +				    </span><span class="p" data-group-id="4940317009-169">{</span><span class="ss">outdir</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="4940317009-170">(</span><span class="n">RelFileName</span><span class="p" data-group-id="4940317009-170">)</span><span class="p" data-group-id="4940317009-169">}</span><span class="w">
│ │ │ │ +				    </span><span class="p">|</span><span class="n">Opts</span><span class="p" data-group-id="4940317009-167">]</span><span class="p" data-group-id="4940317009-166">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% extract_tar(TarFile, DestDir)</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │ -</span><span class="nf">extract_tar</span><span class="p" data-group-id="7066557652-171">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p" data-group-id="7066557652-171">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">extract</span><span class="p" data-group-id="7066557652-172">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-173">[</span><span class="p" data-group-id="7066557652-174">{</span><span class="ss">cwd</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p" data-group-id="7066557652-174">}</span><span class="p">,</span><span class="w"> </span><span class="ss">compressed</span><span class="p" data-group-id="7066557652-173">]</span><span class="p" data-group-id="7066557652-172">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">extract_tar</span><span class="p" data-group-id="4940317009-171">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p" data-group-id="4940317009-171">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">extract</span><span class="p" data-group-id="4940317009-172">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-173">[</span><span class="p" data-group-id="4940317009-174">{</span><span class="ss">cwd</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p" data-group-id="4940317009-174">}</span><span class="p">,</span><span class="w"> </span><span class="ss">compressed</span><span class="p" data-group-id="4940317009-173">]</span><span class="p" data-group-id="4940317009-172">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">create_RELEASES</span><span class="p" data-group-id="7066557652-175">(</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="p" data-group-id="7066557652-175">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">create_RELEASES</span><span class="p" data-group-id="7066557652-176">(</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.rel&quot;</span><span class="p" data-group-id="7066557652-176">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">create_RELEASES</span><span class="p" data-group-id="4940317009-175">(</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="p" data-group-id="4940317009-175">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">create_RELEASES</span><span class="p" data-group-id="4940317009-176">(</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.rel&quot;</span><span class="p" data-group-id="4940317009-176">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">subst_src_scripts</span><span class="p" data-group-id="7066557652-177">(</span><span class="n">Scripts</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7066557652-177">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="7066557652-178">(</span><span class="nf">fun</span><span class="p" data-group-id="7066557652-179">(</span><span class="n">Script</span><span class="p" data-group-id="7066557652-179">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                          </span><span class="nf">subst_src_script</span><span class="p" data-group-id="7066557652-180">(</span><span class="n">Script</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w">
│ │ │ │ -                                           </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7066557652-180">)</span><span class="w">
│ │ │ │ -                  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Scripts</span><span class="p" data-group-id="7066557652-178">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">subst_src_script</span><span class="p" data-group-id="7066557652-181">(</span><span class="n">Script</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7066557652-181">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst_file</span><span class="p" data-group-id="7066557652-182">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-183">(</span><span class="p" data-group-id="7066557652-184">[</span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">Script</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.src&quot;</span><span class="p" data-group-id="7066557652-184">]</span><span class="p" data-group-id="7066557652-183">)</span><span class="p">,</span><span class="w">
│ │ │ │ -               </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-185">(</span><span class="p" data-group-id="7066557652-186">[</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Script</span><span class="p" data-group-id="7066557652-186">]</span><span class="p" data-group-id="7066557652-185">)</span><span class="p">,</span><span class="w">
│ │ │ │ -               </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7066557652-182">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">subst_file</span><span class="p" data-group-id="7066557652-187">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7066557652-187">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7066557652-188">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Conts</span><span class="p" data-group-id="7066557652-188">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">read_txt_file</span><span class="p" data-group-id="7066557652-189">(</span><span class="n">Src</span><span class="p" data-group-id="7066557652-189">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">NConts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">subst</span><span class="p" data-group-id="7066557652-190">(</span><span class="n">Conts</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="7066557652-190">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">write_file</span><span class="p" data-group-id="7066557652-191">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">NConts</span><span class="p" data-group-id="7066557652-191">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="7066557652-192">(</span><span class="ss">preserve</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7066557652-192">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">subst_src_scripts</span><span class="p" data-group-id="4940317009-177">(</span><span class="n">Scripts</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4940317009-177">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="4940317009-178">(</span><span class="nf">fun</span><span class="p" data-group-id="4940317009-179">(</span><span class="n">Script</span><span class="p" data-group-id="4940317009-179">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                          </span><span class="nf">subst_src_script</span><span class="p" data-group-id="4940317009-180">(</span><span class="n">Script</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w">
│ │ │ │ +                                           </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4940317009-180">)</span><span class="w">
│ │ │ │ +                  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Scripts</span><span class="p" data-group-id="4940317009-178">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">subst_src_script</span><span class="p" data-group-id="4940317009-181">(</span><span class="n">Script</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4940317009-181">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst_file</span><span class="p" data-group-id="4940317009-182">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-183">(</span><span class="p" data-group-id="4940317009-184">[</span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">Script</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.src&quot;</span><span class="p" data-group-id="4940317009-184">]</span><span class="p" data-group-id="4940317009-183">)</span><span class="p">,</span><span class="w">
│ │ │ │ +               </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-185">(</span><span class="p" data-group-id="4940317009-186">[</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Script</span><span class="p" data-group-id="4940317009-186">]</span><span class="p" data-group-id="4940317009-185">)</span><span class="p">,</span><span class="w">
│ │ │ │ +               </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4940317009-182">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">subst_file</span><span class="p" data-group-id="4940317009-187">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4940317009-187">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4940317009-188">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Conts</span><span class="p" data-group-id="4940317009-188">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">read_txt_file</span><span class="p" data-group-id="4940317009-189">(</span><span class="n">Src</span><span class="p" data-group-id="4940317009-189">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">NConts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">subst</span><span class="p" data-group-id="4940317009-190">(</span><span class="n">Conts</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="4940317009-190">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">write_file</span><span class="p" data-group-id="4940317009-191">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">NConts</span><span class="p" data-group-id="4940317009-191">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="4940317009-192">(</span><span class="ss">preserve</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4940317009-192">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="7066557652-193">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="7066557652-193">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file_info</span><span class="p" data-group-id="7066557652-194">(</span><span class="n">Src</span><span class="p" data-group-id="7066557652-194">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nc">file</span><span class="p">:</span><span class="nf">write_file_info</span><span class="p" data-group-id="7066557652-195">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="7066557652-195">)</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="4940317009-193">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="4940317009-193">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file_info</span><span class="p" data-group-id="4940317009-194">(</span><span class="n">Src</span><span class="p" data-group-id="4940317009-194">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">file</span><span class="p">:</span><span class="nf">write_file_info</span><span class="p" data-group-id="4940317009-195">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="4940317009-195">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">ok</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% subst(Str, Vars)</span><span class="w">
│ │ │ │  </span><span class="c1">%% Vars = [{Var, Val}]</span><span class="w">
│ │ │ │  </span><span class="c1">%% Var = Val = string()</span><span class="w">
│ │ │ │  </span><span class="c1">%% Substitute all occurrences of %Var% for Val in Str, using the list</span><span class="w">
│ │ │ │  </span><span class="c1">%% of variables in Vars.</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="7066557652-196">(</span><span class="n">Str</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="7066557652-196">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst</span><span class="p" data-group-id="7066557652-197">(</span><span class="n">Str</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-198">[</span><span class="p" data-group-id="7066557652-198">]</span><span class="p" data-group-id="7066557652-197">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="4940317009-196">(</span><span class="n">Str</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="4940317009-196">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst</span><span class="p" data-group-id="4940317009-197">(</span><span class="n">Str</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-198">[</span><span class="p" data-group-id="4940317009-198">]</span><span class="p" data-group-id="4940317009-197">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="7066557652-199">(</span><span class="p" data-group-id="7066557652-200">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7066557652-200">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7066557652-199">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$A</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$Z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst_var</span><span class="p" data-group-id="7066557652-201">(</span><span class="p" data-group-id="7066557652-202">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7066557652-202">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-203">[</span><span class="p" data-group-id="7066557652-203">]</span><span class="p" data-group-id="7066557652-201">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="7066557652-204">(</span><span class="p" data-group-id="7066557652-205">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7066557652-205">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7066557652-204">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$a</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst_var</span><span class="p" data-group-id="7066557652-206">(</span><span class="p" data-group-id="7066557652-207">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7066557652-207">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-208">[</span><span class="p" data-group-id="7066557652-208">]</span><span class="p" data-group-id="7066557652-206">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="7066557652-209">(</span><span class="p" data-group-id="7066557652-210">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7066557652-210">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7066557652-209">)</span><span class="w"> </span><span class="k">when</span><span class="w">  </span><span class="n">C</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="sc">$_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst_var</span><span class="p" data-group-id="7066557652-211">(</span><span class="p" data-group-id="7066557652-212">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7066557652-212">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-213">[</span><span class="p" data-group-id="7066557652-213">]</span><span class="p" data-group-id="7066557652-211">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="7066557652-214">(</span><span class="p" data-group-id="7066557652-215">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7066557652-215">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7066557652-214">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst</span><span class="p" data-group-id="7066557652-216">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-217">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7066557652-217">]</span><span class="p" data-group-id="7066557652-216">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="7066557652-218">(</span><span class="p" data-group-id="7066557652-219">[</span><span class="p" data-group-id="7066557652-219">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7066557652-218">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="7066557652-220">(</span><span class="n">Result</span><span class="p" data-group-id="7066557652-220">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">subst_var</span><span class="p" data-group-id="7066557652-221">(</span><span class="p" data-group-id="7066557652-222">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7066557652-222">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="7066557652-221">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Key</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="7066557652-223">(</span><span class="n">VarAcc</span><span class="p" data-group-id="7066557652-223">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="7066557652-224">(</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="7066557652-224">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="7066557652-225">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-226">{</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="7066557652-226">}</span><span class="p" data-group-id="7066557652-225">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">subst</span><span class="p" data-group-id="7066557652-227">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="7066557652-228">(</span><span class="n">Value</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7066557652-228">)</span><span class="p" data-group-id="7066557652-227">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="4940317009-199">(</span><span class="p" data-group-id="4940317009-200">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4940317009-200">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4940317009-199">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$A</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$Z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst_var</span><span class="p" data-group-id="4940317009-201">(</span><span class="p" data-group-id="4940317009-202">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4940317009-202">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-203">[</span><span class="p" data-group-id="4940317009-203">]</span><span class="p" data-group-id="4940317009-201">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="4940317009-204">(</span><span class="p" data-group-id="4940317009-205">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4940317009-205">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4940317009-204">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$a</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst_var</span><span class="p" data-group-id="4940317009-206">(</span><span class="p" data-group-id="4940317009-207">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4940317009-207">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-208">[</span><span class="p" data-group-id="4940317009-208">]</span><span class="p" data-group-id="4940317009-206">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="4940317009-209">(</span><span class="p" data-group-id="4940317009-210">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4940317009-210">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4940317009-209">)</span><span class="w"> </span><span class="k">when</span><span class="w">  </span><span class="n">C</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="sc">$_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst_var</span><span class="p" data-group-id="4940317009-211">(</span><span class="p" data-group-id="4940317009-212">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4940317009-212">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-213">[</span><span class="p" data-group-id="4940317009-213">]</span><span class="p" data-group-id="4940317009-211">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="4940317009-214">(</span><span class="p" data-group-id="4940317009-215">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4940317009-215">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4940317009-214">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst</span><span class="p" data-group-id="4940317009-216">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-217">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4940317009-217">]</span><span class="p" data-group-id="4940317009-216">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="4940317009-218">(</span><span class="p" data-group-id="4940317009-219">[</span><span class="p" data-group-id="4940317009-219">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4940317009-218">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="4940317009-220">(</span><span class="n">Result</span><span class="p" data-group-id="4940317009-220">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">subst_var</span><span class="p" data-group-id="4940317009-221">(</span><span class="p" data-group-id="4940317009-222">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4940317009-222">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="4940317009-221">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Key</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="4940317009-223">(</span><span class="n">VarAcc</span><span class="p" data-group-id="4940317009-223">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="4940317009-224">(</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="4940317009-224">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="4940317009-225">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-226">{</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="4940317009-226">}</span><span class="p" data-group-id="4940317009-225">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">subst</span><span class="p" data-group-id="4940317009-227">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="4940317009-228">(</span><span class="n">Value</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4940317009-228">)</span><span class="p" data-group-id="4940317009-227">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">subst</span><span class="p" data-group-id="7066557652-229">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-230">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">VarAcc</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="7066557652-231">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7066557652-231">]</span><span class="p" data-group-id="7066557652-230">]</span><span class="p" data-group-id="7066557652-229">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">subst</span><span class="p" data-group-id="4940317009-229">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-230">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">VarAcc</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="4940317009-231">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4940317009-231">]</span><span class="p" data-group-id="4940317009-230">]</span><span class="p" data-group-id="4940317009-229">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">subst_var</span><span class="p" data-group-id="7066557652-232">(</span><span class="p" data-group-id="7066557652-233">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7066557652-233">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="7066557652-232">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst_var</span><span class="p" data-group-id="7066557652-234">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-235">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="7066557652-235">]</span><span class="p" data-group-id="7066557652-234">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">subst_var</span><span class="p" data-group-id="7066557652-236">(</span><span class="p" data-group-id="7066557652-237">[</span><span class="p" data-group-id="7066557652-237">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="7066557652-236">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst</span><span class="p" data-group-id="7066557652-238">(</span><span class="p" data-group-id="7066557652-239">[</span><span class="p" data-group-id="7066557652-239">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-240">[</span><span class="n">VarAcc</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="7066557652-241">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7066557652-241">]</span><span class="p" data-group-id="7066557652-240">]</span><span class="p" data-group-id="7066557652-238">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">copy_file</span><span class="p" data-group-id="7066557652-242">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p" data-group-id="7066557652-242">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="7066557652-243">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-244">[</span><span class="p" data-group-id="7066557652-244">]</span><span class="p" data-group-id="7066557652-243">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">copy_file</span><span class="p" data-group-id="7066557652-245">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7066557652-245">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7066557652-246">{</span><span class="ss">ok</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="7066557652-246">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">copy</span><span class="p" data-group-id="7066557652-247">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p" data-group-id="7066557652-247">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="7066557652-248">(</span><span class="ss">preserve</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7066557652-248">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">subst_var</span><span class="p" data-group-id="4940317009-232">(</span><span class="p" data-group-id="4940317009-233">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4940317009-233">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="4940317009-232">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst_var</span><span class="p" data-group-id="4940317009-234">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-235">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="4940317009-235">]</span><span class="p" data-group-id="4940317009-234">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">subst_var</span><span class="p" data-group-id="4940317009-236">(</span><span class="p" data-group-id="4940317009-237">[</span><span class="p" data-group-id="4940317009-237">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="4940317009-236">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst</span><span class="p" data-group-id="4940317009-238">(</span><span class="p" data-group-id="4940317009-239">[</span><span class="p" data-group-id="4940317009-239">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-240">[</span><span class="n">VarAcc</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="4940317009-241">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4940317009-241">]</span><span class="p" data-group-id="4940317009-240">]</span><span class="p" data-group-id="4940317009-238">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">copy_file</span><span class="p" data-group-id="4940317009-242">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p" data-group-id="4940317009-242">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="4940317009-243">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-244">[</span><span class="p" data-group-id="4940317009-244">]</span><span class="p" data-group-id="4940317009-243">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">copy_file</span><span class="p" data-group-id="4940317009-245">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4940317009-245">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4940317009-246">{</span><span class="ss">ok</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4940317009-246">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">copy</span><span class="p" data-group-id="4940317009-247">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p" data-group-id="4940317009-247">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="4940317009-248">(</span><span class="ss">preserve</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4940317009-248">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="7066557652-249">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="7066557652-249">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file_info</span><span class="p" data-group-id="7066557652-250">(</span><span class="n">Src</span><span class="p" data-group-id="7066557652-250">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nc">file</span><span class="p">:</span><span class="nf">write_file_info</span><span class="p" data-group-id="7066557652-251">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="7066557652-251">)</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="4940317009-249">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="4940317009-249">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file_info</span><span class="p" data-group-id="4940317009-250">(</span><span class="n">Src</span><span class="p" data-group-id="4940317009-250">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">file</span><span class="p">:</span><span class="nf">write_file_info</span><span class="p" data-group-id="4940317009-251">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="4940317009-251">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">ok</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">write_file</span><span class="p" data-group-id="7066557652-252">(</span><span class="n">FName</span><span class="p">,</span><span class="w"> </span><span class="n">Conts</span><span class="p" data-group-id="7066557652-252">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Enc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">native_name_encoding</span><span class="p" data-group-id="7066557652-253">(</span><span class="p" data-group-id="7066557652-253">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7066557652-254">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7066557652-254">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="7066557652-255">(</span><span class="n">FName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-256">[</span><span class="ss">write</span><span class="p" data-group-id="7066557652-256">]</span><span class="p" data-group-id="7066557652-255">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">write</span><span class="p" data-group-id="7066557652-257">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="nc">unicode</span><span class="p">:</span><span class="nf">characters_to_binary</span><span class="p" data-group-id="7066557652-258">(</span><span class="n">Conts</span><span class="p">,</span><span class="n">Enc</span><span class="p">,</span><span class="n">Enc</span><span class="p" data-group-id="7066557652-258">)</span><span class="p" data-group-id="7066557652-257">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="7066557652-259">(</span><span class="n">Fd</span><span class="p" data-group-id="7066557652-259">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">read_txt_file</span><span class="p" data-group-id="7066557652-260">(</span><span class="n">File</span><span class="p" data-group-id="7066557652-260">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7066557652-261">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Bin</span><span class="p" data-group-id="7066557652-261">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file</span><span class="p" data-group-id="7066557652-262">(</span><span class="n">File</span><span class="p" data-group-id="7066557652-262">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7066557652-263">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_list</span><span class="p" data-group-id="7066557652-264">(</span><span class="n">Bin</span><span class="p" data-group-id="7066557652-264">)</span><span class="p" data-group-id="7066557652-263">}</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">remove_dir_tree</span><span class="p" data-group-id="7066557652-265">(</span><span class="n">Dir</span><span class="p" data-group-id="7066557652-265">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">remove_all_files</span><span class="p" data-group-id="7066557652-266">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7066557652-267">[</span><span class="n">Dir</span><span class="p" data-group-id="7066557652-267">]</span><span class="p" data-group-id="7066557652-266">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">remove_all_files</span><span class="p" data-group-id="7066557652-268">(</span><span class="n">Dir</span><span class="p">,</span><span class="w"> </span><span class="n">Files</span><span class="p" data-group-id="7066557652-268">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="7066557652-269">(</span><span class="nf">fun</span><span class="p" data-group-id="7066557652-270">(</span><span class="n">File</span><span class="p" data-group-id="7066557652-270">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                          </span><span class="n">FilePath</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7066557652-271">(</span><span class="p" data-group-id="7066557652-272">[</span><span class="n">Dir</span><span class="p">,</span><span class="w"> </span><span class="n">File</span><span class="p" data-group-id="7066557652-272">]</span><span class="p" data-group-id="7066557652-271">)</span><span class="p">,</span><span class="w">
│ │ │ │ -                          </span><span class="k">case</span><span class="w"> </span><span class="nc">filelib</span><span class="p">:</span><span class="nf">is_dir</span><span class="p" data-group-id="7066557652-273">(</span><span class="n">FilePath</span><span class="p" data-group-id="7066557652-273">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">write_file</span><span class="p" data-group-id="4940317009-252">(</span><span class="n">FName</span><span class="p">,</span><span class="w"> </span><span class="n">Conts</span><span class="p" data-group-id="4940317009-252">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Enc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">native_name_encoding</span><span class="p" data-group-id="4940317009-253">(</span><span class="p" data-group-id="4940317009-253">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4940317009-254">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="4940317009-254">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="4940317009-255">(</span><span class="n">FName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-256">[</span><span class="ss">write</span><span class="p" data-group-id="4940317009-256">]</span><span class="p" data-group-id="4940317009-255">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">write</span><span class="p" data-group-id="4940317009-257">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="nc">unicode</span><span class="p">:</span><span class="nf">characters_to_binary</span><span class="p" data-group-id="4940317009-258">(</span><span class="n">Conts</span><span class="p">,</span><span class="n">Enc</span><span class="p">,</span><span class="n">Enc</span><span class="p" data-group-id="4940317009-258">)</span><span class="p" data-group-id="4940317009-257">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="4940317009-259">(</span><span class="n">Fd</span><span class="p" data-group-id="4940317009-259">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">read_txt_file</span><span class="p" data-group-id="4940317009-260">(</span><span class="n">File</span><span class="p" data-group-id="4940317009-260">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4940317009-261">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Bin</span><span class="p" data-group-id="4940317009-261">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file</span><span class="p" data-group-id="4940317009-262">(</span><span class="n">File</span><span class="p" data-group-id="4940317009-262">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4940317009-263">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_list</span><span class="p" data-group-id="4940317009-264">(</span><span class="n">Bin</span><span class="p" data-group-id="4940317009-264">)</span><span class="p" data-group-id="4940317009-263">}</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">remove_dir_tree</span><span class="p" data-group-id="4940317009-265">(</span><span class="n">Dir</span><span class="p" data-group-id="4940317009-265">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">remove_all_files</span><span class="p" data-group-id="4940317009-266">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4940317009-267">[</span><span class="n">Dir</span><span class="p" data-group-id="4940317009-267">]</span><span class="p" data-group-id="4940317009-266">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">remove_all_files</span><span class="p" data-group-id="4940317009-268">(</span><span class="n">Dir</span><span class="p">,</span><span class="w"> </span><span class="n">Files</span><span class="p" data-group-id="4940317009-268">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="4940317009-269">(</span><span class="nf">fun</span><span class="p" data-group-id="4940317009-270">(</span><span class="n">File</span><span class="p" data-group-id="4940317009-270">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                          </span><span class="n">FilePath</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4940317009-271">(</span><span class="p" data-group-id="4940317009-272">[</span><span class="n">Dir</span><span class="p">,</span><span class="w"> </span><span class="n">File</span><span class="p" data-group-id="4940317009-272">]</span><span class="p" data-group-id="4940317009-271">)</span><span class="p">,</span><span class="w">
│ │ │ │ +                          </span><span class="k">case</span><span class="w"> </span><span class="nc">filelib</span><span class="p">:</span><span class="nf">is_dir</span><span class="p" data-group-id="4940317009-273">(</span><span class="n">FilePath</span><span class="p" data-group-id="4940317009-273">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │                                </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                                  </span><span class="p" data-group-id="7066557652-274">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">DirFiles</span><span class="p" data-group-id="7066557652-274">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">list_dir</span><span class="p" data-group-id="7066557652-275">(</span><span class="n">FilePath</span><span class="p" data-group-id="7066557652-275">)</span><span class="p">,</span><span class="w">
│ │ │ │ -                                  </span><span class="nf">remove_all_files</span><span class="p" data-group-id="7066557652-276">(</span><span class="n">FilePath</span><span class="p">,</span><span class="w"> </span><span class="n">DirFiles</span><span class="p" data-group-id="7066557652-276">)</span><span class="p">,</span><span class="w">
│ │ │ │ -                                  </span><span class="nc">file</span><span class="p">:</span><span class="nf">del_dir</span><span class="p" data-group-id="7066557652-277">(</span><span class="n">FilePath</span><span class="p" data-group-id="7066557652-277">)</span><span class="p">;</span><span class="w">
│ │ │ │ +                                  </span><span class="p" data-group-id="4940317009-274">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">DirFiles</span><span class="p" data-group-id="4940317009-274">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">list_dir</span><span class="p" data-group-id="4940317009-275">(</span><span class="n">FilePath</span><span class="p" data-group-id="4940317009-275">)</span><span class="p">,</span><span class="w">
│ │ │ │ +                                  </span><span class="nf">remove_all_files</span><span class="p" data-group-id="4940317009-276">(</span><span class="n">FilePath</span><span class="p">,</span><span class="w"> </span><span class="n">DirFiles</span><span class="p" data-group-id="4940317009-276">)</span><span class="p">,</span><span class="w">
│ │ │ │ +                                  </span><span class="nc">file</span><span class="p">:</span><span class="nf">del_dir</span><span class="p" data-group-id="4940317009-277">(</span><span class="n">FilePath</span><span class="p" data-group-id="4940317009-277">)</span><span class="p">;</span><span class="w">
│ │ │ │                                </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                                  </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="7066557652-278">(</span><span class="n">FilePath</span><span class="p" data-group-id="7066557652-278">)</span><span class="w">
│ │ │ │ +                                  </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="4940317009-278">(</span><span class="n">FilePath</span><span class="p" data-group-id="4940317009-278">)</span><span class="w">
│ │ │ │                            </span><span class="k">end</span><span class="w">
│ │ │ │ -                  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Files</span><span class="p" data-group-id="7066557652-269">)</span><span class="p">.</span></code></pre>
│ │ │ │ +                  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Files</span><span class="p" data-group-id="4940317009-269">)</span><span class="p">.</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/content.opf
│ │ │ │ ├── OEBPS/content.opf
│ │ │ │ │ @@ -1,14 +1,14 @@
│ │ │ │ │  <?xml version="1.0" encoding="utf-8"?>
│ │ │ │ │  <package xmlns="http://www.idpf.org/2007/opf" unique-identifier="project-Erlang System Documentation" version="3.0">
│ │ │ │ │    <metadata xmlns:dc="http://purl.org/dc/elements/1.1/">
│ │ │ │ │      <dc:title>Erlang System Documentation - 29.0-rc3</dc:title>
│ │ │ │ │ -    <dc:identifier id="project-Erlang System Documentation">urn:uuid:1745e863-a49a-b90b-ffa6-0afe165779fa</dc:identifier>
│ │ │ │ │ +    <dc:identifier id="project-Erlang System Documentation">urn:uuid:3da5c23f-9d8b-9b62-01c2-5b7aca6be736</dc:identifier>
│ │ │ │ │      <dc:language>en</dc:language>
│ │ │ │ │ -    <meta property="dcterms:modified">2026-04-15T20:07:07Z</meta>
│ │ │ │ │ +    <meta property="dcterms:modified">2026-04-21T04:13:39Z</meta>
│ │ │ │ │    </metadata>
│ │ │ │ │    <manifest>
│ │ │ │ │      <item id="nav" href="nav.xhtml" media-type="application/xhtml+xml" properties="nav scripted"/>
│ │ │ │ │      <item id="cover" href="title.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │      <item id="readme" href="readme.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │      <item id="installation_guide" href="installation_guide.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │      <item id="install" href="install.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │ @@ -87,22 +87,22 @@
│ │ │ │ │      <item id="nif" href="nif.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │      <item id="debugging" href="debugging.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │      <item id="embedded" href="embedded.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │      <item id="sbom" href="sbom.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │      <item id="vulnerabilities" href="vulnerabilities.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │      <item id="epub-lsjciytm-js" href="dist/epub-LSJCIYTM.js" media-type="text/javascript"/>
│ │ │ │ │      <item id="epub-erlang-espt6bqv-css" href="dist/epub-erlang-ESPT6BQV.css" media-type="text/css"/>
│ │ │ │ │ +    <item id="dist2-gif" href="assets/dist2.gif" media-type="image/gif"/>
│ │ │ │ │      <item id="erlang-logo-png" href="assets/erlang-logo.png" media-type="image/png"/>
│ │ │ │ │      <item id="dist1-gif" href="assets/dist1.gif" media-type="image/gif"/>
│ │ │ │ │ -    <item id="dist2-gif" href="assets/dist2.gif" media-type="image/gif"/>
│ │ │ │ │ +    <item id="prio-msg-recv-png" href="assets/prio-msg-recv.png" media-type="image/png"/>
│ │ │ │ │      <item id="dist3-gif" href="assets/dist3.gif" media-type="image/gif"/>
│ │ │ │ │      <item id="dist4-gif" href="assets/dist4.gif" media-type="image/gif"/>
│ │ │ │ │ -    <item id="dist5-gif" href="assets/dist5.gif" media-type="image/gif"/>
│ │ │ │ │      <item id="ballpoint-pen-svg" href="assets/ballpoint-pen.svg" media-type="image/svg+xml"/>
│ │ │ │ │ -    <item id="prio-msg-recv-png" href="assets/prio-msg-recv.png" media-type="image/png"/>
│ │ │ │ │ +    <item id="dist5-gif" href="assets/dist5.gif" media-type="image/gif"/>
│ │ │ │ │      <item id="logo" href="assets/logo.png" media-type="image/png"/>
│ │ │ │ │    </manifest>
│ │ │ │ │    <spine>
│ │ │ │ │      <itemref idref="cover"/>
│ │ │ │ │      <itemref idref="nav"/>
│ │ │ │ │      <itemref idref="readme"/>
│ │ │ │ │      <itemref idref="installation_guide"/>
│ │ │ ├── OEBPS/conc_prog.xhtml
│ │ │ │ @@ -37,107 +37,107 @@
│ │ │ │  threads of execution in an Erlang program and to allow these threads to
│ │ │ │  communicate with each other. In Erlang, each thread of execution is called a
│ │ │ │  <em>process</em>.</p><p>(Aside: the term &quot;process&quot; is usually used when the threads of execution share
│ │ │ │  no data with each other and the term &quot;thread&quot; when they share data in some way.
│ │ │ │  Threads of execution in Erlang share no data, that is why they are called
│ │ │ │  processes).</p><p>The Erlang BIF <code class="inline">spawn</code> is used to create a new process:
│ │ │ │  <code class="inline">spawn(Module, Exported_Function, List of Arguments)</code>. Consider the following
│ │ │ │ -module:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8979858024-1">(</span><span class="ss">tut14</span><span class="p" data-group-id="8979858024-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +module:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4137242077-1">(</span><span class="ss">tut14</span><span class="p" data-group-id="4137242077-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8979858024-2">(</span><span class="p" data-group-id="8979858024-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8979858024-3">]</span><span class="p" data-group-id="8979858024-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4137242077-2">(</span><span class="p" data-group-id="4137242077-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4137242077-3">]</span><span class="p" data-group-id="4137242077-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">say_something</span><span class="p" data-group-id="8979858024-4">(</span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="8979858024-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">say_something</span><span class="p" data-group-id="4137242077-4">(</span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="4137242077-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">done</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">say_something</span><span class="p" data-group-id="8979858024-5">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="n">Times</span><span class="p" data-group-id="8979858024-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8979858024-6">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8979858024-7">[</span><span class="n">What</span><span class="p" data-group-id="8979858024-7">]</span><span class="p" data-group-id="8979858024-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">say_something</span><span class="p" data-group-id="8979858024-8">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="n">Times</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="8979858024-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="8979858024-9">(</span><span class="p" data-group-id="8979858024-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="8979858024-10">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8979858024-11">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="8979858024-11">]</span><span class="p" data-group-id="8979858024-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="8979858024-12">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8979858024-13">[</span><span class="ss">goodbye</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="8979858024-13">]</span><span class="p" data-group-id="8979858024-12">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nf">c</span><span class="p" data-group-id="7707454896-1">(</span><span class="ss">tut14</span><span class="p" data-group-id="7707454896-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7707454896-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut14</span><span class="p" data-group-id="7707454896-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nc">tut14</span><span class="p">:</span><span class="nf">say_something</span><span class="p" data-group-id="7707454896-3">(</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="7707454896-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">say_something</span><span class="p" data-group-id="4137242077-5">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="n">Times</span><span class="p" data-group-id="4137242077-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4137242077-6">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4137242077-7">[</span><span class="n">What</span><span class="p" data-group-id="4137242077-7">]</span><span class="p" data-group-id="4137242077-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">say_something</span><span class="p" data-group-id="4137242077-8">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="n">Times</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="4137242077-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="4137242077-9">(</span><span class="p" data-group-id="4137242077-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="4137242077-10">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4137242077-11">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="4137242077-11">]</span><span class="p" data-group-id="4137242077-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="4137242077-12">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4137242077-13">[</span><span class="ss">goodbye</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="4137242077-13">]</span><span class="p" data-group-id="4137242077-12">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nf">c</span><span class="p" data-group-id="8622937420-1">(</span><span class="ss">tut14</span><span class="p" data-group-id="8622937420-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8622937420-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut14</span><span class="p" data-group-id="8622937420-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nc">tut14</span><span class="p">:</span><span class="nf">say_something</span><span class="p" data-group-id="8622937420-3">(</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="8622937420-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │ │  </span><span class="ss">done</span></code></pre><p>As shown, the function <code class="inline">say_something</code> writes its first argument the number of
│ │ │ │  times specified by the second argument. The function <code class="inline">start</code> starts two Erlang
│ │ │ │  processes, one that writes &quot;hello&quot; three times and one that writes &quot;goodbye&quot;
│ │ │ │  three times. Both processes use the function <code class="inline">say_something</code>. Notice that a
│ │ │ │  function used in this way by <code class="inline">spawn</code>, to start a process, must be exported from
│ │ │ │ -the module (that is, in the <code class="inline">-export</code> at the start of the module).</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">9&gt; </span><span class="nc">tut14</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="4499269700-1">(</span><span class="p" data-group-id="4499269700-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +the module (that is, in the <code class="inline">-export</code> at the start of the module).</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">9&gt; </span><span class="nc">tut14</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="4022774556-1">(</span><span class="p" data-group-id="4022774556-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │ │  </span><span class="ss">goodbye</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">0.63</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │ │  </span><span class="ss">goodbye</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │ │  </span><span class="ss">goodbye</span></code></pre><p>Notice that it did not write &quot;hello&quot; three times and then &quot;goodbye&quot; three times.
│ │ │ │  Instead, the first process wrote a &quot;hello&quot;, the second a &quot;goodbye&quot;, the first
│ │ │ │  another &quot;hello&quot; and so forth. But where did the <code class="inline">&lt;0.63.0&gt;</code> come from? The return
│ │ │ │  value of a function is the return value of the last &quot;thing&quot; in the function. The
│ │ │ │ -last thing in the function <code class="inline">start</code> is</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="2586317459-1">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2586317459-2">[</span><span class="ss">goodbye</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="2586317459-2">]</span><span class="p" data-group-id="2586317459-1">)</span><span class="p">.</span></code></pre><p><code class="inline">spawn</code> returns a <em>process identifier</em>, or <em>pid</em>, which uniquely identifies the
│ │ │ │ +last thing in the function <code class="inline">start</code> is</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="7531477477-1">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7531477477-2">[</span><span class="ss">goodbye</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="7531477477-2">]</span><span class="p" data-group-id="7531477477-1">)</span><span class="p">.</span></code></pre><p><code class="inline">spawn</code> returns a <em>process identifier</em>, or <em>pid</em>, which uniquely identifies the
│ │ │ │  process. So <code class="inline">&lt;0.63.0&gt;</code> is the pid of the <code class="inline">spawn</code> function call above. The next
│ │ │ │  example shows how to use pids.</p><p>Notice also that ~p is used instead of ~w in <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a>. To quote <a href="../../../lib/stdlib/doc/html/io.html#tilde_p">the manual</a>:</p><blockquote><p>~p Writes the data with standard syntax in the same way as ~w, but breaks terms
│ │ │ │  whose printed representation is longer than one line into many lines and indents
│ │ │ │  each line sensibly. It also tries to detect flat lists of printable characters and
│ │ │ │  to output these as strings</p></blockquote><h2 id="message-passing" class="section-heading">
│ │ │ │    <a href="#message-passing" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Message Passing</span>
│ │ │ │  </h2>
│ │ │ │  <p>In the following example two processes are created and they send messages to
│ │ │ │ -each other a number of times.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4965968269-1">(</span><span class="ss">tut15</span><span class="p" data-group-id="4965968269-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +each other a number of times.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2021030150-1">(</span><span class="ss">tut15</span><span class="p" data-group-id="2021030150-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4965968269-2">(</span><span class="p" data-group-id="4965968269-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4965968269-3">]</span><span class="p" data-group-id="4965968269-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2021030150-2">(</span><span class="p" data-group-id="2021030150-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2021030150-3">]</span><span class="p" data-group-id="2021030150-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="4965968269-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="4965968269-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="2021030150-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="2021030150-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4965968269-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4965968269-6">[</span><span class="p" data-group-id="4965968269-6">]</span><span class="p" data-group-id="4965968269-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2021030150-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2021030150-6">[</span><span class="p" data-group-id="2021030150-6">]</span><span class="p" data-group-id="2021030150-5">)</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="4965968269-7">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="4965968269-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4965968269-8">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4965968269-9">(</span><span class="p" data-group-id="4965968269-9">)</span><span class="p" data-group-id="4965968269-8">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="2021030150-7">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="2021030150-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2021030150-8">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2021030150-9">(</span><span class="p" data-group-id="2021030150-9">)</span><span class="p" data-group-id="2021030150-8">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4965968269-10">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4965968269-11">[</span><span class="p" data-group-id="4965968269-11">]</span><span class="p" data-group-id="4965968269-10">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2021030150-10">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2021030150-11">[</span><span class="p" data-group-id="2021030150-11">]</span><span class="p" data-group-id="2021030150-10">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="4965968269-12">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="4965968269-12">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="2021030150-12">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="2021030150-12">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="4965968269-13">(</span><span class="p" data-group-id="4965968269-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="2021030150-13">(</span><span class="p" data-group-id="2021030150-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4965968269-14">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4965968269-15">[</span><span class="p" data-group-id="4965968269-15">]</span><span class="p" data-group-id="4965968269-14">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="4965968269-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="4965968269-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4965968269-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4965968269-18">[</span><span class="p" data-group-id="4965968269-18">]</span><span class="p" data-group-id="4965968269-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2021030150-14">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2021030150-15">[</span><span class="p" data-group-id="2021030150-15">]</span><span class="p" data-group-id="2021030150-14">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="2021030150-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="2021030150-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2021030150-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2021030150-18">[</span><span class="p" data-group-id="2021030150-18">]</span><span class="p" data-group-id="2021030150-17">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="4965968269-19">(</span><span class="p" data-group-id="4965968269-19">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="2021030150-19">(</span><span class="p" data-group-id="2021030150-19">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="4965968269-20">(</span><span class="p" data-group-id="4965968269-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="4965968269-21">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4965968269-22">[</span><span class="p" data-group-id="4965968269-22">]</span><span class="p" data-group-id="4965968269-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="4965968269-23">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4965968269-24">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="4965968269-24">]</span><span class="p" data-group-id="4965968269-23">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="8332261449-1">(</span><span class="ss">tut15</span><span class="p" data-group-id="8332261449-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8332261449-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut15</span><span class="p" data-group-id="8332261449-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">tut15</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8332261449-3">(</span><span class="p" data-group-id="8332261449-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="2021030150-20">(</span><span class="p" data-group-id="2021030150-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="2021030150-21">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2021030150-22">[</span><span class="p" data-group-id="2021030150-22">]</span><span class="p" data-group-id="2021030150-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="2021030150-23">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2021030150-24">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="2021030150-24">]</span><span class="p" data-group-id="2021030150-23">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="0248931857-1">(</span><span class="ss">tut15</span><span class="p" data-group-id="0248931857-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0248931857-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut15</span><span class="p" data-group-id="0248931857-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">tut15</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="0248931857-3">(</span><span class="p" data-group-id="0248931857-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">0.36</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="ss">ping</span><span class="w"> </span><span class="ss">finished</span><span class="w">
│ │ │ │ -</span><span class="n">Pong</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>The function <code class="inline">start</code> first creates a process, let us call it &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pong_PID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="6672298373-1">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6672298373-2">[</span><span class="p" data-group-id="6672298373-2">]</span><span class="p" data-group-id="6672298373-1">)</span></code></pre><p>This process executes <code class="inline">tut15:pong()</code>. <code class="inline">Pong_PID</code> is the process identity of the
│ │ │ │ -&quot;pong&quot; process. The function <code class="inline">start</code> now creates another process &quot;ping&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="9871152770-1">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9871152770-2">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="9871152770-2">]</span><span class="p" data-group-id="9871152770-1">)</span><span class="p">,</span></code></pre><p>This process executes:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut15</span><span class="p">:</span><span class="nf">ping</span><span class="p" data-group-id="9382632782-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="9382632782-1">)</span></code></pre><p><code class="inline">&lt;0.36.0&gt;</code> is the return value from the <code class="inline">start</code> function.</p><p>The process &quot;pong&quot; now does:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │ +</span><span class="n">Pong</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>The function <code class="inline">start</code> first creates a process, let us call it &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pong_PID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="5731139012-1">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5731139012-2">[</span><span class="p" data-group-id="5731139012-2">]</span><span class="p" data-group-id="5731139012-1">)</span></code></pre><p>This process executes <code class="inline">tut15:pong()</code>. <code class="inline">Pong_PID</code> is the process identity of the
│ │ │ │ +&quot;pong&quot; process. The function <code class="inline">start</code> now creates another process &quot;ping&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="3718646558-1">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3718646558-2">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="3718646558-2">]</span><span class="p" data-group-id="3718646558-1">)</span><span class="p">,</span></code></pre><p>This process executes:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut15</span><span class="p">:</span><span class="nf">ping</span><span class="p" data-group-id="7129773567-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="7129773567-1">)</span></code></pre><p><code class="inline">&lt;0.36.0&gt;</code> is the return value from the <code class="inline">start</code> function.</p><p>The process &quot;pong&quot; now does:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │      </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8545963379-1">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8545963379-2">[</span><span class="p" data-group-id="8545963379-2">]</span><span class="p" data-group-id="8545963379-1">)</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8545963379-3">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="8545963379-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8545963379-4">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8545963379-5">[</span><span class="p" data-group-id="8545963379-5">]</span><span class="p" data-group-id="8545963379-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9355677487-1">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9355677487-2">[</span><span class="p" data-group-id="9355677487-2">]</span><span class="p" data-group-id="9355677487-1">)</span><span class="p">;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9355677487-3">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="9355677487-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9355677487-4">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9355677487-5">[</span><span class="p" data-group-id="9355677487-5">]</span><span class="p" data-group-id="9355677487-4">)</span><span class="p">,</span><span class="w">
│ │ │ │          </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="nf">pong</span><span class="p" data-group-id="8545963379-6">(</span><span class="p" data-group-id="8545963379-6">)</span><span class="w">
│ │ │ │ +        </span><span class="nf">pong</span><span class="p" data-group-id="9355677487-6">(</span><span class="p" data-group-id="9355677487-6">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">receive</code> construct is used to allow processes to wait for messages from
│ │ │ │  other processes. It has the following format:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │     </span><span class="ss">pattern1</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │         </span><span class="ss">actions1</span><span class="p">;</span><span class="w">
│ │ │ │     </span><span class="ss">pattern2</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │         </span><span class="ss">actions2</span><span class="p">;</span><span class="w">
│ │ │ │     </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ @@ -158,84 +158,84 @@
│ │ │ │  queue (keeping the first message and any other messages in the queue). If the
│ │ │ │  second message does not match, the third message is tried, and so on, until the
│ │ │ │  end of the queue is reached. If the end of the queue is reached, the process
│ │ │ │  blocks (stops execution) and waits until a new message is received and this
│ │ │ │  procedure is repeated.</p><p>The Erlang implementation is &quot;clever&quot; and minimizes the number of times each
│ │ │ │  message is tested against the patterns in each <code class="inline">receive</code>.</p><p>Now back to the ping pong example.</p><p>&quot;Pong&quot; is waiting for messages. If the atom <code class="inline">finished</code> is received, &quot;pong&quot;
│ │ │ │  writes &quot;Pong finished&quot; to the output and, as it has nothing more to do,
│ │ │ │ -terminates. If it receives a message with the format:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9990626279-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="9990626279-1">}</span></code></pre><p>it writes &quot;Pong received ping&quot; to the output and sends the atom <code class="inline">pong</code> to the
│ │ │ │ +terminates. If it receives a message with the format:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1841547497-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="1841547497-1">}</span></code></pre><p>it writes &quot;Pong received ping&quot; to the output and sends the atom <code class="inline">pong</code> to the
│ │ │ │  process &quot;ping&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span></code></pre><p>Notice how the operator <code class="inline">!</code> is used to send messages. The syntax of <code class="inline">!</code> is:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Message</span></code></pre><p>That is, <code class="inline">Message</code> (any Erlang term) is sent to the process with identity <code class="inline">Pid</code>.</p><p>After sending the message <code class="inline">pong</code> to the process &quot;ping&quot;, &quot;pong&quot; calls the <code class="inline">pong</code>
│ │ │ │  function again, which causes it to get back to the <code class="inline">receive</code> again and wait for
│ │ │ │ -another message.</p><p>Now let us look at the process &quot;ping&quot;. Recall that it was started by executing:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut15</span><span class="p">:</span><span class="nf">ping</span><span class="p" data-group-id="4108896732-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="4108896732-1">)</span></code></pre><p>Looking at the function <code class="inline">ping/2</code>, the second clause of <code class="inline">ping/2</code> is executed
│ │ │ │ +another message.</p><p>Now let us look at the process &quot;ping&quot;. Recall that it was started by executing:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut15</span><span class="p">:</span><span class="nf">ping</span><span class="p" data-group-id="9613963938-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="9613963938-1">)</span></code></pre><p>Looking at the function <code class="inline">ping/2</code>, the second clause of <code class="inline">ping/2</code> is executed
│ │ │ │  since the value of the first argument is 3 (not 0) (first clause head is
│ │ │ │ -<code class="inline">ping(0,Pong_PID)</code>, second clause head is <code class="inline">ping(N,Pong_PID)</code>, so <code class="inline">N</code> becomes 3).</p><p>The second clause sends a message to &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6411850169-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6411850169-2">(</span><span class="p" data-group-id="6411850169-2">)</span><span class="p" data-group-id="6411850169-1">}</span><span class="p">,</span></code></pre><p><a href="../../../lib/../erts/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a> returns the pid of the process that executes <a href="../../../lib/../erts/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a>, in this case the
│ │ │ │ +<code class="inline">ping(0,Pong_PID)</code>, second clause head is <code class="inline">ping(N,Pong_PID)</code>, so <code class="inline">N</code> becomes 3).</p><p>The second clause sends a message to &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9281660715-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9281660715-2">(</span><span class="p" data-group-id="9281660715-2">)</span><span class="p" data-group-id="9281660715-1">}</span><span class="p">,</span></code></pre><p><a href="../../../lib/../erts/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a> returns the pid of the process that executes <a href="../../../lib/../erts/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a>, in this case the
│ │ │ │  pid of &quot;ping&quot;. (Recall the code for &quot;pong&quot;, this ends up in the variable
│ │ │ │  <code class="inline">Ping_PID</code> in the <code class="inline">receive</code> previously explained.)</p><p>&quot;Ping&quot; now waits for a reply from &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │      </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9689612930-1">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9689612930-2">[</span><span class="p" data-group-id="9689612930-2">]</span><span class="p" data-group-id="9689612930-1">)</span><span class="w">
│ │ │ │ +        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3583125445-1">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3583125445-2">[</span><span class="p" data-group-id="3583125445-2">]</span><span class="p" data-group-id="3583125445-1">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">,</span></code></pre><p>It writes &quot;Ping received pong&quot; when this reply arrives, after which &quot;ping&quot; calls
│ │ │ │ -the <code class="inline">ping</code> function again.</p><pre><code class="makeup erlang" translate="no"><span class="nf">ping</span><span class="p" data-group-id="3999230844-1">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="3999230844-1">)</span></code></pre><p><code class="inline">N-1</code> causes the first argument to be decremented until it becomes 0. When this
│ │ │ │ -occurs, the first clause of <code class="inline">ping/2</code> is executed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">ping</span><span class="p" data-group-id="5956752562-1">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="5956752562-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +the <code class="inline">ping</code> function again.</p><pre><code class="makeup erlang" translate="no"><span class="nf">ping</span><span class="p" data-group-id="9771538747-1">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="9771538747-1">)</span></code></pre><p><code class="inline">N-1</code> causes the first argument to be decremented until it becomes 0. When this
│ │ │ │ +occurs, the first clause of <code class="inline">ping/2</code> is executed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">ping</span><span class="p" data-group-id="3109177810-1">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="3109177810-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w">  </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5956752562-2">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5956752562-3">[</span><span class="p" data-group-id="5956752562-3">]</span><span class="p" data-group-id="5956752562-2">)</span><span class="p">;</span></code></pre><p>The atom <code class="inline">finished</code> is sent to &quot;pong&quot; (causing it to terminate as described
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3109177810-2">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3109177810-3">[</span><span class="p" data-group-id="3109177810-3">]</span><span class="p" data-group-id="3109177810-2">)</span><span class="p">;</span></code></pre><p>The atom <code class="inline">finished</code> is sent to &quot;pong&quot; (causing it to terminate as described
│ │ │ │  above) and &quot;ping finished&quot; is written to the output. &quot;Ping&quot; then terminates as
│ │ │ │  it has nothing left to do.</p><h2 id="registered-process-names" class="section-heading">
│ │ │ │    <a href="#registered-process-names" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Registered Process Names</span>
│ │ │ │  </h2>
│ │ │ │  <p>In the above example, &quot;pong&quot; was first created to be able to give the identity
│ │ │ │  of &quot;pong&quot; when &quot;ping&quot; was started. That is, in some way &quot;ping&quot; must be able to
│ │ │ │  know the identity of &quot;pong&quot; to be able to send a message to it. Sometimes
│ │ │ │  processes which need to know each other's identities are started independently
│ │ │ │  of each other. Erlang thus provides a mechanism for processes to be given names
│ │ │ │  so that these names can be used as identities instead of pids. This is done by
│ │ │ │ -using the <code class="inline">register</code> BIF:</p><pre><code class="makeup erlang" translate="no"><span class="nf">register</span><span class="p" data-group-id="3708739197-1">(</span><span class="ss">some_atom</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="3708739197-1">)</span></code></pre><p>Let us now rewrite the ping pong example using this and give the name <code class="inline">pong</code> to
│ │ │ │ -the &quot;pong&quot; process:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8094814582-1">(</span><span class="ss">tut16</span><span class="p" data-group-id="8094814582-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +using the <code class="inline">register</code> BIF:</p><pre><code class="makeup erlang" translate="no"><span class="nf">register</span><span class="p" data-group-id="1851051136-1">(</span><span class="ss">some_atom</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="1851051136-1">)</span></code></pre><p>Let us now rewrite the ping pong example using this and give the name <code class="inline">pong</code> to
│ │ │ │ +the &quot;pong&quot; process:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0318489548-1">(</span><span class="ss">tut16</span><span class="p" data-group-id="0318489548-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8094814582-2">(</span><span class="p" data-group-id="8094814582-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8094814582-3">]</span><span class="p" data-group-id="8094814582-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0318489548-2">(</span><span class="p" data-group-id="0318489548-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0318489548-3">]</span><span class="p" data-group-id="0318489548-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="8094814582-4">(</span><span class="mi">0</span><span class="p" data-group-id="8094814582-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="0318489548-4">(</span><span class="mi">0</span><span class="p" data-group-id="0318489548-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8094814582-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8094814582-6">[</span><span class="p" data-group-id="8094814582-6">]</span><span class="p" data-group-id="8094814582-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0318489548-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0318489548-6">[</span><span class="p" data-group-id="0318489548-6">]</span><span class="p" data-group-id="0318489548-5">)</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="8094814582-7">(</span><span class="n">N</span><span class="p" data-group-id="8094814582-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8094814582-8">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8094814582-9">(</span><span class="p" data-group-id="8094814582-9">)</span><span class="p" data-group-id="8094814582-8">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="0318489548-7">(</span><span class="n">N</span><span class="p" data-group-id="0318489548-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0318489548-8">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0318489548-9">(</span><span class="p" data-group-id="0318489548-9">)</span><span class="p" data-group-id="0318489548-8">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8094814582-10">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8094814582-11">[</span><span class="p" data-group-id="8094814582-11">]</span><span class="p" data-group-id="8094814582-10">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0318489548-10">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0318489548-11">[</span><span class="p" data-group-id="0318489548-11">]</span><span class="p" data-group-id="0318489548-10">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="8094814582-12">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="8094814582-12">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="0318489548-12">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="0318489548-12">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="8094814582-13">(</span><span class="p" data-group-id="8094814582-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="0318489548-13">(</span><span class="p" data-group-id="0318489548-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8094814582-14">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8094814582-15">[</span><span class="p" data-group-id="8094814582-15">]</span><span class="p" data-group-id="8094814582-14">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8094814582-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="8094814582-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8094814582-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8094814582-18">[</span><span class="p" data-group-id="8094814582-18">]</span><span class="p" data-group-id="8094814582-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0318489548-14">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0318489548-15">[</span><span class="p" data-group-id="0318489548-15">]</span><span class="p" data-group-id="0318489548-14">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0318489548-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="0318489548-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0318489548-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0318489548-18">[</span><span class="p" data-group-id="0318489548-18">]</span><span class="p" data-group-id="0318489548-17">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="8094814582-19">(</span><span class="p" data-group-id="8094814582-19">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="0318489548-19">(</span><span class="p" data-group-id="0318489548-19">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="8094814582-20">(</span><span class="p" data-group-id="8094814582-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="8094814582-21">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="8094814582-22">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8094814582-23">[</span><span class="p" data-group-id="8094814582-23">]</span><span class="p" data-group-id="8094814582-22">)</span><span class="p" data-group-id="8094814582-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="8094814582-24">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8094814582-25">[</span><span class="mi">3</span><span class="p" data-group-id="8094814582-25">]</span><span class="p" data-group-id="8094814582-24">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nf">c</span><span class="p" data-group-id="5627371475-1">(</span><span class="ss">tut16</span><span class="p" data-group-id="5627371475-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5627371475-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut16</span><span class="p" data-group-id="5627371475-2">}</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">tut16</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="5627371475-3">(</span><span class="p" data-group-id="5627371475-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="0318489548-20">(</span><span class="p" data-group-id="0318489548-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="0318489548-21">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="0318489548-22">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0318489548-23">[</span><span class="p" data-group-id="0318489548-23">]</span><span class="p" data-group-id="0318489548-22">)</span><span class="p" data-group-id="0318489548-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="0318489548-24">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0318489548-25">[</span><span class="mi">3</span><span class="p" data-group-id="0318489548-25">]</span><span class="p" data-group-id="0318489548-24">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nf">c</span><span class="p" data-group-id="7568984779-1">(</span><span class="ss">tut16</span><span class="p" data-group-id="7568984779-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7568984779-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut16</span><span class="p" data-group-id="7568984779-2">}</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">tut16</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="7568984779-3">(</span><span class="p" data-group-id="7568984779-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">0.38</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="ss">ping</span><span class="w"> </span><span class="ss">finished</span><span class="w">
│ │ │ │ -</span><span class="n">Pong</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>Here the <code class="inline">start/0</code> function,</p><pre><code class="makeup erlang" translate="no"><span class="nf">register</span><span class="p" data-group-id="3861584926-1">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="3861584926-2">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3861584926-3">[</span><span class="p" data-group-id="3861584926-3">]</span><span class="p" data-group-id="3861584926-2">)</span><span class="p" data-group-id="3861584926-1">)</span><span class="p">,</span></code></pre><p>both spawns the &quot;pong&quot; process and gives it the name <code class="inline">pong</code>. In the &quot;ping&quot;
│ │ │ │ -process, messages can be sent to <code class="inline">pong</code> by:</p><pre><code class="makeup erlang" translate="no"><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0649562872-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0649562872-2">(</span><span class="p" data-group-id="0649562872-2">)</span><span class="p" data-group-id="0649562872-1">}</span><span class="p">,</span></code></pre><p><code class="inline">ping/2</code> now becomes <code class="inline">ping/1</code> as the argument <code class="inline">Pong_PID</code> is not needed.</p><h2 id="distributed-programming" class="section-heading">
│ │ │ │ +</span><span class="n">Pong</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>Here the <code class="inline">start/0</code> function,</p><pre><code class="makeup erlang" translate="no"><span class="nf">register</span><span class="p" data-group-id="0163823495-1">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="0163823495-2">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0163823495-3">[</span><span class="p" data-group-id="0163823495-3">]</span><span class="p" data-group-id="0163823495-2">)</span><span class="p" data-group-id="0163823495-1">)</span><span class="p">,</span></code></pre><p>both spawns the &quot;pong&quot; process and gives it the name <code class="inline">pong</code>. In the &quot;ping&quot;
│ │ │ │ +process, messages can be sent to <code class="inline">pong</code> by:</p><pre><code class="makeup erlang" translate="no"><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8824556171-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8824556171-2">(</span><span class="p" data-group-id="8824556171-2">)</span><span class="p" data-group-id="8824556171-1">}</span><span class="p">,</span></code></pre><p><code class="inline">ping/2</code> now becomes <code class="inline">ping/1</code> as the argument <code class="inline">Pong_PID</code> is not needed.</p><h2 id="distributed-programming" class="section-heading">
│ │ │ │    <a href="#distributed-programming" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Distributed Programming</span>
│ │ │ │  </h2>
│ │ │ │  <p>Let us rewrite the ping pong program with &quot;ping&quot; and &quot;pong&quot; on different
│ │ │ │  computers. First a few things need to be set up to get this to work. The
│ │ │ │ @@ -255,106 +255,106 @@
│ │ │ │  of the file. This is a requirement.</p><p>When you start an Erlang system that is going to talk to other Erlang systems,
│ │ │ │  you must give it a name, for example:</p><pre><code class="text">$ erl -sname my_name</code></pre><p>We will see more details of this later. If you want to experiment with
│ │ │ │  distributed Erlang, but you only have one computer to work on, you can start two
│ │ │ │  separate Erlang systems on the same computer but give them different names. Each
│ │ │ │  Erlang system running on a computer is called an <em>Erlang node</em>.</p><p>(Note: <code class="inline">erl -sname</code> assumes that all nodes are in the same IP domain and we can
│ │ │ │  use only the first component of the IP address, if we want to use nodes in
│ │ │ │  different domains we use <code class="inline">-name</code> instead, but then all IP addresses must be given
│ │ │ │ -in full.)</p><p>Here is the ping pong example modified to run on two separate nodes:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6663796437-1">(</span><span class="ss">tut17</span><span class="p" data-group-id="6663796437-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +in full.)</p><p>Here is the ping pong example modified to run on two separate nodes:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3809763109-1">(</span><span class="ss">tut17</span><span class="p" data-group-id="3809763109-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6663796437-2">(</span><span class="p" data-group-id="6663796437-3">[</span><span class="ss">start_ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">start_pong</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6663796437-3">]</span><span class="p" data-group-id="6663796437-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3809763109-2">(</span><span class="p" data-group-id="3809763109-3">[</span><span class="ss">start_ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">start_pong</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3809763109-3">]</span><span class="p" data-group-id="3809763109-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="6663796437-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="6663796437-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6663796437-5">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="6663796437-5">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6663796437-6">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6663796437-7">[</span><span class="p" data-group-id="6663796437-7">]</span><span class="p" data-group-id="6663796437-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="3809763109-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="3809763109-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3809763109-5">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="3809763109-5">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3809763109-6">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3809763109-7">[</span><span class="p" data-group-id="3809763109-7">]</span><span class="p" data-group-id="3809763109-6">)</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="6663796437-8">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="6663796437-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6663796437-9">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="6663796437-9">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6663796437-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6663796437-11">(</span><span class="p" data-group-id="6663796437-11">)</span><span class="p" data-group-id="6663796437-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="3809763109-8">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="3809763109-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3809763109-9">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="3809763109-9">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3809763109-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3809763109-11">(</span><span class="p" data-group-id="3809763109-11">)</span><span class="p" data-group-id="3809763109-10">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6663796437-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6663796437-13">[</span><span class="p" data-group-id="6663796437-13">]</span><span class="p" data-group-id="6663796437-12">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3809763109-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3809763109-13">[</span><span class="p" data-group-id="3809763109-13">]</span><span class="p" data-group-id="3809763109-12">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="6663796437-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="6663796437-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="3809763109-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="3809763109-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="6663796437-15">(</span><span class="p" data-group-id="6663796437-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="3809763109-15">(</span><span class="p" data-group-id="3809763109-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6663796437-16">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6663796437-17">[</span><span class="p" data-group-id="6663796437-17">]</span><span class="p" data-group-id="6663796437-16">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6663796437-18">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="6663796437-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6663796437-19">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6663796437-20">[</span><span class="p" data-group-id="6663796437-20">]</span><span class="p" data-group-id="6663796437-19">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3809763109-16">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3809763109-17">[</span><span class="p" data-group-id="3809763109-17">]</span><span class="p" data-group-id="3809763109-16">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3809763109-18">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="3809763109-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3809763109-19">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3809763109-20">[</span><span class="p" data-group-id="3809763109-20">]</span><span class="p" data-group-id="3809763109-19">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="6663796437-21">(</span><span class="p" data-group-id="6663796437-21">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="3809763109-21">(</span><span class="p" data-group-id="3809763109-21">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_pong</span><span class="p" data-group-id="6663796437-22">(</span><span class="p" data-group-id="6663796437-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="6663796437-23">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="6663796437-24">(</span><span class="ss">tut17</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6663796437-25">[</span><span class="p" data-group-id="6663796437-25">]</span><span class="p" data-group-id="6663796437-24">)</span><span class="p" data-group-id="6663796437-23">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_pong</span><span class="p" data-group-id="3809763109-22">(</span><span class="p" data-group-id="3809763109-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="3809763109-23">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="3809763109-24">(</span><span class="ss">tut17</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3809763109-25">[</span><span class="p" data-group-id="3809763109-25">]</span><span class="p" data-group-id="3809763109-24">)</span><span class="p" data-group-id="3809763109-23">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_ping</span><span class="p" data-group-id="6663796437-26">(</span><span class="n">Pong_Node</span><span class="p" data-group-id="6663796437-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="6663796437-27">(</span><span class="ss">tut17</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6663796437-28">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="6663796437-28">]</span><span class="p" data-group-id="6663796437-27">)</span><span class="p">.</span></code></pre><p>Let us assume there are two computers called gollum and kosken. First a node is
│ │ │ │ +</span><span class="nf">start_ping</span><span class="p" data-group-id="3809763109-26">(</span><span class="n">Pong_Node</span><span class="p" data-group-id="3809763109-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="3809763109-27">(</span><span class="ss">tut17</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3809763109-28">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="3809763109-28">]</span><span class="p" data-group-id="3809763109-27">)</span><span class="p">.</span></code></pre><p>Let us assume there are two computers called gollum and kosken. First a node is
│ │ │ │  started on kosken, called ping, and then a node on gollum, called pong.</p><p>On kosken (on a Linux/UNIX system):</p><pre><code class="text">kosken$ erl -sname ping
│ │ │ │  Erlang/OTP 28 [erts-16.3] [source] [64-bit] [smp:16:16] [ds:16:16:10] [async-threads:1] [jit:ns]
│ │ │ │  
│ │ │ │  Eshell V16.3 (press Ctrl+G to abort, type help(). for help)
│ │ │ │  (ping@kosken)1&gt;</code></pre><p>On gollum:</p><pre><code class="text">gollum$ erl -sname pong
│ │ │ │  Erlang/OTP 28 [erts-16.3] [source] [64-bit] [smp:16:16] [ds:16:16:10] [async-threads:1] [jit:ns]
│ │ │ │  
│ │ │ │  Eshell V16.3 (press Ctrl+G to abort, type help(). for help)
│ │ │ │ -(pong@gollum)1&gt;</code></pre><p>Now the &quot;pong&quot; process on gollum is started:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)1&gt; </span><span class="nc">tut17</span><span class="p">:</span><span class="nf">start_pong</span><span class="p" data-group-id="6290596855-1">(</span><span class="p" data-group-id="6290596855-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +(pong@gollum)1&gt;</code></pre><p>Now the &quot;pong&quot; process on gollum is started:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)1&gt; </span><span class="nc">tut17</span><span class="p">:</span><span class="nf">start_pong</span><span class="p" data-group-id="6884430976-1">(</span><span class="p" data-group-id="6884430976-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span></code></pre><p>And the &quot;ping&quot; process on kosken is started (from the code above you can see
│ │ │ │  that a parameter of the <code class="inline">start_ping</code> function is the node name of the Erlang
│ │ │ │ -system where &quot;pong&quot; is running):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(ping@kosken)1&gt; </span><span class="nc">tut17</span><span class="p">:</span><span class="nf">start_ping</span><span class="p" data-group-id="1559420785-1">(</span><span class="ss">pong@gollum</span><span class="p" data-group-id="1559420785-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +system where &quot;pong&quot; is running):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(ping@kosken)1&gt; </span><span class="nc">tut17</span><span class="p">:</span><span class="nf">start_ping</span><span class="p" data-group-id="3110925570-1">(</span><span class="ss">pong@gollum</span><span class="p" data-group-id="3110925570-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">0.37</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="ss">ping</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>As shown, the ping pong program has run. On the &quot;pong&quot; side:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)2&gt; </span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="nf">finished</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9190336906-1">(</span><span class="ss">pong@gollum</span><span class="p" data-group-id="9190336906-1">)</span><span class="mi">2</span><span class="o">&gt;</span><span class="w"> </span></code></pre><p>Looking at the <code class="inline">tut17</code> code, you see that the <code class="inline">pong</code> function itself is
│ │ │ │ +</span><span class="p" data-group-id="4917508787-1">(</span><span class="ss">pong@gollum</span><span class="p" data-group-id="4917508787-1">)</span><span class="mi">2</span><span class="o">&gt;</span><span class="w"> </span></code></pre><p>Looking at the <code class="inline">tut17</code> code, you see that the <code class="inline">pong</code> function itself is
│ │ │ │  unchanged, the following lines work in the same way irrespective of on which
│ │ │ │ -node the &quot;ping&quot; process is executed:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8579337270-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="8579337270-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8579337270-2">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8579337270-3">[</span><span class="p" data-group-id="8579337270-3">]</span><span class="p" data-group-id="8579337270-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +node the &quot;ping&quot; process is executed:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8685085454-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="8685085454-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8685085454-2">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8685085454-3">[</span><span class="p" data-group-id="8685085454-3">]</span><span class="p" data-group-id="8685085454-2">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span></code></pre><p>Thus, Erlang pids contain information about where the process executes. So if
│ │ │ │  you know the pid of a process, the <code class="inline">!</code> operator can be used to send it a
│ │ │ │ -message disregarding if the process is on the same node or on a different node.</p><p>A difference is how messages are sent to a registered process on another node:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3556822742-1">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="3556822742-1">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3556822742-2">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3556822742-3">(</span><span class="p" data-group-id="3556822742-3">)</span><span class="p" data-group-id="3556822742-2">}</span><span class="p">,</span></code></pre><p>A tuple <code class="inline">{registered_name,node_name}</code> is used instead of just the
│ │ │ │ +message disregarding if the process is on the same node or on a different node.</p><p>A difference is how messages are sent to a registered process on another node:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1422721521-1">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="1422721521-1">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1422721521-2">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1422721521-3">(</span><span class="p" data-group-id="1422721521-3">)</span><span class="p" data-group-id="1422721521-2">}</span><span class="p">,</span></code></pre><p>A tuple <code class="inline">{registered_name,node_name}</code> is used instead of just the
│ │ │ │  <code class="inline">registered_name</code>.</p><p>In the previous example, &quot;ping&quot; and &quot;pong&quot; were started from the shells of two
│ │ │ │  separate Erlang nodes. <code class="inline">spawn</code> can also be used to start processes in other
│ │ │ │  nodes.</p><p>The next example is the ping pong program, yet again, but this time &quot;ping&quot; is
│ │ │ │ -started in another node:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2239386724-1">(</span><span class="ss">tut18</span><span class="p" data-group-id="2239386724-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +started in another node:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7182846946-1">(</span><span class="ss">tut18</span><span class="p" data-group-id="7182846946-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2239386724-2">(</span><span class="p" data-group-id="2239386724-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2239386724-3">]</span><span class="p" data-group-id="2239386724-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7182846946-2">(</span><span class="p" data-group-id="7182846946-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7182846946-3">]</span><span class="p" data-group-id="7182846946-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="2239386724-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2239386724-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2239386724-5">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2239386724-5">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2239386724-6">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2239386724-7">[</span><span class="p" data-group-id="2239386724-7">]</span><span class="p" data-group-id="2239386724-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="7182846946-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="7182846946-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7182846946-5">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="7182846946-5">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7182846946-6">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7182846946-7">[</span><span class="p" data-group-id="7182846946-7">]</span><span class="p" data-group-id="7182846946-6">)</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="2239386724-8">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2239386724-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2239386724-9">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2239386724-9">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2239386724-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2239386724-11">(</span><span class="p" data-group-id="2239386724-11">)</span><span class="p" data-group-id="2239386724-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="7182846946-8">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="7182846946-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7182846946-9">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="7182846946-9">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7182846946-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7182846946-11">(</span><span class="p" data-group-id="7182846946-11">)</span><span class="p" data-group-id="7182846946-10">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2239386724-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2239386724-13">[</span><span class="p" data-group-id="2239386724-13">]</span><span class="p" data-group-id="2239386724-12">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7182846946-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7182846946-13">[</span><span class="p" data-group-id="7182846946-13">]</span><span class="p" data-group-id="7182846946-12">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="2239386724-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2239386724-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="7182846946-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="7182846946-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="2239386724-15">(</span><span class="p" data-group-id="2239386724-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="7182846946-15">(</span><span class="p" data-group-id="7182846946-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2239386724-16">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2239386724-17">[</span><span class="p" data-group-id="2239386724-17">]</span><span class="p" data-group-id="2239386724-16">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="2239386724-18">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="2239386724-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2239386724-19">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2239386724-20">[</span><span class="p" data-group-id="2239386724-20">]</span><span class="p" data-group-id="2239386724-19">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7182846946-16">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7182846946-17">[</span><span class="p" data-group-id="7182846946-17">]</span><span class="p" data-group-id="7182846946-16">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="7182846946-18">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="7182846946-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7182846946-19">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7182846946-20">[</span><span class="p" data-group-id="7182846946-20">]</span><span class="p" data-group-id="7182846946-19">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="2239386724-21">(</span><span class="p" data-group-id="2239386724-21">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="7182846946-21">(</span><span class="p" data-group-id="7182846946-21">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="2239386724-22">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="2239386724-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="2239386724-23">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="2239386724-24">(</span><span class="ss">tut18</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2239386724-25">[</span><span class="p" data-group-id="2239386724-25">]</span><span class="p" data-group-id="2239386724-24">)</span><span class="p" data-group-id="2239386724-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="2239386724-26">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut18</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2239386724-27">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="nf">node</span><span class="p" data-group-id="2239386724-28">(</span><span class="p" data-group-id="2239386724-28">)</span><span class="p" data-group-id="2239386724-27">]</span><span class="p" data-group-id="2239386724-26">)</span><span class="p">.</span></code></pre><p>Assuming an Erlang system called ping (but not the &quot;ping&quot; process) has already
│ │ │ │ -been started on kosken, then on gollum this is done:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)1&gt; </span><span class="nc">tut18</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="7522262762-1">(</span><span class="ss">ping@kosken</span><span class="p" data-group-id="7522262762-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="7182846946-22">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="7182846946-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="7182846946-23">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="7182846946-24">(</span><span class="ss">tut18</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7182846946-25">[</span><span class="p" data-group-id="7182846946-25">]</span><span class="p" data-group-id="7182846946-24">)</span><span class="p" data-group-id="7182846946-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="7182846946-26">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut18</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7182846946-27">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="nf">node</span><span class="p" data-group-id="7182846946-28">(</span><span class="p" data-group-id="7182846946-28">)</span><span class="p" data-group-id="7182846946-27">]</span><span class="p" data-group-id="7182846946-26">)</span><span class="p">.</span></code></pre><p>Assuming an Erlang system called ping (but not the &quot;ping&quot; process) has already
│ │ │ │ +been started on kosken, then on gollum this is done:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)1&gt; </span><span class="nc">tut18</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="6858086643-1">(</span><span class="ss">ping@kosken</span><span class="p" data-group-id="6858086643-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">3934.39</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │ @@ -418,184 +418,184 @@
│ │ │ │  </span><span class="c1">%%% Started: messenger:client(Server_Node, Name)</span><span class="w">
│ │ │ │  </span><span class="c1">%%% To client: logoff</span><span class="w">
│ │ │ │  </span><span class="c1">%%% To client: {message_to, ToName, Message}</span><span class="w">
│ │ │ │  </span><span class="c1">%%%</span><span class="w">
│ │ │ │  </span><span class="c1">%%% Configuration: change the server_node() function to return the</span><span class="w">
│ │ │ │  </span><span class="c1">%%% name of the node where the messenger server runs</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1439152443-1">(</span><span class="ss">messenger</span><span class="p" data-group-id="1439152443-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1439152443-2">(</span><span class="p" data-group-id="1439152443-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1439152443-3">]</span><span class="p" data-group-id="1439152443-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8099063168-1">(</span><span class="ss">messenger</span><span class="p" data-group-id="8099063168-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8099063168-2">(</span><span class="p" data-group-id="8099063168-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8099063168-3">]</span><span class="p" data-group-id="8099063168-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Change the function below to return the name of the node where the</span><span class="w">
│ │ │ │  </span><span class="c1">%%% messenger server runs</span><span class="w">
│ │ │ │ -</span><span class="nf">server_node</span><span class="p" data-group-id="1439152443-4">(</span><span class="p" data-group-id="1439152443-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_node</span><span class="p" data-group-id="8099063168-4">(</span><span class="p" data-group-id="8099063168-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">messenger@super</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% This is the server process for the &quot;messenger&quot;</span><span class="w">
│ │ │ │  </span><span class="c1">%%% the user list has the format [{ClientPid1, Name1},{ClientPid2, Name2},...]</span><span class="w">
│ │ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="1439152443-5">(</span><span class="n">User_List</span><span class="p" data-group-id="1439152443-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="8099063168-5">(</span><span class="n">User_List</span><span class="p" data-group-id="8099063168-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1439152443-6">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1439152443-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="1439152443-7">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1439152443-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="1439152443-8">(</span><span class="n">New_User_List</span><span class="p" data-group-id="1439152443-8">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1439152443-9">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p" data-group-id="1439152443-9">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="1439152443-10">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1439152443-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="1439152443-11">(</span><span class="n">New_User_List</span><span class="p" data-group-id="1439152443-11">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1439152443-12">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1439152443-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="1439152443-13">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1439152443-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1439152443-14">(</span><span class="s">&quot;list is now: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1439152443-15">[</span><span class="n">User_List</span><span class="p" data-group-id="1439152443-15">]</span><span class="p" data-group-id="1439152443-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="1439152443-16">(</span><span class="n">User_List</span><span class="p" data-group-id="1439152443-16">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="8099063168-6">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="8099063168-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="8099063168-7">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="8099063168-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="8099063168-8">(</span><span class="n">New_User_List</span><span class="p" data-group-id="8099063168-8">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="8099063168-9">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p" data-group-id="8099063168-9">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="8099063168-10">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="8099063168-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="8099063168-11">(</span><span class="n">New_User_List</span><span class="p" data-group-id="8099063168-11">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="8099063168-12">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="8099063168-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="8099063168-13">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="8099063168-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8099063168-14">(</span><span class="s">&quot;list is now: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8099063168-15">[</span><span class="n">User_List</span><span class="p" data-group-id="8099063168-15">]</span><span class="p" data-group-id="8099063168-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="8099063168-16">(</span><span class="n">User_List</span><span class="p" data-group-id="8099063168-16">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Start the server</span><span class="w">
│ │ │ │ -</span><span class="nf">start_server</span><span class="p" data-group-id="1439152443-17">(</span><span class="p" data-group-id="1439152443-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="1439152443-18">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="1439152443-19">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1439152443-20">[</span><span class="p" data-group-id="1439152443-21">[</span><span class="p" data-group-id="1439152443-21">]</span><span class="p" data-group-id="1439152443-20">]</span><span class="p" data-group-id="1439152443-19">)</span><span class="p" data-group-id="1439152443-18">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_server</span><span class="p" data-group-id="8099063168-17">(</span><span class="p" data-group-id="8099063168-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="8099063168-18">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="8099063168-19">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8099063168-20">[</span><span class="p" data-group-id="8099063168-21">[</span><span class="p" data-group-id="8099063168-21">]</span><span class="p" data-group-id="8099063168-20">]</span><span class="p" data-group-id="8099063168-19">)</span><span class="p" data-group-id="8099063168-18">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server adds a new user to the user list</span><span class="w">
│ │ │ │ -</span><span class="nf">server_logon</span><span class="p" data-group-id="1439152443-22">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1439152443-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_logon</span><span class="p" data-group-id="8099063168-22">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="8099063168-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% check if logged on anywhere else</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="1439152443-23">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1439152443-23">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="8099063168-23">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="8099063168-23">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1439152443-24">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="1439152443-24">}</span><span class="p">,</span><span class="w">  </span><span class="c1">%reject logon</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8099063168-24">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="8099063168-24">}</span><span class="p">,</span><span class="w">  </span><span class="c1">%reject logon</span><span class="w">
│ │ │ │              </span><span class="n">User_List</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1439152443-25">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">logged_on</span><span class="p" data-group-id="1439152443-25">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="1439152443-26">[</span><span class="p" data-group-id="1439152443-27">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1439152443-27">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1439152443-26">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8099063168-25">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">logged_on</span><span class="p" data-group-id="8099063168-25">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="8099063168-26">[</span><span class="p" data-group-id="8099063168-27">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="8099063168-27">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="8099063168-26">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server deletes a user from the user list</span><span class="w">
│ │ │ │ -</span><span class="nf">server_logoff</span><span class="p" data-group-id="1439152443-28">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1439152443-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="1439152443-29">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1439152443-29">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">server_logoff</span><span class="p" data-group-id="8099063168-28">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="8099063168-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="8099063168-29">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="8099063168-29">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server transfers a message between users</span><span class="w">
│ │ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="1439152443-30">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1439152443-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="8099063168-30">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="8099063168-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% check that the user is logged on and who he is</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="1439152443-31">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1439152443-31">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="8099063168-31">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="8099063168-31">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1439152443-32">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="1439152443-32">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1439152443-33">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1439152443-33">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="1439152443-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1439152443-34">)</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8099063168-32">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="8099063168-32">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="8099063168-33">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="8099063168-33">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="8099063168-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="8099063168-34">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%% If the user exists, send the message</span><span class="w">
│ │ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="1439152443-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1439152443-35">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="8099063168-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="8099063168-35">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Find the receiver and send the message</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="1439152443-36">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1439152443-36">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="8099063168-36">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="8099063168-36">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1439152443-37">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="1439152443-37">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1439152443-38">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="1439152443-38">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1439152443-39">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1439152443-39">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1439152443-40">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="1439152443-40">}</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8099063168-37">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="8099063168-37">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="8099063168-38">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="8099063168-38">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8099063168-39">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="8099063168-39">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8099063168-40">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="8099063168-40">}</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% User Commands</span><span class="w">
│ │ │ │ -</span><span class="nf">logon</span><span class="p" data-group-id="1439152443-41">(</span><span class="n">Name</span><span class="p" data-group-id="1439152443-41">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="1439152443-42">(</span><span class="ss">mess_client</span><span class="p" data-group-id="1439152443-42">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">logon</span><span class="p" data-group-id="8099063168-41">(</span><span class="n">Name</span><span class="p" data-group-id="8099063168-41">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="8099063168-42">(</span><span class="ss">mess_client</span><span class="p" data-group-id="8099063168-42">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">register</span><span class="p" data-group-id="1439152443-43">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ │ -                     </span><span class="nf">spawn</span><span class="p" data-group-id="1439152443-44">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1439152443-45">[</span><span class="nf">server_node</span><span class="p" data-group-id="1439152443-46">(</span><span class="p" data-group-id="1439152443-46">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1439152443-45">]</span><span class="p" data-group-id="1439152443-44">)</span><span class="p" data-group-id="1439152443-43">)</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="nf">register</span><span class="p" data-group-id="8099063168-43">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ │ +                     </span><span class="nf">spawn</span><span class="p" data-group-id="8099063168-44">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8099063168-45">[</span><span class="nf">server_node</span><span class="p" data-group-id="8099063168-46">(</span><span class="p" data-group-id="8099063168-46">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="8099063168-45">]</span><span class="p" data-group-id="8099063168-44">)</span><span class="p" data-group-id="8099063168-43">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">already_logged_on</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">logoff</span><span class="p" data-group-id="1439152443-47">(</span><span class="p" data-group-id="1439152443-47">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">logoff</span><span class="p" data-group-id="8099063168-47">(</span><span class="p" data-group-id="8099063168-47">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">logoff</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">message</span><span class="p" data-group-id="1439152443-48">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1439152443-48">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="1439152443-49">(</span><span class="ss">mess_client</span><span class="p" data-group-id="1439152443-49">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ │ +</span><span class="nf">message</span><span class="p" data-group-id="8099063168-48">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="8099063168-48">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="8099063168-49">(</span><span class="ss">mess_client</span><span class="p" data-group-id="8099063168-49">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">not_logged_on</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1439152443-50">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1439152443-50">}</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8099063168-50">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="8099063168-50">}</span><span class="p">,</span><span class="w">
│ │ │ │               </span><span class="ss">ok</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% The client process which runs on each server node</span><span class="w">
│ │ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="1439152443-51">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1439152443-51">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1439152443-52">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="1439152443-52">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1439152443-53">{</span><span class="nf">self</span><span class="p" data-group-id="1439152443-54">(</span><span class="p" data-group-id="1439152443-54">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1439152443-53">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">await_result</span><span class="p" data-group-id="1439152443-55">(</span><span class="p" data-group-id="1439152443-55">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="1439152443-56">(</span><span class="n">Server_Node</span><span class="p" data-group-id="1439152443-56">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="8099063168-51">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="8099063168-51">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8099063168-52">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="8099063168-52">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8099063168-53">{</span><span class="nf">self</span><span class="p" data-group-id="8099063168-54">(</span><span class="p" data-group-id="8099063168-54">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="8099063168-53">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">await_result</span><span class="p" data-group-id="8099063168-55">(</span><span class="p" data-group-id="8099063168-55">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="8099063168-56">(</span><span class="n">Server_Node</span><span class="p" data-group-id="8099063168-56">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="1439152443-57">(</span><span class="n">Server_Node</span><span class="p" data-group-id="1439152443-57">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="8099063168-57">(</span><span class="n">Server_Node</span><span class="p" data-group-id="8099063168-57">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">logoff</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="1439152443-58">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="1439152443-58">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1439152443-59">{</span><span class="nf">self</span><span class="p" data-group-id="1439152443-60">(</span><span class="p" data-group-id="1439152443-60">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p" data-group-id="1439152443-59">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="1439152443-61">(</span><span class="ss">normal</span><span class="p" data-group-id="1439152443-61">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1439152443-62">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1439152443-62">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="1439152443-63">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="1439152443-63">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1439152443-64">{</span><span class="nf">self</span><span class="p" data-group-id="1439152443-65">(</span><span class="p" data-group-id="1439152443-65">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1439152443-64">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">await_result</span><span class="p" data-group-id="1439152443-66">(</span><span class="p" data-group-id="1439152443-66">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1439152443-67">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1439152443-67">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1439152443-68">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1439152443-69">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1439152443-69">]</span><span class="p" data-group-id="1439152443-68">)</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="8099063168-58">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="8099063168-58">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8099063168-59">{</span><span class="nf">self</span><span class="p" data-group-id="8099063168-60">(</span><span class="p" data-group-id="8099063168-60">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p" data-group-id="8099063168-59">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="8099063168-61">(</span><span class="ss">normal</span><span class="p" data-group-id="8099063168-61">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="8099063168-62">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="8099063168-62">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="8099063168-63">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="8099063168-63">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8099063168-64">{</span><span class="nf">self</span><span class="p" data-group-id="8099063168-65">(</span><span class="p" data-group-id="8099063168-65">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="8099063168-64">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">await_result</span><span class="p" data-group-id="8099063168-66">(</span><span class="p" data-group-id="8099063168-66">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="8099063168-67">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="8099063168-67">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8099063168-68">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8099063168-69">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="8099063168-69">]</span><span class="p" data-group-id="8099063168-68">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="1439152443-70">(</span><span class="n">Server_Node</span><span class="p" data-group-id="1439152443-70">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="8099063168-70">(</span><span class="n">Server_Node</span><span class="p" data-group-id="8099063168-70">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% wait for a response from the server</span><span class="w">
│ │ │ │ -</span><span class="nf">await_result</span><span class="p" data-group-id="1439152443-71">(</span><span class="p" data-group-id="1439152443-71">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">await_result</span><span class="p" data-group-id="8099063168-71">(</span><span class="p" data-group-id="8099063168-71">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1439152443-72">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">Why</span><span class="p" data-group-id="1439152443-72">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Stop the client</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1439152443-73">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1439152443-74">[</span><span class="n">Why</span><span class="p" data-group-id="1439152443-74">]</span><span class="p" data-group-id="1439152443-73">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="1439152443-75">(</span><span class="ss">normal</span><span class="p" data-group-id="1439152443-75">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1439152443-76">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">What</span><span class="p" data-group-id="1439152443-76">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Normal response</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1439152443-77">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1439152443-78">[</span><span class="n">What</span><span class="p" data-group-id="1439152443-78">]</span><span class="p" data-group-id="1439152443-77">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="8099063168-72">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">Why</span><span class="p" data-group-id="8099063168-72">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Stop the client</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8099063168-73">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8099063168-74">[</span><span class="n">Why</span><span class="p" data-group-id="8099063168-74">]</span><span class="p" data-group-id="8099063168-73">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="8099063168-75">(</span><span class="ss">normal</span><span class="p" data-group-id="8099063168-75">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="8099063168-76">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">What</span><span class="p" data-group-id="8099063168-76">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Normal response</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8099063168-77">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8099063168-78">[</span><span class="n">What</span><span class="p" data-group-id="8099063168-78">]</span><span class="p" data-group-id="8099063168-77">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>To use this program, you need to:</p><ul><li>Configure the <code class="inline">server_node()</code> function.</li><li>Copy the compiled code (<code class="inline">messenger.beam</code>) to the directory on each computer
│ │ │ │  where you start Erlang.</li></ul><p>In the following example using this program, nodes are started on four different
│ │ │ │  computers. If you do not have that many machines available on your network, you
│ │ │ │  can start several nodes on the same machine.</p><p>Four Erlang nodes are started up: messenger@super, c1@bilbo, c2@kosken,
│ │ │ │ -c3@gollum.</p><p>First the server at messenger@super is started up:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(messenger@super)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">start_server</span><span class="p" data-group-id="9799189527-1">(</span><span class="p" data-group-id="9799189527-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="ss">true</span></code></pre><p>Now Peter logs on at c1@bilbo:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c1@bilbo)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="3918620874-1">(</span><span class="ss">peter</span><span class="p" data-group-id="3918620874-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +c3@gollum.</p><p>First the server at messenger@super is started up:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(messenger@super)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">start_server</span><span class="p" data-group-id="2087063031-1">(</span><span class="p" data-group-id="2087063031-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">true</span></code></pre><p>Now Peter logs on at c1@bilbo:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c1@bilbo)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="8219928174-1">(</span><span class="ss">peter</span><span class="p" data-group-id="8219928174-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="ss">logged_on</span></code></pre><p>James logs on at c2@kosken:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c2@kosken)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="2252233694-1">(</span><span class="ss">james</span><span class="p" data-group-id="2252233694-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">logged_on</span></code></pre><p>James logs on at c2@kosken:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c2@kosken)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="5045589147-1">(</span><span class="ss">james</span><span class="p" data-group-id="5045589147-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="ss">logged_on</span></code></pre><p>And Fred logs on at c3@gollum:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c3@gollum)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="3382060610-1">(</span><span class="ss">fred</span><span class="p" data-group-id="3382060610-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">logged_on</span></code></pre><p>And Fred logs on at c3@gollum:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c3@gollum)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="7194697700-1">(</span><span class="ss">fred</span><span class="p" data-group-id="7194697700-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="ss">logged_on</span></code></pre><p>Now Peter sends Fred a message:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c1@bilbo)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="8008822732-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="8008822732-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">logged_on</span></code></pre><p>Now Peter sends Fred a message:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c1@bilbo)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="3738478821-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="3738478821-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │  </span><span class="ss">sent</span></code></pre><p>Fred receives the message and sends a message to Peter and logs off:</p><pre><code class="makeup erlang" translate="no"><span class="n">Message</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="nc">peter</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">(c3@gollum)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="6943606287-1">(</span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;go away, I&#39;m busy&quot;</span><span class="p" data-group-id="6943606287-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">(c3@gollum)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="7914909702-1">(</span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;go away, I&#39;m busy&quot;</span><span class="p" data-group-id="7914909702-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │  </span><span class="nf">sent</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6943606287-2">(</span><span class="ss">c3@gollum</span><span class="p" data-group-id="6943606287-2">)</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logoff</span><span class="p" data-group-id="6943606287-3">(</span><span class="p" data-group-id="6943606287-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="ss">logoff</span></code></pre><p>James now tries to send a message to Fred:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c2@kosken)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="0354739699-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;peter doesn&#39;t like you&quot;</span><span class="p" data-group-id="0354739699-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7914909702-2">(</span><span class="ss">c3@gollum</span><span class="p" data-group-id="7914909702-2">)</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logoff</span><span class="p" data-group-id="7914909702-3">(</span><span class="p" data-group-id="7914909702-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">logoff</span></code></pre><p>James now tries to send a message to Fred:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c2@kosken)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="3209848006-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;peter doesn&#39;t like you&quot;</span><span class="p" data-group-id="3209848006-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │  </span><span class="ss">receiver_not_found</span></code></pre><p>But this fails as Fred has already logged off.</p><p>First let us look at some of the new concepts that have been introduced.</p><p>There are two versions of the <code class="inline">server_transfer</code> function: one with four
│ │ │ │  arguments (<code class="inline">server_transfer/4</code>) and one with five (<code class="inline">server_transfer/5</code>). These
│ │ │ │  are regarded by Erlang as two separate functions.</p><p>Notice how to write the <code class="inline">server</code> function so that it calls itself, through
│ │ │ │  <code class="inline">server(User_List)</code>, and thus creates a loop. The Erlang compiler is &quot;clever&quot;
│ │ │ │  and optimizes the code so that this really is a sort of loop and not a proper
│ │ │ │  function call. But this only works if there is no code after the call.
│ │ │ │  Otherwise, the compiler expects the call to return and make a proper function
│ │ │ │  call. This would result in the process getting bigger and bigger for every loop.</p><p>Functions in the <code class="inline">lists</code> module are used. This is a very useful module and a
│ │ │ │  study of the manual page is recommended (<code class="inline">erl -man lists</code>).
│ │ │ │  <code class="inline">lists:keymember(Key,Position,List)</code> looks through a list of tuples and looks
│ │ │ │  at <code class="inline">Position</code> in each tuple to see if it is the same as <code class="inline">Key</code>. The first element
│ │ │ │  is position 1. If it finds a tuple where the element at <code class="inline">Position</code> is the same
│ │ │ │ -as <code class="inline">Key</code>, it returns <code class="inline">true</code>, otherwise <code class="inline">false</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="9805964018-1">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9805964018-2">[</span><span class="p" data-group-id="9805964018-3">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="9805964018-3">}</span><span class="p">,</span><span class="p" data-group-id="9805964018-4">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9805964018-4">}</span><span class="p">,</span><span class="p" data-group-id="9805964018-5">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="9805964018-5">}</span><span class="p">,</span><span class="p" data-group-id="9805964018-6">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="9805964018-6">}</span><span class="p" data-group-id="9805964018-2">]</span><span class="p" data-group-id="9805964018-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +as <code class="inline">Key</code>, it returns <code class="inline">true</code>, otherwise <code class="inline">false</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="6126116906-1">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6126116906-2">[</span><span class="p" data-group-id="6126116906-3">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="6126116906-3">}</span><span class="p">,</span><span class="p" data-group-id="6126116906-4">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6126116906-4">}</span><span class="p">,</span><span class="p" data-group-id="6126116906-5">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6126116906-5">}</span><span class="p">,</span><span class="p" data-group-id="6126116906-6">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="6126116906-6">}</span><span class="p" data-group-id="6126116906-2">]</span><span class="p" data-group-id="6126116906-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="9805964018-7">(</span><span class="ss">p</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9805964018-8">[</span><span class="p" data-group-id="9805964018-9">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="9805964018-9">}</span><span class="p">,</span><span class="p" data-group-id="9805964018-10">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9805964018-10">}</span><span class="p">,</span><span class="p" data-group-id="9805964018-11">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="9805964018-11">}</span><span class="p">,</span><span class="p" data-group-id="9805964018-12">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="9805964018-12">}</span><span class="p" data-group-id="9805964018-8">]</span><span class="p" data-group-id="9805964018-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="6126116906-7">(</span><span class="ss">p</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6126116906-8">[</span><span class="p" data-group-id="6126116906-9">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="6126116906-9">}</span><span class="p">,</span><span class="p" data-group-id="6126116906-10">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6126116906-10">}</span><span class="p">,</span><span class="p" data-group-id="6126116906-11">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6126116906-11">}</span><span class="p">,</span><span class="p" data-group-id="6126116906-12">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="6126116906-12">}</span><span class="p" data-group-id="6126116906-8">]</span><span class="p" data-group-id="6126116906-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span></code></pre><p><code class="inline">lists:keydelete</code> works in the same way but deletes the first tuple found (if
│ │ │ │ -any) and returns the remaining list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="9726770533-1">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9726770533-2">[</span><span class="p" data-group-id="9726770533-3">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="9726770533-3">}</span><span class="p">,</span><span class="p" data-group-id="9726770533-4">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9726770533-4">}</span><span class="p">,</span><span class="p" data-group-id="9726770533-5">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="9726770533-5">}</span><span class="p">,</span><span class="p" data-group-id="9726770533-6">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="9726770533-6">}</span><span class="p" data-group-id="9726770533-2">]</span><span class="p" data-group-id="9726770533-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9726770533-7">[</span><span class="p" data-group-id="9726770533-8">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="9726770533-8">}</span><span class="p">,</span><span class="p" data-group-id="9726770533-9">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9726770533-9">}</span><span class="p">,</span><span class="p" data-group-id="9726770533-10">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="9726770533-10">}</span><span class="p" data-group-id="9726770533-7">]</span></code></pre><p><code class="inline">lists:keyfind</code> is like <code class="inline">lists:keymember</code>, but it returns
│ │ │ │ +any) and returns the remaining list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="3677758764-1">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3677758764-2">[</span><span class="p" data-group-id="3677758764-3">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="3677758764-3">}</span><span class="p">,</span><span class="p" data-group-id="3677758764-4">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3677758764-4">}</span><span class="p">,</span><span class="p" data-group-id="3677758764-5">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3677758764-5">}</span><span class="p">,</span><span class="p" data-group-id="3677758764-6">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="3677758764-6">}</span><span class="p" data-group-id="3677758764-2">]</span><span class="p" data-group-id="3677758764-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3677758764-7">[</span><span class="p" data-group-id="3677758764-8">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="3677758764-8">}</span><span class="p">,</span><span class="p" data-group-id="3677758764-9">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3677758764-9">}</span><span class="p">,</span><span class="p" data-group-id="3677758764-10">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="3677758764-10">}</span><span class="p" data-group-id="3677758764-7">]</span></code></pre><p><code class="inline">lists:keyfind</code> is like <code class="inline">lists:keymember</code>, but it returns
│ │ │ │  <code class="inline">Tuple_Found</code> or the atom <code class="inline">false</code>.</p><p>There are many very useful functions in the <code class="inline">lists</code> module.</p><p>An Erlang process (conceptually) runs until it does a <code class="inline">receive</code> and there is no
│ │ │ │  message which it wants to receive in the message queue. &quot;conceptually&quot; is used
│ │ │ │  here because the Erlang system shares the CPU time between the active processes
│ │ │ │  in the system.</p><p>A process terminates when there is nothing more for it to do, that is, the last
│ │ │ │  function it calls simply returns and does not call another function. Another way
│ │ │ │  for a process to terminate is for it to call <a href="../../../lib/../erts/doc/html/erlang.html#exit/1"><code class="inline">exit/1</code></a>. The argument
│ │ │ │  to <a href="../../../lib/../erts/doc/html/erlang.html#exit/1"><code class="inline">exit/1</code></a> has a special meaning, which is discussed later. In this
│ │ │ │  example, <a href="../../../lib/../erts/doc/html/erlang.html#exit/1"><code class="inline">exit(normal)</code></a> is done, which has the same effect as a
│ │ │ │  process running out of functions to call.</p><p>The BIF <a href="../../../lib/../erts/doc/html/erlang.html#whereis/1"><code class="inline">whereis(RegisteredName)</code></a> checks if a registered process
│ │ │ │  of name <code class="inline">RegisteredName</code> exists. If it exists, the pid of that process is
│ │ │ │  returned. If it does not exist, the atom <code class="inline">undefined</code> is returned.</p><p>You should by now be able to understand most of the code in the
│ │ │ │  messenger-module. Let us study one case in detail: a message is sent from one
│ │ │ │ -user to another.</p><p>The first user &quot;sends&quot; the message in the example above by:</p><pre><code class="makeup erlang" translate="no"><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="6373294795-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="6373294795-1">)</span></code></pre><p>After testing that the client process exists:</p><pre><code class="makeup erlang" translate="no"><span class="nf">whereis</span><span class="p" data-group-id="9844885426-1">(</span><span class="ss">mess_client</span><span class="p" data-group-id="9844885426-1">)</span></code></pre><p>And a message is sent to <code class="inline">mess_client</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8739714393-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="8739714393-1">}</span></code></pre><p>The client sends the message to the server by:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4294623477-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="4294623477-1">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4294623477-2">{</span><span class="nf">self</span><span class="p" data-group-id="4294623477-3">(</span><span class="p" data-group-id="4294623477-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="4294623477-2">}</span><span class="p">,</span></code></pre><p>And waits for a reply from the server.</p><p>The server receives this message and calls:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server_transfer</span><span class="p" data-group-id="2513737873-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="2513737873-1">)</span><span class="p">,</span></code></pre><p>This checks that the pid <code class="inline">From</code> is in the <code class="inline">User_List</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="2358047069-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="2358047069-1">)</span></code></pre><p>If <code class="inline">keyfind</code> returns the atom <code class="inline">false</code>, some error has occurred and the server
│ │ │ │ -sends back the message:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7388170533-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="7388170533-1">}</span></code></pre><p>This is received by the client, which in turn does <a href="../../../lib/../erts/doc/html/erlang.html#exit/1"><code class="inline">exit(normal)</code></a>
│ │ │ │ +user to another.</p><p>The first user &quot;sends&quot; the message in the example above by:</p><pre><code class="makeup erlang" translate="no"><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="2883958996-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="2883958996-1">)</span></code></pre><p>After testing that the client process exists:</p><pre><code class="makeup erlang" translate="no"><span class="nf">whereis</span><span class="p" data-group-id="8521832954-1">(</span><span class="ss">mess_client</span><span class="p" data-group-id="8521832954-1">)</span></code></pre><p>And a message is sent to <code class="inline">mess_client</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3276359033-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="3276359033-1">}</span></code></pre><p>The client sends the message to the server by:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0510428506-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="0510428506-1">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0510428506-2">{</span><span class="nf">self</span><span class="p" data-group-id="0510428506-3">(</span><span class="p" data-group-id="0510428506-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="0510428506-2">}</span><span class="p">,</span></code></pre><p>And waits for a reply from the server.</p><p>The server receives this message and calls:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server_transfer</span><span class="p" data-group-id="1864175848-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1864175848-1">)</span><span class="p">,</span></code></pre><p>This checks that the pid <code class="inline">From</code> is in the <code class="inline">User_List</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="1615789716-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1615789716-1">)</span></code></pre><p>If <code class="inline">keyfind</code> returns the atom <code class="inline">false</code>, some error has occurred and the server
│ │ │ │ +sends back the message:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6155880733-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="6155880733-1">}</span></code></pre><p>This is received by the client, which in turn does <a href="../../../lib/../erts/doc/html/erlang.html#exit/1"><code class="inline">exit(normal)</code></a>
│ │ │ │  and terminates. If <code class="inline">keyfind</code> returns <code class="inline">{From,Name}</code> it is certain that
│ │ │ │ -the user is logged on and that their name (peter) is in the variable <code class="inline">Name</code>.</p><p>Let us now call:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server_transfer</span><span class="p" data-group-id="9572990893-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9572990893-1">)</span></code></pre><p>Notice that as this is <code class="inline">server_transfer/5</code>, it is not the same as the previous
│ │ │ │ +the user is logged on and that their name (peter) is in the variable <code class="inline">Name</code>.</p><p>Let us now call:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server_transfer</span><span class="p" data-group-id="9725367478-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9725367478-1">)</span></code></pre><p>Notice that as this is <code class="inline">server_transfer/5</code>, it is not the same as the previous
│ │ │ │  function <code class="inline">server_transfer/4</code>. Another <code class="inline">keyfind</code> is done on <code class="inline">User_List</code> to find
│ │ │ │ -the pid of the client corresponding to fred:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="1871808207-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1871808207-1">)</span></code></pre><p>This time argument 2 is used, which is the second element in the tuple. If this
│ │ │ │ +the pid of the client corresponding to fred:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="4703474997-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="4703474997-1">)</span></code></pre><p>This time argument 2 is used, which is the second element in the tuple. If this
│ │ │ │  returns the atom <code class="inline">false</code>, fred is not logged on and the following message is
│ │ │ │ -sent:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8367239470-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="8367239470-1">}</span><span class="p">;</span></code></pre><p>This is received by the client.</p><p>If <code class="inline">keyfind</code> returns:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2581116222-1">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p" data-group-id="2581116222-1">}</span></code></pre><p>The following message is sent to fred's client:</p><pre><code class="makeup erlang" translate="no"><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6293318543-1">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="6293318543-1">}</span><span class="p">,</span></code></pre><p>The following message is sent to peter's client:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8913893065-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="8913893065-1">}</span></code></pre><p>Fred's client receives the message and prints it:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3543016308-1">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="3543016308-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3543016308-2">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3543016308-3">[</span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="3543016308-3">]</span><span class="p" data-group-id="3543016308-2">)</span></code></pre><p>Peter's client receives the message in the <code class="inline">await_result</code> function.</p>
│ │ │ │ +sent:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3678020170-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="3678020170-1">}</span><span class="p">;</span></code></pre><p>This is received by the client.</p><p>If <code class="inline">keyfind</code> returns:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8373161836-1">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p" data-group-id="8373161836-1">}</span></code></pre><p>The following message is sent to fred's client:</p><pre><code class="makeup erlang" translate="no"><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0045752043-1">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="0045752043-1">}</span><span class="p">,</span></code></pre><p>The following message is sent to peter's client:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9695394188-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="9695394188-1">}</span></code></pre><p>Fred's client receives the message and prints it:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4040184690-1">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="4040184690-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4040184690-2">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4040184690-3">[</span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="4040184690-3">]</span><span class="p" data-group-id="4040184690-2">)</span></code></pre><p>Peter's client receives the message in the <code class="inline">await_result</code> function.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/commoncaveats.xhtml
│ │ │ │ @@ -23,31 +23,31 @@
│ │ │ │  <p>This section lists a few constructs to watch out for.</p><h2 id="operator" class="section-heading">
│ │ │ │    <a href="#operator" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Operator <code class="inline">++</code></span>
│ │ │ │  </h2>
│ │ │ │  <p>The <code class="inline">++</code> operator copies its left-hand side operand. That is clearly
│ │ │ │ -seen if we do our own implementation in Erlang:</p><pre><code class="makeup erlang" translate="no"><span class="nf">my_plus_plus</span><span class="p" data-group-id="1622041585-1">(</span><span class="p" data-group-id="1622041585-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1622041585-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="1622041585-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1622041585-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_plus_plus</span><span class="p" data-group-id="1622041585-4">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="1622041585-4">)</span><span class="p" data-group-id="1622041585-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">my_plus_plus</span><span class="p" data-group-id="1622041585-5">(</span><span class="p" data-group-id="1622041585-6">[</span><span class="p" data-group-id="1622041585-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="1622041585-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Tail</span><span class="p">.</span></code></pre><p>We must be careful how we use <code class="inline">++</code> in a loop. First is how not to use it:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">naive_reverse</span><span class="p" data-group-id="5601518093-1">(</span><span class="p" data-group-id="5601518093-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5601518093-2">]</span><span class="p" data-group-id="5601518093-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">naive_reverse</span><span class="p" data-group-id="5601518093-3">(</span><span class="n">T</span><span class="p" data-group-id="5601518093-3">)</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="5601518093-4">[</span><span class="n">H</span><span class="p" data-group-id="5601518093-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">naive_reverse</span><span class="p" data-group-id="5601518093-5">(</span><span class="p" data-group-id="5601518093-6">[</span><span class="p" data-group-id="5601518093-6">]</span><span class="p" data-group-id="5601518093-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5601518093-7">[</span><span class="p" data-group-id="5601518093-7">]</span><span class="p">.</span></code></pre><p>As the <code class="inline">++</code> operator copies its left-hand side operand, the growing
│ │ │ │ -result is copied repeatedly, leading to quadratic complexity.</p><p>On the other hand, using <code class="inline">++</code> in a loop like this is perfectly fine:</p><p><strong>OK</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="3406484496-1">(</span><span class="n">List</span><span class="p" data-group-id="3406484496-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="3406484496-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3406484496-3">[</span><span class="p" data-group-id="3406484496-3">]</span><span class="p" data-group-id="3406484496-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +seen if we do our own implementation in Erlang:</p><pre><code class="makeup erlang" translate="no"><span class="nf">my_plus_plus</span><span class="p" data-group-id="9965536143-1">(</span><span class="p" data-group-id="9965536143-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9965536143-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="9965536143-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9965536143-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_plus_plus</span><span class="p" data-group-id="9965536143-4">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="9965536143-4">)</span><span class="p" data-group-id="9965536143-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">my_plus_plus</span><span class="p" data-group-id="9965536143-5">(</span><span class="p" data-group-id="9965536143-6">[</span><span class="p" data-group-id="9965536143-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="9965536143-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Tail</span><span class="p">.</span></code></pre><p>We must be careful how we use <code class="inline">++</code> in a loop. First is how not to use it:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">naive_reverse</span><span class="p" data-group-id="1687685616-1">(</span><span class="p" data-group-id="1687685616-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1687685616-2">]</span><span class="p" data-group-id="1687685616-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">naive_reverse</span><span class="p" data-group-id="1687685616-3">(</span><span class="n">T</span><span class="p" data-group-id="1687685616-3">)</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="1687685616-4">[</span><span class="n">H</span><span class="p" data-group-id="1687685616-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">naive_reverse</span><span class="p" data-group-id="1687685616-5">(</span><span class="p" data-group-id="1687685616-6">[</span><span class="p" data-group-id="1687685616-6">]</span><span class="p" data-group-id="1687685616-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1687685616-7">[</span><span class="p" data-group-id="1687685616-7">]</span><span class="p">.</span></code></pre><p>As the <code class="inline">++</code> operator copies its left-hand side operand, the growing
│ │ │ │ +result is copied repeatedly, leading to quadratic complexity.</p><p>On the other hand, using <code class="inline">++</code> in a loop like this is perfectly fine:</p><p><strong>OK</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="5166647872-1">(</span><span class="n">List</span><span class="p" data-group-id="5166647872-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="5166647872-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5166647872-3">[</span><span class="p" data-group-id="5166647872-3">]</span><span class="p" data-group-id="5166647872-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="3406484496-4">(</span><span class="p" data-group-id="3406484496-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3406484496-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3406484496-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="3406484496-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3406484496-7">[</span><span class="n">H</span><span class="p" data-group-id="3406484496-7">]</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3406484496-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="3406484496-8">(</span><span class="p" data-group-id="3406484496-9">[</span><span class="p" data-group-id="3406484496-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3406484496-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="5166647872-4">(</span><span class="p" data-group-id="5166647872-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5166647872-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5166647872-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="5166647872-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5166647872-7">[</span><span class="n">H</span><span class="p" data-group-id="5166647872-7">]</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5166647872-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="5166647872-8">(</span><span class="p" data-group-id="5166647872-9">[</span><span class="p" data-group-id="5166647872-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5166647872-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>Each list element is copied only once. The growing result <code class="inline">Acc</code> is the right-hand
│ │ │ │ -side operand, which is <em>not</em> copied.</p><p>Experienced Erlang programmers would probably write as follows:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">vanilla_reverse</span><span class="p" data-group-id="2147516219-1">(</span><span class="p" data-group-id="2147516219-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2147516219-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2147516219-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">vanilla_reverse</span><span class="p" data-group-id="2147516219-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2147516219-4">[</span><span class="n">H</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="2147516219-4">]</span><span class="p" data-group-id="2147516219-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">vanilla_reverse</span><span class="p" data-group-id="2147516219-5">(</span><span class="p" data-group-id="2147516219-6">[</span><span class="p" data-group-id="2147516219-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2147516219-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +side operand, which is <em>not</em> copied.</p><p>Experienced Erlang programmers would probably write as follows:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">vanilla_reverse</span><span class="p" data-group-id="4571259331-1">(</span><span class="p" data-group-id="4571259331-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4571259331-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="4571259331-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">vanilla_reverse</span><span class="p" data-group-id="4571259331-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4571259331-4">[</span><span class="n">H</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="4571259331-4">]</span><span class="p" data-group-id="4571259331-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">vanilla_reverse</span><span class="p" data-group-id="4571259331-5">(</span><span class="p" data-group-id="4571259331-6">[</span><span class="p" data-group-id="4571259331-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="4571259331-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>In principle, this is slightly more efficient because the list element <code class="inline">[H]</code>
│ │ │ │  is not built before being copied and discarded. In practice, the compiler
│ │ │ │  rewrites <code class="inline">[H] ++ Acc</code> to <code class="inline">[H|Acc]</code>.</p><h2 id="timer-module" class="section-heading">
│ │ │ │    <a href="#timer-module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Timer Module</span>
│ │ │ │ @@ -65,49 +65,49 @@
│ │ │ │  therefore harmless.</p><h2 id="accidental-copying-and-loss-of-sharing" class="section-heading">
│ │ │ │    <a href="#accidental-copying-and-loss-of-sharing" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Accidental Copying and Loss of Sharing</span>
│ │ │ │  </h2>
│ │ │ │  <p>When spawning a new process using a fun, one can accidentally copy more data to
│ │ │ │ -the process than intended. For example:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">accidental1</span><span class="p" data-group-id="1523536107-1">(</span><span class="n">State</span><span class="p" data-group-id="1523536107-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="1523536107-2">(</span><span class="nf">fun</span><span class="p" data-group-id="1523536107-3">(</span><span class="p" data-group-id="1523536107-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1523536107-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1523536107-5">[</span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">info</span><span class="p" data-group-id="1523536107-5">]</span><span class="p" data-group-id="1523536107-4">)</span><span class="w">
│ │ │ │ -          </span><span class="k">end</span><span class="p" data-group-id="1523536107-2">)</span><span class="p">.</span></code></pre><p>The code in the fun will extract one element from the record and print it. The
│ │ │ │ +the process than intended. For example:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">accidental1</span><span class="p" data-group-id="3851575394-1">(</span><span class="n">State</span><span class="p" data-group-id="3851575394-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="3851575394-2">(</span><span class="nf">fun</span><span class="p" data-group-id="3851575394-3">(</span><span class="p" data-group-id="3851575394-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3851575394-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3851575394-5">[</span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">info</span><span class="p" data-group-id="3851575394-5">]</span><span class="p" data-group-id="3851575394-4">)</span><span class="w">
│ │ │ │ +          </span><span class="k">end</span><span class="p" data-group-id="3851575394-2">)</span><span class="p">.</span></code></pre><p>The code in the fun will extract one element from the record and print it. The
│ │ │ │  rest of the <code class="inline">state</code> record is not used. However, when the <a href="../../../lib/../erts/doc/html/erlang.html#spawn/1"><code class="inline">spawn/1</code></a>
│ │ │ │ -function is executed, the entire record is copied to the newly created process.</p><p>The same kind of problem can happen with a map:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">accidental2</span><span class="p" data-group-id="3175466093-1">(</span><span class="n">State</span><span class="p" data-group-id="3175466093-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="3175466093-2">(</span><span class="nf">fun</span><span class="p" data-group-id="3175466093-3">(</span><span class="p" data-group-id="3175466093-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3175466093-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3175466093-5">[</span><span class="nf">map_get</span><span class="p" data-group-id="3175466093-6">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="3175466093-6">)</span><span class="p" data-group-id="3175466093-5">]</span><span class="p" data-group-id="3175466093-4">)</span><span class="w">
│ │ │ │ -          </span><span class="k">end</span><span class="p" data-group-id="3175466093-2">)</span><span class="p">.</span></code></pre><p>In the following example (part of a module implementing the <a href="../../../lib/stdlib/doc/html/gen_server.html"><code class="inline">gen_server</code></a>
│ │ │ │ -behavior) the created fun is sent to another process:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_call</span><span class="p" data-group-id="7722962731-1">(</span><span class="ss">give_me_a_fun</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="7722962731-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="7722962731-2">(</span><span class="p" data-group-id="7722962731-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="nb">size</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7722962731-3">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="7722962731-3">}</span><span class="p">.</span></code></pre><p>How bad that unnecessary copy is depends on the contents of the record or the
│ │ │ │ -map.</p><p>For example, if the <code class="inline">state</code> record is initialized like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init1</span><span class="p" data-group-id="8534528902-1">(</span><span class="p" data-group-id="8534528902-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="8534528902-2">{</span><span class="ss">data</span><span class="o">=</span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="8534528902-3">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">10000</span><span class="p" data-group-id="8534528902-3">)</span><span class="p" data-group-id="8534528902-2">}</span><span class="p">.</span></code></pre><p>a list with 10000 elements (or about 20000 heap words) will be copied to the
│ │ │ │ +function is executed, the entire record is copied to the newly created process.</p><p>The same kind of problem can happen with a map:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">accidental2</span><span class="p" data-group-id="4975354763-1">(</span><span class="n">State</span><span class="p" data-group-id="4975354763-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="4975354763-2">(</span><span class="nf">fun</span><span class="p" data-group-id="4975354763-3">(</span><span class="p" data-group-id="4975354763-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4975354763-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4975354763-5">[</span><span class="nf">map_get</span><span class="p" data-group-id="4975354763-6">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4975354763-6">)</span><span class="p" data-group-id="4975354763-5">]</span><span class="p" data-group-id="4975354763-4">)</span><span class="w">
│ │ │ │ +          </span><span class="k">end</span><span class="p" data-group-id="4975354763-2">)</span><span class="p">.</span></code></pre><p>In the following example (part of a module implementing the <a href="../../../lib/stdlib/doc/html/gen_server.html"><code class="inline">gen_server</code></a>
│ │ │ │ +behavior) the created fun is sent to another process:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_call</span><span class="p" data-group-id="2738260883-1">(</span><span class="ss">give_me_a_fun</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2738260883-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="2738260883-2">(</span><span class="p" data-group-id="2738260883-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="nb">size</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2738260883-3">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2738260883-3">}</span><span class="p">.</span></code></pre><p>How bad that unnecessary copy is depends on the contents of the record or the
│ │ │ │ +map.</p><p>For example, if the <code class="inline">state</code> record is initialized like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init1</span><span class="p" data-group-id="6943297355-1">(</span><span class="p" data-group-id="6943297355-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="6943297355-2">{</span><span class="ss">data</span><span class="o">=</span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="6943297355-3">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">10000</span><span class="p" data-group-id="6943297355-3">)</span><span class="p" data-group-id="6943297355-2">}</span><span class="p">.</span></code></pre><p>a list with 10000 elements (or about 20000 heap words) will be copied to the
│ │ │ │  newly created process.</p><p>An unnecessary copy of 10000 element list can be bad enough, but it can get even
│ │ │ │  worse if the <code class="inline">state</code> record contains <em>shared subterms</em>. Here is a simple example
│ │ │ │ -of a term with a shared subterm:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1602059273-1">{</span><span class="n">SubTerm</span><span class="p">,</span><span class="w"> </span><span class="n">SubTerm</span><span class="p" data-group-id="1602059273-1">}</span></code></pre><p>When a term is copied to another process, sharing of subterms will be lost and
│ │ │ │ -the copied term can be many times larger than the original term. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init2</span><span class="p" data-group-id="8539791965-1">(</span><span class="p" data-group-id="8539791965-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SharedSubTerms</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="8539791965-2">(</span><span class="nf">fun</span><span class="p" data-group-id="8539791965-3">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="8539791965-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8539791965-4">[</span><span class="n">A</span><span class="p">|</span><span class="n">A</span><span class="p" data-group-id="8539791965-4">]</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8539791965-5">[</span><span class="mi">0</span><span class="p" data-group-id="8539791965-5">]</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="8539791965-6">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">15</span><span class="p" data-group-id="8539791965-6">)</span><span class="p" data-group-id="8539791965-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="8539791965-7">{</span><span class="ss">data</span><span class="o">=</span><span class="n">SharedSubTerms</span><span class="p" data-group-id="8539791965-7">}</span><span class="p">.</span></code></pre><p>In the process that calls <code class="inline">init2/0</code>, the size of the <code class="inline">data</code> field in the <code class="inline">state</code>
│ │ │ │ +of a term with a shared subterm:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9549806371-1">{</span><span class="n">SubTerm</span><span class="p">,</span><span class="w"> </span><span class="n">SubTerm</span><span class="p" data-group-id="9549806371-1">}</span></code></pre><p>When a term is copied to another process, sharing of subterms will be lost and
│ │ │ │ +the copied term can be many times larger than the original term. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init2</span><span class="p" data-group-id="7865446793-1">(</span><span class="p" data-group-id="7865446793-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SharedSubTerms</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="7865446793-2">(</span><span class="nf">fun</span><span class="p" data-group-id="7865446793-3">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="7865446793-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7865446793-4">[</span><span class="n">A</span><span class="p">|</span><span class="n">A</span><span class="p" data-group-id="7865446793-4">]</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7865446793-5">[</span><span class="mi">0</span><span class="p" data-group-id="7865446793-5">]</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="7865446793-6">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">15</span><span class="p" data-group-id="7865446793-6">)</span><span class="p" data-group-id="7865446793-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="7865446793-7">{</span><span class="ss">data</span><span class="o">=</span><span class="n">SharedSubTerms</span><span class="p" data-group-id="7865446793-7">}</span><span class="p">.</span></code></pre><p>In the process that calls <code class="inline">init2/0</code>, the size of the <code class="inline">data</code> field in the <code class="inline">state</code>
│ │ │ │  record will be 32 heap words. When the record is copied to the newly created
│ │ │ │  process, sharing will be lost and the size of the copied <code class="inline">data</code> field will be
│ │ │ │  131070 heap words. More details about
│ │ │ │  <a href="eff_guide_processes.xhtml#loss-of-sharing">loss of sharing</a> are found in a later
│ │ │ │  section.</p><p>To avoid the problem, outside of the fun extract only the fields of the record
│ │ │ │ -that are actually used:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">fixed_accidental1</span><span class="p" data-group-id="2487903372-1">(</span><span class="n">State</span><span class="p" data-group-id="2487903372-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +that are actually used:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">fixed_accidental1</span><span class="p" data-group-id="0631811664-1">(</span><span class="n">State</span><span class="p" data-group-id="0631811664-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">info</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="2487903372-2">(</span><span class="nf">fun</span><span class="p" data-group-id="2487903372-3">(</span><span class="p" data-group-id="2487903372-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2487903372-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2487903372-5">[</span><span class="n">Info</span><span class="p" data-group-id="2487903372-5">]</span><span class="p" data-group-id="2487903372-4">)</span><span class="w">
│ │ │ │ -          </span><span class="k">end</span><span class="p" data-group-id="2487903372-2">)</span><span class="p">.</span></code></pre><p>Similarly, outside of the fun extract only the map elements that are actually
│ │ │ │ -used:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">fixed_accidental2</span><span class="p" data-group-id="7970768091-1">(</span><span class="n">State</span><span class="p" data-group-id="7970768091-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">map_get</span><span class="p" data-group-id="7970768091-2">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="7970768091-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="7970768091-3">(</span><span class="nf">fun</span><span class="p" data-group-id="7970768091-4">(</span><span class="p" data-group-id="7970768091-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7970768091-5">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7970768091-6">[</span><span class="n">Info</span><span class="p" data-group-id="7970768091-6">]</span><span class="p" data-group-id="7970768091-5">)</span><span class="w">
│ │ │ │ -          </span><span class="k">end</span><span class="p" data-group-id="7970768091-3">)</span><span class="p">.</span></code></pre><h2 id="list_to_atom-1-binary_to_atom-1-2" class="section-heading">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="0631811664-2">(</span><span class="nf">fun</span><span class="p" data-group-id="0631811664-3">(</span><span class="p" data-group-id="0631811664-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0631811664-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0631811664-5">[</span><span class="n">Info</span><span class="p" data-group-id="0631811664-5">]</span><span class="p" data-group-id="0631811664-4">)</span><span class="w">
│ │ │ │ +          </span><span class="k">end</span><span class="p" data-group-id="0631811664-2">)</span><span class="p">.</span></code></pre><p>Similarly, outside of the fun extract only the map elements that are actually
│ │ │ │ +used:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">fixed_accidental2</span><span class="p" data-group-id="5230617153-1">(</span><span class="n">State</span><span class="p" data-group-id="5230617153-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">map_get</span><span class="p" data-group-id="5230617153-2">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5230617153-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="5230617153-3">(</span><span class="nf">fun</span><span class="p" data-group-id="5230617153-4">(</span><span class="p" data-group-id="5230617153-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5230617153-5">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5230617153-6">[</span><span class="n">Info</span><span class="p" data-group-id="5230617153-6">]</span><span class="p" data-group-id="5230617153-5">)</span><span class="w">
│ │ │ │ +          </span><span class="k">end</span><span class="p" data-group-id="5230617153-3">)</span><span class="p">.</span></code></pre><h2 id="list_to_atom-1-binary_to_atom-1-2" class="section-heading">
│ │ │ │    <a href="#list_to_atom-1-binary_to_atom-1-2" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">list_to_atom/1, binary_to_atom/1,2</span>
│ │ │ │  </h2>
│ │ │ │  <p>Atoms are not garbage-collected. Once an atom is created, it is never removed.
│ │ │ │  The emulator terminates if the limit for the number of atoms (1,048,576 by
│ │ │ │ @@ -116,28 +116,28 @@
│ │ │ │  input, <a href="../../../lib/../erts/doc/html/erlang.html#list_to_existing_atom/1"><code class="inline">list_to_existing_atom/1</code></a>,
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#binary_to_existing_atom/1"><code class="inline">binary_to_existing_atom/1</code></a>, or
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#binary_to_existing_atom/2"><code class="inline">binary_to_existing_atom/2</code></a> can be used
│ │ │ │  to guard against a denial-of-service attack. All atoms that are allowed must
│ │ │ │  have been created earlier, for example, by using all of them in a module
│ │ │ │  and loading that module.</p><p>Using <a href="../../../lib/../erts/doc/html/erlang.html#list_to_atom/1"><code class="inline">list_to_atom/1</code></a>, <a href="../../../lib/../erts/doc/html/erlang.html#binary_to_atom/1"><code class="inline">binary_to_atom/1</code></a>, or
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#binary_to_atom/2"><code class="inline">binary_to_atom/2</code></a> to construct an atom that
│ │ │ │ -is passed to <a href="../../../lib/../erts/doc/html/erlang.html#apply/3"><code class="inline">apply/3</code></a> is quite expensive.</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">apply</span><span class="p" data-group-id="8318969565-1">(</span><span class="nf">list_to_atom</span><span class="p" data-group-id="8318969565-2">(</span><span class="s">&quot;some_prefix&quot;</span><span class="o">++</span><span class="n">Var</span><span class="p" data-group-id="8318969565-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="8318969565-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">apply</span><span class="p" data-group-id="4796302129-1">(</span><span class="nf">binary_to_atom</span><span class="p" data-group-id="4796302129-2">(</span><span class="p" data-group-id="4796302129-3">&lt;&lt;</span><span class="s">&quot;some_prefix&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Var</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4796302129-3">&gt;&gt;</span><span class="p" data-group-id="4796302129-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="4796302129-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">apply</span><span class="p" data-group-id="9090239418-1">(</span><span class="nf">binary_to_atom</span><span class="p" data-group-id="9090239418-2">(</span><span class="p" data-group-id="9090239418-3">&lt;&lt;</span><span class="s">&quot;some_prefix&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Var</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="9090239418-3">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="ss">utf8</span><span class="p" data-group-id="9090239418-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="9090239418-1">)</span></code></pre><h2 id="length-1" class="section-heading">
│ │ │ │ +is passed to <a href="../../../lib/../erts/doc/html/erlang.html#apply/3"><code class="inline">apply/3</code></a> is quite expensive.</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">apply</span><span class="p" data-group-id="0432756891-1">(</span><span class="nf">list_to_atom</span><span class="p" data-group-id="0432756891-2">(</span><span class="s">&quot;some_prefix&quot;</span><span class="o">++</span><span class="n">Var</span><span class="p" data-group-id="0432756891-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="0432756891-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">apply</span><span class="p" data-group-id="6284586096-1">(</span><span class="nf">binary_to_atom</span><span class="p" data-group-id="6284586096-2">(</span><span class="p" data-group-id="6284586096-3">&lt;&lt;</span><span class="s">&quot;some_prefix&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Var</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6284586096-3">&gt;&gt;</span><span class="p" data-group-id="6284586096-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="6284586096-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">apply</span><span class="p" data-group-id="8546776015-1">(</span><span class="nf">binary_to_atom</span><span class="p" data-group-id="8546776015-2">(</span><span class="p" data-group-id="8546776015-3">&lt;&lt;</span><span class="s">&quot;some_prefix&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Var</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8546776015-3">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="ss">utf8</span><span class="p" data-group-id="8546776015-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="8546776015-1">)</span></code></pre><h2 id="length-1" class="section-heading">
│ │ │ │    <a href="#length-1" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">length/1</span>
│ │ │ │  </h2>
│ │ │ │  <p>The time for calculating the length of a list is proportional to the length of
│ │ │ │  the list, as opposed to <a href="../../../lib/../erts/doc/html/erlang.html#tuple_size/1"><code class="inline">tuple_size/1</code></a>,
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#byte_size/1"><code class="inline">byte_size/1</code></a>, and <a href="../../../lib/../erts/doc/html/erlang.html#bit_size/1"><code class="inline">bit_size/1</code></a>, which all
│ │ │ │  execute in constant time.</p><p>Normally, there is no need to worry about the speed of <a href="../../../lib/../erts/doc/html/erlang.html#length/1"><code class="inline">length/1</code></a>,
│ │ │ │  because it is efficiently implemented in C. In time-critical code, you might
│ │ │ │  want to avoid it if the input list could potentially be very long.</p><p>Some uses of <a href="../../../lib/../erts/doc/html/erlang.html#length/1"><code class="inline">length/1</code></a> can be replaced by matching. For example,
│ │ │ │ -the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="9483547745-1">(</span><span class="n">L</span><span class="p" data-group-id="9483547745-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="9483547745-2">(</span><span class="n">L</span><span class="p" data-group-id="9483547745-2">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>can be rewritten to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="5334633131-1">(</span><span class="p" data-group-id="5334633131-2">[</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="5334633131-2">]</span><span class="o">=</span><span class="n">L</span><span class="p" data-group-id="5334633131-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="4585583691-1">(</span><span class="n">L</span><span class="p" data-group-id="4585583691-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="4585583691-2">(</span><span class="n">L</span><span class="p" data-group-id="4585583691-2">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>can be rewritten to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="9359737719-1">(</span><span class="p" data-group-id="9359737719-2">[</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="9359737719-2">]</span><span class="o">=</span><span class="n">L</span><span class="p" data-group-id="9359737719-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │     </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>One slight difference is that <a href="../../../lib/../erts/doc/html/erlang.html#length/1"><code class="inline">length(L)</code></a> fails if <code class="inline">L</code> is an
│ │ │ │  improper list, while the pattern in the second code fragment accepts an improper
│ │ │ │  list.</p><h2 id="setelement-3" class="section-heading">
│ │ │ │    <a href="#setelement-3" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">setelement/3</span>
│ │ │ │ @@ -148,18 +148,18 @@
│ │ │ │    <a href="#compiler-optimizations-of-setelement-3" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Compiler optimizations of setelement/3</span>
│ │ │ │  </h3>
│ │ │ │  <p>Under certain conditions, the compiler can coalesce multiple calls to
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> into a single operation, avoiding
│ │ │ │ -the cost of copying the tuple for each call.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">multiple_setelement</span><span class="p" data-group-id="0590081522-1">(</span><span class="n">T0</span><span class="p" data-group-id="0590081522-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">tuple_size</span><span class="p" data-group-id="0590081522-2">(</span><span class="n">T0</span><span class="p" data-group-id="0590081522-2">)</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">9</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">T1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="0590081522-3">(</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="n">T0</span><span class="p">,</span><span class="w"> </span><span class="ss">new_value</span><span class="p" data-group-id="0590081522-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">T2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="0590081522-4">(</span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p">,</span><span class="w"> </span><span class="ss">foobar</span><span class="p" data-group-id="0590081522-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">setelement</span><span class="p" data-group-id="0590081522-5">(</span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p" data-group-id="0590081522-5">)</span><span class="p">.</span></code></pre><p>The compiler will replace the three <a href="../../../lib/../erts/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> calls with code that
│ │ │ │ +the cost of copying the tuple for each call.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">multiple_setelement</span><span class="p" data-group-id="8287044628-1">(</span><span class="n">T0</span><span class="p" data-group-id="8287044628-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">tuple_size</span><span class="p" data-group-id="8287044628-2">(</span><span class="n">T0</span><span class="p" data-group-id="8287044628-2">)</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">9</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">T1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="8287044628-3">(</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="n">T0</span><span class="p">,</span><span class="w"> </span><span class="ss">new_value</span><span class="p" data-group-id="8287044628-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">T2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="8287044628-4">(</span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p">,</span><span class="w"> </span><span class="ss">foobar</span><span class="p" data-group-id="8287044628-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">setelement</span><span class="p" data-group-id="8287044628-5">(</span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p" data-group-id="8287044628-5">)</span><span class="p">.</span></code></pre><p>The compiler will replace the three <a href="../../../lib/../erts/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> calls with code that
│ │ │ │  copies the tuple once and updates the elements at positions 5, 7, and 9.</p><p>Starting with Erlang/OTP 26, the following conditions must be met for
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> calls to be coalesced into a single
│ │ │ │  operation:</p><ul><li><p>The tuple argument must be known at compile time to be a tuple of a
│ │ │ │  specific size.</p></li><li><p>The element indices must be integer literals, not variables or expressions.</p></li><li><p>There must be no intervening expressions between the calls to
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a>.</p></li><li><p>The tuple returned from one <a href="../../../lib/../erts/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> call must be
│ │ │ │  used only in the subsequent <a href="../../../lib/../erts/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> call.</p></li></ul><p>Before Erlang/OTP 26, an additional condition was that
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> calls had to be made in descending
│ │ │ ├── OEBPS/code_loading.xhtml
│ │ │ │ @@ -27,16 +27,16 @@
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Compilation</span>
│ │ │ │  </h2>
│ │ │ │  <p>Erlang programs must be <em>compiled</em> to object code. The compiler can generate a
│ │ │ │  new file that contains the object code. The current abstract machine, which runs
│ │ │ │  the object code, is called BEAM and therefore the object files get the suffix
│ │ │ │ -<code class="inline">.beam</code>. The compiler can also generate a binary which can be loaded directly.</p><p>The compiler is located in the module <a href="../../../lib/compiler/doc/html/compile.html"><code class="inline">compile</code></a> in Compiler.</p><pre><code class="makeup erlang" translate="no"><span class="nc">compile</span><span class="p">:</span><span class="nf">file</span><span class="p" data-group-id="6814828167-1">(</span><span class="n">Module</span><span class="p" data-group-id="6814828167-1">)</span><span class="w">
│ │ │ │ -</span><span class="nc">compile</span><span class="p">:</span><span class="nf">file</span><span class="p" data-group-id="6814828167-2">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="6814828167-2">)</span></code></pre><p>The Erlang shell understands the command <code class="inline">c(Module)</code>, which both compiles and
│ │ │ │ +<code class="inline">.beam</code>. The compiler can also generate a binary which can be loaded directly.</p><p>The compiler is located in the module <a href="../../../lib/compiler/doc/html/compile.html"><code class="inline">compile</code></a> in Compiler.</p><pre><code class="makeup erlang" translate="no"><span class="nc">compile</span><span class="p">:</span><span class="nf">file</span><span class="p" data-group-id="5601267157-1">(</span><span class="n">Module</span><span class="p" data-group-id="5601267157-1">)</span><span class="w">
│ │ │ │ +</span><span class="nc">compile</span><span class="p">:</span><span class="nf">file</span><span class="p" data-group-id="5601267157-2">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="5601267157-2">)</span></code></pre><p>The Erlang shell understands the command <code class="inline">c(Module)</code>, which both compiles and
│ │ │ │  loads <code class="inline">Module</code>.</p><p>There is also a module <code class="inline">make</code>, which provides a set of functions similar to the
│ │ │ │  UNIX type Make functions, see module <a href="../../../lib/tools/doc/html/make.html"><code class="inline">make</code></a> in Tools.</p><p>The compiler can also be accessed from the OS prompt using the
│ │ │ │  <a href="../../../lib/../erts/doc/html/erl_cmd.xhtml">erl</a> executable in ERTS.</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -compile Module1...ModuleN</span><span class="w">
│ │ │ │  </span><span class="c1">% erl -make</span></code></pre><p>The <code class="inline">erlc</code> program provides a way to compile modules from the OS
│ │ │ │  shell, see the <a href="../../../lib/../erts/doc/html/erlc_cmd.xhtml">erlc</a> executable in ERTS. It
│ │ │ │  understands a number of flags that can be used to define macros, add search
│ │ │ │  paths for include files, and more.</p><pre><code class="text">% erlc &lt;flags&gt; File1.erl...FileN.erl</code></pre><p><a href="" id="loading"></a></p><h2 id="code-loading" class="section-heading">
│ │ │ │ @@ -61,51 +61,51 @@
│ │ │ │  When a module is loaded into the system for the first time, the code becomes
│ │ │ │  'current'. If then a new instance of the module is loaded, the code of the
│ │ │ │  previous instance becomes 'old' and the new instance becomes 'current'.</p><p>Both old and current code are valid, and can be evaluated concurrently. Fully
│ │ │ │  qualified function calls always refer to current code. Old code can still be
│ │ │ │  evaluated because of processes lingering in the old code.</p><p>If a third instance of the module is loaded, the code server removes (purges)
│ │ │ │  the old code and any processes lingering in it are terminated. Then the third
│ │ │ │  instance becomes 'current' and the previously current code becomes 'old'.</p><p>To change from old code to current code, a process must make a fully qualified
│ │ │ │ -function call.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2509757695-1">(</span><span class="ss">m</span><span class="p" data-group-id="2509757695-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2509757695-2">(</span><span class="p" data-group-id="2509757695-3">[</span><span class="ss">loop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2509757695-3">]</span><span class="p" data-group-id="2509757695-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +function call.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5557413022-1">(</span><span class="ss">m</span><span class="p" data-group-id="5557413022-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5557413022-2">(</span><span class="p" data-group-id="5557413022-3">[</span><span class="ss">loop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5557413022-3">]</span><span class="p" data-group-id="5557413022-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="2509757695-4">(</span><span class="p" data-group-id="2509757695-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="5557413022-4">(</span><span class="p" data-group-id="5557413022-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">code_switch</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">m</span><span class="p">:</span><span class="nf">loop</span><span class="p" data-group-id="2509757695-5">(</span><span class="p" data-group-id="2509757695-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="nc">m</span><span class="p">:</span><span class="nf">loop</span><span class="p" data-group-id="5557413022-5">(</span><span class="p" data-group-id="5557413022-5">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="n">Msg</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="2509757695-6">(</span><span class="p" data-group-id="2509757695-6">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="5557413022-6">(</span><span class="p" data-group-id="5557413022-6">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>To make the process change code, send the message <code class="inline">code_switch</code> to it. The
│ │ │ │  process then makes a fully qualified call to <code class="inline">m:loop()</code> and changes to current
│ │ │ │  code. Notice that <code class="inline">m:loop/0</code> must be exported.</p><p>For code replacement of funs to work, use the syntax
│ │ │ │  <code class="inline">fun Module:FunctionName/Arity</code>.</p><p><a href="" id="on_load"></a></p><h2 id="running-a-function-when-a-module-is-loaded" class="section-heading">
│ │ │ │    <a href="#running-a-function-when-a-module-is-loaded" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Running a Function When a Module is Loaded</span>
│ │ │ │  </h2>
│ │ │ │  <p>The <code class="inline">-on_load()</code> directive names a function that is to be run automatically when
│ │ │ │ -a module is loaded.</p><p>Its syntax is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="5394656354-1">(</span><span class="n">Name</span><span class="o">/</span><span class="mi">0</span><span class="p" data-group-id="5394656354-1">)</span><span class="p">.</span></code></pre><p>It is not necessary to export the function. It is called in a freshly spawned
│ │ │ │ +a module is loaded.</p><p>Its syntax is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="0616869960-1">(</span><span class="n">Name</span><span class="o">/</span><span class="mi">0</span><span class="p" data-group-id="0616869960-1">)</span><span class="p">.</span></code></pre><p>It is not necessary to export the function. It is called in a freshly spawned
│ │ │ │  process (which terminates as soon as the function returns).</p><p>The function must return <code class="inline">ok</code> if the module is to become the new current code
│ │ │ │  for the module and become callable.</p><p>Returning any other value or generating an exception causes the new code to be
│ │ │ │  unloaded. If the return value is not an atom, a warning error report is sent to
│ │ │ │  the error logger.</p><p>If there already is current code for the module, that code will remain current
│ │ │ │  and can be called until the <code class="inline">on_load</code> function has returned. If the <code class="inline">on_load</code>
│ │ │ │  function fails, the current code (if any) will remain current. If there is no
│ │ │ │  current code for a module, any process that makes an external call to the module
│ │ │ │  before the <code class="inline">on_load</code> function has finished will be suspended until the <code class="inline">on_load</code>
│ │ │ │  function has finished.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 19, if the <code class="inline">on_load</code> function failed, any previously current
│ │ │ │  code would become old, essentially leaving the system without any working and
│ │ │ │  reachable instance of the module.</p></section><p>In embedded mode, first all modules are loaded. Then all <code class="inline">on_load</code> functions are
│ │ │ │  called. The system is terminated unless all of the <code class="inline">on_load</code> functions return
│ │ │ │ -<code class="inline">ok</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3851382516-1">(</span><span class="ss">m</span><span class="p" data-group-id="3851382516-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="3851382516-2">(</span><span class="ss">load_my_nifs</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3851382516-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">ok</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2162827768-1">(</span><span class="ss">m</span><span class="p" data-group-id="2162827768-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="2162827768-2">(</span><span class="ss">load_my_nifs</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2162827768-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">load_my_nifs</span><span class="p" data-group-id="3851382516-3">(</span><span class="p" data-group-id="3851382516-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">load_my_nifs</span><span class="p" data-group-id="2162827768-3">(</span><span class="p" data-group-id="2162827768-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">NifPath</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">    </span><span class="c1">%Set up the path to the NIF library.</span><span class="w">
│ │ │ │      </span><span class="n">Info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">       </span><span class="c1">%Initialize the Info term</span><span class="w">
│ │ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="3851382516-4">(</span><span class="n">NifPath</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p" data-group-id="3851382516-4">)</span><span class="p">.</span></code></pre><p>If the call to <a href="../../../lib/../erts/doc/html/erlang.html#load_nif/2"><code class="inline">erlang:load_nif/2</code></a> fails, the module is unloaded and a warning
│ │ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="2162827768-4">(</span><span class="n">NifPath</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p" data-group-id="2162827768-4">)</span><span class="p">.</span></code></pre><p>If the call to <a href="../../../lib/../erts/doc/html/erlang.html#load_nif/2"><code class="inline">erlang:load_nif/2</code></a> fails, the module is unloaded and a warning
│ │ │ │  report is sent to the error logger.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/c_portdriver.xhtml
│ │ │ │ @@ -56,112 +56,112 @@
│ │ │ │  <p>Like a port program, the port communicates with an Erlang process. All
│ │ │ │  communication goes through one Erlang process that is the <em>connected process</em> of
│ │ │ │  the port driver. Terminating this process closes the port driver.</p><p>Before the port is created, the driver must be loaded. This is done with the
│ │ │ │  function <a href="../../../lib/kernel/doc/html/erl_ddll.html#load_driver/2"><code class="inline">erl_ddll:load_driver/2</code></a>, with the name of the shared library as
│ │ │ │  argument.</p><p>The port is then created using the BIF <a href="../../../lib/../erts/doc/html/erlang.html#open_port/2"><code class="inline">open_port/2</code></a>, with the
│ │ │ │  tuple <code class="inline">{spawn, DriverName}</code> as the first argument. The string <code class="inline">SharedLib</code> is the
│ │ │ │  name of the port driver. The second argument is a list of options, none in this
│ │ │ │ -case:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2183174677-1">(</span><span class="ss">complex5</span><span class="p" data-group-id="2183174677-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2183174677-2">(</span><span class="p" data-group-id="2183174677-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2183174677-3">]</span><span class="p" data-group-id="2183174677-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +case:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8396170461-1">(</span><span class="ss">complex5</span><span class="p" data-group-id="8396170461-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8396170461-2">(</span><span class="p" data-group-id="8396170461-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8396170461-3">]</span><span class="p" data-group-id="8396170461-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="2183174677-4">(</span><span class="n">SharedLib</span><span class="p" data-group-id="2183174677-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="2183174677-5">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="2183174677-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="8396170461-4">(</span><span class="n">SharedLib</span><span class="p" data-group-id="8396170461-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="8396170461-5">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="8396170461-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="2183174677-6">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="2183174677-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="2183174677-7">(</span><span class="p" data-group-id="2183174677-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="2183174677-8">}</span><span class="p" data-group-id="2183174677-7">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="8396170461-6">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="8396170461-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="8396170461-7">(</span><span class="p" data-group-id="8396170461-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="8396170461-8">}</span><span class="p" data-group-id="8396170461-7">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="2183174677-9">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2183174677-10">[</span><span class="n">SharedLib</span><span class="p" data-group-id="2183174677-10">]</span><span class="p" data-group-id="2183174677-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="8396170461-9">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8396170461-10">[</span><span class="n">SharedLib</span><span class="p" data-group-id="8396170461-10">]</span><span class="p" data-group-id="8396170461-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="2183174677-11">(</span><span class="n">SharedLib</span><span class="p" data-group-id="2183174677-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -  </span><span class="nf">register</span><span class="p" data-group-id="2183174677-12">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2183174677-13">(</span><span class="p" data-group-id="2183174677-13">)</span><span class="p" data-group-id="2183174677-12">)</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="2183174677-14">(</span><span class="p" data-group-id="2183174677-15">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="2183174677-15">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2183174677-16">[</span><span class="p" data-group-id="2183174677-16">]</span><span class="p" data-group-id="2183174677-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="nf">loop</span><span class="p" data-group-id="2183174677-17">(</span><span class="n">Port</span><span class="p" data-group-id="2183174677-17">)</span><span class="p">.</span></code></pre><p>Now <code class="inline">complex5:foo/1</code> and <code class="inline">complex5:bar/1</code> can be implemented. Both send a
│ │ │ │ -message to the <code class="inline">complex</code> process and receive the following reply:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="8120755643-1">(</span><span class="n">X</span><span class="p" data-group-id="8120755643-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="8120755643-2">(</span><span class="p" data-group-id="8120755643-3">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="8120755643-3">}</span><span class="p" data-group-id="8120755643-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="8120755643-4">(</span><span class="n">Y</span><span class="p" data-group-id="8120755643-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="8120755643-5">(</span><span class="p" data-group-id="8120755643-6">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8120755643-6">}</span><span class="p" data-group-id="8120755643-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="8396170461-11">(</span><span class="n">SharedLib</span><span class="p" data-group-id="8396170461-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="nf">register</span><span class="p" data-group-id="8396170461-12">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8396170461-13">(</span><span class="p" data-group-id="8396170461-13">)</span><span class="p" data-group-id="8396170461-12">)</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="8396170461-14">(</span><span class="p" data-group-id="8396170461-15">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="8396170461-15">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8396170461-16">[</span><span class="p" data-group-id="8396170461-16">]</span><span class="p" data-group-id="8396170461-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="nf">loop</span><span class="p" data-group-id="8396170461-17">(</span><span class="n">Port</span><span class="p" data-group-id="8396170461-17">)</span><span class="p">.</span></code></pre><p>Now <code class="inline">complex5:foo/1</code> and <code class="inline">complex5:bar/1</code> can be implemented. Both send a
│ │ │ │ +message to the <code class="inline">complex</code> process and receive the following reply:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="0760511707-1">(</span><span class="n">X</span><span class="p" data-group-id="0760511707-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="0760511707-2">(</span><span class="p" data-group-id="0760511707-3">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0760511707-3">}</span><span class="p" data-group-id="0760511707-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="0760511707-4">(</span><span class="n">Y</span><span class="p" data-group-id="0760511707-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="0760511707-5">(</span><span class="p" data-group-id="0760511707-6">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0760511707-6">}</span><span class="p" data-group-id="0760511707-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="8120755643-7">(</span><span class="n">Msg</span><span class="p" data-group-id="8120755643-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8120755643-8">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8120755643-9">(</span><span class="p" data-group-id="8120755643-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="8120755643-8">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="0760511707-7">(</span><span class="n">Msg</span><span class="p" data-group-id="0760511707-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0760511707-8">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0760511707-9">(</span><span class="p" data-group-id="0760511707-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0760511707-8">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8120755643-10">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="8120755643-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0760511707-10">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0760511707-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="n">Result</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">complex</code> process performs the following:</p><ul><li>Encodes the message into a sequence of bytes.</li><li>Sends it to the port.</li><li>Waits for a reply.</li><li>Decodes the reply.</li><li>Sends it back to the caller:</li></ul><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="0455697067-1">(</span><span class="n">Port</span><span class="p" data-group-id="0455697067-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">complex</code> process performs the following:</p><ul><li>Encodes the message into a sequence of bytes.</li><li>Sends it to the port.</li><li>Waits for a reply.</li><li>Decodes the reply.</li><li>Sends it back to the caller:</li></ul><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="8362188733-1">(</span><span class="n">Port</span><span class="p" data-group-id="8362188733-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="0455697067-2">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0455697067-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0455697067-3">{</span><span class="nf">self</span><span class="p" data-group-id="0455697067-4">(</span><span class="p" data-group-id="0455697067-4">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0455697067-5">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="0455697067-6">(</span><span class="n">Msg</span><span class="p" data-group-id="0455697067-6">)</span><span class="p" data-group-id="0455697067-5">}</span><span class="p" data-group-id="0455697067-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="8362188733-2">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="8362188733-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8362188733-3">{</span><span class="nf">self</span><span class="p" data-group-id="8362188733-4">(</span><span class="p" data-group-id="8362188733-4">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8362188733-5">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="8362188733-6">(</span><span class="n">Msg</span><span class="p" data-group-id="8362188733-6">)</span><span class="p" data-group-id="8362188733-5">}</span><span class="p" data-group-id="8362188733-3">}</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="k">receive</span><span class="w">
│ │ │ │ -                </span><span class="p" data-group-id="0455697067-7">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0455697067-8">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0455697067-8">}</span><span class="p" data-group-id="0455697067-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0455697067-9">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="0455697067-10">(</span><span class="n">Data</span><span class="p" data-group-id="0455697067-10">)</span><span class="p" data-group-id="0455697067-9">}</span><span class="w">
│ │ │ │ +                </span><span class="p" data-group-id="8362188733-7">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8362188733-8">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8362188733-8">}</span><span class="p" data-group-id="8362188733-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8362188733-9">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="8362188733-10">(</span><span class="n">Data</span><span class="p" data-group-id="8362188733-10">)</span><span class="p" data-group-id="8362188733-9">}</span><span class="w">
│ │ │ │              </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="0455697067-11">(</span><span class="n">Port</span><span class="p" data-group-id="0455697067-11">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="8362188733-11">(</span><span class="n">Port</span><span class="p" data-group-id="8362188733-11">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Assuming that both the arguments and the results from the C functions are less
│ │ │ │  than 256, a simple encoding/decoding scheme is employed. In this scheme, <code class="inline">foo</code>
│ │ │ │  is represented by byte 1, <code class="inline">bar</code> is represented by 2, and the argument/result is
│ │ │ │ -represented by a single byte as well:</p><pre><code class="makeup erlang" translate="no"><span class="nf">encode</span><span class="p" data-group-id="8440978466-1">(</span><span class="p" data-group-id="8440978466-2">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="8440978466-2">}</span><span class="p" data-group-id="8440978466-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8440978466-3">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="8440978466-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="8440978466-4">(</span><span class="p" data-group-id="8440978466-5">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8440978466-5">}</span><span class="p" data-group-id="8440978466-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8440978466-6">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8440978466-6">]</span><span class="p">.</span><span class="w">
│ │ │ │ +represented by a single byte as well:</p><pre><code class="makeup erlang" translate="no"><span class="nf">encode</span><span class="p" data-group-id="6329375415-1">(</span><span class="p" data-group-id="6329375415-2">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="6329375415-2">}</span><span class="p" data-group-id="6329375415-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6329375415-3">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="6329375415-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="6329375415-4">(</span><span class="p" data-group-id="6329375415-5">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6329375415-5">}</span><span class="p" data-group-id="6329375415-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6329375415-6">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6329375415-6">]</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="8440978466-7">(</span><span class="p" data-group-id="8440978466-8">[</span><span class="n">Int</span><span class="p" data-group-id="8440978466-8">]</span><span class="p" data-group-id="8440978466-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>The resulting Erlang program, including functions for stopping the port and
│ │ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="6329375415-7">(</span><span class="p" data-group-id="6329375415-8">[</span><span class="n">Int</span><span class="p" data-group-id="6329375415-8">]</span><span class="p" data-group-id="6329375415-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>The resulting Erlang program, including functions for stopping the port and
│ │ │ │  detecting port failures, is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4614922975-1">(</span><span class="ss">complex5</span><span class="p" data-group-id="4614922975-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4614922975-2">(</span><span class="p" data-group-id="4614922975-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4614922975-3">]</span><span class="p" data-group-id="4614922975-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4614922975-4">(</span><span class="p" data-group-id="4614922975-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4614922975-5">]</span><span class="p" data-group-id="4614922975-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0217833467-1">(</span><span class="ss">complex5</span><span class="p" data-group-id="0217833467-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0217833467-2">(</span><span class="p" data-group-id="0217833467-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0217833467-3">]</span><span class="p" data-group-id="0217833467-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0217833467-4">(</span><span class="p" data-group-id="0217833467-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0217833467-5">]</span><span class="p" data-group-id="0217833467-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="4614922975-6">(</span><span class="n">SharedLib</span><span class="p" data-group-id="4614922975-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="4614922975-7">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="4614922975-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="0217833467-6">(</span><span class="n">SharedLib</span><span class="p" data-group-id="0217833467-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="0217833467-7">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="0217833467-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │  	</span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="4614922975-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="4614922975-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ │ -	</span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="4614922975-9">(</span><span class="p" data-group-id="4614922975-10">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="4614922975-10">}</span><span class="p" data-group-id="4614922975-9">)</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="0217833467-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="0217833467-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ │ +	</span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="0217833467-9">(</span><span class="p" data-group-id="0217833467-10">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="0217833467-10">}</span><span class="p" data-group-id="0217833467-9">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="4614922975-11">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4614922975-12">[</span><span class="n">SharedLib</span><span class="p" data-group-id="4614922975-12">]</span><span class="p" data-group-id="4614922975-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="0217833467-11">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0217833467-12">[</span><span class="n">SharedLib</span><span class="p" data-group-id="0217833467-12">]</span><span class="p" data-group-id="0217833467-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="4614922975-13">(</span><span class="n">SharedLib</span><span class="p" data-group-id="4614922975-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="4614922975-14">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4614922975-15">(</span><span class="p" data-group-id="4614922975-15">)</span><span class="p" data-group-id="4614922975-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="4614922975-16">(</span><span class="p" data-group-id="4614922975-17">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="4614922975-17">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4614922975-18">[</span><span class="p" data-group-id="4614922975-18">]</span><span class="p" data-group-id="4614922975-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="4614922975-19">(</span><span class="n">Port</span><span class="p" data-group-id="4614922975-19">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="0217833467-13">(</span><span class="n">SharedLib</span><span class="p" data-group-id="0217833467-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="0217833467-14">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0217833467-15">(</span><span class="p" data-group-id="0217833467-15">)</span><span class="p" data-group-id="0217833467-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="0217833467-16">(</span><span class="p" data-group-id="0217833467-17">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="0217833467-17">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0217833467-18">[</span><span class="p" data-group-id="0217833467-18">]</span><span class="p" data-group-id="0217833467-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="0217833467-19">(</span><span class="n">Port</span><span class="p" data-group-id="0217833467-19">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="4614922975-20">(</span><span class="p" data-group-id="4614922975-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="0217833467-20">(</span><span class="p" data-group-id="0217833467-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">stop</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="4614922975-21">(</span><span class="n">X</span><span class="p" data-group-id="4614922975-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="4614922975-22">(</span><span class="p" data-group-id="4614922975-23">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4614922975-23">}</span><span class="p" data-group-id="4614922975-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="4614922975-24">(</span><span class="n">Y</span><span class="p" data-group-id="4614922975-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="4614922975-25">(</span><span class="p" data-group-id="4614922975-26">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4614922975-26">}</span><span class="p" data-group-id="4614922975-25">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="0217833467-21">(</span><span class="n">X</span><span class="p" data-group-id="0217833467-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="0217833467-22">(</span><span class="p" data-group-id="0217833467-23">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0217833467-23">}</span><span class="p" data-group-id="0217833467-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="0217833467-24">(</span><span class="n">Y</span><span class="p" data-group-id="0217833467-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="0217833467-25">(</span><span class="p" data-group-id="0217833467-26">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0217833467-26">}</span><span class="p" data-group-id="0217833467-25">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="4614922975-27">(</span><span class="n">Msg</span><span class="p" data-group-id="4614922975-27">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4614922975-28">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4614922975-29">(</span><span class="p" data-group-id="4614922975-29">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4614922975-28">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="0217833467-27">(</span><span class="n">Msg</span><span class="p" data-group-id="0217833467-27">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0217833467-28">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0217833467-29">(</span><span class="p" data-group-id="0217833467-29">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0217833467-28">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="4614922975-30">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4614922975-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="0217833467-30">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0217833467-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  	    </span><span class="n">Result</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="4614922975-31">(</span><span class="n">Port</span><span class="p" data-group-id="4614922975-31">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="0217833467-31">(</span><span class="n">Port</span><span class="p" data-group-id="0217833467-31">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="4614922975-32">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4614922975-32">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4614922975-33">{</span><span class="nf">self</span><span class="p" data-group-id="4614922975-34">(</span><span class="p" data-group-id="4614922975-34">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4614922975-35">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="4614922975-36">(</span><span class="n">Msg</span><span class="p" data-group-id="4614922975-36">)</span><span class="p" data-group-id="4614922975-35">}</span><span class="p" data-group-id="4614922975-33">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="0217833467-32">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0217833467-32">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0217833467-33">{</span><span class="nf">self</span><span class="p" data-group-id="0217833467-34">(</span><span class="p" data-group-id="0217833467-34">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0217833467-35">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="0217833467-36">(</span><span class="n">Msg</span><span class="p" data-group-id="0217833467-36">)</span><span class="p" data-group-id="0217833467-35">}</span><span class="p" data-group-id="0217833467-33">}</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="4614922975-37">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4614922975-38">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4614922975-38">}</span><span class="p" data-group-id="4614922975-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4614922975-39">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="4614922975-40">(</span><span class="n">Data</span><span class="p" data-group-id="4614922975-40">)</span><span class="p" data-group-id="4614922975-39">}</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="0217833467-37">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0217833467-38">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0217833467-38">}</span><span class="p" data-group-id="0217833467-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0217833467-39">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="0217833467-40">(</span><span class="n">Data</span><span class="p" data-group-id="0217833467-40">)</span><span class="p" data-group-id="0217833467-39">}</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -	    </span><span class="nf">loop</span><span class="p" data-group-id="4614922975-41">(</span><span class="n">Port</span><span class="p" data-group-id="4614922975-41">)</span><span class="p">;</span><span class="w">
│ │ │ │ +	    </span><span class="nf">loop</span><span class="p" data-group-id="0217833467-41">(</span><span class="n">Port</span><span class="p" data-group-id="0217833467-41">)</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">stop</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4614922975-42">{</span><span class="nf">self</span><span class="p" data-group-id="4614922975-43">(</span><span class="p" data-group-id="4614922975-43">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="4614922975-42">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0217833467-42">{</span><span class="nf">self</span><span class="p" data-group-id="0217833467-43">(</span><span class="p" data-group-id="0217833467-43">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="0217833467-42">}</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="4614922975-44">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="4614922975-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="nf">exit</span><span class="p" data-group-id="4614922975-45">(</span><span class="ss">normal</span><span class="p" data-group-id="4614922975-45">)</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="0217833467-44">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="0217833467-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="nf">exit</span><span class="p" data-group-id="0217833467-45">(</span><span class="ss">normal</span><span class="p" data-group-id="0217833467-45">)</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="4614922975-46">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="4614922975-46">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4614922975-47">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4614922975-48">[</span><span class="n">Reason</span><span class="p" data-group-id="4614922975-48">]</span><span class="p" data-group-id="4614922975-47">)</span><span class="p">,</span><span class="w">
│ │ │ │ -	    </span><span class="nf">exit</span><span class="p" data-group-id="4614922975-49">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="4614922975-49">)</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="0217833467-46">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="0217833467-46">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0217833467-47">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0217833467-48">[</span><span class="n">Reason</span><span class="p" data-group-id="0217833467-48">]</span><span class="p" data-group-id="0217833467-47">)</span><span class="p">,</span><span class="w">
│ │ │ │ +	    </span><span class="nf">exit</span><span class="p" data-group-id="0217833467-49">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="0217833467-49">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="4614922975-50">(</span><span class="p" data-group-id="4614922975-51">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4614922975-51">}</span><span class="p" data-group-id="4614922975-50">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4614922975-52">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4614922975-52">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="4614922975-53">(</span><span class="p" data-group-id="4614922975-54">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4614922975-54">}</span><span class="p" data-group-id="4614922975-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4614922975-55">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4614922975-55">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="0217833467-50">(</span><span class="p" data-group-id="0217833467-51">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0217833467-51">}</span><span class="p" data-group-id="0217833467-50">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0217833467-52">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0217833467-52">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="0217833467-53">(</span><span class="p" data-group-id="0217833467-54">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0217833467-54">}</span><span class="p" data-group-id="0217833467-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0217833467-55">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0217833467-55">]</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="4614922975-56">(</span><span class="p" data-group-id="4614922975-57">[</span><span class="n">Int</span><span class="p" data-group-id="4614922975-57">]</span><span class="p" data-group-id="4614922975-56">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><h2 id="c-driver" class="section-heading">
│ │ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="0217833467-56">(</span><span class="p" data-group-id="0217833467-57">[</span><span class="n">Int</span><span class="p" data-group-id="0217833467-57">]</span><span class="p" data-group-id="0217833467-56">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><h2 id="c-driver" class="section-heading">
│ │ │ │    <a href="#c-driver" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">C Driver</span>
│ │ │ │  </h2>
│ │ │ │  <p>The C driver is a module that is compiled and linked into a shared library. It
│ │ │ │  uses a driver structure and includes the header file <code class="inline">erl_driver.h</code>.</p><p>The driver structure is filled with the driver name and function pointers. It is
│ │ │ │ @@ -252,22 +252,22 @@
│ │ │ │    <a href="#running-the-example" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Running the Example</span>
│ │ │ │  </h2>
│ │ │ │  <p><em>Step 1.</em> Compile the C code:</p><pre><code class="text">unix&gt; gcc -o example_drv.so -fpic -shared complex.c port_driver.c
│ │ │ │  windows&gt; cl -LD -MD -Fe example_drv.dll complex.c port_driver.c</code></pre><p><em>Step 2.</em> Start Erlang and compile the Erlang code:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="ss">erl</span><span class="w">
│ │ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="1854105968-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="1854105968-1">]</span><span class="w"> </span><span class="p" data-group-id="1854105968-2">[</span><span class="ss">source</span><span class="p" data-group-id="1854105968-2">]</span><span class="w"> </span><span class="p" data-group-id="1854105968-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="1854105968-3">]</span><span class="w"> </span><span class="p" data-group-id="1854105968-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="1854105968-4">]</span><span class="w"> </span><span class="p" data-group-id="1854105968-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="1854105968-5">]</span><span class="w"> </span><span class="p" data-group-id="1854105968-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1854105968-6">]</span><span class="w"> </span><span class="p" data-group-id="1854105968-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="1854105968-7">]</span><span class="w">
│ │ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="2418731546-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="2418731546-1">]</span><span class="w"> </span><span class="p" data-group-id="2418731546-2">[</span><span class="ss">source</span><span class="p" data-group-id="2418731546-2">]</span><span class="w"> </span><span class="p" data-group-id="2418731546-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="2418731546-3">]</span><span class="w"> </span><span class="p" data-group-id="2418731546-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="2418731546-4">]</span><span class="w"> </span><span class="p" data-group-id="2418731546-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="2418731546-5">]</span><span class="w"> </span><span class="p" data-group-id="2418731546-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="2418731546-6">]</span><span class="w"> </span><span class="p" data-group-id="2418731546-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="2418731546-7">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="1854105968-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="1854105968-9">(</span><span class="p" data-group-id="1854105968-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="1854105968-8">)</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="1854105968-10">(</span><span class="ss">complex5</span><span class="p" data-group-id="1854105968-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1854105968-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex5</span><span class="p" data-group-id="1854105968-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1743130045-1">(</span><span class="s">&quot;example_drv&quot;</span><span class="p" data-group-id="1743130045-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="2418731546-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="2418731546-9">(</span><span class="p" data-group-id="2418731546-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="2418731546-8">)</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="2418731546-10">(</span><span class="ss">complex5</span><span class="p" data-group-id="2418731546-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2418731546-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex5</span><span class="p" data-group-id="2418731546-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="5180301072-1">(</span><span class="s">&quot;example_drv&quot;</span><span class="p" data-group-id="5180301072-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">0.34</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="1743130045-2">(</span><span class="mi">3</span><span class="p" data-group-id="1743130045-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="5180301072-2">(</span><span class="mi">3</span><span class="p" data-group-id="5180301072-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="1743130045-3">(</span><span class="mi">5</span><span class="p" data-group-id="1743130045-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="5180301072-3">(</span><span class="mi">5</span><span class="p" data-group-id="5180301072-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">10</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="1743130045-4">(</span><span class="p" data-group-id="1743130045-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="5180301072-4">(</span><span class="p" data-group-id="5180301072-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">stop</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/c_port.xhtml
│ │ │ │ @@ -53,101 +53,101 @@
│ │ │ │  external program, if it is written properly).</p><p>The port is created using the BIF <a href="../../../lib/../erts/doc/html/erlang.html#open_port/2"><code class="inline">open_port/2</code></a> with
│ │ │ │  <code class="inline">{spawn,ExtPrg}</code> as the first argument. The string <code class="inline">ExtPrg</code> is the name of the
│ │ │ │  external program, including any command line arguments. The second argument is a
│ │ │ │  list of options, in this case only <code class="inline">{packet,2}</code>. This option says that a 2 byte
│ │ │ │  length indicator is to be used to simplify the communication between C and
│ │ │ │  Erlang. The Erlang port automatically adds the length indicator, but this must
│ │ │ │  be done explicitly in the external C program.</p><p>The process is also set to trap exits, which enables detection of failure of the
│ │ │ │ -external program:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6558168004-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="6558168004-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6558168004-2">(</span><span class="p" data-group-id="6558168004-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6558168004-3">]</span><span class="p" data-group-id="6558168004-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +external program:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8166997990-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="8166997990-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8166997990-2">(</span><span class="p" data-group-id="8166997990-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8166997990-3">]</span><span class="p" data-group-id="8166997990-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="6558168004-4">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="6558168004-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -  </span><span class="nf">spawn</span><span class="p" data-group-id="6558168004-5">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6558168004-6">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="6558168004-6">]</span><span class="p" data-group-id="6558168004-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="8166997990-4">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="8166997990-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="nf">spawn</span><span class="p" data-group-id="8166997990-5">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8166997990-6">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="8166997990-6">]</span><span class="p" data-group-id="8166997990-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="6558168004-7">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="6558168004-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -  </span><span class="nf">register</span><span class="p" data-group-id="6558168004-8">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6558168004-9">(</span><span class="p" data-group-id="6558168004-9">)</span><span class="p" data-group-id="6558168004-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="nf">process_flag</span><span class="p" data-group-id="6558168004-10">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="6558168004-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="6558168004-11">(</span><span class="p" data-group-id="6558168004-12">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="6558168004-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6558168004-13">[</span><span class="p" data-group-id="6558168004-14">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="6558168004-14">}</span><span class="p" data-group-id="6558168004-13">]</span><span class="p" data-group-id="6558168004-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="nf">loop</span><span class="p" data-group-id="6558168004-15">(</span><span class="n">Port</span><span class="p" data-group-id="6558168004-15">)</span><span class="p">.</span></code></pre><p>Now <code class="inline">complex1:foo/1</code> and <code class="inline">complex1:bar/1</code> can be implemented. Both send a
│ │ │ │ -message to the <code class="inline">complex</code> process and receive the following replies:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="6148966198-1">(</span><span class="n">X</span><span class="p" data-group-id="6148966198-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -  </span><span class="nf">call_port</span><span class="p" data-group-id="6148966198-2">(</span><span class="p" data-group-id="6148966198-3">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="6148966198-3">}</span><span class="p" data-group-id="6148966198-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="6148966198-4">(</span><span class="n">Y</span><span class="p" data-group-id="6148966198-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -  </span><span class="nf">call_port</span><span class="p" data-group-id="6148966198-5">(</span><span class="p" data-group-id="6148966198-6">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6148966198-6">}</span><span class="p" data-group-id="6148966198-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="8166997990-7">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="8166997990-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="nf">register</span><span class="p" data-group-id="8166997990-8">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8166997990-9">(</span><span class="p" data-group-id="8166997990-9">)</span><span class="p" data-group-id="8166997990-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="nf">process_flag</span><span class="p" data-group-id="8166997990-10">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="8166997990-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="8166997990-11">(</span><span class="p" data-group-id="8166997990-12">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="8166997990-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8166997990-13">[</span><span class="p" data-group-id="8166997990-14">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="8166997990-14">}</span><span class="p" data-group-id="8166997990-13">]</span><span class="p" data-group-id="8166997990-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="nf">loop</span><span class="p" data-group-id="8166997990-15">(</span><span class="n">Port</span><span class="p" data-group-id="8166997990-15">)</span><span class="p">.</span></code></pre><p>Now <code class="inline">complex1:foo/1</code> and <code class="inline">complex1:bar/1</code> can be implemented. Both send a
│ │ │ │ +message to the <code class="inline">complex</code> process and receive the following replies:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="2823913581-1">(</span><span class="n">X</span><span class="p" data-group-id="2823913581-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="nf">call_port</span><span class="p" data-group-id="2823913581-2">(</span><span class="p" data-group-id="2823913581-3">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="2823913581-3">}</span><span class="p" data-group-id="2823913581-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="2823913581-4">(</span><span class="n">Y</span><span class="p" data-group-id="2823913581-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="nf">call_port</span><span class="p" data-group-id="2823913581-5">(</span><span class="p" data-group-id="2823913581-6">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2823913581-6">}</span><span class="p" data-group-id="2823913581-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="6148966198-7">(</span><span class="n">Msg</span><span class="p" data-group-id="6148966198-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -  </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6148966198-8">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6148966198-9">(</span><span class="p" data-group-id="6148966198-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="6148966198-8">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="2823913581-7">(</span><span class="n">Msg</span><span class="p" data-group-id="2823913581-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2823913581-8">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2823913581-9">(</span><span class="p" data-group-id="2823913581-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="2823913581-8">}</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6148966198-10">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="6148966198-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2823913581-10">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="2823913581-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │        </span><span class="n">Result</span><span class="w">
│ │ │ │ -  </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">complex</code> process does the following:</p><ul><li>Encodes the message into a sequence of bytes.</li><li>Sends it to the port.</li><li>Waits for a reply.</li><li>Decodes the reply.</li><li>Sends it back to the caller:</li></ul><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="2873576082-1">(</span><span class="n">Port</span><span class="p" data-group-id="2873576082-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">complex</code> process does the following:</p><ul><li>Encodes the message into a sequence of bytes.</li><li>Sends it to the port.</li><li>Waits for a reply.</li><li>Decodes the reply.</li><li>Sends it back to the caller:</li></ul><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="3023553180-1">(</span><span class="n">Port</span><span class="p" data-group-id="3023553180-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │    </span><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2873576082-2">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="2873576082-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -      </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2873576082-3">{</span><span class="nf">self</span><span class="p" data-group-id="2873576082-4">(</span><span class="p" data-group-id="2873576082-4">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2873576082-5">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="2873576082-6">(</span><span class="n">Msg</span><span class="p" data-group-id="2873576082-6">)</span><span class="p" data-group-id="2873576082-5">}</span><span class="p" data-group-id="2873576082-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3023553180-2">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="3023553180-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +      </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3023553180-3">{</span><span class="nf">self</span><span class="p" data-group-id="3023553180-4">(</span><span class="p" data-group-id="3023553180-4">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3023553180-5">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="3023553180-6">(</span><span class="n">Msg</span><span class="p" data-group-id="3023553180-6">)</span><span class="p" data-group-id="3023553180-5">}</span><span class="p" data-group-id="3023553180-3">}</span><span class="p">,</span><span class="w">
│ │ │ │        </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="2873576082-7">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2873576082-8">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2873576082-8">}</span><span class="p" data-group-id="2873576082-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -          </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2873576082-9">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="2873576082-10">(</span><span class="n">Data</span><span class="p" data-group-id="2873576082-10">)</span><span class="p" data-group-id="2873576082-9">}</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3023553180-7">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3023553180-8">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3023553180-8">}</span><span class="p" data-group-id="3023553180-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +          </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3023553180-9">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="3023553180-10">(</span><span class="n">Data</span><span class="p" data-group-id="3023553180-10">)</span><span class="p" data-group-id="3023553180-9">}</span><span class="w">
│ │ │ │        </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -      </span><span class="nf">loop</span><span class="p" data-group-id="2873576082-11">(</span><span class="n">Port</span><span class="p" data-group-id="2873576082-11">)</span><span class="w">
│ │ │ │ +      </span><span class="nf">loop</span><span class="p" data-group-id="3023553180-11">(</span><span class="n">Port</span><span class="p" data-group-id="3023553180-11">)</span><span class="w">
│ │ │ │    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Assuming that both the arguments and the results from the C functions are less
│ │ │ │  than 256, a simple encoding/decoding scheme is employed. In this scheme, <code class="inline">foo</code>
│ │ │ │  is represented by byte 1, <code class="inline">bar</code> is represented by 2, and the argument/result is
│ │ │ │ -represented by a single byte as well:</p><pre><code class="makeup erlang" translate="no"><span class="nf">encode</span><span class="p" data-group-id="8888184383-1">(</span><span class="p" data-group-id="8888184383-2">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="8888184383-2">}</span><span class="p" data-group-id="8888184383-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8888184383-3">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="8888184383-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="8888184383-4">(</span><span class="p" data-group-id="8888184383-5">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8888184383-5">}</span><span class="p" data-group-id="8888184383-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8888184383-6">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8888184383-6">]</span><span class="p">.</span><span class="w">
│ │ │ │ +represented by a single byte as well:</p><pre><code class="makeup erlang" translate="no"><span class="nf">encode</span><span class="p" data-group-id="2356334517-1">(</span><span class="p" data-group-id="2356334517-2">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="2356334517-2">}</span><span class="p" data-group-id="2356334517-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2356334517-3">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="2356334517-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="2356334517-4">(</span><span class="p" data-group-id="2356334517-5">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2356334517-5">}</span><span class="p" data-group-id="2356334517-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2356334517-6">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2356334517-6">]</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="8888184383-7">(</span><span class="p" data-group-id="8888184383-8">[</span><span class="n">Int</span><span class="p" data-group-id="8888184383-8">]</span><span class="p" data-group-id="8888184383-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>The resulting Erlang program, including functionality for stopping the port and
│ │ │ │ -detecting port failures, is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4188799582-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="4188799582-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4188799582-2">(</span><span class="p" data-group-id="4188799582-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4188799582-3">]</span><span class="p" data-group-id="4188799582-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4188799582-4">(</span><span class="p" data-group-id="4188799582-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4188799582-5">]</span><span class="p" data-group-id="4188799582-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="4188799582-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="4188799582-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="4188799582-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4188799582-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="4188799582-8">]</span><span class="p" data-group-id="4188799582-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="4188799582-9">(</span><span class="p" data-group-id="4188799582-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="2356334517-7">(</span><span class="p" data-group-id="2356334517-8">[</span><span class="n">Int</span><span class="p" data-group-id="2356334517-8">]</span><span class="p" data-group-id="2356334517-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>The resulting Erlang program, including functionality for stopping the port and
│ │ │ │ +detecting port failures, is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4983907343-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="4983907343-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4983907343-2">(</span><span class="p" data-group-id="4983907343-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4983907343-3">]</span><span class="p" data-group-id="4983907343-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4983907343-4">(</span><span class="p" data-group-id="4983907343-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4983907343-5">]</span><span class="p" data-group-id="4983907343-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="4983907343-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="4983907343-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="4983907343-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4983907343-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="4983907343-8">]</span><span class="p" data-group-id="4983907343-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="4983907343-9">(</span><span class="p" data-group-id="4983907343-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">stop</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="4188799582-10">(</span><span class="n">X</span><span class="p" data-group-id="4188799582-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="4188799582-11">(</span><span class="p" data-group-id="4188799582-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4188799582-12">}</span><span class="p" data-group-id="4188799582-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="4188799582-13">(</span><span class="n">Y</span><span class="p" data-group-id="4188799582-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="4188799582-14">(</span><span class="p" data-group-id="4188799582-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4188799582-15">}</span><span class="p" data-group-id="4188799582-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="4983907343-10">(</span><span class="n">X</span><span class="p" data-group-id="4983907343-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="4983907343-11">(</span><span class="p" data-group-id="4983907343-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4983907343-12">}</span><span class="p" data-group-id="4983907343-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="4983907343-13">(</span><span class="n">Y</span><span class="p" data-group-id="4983907343-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="4983907343-14">(</span><span class="p" data-group-id="4983907343-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4983907343-15">}</span><span class="p" data-group-id="4983907343-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="4188799582-16">(</span><span class="n">Msg</span><span class="p" data-group-id="4188799582-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4188799582-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4188799582-18">(</span><span class="p" data-group-id="4188799582-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4188799582-17">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="4983907343-16">(</span><span class="n">Msg</span><span class="p" data-group-id="4983907343-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4983907343-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4983907343-18">(</span><span class="p" data-group-id="4983907343-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4983907343-17">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="4188799582-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4188799582-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="4983907343-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4983907343-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  	    </span><span class="n">Result</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="4188799582-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="4188799582-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="4188799582-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4188799582-22">(</span><span class="p" data-group-id="4188799582-22">)</span><span class="p" data-group-id="4188799582-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="4188799582-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4188799582-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="4188799582-24">(</span><span class="p" data-group-id="4188799582-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="4188799582-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4188799582-26">[</span><span class="p" data-group-id="4188799582-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="4188799582-27">}</span><span class="p" data-group-id="4188799582-26">]</span><span class="p" data-group-id="4188799582-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="4188799582-28">(</span><span class="n">Port</span><span class="p" data-group-id="4188799582-28">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="4983907343-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="4983907343-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="4983907343-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4983907343-22">(</span><span class="p" data-group-id="4983907343-22">)</span><span class="p" data-group-id="4983907343-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="4983907343-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4983907343-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="4983907343-24">(</span><span class="p" data-group-id="4983907343-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="4983907343-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4983907343-26">[</span><span class="p" data-group-id="4983907343-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="4983907343-27">}</span><span class="p" data-group-id="4983907343-26">]</span><span class="p" data-group-id="4983907343-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="4983907343-28">(</span><span class="n">Port</span><span class="p" data-group-id="4983907343-28">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="4188799582-29">(</span><span class="n">Port</span><span class="p" data-group-id="4188799582-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="4983907343-29">(</span><span class="n">Port</span><span class="p" data-group-id="4983907343-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="4188799582-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4188799582-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4188799582-31">{</span><span class="nf">self</span><span class="p" data-group-id="4188799582-32">(</span><span class="p" data-group-id="4188799582-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4188799582-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="4188799582-34">(</span><span class="n">Msg</span><span class="p" data-group-id="4188799582-34">)</span><span class="p" data-group-id="4188799582-33">}</span><span class="p" data-group-id="4188799582-31">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="4983907343-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4983907343-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4983907343-31">{</span><span class="nf">self</span><span class="p" data-group-id="4983907343-32">(</span><span class="p" data-group-id="4983907343-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4983907343-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="4983907343-34">(</span><span class="n">Msg</span><span class="p" data-group-id="4983907343-34">)</span><span class="p" data-group-id="4983907343-33">}</span><span class="p" data-group-id="4983907343-31">}</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="4188799582-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4188799582-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4188799582-36">}</span><span class="p" data-group-id="4188799582-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4188799582-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="4188799582-38">(</span><span class="n">Data</span><span class="p" data-group-id="4188799582-38">)</span><span class="p" data-group-id="4188799582-37">}</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="4983907343-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4983907343-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4983907343-36">}</span><span class="p" data-group-id="4983907343-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4983907343-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="4983907343-38">(</span><span class="n">Data</span><span class="p" data-group-id="4983907343-38">)</span><span class="p" data-group-id="4983907343-37">}</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -	    </span><span class="nf">loop</span><span class="p" data-group-id="4188799582-39">(</span><span class="n">Port</span><span class="p" data-group-id="4188799582-39">)</span><span class="p">;</span><span class="w">
│ │ │ │ +	    </span><span class="nf">loop</span><span class="p" data-group-id="4983907343-39">(</span><span class="n">Port</span><span class="p" data-group-id="4983907343-39">)</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">stop</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4188799582-40">{</span><span class="nf">self</span><span class="p" data-group-id="4188799582-41">(</span><span class="p" data-group-id="4188799582-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="4188799582-40">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4983907343-40">{</span><span class="nf">self</span><span class="p" data-group-id="4983907343-41">(</span><span class="p" data-group-id="4983907343-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="4983907343-40">}</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="4188799582-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="4188799582-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="nf">exit</span><span class="p" data-group-id="4188799582-43">(</span><span class="ss">normal</span><span class="p" data-group-id="4188799582-43">)</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="4983907343-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="4983907343-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="nf">exit</span><span class="p" data-group-id="4983907343-43">(</span><span class="ss">normal</span><span class="p" data-group-id="4983907343-43">)</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="4188799582-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="4188799582-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="nf">exit</span><span class="p" data-group-id="4188799582-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="4188799582-45">)</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="4983907343-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="4983907343-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	    </span><span class="nf">exit</span><span class="p" data-group-id="4983907343-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="4983907343-45">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="4188799582-46">(</span><span class="p" data-group-id="4188799582-47">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4188799582-47">}</span><span class="p" data-group-id="4188799582-46">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4188799582-48">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4188799582-48">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="4188799582-49">(</span><span class="p" data-group-id="4188799582-50">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4188799582-50">}</span><span class="p" data-group-id="4188799582-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4188799582-51">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4188799582-51">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="4983907343-46">(</span><span class="p" data-group-id="4983907343-47">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4983907343-47">}</span><span class="p" data-group-id="4983907343-46">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4983907343-48">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4983907343-48">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="4983907343-49">(</span><span class="p" data-group-id="4983907343-50">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4983907343-50">}</span><span class="p" data-group-id="4983907343-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4983907343-51">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4983907343-51">]</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="4188799582-52">(</span><span class="p" data-group-id="4188799582-53">[</span><span class="n">Int</span><span class="p" data-group-id="4188799582-53">]</span><span class="p" data-group-id="4188799582-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><h2 id="c-program" class="section-heading">
│ │ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="4983907343-52">(</span><span class="p" data-group-id="4983907343-53">[</span><span class="n">Int</span><span class="p" data-group-id="4983907343-53">]</span><span class="p" data-group-id="4983907343-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><h2 id="c-program" class="section-heading">
│ │ │ │    <a href="#c-program" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">C Program</span>
│ │ │ │  </h2>
│ │ │ │  <p>On the C side, it is necessary to write functions for receiving and sending data
│ │ │ │  with 2 byte length indicators from/to Erlang. By default, the C program is to
│ │ │ │ @@ -238,22 +238,22 @@
│ │ │ │  and terminates.</p><h2 id="running-the-example" class="section-heading">
│ │ │ │    <a href="#running-the-example" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Running the Example</span>
│ │ │ │  </h2>
│ │ │ │  <p><em>Step 1.</em> Compile the C code:</p><pre><code class="text">$ gcc -o extprg complex.c erl_comm.c port.c</code></pre><p><em>Step 2.</em> Start Erlang and compile the Erlang code:</p><pre><code class="makeup erlang" translate="no"><span class="sc">$ </span><span class="ss">erl</span><span class="w">
│ │ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="7881009014-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="7881009014-1">]</span><span class="w"> </span><span class="p" data-group-id="7881009014-2">[</span><span class="ss">source</span><span class="p" data-group-id="7881009014-2">]</span><span class="w"> </span><span class="p" data-group-id="7881009014-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="7881009014-3">]</span><span class="w"> </span><span class="p" data-group-id="7881009014-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="7881009014-4">]</span><span class="w"> </span><span class="p" data-group-id="7881009014-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="7881009014-5">]</span><span class="w"> </span><span class="p" data-group-id="7881009014-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="7881009014-6">]</span><span class="w"> </span><span class="p" data-group-id="7881009014-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="7881009014-7">]</span><span class="w">
│ │ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="3130139195-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="3130139195-1">]</span><span class="w"> </span><span class="p" data-group-id="3130139195-2">[</span><span class="ss">source</span><span class="p" data-group-id="3130139195-2">]</span><span class="w"> </span><span class="p" data-group-id="3130139195-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="3130139195-3">]</span><span class="w"> </span><span class="p" data-group-id="3130139195-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="3130139195-4">]</span><span class="w"> </span><span class="p" data-group-id="3130139195-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="3130139195-5">]</span><span class="w"> </span><span class="p" data-group-id="3130139195-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="3130139195-6">]</span><span class="w"> </span><span class="p" data-group-id="3130139195-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="3130139195-7">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="7881009014-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="7881009014-9">(</span><span class="p" data-group-id="7881009014-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="7881009014-8">)</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="7881009014-10">(</span><span class="ss">complex1</span><span class="p" data-group-id="7881009014-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7881009014-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex1</span><span class="p" data-group-id="7881009014-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="9733444689-1">(</span><span class="s">&quot;./extprg&quot;</span><span class="p" data-group-id="9733444689-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="3130139195-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="3130139195-9">(</span><span class="p" data-group-id="3130139195-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="3130139195-8">)</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="3130139195-10">(</span><span class="ss">complex1</span><span class="p" data-group-id="3130139195-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3130139195-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex1</span><span class="p" data-group-id="3130139195-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1142253001-1">(</span><span class="s">&quot;./extprg&quot;</span><span class="p" data-group-id="1142253001-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">0.34</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="9733444689-2">(</span><span class="mi">3</span><span class="p" data-group-id="9733444689-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="1142253001-2">(</span><span class="mi">3</span><span class="p" data-group-id="1142253001-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="9733444689-3">(</span><span class="mi">5</span><span class="p" data-group-id="9733444689-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="1142253001-3">(</span><span class="mi">5</span><span class="p" data-group-id="1142253001-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">10</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="9733444689-4">(</span><span class="p" data-group-id="9733444689-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="1142253001-4">(</span><span class="p" data-group-id="1142253001-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">stop</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/bit_syntax.xhtml
│ │ │ │ @@ -24,48 +24,48 @@
│ │ │ │    <a href="#introduction" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Introduction</span>
│ │ │ │  </h2>
│ │ │ │  <p>The complete specification for the bit syntax appears in the
│ │ │ │  <a href="../../../lib/../system/doc/html/expressions.xhtml#bit-syntax-expressions">Reference Manual</a>.</p><p>In Erlang, a Bin is used for constructing binaries and matching binary patterns.
│ │ │ │ -A Bin is written with the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0199729754-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="0199729754-1">&gt;&gt;</span></code></pre><p>A Bin is a low-level sequence of bits or bytes. The purpose of a Bin is to
│ │ │ │ -enable construction of binaries:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4977838947-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="4977838947-1">&gt;&gt;</span></code></pre><p>All elements must be bound. Or match a binary:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9769510366-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="9769510366-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin</span></code></pre><p>Here, <code class="inline">Bin</code> is bound and the elements are bound or unbound, as in any match.</p><p>A Bin does not need to consist of a whole number of bytes.</p><p>A <em>bitstring</em> is a sequence of zero or more bits, where the number of bits does
│ │ │ │ +A Bin is written with the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6492352954-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="6492352954-1">&gt;&gt;</span></code></pre><p>A Bin is a low-level sequence of bits or bytes. The purpose of a Bin is to
│ │ │ │ +enable construction of binaries:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6943708568-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="6943708568-1">&gt;&gt;</span></code></pre><p>All elements must be bound. Or match a binary:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4883691023-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="4883691023-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin</span></code></pre><p>Here, <code class="inline">Bin</code> is bound and the elements are bound or unbound, as in any match.</p><p>A Bin does not need to consist of a whole number of bytes.</p><p>A <em>bitstring</em> is a sequence of zero or more bits, where the number of bits does
│ │ │ │  not need to be divisible by 8. If the number of bits is divisible by 8, the
│ │ │ │  bitstring is also a binary.</p><p>Each element specifies a certain <em>segment</em> of the bitstring. A segment is a set
│ │ │ │  of contiguous bits of the binary (not necessarily on a byte boundary). The first
│ │ │ │  element specifies the initial segment, the second element specifies the
│ │ │ │  following segment, and so on.</p><p>The following examples illustrate how binaries are constructed, or matched, and
│ │ │ │  how elements and tails are specified.</p><h3 id="examples" class="section-heading">
│ │ │ │    <a href="#examples" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Examples</span>
│ │ │ │  </h3>
│ │ │ │  <p><em>Example 1:</em> A binary can be constructed from a set of constants or a string
│ │ │ │ -literal:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin11</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1140971819-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">17</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="1140971819-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Bin12</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1140971819-2">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1140971819-2">&gt;&gt;</span></code></pre><p>This gives two binaries of size 3, with the following evaluations:</p><ul><li><a href="../../../lib/../erts/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin11)</code></a> evaluates to <code class="inline">[1, 17, 42]</code>.</li><li><a href="../../../lib/../erts/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin12)</code></a> evaluates to <code class="inline">[97, 98, 99]</code>.</li></ul><p><em>Example 2:</em> Similarly, a binary can be constructed from a set of bound
│ │ │ │ +literal:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin11</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5041769632-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">17</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="5041769632-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Bin12</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5041769632-2">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="5041769632-2">&gt;&gt;</span></code></pre><p>This gives two binaries of size 3, with the following evaluations:</p><ul><li><a href="../../../lib/../erts/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin11)</code></a> evaluates to <code class="inline">[1, 17, 42]</code>.</li><li><a href="../../../lib/../erts/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin12)</code></a> evaluates to <code class="inline">[97, 98, 99]</code>.</li></ul><p><em>Example 2:</em> Similarly, a binary can be constructed from a set of bound
│ │ │ │  variables:</p><pre><code class="makeup erlang" translate="no"><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">17</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4563604912-1">&lt;&lt;</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="4563604912-1">&gt;&gt;</span></code></pre><p>This gives a binary of size 4. Here, a <em>size expression</em> is used for the
│ │ │ │ +</span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9992706920-1">&lt;&lt;</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9992706920-1">&gt;&gt;</span></code></pre><p>This gives a binary of size 4. Here, a <em>size expression</em> is used for the
│ │ │ │  variable <code class="inline">C</code> to specify a 16-bit segment of <code class="inline">Bin2</code>.</p><p><a href="../../../lib/../erts/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin2)</code></a> evaluates to <code class="inline">[1, 17, 00, 42]</code>.</p><p><em>Example 3:</em> A Bin can also be used for matching. <code class="inline">D</code>, <code class="inline">E</code>, and <code class="inline">F</code> are unbound
│ │ │ │ -variables, and <code class="inline">Bin2</code> is bound, as in Example 2:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2228914411-1">&lt;&lt;</span><span class="n">D</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2228914411-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin2</span></code></pre><p>This gives <code class="inline">D = 273</code>, <code class="inline">E = 00</code>, and F binds to a binary of size 1:
│ │ │ │ +variables, and <code class="inline">Bin2</code> is bound, as in Example 2:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7723972060-1">&lt;&lt;</span><span class="n">D</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7723972060-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin2</span></code></pre><p>This gives <code class="inline">D = 273</code>, <code class="inline">E = 00</code>, and F binds to a binary of size 1:
│ │ │ │  <code class="inline">binary_to_list(F) = [42]</code>.</p><p><em>Example 4:</em> The following is a more elaborate example of matching. Here,
│ │ │ │  <code class="inline">Dgram</code> is bound to the consecutive bytes of an IP datagram of IP protocol
│ │ │ │ -version 4. The ambition is to extract the header and the data of the datagram:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4107951771-1">(</span><span class="n">IP_VERSION</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="4107951771-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4107951771-2">(</span><span class="n">IP_MIN_HDR_LEN</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="4107951771-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +version 4. The ambition is to extract the header and the data of the datagram:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2640078160-1">(</span><span class="n">IP_VERSION</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="2640078160-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2640078160-2">(</span><span class="n">IP_MIN_HDR_LEN</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="2640078160-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">DgramSize</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">byte_size</span><span class="p" data-group-id="4107951771-3">(</span><span class="n">Dgram</span><span class="p" data-group-id="4107951771-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">DgramSize</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">byte_size</span><span class="p" data-group-id="2640078160-3">(</span><span class="n">Dgram</span><span class="p" data-group-id="2640078160-3">)</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="k">case</span><span class="w"> </span><span class="n">Dgram</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4107951771-4">&lt;&lt;</span><span class="o">?</span><span class="n">IP_VERSION</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">HLen</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">SrvcType</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="n">TotLen</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2640078160-4">&lt;&lt;</span><span class="o">?</span><span class="n">IP_VERSION</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">HLen</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">SrvcType</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="n">TotLen</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w">
│ │ │ │        </span><span class="n">ID</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w"> </span><span class="n">Flgs</span><span class="p">:</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">FragOff</span><span class="p">:</span><span class="mi">13</span><span class="p">,</span><span class="w">
│ │ │ │        </span><span class="n">TTL</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="n">Proto</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="n">HdrChkSum</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w">
│ │ │ │        </span><span class="n">SrcIP</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="w">
│ │ │ │ -      </span><span class="n">DestIP</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="w"> </span><span class="n">RestDgram</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4107951771-4">&gt;&gt;</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">HLen</span><span class="o">&gt;=</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="o">*</span><span class="n">HLen</span><span class="o">=&lt;</span><span class="n">DgramSize</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="n">OptsLen</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">4</span><span class="o">*</span><span class="p" data-group-id="4107951771-5">(</span><span class="n">HLen</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">?</span><span class="n">IP_MIN_HDR_LEN</span><span class="p" data-group-id="4107951771-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="4107951771-6">&lt;&lt;</span><span class="n">Opts</span><span class="p">:</span><span class="n">OptsLen</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Data</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4107951771-6">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RestDgram</span><span class="p">,</span><span class="w">
│ │ │ │ +      </span><span class="n">DestIP</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="w"> </span><span class="n">RestDgram</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2640078160-4">&gt;&gt;</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">HLen</span><span class="o">&gt;=</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="o">*</span><span class="n">HLen</span><span class="o">=&lt;</span><span class="n">DgramSize</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="n">OptsLen</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">4</span><span class="o">*</span><span class="p" data-group-id="2640078160-5">(</span><span class="n">HLen</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">?</span><span class="n">IP_MIN_HDR_LEN</span><span class="p" data-group-id="2640078160-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="2640078160-6">&lt;&lt;</span><span class="n">Opts</span><span class="p">:</span><span class="n">OptsLen</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Data</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2640078160-6">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RestDgram</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>Here, the segment corresponding to the <code class="inline">Opts</code> variable has a <em>type modifier</em>,
│ │ │ │  specifying that <code class="inline">Opts</code> is to bind to a binary. All other variables have the
│ │ │ │  default type equal to unsigned integer.</p><p>An IP datagram header is of variable length. This length is measured in the
│ │ │ │  number of 32-bit words and is given in the segment corresponding to <code class="inline">HLen</code>. The
│ │ │ │  minimum value of <code class="inline">HLen</code> is 5. It is the segment corresponding to <code class="inline">Opts</code> that is
│ │ │ │  variable, so if <code class="inline">HLen</code> is equal to 5, <code class="inline">Opts</code> becomes an empty binary.</p><p>The tail variables <code class="inline">RestDgram</code> and <code class="inline">Data</code> bind to binaries, as all tail
│ │ │ │ @@ -123,77 +123,77 @@
│ │ │ │  <p>This section describes the rules for constructing binaries using the bit syntax.
│ │ │ │  Unlike when constructing lists or tuples, the construction of a binary can fail
│ │ │ │  with a <code class="inline">badarg</code> exception.</p><p>There can be zero or more segments in a binary to be constructed. The expression
│ │ │ │  <code class="inline">&lt;&lt;&gt;&gt;</code> constructs a zero length binary.</p><p>Each segment in a binary can consist of zero or more bits. There are no
│ │ │ │  alignment rules for individual segments of type <code class="inline">integer</code> and <code class="inline">float</code>. For
│ │ │ │  binaries and bitstrings without size, the unit specifies the alignment. Since
│ │ │ │  the default alignment for the <code class="inline">binary</code> type is 8, the size of a binary segment
│ │ │ │ -must be a multiple of 8 bits, that is, only whole bytes.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8865289941-1">&lt;&lt;</span><span class="n">Bin</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Bitstring</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="8865289941-1">&gt;&gt;</span></code></pre><p>The variable <code class="inline">Bin</code> must contain a whole number of bytes, because the <code class="inline">binary</code>
│ │ │ │ +must be a multiple of 8 bits, that is, only whole bytes.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0323475920-1">&lt;&lt;</span><span class="n">Bin</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Bitstring</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="0323475920-1">&gt;&gt;</span></code></pre><p>The variable <code class="inline">Bin</code> must contain a whole number of bytes, because the <code class="inline">binary</code>
│ │ │ │  type defaults to <code class="inline">unit:8</code>. A <code class="inline">badarg</code> exception is generated if <code class="inline">Bin</code> consists
│ │ │ │  of, for example, 17 bits.</p><p>The <code class="inline">Bitstring</code> variable can consist of any number of bits, for example, 0, 1,
│ │ │ │  8, 11, 17, 42, and so on. This is because the default <code class="inline">unit</code> for bitstrings
│ │ │ │  is 1.</p><p>For clarity, it is recommended not to change the unit size for binaries.
│ │ │ │  Instead, use <code class="inline">binary</code> when you need byte alignment and <code class="inline">bitstring</code> when you need
│ │ │ │  bit alignment.</p><p>The following example successfully constructs a bitstring of 7 bits, provided
│ │ │ │ -that all of X and Y are integers:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1239968130-1">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="mi">1</span><span class="p">,</span><span class="n">Y</span><span class="p">:</span><span class="mi">6</span><span class="p" data-group-id="1239968130-1">&gt;&gt;</span></code></pre><p>As mentioned earlier, segments have the following general syntax:</p><p><code class="inline">Value:Size/TypeSpecifierList</code></p><p>When constructing binaries, <code class="inline">Value</code> and <code class="inline">Size</code> can be any Erlang expression.
│ │ │ │ +that all of X and Y are integers:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4481895008-1">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="mi">1</span><span class="p">,</span><span class="n">Y</span><span class="p">:</span><span class="mi">6</span><span class="p" data-group-id="4481895008-1">&gt;&gt;</span></code></pre><p>As mentioned earlier, segments have the following general syntax:</p><p><code class="inline">Value:Size/TypeSpecifierList</code></p><p>When constructing binaries, <code class="inline">Value</code> and <code class="inline">Size</code> can be any Erlang expression.
│ │ │ │  However, for syntactical reasons, both <code class="inline">Value</code> and <code class="inline">Size</code> must be enclosed in
│ │ │ │  parentheses if the expression consists of anything more than a single literal or
│ │ │ │ -a variable. The following gives a compiler syntax error:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0183907578-1">&lt;&lt;</span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="0183907578-1">&gt;&gt;</span></code></pre><p>This expression must be rewritten into the following, to be accepted by the
│ │ │ │ -compiler:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3025652080-1">&lt;&lt;</span><span class="p" data-group-id="3025652080-2">(</span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="3025652080-2">)</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="3025652080-1">&gt;&gt;</span></code></pre><h3 id="including-literal-strings" class="section-heading">
│ │ │ │ +a variable. The following gives a compiler syntax error:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7517923527-1">&lt;&lt;</span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="7517923527-1">&gt;&gt;</span></code></pre><p>This expression must be rewritten into the following, to be accepted by the
│ │ │ │ +compiler:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3698565703-1">&lt;&lt;</span><span class="p" data-group-id="3698565703-2">(</span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="3698565703-2">)</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="3698565703-1">&gt;&gt;</span></code></pre><h3 id="including-literal-strings" class="section-heading">
│ │ │ │    <a href="#including-literal-strings" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Including Literal Strings</span>
│ │ │ │  </h3>
│ │ │ │ -<p>A literal string can be written instead of an element:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7917033109-1">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="7917033109-1">&gt;&gt;</span></code></pre><p>This is syntactic sugar for the following:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8919952051-1">&lt;&lt;</span><span class="sc">$h</span><span class="p">,</span><span class="sc">$e</span><span class="p">,</span><span class="sc">$l</span><span class="p">,</span><span class="sc">$l</span><span class="p">,</span><span class="sc">$o</span><span class="p" data-group-id="8919952051-1">&gt;&gt;</span></code></pre><h2 id="matching-binaries" class="section-heading">
│ │ │ │ +<p>A literal string can be written instead of an element:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2956030220-1">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="2956030220-1">&gt;&gt;</span></code></pre><p>This is syntactic sugar for the following:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3803305498-1">&lt;&lt;</span><span class="sc">$h</span><span class="p">,</span><span class="sc">$e</span><span class="p">,</span><span class="sc">$l</span><span class="p">,</span><span class="sc">$l</span><span class="p">,</span><span class="sc">$o</span><span class="p" data-group-id="3803305498-1">&gt;&gt;</span></code></pre><h2 id="matching-binaries" class="section-heading">
│ │ │ │    <a href="#matching-binaries" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Matching Binaries</span>
│ │ │ │  </h2>
│ │ │ │  <p>This section describes the rules for matching binaries, using the bit syntax.</p><p>There can be zero or more segments in a binary pattern. A binary pattern can
│ │ │ │  occur wherever patterns are allowed, including inside other patterns. Binary
│ │ │ │  patterns cannot be nested. The pattern <code class="inline">&lt;&lt;&gt;&gt;</code> matches a zero length binary.</p><p>Each segment in a binary can consist of zero or more bits. A segment of type
│ │ │ │  <code class="inline">binary</code> must have a size evenly divisible by 8 (or divisible by the unit size,
│ │ │ │  if the unit size has been changed). A segment of type <code class="inline">bitstring</code> has no
│ │ │ │  restrictions on the size. A segment of type <code class="inline">float</code> must have size 64 or 32.</p><p>As mentioned earlier, segments have the following general syntax:</p><p><code class="inline">Value:Size/TypeSpecifierList</code></p><p>When matching <code class="inline">Value</code>, <code class="inline">Value</code> must be either a variable or an integer, or a
│ │ │ │  floating point literal. Expressions are not allowed.</p><p><code class="inline">Size</code> must be a
│ │ │ │  <a href="../../../lib/../system/doc/html/expressions.xhtml#guard-expressions">guard expression</a>, which can use
│ │ │ │ -literals and previously bound variables. The following is not allowed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="5617918052-1">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5617918052-2">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">N</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5617918052-2">&gt;&gt;</span><span class="p" data-group-id="5617918052-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="5617918052-3">{</span><span class="n">X</span><span class="p">,</span><span class="n">T</span><span class="p" data-group-id="5617918052-3">}</span><span class="p">.</span></code></pre><p>The two occurrences of <code class="inline">N</code> are not related. The compiler will complain that the
│ │ │ │ -<code class="inline">N</code> in the size field is unbound.</p><p>The correct way to write this example is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="5201214083-1">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Bin</span><span class="p" data-group-id="5201214083-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="5201214083-2">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">N</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5201214083-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="5201214083-3">{</span><span class="n">X</span><span class="p">,</span><span class="n">T</span><span class="p" data-group-id="5201214083-3">}</span><span class="p">.</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Before OTP 23, <code class="inline">Size</code> was restricted to be an integer or a variable bound to
│ │ │ │ +literals and previously bound variables. The following is not allowed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="2978200048-1">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2978200048-2">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">N</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2978200048-2">&gt;&gt;</span><span class="p" data-group-id="2978200048-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="2978200048-3">{</span><span class="n">X</span><span class="p">,</span><span class="n">T</span><span class="p" data-group-id="2978200048-3">}</span><span class="p">.</span></code></pre><p>The two occurrences of <code class="inline">N</code> are not related. The compiler will complain that the
│ │ │ │ +<code class="inline">N</code> in the size field is unbound.</p><p>The correct way to write this example is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="7039845406-1">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Bin</span><span class="p" data-group-id="7039845406-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="7039845406-2">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">N</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7039845406-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="7039845406-3">{</span><span class="n">X</span><span class="p">,</span><span class="n">T</span><span class="p" data-group-id="7039845406-3">}</span><span class="p">.</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Before OTP 23, <code class="inline">Size</code> was restricted to be an integer or a variable bound to
│ │ │ │  an integer.</p></section><h3 id="binding-and-using-a-size-variable" class="section-heading">
│ │ │ │    <a href="#binding-and-using-a-size-variable" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Binding and Using a Size Variable</span>
│ │ │ │  </h3>
│ │ │ │  <p>There is one exception to the rule that a variable that is used as size must be
│ │ │ │  previously bound. It is possible to match and bind a variable, and use it as a
│ │ │ │ -size within the same binary pattern. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="5876904675-1">(</span><span class="p" data-group-id="5876904675-2">&lt;&lt;</span><span class="n">Sz</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Payload</span><span class="p">:</span><span class="n">Sz</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5876904675-2">&gt;&gt;</span><span class="p" data-group-id="5876904675-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="5876904675-3">{</span><span class="n">Payload</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="5876904675-3">}</span><span class="p">.</span></code></pre><p>Here <code class="inline">Sz</code> is bound to the value in the first byte of the binary. <code class="inline">Sz</code> is then
│ │ │ │ -used as the number of bytes to match out as a binary.</p><p>Starting in OTP 23, the size can be a guard expression:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="2912784432-1">(</span><span class="p" data-group-id="2912784432-2">&lt;&lt;</span><span class="n">Sz</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Payload</span><span class="p">:</span><span class="p" data-group-id="2912784432-3">(</span><span class="p" data-group-id="2912784432-4">(</span><span class="n">Sz</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="2912784432-4">)</span><span class="o">*</span><span class="mi">8</span><span class="p" data-group-id="2912784432-3">)</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2912784432-2">&gt;&gt;</span><span class="p" data-group-id="2912784432-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="2912784432-5">{</span><span class="n">Payload</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="2912784432-5">}</span><span class="p">.</span></code></pre><p>Here <code class="inline">Sz</code> is the combined size of the header and the payload, so we will need to
│ │ │ │ +size within the same binary pattern. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="1936662387-1">(</span><span class="p" data-group-id="1936662387-2">&lt;&lt;</span><span class="n">Sz</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Payload</span><span class="p">:</span><span class="n">Sz</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1936662387-2">&gt;&gt;</span><span class="p" data-group-id="1936662387-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="1936662387-3">{</span><span class="n">Payload</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="1936662387-3">}</span><span class="p">.</span></code></pre><p>Here <code class="inline">Sz</code> is bound to the value in the first byte of the binary. <code class="inline">Sz</code> is then
│ │ │ │ +used as the number of bytes to match out as a binary.</p><p>Starting in OTP 23, the size can be a guard expression:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="7451178300-1">(</span><span class="p" data-group-id="7451178300-2">&lt;&lt;</span><span class="n">Sz</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Payload</span><span class="p">:</span><span class="p" data-group-id="7451178300-3">(</span><span class="p" data-group-id="7451178300-4">(</span><span class="n">Sz</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="7451178300-4">)</span><span class="o">*</span><span class="mi">8</span><span class="p" data-group-id="7451178300-3">)</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7451178300-2">&gt;&gt;</span><span class="p" data-group-id="7451178300-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="7451178300-5">{</span><span class="n">Payload</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="7451178300-5">}</span><span class="p">.</span></code></pre><p>Here <code class="inline">Sz</code> is the combined size of the header and the payload, so we will need to
│ │ │ │  subtract one byte to get the size of the payload.</p><h3 id="getting-the-rest-of-the-binary-or-bitstring" class="section-heading">
│ │ │ │    <a href="#getting-the-rest-of-the-binary-or-bitstring" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Getting the Rest of the Binary or Bitstring</span>
│ │ │ │  </h3>
│ │ │ │ -<p>To match out the rest of a binary, specify a binary field without size:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="8081920254-1">(</span><span class="p" data-group-id="8081920254-2">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8081920254-2">&gt;&gt;</span><span class="p" data-group-id="8081920254-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>The size of the tail must be evenly divisible by 8.</p><p>To match out the rest of a bitstring, specify a field without size:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="7348199378-1">(</span><span class="p" data-group-id="7348199378-2">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="7348199378-2">&gt;&gt;</span><span class="p" data-group-id="7348199378-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>There are no restrictions on the number of bits in the tail.</p><h2 id="appending-to-a-binary" class="section-heading">
│ │ │ │ +<p>To match out the rest of a binary, specify a binary field without size:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="4403924405-1">(</span><span class="p" data-group-id="4403924405-2">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4403924405-2">&gt;&gt;</span><span class="p" data-group-id="4403924405-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>The size of the tail must be evenly divisible by 8.</p><p>To match out the rest of a bitstring, specify a field without size:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="0684758803-1">(</span><span class="p" data-group-id="0684758803-2">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="0684758803-2">&gt;&gt;</span><span class="p" data-group-id="0684758803-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>There are no restrictions on the number of bits in the tail.</p><h2 id="appending-to-a-binary" class="section-heading">
│ │ │ │    <a href="#appending-to-a-binary" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Appending to a Binary</span>
│ │ │ │  </h2>
│ │ │ │ -<p>Appending to a binary in an efficient way can be done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">triples_to_bin</span><span class="p" data-group-id="3914103869-1">(</span><span class="n">T</span><span class="p" data-group-id="3914103869-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">triples_to_bin</span><span class="p" data-group-id="3914103869-2">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3914103869-3">&lt;&lt;</span><span class="p" data-group-id="3914103869-3">&gt;&gt;</span><span class="p" data-group-id="3914103869-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>Appending to a binary in an efficient way can be done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">triples_to_bin</span><span class="p" data-group-id="1274832023-1">(</span><span class="n">T</span><span class="p" data-group-id="1274832023-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">triples_to_bin</span><span class="p" data-group-id="1274832023-2">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1274832023-3">&lt;&lt;</span><span class="p" data-group-id="1274832023-3">&gt;&gt;</span><span class="p" data-group-id="1274832023-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">triples_to_bin</span><span class="p" data-group-id="3914103869-4">(</span><span class="p" data-group-id="3914103869-5">[</span><span class="p" data-group-id="3914103869-6">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="n">Z</span><span class="p" data-group-id="3914103869-6">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="3914103869-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3914103869-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">triples_to_bin</span><span class="p" data-group-id="3914103869-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3914103869-8">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">X</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="n">Y</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="n">Z</span><span class="p">:</span><span class="mi">32</span><span class="p" data-group-id="3914103869-8">&gt;&gt;</span><span class="p" data-group-id="3914103869-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">triples_to_bin</span><span class="p" data-group-id="3914103869-9">(</span><span class="p" data-group-id="3914103869-10">[</span><span class="p" data-group-id="3914103869-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3914103869-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">triples_to_bin</span><span class="p" data-group-id="1274832023-4">(</span><span class="p" data-group-id="1274832023-5">[</span><span class="p" data-group-id="1274832023-6">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="n">Z</span><span class="p" data-group-id="1274832023-6">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="1274832023-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="1274832023-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">triples_to_bin</span><span class="p" data-group-id="1274832023-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1274832023-8">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">X</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="n">Y</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="n">Z</span><span class="p">:</span><span class="mi">32</span><span class="p" data-group-id="1274832023-8">&gt;&gt;</span><span class="p" data-group-id="1274832023-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">triples_to_bin</span><span class="p" data-group-id="1274832023-9">(</span><span class="p" data-group-id="1274832023-10">[</span><span class="p" data-group-id="1274832023-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="1274832023-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/binaryhandling.xhtml
│ │ │ │ @@ -19,43 +19,43 @@
│ │ │ │  
│ │ │ │      <h1 id="content">
│ │ │ │  Constructing and Matching Binaries
│ │ │ │      </h1>
│ │ │ │  <p>This section gives a few examples on how to handle binaries in an efficient way.
│ │ │ │  The sections that follow take an in-depth look at how binaries are implemented
│ │ │ │  and how to best take advantage of the optimizations done by the compiler and
│ │ │ │ -runtime system.</p><p>Binaries can be efficiently <em>built</em> in the following way:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_list_to_binary</span><span class="p" data-group-id="6496106646-1">(</span><span class="n">List</span><span class="p" data-group-id="6496106646-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="6496106646-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6496106646-3">&lt;&lt;</span><span class="p" data-group-id="6496106646-3">&gt;&gt;</span><span class="p" data-group-id="6496106646-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +runtime system.</p><p>Binaries can be efficiently <em>built</em> in the following way:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_list_to_binary</span><span class="p" data-group-id="4780740918-1">(</span><span class="n">List</span><span class="p" data-group-id="4780740918-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="4780740918-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4780740918-3">&lt;&lt;</span><span class="p" data-group-id="4780740918-3">&gt;&gt;</span><span class="p" data-group-id="4780740918-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="6496106646-4">(</span><span class="p" data-group-id="6496106646-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6496106646-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6496106646-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="6496106646-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6496106646-7">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="6496106646-7">&gt;&gt;</span><span class="p" data-group-id="6496106646-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="6496106646-8">(</span><span class="p" data-group-id="6496106646-9">[</span><span class="p" data-group-id="6496106646-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6496106646-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="4780740918-4">(</span><span class="p" data-group-id="4780740918-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4780740918-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="4780740918-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="4780740918-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4780740918-7">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="4780740918-7">&gt;&gt;</span><span class="p" data-group-id="4780740918-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="4780740918-8">(</span><span class="p" data-group-id="4780740918-9">[</span><span class="p" data-group-id="4780740918-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="4780740918-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>Appending data to a binary as in the example is efficient because it is
│ │ │ │  specially optimized by the runtime system to avoid copying the <code class="inline">Acc</code> binary
│ │ │ │ -every time.</p><p>Prepending data to a binary in a loop is not efficient:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="3370689196-1">(</span><span class="n">List</span><span class="p" data-group-id="3370689196-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="3370689196-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3370689196-3">&lt;&lt;</span><span class="p" data-group-id="3370689196-3">&gt;&gt;</span><span class="p" data-group-id="3370689196-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +every time.</p><p>Prepending data to a binary in a loop is not efficient:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9381661310-1">(</span><span class="n">List</span><span class="p" data-group-id="9381661310-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9381661310-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9381661310-3">&lt;&lt;</span><span class="p" data-group-id="9381661310-3">&gt;&gt;</span><span class="p" data-group-id="9381661310-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="3370689196-4">(</span><span class="p" data-group-id="3370689196-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3370689196-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3370689196-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="3370689196-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3370689196-7">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3370689196-7">&gt;&gt;</span><span class="p" data-group-id="3370689196-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="3370689196-8">(</span><span class="p" data-group-id="3370689196-9">[</span><span class="p" data-group-id="3370689196-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3370689196-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9381661310-4">(</span><span class="p" data-group-id="9381661310-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9381661310-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="9381661310-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9381661310-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9381661310-7">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="9381661310-7">&gt;&gt;</span><span class="p" data-group-id="9381661310-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9381661310-8">(</span><span class="p" data-group-id="9381661310-9">[</span><span class="p" data-group-id="9381661310-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="9381661310-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>This is not efficient for long lists because the <code class="inline">Acc</code> binary is copied every
│ │ │ │ -time. One way to make the function more efficient is like this:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="6600196547-1">(</span><span class="n">List</span><span class="p" data-group-id="6600196547-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="6600196547-2">(</span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="6600196547-3">(</span><span class="n">List</span><span class="p" data-group-id="6600196547-3">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6600196547-4">&lt;&lt;</span><span class="p" data-group-id="6600196547-4">&gt;&gt;</span><span class="p" data-group-id="6600196547-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +time. One way to make the function more efficient is like this:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="6713184862-1">(</span><span class="n">List</span><span class="p" data-group-id="6713184862-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="6713184862-2">(</span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="6713184862-3">(</span><span class="n">List</span><span class="p" data-group-id="6713184862-3">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6713184862-4">&lt;&lt;</span><span class="p" data-group-id="6713184862-4">&gt;&gt;</span><span class="p" data-group-id="6713184862-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="6600196547-5">(</span><span class="p" data-group-id="6600196547-6">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6600196547-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6600196547-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="6600196547-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6600196547-8">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="6600196547-8">&gt;&gt;</span><span class="p" data-group-id="6600196547-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="6600196547-9">(</span><span class="p" data-group-id="6600196547-10">[</span><span class="p" data-group-id="6600196547-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6600196547-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>Another way to avoid copying the binary each time is like this:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8067066766-1">(</span><span class="p" data-group-id="8067066766-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8067066766-2">]</span><span class="p" data-group-id="8067066766-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">RevTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8067066766-3">(</span><span class="n">T</span><span class="p" data-group-id="8067066766-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8067066766-4">&lt;&lt;</span><span class="n">RevTail</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="8067066766-4">&gt;&gt;</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8067066766-5">(</span><span class="p" data-group-id="8067066766-6">[</span><span class="p" data-group-id="8067066766-6">]</span><span class="p" data-group-id="8067066766-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8067066766-7">&lt;&lt;</span><span class="p" data-group-id="8067066766-7">&gt;&gt;</span><span class="p">.</span></code></pre><p>Note that in each of the <strong>DO</strong> examples, the binary to be appended to is always
│ │ │ │ -given as the first segment.</p><p>Binaries can be efficiently <em>matched</em> in the following way:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_binary_to_list</span><span class="p" data-group-id="8830047269-1">(</span><span class="p" data-group-id="8830047269-2">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8830047269-2">&gt;&gt;</span><span class="p" data-group-id="8830047269-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8830047269-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="8830047269-4">(</span><span class="n">T</span><span class="p" data-group-id="8830047269-4">)</span><span class="p" data-group-id="8830047269-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="8830047269-5">(</span><span class="p" data-group-id="8830047269-6">&lt;&lt;</span><span class="p" data-group-id="8830047269-6">&gt;&gt;</span><span class="p" data-group-id="8830047269-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8830047269-7">[</span><span class="p" data-group-id="8830047269-7">]</span><span class="p">.</span></code></pre><h2 id="how-binaries-are-implemented" class="section-heading">
│ │ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="6713184862-5">(</span><span class="p" data-group-id="6713184862-6">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6713184862-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6713184862-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="6713184862-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6713184862-8">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="6713184862-8">&gt;&gt;</span><span class="p" data-group-id="6713184862-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="6713184862-9">(</span><span class="p" data-group-id="6713184862-10">[</span><span class="p" data-group-id="6713184862-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6713184862-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>Another way to avoid copying the binary each time is like this:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8740944234-1">(</span><span class="p" data-group-id="8740944234-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8740944234-2">]</span><span class="p" data-group-id="8740944234-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">RevTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8740944234-3">(</span><span class="n">T</span><span class="p" data-group-id="8740944234-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8740944234-4">&lt;&lt;</span><span class="n">RevTail</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="8740944234-4">&gt;&gt;</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8740944234-5">(</span><span class="p" data-group-id="8740944234-6">[</span><span class="p" data-group-id="8740944234-6">]</span><span class="p" data-group-id="8740944234-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8740944234-7">&lt;&lt;</span><span class="p" data-group-id="8740944234-7">&gt;&gt;</span><span class="p">.</span></code></pre><p>Note that in each of the <strong>DO</strong> examples, the binary to be appended to is always
│ │ │ │ +given as the first segment.</p><p>Binaries can be efficiently <em>matched</em> in the following way:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_binary_to_list</span><span class="p" data-group-id="1343891910-1">(</span><span class="p" data-group-id="1343891910-2">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1343891910-2">&gt;&gt;</span><span class="p" data-group-id="1343891910-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1343891910-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="1343891910-4">(</span><span class="n">T</span><span class="p" data-group-id="1343891910-4">)</span><span class="p" data-group-id="1343891910-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="1343891910-5">(</span><span class="p" data-group-id="1343891910-6">&lt;&lt;</span><span class="p" data-group-id="1343891910-6">&gt;&gt;</span><span class="p" data-group-id="1343891910-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1343891910-7">[</span><span class="p" data-group-id="1343891910-7">]</span><span class="p">.</span></code></pre><h2 id="how-binaries-are-implemented" class="section-heading">
│ │ │ │    <a href="#how-binaries-are-implemented" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">How Binaries are Implemented</span>
│ │ │ │  </h2>
│ │ │ │  <p>Internally, binaries and bitstrings are implemented in the same way. In this
│ │ │ │  section, they are called <em>binaries</em> because that is what they are called in the
│ │ │ │ @@ -110,29 +110,29 @@
│ │ │ │  called referential transparency) of Erlang would break.</p><h2 id="constructing-binaries" class="section-heading">
│ │ │ │    <a href="#constructing-binaries" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Constructing Binaries</span>
│ │ │ │  </h2>
│ │ │ │  <p>Appending to a binary or bitstring in the following way is specially optimized
│ │ │ │ -to avoid copying the binary:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6370746667-1">&lt;&lt;</span><span class="n">Binary</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6370746667-1">&gt;&gt;</span><span class="w">
│ │ │ │ +to avoid copying the binary:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8469193859-1">&lt;&lt;</span><span class="n">Binary</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8469193859-1">&gt;&gt;</span><span class="w">
│ │ │ │  </span><span class="c1">%% - OR -</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6370746667-2">&lt;&lt;</span><span class="n">Binary</span><span class="o">/</span><span class="ss">bitstring</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6370746667-2">&gt;&gt;</span></code></pre><p>This optimization is applied by the runtime system in a way that makes it
│ │ │ │ +</span><span class="p" data-group-id="8469193859-2">&lt;&lt;</span><span class="n">Binary</span><span class="o">/</span><span class="ss">bitstring</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8469193859-2">&gt;&gt;</span></code></pre><p>This optimization is applied by the runtime system in a way that makes it
│ │ │ │  effective in most circumstances (for exceptions, see
│ │ │ │  <a href="binaryhandling.xhtml#forced_copying">Circumstances That Force Copying</a>). The
│ │ │ │  optimization in its basic form does not need any help from the compiler.
│ │ │ │  However, the compiler adds hints to the runtime system when it is safe to apply
│ │ │ │  the optimization in a more efficient way.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>The compiler support for making the optimization more efficient was added in
│ │ │ │  Erlang/OTP 26.</p></section><p>To explain how the basic optimization works, let us examine the following code
│ │ │ │ -line by line:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3585158972-1">&lt;&lt;</span><span class="mi">0</span><span class="p" data-group-id="3585158972-1">&gt;&gt;</span><span class="p">,</span><span class="w">                    </span><span class="c1">%% 1</span><span class="w">
│ │ │ │ -</span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3585158972-2">&lt;&lt;</span><span class="n">Bin0</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3585158972-2">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 2</span><span class="w">
│ │ │ │ -</span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3585158972-3">&lt;&lt;</span><span class="n">Bin1</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3585158972-3">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 3</span><span class="w">
│ │ │ │ -</span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3585158972-4">&lt;&lt;</span><span class="n">Bin2</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p" data-group-id="3585158972-4">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 4</span><span class="w">
│ │ │ │ -</span><span class="n">Bin4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3585158972-5">&lt;&lt;</span><span class="n">Bin1</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="3585158972-5">&gt;&gt;</span><span class="p">,</span><span class="w">       </span><span class="c1">%% 5 !!!</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3585158972-6">{</span><span class="n">Bin4</span><span class="p">,</span><span class="n">Bin3</span><span class="p" data-group-id="3585158972-6">}</span><span class="w">                      </span><span class="c1">%% 6</span></code></pre><ul><li><p>Line 1 (marked with the <code class="inline">%% 1</code> comment), assigns a
│ │ │ │ +line by line:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3126776590-1">&lt;&lt;</span><span class="mi">0</span><span class="p" data-group-id="3126776590-1">&gt;&gt;</span><span class="p">,</span><span class="w">                    </span><span class="c1">%% 1</span><span class="w">
│ │ │ │ +</span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3126776590-2">&lt;&lt;</span><span class="n">Bin0</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3126776590-2">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 2</span><span class="w">
│ │ │ │ +</span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3126776590-3">&lt;&lt;</span><span class="n">Bin1</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3126776590-3">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 3</span><span class="w">
│ │ │ │ +</span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3126776590-4">&lt;&lt;</span><span class="n">Bin2</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p" data-group-id="3126776590-4">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 4</span><span class="w">
│ │ │ │ +</span><span class="n">Bin4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3126776590-5">&lt;&lt;</span><span class="n">Bin1</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="3126776590-5">&gt;&gt;</span><span class="p">,</span><span class="w">       </span><span class="c1">%% 5 !!!</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3126776590-6">{</span><span class="n">Bin4</span><span class="p">,</span><span class="n">Bin3</span><span class="p" data-group-id="3126776590-6">}</span><span class="w">                      </span><span class="c1">%% 6</span></code></pre><ul><li><p>Line 1 (marked with the <code class="inline">%% 1</code> comment), assigns a
│ │ │ │  <a href="binaryhandling.xhtml#heap_binary">heap binary</a> to the <code class="inline">Bin0</code> variable.</p></li><li><p>Line 2 is an append operation. As <code class="inline">Bin0</code> has not been involved in an append
│ │ │ │  operation, a new <a href="binaryhandling.xhtml#refc_binary">refc binary</a> is created and
│ │ │ │  the contents of <code class="inline">Bin0</code> is copied into it. The <em>ProcBin</em> part of the refc
│ │ │ │  binary has its size set to the size of the data stored in the binary, while
│ │ │ │  the binary object has extra space allocated. The size of the binary object is
│ │ │ │  either twice the size of <code class="inline">Bin1</code> or 256, whichever is larger. In this case it
│ │ │ │  is 256.</p></li><li><p>Line 3 is more interesting. <code class="inline">Bin1</code> <em>has</em> been used in an append operation, and
│ │ │ │ @@ -158,23 +158,23 @@
│ │ │ │  handle an append operation to a heap binary by copying it to a refc binary (line
│ │ │ │  2), and also handle an append operation to a previous version of the binary by
│ │ │ │  copying it (line 5). The support for doing that does not come for free. For
│ │ │ │  example, to make it possible to know when it is necessary to copy the binary,
│ │ │ │  for every append operation, the runtime system must create a sub binary.</p><p>When the compiler can determine that none of those situations need to be handled
│ │ │ │  and that the append operation cannot possibly fail, the compiler generates code
│ │ │ │  that causes the runtime system to apply a more efficient variant of the
│ │ │ │ -optimization.</p><p><strong>Example:</strong></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8006087468-1">(</span><span class="ss">repack</span><span class="p" data-group-id="8006087468-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8006087468-2">(</span><span class="p" data-group-id="8006087468-3">[</span><span class="ss">repack</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8006087468-3">]</span><span class="p" data-group-id="8006087468-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +optimization.</p><p><strong>Example:</strong></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7932043522-1">(</span><span class="ss">repack</span><span class="p" data-group-id="7932043522-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7932043522-2">(</span><span class="p" data-group-id="7932043522-3">[</span><span class="ss">repack</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7932043522-3">]</span><span class="p" data-group-id="7932043522-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">repack</span><span class="p" data-group-id="8006087468-4">(</span><span class="n">Bin</span><span class="p" data-group-id="8006087468-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_binary</span><span class="p" data-group-id="8006087468-5">(</span><span class="n">Bin</span><span class="p" data-group-id="8006087468-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">repack</span><span class="p" data-group-id="8006087468-6">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8006087468-7">&lt;&lt;</span><span class="p" data-group-id="8006087468-7">&gt;&gt;</span><span class="p" data-group-id="8006087468-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">repack</span><span class="p" data-group-id="7932043522-4">(</span><span class="n">Bin</span><span class="p" data-group-id="7932043522-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_binary</span><span class="p" data-group-id="7932043522-5">(</span><span class="n">Bin</span><span class="p" data-group-id="7932043522-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">repack</span><span class="p" data-group-id="7932043522-6">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7932043522-7">&lt;&lt;</span><span class="p" data-group-id="7932043522-7">&gt;&gt;</span><span class="p" data-group-id="7932043522-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">repack</span><span class="p" data-group-id="8006087468-8">(</span><span class="p" data-group-id="8006087468-9">&lt;&lt;</span><span class="n">C</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8006087468-9">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="8006087468-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">repack</span><span class="p" data-group-id="8006087468-10">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8006087468-11">&lt;&lt;</span><span class="n">Result</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="8006087468-11">&gt;&gt;</span><span class="p" data-group-id="8006087468-10">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">repack</span><span class="p" data-group-id="8006087468-12">(</span><span class="p" data-group-id="8006087468-13">&lt;&lt;</span><span class="p" data-group-id="8006087468-13">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="8006087468-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">repack</span><span class="p" data-group-id="7932043522-8">(</span><span class="p" data-group-id="7932043522-9">&lt;&lt;</span><span class="n">C</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7932043522-9">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7932043522-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">repack</span><span class="p" data-group-id="7932043522-10">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7932043522-11">&lt;&lt;</span><span class="n">Result</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="7932043522-11">&gt;&gt;</span><span class="p" data-group-id="7932043522-10">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">repack</span><span class="p" data-group-id="7932043522-12">(</span><span class="p" data-group-id="7932043522-13">&lt;&lt;</span><span class="p" data-group-id="7932043522-13">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7932043522-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Result</span><span class="p">.</span></code></pre><p>The <code class="inline">repack/2</code> function only keeps a single version of the binary, so there is
│ │ │ │  never any need to copy the binary. The compiler rewrites the creation of the
│ │ │ │  empty binary in <code class="inline">repack/1</code> to instead create a refc binary with 256 bytes
│ │ │ │  already reserved; thus, the append operation in <code class="inline">repack/2</code> never needs to handle
│ │ │ │  a binary not prepared for appending.</p><p><a href="" id="forced_copying"></a></p><h3 id="circumstances-that-force-copying" class="section-heading">
│ │ │ │    <a href="#circumstances-that-force-copying" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │ @@ -186,72 +186,72 @@
│ │ │ │  reason is that the binary object can be moved (reallocated) during an append
│ │ │ │  operation, and when that happens, the pointer in the ProcBin must be updated. If
│ │ │ │  there would be more than one ProcBin pointing to the binary object, it would not
│ │ │ │  be possible to find and update all of them.</p><p>Therefore, certain operations on a binary mark it so that any future append
│ │ │ │  operation will be forced to copy the binary. In most cases, the binary object
│ │ │ │  will be shrunk at the same time to reclaim the extra space allocated for
│ │ │ │  growing.</p><p>When appending to a binary as follows, only the binary returned from the latest
│ │ │ │ -append operation will support further cheap append operations:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0260479596-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0260479596-1">&gt;&gt;</span></code></pre><p>In the code fragment in the beginning of this section, appending to <code class="inline">Bin</code> will
│ │ │ │ +append operation will support further cheap append operations:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6178139595-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6178139595-1">&gt;&gt;</span></code></pre><p>In the code fragment in the beginning of this section, appending to <code class="inline">Bin</code> will
│ │ │ │  be cheap, while appending to <code class="inline">Bin0</code> will force the creation of a new binary and
│ │ │ │  copying of the contents of <code class="inline">Bin0</code>.</p><p>If a binary is sent as a message to a process or port, the binary will be shrunk
│ │ │ │  and any further append operation will copy the binary data into a new binary.
│ │ │ │  For example, in the following code fragment <code class="inline">Bin1</code> will be copied in the third
│ │ │ │ -line:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0170533901-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0170533901-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ +line:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0929280801-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0929280801-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="n">PortOrPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Bin1</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0170533901-2">&lt;&lt;</span><span class="n">Bin1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0170533901-2">&gt;&gt;</span><span class="w">  </span><span class="c1">%% Bin1 will be COPIED</span></code></pre><p>The same happens if you insert a binary into an Ets table, send it to a port
│ │ │ │ +</span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0929280801-2">&lt;&lt;</span><span class="n">Bin1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0929280801-2">&gt;&gt;</span><span class="w">  </span><span class="c1">%% Bin1 will be COPIED</span></code></pre><p>The same happens if you insert a binary into an Ets table, send it to a port
│ │ │ │  using <a href="../../../lib/../erts/doc/html/erlang.html#port_command/2"><code class="inline">erlang:port_command/2</code></a>, or pass it to
│ │ │ │  <a href="../../../lib/../erts/doc/html/erl_nif.xhtml#enif_inspect_binary">enif_inspect_binary</a> in a NIF.</p><p>Matching a binary will also cause it to shrink and the next append operation
│ │ │ │ -will copy the binary data:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2089028537-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2089028537-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2089028537-2">&lt;&lt;</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="n">Z</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2089028537-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin1</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2089028537-3">&lt;&lt;</span><span class="n">Bin1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2089028537-3">&gt;&gt;</span><span class="w">  </span><span class="c1">%% Bin1 will be COPIED</span></code></pre><p>The reason is that a <a href="binaryhandling.xhtml#match_context">match context</a> contains a
│ │ │ │ +will copy the binary data:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7541807651-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7541807651-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7541807651-2">&lt;&lt;</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="n">Z</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7541807651-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin1</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7541807651-3">&lt;&lt;</span><span class="n">Bin1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7541807651-3">&gt;&gt;</span><span class="w">  </span><span class="c1">%% Bin1 will be COPIED</span></code></pre><p>The reason is that a <a href="binaryhandling.xhtml#match_context">match context</a> contains a
│ │ │ │  direct pointer to the binary data.</p><p>If a process simply keeps binaries (either in &quot;loop data&quot; or in the process
│ │ │ │  dictionary), the garbage collector can eventually shrink the binaries. If only
│ │ │ │  one such binary is kept, it will not be shrunk. If the process later appends to
│ │ │ │  a binary that has been shrunk, the binary object will be reallocated to make
│ │ │ │  place for the data to be appended.</p><h2 id="matching-binaries" class="section-heading">
│ │ │ │    <a href="#matching-binaries" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Matching Binaries</span>
│ │ │ │  </h2>
│ │ │ │ -<p>Let us revisit the example in the beginning of the previous section:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_binary_to_list</span><span class="p" data-group-id="8325361846-1">(</span><span class="p" data-group-id="8325361846-2">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8325361846-2">&gt;&gt;</span><span class="p" data-group-id="8325361846-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8325361846-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="8325361846-4">(</span><span class="n">T</span><span class="p" data-group-id="8325361846-4">)</span><span class="p" data-group-id="8325361846-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="8325361846-5">(</span><span class="p" data-group-id="8325361846-6">&lt;&lt;</span><span class="p" data-group-id="8325361846-6">&gt;&gt;</span><span class="p" data-group-id="8325361846-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8325361846-7">[</span><span class="p" data-group-id="8325361846-7">]</span><span class="p">.</span></code></pre><p>The first time <code class="inline">my_binary_to_list/1</code> is called, a
│ │ │ │ +<p>Let us revisit the example in the beginning of the previous section:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_binary_to_list</span><span class="p" data-group-id="3529944157-1">(</span><span class="p" data-group-id="3529944157-2">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3529944157-2">&gt;&gt;</span><span class="p" data-group-id="3529944157-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3529944157-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="3529944157-4">(</span><span class="n">T</span><span class="p" data-group-id="3529944157-4">)</span><span class="p" data-group-id="3529944157-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="3529944157-5">(</span><span class="p" data-group-id="3529944157-6">&lt;&lt;</span><span class="p" data-group-id="3529944157-6">&gt;&gt;</span><span class="p" data-group-id="3529944157-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3529944157-7">[</span><span class="p" data-group-id="3529944157-7">]</span><span class="p">.</span></code></pre><p>The first time <code class="inline">my_binary_to_list/1</code> is called, a
│ │ │ │  <a href="binaryhandling.xhtml#match_context">match context</a> is created. The match context
│ │ │ │  points to the first byte of the binary. 1 byte is matched out and the match
│ │ │ │  context is updated to point to the second byte in the binary.</p><p>At this point it would make sense to create a
│ │ │ │  <a href="binaryhandling.xhtml#sub_binary">sub binary</a>, but in this particular example the
│ │ │ │  compiler sees that there will soon be a call to a function (in this case, to
│ │ │ │  <code class="inline">my_binary_to_list/1</code> itself) that immediately will create a new match context
│ │ │ │  and discard the sub binary.</p><p>Therefore <code class="inline">my_binary_to_list/1</code> calls itself with the match context instead of
│ │ │ │  with a sub binary. The instruction that initializes the matching operation
│ │ │ │  basically does nothing when it sees that it was passed a match context instead
│ │ │ │  of a binary.</p><p>When the end of the binary is reached and the second clause matches, the match
│ │ │ │  context will simply be discarded (removed in the next garbage collection, as
│ │ │ │  there is no longer any reference to it).</p><p>To summarize, <code class="inline">my_binary_to_list/1</code> only needs to create <em>one</em> match context and
│ │ │ │  no sub binaries.</p><p>Notice that the match context in <code class="inline">my_binary_to_list/1</code> was discarded when the
│ │ │ │  entire binary had been traversed. What happens if the iteration stops before it
│ │ │ │ -has reached the end of the binary? Will the optimization still work?</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="0215577553-1">(</span><span class="p" data-group-id="0215577553-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0215577553-2">&gt;&gt;</span><span class="p" data-group-id="0215577553-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +has reached the end of the binary? Will the optimization still work?</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="7140806481-1">(</span><span class="p" data-group-id="7140806481-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7140806481-2">&gt;&gt;</span><span class="p" data-group-id="7140806481-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">T</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="0215577553-3">(</span><span class="p" data-group-id="0215577553-4">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0215577553-4">&gt;&gt;</span><span class="p" data-group-id="0215577553-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">after_zero</span><span class="p" data-group-id="0215577553-5">(</span><span class="n">T</span><span class="p" data-group-id="0215577553-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="0215577553-6">(</span><span class="p" data-group-id="0215577553-7">&lt;&lt;</span><span class="p" data-group-id="0215577553-7">&gt;&gt;</span><span class="p" data-group-id="0215577553-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0215577553-8">&lt;&lt;</span><span class="p" data-group-id="0215577553-8">&gt;&gt;</span><span class="p">.</span></code></pre><p>Yes, it will. The compiler will remove the building of the sub binary in the
│ │ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="7140806481-3">(</span><span class="p" data-group-id="7140806481-4">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7140806481-4">&gt;&gt;</span><span class="p" data-group-id="7140806481-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">after_zero</span><span class="p" data-group-id="7140806481-5">(</span><span class="n">T</span><span class="p" data-group-id="7140806481-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="7140806481-6">(</span><span class="p" data-group-id="7140806481-7">&lt;&lt;</span><span class="p" data-group-id="7140806481-7">&gt;&gt;</span><span class="p" data-group-id="7140806481-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7140806481-8">&lt;&lt;</span><span class="p" data-group-id="7140806481-8">&gt;&gt;</span><span class="p">.</span></code></pre><p>Yes, it will. The compiler will remove the building of the sub binary in the
│ │ │ │  second clause:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="4803153666-1">(</span><span class="p" data-group-id="4803153666-2">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4803153666-2">&gt;&gt;</span><span class="p" data-group-id="4803153666-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">after_zero</span><span class="p" data-group-id="4803153666-3">(</span><span class="n">T</span><span class="p" data-group-id="4803153666-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>But it will generate code that builds a sub binary in the first clause:</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="2004435579-1">(</span><span class="p" data-group-id="2004435579-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2004435579-2">&gt;&gt;</span><span class="p" data-group-id="2004435579-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="4515653315-1">(</span><span class="p" data-group-id="4515653315-2">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4515653315-2">&gt;&gt;</span><span class="p" data-group-id="4515653315-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">after_zero</span><span class="p" data-group-id="4515653315-3">(</span><span class="n">T</span><span class="p" data-group-id="4515653315-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>But it will generate code that builds a sub binary in the first clause:</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="7533668575-1">(</span><span class="p" data-group-id="7533668575-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7533668575-2">&gt;&gt;</span><span class="p" data-group-id="7533668575-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">T</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Therefore, <code class="inline">after_zero/1</code> builds one match context and one sub binary (assuming
│ │ │ │ -it is passed a binary that contains a zero byte).</p><p>Code like the following will also be optimized:</p><pre><code class="makeup erlang" translate="no"><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="6223010104-1">(</span><span class="n">Buffer</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="6223010104-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6223010104-2">{</span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="6223010104-3">(</span><span class="n">Acc</span><span class="p" data-group-id="6223010104-3">)</span><span class="p">,</span><span class="n">Buffer</span><span class="p" data-group-id="6223010104-2">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="6223010104-4">(</span><span class="p" data-group-id="6223010104-5">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6223010104-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="p" data-group-id="6223010104-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="6223010104-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="6223010104-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="6223010104-7">(</span><span class="p" data-group-id="6223010104-8">&lt;&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6223010104-8">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="p" data-group-id="6223010104-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="6223010104-9">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6223010104-10">[</span><span class="n">Byte</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="6223010104-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="6223010104-9">)</span><span class="p">.</span></code></pre><p>The compiler removes building of sub binaries in the second and third clauses,
│ │ │ │ +it is passed a binary that contains a zero byte).</p><p>Code like the following will also be optimized:</p><pre><code class="makeup erlang" translate="no"><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="3504653091-1">(</span><span class="n">Buffer</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="3504653091-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3504653091-2">{</span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="3504653091-3">(</span><span class="n">Acc</span><span class="p" data-group-id="3504653091-3">)</span><span class="p">,</span><span class="n">Buffer</span><span class="p" data-group-id="3504653091-2">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="3504653091-4">(</span><span class="p" data-group-id="3504653091-5">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3504653091-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="p" data-group-id="3504653091-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="3504653091-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="3504653091-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="3504653091-7">(</span><span class="p" data-group-id="3504653091-8">&lt;&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3504653091-8">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="p" data-group-id="3504653091-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="3504653091-9">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3504653091-10">[</span><span class="n">Byte</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="3504653091-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="3504653091-9">)</span><span class="p">.</span></code></pre><p>The compiler removes building of sub binaries in the second and third clauses,
│ │ │ │  and it adds an instruction to the first clause that converts <code class="inline">Buffer</code> from a
│ │ │ │  match context to a sub binary (or does nothing if <code class="inline">Buffer</code> is already a binary).</p><p>But in more complicated code, how can one know whether the optimization is
│ │ │ │  applied or not?</p><p><a href="" id="bin_opt_info"></a></p><h3 id="option-bin_opt_info" class="section-heading">
│ │ │ │    <a href="#option-bin_opt_info" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Option bin_opt_info</span>
│ │ │ │ @@ -259,35 +259,35 @@
│ │ │ │  <p>Use the <code class="inline">bin_opt_info</code> option to have the compiler print a lot of information
│ │ │ │  about binary optimizations. It can be given either to the compiler or <code class="inline">erlc</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">erlc</span><span class="w"> </span><span class="o">+</span><span class="ss">bin_opt_info</span><span class="w"> </span><span class="n">Mod</span><span class="p">.</span><span class="ss">erl</span></code></pre><p>or passed through an environment variable:</p><pre><code class="makeup erlang" translate="no"><span class="ss">export</span><span class="w"> </span><span class="n">ERL_COMPILER_OPTIONS</span><span class="o">=</span><span class="ss">bin_opt_info</span></code></pre><p>Notice that the <code class="inline">bin_opt_info</code> is not meant to be a permanent option added to
│ │ │ │  your <code class="inline">Makefile</code>s, because all messages that it generates cannot be eliminated.
│ │ │ │  Therefore, passing the option through the environment is in most cases the most
│ │ │ │  practical approach.</p><p>The warnings look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="o">/</span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">60</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">NOT</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">binary</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">returned</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">function</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="o">/</span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">62</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">match</span><span class="w"> </span><span class="ss">context</span><span class="w"> </span><span class="ss">reused</span></code></pre><p>To make it clearer exactly what code the warnings refer to, the warnings in the
│ │ │ │  following examples are inserted as comments after the clause they refer to, for
│ │ │ │ -example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="6681917456-1">(</span><span class="p" data-group-id="6681917456-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6681917456-2">&gt;&gt;</span><span class="p" data-group-id="6681917456-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="0483241417-1">(</span><span class="p" data-group-id="0483241417-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0483241417-2">&gt;&gt;</span><span class="p" data-group-id="0483241417-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │           </span><span class="c1">%% BINARY CREATED: binary is returned from the function</span><span class="w">
│ │ │ │      </span><span class="n">T</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="6681917456-3">(</span><span class="p" data-group-id="6681917456-4">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6681917456-4">&gt;&gt;</span><span class="p" data-group-id="6681917456-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="0483241417-3">(</span><span class="p" data-group-id="0483241417-4">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0483241417-4">&gt;&gt;</span><span class="p" data-group-id="0483241417-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │           </span><span class="c1">%% OPTIMIZED: match context reused</span><span class="w">
│ │ │ │ -    </span><span class="nf">after_zero</span><span class="p" data-group-id="6681917456-5">(</span><span class="n">T</span><span class="p" data-group-id="6681917456-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="6681917456-6">(</span><span class="p" data-group-id="6681917456-7">&lt;&lt;</span><span class="p" data-group-id="6681917456-7">&gt;&gt;</span><span class="p" data-group-id="6681917456-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6681917456-8">&lt;&lt;</span><span class="p" data-group-id="6681917456-8">&gt;&gt;</span><span class="p">.</span></code></pre><p>The warning for the first clause says that the creation of a sub binary cannot
│ │ │ │ +    </span><span class="nf">after_zero</span><span class="p" data-group-id="0483241417-5">(</span><span class="n">T</span><span class="p" data-group-id="0483241417-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="0483241417-6">(</span><span class="p" data-group-id="0483241417-7">&lt;&lt;</span><span class="p" data-group-id="0483241417-7">&gt;&gt;</span><span class="p" data-group-id="0483241417-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0483241417-8">&lt;&lt;</span><span class="p" data-group-id="0483241417-8">&gt;&gt;</span><span class="p">.</span></code></pre><p>The warning for the first clause says that the creation of a sub binary cannot
│ │ │ │  be delayed, because it will be returned. The warning for the second clause says
│ │ │ │  that a sub binary will not be created (yet).</p><h3 id="unused-variables" class="section-heading">
│ │ │ │    <a href="#unused-variables" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Unused Variables</span>
│ │ │ │  </h3>
│ │ │ │  <p>The compiler figures out if a variable is unused. The same code is generated for
│ │ │ │ -each of the following functions:</p><pre><code class="makeup erlang" translate="no"><span class="nf">count1</span><span class="p" data-group-id="8095591907-1">(</span><span class="p" data-group-id="8095591907-2">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8095591907-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="8095591907-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count1</span><span class="p" data-group-id="8095591907-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="8095591907-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">count1</span><span class="p" data-group-id="8095591907-4">(</span><span class="p" data-group-id="8095591907-5">&lt;&lt;</span><span class="p" data-group-id="8095591907-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="8095591907-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span><span class="w">
│ │ │ │ +each of the following functions:</p><pre><code class="makeup erlang" translate="no"><span class="nf">count1</span><span class="p" data-group-id="0104408947-1">(</span><span class="p" data-group-id="0104408947-2">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0104408947-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="0104408947-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count1</span><span class="p" data-group-id="0104408947-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="0104408947-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">count1</span><span class="p" data-group-id="0104408947-4">(</span><span class="p" data-group-id="0104408947-5">&lt;&lt;</span><span class="p" data-group-id="0104408947-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="0104408947-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">count2</span><span class="p" data-group-id="8095591907-6">(</span><span class="p" data-group-id="8095591907-7">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8095591907-7">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="8095591907-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count2</span><span class="p" data-group-id="8095591907-8">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="8095591907-8">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">count2</span><span class="p" data-group-id="8095591907-9">(</span><span class="p" data-group-id="8095591907-10">&lt;&lt;</span><span class="p" data-group-id="8095591907-10">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="8095591907-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">count2</span><span class="p" data-group-id="0104408947-6">(</span><span class="p" data-group-id="0104408947-7">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0104408947-7">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="0104408947-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count2</span><span class="p" data-group-id="0104408947-8">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="0104408947-8">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">count2</span><span class="p" data-group-id="0104408947-9">(</span><span class="p" data-group-id="0104408947-10">&lt;&lt;</span><span class="p" data-group-id="0104408947-10">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="0104408947-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">count3</span><span class="p" data-group-id="8095591907-11">(</span><span class="p" data-group-id="8095591907-12">&lt;&lt;</span><span class="p">_</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8095591907-12">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="8095591907-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count3</span><span class="p" data-group-id="8095591907-13">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="8095591907-13">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">count3</span><span class="p" data-group-id="8095591907-14">(</span><span class="p" data-group-id="8095591907-15">&lt;&lt;</span><span class="p" data-group-id="8095591907-15">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="8095591907-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span></code></pre><p>In each iteration, the first 8 bits in the binary will be skipped, not matched
│ │ │ │ +</span><span class="nf">count3</span><span class="p" data-group-id="0104408947-11">(</span><span class="p" data-group-id="0104408947-12">&lt;&lt;</span><span class="p">_</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0104408947-12">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="0104408947-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count3</span><span class="p" data-group-id="0104408947-13">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="0104408947-13">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">count3</span><span class="p" data-group-id="0104408947-14">(</span><span class="p" data-group-id="0104408947-15">&lt;&lt;</span><span class="p" data-group-id="0104408947-15">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="0104408947-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span></code></pre><p>In each iteration, the first 8 bits in the binary will be skipped, not matched
│ │ │ │  out.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/benchmarking.xhtml
│ │ │ │ @@ -49,16 +49,16 @@
│ │ │ │  fast as possible, what can we do? One way could be to generate more
│ │ │ │  than two bytes at a time.</p><pre><code class="text">% erlperf 'rand:bytes(100).' 'crypto:strong_rand_bytes(100).'
│ │ │ │  Code                                   ||        QPS       Time   Rel
│ │ │ │  rand:bytes(100).                        1    2124 Ki     470 ns  100%
│ │ │ │  crypto:strong_rand_bytes(100).          1    1915 Ki     522 ns   90%</code></pre><p><a href="../../../lib/stdlib/doc/html/rand.html#bytes/1"><code class="inline">rand:bytes/1</code></a> is still faster when we generate 100 bytes at a time,
│ │ │ │  but the relative difference is smaller.</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erlperf &#39;rand:bytes(1000).&#39; &#39;crypto:strong_rand_bytes(1000).&#39;</span><span class="w">
│ │ │ │  </span><span class="n">Code</span><span class="w">                                    </span><span class="p">||</span><span class="w">        </span><span class="n">QPS</span><span class="w">       </span><span class="n">Time</span><span class="w">   </span><span class="n">Rel</span><span class="w">
│ │ │ │ -</span><span class="nc">crypto</span><span class="p">:</span><span class="nf">strong_rand_bytes</span><span class="p" data-group-id="0067696383-1">(</span><span class="mi">1000</span><span class="p" data-group-id="0067696383-1">)</span><span class="p">.</span><span class="w">          </span><span class="mi">1</span><span class="w">    </span><span class="mi">1518</span><span class="w"> </span><span class="n">Ki</span><span class="w">     </span><span class="mi">658</span><span class="w"> </span><span class="ss">ns</span><span class="w">  </span><span class="mi">100</span><span class="c1">%</span><span class="w">
│ │ │ │ -</span><span class="nc">rand</span><span class="p">:</span><span class="nf">bytes</span><span class="p" data-group-id="0067696383-2">(</span><span class="mi">1000</span><span class="p" data-group-id="0067696383-2">)</span><span class="p">.</span><span class="w">                        </span><span class="mi">1</span><span class="w">     </span><span class="mi">284</span><span class="w"> </span><span class="n">Ki</span><span class="w">    </span><span class="mi">3521</span><span class="w"> </span><span class="ss">ns</span><span class="w">   </span><span class="mi">19</span><span class="c1">%</span></code></pre><p>When we generate 1000 bytes at a time, <a href="../../../lib/crypto/doc/html/crypto.html#strong_rand_bytes/1"><code class="inline">crypto:strong_rand_bytes/1</code></a> is
│ │ │ │ +</span><span class="nc">crypto</span><span class="p">:</span><span class="nf">strong_rand_bytes</span><span class="p" data-group-id="5307371020-1">(</span><span class="mi">1000</span><span class="p" data-group-id="5307371020-1">)</span><span class="p">.</span><span class="w">          </span><span class="mi">1</span><span class="w">    </span><span class="mi">1518</span><span class="w"> </span><span class="n">Ki</span><span class="w">     </span><span class="mi">658</span><span class="w"> </span><span class="ss">ns</span><span class="w">  </span><span class="mi">100</span><span class="c1">%</span><span class="w">
│ │ │ │ +</span><span class="nc">rand</span><span class="p">:</span><span class="nf">bytes</span><span class="p" data-group-id="5307371020-2">(</span><span class="mi">1000</span><span class="p" data-group-id="5307371020-2">)</span><span class="p">.</span><span class="w">                        </span><span class="mi">1</span><span class="w">     </span><span class="mi">284</span><span class="w"> </span><span class="n">Ki</span><span class="w">    </span><span class="mi">3521</span><span class="w"> </span><span class="ss">ns</span><span class="w">   </span><span class="mi">19</span><span class="c1">%</span></code></pre><p>When we generate 1000 bytes at a time, <a href="../../../lib/crypto/doc/html/crypto.html#strong_rand_bytes/1"><code class="inline">crypto:strong_rand_bytes/1</code></a> is
│ │ │ │  now the fastest.</p><h2 id="benchmarking-using-erlang-otp-functionality" class="section-heading">
│ │ │ │    <a href="#benchmarking-using-erlang-otp-functionality" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Benchmarking using Erlang/OTP functionality</span>
│ │ │ │  </h2>
│ │ │ │  <p>Benchmarks can measure wall-clock time or CPU time.</p><ul><li><p><a href="../../../lib/stdlib/doc/html/timer.html#tc/3"><code class="inline">timer:tc/3</code></a> measures wall-clock time. The advantage with wall-clock time is
│ │ │ ├── OEBPS/appup_cookbook.xhtml
│ │ │ │ @@ -25,18 +25,18 @@
│ │ │ │    <a href="#changing-a-functional-module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing a Functional Module</span>
│ │ │ │  </h2>
│ │ │ │  <p>When a functional module has been changed, for example, if a new function has
│ │ │ │  been added or a bug has been corrected, simple code replacement is sufficient,
│ │ │ │ -for example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3394176172-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3394176172-2">[</span><span class="p" data-group-id="3394176172-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3394176172-4">[</span><span class="p" data-group-id="3394176172-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="3394176172-5">}</span><span class="p" data-group-id="3394176172-4">]</span><span class="p" data-group-id="3394176172-3">}</span><span class="p" data-group-id="3394176172-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3394176172-6">[</span><span class="p" data-group-id="3394176172-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3394176172-8">[</span><span class="p" data-group-id="3394176172-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="3394176172-9">}</span><span class="p" data-group-id="3394176172-8">]</span><span class="p" data-group-id="3394176172-7">}</span><span class="p" data-group-id="3394176172-6">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3394176172-1">}</span><span class="p">.</span></code></pre><h2 id="changing-a-residence-module" class="section-heading">
│ │ │ │ +for example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1417317265-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="1417317265-2">[</span><span class="p" data-group-id="1417317265-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1417317265-4">[</span><span class="p" data-group-id="1417317265-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="1417317265-5">}</span><span class="p" data-group-id="1417317265-4">]</span><span class="p" data-group-id="1417317265-3">}</span><span class="p" data-group-id="1417317265-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="1417317265-6">[</span><span class="p" data-group-id="1417317265-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1417317265-8">[</span><span class="p" data-group-id="1417317265-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="1417317265-9">}</span><span class="p" data-group-id="1417317265-8">]</span><span class="p" data-group-id="1417317265-7">}</span><span class="p" data-group-id="1417317265-6">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1417317265-1">}</span><span class="p">.</span></code></pre><h2 id="changing-a-residence-module" class="section-heading">
│ │ │ │    <a href="#changing-a-residence-module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing a Residence Module</span>
│ │ │ │  </h2>
│ │ │ │  <p>In a system implemented according to the OTP design principles, all processes,
│ │ │ │  except system processes and special processes, reside in one of the behaviours
│ │ │ │ @@ -47,46 +47,46 @@
│ │ │ │    <a href="#changing-a-callback-module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing a Callback Module</span>
│ │ │ │  </h2>
│ │ │ │  <p>A callback module is a functional module, and for code extensions simple code
│ │ │ │  replacement is sufficient.</p><p><em>Example</em></p><p>When adding a function to <code class="inline">ch3</code>, as described in the example in
│ │ │ │ -<a href="release_handling.xhtml#appup">Release Handling</a>, <code class="inline">ch_app.appup</code> looks as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2905874615-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2905874615-2">[</span><span class="p" data-group-id="2905874615-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2905874615-4">[</span><span class="p" data-group-id="2905874615-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="2905874615-5">}</span><span class="p" data-group-id="2905874615-4">]</span><span class="p" data-group-id="2905874615-3">}</span><span class="p" data-group-id="2905874615-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2905874615-6">[</span><span class="p" data-group-id="2905874615-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2905874615-8">[</span><span class="p" data-group-id="2905874615-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="2905874615-9">}</span><span class="p" data-group-id="2905874615-8">]</span><span class="p" data-group-id="2905874615-7">}</span><span class="p" data-group-id="2905874615-6">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2905874615-1">}</span><span class="p">.</span></code></pre><p>OTP also supports changing the internal state of behaviour processes; see
│ │ │ │ +<a href="release_handling.xhtml#appup">Release Handling</a>, <code class="inline">ch_app.appup</code> looks as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7847126700-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7847126700-2">[</span><span class="p" data-group-id="7847126700-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7847126700-4">[</span><span class="p" data-group-id="7847126700-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="7847126700-5">}</span><span class="p" data-group-id="7847126700-4">]</span><span class="p" data-group-id="7847126700-3">}</span><span class="p" data-group-id="7847126700-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7847126700-6">[</span><span class="p" data-group-id="7847126700-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7847126700-8">[</span><span class="p" data-group-id="7847126700-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="7847126700-9">}</span><span class="p" data-group-id="7847126700-8">]</span><span class="p" data-group-id="7847126700-7">}</span><span class="p" data-group-id="7847126700-6">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7847126700-1">}</span><span class="p">.</span></code></pre><p>OTP also supports changing the internal state of behaviour processes; see
│ │ │ │  <a href="appup_cookbook.xhtml#int_state">Changing Internal State</a>.</p><p><a href="" id="int_state"></a></p><h2 id="changing-internal-state" class="section-heading">
│ │ │ │    <a href="#changing-internal-state" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing Internal State</span>
│ │ │ │  </h2>
│ │ │ │  <p>In this case, simple code replacement is not sufficient. The process must
│ │ │ │  explicitly transform its state using the callback function <code class="inline">code_change/3</code> before
│ │ │ │  switching to the new version of the callback module. Thus, synchronized code
│ │ │ │  replacement is used.</p><p><em>Example</em></p><p>Consider the <code class="inline">ch3</code> module from
│ │ │ │  <a href="gen_server_concepts.xhtml#ex">gen_server Behaviour</a>. The internal state is a term
│ │ │ │  <code class="inline">Chs</code> representing the available channels. Assume you want to add a counter <code class="inline">N</code>,
│ │ │ │  which keeps track of the number of <code class="inline">alloc</code> requests so far. This means that the
│ │ │ │ -format must be changed to <code class="inline">{Chs,N}</code>.</p><p>The <code class="inline">.appup</code> file can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3932141604-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3932141604-2">[</span><span class="p" data-group-id="3932141604-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3932141604-4">[</span><span class="p" data-group-id="3932141604-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3932141604-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3932141604-7">[</span><span class="p" data-group-id="3932141604-7">]</span><span class="p" data-group-id="3932141604-6">}</span><span class="p" data-group-id="3932141604-5">}</span><span class="p" data-group-id="3932141604-4">]</span><span class="p" data-group-id="3932141604-3">}</span><span class="p" data-group-id="3932141604-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3932141604-8">[</span><span class="p" data-group-id="3932141604-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3932141604-10">[</span><span class="p" data-group-id="3932141604-11">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3932141604-12">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3932141604-13">[</span><span class="p" data-group-id="3932141604-13">]</span><span class="p" data-group-id="3932141604-12">}</span><span class="p" data-group-id="3932141604-11">}</span><span class="p" data-group-id="3932141604-10">]</span><span class="p" data-group-id="3932141604-9">}</span><span class="p" data-group-id="3932141604-8">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3932141604-1">}</span><span class="p">.</span></code></pre><p>The third element of the <code class="inline">update</code> instruction is a tuple <code class="inline">{advanced,Extra}</code>,
│ │ │ │ +format must be changed to <code class="inline">{Chs,N}</code>.</p><p>The <code class="inline">.appup</code> file can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2227920924-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="2227920924-2">[</span><span class="p" data-group-id="2227920924-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2227920924-4">[</span><span class="p" data-group-id="2227920924-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2227920924-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2227920924-7">[</span><span class="p" data-group-id="2227920924-7">]</span><span class="p" data-group-id="2227920924-6">}</span><span class="p" data-group-id="2227920924-5">}</span><span class="p" data-group-id="2227920924-4">]</span><span class="p" data-group-id="2227920924-3">}</span><span class="p" data-group-id="2227920924-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="2227920924-8">[</span><span class="p" data-group-id="2227920924-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2227920924-10">[</span><span class="p" data-group-id="2227920924-11">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2227920924-12">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2227920924-13">[</span><span class="p" data-group-id="2227920924-13">]</span><span class="p" data-group-id="2227920924-12">}</span><span class="p" data-group-id="2227920924-11">}</span><span class="p" data-group-id="2227920924-10">]</span><span class="p" data-group-id="2227920924-9">}</span><span class="p" data-group-id="2227920924-8">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2227920924-1">}</span><span class="p">.</span></code></pre><p>The third element of the <code class="inline">update</code> instruction is a tuple <code class="inline">{advanced,Extra}</code>,
│ │ │ │  which says that the affected processes are to do a state transformation before
│ │ │ │  loading the new version of the module. This is done by the processes calling the
│ │ │ │  callback function <code class="inline">code_change/3</code> (see <a href="../../../lib/stdlib/doc/html/gen_server.html"><code class="inline">gen_server</code></a> in STDLIB).
│ │ │ │ -The term <code class="inline">Extra</code>, in this case <code class="inline">[]</code>, is passed as is to the function:</p><p><a href="" id="code_change"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3745929164-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="3745929164-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +The term <code class="inline">Extra</code>, in this case <code class="inline">[]</code>, is passed as is to the function:</p><p><a href="" id="code_change"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0103740242-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="0103740242-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3745929164-2">(</span><span class="p" data-group-id="3745929164-3">[</span><span class="ss">code_change</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="3745929164-3">]</span><span class="p" data-group-id="3745929164-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0103740242-2">(</span><span class="p" data-group-id="0103740242-3">[</span><span class="ss">code_change</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="0103740242-3">]</span><span class="p" data-group-id="0103740242-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">code_change</span><span class="p" data-group-id="3745929164-4">(</span><span class="p" data-group-id="3745929164-5">{</span><span class="ss">down</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Vsn</span><span class="p" data-group-id="3745929164-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3745929164-6">{</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p" data-group-id="3745929164-6">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="3745929164-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3745929164-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3745929164-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">code_change</span><span class="p" data-group-id="3745929164-8">(</span><span class="p">_</span><span class="n">Vsn</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="3745929164-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3745929164-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3745929164-10">{</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="3745929164-10">}</span><span class="p" data-group-id="3745929164-9">}</span><span class="p">.</span></code></pre><p>The first argument is <code class="inline">{down,Vsn}</code> if there is a downgrade, or <code class="inline">Vsn</code> if there is
│ │ │ │ +</span><span class="nf">code_change</span><span class="p" data-group-id="0103740242-4">(</span><span class="p" data-group-id="0103740242-5">{</span><span class="ss">down</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Vsn</span><span class="p" data-group-id="0103740242-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0103740242-6">{</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p" data-group-id="0103740242-6">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="0103740242-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0103740242-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="0103740242-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">code_change</span><span class="p" data-group-id="0103740242-8">(</span><span class="p">_</span><span class="n">Vsn</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="0103740242-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0103740242-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0103740242-10">{</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="0103740242-10">}</span><span class="p" data-group-id="0103740242-9">}</span><span class="p">.</span></code></pre><p>The first argument is <code class="inline">{down,Vsn}</code> if there is a downgrade, or <code class="inline">Vsn</code> if there is
│ │ │ │  an upgrade. The term <code class="inline">Vsn</code> is fetched from the 'original' version of the module,
│ │ │ │  that is, the version you are upgrading from, or downgrading to.</p><p>The version is defined by the module attribute <code class="inline">vsn</code>, if any. There is no such
│ │ │ │  attribute in <code class="inline">ch3</code>, so in this case the version is the checksum (a huge integer)
│ │ │ │  of the beam file, an uninteresting value, which is ignored.</p><p>The other callback functions of <code class="inline">ch3</code> must also be modified and perhaps a new
│ │ │ │  interface function must be added, but this is not shown here.</p><h2 id="module-dependencies" class="section-heading">
│ │ │ │    <a href="#module-dependencies" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │ @@ -95,67 +95,67 @@
│ │ │ │  </h2>
│ │ │ │  <p>Assume that a module is extended by adding an interface function, as in the
│ │ │ │  example in <a href="release_handling.xhtml#appup">Release Handling</a>, where a function
│ │ │ │  <code class="inline">available/0</code> is added to <code class="inline">ch3</code>.</p><p>If a call is added to this function, say in module <code class="inline">m1</code>, a runtime error could
│ │ │ │  occur during release upgrade if the new version of <code class="inline">m1</code> is loaded first and
│ │ │ │  calls <code class="inline">ch3:available/0</code> before the new version of <code class="inline">ch3</code> is loaded.</p><p>Thus, <code class="inline">ch3</code> must be loaded before <code class="inline">m1</code>, in the upgrade case, and conversely in
│ │ │ │  the downgrade case. <code class="inline">m1</code> is said to be <em>dependent on</em> <code class="inline">ch3</code>. In a release
│ │ │ │ -handling instruction, this is expressed by the <code class="inline">DepMods</code> element:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4592621485-1">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">DepMods</span><span class="p" data-group-id="4592621485-1">}</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4592621485-2">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4592621485-3">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="4592621485-3">}</span><span class="p">,</span><span class="w"> </span><span class="n">DepMods</span><span class="p" data-group-id="4592621485-2">}</span></code></pre><p><code class="inline">DepMods</code> is a list of modules, on which <code class="inline">Module</code> is dependent.</p><p><em>Example</em></p><p>The module <code class="inline">m1</code> in application <code class="inline">myapp</code> is dependent on <code class="inline">ch3</code> when
│ │ │ │ +handling instruction, this is expressed by the <code class="inline">DepMods</code> element:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3411290152-1">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">DepMods</span><span class="p" data-group-id="3411290152-1">}</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3411290152-2">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3411290152-3">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="3411290152-3">}</span><span class="p">,</span><span class="w"> </span><span class="n">DepMods</span><span class="p" data-group-id="3411290152-2">}</span></code></pre><p><code class="inline">DepMods</code> is a list of modules, on which <code class="inline">Module</code> is dependent.</p><p><em>Example</em></p><p>The module <code class="inline">m1</code> in application <code class="inline">myapp</code> is dependent on <code class="inline">ch3</code> when
│ │ │ │  upgrading from &quot;1&quot; to &quot;2&quot;, or downgrading from &quot;2&quot; to &quot;1&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="ss">myapp</span><span class="p">.</span><span class="nc">appup</span><span class="p">:</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="p" data-group-id="4791457938-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4791457938-2">[</span><span class="p" data-group-id="4791457938-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4791457938-4">[</span><span class="p" data-group-id="4791457938-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4791457938-6">[</span><span class="ss">ch3</span><span class="p" data-group-id="4791457938-6">]</span><span class="p" data-group-id="4791457938-5">}</span><span class="p" data-group-id="4791457938-4">]</span><span class="p" data-group-id="4791457938-3">}</span><span class="p" data-group-id="4791457938-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4791457938-7">[</span><span class="p" data-group-id="4791457938-8">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4791457938-9">[</span><span class="p" data-group-id="4791457938-10">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4791457938-11">[</span><span class="ss">ch3</span><span class="p" data-group-id="4791457938-11">]</span><span class="p" data-group-id="4791457938-10">}</span><span class="p" data-group-id="4791457938-9">]</span><span class="p" data-group-id="4791457938-8">}</span><span class="p" data-group-id="4791457938-7">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4791457938-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9818454302-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9818454302-2">[</span><span class="p" data-group-id="9818454302-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9818454302-4">[</span><span class="p" data-group-id="9818454302-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9818454302-6">[</span><span class="ss">ch3</span><span class="p" data-group-id="9818454302-6">]</span><span class="p" data-group-id="9818454302-5">}</span><span class="p" data-group-id="9818454302-4">]</span><span class="p" data-group-id="9818454302-3">}</span><span class="p" data-group-id="9818454302-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9818454302-7">[</span><span class="p" data-group-id="9818454302-8">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9818454302-9">[</span><span class="p" data-group-id="9818454302-10">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9818454302-11">[</span><span class="ss">ch3</span><span class="p" data-group-id="9818454302-11">]</span><span class="p" data-group-id="9818454302-10">}</span><span class="p" data-group-id="9818454302-9">]</span><span class="p" data-group-id="9818454302-8">}</span><span class="p" data-group-id="9818454302-7">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9818454302-1">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="ss">ch_app</span><span class="p">.</span><span class="nc">appup</span><span class="p">:</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="p" data-group-id="4791457938-12">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4791457938-13">[</span><span class="p" data-group-id="4791457938-14">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4791457938-15">[</span><span class="p" data-group-id="4791457938-16">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="4791457938-16">}</span><span class="p" data-group-id="4791457938-15">]</span><span class="p" data-group-id="4791457938-14">}</span><span class="p" data-group-id="4791457938-13">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4791457938-17">[</span><span class="p" data-group-id="4791457938-18">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4791457938-19">[</span><span class="p" data-group-id="4791457938-20">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="4791457938-20">}</span><span class="p" data-group-id="4791457938-19">]</span><span class="p" data-group-id="4791457938-18">}</span><span class="p" data-group-id="4791457938-17">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4791457938-12">}</span><span class="p">.</span></code></pre><p>If instead <code class="inline">m1</code> and <code class="inline">ch3</code> belong to the same application, the <code class="inline">.appup</code> file can
│ │ │ │ -look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3949451218-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3949451218-2">[</span><span class="p" data-group-id="3949451218-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="3949451218-4">[</span><span class="p" data-group-id="3949451218-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="3949451218-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3949451218-6">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3949451218-7">[</span><span class="ss">ch3</span><span class="p" data-group-id="3949451218-7">]</span><span class="p" data-group-id="3949451218-6">}</span><span class="p" data-group-id="3949451218-4">]</span><span class="p" data-group-id="3949451218-3">}</span><span class="p" data-group-id="3949451218-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3949451218-8">[</span><span class="p" data-group-id="3949451218-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="3949451218-10">[</span><span class="p" data-group-id="3949451218-11">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="3949451218-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3949451218-12">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3949451218-13">[</span><span class="ss">ch3</span><span class="p" data-group-id="3949451218-13">]</span><span class="p" data-group-id="3949451218-12">}</span><span class="p" data-group-id="3949451218-10">]</span><span class="p" data-group-id="3949451218-9">}</span><span class="p" data-group-id="3949451218-8">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3949451218-1">}</span><span class="p">.</span></code></pre><p><code class="inline">m1</code> is dependent on <code class="inline">ch3</code> also when downgrading. <code class="inline">systools</code> knows the
│ │ │ │ +</span><span class="p" data-group-id="9818454302-12">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9818454302-13">[</span><span class="p" data-group-id="9818454302-14">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9818454302-15">[</span><span class="p" data-group-id="9818454302-16">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="9818454302-16">}</span><span class="p" data-group-id="9818454302-15">]</span><span class="p" data-group-id="9818454302-14">}</span><span class="p" data-group-id="9818454302-13">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9818454302-17">[</span><span class="p" data-group-id="9818454302-18">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9818454302-19">[</span><span class="p" data-group-id="9818454302-20">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="9818454302-20">}</span><span class="p" data-group-id="9818454302-19">]</span><span class="p" data-group-id="9818454302-18">}</span><span class="p" data-group-id="9818454302-17">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9818454302-12">}</span><span class="p">.</span></code></pre><p>If instead <code class="inline">m1</code> and <code class="inline">ch3</code> belong to the same application, the <code class="inline">.appup</code> file can
│ │ │ │ +look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3240175472-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="3240175472-2">[</span><span class="p" data-group-id="3240175472-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="3240175472-4">[</span><span class="p" data-group-id="3240175472-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="3240175472-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3240175472-6">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3240175472-7">[</span><span class="ss">ch3</span><span class="p" data-group-id="3240175472-7">]</span><span class="p" data-group-id="3240175472-6">}</span><span class="p" data-group-id="3240175472-4">]</span><span class="p" data-group-id="3240175472-3">}</span><span class="p" data-group-id="3240175472-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="3240175472-8">[</span><span class="p" data-group-id="3240175472-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="3240175472-10">[</span><span class="p" data-group-id="3240175472-11">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="3240175472-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3240175472-12">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3240175472-13">[</span><span class="ss">ch3</span><span class="p" data-group-id="3240175472-13">]</span><span class="p" data-group-id="3240175472-12">}</span><span class="p" data-group-id="3240175472-10">]</span><span class="p" data-group-id="3240175472-9">}</span><span class="p" data-group-id="3240175472-8">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3240175472-1">}</span><span class="p">.</span></code></pre><p><code class="inline">m1</code> is dependent on <code class="inline">ch3</code> also when downgrading. <code class="inline">systools</code> knows the
│ │ │ │  difference between up- and downgrading and generates a correct <code class="inline">relup</code>, where
│ │ │ │  <code class="inline">ch3</code> is loaded before <code class="inline">m1</code> when upgrading, but <code class="inline">m1</code> is loaded before <code class="inline">ch3</code> when
│ │ │ │  downgrading.</p><p><a href="" id="spec"></a></p><h2 id="changing-code-for-a-special-process" class="section-heading">
│ │ │ │    <a href="#changing-code-for-a-special-process" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing Code for a Special Process</span>
│ │ │ │  </h2>
│ │ │ │  <p>In this case, simple code replacement is not sufficient. When a new version of a
│ │ │ │  residence module for a special process is loaded, the process must make a fully
│ │ │ │  qualified call to its loop function to switch to the new code. Thus,
│ │ │ │  synchronized code replacement must be used.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The name(s) of the user-defined residence module(s) must be listed in the
│ │ │ │  <code class="inline">Modules</code> part of the child specification for the special process. Otherwise
│ │ │ │  the release handler cannot find the process.</p></section><p><em>Example</em></p><p>Consider the example <code class="inline">ch4</code> in <a href="spec_proc.xhtml#ex">sys and proc_lib</a>.
│ │ │ │ -When started by a supervisor, the child specification can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7443391812-1">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7443391812-2">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7443391812-3">[</span><span class="p" data-group-id="7443391812-3">]</span><span class="p" data-group-id="7443391812-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="ss">permanent</span><span class="p">,</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p">,</span><span class="w"> </span><span class="ss">worker</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7443391812-4">[</span><span class="ss">ch4</span><span class="p" data-group-id="7443391812-4">]</span><span class="p" data-group-id="7443391812-1">}</span></code></pre><p>If <code class="inline">ch4</code> is part of the application <code class="inline">sp_app</code> and a new version of the module is
│ │ │ │ +When started by a supervisor, the child specification can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0988837531-1">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0988837531-2">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0988837531-3">[</span><span class="p" data-group-id="0988837531-3">]</span><span class="p" data-group-id="0988837531-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="ss">permanent</span><span class="p">,</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p">,</span><span class="w"> </span><span class="ss">worker</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0988837531-4">[</span><span class="ss">ch4</span><span class="p" data-group-id="0988837531-4">]</span><span class="p" data-group-id="0988837531-1">}</span></code></pre><p>If <code class="inline">ch4</code> is part of the application <code class="inline">sp_app</code> and a new version of the module is
│ │ │ │  to be loaded when upgrading from version &quot;1&quot; to &quot;2&quot; of this application,
│ │ │ │ -<code class="inline">sp_app.appup</code> can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1445411168-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1445411168-2">[</span><span class="p" data-group-id="1445411168-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1445411168-4">[</span><span class="p" data-group-id="1445411168-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1445411168-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1445411168-7">[</span><span class="p" data-group-id="1445411168-7">]</span><span class="p" data-group-id="1445411168-6">}</span><span class="p" data-group-id="1445411168-5">}</span><span class="p" data-group-id="1445411168-4">]</span><span class="p" data-group-id="1445411168-3">}</span><span class="p" data-group-id="1445411168-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1445411168-8">[</span><span class="p" data-group-id="1445411168-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1445411168-10">[</span><span class="p" data-group-id="1445411168-11">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1445411168-12">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1445411168-13">[</span><span class="p" data-group-id="1445411168-13">]</span><span class="p" data-group-id="1445411168-12">}</span><span class="p" data-group-id="1445411168-11">}</span><span class="p" data-group-id="1445411168-10">]</span><span class="p" data-group-id="1445411168-9">}</span><span class="p" data-group-id="1445411168-8">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1445411168-1">}</span><span class="p">.</span></code></pre><p>The <code class="inline">update</code> instruction must contain the tuple <code class="inline">{advanced,Extra}</code>. The
│ │ │ │ +<code class="inline">sp_app.appup</code> can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7054191995-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7054191995-2">[</span><span class="p" data-group-id="7054191995-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7054191995-4">[</span><span class="p" data-group-id="7054191995-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7054191995-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7054191995-7">[</span><span class="p" data-group-id="7054191995-7">]</span><span class="p" data-group-id="7054191995-6">}</span><span class="p" data-group-id="7054191995-5">}</span><span class="p" data-group-id="7054191995-4">]</span><span class="p" data-group-id="7054191995-3">}</span><span class="p" data-group-id="7054191995-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7054191995-8">[</span><span class="p" data-group-id="7054191995-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7054191995-10">[</span><span class="p" data-group-id="7054191995-11">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7054191995-12">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7054191995-13">[</span><span class="p" data-group-id="7054191995-13">]</span><span class="p" data-group-id="7054191995-12">}</span><span class="p" data-group-id="7054191995-11">}</span><span class="p" data-group-id="7054191995-10">]</span><span class="p" data-group-id="7054191995-9">}</span><span class="p" data-group-id="7054191995-8">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7054191995-1">}</span><span class="p">.</span></code></pre><p>The <code class="inline">update</code> instruction must contain the tuple <code class="inline">{advanced,Extra}</code>. The
│ │ │ │  instruction makes the special process call the callback function
│ │ │ │  <code class="inline">system_code_change/4</code>, a function the user must implement. The term <code class="inline">Extra</code>, in
│ │ │ │ -this case <code class="inline">[]</code>, is passed as is to <code class="inline">system_code_change/4</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6091085581-1">(</span><span class="ss">ch4</span><span class="p" data-group-id="6091085581-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +this case <code class="inline">[]</code>, is passed as is to <code class="inline">system_code_change/4</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5988994032-1">(</span><span class="ss">ch4</span><span class="p" data-group-id="5988994032-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6091085581-2">(</span><span class="p" data-group-id="6091085581-3">[</span><span class="ss">system_code_change</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="6091085581-3">]</span><span class="p" data-group-id="6091085581-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5988994032-2">(</span><span class="p" data-group-id="5988994032-3">[</span><span class="ss">system_code_change</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="5988994032-3">]</span><span class="p" data-group-id="5988994032-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_code_change</span><span class="p" data-group-id="6091085581-4">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="6091085581-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6091085581-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6091085581-5">}</span><span class="p">.</span></code></pre><ul><li>The first argument is the internal state <code class="inline">State</code>, passed from
│ │ │ │ +</span><span class="nf">system_code_change</span><span class="p" data-group-id="5988994032-4">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="5988994032-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5988994032-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="5988994032-5">}</span><span class="p">.</span></code></pre><ul><li>The first argument is the internal state <code class="inline">State</code>, passed from
│ │ │ │  function <a href="../../../lib/stdlib/doc/html/sys.html#handle_system_msg/6"><code class="inline">sys:handle_system_msg(Request, From, Parent, Module, Deb, State)</code></a>, and called by the special
│ │ │ │  process when a system message is received. In <code class="inline">ch4</code>, the internal
│ │ │ │  state is the set of available channels <code class="inline">Chs</code>.</li><li>The second argument is the name of the module (<code class="inline">ch4</code>).</li><li>The third argument is <code class="inline">Vsn</code> or <code class="inline">{down,Vsn}</code>, as described for
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_server.html#c:code_change/3"><code class="inline">gen_server:code_change/3</code></a> in
│ │ │ │  <a href="appup_cookbook.xhtml#code_change">Changing Internal State</a>.</li></ul><p>In this case, all arguments but the first are ignored and the function simply
│ │ │ │  returns the internal state again. This is enough if the code only has been
│ │ │ │  extended. If instead the internal state is changed (similar to the example in
│ │ │ │ @@ -176,86 +176,86 @@
│ │ │ │    <span class="text">Changing Properties</span>
│ │ │ │  </h3>
│ │ │ │  <p>Since the supervisor is to change its internal state, synchronized code
│ │ │ │  replacement is required. However, a special <code class="inline">update</code> instruction must be used.</p><p>First, the new version of the callback module must be loaded, both in the case
│ │ │ │  of upgrade and downgrade. Then the new return value of <code class="inline">init/1</code> can be checked
│ │ │ │  and the internal state be changed accordingly.</p><p>The following <code class="inline">upgrade</code> instruction is used for supervisors:</p><pre><code class="text">{update, Module, supervisor}</code></pre><p><em>Example</em></p><p>To change the restart strategy of <code class="inline">ch_sup</code> (from
│ │ │ │  <a href="sup_princ.xhtml#ex">Supervisor Behaviour</a>) from <code class="inline">one_for_one</code> to <code class="inline">one_for_all</code>,
│ │ │ │ -change the callback function <code class="inline">init/1</code> in <code class="inline">ch_sup.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5850163545-1">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="5850163545-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +change the callback function <code class="inline">init/1</code> in <code class="inline">ch_sup.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6540669707-1">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="6540669707-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="5850163545-2">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="5850163545-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5850163545-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5850163545-4">{</span><span class="p" data-group-id="5850163545-5">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">one_for_all</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="5850163545-5">}</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="5850163545-4">}</span><span class="p" data-group-id="5850163545-3">}</span><span class="p">.</span></code></pre><p>The file <code class="inline">ch_app.appup</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2766256568-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2766256568-2">[</span><span class="p" data-group-id="2766256568-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2766256568-4">[</span><span class="p" data-group-id="2766256568-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="2766256568-5">}</span><span class="p" data-group-id="2766256568-4">]</span><span class="p" data-group-id="2766256568-3">}</span><span class="p" data-group-id="2766256568-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2766256568-6">[</span><span class="p" data-group-id="2766256568-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2766256568-8">[</span><span class="p" data-group-id="2766256568-9">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="2766256568-9">}</span><span class="p" data-group-id="2766256568-8">]</span><span class="p" data-group-id="2766256568-7">}</span><span class="p" data-group-id="2766256568-6">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2766256568-1">}</span><span class="p">.</span></code></pre><h3 id="changing-child-specifications" class="section-heading">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="6540669707-2">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="6540669707-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6540669707-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6540669707-4">{</span><span class="p" data-group-id="6540669707-5">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">one_for_all</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6540669707-5">}</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6540669707-4">}</span><span class="p" data-group-id="6540669707-3">}</span><span class="p">.</span></code></pre><p>The file <code class="inline">ch_app.appup</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6673650197-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6673650197-2">[</span><span class="p" data-group-id="6673650197-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6673650197-4">[</span><span class="p" data-group-id="6673650197-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="6673650197-5">}</span><span class="p" data-group-id="6673650197-4">]</span><span class="p" data-group-id="6673650197-3">}</span><span class="p" data-group-id="6673650197-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6673650197-6">[</span><span class="p" data-group-id="6673650197-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6673650197-8">[</span><span class="p" data-group-id="6673650197-9">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="6673650197-9">}</span><span class="p" data-group-id="6673650197-8">]</span><span class="p" data-group-id="6673650197-7">}</span><span class="p" data-group-id="6673650197-6">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6673650197-1">}</span><span class="p">.</span></code></pre><h3 id="changing-child-specifications" class="section-heading">
│ │ │ │    <a href="#changing-child-specifications" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing Child Specifications</span>
│ │ │ │  </h3>
│ │ │ │  <p>The instruction, and thus the <code class="inline">.appup</code> file, when changing an existing child
│ │ │ │ -specification, is the same as when changing properties as described earlier:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2785833742-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2785833742-2">[</span><span class="p" data-group-id="2785833742-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2785833742-4">[</span><span class="p" data-group-id="2785833742-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="2785833742-5">}</span><span class="p" data-group-id="2785833742-4">]</span><span class="p" data-group-id="2785833742-3">}</span><span class="p" data-group-id="2785833742-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2785833742-6">[</span><span class="p" data-group-id="2785833742-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2785833742-8">[</span><span class="p" data-group-id="2785833742-9">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="2785833742-9">}</span><span class="p" data-group-id="2785833742-8">]</span><span class="p" data-group-id="2785833742-7">}</span><span class="p" data-group-id="2785833742-6">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2785833742-1">}</span><span class="p">.</span></code></pre><p>The changes do not affect existing child processes. For example, changing the
│ │ │ │ +specification, is the same as when changing properties as described earlier:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9162976579-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9162976579-2">[</span><span class="p" data-group-id="9162976579-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9162976579-4">[</span><span class="p" data-group-id="9162976579-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="9162976579-5">}</span><span class="p" data-group-id="9162976579-4">]</span><span class="p" data-group-id="9162976579-3">}</span><span class="p" data-group-id="9162976579-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9162976579-6">[</span><span class="p" data-group-id="9162976579-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9162976579-8">[</span><span class="p" data-group-id="9162976579-9">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="9162976579-9">}</span><span class="p" data-group-id="9162976579-8">]</span><span class="p" data-group-id="9162976579-7">}</span><span class="p" data-group-id="9162976579-6">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9162976579-1">}</span><span class="p">.</span></code></pre><p>The changes do not affect existing child processes. For example, changing the
│ │ │ │  start function only specifies how the child process is to be restarted, if
│ │ │ │  needed later on.</p><p>The id of the child specification cannot be changed.</p><p>Changing the <code class="inline">Modules</code> field of the child specification can affect the release
│ │ │ │  handling process itself, as this field is used to identify which processes are
│ │ │ │  affected when doing a synchronized code replacement.</p><p><a href="" id="sup_add"></a></p><h3 id="adding-and-deleting-child-processes" class="section-heading">
│ │ │ │    <a href="#adding-and-deleting-child-processes" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Adding and Deleting Child Processes</span>
│ │ │ │  </h3>
│ │ │ │  <p>As stated earlier, changing child specifications does not affect existing child
│ │ │ │  processes. New child specifications are automatically added, but not deleted.
│ │ │ │  Child processes are not automatically started or terminated, this must be done
│ │ │ │  using <code class="inline">apply</code> instructions.</p><p><em>Example</em></p><p>Assume a new child process <code class="inline">m1</code> is to be added to <code class="inline">ch_sup</code> when
│ │ │ │  upgrading <code class="inline">ch_app</code> from &quot;1&quot; to &quot;2&quot;. This means <code class="inline">m1</code> is to be deleted when
│ │ │ │ -downgrading from &quot;2&quot; to &quot;1&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1733240929-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1733240929-2">[</span><span class="p" data-group-id="1733240929-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="1733240929-4">[</span><span class="p" data-group-id="1733240929-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="1733240929-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1733240929-6">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1733240929-7">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">restart_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1733240929-8">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="1733240929-8">]</span><span class="p" data-group-id="1733240929-7">}</span><span class="p" data-group-id="1733240929-6">}</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="1733240929-4">]</span><span class="p" data-group-id="1733240929-3">}</span><span class="p" data-group-id="1733240929-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1733240929-9">[</span><span class="p" data-group-id="1733240929-10">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="1733240929-11">[</span><span class="p" data-group-id="1733240929-12">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1733240929-13">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1733240929-14">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="1733240929-14">]</span><span class="p" data-group-id="1733240929-13">}</span><span class="p" data-group-id="1733240929-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1733240929-15">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1733240929-16">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">delete_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1733240929-17">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="1733240929-17">]</span><span class="p" data-group-id="1733240929-16">}</span><span class="p" data-group-id="1733240929-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1733240929-18">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="1733240929-18">}</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="1733240929-11">]</span><span class="p" data-group-id="1733240929-10">}</span><span class="p" data-group-id="1733240929-9">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1733240929-1">}</span><span class="p">.</span></code></pre><p>The order of the instructions is important.</p><p>The supervisor must be registered as <code class="inline">ch_sup</code> for the script to work. If the
│ │ │ │ +downgrading from &quot;2&quot; to &quot;1&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8825517548-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8825517548-2">[</span><span class="p" data-group-id="8825517548-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="8825517548-4">[</span><span class="p" data-group-id="8825517548-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="8825517548-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8825517548-6">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8825517548-7">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">restart_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8825517548-8">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="8825517548-8">]</span><span class="p" data-group-id="8825517548-7">}</span><span class="p" data-group-id="8825517548-6">}</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="8825517548-4">]</span><span class="p" data-group-id="8825517548-3">}</span><span class="p" data-group-id="8825517548-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8825517548-9">[</span><span class="p" data-group-id="8825517548-10">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="8825517548-11">[</span><span class="p" data-group-id="8825517548-12">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8825517548-13">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8825517548-14">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="8825517548-14">]</span><span class="p" data-group-id="8825517548-13">}</span><span class="p" data-group-id="8825517548-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8825517548-15">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8825517548-16">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">delete_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8825517548-17">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="8825517548-17">]</span><span class="p" data-group-id="8825517548-16">}</span><span class="p" data-group-id="8825517548-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8825517548-18">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="8825517548-18">}</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="8825517548-11">]</span><span class="p" data-group-id="8825517548-10">}</span><span class="p" data-group-id="8825517548-9">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8825517548-1">}</span><span class="p">.</span></code></pre><p>The order of the instructions is important.</p><p>The supervisor must be registered as <code class="inline">ch_sup</code> for the script to work. If the
│ │ │ │  supervisor is not registered, it cannot be accessed directly from the script.
│ │ │ │  Instead a help function that finds the pid of the supervisor and calls
│ │ │ │  <code class="inline">supervisor:restart_child</code>, and so on, must be written. This function is then to
│ │ │ │  be called from the script using the <code class="inline">apply</code> instruction.</p><p>If the module <code class="inline">m1</code> is introduced in version &quot;2&quot; of <code class="inline">ch_app</code>, it must also be
│ │ │ │ -loaded when upgrading and deleted when downgrading:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4626413729-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4626413729-2">[</span><span class="p" data-group-id="4626413729-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="4626413729-4">[</span><span class="p" data-group-id="4626413729-5">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="4626413729-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4626413729-6">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="4626413729-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4626413729-7">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4626413729-8">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">restart_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4626413729-9">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="4626413729-9">]</span><span class="p" data-group-id="4626413729-8">}</span><span class="p" data-group-id="4626413729-7">}</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="4626413729-4">]</span><span class="p" data-group-id="4626413729-3">}</span><span class="p" data-group-id="4626413729-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4626413729-10">[</span><span class="p" data-group-id="4626413729-11">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="4626413729-12">[</span><span class="p" data-group-id="4626413729-13">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4626413729-14">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4626413729-15">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="4626413729-15">]</span><span class="p" data-group-id="4626413729-14">}</span><span class="p" data-group-id="4626413729-13">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4626413729-16">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4626413729-17">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">delete_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4626413729-18">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="4626413729-18">]</span><span class="p" data-group-id="4626413729-17">}</span><span class="p" data-group-id="4626413729-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4626413729-19">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="4626413729-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4626413729-20">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="4626413729-20">}</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="4626413729-12">]</span><span class="p" data-group-id="4626413729-11">}</span><span class="p" data-group-id="4626413729-10">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4626413729-1">}</span><span class="p">.</span></code></pre><p>As stated earlier, the order of the instructions is important. When upgrading,
│ │ │ │ +loaded when upgrading and deleted when downgrading:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5902298175-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5902298175-2">[</span><span class="p" data-group-id="5902298175-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="5902298175-4">[</span><span class="p" data-group-id="5902298175-5">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="5902298175-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5902298175-6">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="5902298175-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5902298175-7">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5902298175-8">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">restart_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5902298175-9">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="5902298175-9">]</span><span class="p" data-group-id="5902298175-8">}</span><span class="p" data-group-id="5902298175-7">}</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="5902298175-4">]</span><span class="p" data-group-id="5902298175-3">}</span><span class="p" data-group-id="5902298175-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5902298175-10">[</span><span class="p" data-group-id="5902298175-11">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="5902298175-12">[</span><span class="p" data-group-id="5902298175-13">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5902298175-14">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5902298175-15">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="5902298175-15">]</span><span class="p" data-group-id="5902298175-14">}</span><span class="p" data-group-id="5902298175-13">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5902298175-16">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5902298175-17">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">delete_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5902298175-18">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="5902298175-18">]</span><span class="p" data-group-id="5902298175-17">}</span><span class="p" data-group-id="5902298175-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5902298175-19">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="5902298175-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5902298175-20">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="5902298175-20">}</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="5902298175-12">]</span><span class="p" data-group-id="5902298175-11">}</span><span class="p" data-group-id="5902298175-10">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5902298175-1">}</span><span class="p">.</span></code></pre><p>As stated earlier, the order of the instructions is important. When upgrading,
│ │ │ │  <code class="inline">m1</code> must be loaded, and the supervisor child specification changed, before the
│ │ │ │  new child process can be started. When downgrading, the child process must be
│ │ │ │  terminated before the child specification is changed and the module is deleted.</p><h2 id="adding-or-deleting-a-module" class="section-heading">
│ │ │ │    <a href="#adding-or-deleting-a-module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Adding or Deleting a Module</span>
│ │ │ │  </h2>
│ │ │ │ -<p><em>Example</em></p><p>A new functional module <code class="inline">m</code> is added to <code class="inline">ch_app</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0676018825-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="0676018825-2">[</span><span class="p" data-group-id="0676018825-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0676018825-4">[</span><span class="p" data-group-id="0676018825-5">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="0676018825-5">}</span><span class="p" data-group-id="0676018825-4">]</span><span class="p" data-group-id="0676018825-3">}</span><span class="p" data-group-id="0676018825-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="0676018825-6">[</span><span class="p" data-group-id="0676018825-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0676018825-8">[</span><span class="p" data-group-id="0676018825-9">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="0676018825-9">}</span><span class="p" data-group-id="0676018825-8">]</span><span class="p" data-group-id="0676018825-7">}</span><span class="p" data-group-id="0676018825-6">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0676018825-1">}</span><span class="p">.</span></code></pre><h2 id="starting-or-terminating-a-process" class="section-heading">
│ │ │ │ +<p><em>Example</em></p><p>A new functional module <code class="inline">m</code> is added to <code class="inline">ch_app</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9160857062-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9160857062-2">[</span><span class="p" data-group-id="9160857062-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9160857062-4">[</span><span class="p" data-group-id="9160857062-5">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="9160857062-5">}</span><span class="p" data-group-id="9160857062-4">]</span><span class="p" data-group-id="9160857062-3">}</span><span class="p" data-group-id="9160857062-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9160857062-6">[</span><span class="p" data-group-id="9160857062-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9160857062-8">[</span><span class="p" data-group-id="9160857062-9">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="9160857062-9">}</span><span class="p" data-group-id="9160857062-8">]</span><span class="p" data-group-id="9160857062-7">}</span><span class="p" data-group-id="9160857062-6">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9160857062-1">}</span><span class="p">.</span></code></pre><h2 id="starting-or-terminating-a-process" class="section-heading">
│ │ │ │    <a href="#starting-or-terminating-a-process" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Starting or Terminating a Process</span>
│ │ │ │  </h2>
│ │ │ │  <p>In a system structured according to the OTP design principles, any process would
│ │ │ │  be a child process belonging to a supervisor, see
│ │ │ │ @@ -275,29 +275,29 @@
│ │ │ │    <span class="text">Restarting an Application</span>
│ │ │ │  </h2>
│ │ │ │  <p>Restarting an application is useful when a change is too complicated to be made
│ │ │ │  without restarting the processes, for example, if the supervisor hierarchy has
│ │ │ │  been restructured.</p><p><em>Example</em></p><p>When adding a child <code class="inline">m1</code> to <code class="inline">ch_sup</code>, as in
│ │ │ │  <a href="appup_cookbook.xhtml#sup_add">Adding and Deleting Child Processes</a> in Changing a
│ │ │ │  Supervisor, an alternative to updating the supervisor is to restart the entire
│ │ │ │ -application:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4425470392-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4425470392-2">[</span><span class="p" data-group-id="4425470392-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4425470392-4">[</span><span class="p" data-group-id="4425470392-5">{</span><span class="ss">restart_application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p" data-group-id="4425470392-5">}</span><span class="p" data-group-id="4425470392-4">]</span><span class="p" data-group-id="4425470392-3">}</span><span class="p" data-group-id="4425470392-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4425470392-6">[</span><span class="p" data-group-id="4425470392-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4425470392-8">[</span><span class="p" data-group-id="4425470392-9">{</span><span class="ss">restart_application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p" data-group-id="4425470392-9">}</span><span class="p" data-group-id="4425470392-8">]</span><span class="p" data-group-id="4425470392-7">}</span><span class="p" data-group-id="4425470392-6">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4425470392-1">}</span><span class="p">.</span></code></pre><p><a href="" id="app_spec"></a></p><h2 id="changing-an-application-specification" class="section-heading">
│ │ │ │ +application:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4473263853-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="4473263853-2">[</span><span class="p" data-group-id="4473263853-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4473263853-4">[</span><span class="p" data-group-id="4473263853-5">{</span><span class="ss">restart_application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p" data-group-id="4473263853-5">}</span><span class="p" data-group-id="4473263853-4">]</span><span class="p" data-group-id="4473263853-3">}</span><span class="p" data-group-id="4473263853-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="4473263853-6">[</span><span class="p" data-group-id="4473263853-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4473263853-8">[</span><span class="p" data-group-id="4473263853-9">{</span><span class="ss">restart_application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p" data-group-id="4473263853-9">}</span><span class="p" data-group-id="4473263853-8">]</span><span class="p" data-group-id="4473263853-7">}</span><span class="p" data-group-id="4473263853-6">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4473263853-1">}</span><span class="p">.</span></code></pre><p><a href="" id="app_spec"></a></p><h2 id="changing-an-application-specification" class="section-heading">
│ │ │ │    <a href="#changing-an-application-specification" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing an Application Specification</span>
│ │ │ │  </h2>
│ │ │ │  <p>When installing a release, the application specifications are automatically
│ │ │ │  updated before evaluating the <code class="inline">relup</code> script. Thus, no instructions are needed
│ │ │ │ -in the <code class="inline">.appup</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1725251624-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1725251624-2">[</span><span class="p" data-group-id="1725251624-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1725251624-4">[</span><span class="p" data-group-id="1725251624-4">]</span><span class="p" data-group-id="1725251624-3">}</span><span class="p" data-group-id="1725251624-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1725251624-5">[</span><span class="p" data-group-id="1725251624-6">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1725251624-7">[</span><span class="p" data-group-id="1725251624-7">]</span><span class="p" data-group-id="1725251624-6">}</span><span class="p" data-group-id="1725251624-5">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1725251624-1">}</span><span class="p">.</span></code></pre><h2 id="changing-application-configuration" class="section-heading">
│ │ │ │ +in the <code class="inline">.appup</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3718405198-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="3718405198-2">[</span><span class="p" data-group-id="3718405198-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3718405198-4">[</span><span class="p" data-group-id="3718405198-4">]</span><span class="p" data-group-id="3718405198-3">}</span><span class="p" data-group-id="3718405198-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="3718405198-5">[</span><span class="p" data-group-id="3718405198-6">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3718405198-7">[</span><span class="p" data-group-id="3718405198-7">]</span><span class="p" data-group-id="3718405198-6">}</span><span class="p" data-group-id="3718405198-5">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3718405198-1">}</span><span class="p">.</span></code></pre><h2 id="changing-application-configuration" class="section-heading">
│ │ │ │    <a href="#changing-application-configuration" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing Application Configuration</span>
│ │ │ │  </h2>
│ │ │ │  <p>Changing an application configuration by updating the <code class="inline">env</code> key in the <code class="inline">.app</code>
│ │ │ │  file is an instance of changing an application specification, see the previous
│ │ │ │ @@ -312,26 +312,26 @@
│ │ │ │  applications apply to primary applications only. There are no corresponding
│ │ │ │  instructions for included applications. However, since an included application
│ │ │ │  is really a supervision tree with a topmost supervisor, started as a child
│ │ │ │  process to a supervisor in the including application, a <code class="inline">.relup</code> file can be
│ │ │ │  manually created.</p><p><em>Example</em></p><p>Assume there is a release containing an application <code class="inline">prim_app</code>, which
│ │ │ │  has a supervisor <code class="inline">prim_sup</code> in its supervision tree.</p><p>In a new version of the release, the application <code class="inline">ch_app</code> is to be included in
│ │ │ │  <code class="inline">prim_app</code>. That is, its topmost supervisor <code class="inline">ch_sup</code> is to be started as a child
│ │ │ │ -process to <code class="inline">prim_sup</code>.</p><p>The workflow is as follows:</p><p><em>Step 1)</em> Edit the code for <code class="inline">prim_sup</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="2869428090-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2869428090-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2869428090-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2869428090-3">{</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="ss">supervisor</span><span class="w"> </span><span class="ss">flags</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -          </span><span class="p" data-group-id="2869428090-4">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -           </span><span class="p" data-group-id="2869428090-5">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2869428090-6">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">start_link</span><span class="p">,</span><span class="p" data-group-id="2869428090-7">[</span><span class="p" data-group-id="2869428090-7">]</span><span class="p" data-group-id="2869428090-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="ss">permanent</span><span class="p">,</span><span class="ss">infinity</span><span class="p">,</span><span class="ss">supervisor</span><span class="p">,</span><span class="p" data-group-id="2869428090-8">[</span><span class="ss">ch_sup</span><span class="p" data-group-id="2869428090-8">]</span><span class="p" data-group-id="2869428090-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -           </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2869428090-4">]</span><span class="p" data-group-id="2869428090-3">}</span><span class="p" data-group-id="2869428090-2">}</span><span class="p">.</span></code></pre><p><em>Step 2)</em> Edit the <code class="inline">.app</code> file for <code class="inline">prim_app</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7205393434-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7205393434-2">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="7205393434-3">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="7205393434-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +process to <code class="inline">prim_sup</code>.</p><p>The workflow is as follows:</p><p><em>Step 1)</em> Edit the code for <code class="inline">prim_sup</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="2603241566-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2603241566-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2603241566-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2603241566-3">{</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="ss">supervisor</span><span class="w"> </span><span class="ss">flags</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ +          </span><span class="p" data-group-id="2603241566-4">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ +           </span><span class="p" data-group-id="2603241566-5">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2603241566-6">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">start_link</span><span class="p">,</span><span class="p" data-group-id="2603241566-7">[</span><span class="p" data-group-id="2603241566-7">]</span><span class="p" data-group-id="2603241566-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="ss">permanent</span><span class="p">,</span><span class="ss">infinity</span><span class="p">,</span><span class="ss">supervisor</span><span class="p">,</span><span class="p" data-group-id="2603241566-8">[</span><span class="ss">ch_sup</span><span class="p" data-group-id="2603241566-8">]</span><span class="p" data-group-id="2603241566-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +           </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2603241566-4">]</span><span class="p" data-group-id="2603241566-3">}</span><span class="p" data-group-id="2603241566-2">}</span><span class="p">.</span></code></pre><p><em>Step 2)</em> Edit the <code class="inline">.app</code> file for <code class="inline">prim_app</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7930028966-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7930028966-2">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="7930028966-3">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="7930028966-3">}</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="7205393434-4">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7205393434-5">[</span><span class="ss">ch_app</span><span class="p" data-group-id="7205393434-5">]</span><span class="p" data-group-id="7205393434-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="7930028966-4">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7930028966-5">[</span><span class="ss">ch_app</span><span class="p" data-group-id="7930028966-5">]</span><span class="p" data-group-id="7930028966-4">}</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7205393434-2">]</span><span class="p" data-group-id="7205393434-1">}</span><span class="p">.</span></code></pre><p><em>Step 3)</em> Create a new <code class="inline">.rel</code> file, including <code class="inline">ch_app</code>:</p><pre><code class="text">{release,
│ │ │ │ + </span><span class="p" data-group-id="7930028966-2">]</span><span class="p" data-group-id="7930028966-1">}</span><span class="p">.</span></code></pre><p><em>Step 3)</em> Create a new <code class="inline">.rel</code> file, including <code class="inline">ch_app</code>:</p><pre><code class="text">{release,
│ │ │ │   ...,
│ │ │ │   [...,
│ │ │ │    {prim_app, &quot;2&quot;},
│ │ │ │    {ch_app, &quot;1&quot;}]}.</code></pre><p>The included application can be started in two ways. This is described in the
│ │ │ │  next two sections.</p><h3 id="application-restart" class="section-heading">
│ │ │ │    <a href="#application-restart" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │ @@ -386,74 +386,74 @@
│ │ │ │  <p><em>Step 4b)</em> Another way to start the included application (or stop it in the case
│ │ │ │  of downgrade) is by combining instructions for adding and removing child
│ │ │ │  processes to/from <code class="inline">prim_sup</code> with instructions for loading/unloading all
│ │ │ │  <code class="inline">ch_app</code> code and its application specification.</p><p>Again, the <code class="inline">.relup</code> file is created manually, either from scratch or by editing a
│ │ │ │  generated version. Load all code for <code class="inline">ch_app</code> first, and also load the
│ │ │ │  application specification, before <code class="inline">prim_sup</code> is updated. When downgrading,
│ │ │ │  <code class="inline">prim_sup</code> is to be updated first, before the code for <code class="inline">ch_app</code> and its application
│ │ │ │ -specification are unloaded.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4879027137-1">{</span><span class="s">&quot;B&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4879027137-2">[</span><span class="p" data-group-id="4879027137-3">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="4879027137-4">[</span><span class="p" data-group-id="4879027137-4">]</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="4879027137-5">[</span><span class="p" data-group-id="4879027137-6">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="4879027137-7">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="p" data-group-id="4879027137-8">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">ch3</span><span class="p" data-group-id="4879027137-8">]</span><span class="p" data-group-id="4879027137-7">}</span><span class="p" data-group-id="4879027137-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-9">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="4879027137-10">{</span><span class="ss">prim_app</span><span class="p">,</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="p" data-group-id="4879027137-11">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="4879027137-11">]</span><span class="p" data-group-id="4879027137-10">}</span><span class="p" data-group-id="4879027137-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +specification are unloaded.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6464050063-1">{</span><span class="s">&quot;B&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6464050063-2">[</span><span class="p" data-group-id="6464050063-3">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="6464050063-4">[</span><span class="p" data-group-id="6464050063-4">]</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="6464050063-5">[</span><span class="p" data-group-id="6464050063-6">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="6464050063-7">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="p" data-group-id="6464050063-8">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">ch3</span><span class="p" data-group-id="6464050063-8">]</span><span class="p" data-group-id="6464050063-7">}</span><span class="p" data-group-id="6464050063-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-9">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="6464050063-10">{</span><span class="ss">prim_app</span><span class="p">,</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="p" data-group-id="6464050063-11">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="6464050063-11">]</span><span class="p" data-group-id="6464050063-10">}</span><span class="p" data-group-id="6464050063-9">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">point_of_no_return</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-12">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="4879027137-13">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="4879027137-13">}</span><span class="p" data-group-id="4879027137-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-14">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="4879027137-15">{</span><span class="ss">ch3</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="4879027137-15">}</span><span class="p" data-group-id="4879027137-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-16">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="4879027137-17">{</span><span class="ss">application</span><span class="p">,</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="4879027137-18">[</span><span class="ss">ch_app</span><span class="p" data-group-id="4879027137-18">]</span><span class="p" data-group-id="4879027137-17">}</span><span class="p" data-group-id="4879027137-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-19">{</span><span class="ss">suspend</span><span class="p">,</span><span class="p" data-group-id="4879027137-20">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="4879027137-20">]</span><span class="p" data-group-id="4879027137-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-21">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="4879027137-22">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="4879027137-22">}</span><span class="p" data-group-id="4879027137-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-23">{</span><span class="ss">code_change</span><span class="p">,</span><span class="ss">up</span><span class="p">,</span><span class="p" data-group-id="4879027137-24">[</span><span class="p" data-group-id="4879027137-25">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="p" data-group-id="4879027137-26">[</span><span class="p" data-group-id="4879027137-26">]</span><span class="p" data-group-id="4879027137-25">}</span><span class="p" data-group-id="4879027137-24">]</span><span class="p" data-group-id="4879027137-23">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-27">{</span><span class="ss">resume</span><span class="p">,</span><span class="p" data-group-id="4879027137-28">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="4879027137-28">]</span><span class="p" data-group-id="4879027137-27">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-29">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="4879027137-30">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">restart_child</span><span class="p">,</span><span class="p" data-group-id="4879027137-31">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="4879027137-31">]</span><span class="p" data-group-id="4879027137-30">}</span><span class="p" data-group-id="4879027137-29">}</span><span class="p" data-group-id="4879027137-5">]</span><span class="p" data-group-id="4879027137-3">}</span><span class="p" data-group-id="4879027137-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4879027137-32">[</span><span class="p" data-group-id="4879027137-33">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="4879027137-34">[</span><span class="p" data-group-id="4879027137-34">]</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="4879027137-35">[</span><span class="p" data-group-id="4879027137-36">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="4879027137-37">{</span><span class="ss">prim_app</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="p" data-group-id="4879027137-38">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="4879027137-38">]</span><span class="p" data-group-id="4879027137-37">}</span><span class="p" data-group-id="4879027137-36">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-12">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="6464050063-13">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="6464050063-13">}</span><span class="p" data-group-id="6464050063-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-14">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="6464050063-15">{</span><span class="ss">ch3</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="6464050063-15">}</span><span class="p" data-group-id="6464050063-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-16">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="6464050063-17">{</span><span class="ss">application</span><span class="p">,</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="6464050063-18">[</span><span class="ss">ch_app</span><span class="p" data-group-id="6464050063-18">]</span><span class="p" data-group-id="6464050063-17">}</span><span class="p" data-group-id="6464050063-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-19">{</span><span class="ss">suspend</span><span class="p">,</span><span class="p" data-group-id="6464050063-20">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="6464050063-20">]</span><span class="p" data-group-id="6464050063-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-21">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="6464050063-22">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="6464050063-22">}</span><span class="p" data-group-id="6464050063-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-23">{</span><span class="ss">code_change</span><span class="p">,</span><span class="ss">up</span><span class="p">,</span><span class="p" data-group-id="6464050063-24">[</span><span class="p" data-group-id="6464050063-25">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="p" data-group-id="6464050063-26">[</span><span class="p" data-group-id="6464050063-26">]</span><span class="p" data-group-id="6464050063-25">}</span><span class="p" data-group-id="6464050063-24">]</span><span class="p" data-group-id="6464050063-23">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-27">{</span><span class="ss">resume</span><span class="p">,</span><span class="p" data-group-id="6464050063-28">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="6464050063-28">]</span><span class="p" data-group-id="6464050063-27">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-29">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="6464050063-30">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">restart_child</span><span class="p">,</span><span class="p" data-group-id="6464050063-31">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="6464050063-31">]</span><span class="p" data-group-id="6464050063-30">}</span><span class="p" data-group-id="6464050063-29">}</span><span class="p" data-group-id="6464050063-5">]</span><span class="p" data-group-id="6464050063-3">}</span><span class="p" data-group-id="6464050063-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6464050063-32">[</span><span class="p" data-group-id="6464050063-33">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="6464050063-34">[</span><span class="p" data-group-id="6464050063-34">]</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="6464050063-35">[</span><span class="p" data-group-id="6464050063-36">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="6464050063-37">{</span><span class="ss">prim_app</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="p" data-group-id="6464050063-38">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="6464050063-38">]</span><span class="p" data-group-id="6464050063-37">}</span><span class="p" data-group-id="6464050063-36">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">point_of_no_return</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-39">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="4879027137-40">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">terminate_child</span><span class="p">,</span><span class="p" data-group-id="4879027137-41">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="4879027137-41">]</span><span class="p" data-group-id="4879027137-40">}</span><span class="p" data-group-id="4879027137-39">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-42">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="4879027137-43">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">delete_child</span><span class="p">,</span><span class="p" data-group-id="4879027137-44">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="4879027137-44">]</span><span class="p" data-group-id="4879027137-43">}</span><span class="p" data-group-id="4879027137-42">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-45">{</span><span class="ss">suspend</span><span class="p">,</span><span class="p" data-group-id="4879027137-46">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="4879027137-46">]</span><span class="p" data-group-id="4879027137-45">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-47">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="4879027137-48">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="4879027137-48">}</span><span class="p" data-group-id="4879027137-47">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-49">{</span><span class="ss">code_change</span><span class="p">,</span><span class="ss">down</span><span class="p">,</span><span class="p" data-group-id="4879027137-50">[</span><span class="p" data-group-id="4879027137-51">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="p" data-group-id="4879027137-52">[</span><span class="p" data-group-id="4879027137-52">]</span><span class="p" data-group-id="4879027137-51">}</span><span class="p" data-group-id="4879027137-50">]</span><span class="p" data-group-id="4879027137-49">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-53">{</span><span class="ss">resume</span><span class="p">,</span><span class="p" data-group-id="4879027137-54">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="4879027137-54">]</span><span class="p" data-group-id="4879027137-53">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-55">{</span><span class="ss">remove</span><span class="p">,</span><span class="p" data-group-id="4879027137-56">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="4879027137-56">}</span><span class="p" data-group-id="4879027137-55">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-57">{</span><span class="ss">remove</span><span class="p">,</span><span class="p" data-group-id="4879027137-58">{</span><span class="ss">ch3</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="4879027137-58">}</span><span class="p" data-group-id="4879027137-57">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-59">{</span><span class="ss">purge</span><span class="p">,</span><span class="p" data-group-id="4879027137-60">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">ch3</span><span class="p" data-group-id="4879027137-60">]</span><span class="p" data-group-id="4879027137-59">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4879027137-61">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="4879027137-62">{</span><span class="ss">application</span><span class="p">,</span><span class="ss">unload</span><span class="p">,</span><span class="p" data-group-id="4879027137-63">[</span><span class="ss">ch_app</span><span class="p" data-group-id="4879027137-63">]</span><span class="p" data-group-id="4879027137-62">}</span><span class="p" data-group-id="4879027137-61">}</span><span class="p" data-group-id="4879027137-35">]</span><span class="p" data-group-id="4879027137-33">}</span><span class="p" data-group-id="4879027137-32">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4879027137-1">}</span><span class="p">.</span></code></pre><h2 id="changing-non-erlang-code" class="section-heading">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-39">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="6464050063-40">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">terminate_child</span><span class="p">,</span><span class="p" data-group-id="6464050063-41">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="6464050063-41">]</span><span class="p" data-group-id="6464050063-40">}</span><span class="p" data-group-id="6464050063-39">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-42">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="6464050063-43">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">delete_child</span><span class="p">,</span><span class="p" data-group-id="6464050063-44">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="6464050063-44">]</span><span class="p" data-group-id="6464050063-43">}</span><span class="p" data-group-id="6464050063-42">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-45">{</span><span class="ss">suspend</span><span class="p">,</span><span class="p" data-group-id="6464050063-46">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="6464050063-46">]</span><span class="p" data-group-id="6464050063-45">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-47">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="6464050063-48">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="6464050063-48">}</span><span class="p" data-group-id="6464050063-47">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-49">{</span><span class="ss">code_change</span><span class="p">,</span><span class="ss">down</span><span class="p">,</span><span class="p" data-group-id="6464050063-50">[</span><span class="p" data-group-id="6464050063-51">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="p" data-group-id="6464050063-52">[</span><span class="p" data-group-id="6464050063-52">]</span><span class="p" data-group-id="6464050063-51">}</span><span class="p" data-group-id="6464050063-50">]</span><span class="p" data-group-id="6464050063-49">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-53">{</span><span class="ss">resume</span><span class="p">,</span><span class="p" data-group-id="6464050063-54">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="6464050063-54">]</span><span class="p" data-group-id="6464050063-53">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-55">{</span><span class="ss">remove</span><span class="p">,</span><span class="p" data-group-id="6464050063-56">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="6464050063-56">}</span><span class="p" data-group-id="6464050063-55">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-57">{</span><span class="ss">remove</span><span class="p">,</span><span class="p" data-group-id="6464050063-58">{</span><span class="ss">ch3</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="6464050063-58">}</span><span class="p" data-group-id="6464050063-57">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-59">{</span><span class="ss">purge</span><span class="p">,</span><span class="p" data-group-id="6464050063-60">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">ch3</span><span class="p" data-group-id="6464050063-60">]</span><span class="p" data-group-id="6464050063-59">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6464050063-61">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="6464050063-62">{</span><span class="ss">application</span><span class="p">,</span><span class="ss">unload</span><span class="p">,</span><span class="p" data-group-id="6464050063-63">[</span><span class="ss">ch_app</span><span class="p" data-group-id="6464050063-63">]</span><span class="p" data-group-id="6464050063-62">}</span><span class="p" data-group-id="6464050063-61">}</span><span class="p" data-group-id="6464050063-35">]</span><span class="p" data-group-id="6464050063-33">}</span><span class="p" data-group-id="6464050063-32">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6464050063-1">}</span><span class="p">.</span></code></pre><h2 id="changing-non-erlang-code" class="section-heading">
│ │ │ │    <a href="#changing-non-erlang-code" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing Non-Erlang Code</span>
│ │ │ │  </h2>
│ │ │ │  <p>Changing code for a program written in another programming language than Erlang,
│ │ │ │  for example, a port program, is application-dependent and OTP provides no
│ │ │ │  special support.</p><p><em>Example</em></p><p>When changing code for a port program, assume that the Erlang process
│ │ │ │  controlling the port is a <code class="inline">gen_server</code> <code class="inline">portc</code> and that the port is opened in
│ │ │ │ -the callback function <code class="inline">init/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="8299977404-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8299977404-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +the callback function <code class="inline">init/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="6433256725-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6433256725-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">PortPrg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="8299977404-2">(</span><span class="nc">code</span><span class="p">:</span><span class="nf">priv_dir</span><span class="p" data-group-id="8299977404-3">(</span><span class="n">App</span><span class="p" data-group-id="8299977404-3">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;portc&quot;</span><span class="p" data-group-id="8299977404-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="8299977404-4">(</span><span class="p" data-group-id="8299977404-5">{</span><span class="nb">spawn</span><span class="p">,</span><span class="n">PortPrg</span><span class="p" data-group-id="8299977404-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8299977404-6">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8299977404-6">]</span><span class="p" data-group-id="8299977404-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">PortPrg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="6433256725-2">(</span><span class="nc">code</span><span class="p">:</span><span class="nf">priv_dir</span><span class="p" data-group-id="6433256725-3">(</span><span class="n">App</span><span class="p" data-group-id="6433256725-3">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;portc&quot;</span><span class="p" data-group-id="6433256725-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="6433256725-4">(</span><span class="p" data-group-id="6433256725-5">{</span><span class="nb">spawn</span><span class="p">,</span><span class="n">PortPrg</span><span class="p" data-group-id="6433256725-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6433256725-6">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6433256725-6">]</span><span class="p" data-group-id="6433256725-4">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8299977404-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="8299977404-8">{</span><span class="ss">port</span><span class="o">=</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8299977404-8">}</span><span class="p" data-group-id="8299977404-7">}</span><span class="p">.</span></code></pre><p>If the port program is to be updated, the code for the <code class="inline">gen_server</code> can be
│ │ │ │ +    </span><span class="p" data-group-id="6433256725-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="6433256725-8">{</span><span class="ss">port</span><span class="o">=</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6433256725-8">}</span><span class="p" data-group-id="6433256725-7">}</span><span class="p">.</span></code></pre><p>If the port program is to be updated, the code for the <code class="inline">gen_server</code> can be
│ │ │ │  extended with a <code class="inline">code_change/3</code> function, which closes the old port and opens a
│ │ │ │  new port. (If necessary, the <code class="inline">gen_server</code> can first request data that must be
│ │ │ │ -saved from the port program and pass this data to the new port):</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="1082806742-1">(</span><span class="p">_</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="ss">port</span><span class="p" data-group-id="1082806742-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +saved from the port program and pass this data to the new port):</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="7224184020-1">(</span><span class="p">_</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="ss">port</span><span class="p" data-group-id="7224184020-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">close</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1082806742-2">{</span><span class="n">Port</span><span class="p">,</span><span class="ss">close</span><span class="p" data-group-id="1082806742-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="7224184020-2">{</span><span class="n">Port</span><span class="p">,</span><span class="ss">close</span><span class="p" data-group-id="7224184020-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">PortPrg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1082806742-3">(</span><span class="nc">code</span><span class="p">:</span><span class="nf">priv_dir</span><span class="p" data-group-id="1082806742-4">(</span><span class="n">App</span><span class="p" data-group-id="1082806742-4">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;portc&quot;</span><span class="p" data-group-id="1082806742-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="1082806742-5">(</span><span class="p" data-group-id="1082806742-6">{</span><span class="nb">spawn</span><span class="p">,</span><span class="n">PortPrg</span><span class="p" data-group-id="1082806742-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1082806742-7">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1082806742-7">]</span><span class="p" data-group-id="1082806742-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1082806742-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="1082806742-9">{</span><span class="ss">port</span><span class="o">=</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1082806742-9">}</span><span class="p" data-group-id="1082806742-8">}</span><span class="p">.</span></code></pre><p>Update the application version number in the <code class="inline">.app</code> file and write an <code class="inline">.appup</code>
│ │ │ │ -file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4763536993-1">[</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4763536993-2">[</span><span class="p" data-group-id="4763536993-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4763536993-4">[</span><span class="p" data-group-id="4763536993-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">portc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4763536993-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="ss">port</span><span class="p" data-group-id="4763536993-6">}</span><span class="p" data-group-id="4763536993-5">}</span><span class="p" data-group-id="4763536993-4">]</span><span class="p" data-group-id="4763536993-3">}</span><span class="p" data-group-id="4763536993-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4763536993-7">[</span><span class="p" data-group-id="4763536993-8">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4763536993-9">[</span><span class="p" data-group-id="4763536993-10">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">portc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4763536993-11">{</span><span class="ss">advanced</span><span class="p">,</span><span class="ss">port</span><span class="p" data-group-id="4763536993-11">}</span><span class="p" data-group-id="4763536993-10">}</span><span class="p" data-group-id="4763536993-9">]</span><span class="p" data-group-id="4763536993-8">}</span><span class="p" data-group-id="4763536993-7">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4763536993-1">]</span><span class="p">.</span></code></pre><p>Ensure that the <code class="inline">priv</code> directory, where the C program is located, is included in
│ │ │ │ -the new release package:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="8078957253-1">(</span><span class="s">&quot;my_release&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8078957253-2">[</span><span class="p" data-group-id="8078957253-3">{</span><span class="ss">dirs</span><span class="p">,</span><span class="p" data-group-id="8078957253-4">[</span><span class="ss">priv</span><span class="p" data-group-id="8078957253-4">]</span><span class="p" data-group-id="8078957253-3">}</span><span class="p" data-group-id="8078957253-2">]</span><span class="p" data-group-id="8078957253-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="n">PortPrg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7224184020-3">(</span><span class="nc">code</span><span class="p">:</span><span class="nf">priv_dir</span><span class="p" data-group-id="7224184020-4">(</span><span class="n">App</span><span class="p" data-group-id="7224184020-4">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;portc&quot;</span><span class="p" data-group-id="7224184020-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="7224184020-5">(</span><span class="p" data-group-id="7224184020-6">{</span><span class="nb">spawn</span><span class="p">,</span><span class="n">PortPrg</span><span class="p" data-group-id="7224184020-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7224184020-7">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7224184020-7">]</span><span class="p" data-group-id="7224184020-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7224184020-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="7224184020-9">{</span><span class="ss">port</span><span class="o">=</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7224184020-9">}</span><span class="p" data-group-id="7224184020-8">}</span><span class="p">.</span></code></pre><p>Update the application version number in the <code class="inline">.app</code> file and write an <code class="inline">.appup</code>
│ │ │ │ +file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9800133702-1">[</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9800133702-2">[</span><span class="p" data-group-id="9800133702-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9800133702-4">[</span><span class="p" data-group-id="9800133702-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">portc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9800133702-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="ss">port</span><span class="p" data-group-id="9800133702-6">}</span><span class="p" data-group-id="9800133702-5">}</span><span class="p" data-group-id="9800133702-4">]</span><span class="p" data-group-id="9800133702-3">}</span><span class="p" data-group-id="9800133702-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9800133702-7">[</span><span class="p" data-group-id="9800133702-8">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9800133702-9">[</span><span class="p" data-group-id="9800133702-10">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">portc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9800133702-11">{</span><span class="ss">advanced</span><span class="p">,</span><span class="ss">port</span><span class="p" data-group-id="9800133702-11">}</span><span class="p" data-group-id="9800133702-10">}</span><span class="p" data-group-id="9800133702-9">]</span><span class="p" data-group-id="9800133702-8">}</span><span class="p" data-group-id="9800133702-7">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9800133702-1">]</span><span class="p">.</span></code></pre><p>Ensure that the <code class="inline">priv</code> directory, where the C program is located, is included in
│ │ │ │ +the new release package:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="5184304846-1">(</span><span class="s">&quot;my_release&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5184304846-2">[</span><span class="p" data-group-id="5184304846-3">{</span><span class="ss">dirs</span><span class="p">,</span><span class="p" data-group-id="5184304846-4">[</span><span class="ss">priv</span><span class="p" data-group-id="5184304846-4">]</span><span class="p" data-group-id="5184304846-3">}</span><span class="p" data-group-id="5184304846-2">]</span><span class="p" data-group-id="5184304846-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="runtime-system-restart-and-upgrade" class="section-heading">
│ │ │ │    <a href="#runtime-system-restart-and-upgrade" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Runtime System Restart and Upgrade</span>
│ │ │ │  </h2>
│ │ │ │  <p>Two upgrade instructions restart the runtime system:</p><ul><li><p><code class="inline">restart_new_emulator</code></p><p>Intended when ERTS, Kernel, STDLIB, or SASL is upgraded. It is automatically
│ │ │ │ @@ -461,20 +461,20 @@
│ │ │ │  executed before all other upgrade instructions. For more information about
│ │ │ │  this instruction, see restart_new_emulator (Low-Level) in
│ │ │ │  <a href="release_handling.xhtml#restart_new_emulator_instr">Release Handling Instructions</a>.</p></li><li><p><code class="inline">restart_emulator</code></p><p>Used when a restart of the runtime system is required after all other upgrade
│ │ │ │  instructions are executed. For more information about this instruction, see
│ │ │ │  restart_emulator (Low-Level) in
│ │ │ │  <a href="release_handling.xhtml#restart_emulator_instr">Release Handling Instructions</a>.</p></li></ul><p>If a runtime system restart is necessary and no upgrade instructions are needed,
│ │ │ │  that is, if the restart itself is enough for the upgraded applications to start
│ │ │ │ -running the new versions, a simple <code class="inline">.relup</code> file can be created manually:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3190846541-1">{</span><span class="s">&quot;B&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3190846541-2">[</span><span class="p" data-group-id="3190846541-3">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="3190846541-4">[</span><span class="p" data-group-id="3190846541-4">]</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="3190846541-5">[</span><span class="ss">restart_emulator</span><span class="p" data-group-id="3190846541-5">]</span><span class="p" data-group-id="3190846541-3">}</span><span class="p" data-group-id="3190846541-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3190846541-6">[</span><span class="p" data-group-id="3190846541-7">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="3190846541-8">[</span><span class="p" data-group-id="3190846541-8">]</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="3190846541-9">[</span><span class="ss">restart_emulator</span><span class="p" data-group-id="3190846541-9">]</span><span class="p" data-group-id="3190846541-7">}</span><span class="p" data-group-id="3190846541-6">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3190846541-1">}</span><span class="p">.</span></code></pre><p>In this case, the release handler framework with automatic packing and unpacking
│ │ │ │ +running the new versions, a simple <code class="inline">.relup</code> file can be created manually:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4166145699-1">{</span><span class="s">&quot;B&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="4166145699-2">[</span><span class="p" data-group-id="4166145699-3">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="4166145699-4">[</span><span class="p" data-group-id="4166145699-4">]</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="4166145699-5">[</span><span class="ss">restart_emulator</span><span class="p" data-group-id="4166145699-5">]</span><span class="p" data-group-id="4166145699-3">}</span><span class="p" data-group-id="4166145699-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="4166145699-6">[</span><span class="p" data-group-id="4166145699-7">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="4166145699-8">[</span><span class="p" data-group-id="4166145699-8">]</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="4166145699-9">[</span><span class="ss">restart_emulator</span><span class="p" data-group-id="4166145699-9">]</span><span class="p" data-group-id="4166145699-7">}</span><span class="p" data-group-id="4166145699-6">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4166145699-1">}</span><span class="p">.</span></code></pre><p>In this case, the release handler framework with automatic packing and unpacking
│ │ │ │  of release packages, automatic path updates, and so on, can be used without
│ │ │ │  having to specify <code class="inline">.appup</code> files.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/applications.xhtml
│ │ │ │ @@ -40,34 +40,34 @@
│ │ │ │  <a href="applications.xhtml#app_dir">directory structure</a>.</p><p><a href="" id="callback_module"></a></p><h2 id="application-callback-module" class="section-heading">
│ │ │ │    <a href="#application-callback-module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Application Callback Module</span>
│ │ │ │  </h2>
│ │ │ │  <p>How to start and stop the code for the application, including its supervision
│ │ │ │ -tree, is described by two callback functions:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start</span><span class="p" data-group-id="1410471072-1">(</span><span class="n">StartType</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="1410471072-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1410471072-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="1410471072-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="1410471072-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="1410471072-3">}</span><span class="w">
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="1410471072-4">(</span><span class="n">State</span><span class="p" data-group-id="1410471072-4">)</span></code></pre><ul><li><code class="inline">start/2</code> is called when starting the application and is to create the
│ │ │ │ +tree, is described by two callback functions:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start</span><span class="p" data-group-id="5827566056-1">(</span><span class="n">StartType</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="5827566056-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5827566056-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="5827566056-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="5827566056-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5827566056-3">}</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="5827566056-4">(</span><span class="n">State</span><span class="p" data-group-id="5827566056-4">)</span></code></pre><ul><li><code class="inline">start/2</code> is called when starting the application and is to create the
│ │ │ │  supervision tree by starting the top supervisor. It is expected to return the
│ │ │ │  pid of the top supervisor and an optional term, <code class="inline">State</code>, which defaults to
│ │ │ │  <code class="inline">[]</code>. This term is passed as is to <code class="inline">stop/1</code>.</li><li><code class="inline">StartType</code> is usually the atom <code class="inline">normal</code>. It has other values only in the case
│ │ │ │  of a takeover or failover; see
│ │ │ │  <a href="distributed_applications.xhtml">Distributed Applications</a>.</li><li><code class="inline">StartArgs</code> is defined by the key <code class="inline">mod</code> in the
│ │ │ │  <a href="applications.xhtml#appl_res_file">application resource file</a>.</li><li><code class="inline">stop/1</code> is called <em>after</em> the application has been stopped and is to do any
│ │ │ │  necessary cleaning up. The actual stopping of the application, that is,
│ │ │ │  shutting down the supervision tree, is handled automatically as described in
│ │ │ │  <a href="applications.xhtml#stopping">Starting and Stopping Applications</a>.</li></ul><p><a href="" id="ch_app"></a></p><p>Example of an application callback module for packaging the supervision tree
│ │ │ │ -from <a href="sup_princ.xhtml#ex">Supervisor Behaviour</a>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0754628355-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="0754628355-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="0754628355-2">(</span><span class="ss">application</span><span class="p" data-group-id="0754628355-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +from <a href="sup_princ.xhtml#ex">Supervisor Behaviour</a>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0870590703-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="0870590703-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="0870590703-2">(</span><span class="ss">application</span><span class="p" data-group-id="0870590703-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0754628355-3">(</span><span class="p" data-group-id="0754628355-4">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0754628355-4">]</span><span class="p" data-group-id="0754628355-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0870590703-3">(</span><span class="p" data-group-id="0870590703-4">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0870590703-4">]</span><span class="p" data-group-id="0870590703-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="0754628355-5">(</span><span class="p">_</span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="0754628355-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">ch_sup</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="0754628355-6">(</span><span class="p" data-group-id="0754628355-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="0870590703-5">(</span><span class="p">_</span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="0870590703-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">ch_sup</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="0870590703-6">(</span><span class="p" data-group-id="0870590703-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="0754628355-7">(</span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="0754628355-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="0870590703-7">(</span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="0870590703-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>A library application that cannot be started or stopped does not need any
│ │ │ │  application callback module.</p><p><a href="" id="appl_res_file"></a></p><h2 id="application-resource-file" class="section-heading">
│ │ │ │    <a href="#application-resource-file" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Application Resource File</span>
│ │ │ │  </h2>
│ │ │ │ @@ -78,22 +78,22 @@
│ │ │ │  keys.</li></ul><p>The contents of a minimal <code class="inline">.app</code> file for a library application <code class="inline">libapp</code> looks
│ │ │ │  as follows:</p><pre><code class="text">{application, libapp, []}.</code></pre><p>The contents of a minimal <code class="inline">.app</code> file <code class="inline">ch_app.app</code> for a supervision tree
│ │ │ │  application like <code class="inline">ch_app</code> looks as follows:</p><pre><code class="text">{application, ch_app,
│ │ │ │   [{mod, {ch_app,[]}}]}.</code></pre><p>The key <code class="inline">mod</code> defines the callback module and start argument of the application,
│ │ │ │  in this case <code class="inline">ch_app</code> and <code class="inline">[]</code>, respectively. This means that the following is
│ │ │ │  called when the application is to be started:</p><pre><code class="text">ch_app:start(normal, [])</code></pre><p>The following is called when the application is stopped:</p><pre><code class="text">ch_app:stop([])</code></pre><p>When using <a href="../../../lib/sasl/doc/html/systools.html"><code class="inline">systools</code></a>, the Erlang/OTP tools for packaging code (see Section
│ │ │ │  <a href="release_structure.xhtml">Releases</a>), the keys <code class="inline">description</code>, <code class="inline">vsn</code>, <code class="inline">modules</code>,
│ │ │ │ -<code class="inline">registered</code>, and <code class="inline">applications</code> are also to be specified:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4742943957-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4742943957-2">[</span><span class="p" data-group-id="4742943957-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="4742943957-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="4742943957-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="4742943957-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="4742943957-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4742943957-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="4742943957-6">]</span><span class="p" data-group-id="4742943957-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="4742943957-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4742943957-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="4742943957-8">]</span><span class="p" data-group-id="4742943957-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="4742943957-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4742943957-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="4742943957-10">]</span><span class="p" data-group-id="4742943957-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="4742943957-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4742943957-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="4742943957-13">[</span><span class="p" data-group-id="4742943957-13">]</span><span class="p" data-group-id="4742943957-12">}</span><span class="p" data-group-id="4742943957-11">}</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4742943957-2">]</span><span class="p" data-group-id="4742943957-1">}</span><span class="p">.</span></code></pre><ul><li><code class="inline">description</code> - A short description, a string. Defaults to <code class="inline">&quot;&quot;</code>.</li><li><code class="inline">vsn</code> - Version number, a string. Defaults to <code class="inline">&quot;&quot;</code>.</li><li><code class="inline">modules</code> - All modules <em>introduced</em> by this application. <a href="../../../lib/sasl/doc/html/systools.html"><code class="inline">systools</code></a> uses
│ │ │ │ +<code class="inline">registered</code>, and <code class="inline">applications</code> are also to be specified:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3977441725-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="3977441725-2">[</span><span class="p" data-group-id="3977441725-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="3977441725-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="3977441725-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="3977441725-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="3977441725-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3977441725-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="3977441725-6">]</span><span class="p" data-group-id="3977441725-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="3977441725-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3977441725-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="3977441725-8">]</span><span class="p" data-group-id="3977441725-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="3977441725-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3977441725-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="3977441725-10">]</span><span class="p" data-group-id="3977441725-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="3977441725-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3977441725-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="3977441725-13">[</span><span class="p" data-group-id="3977441725-13">]</span><span class="p" data-group-id="3977441725-12">}</span><span class="p" data-group-id="3977441725-11">}</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="3977441725-2">]</span><span class="p" data-group-id="3977441725-1">}</span><span class="p">.</span></code></pre><ul><li><code class="inline">description</code> - A short description, a string. Defaults to <code class="inline">&quot;&quot;</code>.</li><li><code class="inline">vsn</code> - Version number, a string. Defaults to <code class="inline">&quot;&quot;</code>.</li><li><code class="inline">modules</code> - All modules <em>introduced</em> by this application. <a href="../../../lib/sasl/doc/html/systools.html"><code class="inline">systools</code></a> uses
│ │ │ │  this list when generating boot scripts and tar files. A module must only
│ │ │ │  be included in one application. Defaults to <code class="inline">[]</code>.</li><li><code class="inline">registered</code> - All names of registered processes in the application.
│ │ │ │  <a href="../../../lib/sasl/doc/html/systools.html"><code class="inline">systools</code></a> uses this list to detect name clashes between applications.
│ │ │ │  Defaults to <code class="inline">[]</code>.</li><li><code class="inline">applications</code> - All applications that must be started before this
│ │ │ │  application is started. <a href="../../../lib/sasl/doc/html/systools.html"><code class="inline">systools</code></a> uses this list to generate correct boot
│ │ │ │  scripts. Defaults to <code class="inline">[]</code>. Notice that all applications have dependencies to
│ │ │ │  at least Kernel and STDLIB.</li></ul><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>For details about the syntax and contents of the application resource file,
│ │ │ │ @@ -205,38 +205,38 @@
│ │ │ │  stop applications.</p><h2 id="loading-and-unloading-applications" class="section-heading">
│ │ │ │    <a href="#loading-and-unloading-applications" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Loading and Unloading Applications</span>
│ │ │ │  </h2>
│ │ │ │  <p>Before an application can be started, it must be <em>loaded</em>. The application
│ │ │ │ -controller reads and stores the information from the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">load</span><span class="p" data-group-id="9721460829-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="9721460829-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +controller reads and stores the information from the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">load</span><span class="p" data-group-id="0659046982-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="0659046982-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">loaded_applications</span><span class="p" data-group-id="9721460829-2">(</span><span class="p" data-group-id="9721460829-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9721460829-3">[</span><span class="p" data-group-id="9721460829-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="9721460829-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9721460829-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="9721460829-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9721460829-6">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;Channel allocator&quot;</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="9721460829-6">}</span><span class="p" data-group-id="9721460829-3">]</span></code></pre><p>An application that has been stopped, or has never been started, can be
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">loaded_applications</span><span class="p" data-group-id="0659046982-2">(</span><span class="p" data-group-id="0659046982-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0659046982-3">[</span><span class="p" data-group-id="0659046982-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="0659046982-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0659046982-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="0659046982-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0659046982-6">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;Channel allocator&quot;</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="0659046982-6">}</span><span class="p" data-group-id="0659046982-3">]</span></code></pre><p>An application that has been stopped, or has never been started, can be
│ │ │ │  unloaded. The information about the application is erased from the internal
│ │ │ │ -database of the application controller.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">unload</span><span class="p" data-group-id="8828554883-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="8828554883-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +database of the application controller.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">unload</span><span class="p" data-group-id="6235367604-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="6235367604-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">loaded_applications</span><span class="p" data-group-id="8828554883-2">(</span><span class="p" data-group-id="8828554883-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8828554883-3">[</span><span class="p" data-group-id="8828554883-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="8828554883-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="8828554883-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="8828554883-5">}</span><span class="p" data-group-id="8828554883-3">]</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Loading/unloading an application does not load/unload the code used by the
│ │ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">loaded_applications</span><span class="p" data-group-id="6235367604-2">(</span><span class="p" data-group-id="6235367604-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6235367604-3">[</span><span class="p" data-group-id="6235367604-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="6235367604-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6235367604-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="6235367604-5">}</span><span class="p" data-group-id="6235367604-3">]</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Loading/unloading an application does not load/unload the code used by the
│ │ │ │  application. Code loading is handled in the usual way by the code server.</p></section><p><a href="" id="stopping"></a></p><h2 id="starting-and-stopping-applications" class="section-heading">
│ │ │ │    <a href="#starting-and-stopping-applications" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Starting and Stopping Applications</span>
│ │ │ │  </h2>
│ │ │ │ -<p>An application is started by calling:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="0696521547-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="0696521547-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>An application is started by calling:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8007576089-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="8007576089-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">which_applications</span><span class="p" data-group-id="0696521547-2">(</span><span class="p" data-group-id="0696521547-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0696521547-3">[</span><span class="p" data-group-id="0696521547-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="0696521547-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="0696521547-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="0696521547-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="0696521547-6">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;Channel allocator&quot;</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="0696521547-6">}</span><span class="p" data-group-id="0696521547-3">]</span></code></pre><p>If the application is not already loaded, the application controller first loads
│ │ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">which_applications</span><span class="p" data-group-id="8007576089-2">(</span><span class="p" data-group-id="8007576089-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8007576089-3">[</span><span class="p" data-group-id="8007576089-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="8007576089-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8007576089-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="8007576089-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8007576089-6">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;Channel allocator&quot;</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="8007576089-6">}</span><span class="p" data-group-id="8007576089-3">]</span></code></pre><p>If the application is not already loaded, the application controller first loads
│ │ │ │  it using <a href="../../../lib/kernel/doc/html/application.html#load/1"><code class="inline">application:load/1</code></a>. It checks the value of the <code class="inline">applications</code> key to
│ │ │ │  ensure that all applications that are to be started before this application are
│ │ │ │  running.</p><p><a href="" id="application_master"></a></p><p>Following that, the application controller creates an <em>application master</em> for
│ │ │ │  the application.</p><p>The application master establishes itself as the <a href="../../../lib/../erts/doc/html/erlang.html#group_leader/0">group
│ │ │ │  leader</a> of all processes in the application
│ │ │ │  and will forward I/O to the previous group leader.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The purpose of the application master being the group leader is to easily
│ │ │ │  keep track of which processes that belong to the application. That is needed
│ │ │ │ @@ -252,55 +252,55 @@
│ │ │ │  defined by the <code class="inline">mod</code> key.</p><h2 id="configuring-an-application" class="section-heading">
│ │ │ │    <a href="#configuring-an-application" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Configuring an Application</span>
│ │ │ │  </h2>
│ │ │ │  <p>An application can be configured using <em>configuration parameters</em>. These are a
│ │ │ │ -list of <code class="inline">{Par,Val}</code> tuples specified by a key <code class="inline">env</code> in the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8423345940-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="8423345940-2">[</span><span class="p" data-group-id="8423345940-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="8423345940-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="8423345940-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="8423345940-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="8423345940-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8423345940-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="8423345940-6">]</span><span class="p" data-group-id="8423345940-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="8423345940-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8423345940-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="8423345940-8">]</span><span class="p" data-group-id="8423345940-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="8423345940-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8423345940-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="8423345940-10">]</span><span class="p" data-group-id="8423345940-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="8423345940-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8423345940-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="8423345940-13">[</span><span class="p" data-group-id="8423345940-13">]</span><span class="p" data-group-id="8423345940-12">}</span><span class="p" data-group-id="8423345940-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="8423345940-14">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8423345940-15">[</span><span class="p" data-group-id="8423345940-16">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="8423345940-16">}</span><span class="p" data-group-id="8423345940-15">]</span><span class="p" data-group-id="8423345940-14">}</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="8423345940-2">]</span><span class="p" data-group-id="8423345940-1">}</span><span class="p">.</span></code></pre><p><code class="inline">Par</code> is to be an atom. <code class="inline">Val</code> is any term. The application can retrieve the
│ │ │ │ +list of <code class="inline">{Par,Val}</code> tuples specified by a key <code class="inline">env</code> in the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6873570935-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6873570935-2">[</span><span class="p" data-group-id="6873570935-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="6873570935-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6873570935-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="6873570935-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6873570935-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6873570935-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="6873570935-6">]</span><span class="p" data-group-id="6873570935-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6873570935-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6873570935-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="6873570935-8">]</span><span class="p" data-group-id="6873570935-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6873570935-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6873570935-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="6873570935-10">]</span><span class="p" data-group-id="6873570935-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6873570935-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6873570935-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="6873570935-13">[</span><span class="p" data-group-id="6873570935-13">]</span><span class="p" data-group-id="6873570935-12">}</span><span class="p" data-group-id="6873570935-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6873570935-14">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6873570935-15">[</span><span class="p" data-group-id="6873570935-16">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="6873570935-16">}</span><span class="p" data-group-id="6873570935-15">]</span><span class="p" data-group-id="6873570935-14">}</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6873570935-2">]</span><span class="p" data-group-id="6873570935-1">}</span><span class="p">.</span></code></pre><p><code class="inline">Par</code> is to be an atom. <code class="inline">Val</code> is any term. The application can retrieve the
│ │ │ │  value of a configuration parameter by calling <code class="inline">application:get_env(App, Par)</code> or
│ │ │ │  a number of similar functions. For more information, see module <a href="../../../lib/kernel/doc/html/application.html"><code class="inline">application</code></a>
│ │ │ │  in Kernel.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl</span><span class="w">
│ │ │ │ -</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="1693907045-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="1693907045-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="1693907045-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="1693907045-2">]</span><span class="w"> </span><span class="p" data-group-id="1693907045-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="1693907045-3">]</span><span class="w">
│ │ │ │ +</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="6770459347-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="6770459347-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="6770459347-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="6770459347-2">]</span><span class="w"> </span><span class="p" data-group-id="6770459347-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="6770459347-3">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="1693907045-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="1693907045-4">)</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1693907045-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="1693907045-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="6770459347-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="6770459347-4">)</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="6770459347-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="6770459347-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="1693907045-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="1693907045-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1693907045-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="1693907045-7">}</span></code></pre><p>The values in the <code class="inline">.app</code> file can be overridden by values in a <em>system
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="6770459347-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="6770459347-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6770459347-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="6770459347-7">}</span></code></pre><p>The values in the <code class="inline">.app</code> file can be overridden by values in a <em>system
│ │ │ │  configuration file</em>. This is a file that contains configuration parameters for
│ │ │ │ -relevant applications:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7847698092-1">[</span><span class="p" data-group-id="7847698092-2">{</span><span class="n">Application1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7847698092-3">[</span><span class="p" data-group-id="7847698092-4">{</span><span class="n">Par11</span><span class="p">,</span><span class="n">Val11</span><span class="p" data-group-id="7847698092-4">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7847698092-3">]</span><span class="p" data-group-id="7847698092-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +relevant applications:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1429101672-1">[</span><span class="p" data-group-id="1429101672-2">{</span><span class="n">Application1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1429101672-3">[</span><span class="p" data-group-id="1429101672-4">{</span><span class="n">Par11</span><span class="p">,</span><span class="n">Val11</span><span class="p" data-group-id="1429101672-4">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1429101672-3">]</span><span class="p" data-group-id="1429101672-2">}</span><span class="p">,</span><span class="w">
│ │ │ │   </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7847698092-5">{</span><span class="n">ApplicationN</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7847698092-6">[</span><span class="p" data-group-id="7847698092-7">{</span><span class="n">ParN1</span><span class="p">,</span><span class="n">ValN1</span><span class="p" data-group-id="7847698092-7">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7847698092-6">]</span><span class="p" data-group-id="7847698092-5">}</span><span class="p" data-group-id="7847698092-1">]</span><span class="p">.</span></code></pre><p>The system configuration is to be called <code class="inline">Name.config</code> and Erlang is to be
│ │ │ │ + </span><span class="p" data-group-id="1429101672-5">{</span><span class="n">ApplicationN</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1429101672-6">[</span><span class="p" data-group-id="1429101672-7">{</span><span class="n">ParN1</span><span class="p">,</span><span class="n">ValN1</span><span class="p" data-group-id="1429101672-7">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1429101672-6">]</span><span class="p" data-group-id="1429101672-5">}</span><span class="p" data-group-id="1429101672-1">]</span><span class="p">.</span></code></pre><p>The system configuration is to be called <code class="inline">Name.config</code> and Erlang is to be
│ │ │ │  started with the command-line argument <code class="inline">-config Name</code>. For details, see
│ │ │ │  <a href="../../../lib/kernel/doc/html/config.xhtml"><code class="inline">config</code></a> in Kernel.</p><p><em>Example:</em></p><p>A file <code class="inline">test.config</code> is created with the following contents:</p><pre><code class="text">[{ch_app, [{file, &quot;testlog&quot;}]}].</code></pre><p>The value of <code class="inline">file</code> overrides the value of <code class="inline">file</code> as defined in the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -config test</span><span class="w">
│ │ │ │ -</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="2897333074-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="2897333074-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="2897333074-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="2897333074-2">]</span><span class="w"> </span><span class="p" data-group-id="2897333074-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="2897333074-3">]</span><span class="w">
│ │ │ │ +</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="1024054085-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="1024054085-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="1024054085-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="1024054085-2">]</span><span class="w"> </span><span class="p" data-group-id="1024054085-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="1024054085-3">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="2897333074-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="2897333074-4">)</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2897333074-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="2897333074-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="1024054085-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="1024054085-4">)</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1024054085-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="1024054085-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="2897333074-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="2897333074-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2897333074-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;testlog&quot;</span><span class="p" data-group-id="2897333074-7">}</span></code></pre><p>If <a href="release_handling.xhtml#sys">release handling</a> is used, exactly one system
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="1024054085-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="1024054085-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1024054085-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;testlog&quot;</span><span class="p" data-group-id="1024054085-7">}</span></code></pre><p>If <a href="release_handling.xhtml#sys">release handling</a> is used, exactly one system
│ │ │ │  configuration file is to be used and that file is to be called <code class="inline">sys.config</code>.</p><p>The values in the <code class="inline">.app</code> file and the values in a system configuration file can
│ │ │ │  be overridden directly from the command line:</p><pre><code class="text">% erl -ApplName Par1 Val1 ... ParN ValN</code></pre><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -ch_app file &#39;&quot;testlog&quot;&#39;</span><span class="w">
│ │ │ │ -</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="3418166311-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="3418166311-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="3418166311-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="3418166311-2">]</span><span class="w"> </span><span class="p" data-group-id="3418166311-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="3418166311-3">]</span><span class="w">
│ │ │ │ +</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="9292381078-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="9292381078-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="9292381078-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="9292381078-2">]</span><span class="w"> </span><span class="p" data-group-id="9292381078-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="9292381078-3">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="3418166311-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="3418166311-4">)</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="3418166311-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="3418166311-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="9292381078-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="9292381078-4">)</span><span class="w">
│ │ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="9292381078-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="9292381078-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="3418166311-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="3418166311-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3418166311-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;testlog&quot;</span><span class="p" data-group-id="3418166311-7">}</span></code></pre><h2 id="application-start-types" class="section-heading">
│ │ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="9292381078-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="9292381078-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9292381078-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;testlog&quot;</span><span class="p" data-group-id="9292381078-7">}</span></code></pre><h2 id="application-start-types" class="section-heading">
│ │ │ │    <a href="#application-start-types" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Application Start Types</span>
│ │ │ │  </h2>
│ │ │ │  <p>A <em>start type</em> is defined when starting the application:</p><pre><code class="text">application:start(Application, Type)</code></pre><p><code class="inline">application:start(Application)</code> is the same as calling
│ │ │ │  <code class="inline">application:start(Application, temporary)</code>. The type can also be <code class="inline">permanent</code> or
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/applications.html
│ │ │ @@ -135,34 +135,34 @@
│ │ │  <a href="applications.html#app_dir">directory structure</a>.</p><p><a href="" id="callback_module"></a></p><h2 id="application-callback-module" class="section-heading">
│ │ │    <a href="#application-callback-module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Application Callback Module</span>
│ │ │  </h2>
│ │ │  <p>How to start and stop the code for the application, including its supervision
│ │ │ -tree, is described by two callback functions:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start</span><span class="p" data-group-id="0529488867-1">(</span><span class="n">StartType</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="0529488867-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0529488867-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="0529488867-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="0529488867-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0529488867-3">}</span><span class="w">
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="0529488867-4">(</span><span class="n">State</span><span class="p" data-group-id="0529488867-4">)</span></code></pre><ul><li><code class="inline">start/2</code> is called when starting the application and is to create the
│ │ │ +tree, is described by two callback functions:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start</span><span class="p" data-group-id="2823094530-1">(</span><span class="n">StartType</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="2823094530-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2823094530-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="2823094530-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="2823094530-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2823094530-3">}</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="2823094530-4">(</span><span class="n">State</span><span class="p" data-group-id="2823094530-4">)</span></code></pre><ul><li><code class="inline">start/2</code> is called when starting the application and is to create the
│ │ │  supervision tree by starting the top supervisor. It is expected to return the
│ │ │  pid of the top supervisor and an optional term, <code class="inline">State</code>, which defaults to
│ │ │  <code class="inline">[]</code>. This term is passed as is to <code class="inline">stop/1</code>.</li><li><code class="inline">StartType</code> is usually the atom <code class="inline">normal</code>. It has other values only in the case
│ │ │  of a takeover or failover; see
│ │ │  <a href="distributed_applications.html">Distributed Applications</a>.</li><li><code class="inline">StartArgs</code> is defined by the key <code class="inline">mod</code> in the
│ │ │  <a href="applications.html#appl_res_file">application resource file</a>.</li><li><code class="inline">stop/1</code> is called <em>after</em> the application has been stopped and is to do any
│ │ │  necessary cleaning up. The actual stopping of the application, that is,
│ │ │  shutting down the supervision tree, is handled automatically as described in
│ │ │  <a href="applications.html#stopping">Starting and Stopping Applications</a>.</li></ul><p><a href="" id="ch_app"></a></p><p>Example of an application callback module for packaging the supervision tree
│ │ │ -from <a href="sup_princ.html#ex">Supervisor Behaviour</a>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2353460645-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="2353460645-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="2353460645-2">(</span><span class="ss">application</span><span class="p" data-group-id="2353460645-2">)</span><span class="p">.</span><span class="w">
│ │ │ +from <a href="sup_princ.html#ex">Supervisor Behaviour</a>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6710893757-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="6710893757-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="6710893757-2">(</span><span class="ss">application</span><span class="p" data-group-id="6710893757-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2353460645-3">(</span><span class="p" data-group-id="2353460645-4">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2353460645-4">]</span><span class="p" data-group-id="2353460645-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6710893757-3">(</span><span class="p" data-group-id="6710893757-4">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6710893757-4">]</span><span class="p" data-group-id="6710893757-3">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="2353460645-5">(</span><span class="p">_</span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="2353460645-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">ch_sup</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="2353460645-6">(</span><span class="p" data-group-id="2353460645-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="6710893757-5">(</span><span class="p">_</span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="6710893757-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">ch_sup</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="6710893757-6">(</span><span class="p" data-group-id="6710893757-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="2353460645-7">(</span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="2353460645-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="6710893757-7">(</span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="6710893757-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>A library application that cannot be started or stopped does not need any
│ │ │  application callback module.</p><p><a href="" id="appl_res_file"></a></p><h2 id="application-resource-file" class="section-heading">
│ │ │    <a href="#application-resource-file" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Application Resource File</span>
│ │ │  </h2>
│ │ │ @@ -173,22 +173,22 @@
│ │ │  keys.</li></ul><p>The contents of a minimal <code class="inline">.app</code> file for a library application <code class="inline">libapp</code> looks
│ │ │  as follows:</p><pre><code class="text">{application, libapp, []}.</code></pre><p>The contents of a minimal <code class="inline">.app</code> file <code class="inline">ch_app.app</code> for a supervision tree
│ │ │  application like <code class="inline">ch_app</code> looks as follows:</p><pre><code class="text">{application, ch_app,
│ │ │   [{mod, {ch_app,[]}}]}.</code></pre><p>The key <code class="inline">mod</code> defines the callback module and start argument of the application,
│ │ │  in this case <code class="inline">ch_app</code> and <code class="inline">[]</code>, respectively. This means that the following is
│ │ │  called when the application is to be started:</p><pre><code class="text">ch_app:start(normal, [])</code></pre><p>The following is called when the application is stopped:</p><pre><code class="text">ch_app:stop([])</code></pre><p>When using <a href="../../lib/sasl-4.4/doc/html/systools.html"><code class="inline">systools</code></a>, the Erlang/OTP tools for packaging code (see Section
│ │ │  <a href="release_structure.html">Releases</a>), the keys <code class="inline">description</code>, <code class="inline">vsn</code>, <code class="inline">modules</code>,
│ │ │ -<code class="inline">registered</code>, and <code class="inline">applications</code> are also to be specified:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5957670995-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5957670995-2">[</span><span class="p" data-group-id="5957670995-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="5957670995-3">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5957670995-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="5957670995-4">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5957670995-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5957670995-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="5957670995-6">]</span><span class="p" data-group-id="5957670995-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5957670995-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5957670995-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="5957670995-8">]</span><span class="p" data-group-id="5957670995-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5957670995-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5957670995-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="5957670995-10">]</span><span class="p" data-group-id="5957670995-9">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5957670995-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5957670995-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="5957670995-13">[</span><span class="p" data-group-id="5957670995-13">]</span><span class="p" data-group-id="5957670995-12">}</span><span class="p" data-group-id="5957670995-11">}</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5957670995-2">]</span><span class="p" data-group-id="5957670995-1">}</span><span class="p">.</span></code></pre><ul><li><code class="inline">description</code> - A short description, a string. Defaults to <code class="inline">&quot;&quot;</code>.</li><li><code class="inline">vsn</code> - Version number, a string. Defaults to <code class="inline">&quot;&quot;</code>.</li><li><code class="inline">modules</code> - All modules <em>introduced</em> by this application. <a href="../../lib/sasl-4.4/doc/html/systools.html"><code class="inline">systools</code></a> uses
│ │ │ +<code class="inline">registered</code>, and <code class="inline">applications</code> are also to be specified:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8633086089-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8633086089-2">[</span><span class="p" data-group-id="8633086089-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="8633086089-3">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8633086089-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="8633086089-4">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8633086089-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8633086089-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="8633086089-6">]</span><span class="p" data-group-id="8633086089-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8633086089-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8633086089-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="8633086089-8">]</span><span class="p" data-group-id="8633086089-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8633086089-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8633086089-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="8633086089-10">]</span><span class="p" data-group-id="8633086089-9">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8633086089-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8633086089-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="8633086089-13">[</span><span class="p" data-group-id="8633086089-13">]</span><span class="p" data-group-id="8633086089-12">}</span><span class="p" data-group-id="8633086089-11">}</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8633086089-2">]</span><span class="p" data-group-id="8633086089-1">}</span><span class="p">.</span></code></pre><ul><li><code class="inline">description</code> - A short description, a string. Defaults to <code class="inline">&quot;&quot;</code>.</li><li><code class="inline">vsn</code> - Version number, a string. Defaults to <code class="inline">&quot;&quot;</code>.</li><li><code class="inline">modules</code> - All modules <em>introduced</em> by this application. <a href="../../lib/sasl-4.4/doc/html/systools.html"><code class="inline">systools</code></a> uses
│ │ │  this list when generating boot scripts and tar files. A module must only
│ │ │  be included in one application. Defaults to <code class="inline">[]</code>.</li><li><code class="inline">registered</code> - All names of registered processes in the application.
│ │ │  <a href="../../lib/sasl-4.4/doc/html/systools.html"><code class="inline">systools</code></a> uses this list to detect name clashes between applications.
│ │ │  Defaults to <code class="inline">[]</code>.</li><li><code class="inline">applications</code> - All applications that must be started before this
│ │ │  application is started. <a href="../../lib/sasl-4.4/doc/html/systools.html"><code class="inline">systools</code></a> uses this list to generate correct boot
│ │ │  scripts. Defaults to <code class="inline">[]</code>. Notice that all applications have dependencies to
│ │ │  at least Kernel and STDLIB.</li></ul><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>For details about the syntax and contents of the application resource file,
│ │ │ @@ -300,38 +300,38 @@
│ │ │  stop applications.</p><h2 id="loading-and-unloading-applications" class="section-heading">
│ │ │    <a href="#loading-and-unloading-applications" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Loading and Unloading Applications</span>
│ │ │  </h2>
│ │ │  <p>Before an application can be started, it must be <em>loaded</em>. The application
│ │ │ -controller reads and stores the information from the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">load</span><span class="p" data-group-id="0443191314-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="0443191314-1">)</span><span class="p">.</span><span class="w">
│ │ │ +controller reads and stores the information from the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">load</span><span class="p" data-group-id="2044982855-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="2044982855-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">loaded_applications</span><span class="p" data-group-id="0443191314-2">(</span><span class="p" data-group-id="0443191314-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0443191314-3">[</span><span class="p" data-group-id="0443191314-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="0443191314-4">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0443191314-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="0443191314-5">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0443191314-6">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;Channel allocator&quot;</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="0443191314-6">}</span><span class="p" data-group-id="0443191314-3">]</span></code></pre><p>An application that has been stopped, or has never been started, can be
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">loaded_applications</span><span class="p" data-group-id="2044982855-2">(</span><span class="p" data-group-id="2044982855-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2044982855-3">[</span><span class="p" data-group-id="2044982855-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="2044982855-4">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="2044982855-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="2044982855-5">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="2044982855-6">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;Channel allocator&quot;</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="2044982855-6">}</span><span class="p" data-group-id="2044982855-3">]</span></code></pre><p>An application that has been stopped, or has never been started, can be
│ │ │  unloaded. The information about the application is erased from the internal
│ │ │ -database of the application controller.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">unload</span><span class="p" data-group-id="2662464636-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="2662464636-1">)</span><span class="p">.</span><span class="w">
│ │ │ +database of the application controller.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">unload</span><span class="p" data-group-id="6167802046-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="6167802046-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">loaded_applications</span><span class="p" data-group-id="2662464636-2">(</span><span class="p" data-group-id="2662464636-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2662464636-3">[</span><span class="p" data-group-id="2662464636-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="2662464636-4">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="2662464636-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="2662464636-5">}</span><span class="p" data-group-id="2662464636-3">]</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Loading/unloading an application does not load/unload the code used by the
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">loaded_applications</span><span class="p" data-group-id="6167802046-2">(</span><span class="p" data-group-id="6167802046-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6167802046-3">[</span><span class="p" data-group-id="6167802046-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="6167802046-4">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="6167802046-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="6167802046-5">}</span><span class="p" data-group-id="6167802046-3">]</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Loading/unloading an application does not load/unload the code used by the
│ │ │  application. Code loading is handled in the usual way by the code server.</p></section><p><a href="" id="stopping"></a></p><h2 id="starting-and-stopping-applications" class="section-heading">
│ │ │    <a href="#starting-and-stopping-applications" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Starting and Stopping Applications</span>
│ │ │  </h2>
│ │ │ -<p>An application is started by calling:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="4818868161-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="4818868161-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>An application is started by calling:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1273677284-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="1273677284-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">which_applications</span><span class="p" data-group-id="4818868161-2">(</span><span class="p" data-group-id="4818868161-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4818868161-3">[</span><span class="p" data-group-id="4818868161-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="4818868161-4">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="4818868161-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="4818868161-5">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="4818868161-6">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;Channel allocator&quot;</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="4818868161-6">}</span><span class="p" data-group-id="4818868161-3">]</span></code></pre><p>If the application is not already loaded, the application controller first loads
│ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">which_applications</span><span class="p" data-group-id="1273677284-2">(</span><span class="p" data-group-id="1273677284-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1273677284-3">[</span><span class="p" data-group-id="1273677284-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="1273677284-4">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="1273677284-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="1273677284-5">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="1273677284-6">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;Channel allocator&quot;</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="1273677284-6">}</span><span class="p" data-group-id="1273677284-3">]</span></code></pre><p>If the application is not already loaded, the application controller first loads
│ │ │  it using <a href="../../lib/kernel-11.0/doc/html/application.html#load/1"><code class="inline">application:load/1</code></a>. It checks the value of the <code class="inline">applications</code> key to
│ │ │  ensure that all applications that are to be started before this application are
│ │ │  running.</p><p><a href="" id="application_master"></a></p><p>Following that, the application controller creates an <em>application master</em> for
│ │ │  the application.</p><p>The application master establishes itself as the <a href="../../erts-17.0/doc/html/erlang.html#group_leader/0">group
│ │ │  leader</a> of all processes in the application
│ │ │  and will forward I/O to the previous group leader.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The purpose of the application master being the group leader is to easily
│ │ │  keep track of which processes that belong to the application. That is needed
│ │ │ @@ -347,55 +347,55 @@
│ │ │  defined by the <code class="inline">mod</code> key.</p><h2 id="configuring-an-application" class="section-heading">
│ │ │    <a href="#configuring-an-application" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Configuring an Application</span>
│ │ │  </h2>
│ │ │  <p>An application can be configured using <em>configuration parameters</em>. These are a
│ │ │ -list of <code class="inline">{Par,Val}</code> tuples specified by a key <code class="inline">env</code> in the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6552663310-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="6552663310-2">[</span><span class="p" data-group-id="6552663310-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="6552663310-3">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="6552663310-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="6552663310-4">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="6552663310-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6552663310-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="6552663310-6">]</span><span class="p" data-group-id="6552663310-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="6552663310-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6552663310-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="6552663310-8">]</span><span class="p" data-group-id="6552663310-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="6552663310-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6552663310-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="6552663310-10">]</span><span class="p" data-group-id="6552663310-9">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="6552663310-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6552663310-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="6552663310-13">[</span><span class="p" data-group-id="6552663310-13">]</span><span class="p" data-group-id="6552663310-12">}</span><span class="p" data-group-id="6552663310-11">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="6552663310-14">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6552663310-15">[</span><span class="p" data-group-id="6552663310-16">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="6552663310-16">}</span><span class="p" data-group-id="6552663310-15">]</span><span class="p" data-group-id="6552663310-14">}</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="6552663310-2">]</span><span class="p" data-group-id="6552663310-1">}</span><span class="p">.</span></code></pre><p><code class="inline">Par</code> is to be an atom. <code class="inline">Val</code> is any term. The application can retrieve the
│ │ │ +list of <code class="inline">{Par,Val}</code> tuples specified by a key <code class="inline">env</code> in the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0756148307-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0756148307-2">[</span><span class="p" data-group-id="0756148307-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="0756148307-3">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="0756148307-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="0756148307-4">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="0756148307-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0756148307-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="0756148307-6">]</span><span class="p" data-group-id="0756148307-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="0756148307-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0756148307-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="0756148307-8">]</span><span class="p" data-group-id="0756148307-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="0756148307-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0756148307-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="0756148307-10">]</span><span class="p" data-group-id="0756148307-9">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="0756148307-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0756148307-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="0756148307-13">[</span><span class="p" data-group-id="0756148307-13">]</span><span class="p" data-group-id="0756148307-12">}</span><span class="p" data-group-id="0756148307-11">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="0756148307-14">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0756148307-15">[</span><span class="p" data-group-id="0756148307-16">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="0756148307-16">}</span><span class="p" data-group-id="0756148307-15">]</span><span class="p" data-group-id="0756148307-14">}</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0756148307-2">]</span><span class="p" data-group-id="0756148307-1">}</span><span class="p">.</span></code></pre><p><code class="inline">Par</code> is to be an atom. <code class="inline">Val</code> is any term. The application can retrieve the
│ │ │  value of a configuration parameter by calling <code class="inline">application:get_env(App, Par)</code> or
│ │ │  a number of similar functions. For more information, see module <a href="../../lib/kernel-11.0/doc/html/application.html"><code class="inline">application</code></a>
│ │ │  in Kernel.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="2404091593-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="2404091593-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="2404091593-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="2404091593-2">]</span><span class="w"> </span><span class="p" data-group-id="2404091593-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="2404091593-3">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="5918733663-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="5918733663-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="5918733663-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="5918733663-2">]</span><span class="w"> </span><span class="p" data-group-id="5918733663-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="5918733663-3">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="2404091593-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="2404091593-4">)</span><span class="w">
│ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2404091593-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="2404091593-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="5918733663-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="5918733663-4">)</span><span class="w">
│ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="5918733663-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="5918733663-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="2404091593-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="2404091593-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2404091593-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="2404091593-7">}</span></code></pre><p>The values in the <code class="inline">.app</code> file can be overridden by values in a <em>system
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="5918733663-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="5918733663-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5918733663-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="5918733663-7">}</span></code></pre><p>The values in the <code class="inline">.app</code> file can be overridden by values in a <em>system
│ │ │  configuration file</em>. This is a file that contains configuration parameters for
│ │ │ -relevant applications:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0796259499-1">[</span><span class="p" data-group-id="0796259499-2">{</span><span class="n">Application1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0796259499-3">[</span><span class="p" data-group-id="0796259499-4">{</span><span class="n">Par11</span><span class="p">,</span><span class="n">Val11</span><span class="p" data-group-id="0796259499-4">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0796259499-3">]</span><span class="p" data-group-id="0796259499-2">}</span><span class="p">,</span><span class="w">
│ │ │ +relevant applications:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6542705925-1">[</span><span class="p" data-group-id="6542705925-2">{</span><span class="n">Application1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6542705925-3">[</span><span class="p" data-group-id="6542705925-4">{</span><span class="n">Par11</span><span class="p">,</span><span class="n">Val11</span><span class="p" data-group-id="6542705925-4">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6542705925-3">]</span><span class="p" data-group-id="6542705925-2">}</span><span class="p">,</span><span class="w">
│ │ │   </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0796259499-5">{</span><span class="n">ApplicationN</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0796259499-6">[</span><span class="p" data-group-id="0796259499-7">{</span><span class="n">ParN1</span><span class="p">,</span><span class="n">ValN1</span><span class="p" data-group-id="0796259499-7">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0796259499-6">]</span><span class="p" data-group-id="0796259499-5">}</span><span class="p" data-group-id="0796259499-1">]</span><span class="p">.</span></code></pre><p>The system configuration is to be called <code class="inline">Name.config</code> and Erlang is to be
│ │ │ + </span><span class="p" data-group-id="6542705925-5">{</span><span class="n">ApplicationN</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6542705925-6">[</span><span class="p" data-group-id="6542705925-7">{</span><span class="n">ParN1</span><span class="p">,</span><span class="n">ValN1</span><span class="p" data-group-id="6542705925-7">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6542705925-6">]</span><span class="p" data-group-id="6542705925-5">}</span><span class="p" data-group-id="6542705925-1">]</span><span class="p">.</span></code></pre><p>The system configuration is to be called <code class="inline">Name.config</code> and Erlang is to be
│ │ │  started with the command-line argument <code class="inline">-config Name</code>. For details, see
│ │ │  <a href="../../lib/kernel-11.0/doc/html/config.html"><code class="inline">config</code></a> in Kernel.</p><p><em>Example:</em></p><p>A file <code class="inline">test.config</code> is created with the following contents:</p><pre><code class="text">[{ch_app, [{file, &quot;testlog&quot;}]}].</code></pre><p>The value of <code class="inline">file</code> overrides the value of <code class="inline">file</code> as defined in the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -config test</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="3810068102-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="3810068102-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="3810068102-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="3810068102-2">]</span><span class="w"> </span><span class="p" data-group-id="3810068102-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="3810068102-3">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="5464189068-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="5464189068-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="5464189068-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="5464189068-2">]</span><span class="w"> </span><span class="p" data-group-id="5464189068-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="5464189068-3">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="3810068102-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="3810068102-4">)</span><span class="w">
│ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="3810068102-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="3810068102-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="5464189068-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="5464189068-4">)</span><span class="w">
│ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="5464189068-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="5464189068-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="3810068102-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="3810068102-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3810068102-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;testlog&quot;</span><span class="p" data-group-id="3810068102-7">}</span></code></pre><p>If <a href="release_handling.html#sys">release handling</a> is used, exactly one system
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="5464189068-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="5464189068-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5464189068-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;testlog&quot;</span><span class="p" data-group-id="5464189068-7">}</span></code></pre><p>If <a href="release_handling.html#sys">release handling</a> is used, exactly one system
│ │ │  configuration file is to be used and that file is to be called <code class="inline">sys.config</code>.</p><p>The values in the <code class="inline">.app</code> file and the values in a system configuration file can
│ │ │  be overridden directly from the command line:</p><pre><code class="text">% erl -ApplName Par1 Val1 ... ParN ValN</code></pre><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -ch_app file &#39;&quot;testlog&quot;&#39;</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="5833803165-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="5833803165-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="5833803165-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="5833803165-2">]</span><span class="w"> </span><span class="p" data-group-id="5833803165-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="5833803165-3">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="7442365635-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="7442365635-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="7442365635-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="7442365635-2">]</span><span class="w"> </span><span class="p" data-group-id="7442365635-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="7442365635-3">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="5833803165-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="5833803165-4">)</span><span class="w">
│ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="5833803165-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="5833803165-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="7442365635-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="7442365635-4">)</span><span class="w">
│ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="7442365635-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="7442365635-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="5833803165-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="5833803165-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5833803165-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;testlog&quot;</span><span class="p" data-group-id="5833803165-7">}</span></code></pre><h2 id="application-start-types" class="section-heading">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="7442365635-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="7442365635-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7442365635-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;testlog&quot;</span><span class="p" data-group-id="7442365635-7">}</span></code></pre><h2 id="application-start-types" class="section-heading">
│ │ │    <a href="#application-start-types" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Application Start Types</span>
│ │ │  </h2>
│ │ │  <p>A <em>start type</em> is defined when starting the application:</p><pre><code class="text">application:start(Application, Type)</code></pre><p><code class="inline">application:start(Application)</code> is the same as calling
│ │ │  <code class="inline">application:start(Application, temporary)</code>. The type can also be <code class="inline">permanent</code> or
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/appup_cookbook.html
│ │ │ @@ -120,18 +120,18 @@
│ │ │    <a href="#changing-a-functional-module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing a Functional Module</span>
│ │ │  </h2>
│ │ │  <p>When a functional module has been changed, for example, if a new function has
│ │ │  been added or a bug has been corrected, simple code replacement is sufficient,
│ │ │ -for example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8607331114-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8607331114-2">[</span><span class="p" data-group-id="8607331114-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8607331114-4">[</span><span class="p" data-group-id="8607331114-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="8607331114-5">}</span><span class="p" data-group-id="8607331114-4">]</span><span class="p" data-group-id="8607331114-3">}</span><span class="p" data-group-id="8607331114-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8607331114-6">[</span><span class="p" data-group-id="8607331114-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8607331114-8">[</span><span class="p" data-group-id="8607331114-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="8607331114-9">}</span><span class="p" data-group-id="8607331114-8">]</span><span class="p" data-group-id="8607331114-7">}</span><span class="p" data-group-id="8607331114-6">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8607331114-1">}</span><span class="p">.</span></code></pre><h2 id="changing-a-residence-module" class="section-heading">
│ │ │ +for example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9303765541-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9303765541-2">[</span><span class="p" data-group-id="9303765541-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9303765541-4">[</span><span class="p" data-group-id="9303765541-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="9303765541-5">}</span><span class="p" data-group-id="9303765541-4">]</span><span class="p" data-group-id="9303765541-3">}</span><span class="p" data-group-id="9303765541-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9303765541-6">[</span><span class="p" data-group-id="9303765541-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9303765541-8">[</span><span class="p" data-group-id="9303765541-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="9303765541-9">}</span><span class="p" data-group-id="9303765541-8">]</span><span class="p" data-group-id="9303765541-7">}</span><span class="p" data-group-id="9303765541-6">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9303765541-1">}</span><span class="p">.</span></code></pre><h2 id="changing-a-residence-module" class="section-heading">
│ │ │    <a href="#changing-a-residence-module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing a Residence Module</span>
│ │ │  </h2>
│ │ │  <p>In a system implemented according to the OTP design principles, all processes,
│ │ │  except system processes and special processes, reside in one of the behaviours
│ │ │ @@ -142,46 +142,46 @@
│ │ │    <a href="#changing-a-callback-module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing a Callback Module</span>
│ │ │  </h2>
│ │ │  <p>A callback module is a functional module, and for code extensions simple code
│ │ │  replacement is sufficient.</p><p><em>Example</em></p><p>When adding a function to <code class="inline">ch3</code>, as described in the example in
│ │ │ -<a href="release_handling.html#appup">Release Handling</a>, <code class="inline">ch_app.appup</code> looks as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2757012155-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="2757012155-2">[</span><span class="p" data-group-id="2757012155-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2757012155-4">[</span><span class="p" data-group-id="2757012155-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="2757012155-5">}</span><span class="p" data-group-id="2757012155-4">]</span><span class="p" data-group-id="2757012155-3">}</span><span class="p" data-group-id="2757012155-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="2757012155-6">[</span><span class="p" data-group-id="2757012155-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2757012155-8">[</span><span class="p" data-group-id="2757012155-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="2757012155-9">}</span><span class="p" data-group-id="2757012155-8">]</span><span class="p" data-group-id="2757012155-7">}</span><span class="p" data-group-id="2757012155-6">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2757012155-1">}</span><span class="p">.</span></code></pre><p>OTP also supports changing the internal state of behaviour processes; see
│ │ │ +<a href="release_handling.html#appup">Release Handling</a>, <code class="inline">ch_app.appup</code> looks as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7965985637-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7965985637-2">[</span><span class="p" data-group-id="7965985637-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7965985637-4">[</span><span class="p" data-group-id="7965985637-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="7965985637-5">}</span><span class="p" data-group-id="7965985637-4">]</span><span class="p" data-group-id="7965985637-3">}</span><span class="p" data-group-id="7965985637-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7965985637-6">[</span><span class="p" data-group-id="7965985637-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7965985637-8">[</span><span class="p" data-group-id="7965985637-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="7965985637-9">}</span><span class="p" data-group-id="7965985637-8">]</span><span class="p" data-group-id="7965985637-7">}</span><span class="p" data-group-id="7965985637-6">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7965985637-1">}</span><span class="p">.</span></code></pre><p>OTP also supports changing the internal state of behaviour processes; see
│ │ │  <a href="appup_cookbook.html#int_state">Changing Internal State</a>.</p><p><a href="" id="int_state"></a></p><h2 id="changing-internal-state" class="section-heading">
│ │ │    <a href="#changing-internal-state" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing Internal State</span>
│ │ │  </h2>
│ │ │  <p>In this case, simple code replacement is not sufficient. The process must
│ │ │  explicitly transform its state using the callback function <code class="inline">code_change/3</code> before
│ │ │  switching to the new version of the callback module. Thus, synchronized code
│ │ │  replacement is used.</p><p><em>Example</em></p><p>Consider the <code class="inline">ch3</code> module from
│ │ │  <a href="gen_server_concepts.html#ex">gen_server Behaviour</a>. The internal state is a term
│ │ │  <code class="inline">Chs</code> representing the available channels. Assume you want to add a counter <code class="inline">N</code>,
│ │ │  which keeps track of the number of <code class="inline">alloc</code> requests so far. This means that the
│ │ │ -format must be changed to <code class="inline">{Chs,N}</code>.</p><p>The <code class="inline">.appup</code> file can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7615863964-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7615863964-2">[</span><span class="p" data-group-id="7615863964-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7615863964-4">[</span><span class="p" data-group-id="7615863964-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7615863964-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7615863964-7">[</span><span class="p" data-group-id="7615863964-7">]</span><span class="p" data-group-id="7615863964-6">}</span><span class="p" data-group-id="7615863964-5">}</span><span class="p" data-group-id="7615863964-4">]</span><span class="p" data-group-id="7615863964-3">}</span><span class="p" data-group-id="7615863964-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7615863964-8">[</span><span class="p" data-group-id="7615863964-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7615863964-10">[</span><span class="p" data-group-id="7615863964-11">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7615863964-12">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7615863964-13">[</span><span class="p" data-group-id="7615863964-13">]</span><span class="p" data-group-id="7615863964-12">}</span><span class="p" data-group-id="7615863964-11">}</span><span class="p" data-group-id="7615863964-10">]</span><span class="p" data-group-id="7615863964-9">}</span><span class="p" data-group-id="7615863964-8">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7615863964-1">}</span><span class="p">.</span></code></pre><p>The third element of the <code class="inline">update</code> instruction is a tuple <code class="inline">{advanced,Extra}</code>,
│ │ │ +format must be changed to <code class="inline">{Chs,N}</code>.</p><p>The <code class="inline">.appup</code> file can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4952518950-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4952518950-2">[</span><span class="p" data-group-id="4952518950-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4952518950-4">[</span><span class="p" data-group-id="4952518950-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4952518950-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4952518950-7">[</span><span class="p" data-group-id="4952518950-7">]</span><span class="p" data-group-id="4952518950-6">}</span><span class="p" data-group-id="4952518950-5">}</span><span class="p" data-group-id="4952518950-4">]</span><span class="p" data-group-id="4952518950-3">}</span><span class="p" data-group-id="4952518950-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4952518950-8">[</span><span class="p" data-group-id="4952518950-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4952518950-10">[</span><span class="p" data-group-id="4952518950-11">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4952518950-12">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4952518950-13">[</span><span class="p" data-group-id="4952518950-13">]</span><span class="p" data-group-id="4952518950-12">}</span><span class="p" data-group-id="4952518950-11">}</span><span class="p" data-group-id="4952518950-10">]</span><span class="p" data-group-id="4952518950-9">}</span><span class="p" data-group-id="4952518950-8">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4952518950-1">}</span><span class="p">.</span></code></pre><p>The third element of the <code class="inline">update</code> instruction is a tuple <code class="inline">{advanced,Extra}</code>,
│ │ │  which says that the affected processes are to do a state transformation before
│ │ │  loading the new version of the module. This is done by the processes calling the
│ │ │  callback function <code class="inline">code_change/3</code> (see <a href="../../lib/stdlib-8.0/doc/html/gen_server.html"><code class="inline">gen_server</code></a> in STDLIB).
│ │ │ -The term <code class="inline">Extra</code>, in this case <code class="inline">[]</code>, is passed as is to the function:</p><p><a href="" id="code_change"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8432417445-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="8432417445-1">)</span><span class="p">.</span><span class="w">
│ │ │ +The term <code class="inline">Extra</code>, in this case <code class="inline">[]</code>, is passed as is to the function:</p><p><a href="" id="code_change"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5161559132-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="5161559132-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8432417445-2">(</span><span class="p" data-group-id="8432417445-3">[</span><span class="ss">code_change</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="8432417445-3">]</span><span class="p" data-group-id="8432417445-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5161559132-2">(</span><span class="p" data-group-id="5161559132-3">[</span><span class="ss">code_change</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="5161559132-3">]</span><span class="p" data-group-id="5161559132-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">code_change</span><span class="p" data-group-id="8432417445-4">(</span><span class="p" data-group-id="8432417445-5">{</span><span class="ss">down</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Vsn</span><span class="p" data-group-id="8432417445-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8432417445-6">{</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p" data-group-id="8432417445-6">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="8432417445-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8432417445-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="8432417445-7">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">code_change</span><span class="p" data-group-id="8432417445-8">(</span><span class="p">_</span><span class="n">Vsn</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="8432417445-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8432417445-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8432417445-10">{</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="8432417445-10">}</span><span class="p" data-group-id="8432417445-9">}</span><span class="p">.</span></code></pre><p>The first argument is <code class="inline">{down,Vsn}</code> if there is a downgrade, or <code class="inline">Vsn</code> if there is
│ │ │ +</span><span class="nf">code_change</span><span class="p" data-group-id="5161559132-4">(</span><span class="p" data-group-id="5161559132-5">{</span><span class="ss">down</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Vsn</span><span class="p" data-group-id="5161559132-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5161559132-6">{</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p" data-group-id="5161559132-6">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="5161559132-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5161559132-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="5161559132-7">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">code_change</span><span class="p" data-group-id="5161559132-8">(</span><span class="p">_</span><span class="n">Vsn</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="5161559132-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5161559132-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5161559132-10">{</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="5161559132-10">}</span><span class="p" data-group-id="5161559132-9">}</span><span class="p">.</span></code></pre><p>The first argument is <code class="inline">{down,Vsn}</code> if there is a downgrade, or <code class="inline">Vsn</code> if there is
│ │ │  an upgrade. The term <code class="inline">Vsn</code> is fetched from the 'original' version of the module,
│ │ │  that is, the version you are upgrading from, or downgrading to.</p><p>The version is defined by the module attribute <code class="inline">vsn</code>, if any. There is no such
│ │ │  attribute in <code class="inline">ch3</code>, so in this case the version is the checksum (a huge integer)
│ │ │  of the beam file, an uninteresting value, which is ignored.</p><p>The other callback functions of <code class="inline">ch3</code> must also be modified and perhaps a new
│ │ │  interface function must be added, but this is not shown here.</p><h2 id="module-dependencies" class="section-heading">
│ │ │    <a href="#module-dependencies" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -190,67 +190,67 @@
│ │ │  </h2>
│ │ │  <p>Assume that a module is extended by adding an interface function, as in the
│ │ │  example in <a href="release_handling.html#appup">Release Handling</a>, where a function
│ │ │  <code class="inline">available/0</code> is added to <code class="inline">ch3</code>.</p><p>If a call is added to this function, say in module <code class="inline">m1</code>, a runtime error could
│ │ │  occur during release upgrade if the new version of <code class="inline">m1</code> is loaded first and
│ │ │  calls <code class="inline">ch3:available/0</code> before the new version of <code class="inline">ch3</code> is loaded.</p><p>Thus, <code class="inline">ch3</code> must be loaded before <code class="inline">m1</code>, in the upgrade case, and conversely in
│ │ │  the downgrade case. <code class="inline">m1</code> is said to be <em>dependent on</em> <code class="inline">ch3</code>. In a release
│ │ │ -handling instruction, this is expressed by the <code class="inline">DepMods</code> element:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4371820175-1">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">DepMods</span><span class="p" data-group-id="4371820175-1">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4371820175-2">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4371820175-3">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="4371820175-3">}</span><span class="p">,</span><span class="w"> </span><span class="n">DepMods</span><span class="p" data-group-id="4371820175-2">}</span></code></pre><p><code class="inline">DepMods</code> is a list of modules, on which <code class="inline">Module</code> is dependent.</p><p><em>Example</em></p><p>The module <code class="inline">m1</code> in application <code class="inline">myapp</code> is dependent on <code class="inline">ch3</code> when
│ │ │ +handling instruction, this is expressed by the <code class="inline">DepMods</code> element:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0901959386-1">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">DepMods</span><span class="p" data-group-id="0901959386-1">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0901959386-2">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0901959386-3">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="0901959386-3">}</span><span class="p">,</span><span class="w"> </span><span class="n">DepMods</span><span class="p" data-group-id="0901959386-2">}</span></code></pre><p><code class="inline">DepMods</code> is a list of modules, on which <code class="inline">Module</code> is dependent.</p><p><em>Example</em></p><p>The module <code class="inline">m1</code> in application <code class="inline">myapp</code> is dependent on <code class="inline">ch3</code> when
│ │ │  upgrading from &quot;1&quot; to &quot;2&quot;, or downgrading from &quot;2&quot; to &quot;1&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="ss">myapp</span><span class="p">.</span><span class="nc">appup</span><span class="p">:</span><span class="w">
│ │ │  
│ │ │ -</span><span class="p" data-group-id="1533198635-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1533198635-2">[</span><span class="p" data-group-id="1533198635-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1533198635-4">[</span><span class="p" data-group-id="1533198635-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1533198635-6">[</span><span class="ss">ch3</span><span class="p" data-group-id="1533198635-6">]</span><span class="p" data-group-id="1533198635-5">}</span><span class="p" data-group-id="1533198635-4">]</span><span class="p" data-group-id="1533198635-3">}</span><span class="p" data-group-id="1533198635-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1533198635-7">[</span><span class="p" data-group-id="1533198635-8">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1533198635-9">[</span><span class="p" data-group-id="1533198635-10">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1533198635-11">[</span><span class="ss">ch3</span><span class="p" data-group-id="1533198635-11">]</span><span class="p" data-group-id="1533198635-10">}</span><span class="p" data-group-id="1533198635-9">]</span><span class="p" data-group-id="1533198635-8">}</span><span class="p" data-group-id="1533198635-7">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1533198635-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6373248229-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="6373248229-2">[</span><span class="p" data-group-id="6373248229-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6373248229-4">[</span><span class="p" data-group-id="6373248229-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6373248229-6">[</span><span class="ss">ch3</span><span class="p" data-group-id="6373248229-6">]</span><span class="p" data-group-id="6373248229-5">}</span><span class="p" data-group-id="6373248229-4">]</span><span class="p" data-group-id="6373248229-3">}</span><span class="p" data-group-id="6373248229-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="6373248229-7">[</span><span class="p" data-group-id="6373248229-8">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6373248229-9">[</span><span class="p" data-group-id="6373248229-10">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6373248229-11">[</span><span class="ss">ch3</span><span class="p" data-group-id="6373248229-11">]</span><span class="p" data-group-id="6373248229-10">}</span><span class="p" data-group-id="6373248229-9">]</span><span class="p" data-group-id="6373248229-8">}</span><span class="p" data-group-id="6373248229-7">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6373248229-1">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="ss">ch_app</span><span class="p">.</span><span class="nc">appup</span><span class="p">:</span><span class="w">
│ │ │  
│ │ │ -</span><span class="p" data-group-id="1533198635-12">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1533198635-13">[</span><span class="p" data-group-id="1533198635-14">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1533198635-15">[</span><span class="p" data-group-id="1533198635-16">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="1533198635-16">}</span><span class="p" data-group-id="1533198635-15">]</span><span class="p" data-group-id="1533198635-14">}</span><span class="p" data-group-id="1533198635-13">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1533198635-17">[</span><span class="p" data-group-id="1533198635-18">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1533198635-19">[</span><span class="p" data-group-id="1533198635-20">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="1533198635-20">}</span><span class="p" data-group-id="1533198635-19">]</span><span class="p" data-group-id="1533198635-18">}</span><span class="p" data-group-id="1533198635-17">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1533198635-12">}</span><span class="p">.</span></code></pre><p>If instead <code class="inline">m1</code> and <code class="inline">ch3</code> belong to the same application, the <code class="inline">.appup</code> file can
│ │ │ -look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2314775581-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="2314775581-2">[</span><span class="p" data-group-id="2314775581-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="2314775581-4">[</span><span class="p" data-group-id="2314775581-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="2314775581-5">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2314775581-6">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2314775581-7">[</span><span class="ss">ch3</span><span class="p" data-group-id="2314775581-7">]</span><span class="p" data-group-id="2314775581-6">}</span><span class="p" data-group-id="2314775581-4">]</span><span class="p" data-group-id="2314775581-3">}</span><span class="p" data-group-id="2314775581-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="2314775581-8">[</span><span class="p" data-group-id="2314775581-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="2314775581-10">[</span><span class="p" data-group-id="2314775581-11">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="2314775581-11">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2314775581-12">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2314775581-13">[</span><span class="ss">ch3</span><span class="p" data-group-id="2314775581-13">]</span><span class="p" data-group-id="2314775581-12">}</span><span class="p" data-group-id="2314775581-10">]</span><span class="p" data-group-id="2314775581-9">}</span><span class="p" data-group-id="2314775581-8">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2314775581-1">}</span><span class="p">.</span></code></pre><p><code class="inline">m1</code> is dependent on <code class="inline">ch3</code> also when downgrading. <code class="inline">systools</code> knows the
│ │ │ +</span><span class="p" data-group-id="6373248229-12">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="6373248229-13">[</span><span class="p" data-group-id="6373248229-14">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6373248229-15">[</span><span class="p" data-group-id="6373248229-16">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="6373248229-16">}</span><span class="p" data-group-id="6373248229-15">]</span><span class="p" data-group-id="6373248229-14">}</span><span class="p" data-group-id="6373248229-13">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="6373248229-17">[</span><span class="p" data-group-id="6373248229-18">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6373248229-19">[</span><span class="p" data-group-id="6373248229-20">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="6373248229-20">}</span><span class="p" data-group-id="6373248229-19">]</span><span class="p" data-group-id="6373248229-18">}</span><span class="p" data-group-id="6373248229-17">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6373248229-12">}</span><span class="p">.</span></code></pre><p>If instead <code class="inline">m1</code> and <code class="inline">ch3</code> belong to the same application, the <code class="inline">.appup</code> file can
│ │ │ +look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8077781631-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8077781631-2">[</span><span class="p" data-group-id="8077781631-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="8077781631-4">[</span><span class="p" data-group-id="8077781631-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="8077781631-5">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8077781631-6">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8077781631-7">[</span><span class="ss">ch3</span><span class="p" data-group-id="8077781631-7">]</span><span class="p" data-group-id="8077781631-6">}</span><span class="p" data-group-id="8077781631-4">]</span><span class="p" data-group-id="8077781631-3">}</span><span class="p" data-group-id="8077781631-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8077781631-8">[</span><span class="p" data-group-id="8077781631-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="8077781631-10">[</span><span class="p" data-group-id="8077781631-11">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="8077781631-11">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8077781631-12">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8077781631-13">[</span><span class="ss">ch3</span><span class="p" data-group-id="8077781631-13">]</span><span class="p" data-group-id="8077781631-12">}</span><span class="p" data-group-id="8077781631-10">]</span><span class="p" data-group-id="8077781631-9">}</span><span class="p" data-group-id="8077781631-8">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8077781631-1">}</span><span class="p">.</span></code></pre><p><code class="inline">m1</code> is dependent on <code class="inline">ch3</code> also when downgrading. <code class="inline">systools</code> knows the
│ │ │  difference between up- and downgrading and generates a correct <code class="inline">relup</code>, where
│ │ │  <code class="inline">ch3</code> is loaded before <code class="inline">m1</code> when upgrading, but <code class="inline">m1</code> is loaded before <code class="inline">ch3</code> when
│ │ │  downgrading.</p><p><a href="" id="spec"></a></p><h2 id="changing-code-for-a-special-process" class="section-heading">
│ │ │    <a href="#changing-code-for-a-special-process" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing Code for a Special Process</span>
│ │ │  </h2>
│ │ │  <p>In this case, simple code replacement is not sufficient. When a new version of a
│ │ │  residence module for a special process is loaded, the process must make a fully
│ │ │  qualified call to its loop function to switch to the new code. Thus,
│ │ │  synchronized code replacement must be used.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The name(s) of the user-defined residence module(s) must be listed in the
│ │ │  <code class="inline">Modules</code> part of the child specification for the special process. Otherwise
│ │ │  the release handler cannot find the process.</p></section><p><em>Example</em></p><p>Consider the example <code class="inline">ch4</code> in <a href="spec_proc.html#ex">sys and proc_lib</a>.
│ │ │ -When started by a supervisor, the child specification can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0827253534-1">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0827253534-2">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0827253534-3">[</span><span class="p" data-group-id="0827253534-3">]</span><span class="p" data-group-id="0827253534-2">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="ss">permanent</span><span class="p">,</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p">,</span><span class="w"> </span><span class="ss">worker</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0827253534-4">[</span><span class="ss">ch4</span><span class="p" data-group-id="0827253534-4">]</span><span class="p" data-group-id="0827253534-1">}</span></code></pre><p>If <code class="inline">ch4</code> is part of the application <code class="inline">sp_app</code> and a new version of the module is
│ │ │ +When started by a supervisor, the child specification can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1949316728-1">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1949316728-2">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1949316728-3">[</span><span class="p" data-group-id="1949316728-3">]</span><span class="p" data-group-id="1949316728-2">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="ss">permanent</span><span class="p">,</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p">,</span><span class="w"> </span><span class="ss">worker</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1949316728-4">[</span><span class="ss">ch4</span><span class="p" data-group-id="1949316728-4">]</span><span class="p" data-group-id="1949316728-1">}</span></code></pre><p>If <code class="inline">ch4</code> is part of the application <code class="inline">sp_app</code> and a new version of the module is
│ │ │  to be loaded when upgrading from version &quot;1&quot; to &quot;2&quot; of this application,
│ │ │ -<code class="inline">sp_app.appup</code> can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6851324381-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="6851324381-2">[</span><span class="p" data-group-id="6851324381-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6851324381-4">[</span><span class="p" data-group-id="6851324381-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6851324381-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6851324381-7">[</span><span class="p" data-group-id="6851324381-7">]</span><span class="p" data-group-id="6851324381-6">}</span><span class="p" data-group-id="6851324381-5">}</span><span class="p" data-group-id="6851324381-4">]</span><span class="p" data-group-id="6851324381-3">}</span><span class="p" data-group-id="6851324381-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="6851324381-8">[</span><span class="p" data-group-id="6851324381-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6851324381-10">[</span><span class="p" data-group-id="6851324381-11">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6851324381-12">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6851324381-13">[</span><span class="p" data-group-id="6851324381-13">]</span><span class="p" data-group-id="6851324381-12">}</span><span class="p" data-group-id="6851324381-11">}</span><span class="p" data-group-id="6851324381-10">]</span><span class="p" data-group-id="6851324381-9">}</span><span class="p" data-group-id="6851324381-8">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6851324381-1">}</span><span class="p">.</span></code></pre><p>The <code class="inline">update</code> instruction must contain the tuple <code class="inline">{advanced,Extra}</code>. The
│ │ │ +<code class="inline">sp_app.appup</code> can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4020756313-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4020756313-2">[</span><span class="p" data-group-id="4020756313-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4020756313-4">[</span><span class="p" data-group-id="4020756313-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4020756313-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4020756313-7">[</span><span class="p" data-group-id="4020756313-7">]</span><span class="p" data-group-id="4020756313-6">}</span><span class="p" data-group-id="4020756313-5">}</span><span class="p" data-group-id="4020756313-4">]</span><span class="p" data-group-id="4020756313-3">}</span><span class="p" data-group-id="4020756313-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4020756313-8">[</span><span class="p" data-group-id="4020756313-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4020756313-10">[</span><span class="p" data-group-id="4020756313-11">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4020756313-12">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4020756313-13">[</span><span class="p" data-group-id="4020756313-13">]</span><span class="p" data-group-id="4020756313-12">}</span><span class="p" data-group-id="4020756313-11">}</span><span class="p" data-group-id="4020756313-10">]</span><span class="p" data-group-id="4020756313-9">}</span><span class="p" data-group-id="4020756313-8">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4020756313-1">}</span><span class="p">.</span></code></pre><p>The <code class="inline">update</code> instruction must contain the tuple <code class="inline">{advanced,Extra}</code>. The
│ │ │  instruction makes the special process call the callback function
│ │ │  <code class="inline">system_code_change/4</code>, a function the user must implement. The term <code class="inline">Extra</code>, in
│ │ │ -this case <code class="inline">[]</code>, is passed as is to <code class="inline">system_code_change/4</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1448284294-1">(</span><span class="ss">ch4</span><span class="p" data-group-id="1448284294-1">)</span><span class="p">.</span><span class="w">
│ │ │ +this case <code class="inline">[]</code>, is passed as is to <code class="inline">system_code_change/4</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7935799762-1">(</span><span class="ss">ch4</span><span class="p" data-group-id="7935799762-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1448284294-2">(</span><span class="p" data-group-id="1448284294-3">[</span><span class="ss">system_code_change</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="1448284294-3">]</span><span class="p" data-group-id="1448284294-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7935799762-2">(</span><span class="p" data-group-id="7935799762-3">[</span><span class="ss">system_code_change</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="7935799762-3">]</span><span class="p" data-group-id="7935799762-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_code_change</span><span class="p" data-group-id="1448284294-4">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="1448284294-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1448284294-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1448284294-5">}</span><span class="p">.</span></code></pre><ul><li>The first argument is the internal state <code class="inline">State</code>, passed from
│ │ │ +</span><span class="nf">system_code_change</span><span class="p" data-group-id="7935799762-4">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="7935799762-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7935799762-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="7935799762-5">}</span><span class="p">.</span></code></pre><ul><li>The first argument is the internal state <code class="inline">State</code>, passed from
│ │ │  function <a href="../../lib/stdlib-8.0/doc/html/sys.html#handle_system_msg/6"><code class="inline">sys:handle_system_msg(Request, From, Parent, Module, Deb, State)</code></a>, and called by the special
│ │ │  process when a system message is received. In <code class="inline">ch4</code>, the internal
│ │ │  state is the set of available channels <code class="inline">Chs</code>.</li><li>The second argument is the name of the module (<code class="inline">ch4</code>).</li><li>The third argument is <code class="inline">Vsn</code> or <code class="inline">{down,Vsn}</code>, as described for
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/gen_server.html#c:code_change/3"><code class="inline">gen_server:code_change/3</code></a> in
│ │ │  <a href="appup_cookbook.html#code_change">Changing Internal State</a>.</li></ul><p>In this case, all arguments but the first are ignored and the function simply
│ │ │  returns the internal state again. This is enough if the code only has been
│ │ │  extended. If instead the internal state is changed (similar to the example in
│ │ │ @@ -271,86 +271,86 @@
│ │ │    <span class="text">Changing Properties</span>
│ │ │  </h3>
│ │ │  <p>Since the supervisor is to change its internal state, synchronized code
│ │ │  replacement is required. However, a special <code class="inline">update</code> instruction must be used.</p><p>First, the new version of the callback module must be loaded, both in the case
│ │ │  of upgrade and downgrade. Then the new return value of <code class="inline">init/1</code> can be checked
│ │ │  and the internal state be changed accordingly.</p><p>The following <code class="inline">upgrade</code> instruction is used for supervisors:</p><pre><code class="text">{update, Module, supervisor}</code></pre><p><em>Example</em></p><p>To change the restart strategy of <code class="inline">ch_sup</code> (from
│ │ │  <a href="sup_princ.html#ex">Supervisor Behaviour</a>) from <code class="inline">one_for_one</code> to <code class="inline">one_for_all</code>,
│ │ │ -change the callback function <code class="inline">init/1</code> in <code class="inline">ch_sup.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1549161043-1">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="1549161043-1">)</span><span class="p">.</span><span class="w">
│ │ │ +change the callback function <code class="inline">init/1</code> in <code class="inline">ch_sup.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4177691014-1">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="4177691014-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="1549161043-2">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="1549161043-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1549161043-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1549161043-4">{</span><span class="p" data-group-id="1549161043-5">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">one_for_all</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1549161043-5">}</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1549161043-4">}</span><span class="p" data-group-id="1549161043-3">}</span><span class="p">.</span></code></pre><p>The file <code class="inline">ch_app.appup</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3266131826-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3266131826-2">[</span><span class="p" data-group-id="3266131826-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3266131826-4">[</span><span class="p" data-group-id="3266131826-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="3266131826-5">}</span><span class="p" data-group-id="3266131826-4">]</span><span class="p" data-group-id="3266131826-3">}</span><span class="p" data-group-id="3266131826-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3266131826-6">[</span><span class="p" data-group-id="3266131826-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3266131826-8">[</span><span class="p" data-group-id="3266131826-9">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="3266131826-9">}</span><span class="p" data-group-id="3266131826-8">]</span><span class="p" data-group-id="3266131826-7">}</span><span class="p" data-group-id="3266131826-6">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3266131826-1">}</span><span class="p">.</span></code></pre><h3 id="changing-child-specifications" class="section-heading">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="4177691014-2">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="4177691014-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4177691014-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4177691014-4">{</span><span class="p" data-group-id="4177691014-5">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">one_for_all</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4177691014-5">}</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4177691014-4">}</span><span class="p" data-group-id="4177691014-3">}</span><span class="p">.</span></code></pre><p>The file <code class="inline">ch_app.appup</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5588118758-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5588118758-2">[</span><span class="p" data-group-id="5588118758-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5588118758-4">[</span><span class="p" data-group-id="5588118758-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="5588118758-5">}</span><span class="p" data-group-id="5588118758-4">]</span><span class="p" data-group-id="5588118758-3">}</span><span class="p" data-group-id="5588118758-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5588118758-6">[</span><span class="p" data-group-id="5588118758-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5588118758-8">[</span><span class="p" data-group-id="5588118758-9">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="5588118758-9">}</span><span class="p" data-group-id="5588118758-8">]</span><span class="p" data-group-id="5588118758-7">}</span><span class="p" data-group-id="5588118758-6">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5588118758-1">}</span><span class="p">.</span></code></pre><h3 id="changing-child-specifications" class="section-heading">
│ │ │    <a href="#changing-child-specifications" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing Child Specifications</span>
│ │ │  </h3>
│ │ │  <p>The instruction, and thus the <code class="inline">.appup</code> file, when changing an existing child
│ │ │ -specification, is the same as when changing properties as described earlier:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5528406664-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5528406664-2">[</span><span class="p" data-group-id="5528406664-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5528406664-4">[</span><span class="p" data-group-id="5528406664-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="5528406664-5">}</span><span class="p" data-group-id="5528406664-4">]</span><span class="p" data-group-id="5528406664-3">}</span><span class="p" data-group-id="5528406664-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5528406664-6">[</span><span class="p" data-group-id="5528406664-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5528406664-8">[</span><span class="p" data-group-id="5528406664-9">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="5528406664-9">}</span><span class="p" data-group-id="5528406664-8">]</span><span class="p" data-group-id="5528406664-7">}</span><span class="p" data-group-id="5528406664-6">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5528406664-1">}</span><span class="p">.</span></code></pre><p>The changes do not affect existing child processes. For example, changing the
│ │ │ +specification, is the same as when changing properties as described earlier:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3999266387-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="3999266387-2">[</span><span class="p" data-group-id="3999266387-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3999266387-4">[</span><span class="p" data-group-id="3999266387-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="3999266387-5">}</span><span class="p" data-group-id="3999266387-4">]</span><span class="p" data-group-id="3999266387-3">}</span><span class="p" data-group-id="3999266387-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="3999266387-6">[</span><span class="p" data-group-id="3999266387-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3999266387-8">[</span><span class="p" data-group-id="3999266387-9">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="3999266387-9">}</span><span class="p" data-group-id="3999266387-8">]</span><span class="p" data-group-id="3999266387-7">}</span><span class="p" data-group-id="3999266387-6">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3999266387-1">}</span><span class="p">.</span></code></pre><p>The changes do not affect existing child processes. For example, changing the
│ │ │  start function only specifies how the child process is to be restarted, if
│ │ │  needed later on.</p><p>The id of the child specification cannot be changed.</p><p>Changing the <code class="inline">Modules</code> field of the child specification can affect the release
│ │ │  handling process itself, as this field is used to identify which processes are
│ │ │  affected when doing a synchronized code replacement.</p><p><a href="" id="sup_add"></a></p><h3 id="adding-and-deleting-child-processes" class="section-heading">
│ │ │    <a href="#adding-and-deleting-child-processes" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Adding and Deleting Child Processes</span>
│ │ │  </h3>
│ │ │  <p>As stated earlier, changing child specifications does not affect existing child
│ │ │  processes. New child specifications are automatically added, but not deleted.
│ │ │  Child processes are not automatically started or terminated, this must be done
│ │ │  using <code class="inline">apply</code> instructions.</p><p><em>Example</em></p><p>Assume a new child process <code class="inline">m1</code> is to be added to <code class="inline">ch_sup</code> when
│ │ │  upgrading <code class="inline">ch_app</code> from &quot;1&quot; to &quot;2&quot;. This means <code class="inline">m1</code> is to be deleted when
│ │ │ -downgrading from &quot;2&quot; to &quot;1&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8712310722-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8712310722-2">[</span><span class="p" data-group-id="8712310722-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="8712310722-4">[</span><span class="p" data-group-id="8712310722-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="8712310722-5">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8712310722-6">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8712310722-7">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">restart_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8712310722-8">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="8712310722-8">]</span><span class="p" data-group-id="8712310722-7">}</span><span class="p" data-group-id="8712310722-6">}</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="8712310722-4">]</span><span class="p" data-group-id="8712310722-3">}</span><span class="p" data-group-id="8712310722-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8712310722-9">[</span><span class="p" data-group-id="8712310722-10">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="8712310722-11">[</span><span class="p" data-group-id="8712310722-12">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8712310722-13">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8712310722-14">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="8712310722-14">]</span><span class="p" data-group-id="8712310722-13">}</span><span class="p" data-group-id="8712310722-12">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8712310722-15">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8712310722-16">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">delete_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8712310722-17">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="8712310722-17">]</span><span class="p" data-group-id="8712310722-16">}</span><span class="p" data-group-id="8712310722-15">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8712310722-18">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="8712310722-18">}</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="8712310722-11">]</span><span class="p" data-group-id="8712310722-10">}</span><span class="p" data-group-id="8712310722-9">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8712310722-1">}</span><span class="p">.</span></code></pre><p>The order of the instructions is important.</p><p>The supervisor must be registered as <code class="inline">ch_sup</code> for the script to work. If the
│ │ │ +downgrading from &quot;2&quot; to &quot;1&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0742589404-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0742589404-2">[</span><span class="p" data-group-id="0742589404-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="0742589404-4">[</span><span class="p" data-group-id="0742589404-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="0742589404-5">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0742589404-6">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0742589404-7">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">restart_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0742589404-8">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="0742589404-8">]</span><span class="p" data-group-id="0742589404-7">}</span><span class="p" data-group-id="0742589404-6">}</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="0742589404-4">]</span><span class="p" data-group-id="0742589404-3">}</span><span class="p" data-group-id="0742589404-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0742589404-9">[</span><span class="p" data-group-id="0742589404-10">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="0742589404-11">[</span><span class="p" data-group-id="0742589404-12">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0742589404-13">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0742589404-14">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="0742589404-14">]</span><span class="p" data-group-id="0742589404-13">}</span><span class="p" data-group-id="0742589404-12">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0742589404-15">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0742589404-16">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">delete_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0742589404-17">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="0742589404-17">]</span><span class="p" data-group-id="0742589404-16">}</span><span class="p" data-group-id="0742589404-15">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0742589404-18">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="0742589404-18">}</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="0742589404-11">]</span><span class="p" data-group-id="0742589404-10">}</span><span class="p" data-group-id="0742589404-9">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0742589404-1">}</span><span class="p">.</span></code></pre><p>The order of the instructions is important.</p><p>The supervisor must be registered as <code class="inline">ch_sup</code> for the script to work. If the
│ │ │  supervisor is not registered, it cannot be accessed directly from the script.
│ │ │  Instead a help function that finds the pid of the supervisor and calls
│ │ │  <code class="inline">supervisor:restart_child</code>, and so on, must be written. This function is then to
│ │ │  be called from the script using the <code class="inline">apply</code> instruction.</p><p>If the module <code class="inline">m1</code> is introduced in version &quot;2&quot; of <code class="inline">ch_app</code>, it must also be
│ │ │ -loaded when upgrading and deleted when downgrading:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2310590046-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="2310590046-2">[</span><span class="p" data-group-id="2310590046-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="2310590046-4">[</span><span class="p" data-group-id="2310590046-5">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="2310590046-5">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2310590046-6">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="2310590046-6">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2310590046-7">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2310590046-8">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">restart_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2310590046-9">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="2310590046-9">]</span><span class="p" data-group-id="2310590046-8">}</span><span class="p" data-group-id="2310590046-7">}</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="2310590046-4">]</span><span class="p" data-group-id="2310590046-3">}</span><span class="p" data-group-id="2310590046-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="2310590046-10">[</span><span class="p" data-group-id="2310590046-11">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="2310590046-12">[</span><span class="p" data-group-id="2310590046-13">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2310590046-14">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2310590046-15">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="2310590046-15">]</span><span class="p" data-group-id="2310590046-14">}</span><span class="p" data-group-id="2310590046-13">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2310590046-16">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2310590046-17">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">delete_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2310590046-18">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="2310590046-18">]</span><span class="p" data-group-id="2310590046-17">}</span><span class="p" data-group-id="2310590046-16">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2310590046-19">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="2310590046-19">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2310590046-20">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="2310590046-20">}</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="2310590046-12">]</span><span class="p" data-group-id="2310590046-11">}</span><span class="p" data-group-id="2310590046-10">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2310590046-1">}</span><span class="p">.</span></code></pre><p>As stated earlier, the order of the instructions is important. When upgrading,
│ │ │ +loaded when upgrading and deleted when downgrading:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2288442299-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="2288442299-2">[</span><span class="p" data-group-id="2288442299-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="2288442299-4">[</span><span class="p" data-group-id="2288442299-5">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="2288442299-5">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2288442299-6">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="2288442299-6">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2288442299-7">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2288442299-8">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">restart_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2288442299-9">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="2288442299-9">]</span><span class="p" data-group-id="2288442299-8">}</span><span class="p" data-group-id="2288442299-7">}</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="2288442299-4">]</span><span class="p" data-group-id="2288442299-3">}</span><span class="p" data-group-id="2288442299-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="2288442299-10">[</span><span class="p" data-group-id="2288442299-11">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="2288442299-12">[</span><span class="p" data-group-id="2288442299-13">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2288442299-14">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2288442299-15">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="2288442299-15">]</span><span class="p" data-group-id="2288442299-14">}</span><span class="p" data-group-id="2288442299-13">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2288442299-16">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2288442299-17">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">delete_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2288442299-18">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="2288442299-18">]</span><span class="p" data-group-id="2288442299-17">}</span><span class="p" data-group-id="2288442299-16">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2288442299-19">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="2288442299-19">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2288442299-20">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="2288442299-20">}</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="2288442299-12">]</span><span class="p" data-group-id="2288442299-11">}</span><span class="p" data-group-id="2288442299-10">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2288442299-1">}</span><span class="p">.</span></code></pre><p>As stated earlier, the order of the instructions is important. When upgrading,
│ │ │  <code class="inline">m1</code> must be loaded, and the supervisor child specification changed, before the
│ │ │  new child process can be started. When downgrading, the child process must be
│ │ │  terminated before the child specification is changed and the module is deleted.</p><h2 id="adding-or-deleting-a-module" class="section-heading">
│ │ │    <a href="#adding-or-deleting-a-module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Adding or Deleting a Module</span>
│ │ │  </h2>
│ │ │ -<p><em>Example</em></p><p>A new functional module <code class="inline">m</code> is added to <code class="inline">ch_app</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2009833958-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="2009833958-2">[</span><span class="p" data-group-id="2009833958-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2009833958-4">[</span><span class="p" data-group-id="2009833958-5">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="2009833958-5">}</span><span class="p" data-group-id="2009833958-4">]</span><span class="p" data-group-id="2009833958-3">}</span><span class="p" data-group-id="2009833958-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="2009833958-6">[</span><span class="p" data-group-id="2009833958-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2009833958-8">[</span><span class="p" data-group-id="2009833958-9">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="2009833958-9">}</span><span class="p" data-group-id="2009833958-8">]</span><span class="p" data-group-id="2009833958-7">}</span><span class="p" data-group-id="2009833958-6">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2009833958-1">}</span><span class="p">.</span></code></pre><h2 id="starting-or-terminating-a-process" class="section-heading">
│ │ │ +<p><em>Example</em></p><p>A new functional module <code class="inline">m</code> is added to <code class="inline">ch_app</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7335933225-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7335933225-2">[</span><span class="p" data-group-id="7335933225-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7335933225-4">[</span><span class="p" data-group-id="7335933225-5">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="7335933225-5">}</span><span class="p" data-group-id="7335933225-4">]</span><span class="p" data-group-id="7335933225-3">}</span><span class="p" data-group-id="7335933225-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7335933225-6">[</span><span class="p" data-group-id="7335933225-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7335933225-8">[</span><span class="p" data-group-id="7335933225-9">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="7335933225-9">}</span><span class="p" data-group-id="7335933225-8">]</span><span class="p" data-group-id="7335933225-7">}</span><span class="p" data-group-id="7335933225-6">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7335933225-1">}</span><span class="p">.</span></code></pre><h2 id="starting-or-terminating-a-process" class="section-heading">
│ │ │    <a href="#starting-or-terminating-a-process" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Starting or Terminating a Process</span>
│ │ │  </h2>
│ │ │  <p>In a system structured according to the OTP design principles, any process would
│ │ │  be a child process belonging to a supervisor, see
│ │ │ @@ -370,29 +370,29 @@
│ │ │    <span class="text">Restarting an Application</span>
│ │ │  </h2>
│ │ │  <p>Restarting an application is useful when a change is too complicated to be made
│ │ │  without restarting the processes, for example, if the supervisor hierarchy has
│ │ │  been restructured.</p><p><em>Example</em></p><p>When adding a child <code class="inline">m1</code> to <code class="inline">ch_sup</code>, as in
│ │ │  <a href="appup_cookbook.html#sup_add">Adding and Deleting Child Processes</a> in Changing a
│ │ │  Supervisor, an alternative to updating the supervisor is to restart the entire
│ │ │ -application:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5721458222-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5721458222-2">[</span><span class="p" data-group-id="5721458222-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5721458222-4">[</span><span class="p" data-group-id="5721458222-5">{</span><span class="ss">restart_application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p" data-group-id="5721458222-5">}</span><span class="p" data-group-id="5721458222-4">]</span><span class="p" data-group-id="5721458222-3">}</span><span class="p" data-group-id="5721458222-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5721458222-6">[</span><span class="p" data-group-id="5721458222-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5721458222-8">[</span><span class="p" data-group-id="5721458222-9">{</span><span class="ss">restart_application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p" data-group-id="5721458222-9">}</span><span class="p" data-group-id="5721458222-8">]</span><span class="p" data-group-id="5721458222-7">}</span><span class="p" data-group-id="5721458222-6">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5721458222-1">}</span><span class="p">.</span></code></pre><p><a href="" id="app_spec"></a></p><h2 id="changing-an-application-specification" class="section-heading">
│ │ │ +application:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4287840161-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4287840161-2">[</span><span class="p" data-group-id="4287840161-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4287840161-4">[</span><span class="p" data-group-id="4287840161-5">{</span><span class="ss">restart_application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p" data-group-id="4287840161-5">}</span><span class="p" data-group-id="4287840161-4">]</span><span class="p" data-group-id="4287840161-3">}</span><span class="p" data-group-id="4287840161-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4287840161-6">[</span><span class="p" data-group-id="4287840161-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4287840161-8">[</span><span class="p" data-group-id="4287840161-9">{</span><span class="ss">restart_application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p" data-group-id="4287840161-9">}</span><span class="p" data-group-id="4287840161-8">]</span><span class="p" data-group-id="4287840161-7">}</span><span class="p" data-group-id="4287840161-6">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4287840161-1">}</span><span class="p">.</span></code></pre><p><a href="" id="app_spec"></a></p><h2 id="changing-an-application-specification" class="section-heading">
│ │ │    <a href="#changing-an-application-specification" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing an Application Specification</span>
│ │ │  </h2>
│ │ │  <p>When installing a release, the application specifications are automatically
│ │ │  updated before evaluating the <code class="inline">relup</code> script. Thus, no instructions are needed
│ │ │ -in the <code class="inline">.appup</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2820659927-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="2820659927-2">[</span><span class="p" data-group-id="2820659927-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2820659927-4">[</span><span class="p" data-group-id="2820659927-4">]</span><span class="p" data-group-id="2820659927-3">}</span><span class="p" data-group-id="2820659927-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="2820659927-5">[</span><span class="p" data-group-id="2820659927-6">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2820659927-7">[</span><span class="p" data-group-id="2820659927-7">]</span><span class="p" data-group-id="2820659927-6">}</span><span class="p" data-group-id="2820659927-5">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2820659927-1">}</span><span class="p">.</span></code></pre><h2 id="changing-application-configuration" class="section-heading">
│ │ │ +in the <code class="inline">.appup</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9337427073-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9337427073-2">[</span><span class="p" data-group-id="9337427073-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9337427073-4">[</span><span class="p" data-group-id="9337427073-4">]</span><span class="p" data-group-id="9337427073-3">}</span><span class="p" data-group-id="9337427073-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9337427073-5">[</span><span class="p" data-group-id="9337427073-6">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9337427073-7">[</span><span class="p" data-group-id="9337427073-7">]</span><span class="p" data-group-id="9337427073-6">}</span><span class="p" data-group-id="9337427073-5">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9337427073-1">}</span><span class="p">.</span></code></pre><h2 id="changing-application-configuration" class="section-heading">
│ │ │    <a href="#changing-application-configuration" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing Application Configuration</span>
│ │ │  </h2>
│ │ │  <p>Changing an application configuration by updating the <code class="inline">env</code> key in the <code class="inline">.app</code>
│ │ │  file is an instance of changing an application specification, see the previous
│ │ │ @@ -407,26 +407,26 @@
│ │ │  applications apply to primary applications only. There are no corresponding
│ │ │  instructions for included applications. However, since an included application
│ │ │  is really a supervision tree with a topmost supervisor, started as a child
│ │ │  process to a supervisor in the including application, a <code class="inline">.relup</code> file can be
│ │ │  manually created.</p><p><em>Example</em></p><p>Assume there is a release containing an application <code class="inline">prim_app</code>, which
│ │ │  has a supervisor <code class="inline">prim_sup</code> in its supervision tree.</p><p>In a new version of the release, the application <code class="inline">ch_app</code> is to be included in
│ │ │  <code class="inline">prim_app</code>. That is, its topmost supervisor <code class="inline">ch_sup</code> is to be started as a child
│ │ │ -process to <code class="inline">prim_sup</code>.</p><p>The workflow is as follows:</p><p><em>Step 1)</em> Edit the code for <code class="inline">prim_sup</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="7653133747-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7653133747-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7653133747-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7653133747-3">{</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="ss">supervisor</span><span class="w"> </span><span class="ss">flags</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="p" data-group-id="7653133747-4">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -           </span><span class="p" data-group-id="7653133747-5">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7653133747-6">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">start_link</span><span class="p">,</span><span class="p" data-group-id="7653133747-7">[</span><span class="p" data-group-id="7653133747-7">]</span><span class="p" data-group-id="7653133747-6">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="ss">permanent</span><span class="p">,</span><span class="ss">infinity</span><span class="p">,</span><span class="ss">supervisor</span><span class="p">,</span><span class="p" data-group-id="7653133747-8">[</span><span class="ss">ch_sup</span><span class="p" data-group-id="7653133747-8">]</span><span class="p" data-group-id="7653133747-5">}</span><span class="p">,</span><span class="w">
│ │ │ -           </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7653133747-4">]</span><span class="p" data-group-id="7653133747-3">}</span><span class="p" data-group-id="7653133747-2">}</span><span class="p">.</span></code></pre><p><em>Step 2)</em> Edit the <code class="inline">.app</code> file for <code class="inline">prim_app</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4765397764-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="4765397764-2">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="4765397764-3">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="4765397764-3">}</span><span class="p">,</span><span class="w">
│ │ │ +process to <code class="inline">prim_sup</code>.</p><p>The workflow is as follows:</p><p><em>Step 1)</em> Edit the code for <code class="inline">prim_sup</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="2918567798-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2918567798-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2918567798-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2918567798-3">{</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="ss">supervisor</span><span class="w"> </span><span class="ss">flags</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ +          </span><span class="p" data-group-id="2918567798-4">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ +           </span><span class="p" data-group-id="2918567798-5">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2918567798-6">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">start_link</span><span class="p">,</span><span class="p" data-group-id="2918567798-7">[</span><span class="p" data-group-id="2918567798-7">]</span><span class="p" data-group-id="2918567798-6">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="ss">permanent</span><span class="p">,</span><span class="ss">infinity</span><span class="p">,</span><span class="ss">supervisor</span><span class="p">,</span><span class="p" data-group-id="2918567798-8">[</span><span class="ss">ch_sup</span><span class="p" data-group-id="2918567798-8">]</span><span class="p" data-group-id="2918567798-5">}</span><span class="p">,</span><span class="w">
│ │ │ +           </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2918567798-4">]</span><span class="p" data-group-id="2918567798-3">}</span><span class="p" data-group-id="2918567798-2">}</span><span class="p">.</span></code></pre><p><em>Step 2)</em> Edit the <code class="inline">.app</code> file for <code class="inline">prim_app</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1646719564-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="1646719564-2">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1646719564-3">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="1646719564-3">}</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="4765397764-4">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4765397764-5">[</span><span class="ss">ch_app</span><span class="p" data-group-id="4765397764-5">]</span><span class="p" data-group-id="4765397764-4">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1646719564-4">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1646719564-5">[</span><span class="ss">ch_app</span><span class="p" data-group-id="1646719564-5">]</span><span class="p" data-group-id="1646719564-4">}</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="4765397764-2">]</span><span class="p" data-group-id="4765397764-1">}</span><span class="p">.</span></code></pre><p><em>Step 3)</em> Create a new <code class="inline">.rel</code> file, including <code class="inline">ch_app</code>:</p><pre><code class="text">{release,
│ │ │ + </span><span class="p" data-group-id="1646719564-2">]</span><span class="p" data-group-id="1646719564-1">}</span><span class="p">.</span></code></pre><p><em>Step 3)</em> Create a new <code class="inline">.rel</code> file, including <code class="inline">ch_app</code>:</p><pre><code class="text">{release,
│ │ │   ...,
│ │ │   [...,
│ │ │    {prim_app, &quot;2&quot;},
│ │ │    {ch_app, &quot;1&quot;}]}.</code></pre><p>The included application can be started in two ways. This is described in the
│ │ │  next two sections.</p><h3 id="application-restart" class="section-heading">
│ │ │    <a href="#application-restart" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -481,74 +481,74 @@
│ │ │  <p><em>Step 4b)</em> Another way to start the included application (or stop it in the case
│ │ │  of downgrade) is by combining instructions for adding and removing child
│ │ │  processes to/from <code class="inline">prim_sup</code> with instructions for loading/unloading all
│ │ │  <code class="inline">ch_app</code> code and its application specification.</p><p>Again, the <code class="inline">.relup</code> file is created manually, either from scratch or by editing a
│ │ │  generated version. Load all code for <code class="inline">ch_app</code> first, and also load the
│ │ │  application specification, before <code class="inline">prim_sup</code> is updated. When downgrading,
│ │ │  <code class="inline">prim_sup</code> is to be updated first, before the code for <code class="inline">ch_app</code> and its application
│ │ │ -specification are unloaded.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4766321838-1">{</span><span class="s">&quot;B&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="4766321838-2">[</span><span class="p" data-group-id="4766321838-3">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="4766321838-4">[</span><span class="p" data-group-id="4766321838-4">]</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="4766321838-5">[</span><span class="p" data-group-id="4766321838-6">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="4766321838-7">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="p" data-group-id="4766321838-8">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">ch3</span><span class="p" data-group-id="4766321838-8">]</span><span class="p" data-group-id="4766321838-7">}</span><span class="p" data-group-id="4766321838-6">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-9">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="4766321838-10">{</span><span class="ss">prim_app</span><span class="p">,</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="p" data-group-id="4766321838-11">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="4766321838-11">]</span><span class="p" data-group-id="4766321838-10">}</span><span class="p" data-group-id="4766321838-9">}</span><span class="p">,</span><span class="w">
│ │ │ +specification are unloaded.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3913903578-1">{</span><span class="s">&quot;B&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="3913903578-2">[</span><span class="p" data-group-id="3913903578-3">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="3913903578-4">[</span><span class="p" data-group-id="3913903578-4">]</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="3913903578-5">[</span><span class="p" data-group-id="3913903578-6">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="3913903578-7">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="p" data-group-id="3913903578-8">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">ch3</span><span class="p" data-group-id="3913903578-8">]</span><span class="p" data-group-id="3913903578-7">}</span><span class="p" data-group-id="3913903578-6">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-9">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="3913903578-10">{</span><span class="ss">prim_app</span><span class="p">,</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="p" data-group-id="3913903578-11">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="3913903578-11">]</span><span class="p" data-group-id="3913903578-10">}</span><span class="p" data-group-id="3913903578-9">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">point_of_no_return</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-12">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="4766321838-13">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="4766321838-13">}</span><span class="p" data-group-id="4766321838-12">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-14">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="4766321838-15">{</span><span class="ss">ch3</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="4766321838-15">}</span><span class="p" data-group-id="4766321838-14">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-16">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="4766321838-17">{</span><span class="ss">application</span><span class="p">,</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="4766321838-18">[</span><span class="ss">ch_app</span><span class="p" data-group-id="4766321838-18">]</span><span class="p" data-group-id="4766321838-17">}</span><span class="p" data-group-id="4766321838-16">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-19">{</span><span class="ss">suspend</span><span class="p">,</span><span class="p" data-group-id="4766321838-20">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="4766321838-20">]</span><span class="p" data-group-id="4766321838-19">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-21">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="4766321838-22">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="4766321838-22">}</span><span class="p" data-group-id="4766321838-21">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-23">{</span><span class="ss">code_change</span><span class="p">,</span><span class="ss">up</span><span class="p">,</span><span class="p" data-group-id="4766321838-24">[</span><span class="p" data-group-id="4766321838-25">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="p" data-group-id="4766321838-26">[</span><span class="p" data-group-id="4766321838-26">]</span><span class="p" data-group-id="4766321838-25">}</span><span class="p" data-group-id="4766321838-24">]</span><span class="p" data-group-id="4766321838-23">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-27">{</span><span class="ss">resume</span><span class="p">,</span><span class="p" data-group-id="4766321838-28">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="4766321838-28">]</span><span class="p" data-group-id="4766321838-27">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-29">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="4766321838-30">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">restart_child</span><span class="p">,</span><span class="p" data-group-id="4766321838-31">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="4766321838-31">]</span><span class="p" data-group-id="4766321838-30">}</span><span class="p" data-group-id="4766321838-29">}</span><span class="p" data-group-id="4766321838-5">]</span><span class="p" data-group-id="4766321838-3">}</span><span class="p" data-group-id="4766321838-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="4766321838-32">[</span><span class="p" data-group-id="4766321838-33">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="4766321838-34">[</span><span class="p" data-group-id="4766321838-34">]</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="4766321838-35">[</span><span class="p" data-group-id="4766321838-36">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="4766321838-37">{</span><span class="ss">prim_app</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="p" data-group-id="4766321838-38">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="4766321838-38">]</span><span class="p" data-group-id="4766321838-37">}</span><span class="p" data-group-id="4766321838-36">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-12">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="3913903578-13">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="3913903578-13">}</span><span class="p" data-group-id="3913903578-12">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-14">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="3913903578-15">{</span><span class="ss">ch3</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="3913903578-15">}</span><span class="p" data-group-id="3913903578-14">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-16">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="3913903578-17">{</span><span class="ss">application</span><span class="p">,</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="3913903578-18">[</span><span class="ss">ch_app</span><span class="p" data-group-id="3913903578-18">]</span><span class="p" data-group-id="3913903578-17">}</span><span class="p" data-group-id="3913903578-16">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-19">{</span><span class="ss">suspend</span><span class="p">,</span><span class="p" data-group-id="3913903578-20">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="3913903578-20">]</span><span class="p" data-group-id="3913903578-19">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-21">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="3913903578-22">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="3913903578-22">}</span><span class="p" data-group-id="3913903578-21">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-23">{</span><span class="ss">code_change</span><span class="p">,</span><span class="ss">up</span><span class="p">,</span><span class="p" data-group-id="3913903578-24">[</span><span class="p" data-group-id="3913903578-25">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="p" data-group-id="3913903578-26">[</span><span class="p" data-group-id="3913903578-26">]</span><span class="p" data-group-id="3913903578-25">}</span><span class="p" data-group-id="3913903578-24">]</span><span class="p" data-group-id="3913903578-23">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-27">{</span><span class="ss">resume</span><span class="p">,</span><span class="p" data-group-id="3913903578-28">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="3913903578-28">]</span><span class="p" data-group-id="3913903578-27">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-29">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="3913903578-30">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">restart_child</span><span class="p">,</span><span class="p" data-group-id="3913903578-31">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="3913903578-31">]</span><span class="p" data-group-id="3913903578-30">}</span><span class="p" data-group-id="3913903578-29">}</span><span class="p" data-group-id="3913903578-5">]</span><span class="p" data-group-id="3913903578-3">}</span><span class="p" data-group-id="3913903578-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="3913903578-32">[</span><span class="p" data-group-id="3913903578-33">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="3913903578-34">[</span><span class="p" data-group-id="3913903578-34">]</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="3913903578-35">[</span><span class="p" data-group-id="3913903578-36">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="3913903578-37">{</span><span class="ss">prim_app</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="p" data-group-id="3913903578-38">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="3913903578-38">]</span><span class="p" data-group-id="3913903578-37">}</span><span class="p" data-group-id="3913903578-36">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">point_of_no_return</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-39">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="4766321838-40">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">terminate_child</span><span class="p">,</span><span class="p" data-group-id="4766321838-41">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="4766321838-41">]</span><span class="p" data-group-id="4766321838-40">}</span><span class="p" data-group-id="4766321838-39">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-42">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="4766321838-43">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">delete_child</span><span class="p">,</span><span class="p" data-group-id="4766321838-44">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="4766321838-44">]</span><span class="p" data-group-id="4766321838-43">}</span><span class="p" data-group-id="4766321838-42">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-45">{</span><span class="ss">suspend</span><span class="p">,</span><span class="p" data-group-id="4766321838-46">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="4766321838-46">]</span><span class="p" data-group-id="4766321838-45">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-47">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="4766321838-48">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="4766321838-48">}</span><span class="p" data-group-id="4766321838-47">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-49">{</span><span class="ss">code_change</span><span class="p">,</span><span class="ss">down</span><span class="p">,</span><span class="p" data-group-id="4766321838-50">[</span><span class="p" data-group-id="4766321838-51">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="p" data-group-id="4766321838-52">[</span><span class="p" data-group-id="4766321838-52">]</span><span class="p" data-group-id="4766321838-51">}</span><span class="p" data-group-id="4766321838-50">]</span><span class="p" data-group-id="4766321838-49">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-53">{</span><span class="ss">resume</span><span class="p">,</span><span class="p" data-group-id="4766321838-54">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="4766321838-54">]</span><span class="p" data-group-id="4766321838-53">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-55">{</span><span class="ss">remove</span><span class="p">,</span><span class="p" data-group-id="4766321838-56">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="4766321838-56">}</span><span class="p" data-group-id="4766321838-55">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-57">{</span><span class="ss">remove</span><span class="p">,</span><span class="p" data-group-id="4766321838-58">{</span><span class="ss">ch3</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="4766321838-58">}</span><span class="p" data-group-id="4766321838-57">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-59">{</span><span class="ss">purge</span><span class="p">,</span><span class="p" data-group-id="4766321838-60">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">ch3</span><span class="p" data-group-id="4766321838-60">]</span><span class="p" data-group-id="4766321838-59">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4766321838-61">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="4766321838-62">{</span><span class="ss">application</span><span class="p">,</span><span class="ss">unload</span><span class="p">,</span><span class="p" data-group-id="4766321838-63">[</span><span class="ss">ch_app</span><span class="p" data-group-id="4766321838-63">]</span><span class="p" data-group-id="4766321838-62">}</span><span class="p" data-group-id="4766321838-61">}</span><span class="p" data-group-id="4766321838-35">]</span><span class="p" data-group-id="4766321838-33">}</span><span class="p" data-group-id="4766321838-32">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4766321838-1">}</span><span class="p">.</span></code></pre><h2 id="changing-non-erlang-code" class="section-heading">
│ │ │ +    </span><span class="p" data-group-id="3913903578-39">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="3913903578-40">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">terminate_child</span><span class="p">,</span><span class="p" data-group-id="3913903578-41">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="3913903578-41">]</span><span class="p" data-group-id="3913903578-40">}</span><span class="p" data-group-id="3913903578-39">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-42">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="3913903578-43">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">delete_child</span><span class="p">,</span><span class="p" data-group-id="3913903578-44">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="3913903578-44">]</span><span class="p" data-group-id="3913903578-43">}</span><span class="p" data-group-id="3913903578-42">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-45">{</span><span class="ss">suspend</span><span class="p">,</span><span class="p" data-group-id="3913903578-46">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="3913903578-46">]</span><span class="p" data-group-id="3913903578-45">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-47">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="3913903578-48">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="3913903578-48">}</span><span class="p" data-group-id="3913903578-47">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-49">{</span><span class="ss">code_change</span><span class="p">,</span><span class="ss">down</span><span class="p">,</span><span class="p" data-group-id="3913903578-50">[</span><span class="p" data-group-id="3913903578-51">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="p" data-group-id="3913903578-52">[</span><span class="p" data-group-id="3913903578-52">]</span><span class="p" data-group-id="3913903578-51">}</span><span class="p" data-group-id="3913903578-50">]</span><span class="p" data-group-id="3913903578-49">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-53">{</span><span class="ss">resume</span><span class="p">,</span><span class="p" data-group-id="3913903578-54">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="3913903578-54">]</span><span class="p" data-group-id="3913903578-53">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-55">{</span><span class="ss">remove</span><span class="p">,</span><span class="p" data-group-id="3913903578-56">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="3913903578-56">}</span><span class="p" data-group-id="3913903578-55">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-57">{</span><span class="ss">remove</span><span class="p">,</span><span class="p" data-group-id="3913903578-58">{</span><span class="ss">ch3</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="3913903578-58">}</span><span class="p" data-group-id="3913903578-57">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-59">{</span><span class="ss">purge</span><span class="p">,</span><span class="p" data-group-id="3913903578-60">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">ch3</span><span class="p" data-group-id="3913903578-60">]</span><span class="p" data-group-id="3913903578-59">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3913903578-61">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="3913903578-62">{</span><span class="ss">application</span><span class="p">,</span><span class="ss">unload</span><span class="p">,</span><span class="p" data-group-id="3913903578-63">[</span><span class="ss">ch_app</span><span class="p" data-group-id="3913903578-63">]</span><span class="p" data-group-id="3913903578-62">}</span><span class="p" data-group-id="3913903578-61">}</span><span class="p" data-group-id="3913903578-35">]</span><span class="p" data-group-id="3913903578-33">}</span><span class="p" data-group-id="3913903578-32">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3913903578-1">}</span><span class="p">.</span></code></pre><h2 id="changing-non-erlang-code" class="section-heading">
│ │ │    <a href="#changing-non-erlang-code" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing Non-Erlang Code</span>
│ │ │  </h2>
│ │ │  <p>Changing code for a program written in another programming language than Erlang,
│ │ │  for example, a port program, is application-dependent and OTP provides no
│ │ │  special support.</p><p><em>Example</em></p><p>When changing code for a port program, assume that the Erlang process
│ │ │  controlling the port is a <code class="inline">gen_server</code> <code class="inline">portc</code> and that the port is opened in
│ │ │ -the callback function <code class="inline">init/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="0871567142-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0871567142-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +the callback function <code class="inline">init/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="8449440387-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8449440387-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">PortPrg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="0871567142-2">(</span><span class="nc">code</span><span class="p">:</span><span class="nf">priv_dir</span><span class="p" data-group-id="0871567142-3">(</span><span class="n">App</span><span class="p" data-group-id="0871567142-3">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;portc&quot;</span><span class="p" data-group-id="0871567142-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="0871567142-4">(</span><span class="p" data-group-id="0871567142-5">{</span><span class="nb">spawn</span><span class="p">,</span><span class="n">PortPrg</span><span class="p" data-group-id="0871567142-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0871567142-6">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0871567142-6">]</span><span class="p" data-group-id="0871567142-4">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">PortPrg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="8449440387-2">(</span><span class="nc">code</span><span class="p">:</span><span class="nf">priv_dir</span><span class="p" data-group-id="8449440387-3">(</span><span class="n">App</span><span class="p" data-group-id="8449440387-3">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;portc&quot;</span><span class="p" data-group-id="8449440387-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="8449440387-4">(</span><span class="p" data-group-id="8449440387-5">{</span><span class="nb">spawn</span><span class="p">,</span><span class="n">PortPrg</span><span class="p" data-group-id="8449440387-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8449440387-6">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8449440387-6">]</span><span class="p" data-group-id="8449440387-4">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0871567142-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="0871567142-8">{</span><span class="ss">port</span><span class="o">=</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0871567142-8">}</span><span class="p" data-group-id="0871567142-7">}</span><span class="p">.</span></code></pre><p>If the port program is to be updated, the code for the <code class="inline">gen_server</code> can be
│ │ │ +    </span><span class="p" data-group-id="8449440387-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="8449440387-8">{</span><span class="ss">port</span><span class="o">=</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8449440387-8">}</span><span class="p" data-group-id="8449440387-7">}</span><span class="p">.</span></code></pre><p>If the port program is to be updated, the code for the <code class="inline">gen_server</code> can be
│ │ │  extended with a <code class="inline">code_change/3</code> function, which closes the old port and opens a
│ │ │  new port. (If necessary, the <code class="inline">gen_server</code> can first request data that must be
│ │ │ -saved from the port program and pass this data to the new port):</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="2770508108-1">(</span><span class="p">_</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="ss">port</span><span class="p" data-group-id="2770508108-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +saved from the port program and pass this data to the new port):</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="5205674156-1">(</span><span class="p">_</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="ss">port</span><span class="p" data-group-id="5205674156-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">close</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="2770508108-2">{</span><span class="n">Port</span><span class="p">,</span><span class="ss">close</span><span class="p" data-group-id="2770508108-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="5205674156-2">{</span><span class="n">Port</span><span class="p">,</span><span class="ss">close</span><span class="p" data-group-id="5205674156-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">PortPrg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="2770508108-3">(</span><span class="nc">code</span><span class="p">:</span><span class="nf">priv_dir</span><span class="p" data-group-id="2770508108-4">(</span><span class="n">App</span><span class="p" data-group-id="2770508108-4">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;portc&quot;</span><span class="p" data-group-id="2770508108-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="2770508108-5">(</span><span class="p" data-group-id="2770508108-6">{</span><span class="nb">spawn</span><span class="p">,</span><span class="n">PortPrg</span><span class="p" data-group-id="2770508108-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2770508108-7">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2770508108-7">]</span><span class="p" data-group-id="2770508108-5">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2770508108-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="2770508108-9">{</span><span class="ss">port</span><span class="o">=</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2770508108-9">}</span><span class="p" data-group-id="2770508108-8">}</span><span class="p">.</span></code></pre><p>Update the application version number in the <code class="inline">.app</code> file and write an <code class="inline">.appup</code>
│ │ │ -file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1342237486-1">[</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1342237486-2">[</span><span class="p" data-group-id="1342237486-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1342237486-4">[</span><span class="p" data-group-id="1342237486-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">portc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1342237486-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="ss">port</span><span class="p" data-group-id="1342237486-6">}</span><span class="p" data-group-id="1342237486-5">}</span><span class="p" data-group-id="1342237486-4">]</span><span class="p" data-group-id="1342237486-3">}</span><span class="p" data-group-id="1342237486-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1342237486-7">[</span><span class="p" data-group-id="1342237486-8">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1342237486-9">[</span><span class="p" data-group-id="1342237486-10">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">portc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1342237486-11">{</span><span class="ss">advanced</span><span class="p">,</span><span class="ss">port</span><span class="p" data-group-id="1342237486-11">}</span><span class="p" data-group-id="1342237486-10">}</span><span class="p" data-group-id="1342237486-9">]</span><span class="p" data-group-id="1342237486-8">}</span><span class="p" data-group-id="1342237486-7">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1342237486-1">]</span><span class="p">.</span></code></pre><p>Ensure that the <code class="inline">priv</code> directory, where the C program is located, is included in
│ │ │ -the new release package:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="2106285899-1">(</span><span class="s">&quot;my_release&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2106285899-2">[</span><span class="p" data-group-id="2106285899-3">{</span><span class="ss">dirs</span><span class="p">,</span><span class="p" data-group-id="2106285899-4">[</span><span class="ss">priv</span><span class="p" data-group-id="2106285899-4">]</span><span class="p" data-group-id="2106285899-3">}</span><span class="p" data-group-id="2106285899-2">]</span><span class="p" data-group-id="2106285899-1">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="n">PortPrg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5205674156-3">(</span><span class="nc">code</span><span class="p">:</span><span class="nf">priv_dir</span><span class="p" data-group-id="5205674156-4">(</span><span class="n">App</span><span class="p" data-group-id="5205674156-4">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;portc&quot;</span><span class="p" data-group-id="5205674156-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="5205674156-5">(</span><span class="p" data-group-id="5205674156-6">{</span><span class="nb">spawn</span><span class="p">,</span><span class="n">PortPrg</span><span class="p" data-group-id="5205674156-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5205674156-7">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="5205674156-7">]</span><span class="p" data-group-id="5205674156-5">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5205674156-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="5205674156-9">{</span><span class="ss">port</span><span class="o">=</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="5205674156-9">}</span><span class="p" data-group-id="5205674156-8">}</span><span class="p">.</span></code></pre><p>Update the application version number in the <code class="inline">.app</code> file and write an <code class="inline">.appup</code>
│ │ │ +file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8764151548-1">[</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8764151548-2">[</span><span class="p" data-group-id="8764151548-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8764151548-4">[</span><span class="p" data-group-id="8764151548-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">portc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8764151548-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="ss">port</span><span class="p" data-group-id="8764151548-6">}</span><span class="p" data-group-id="8764151548-5">}</span><span class="p" data-group-id="8764151548-4">]</span><span class="p" data-group-id="8764151548-3">}</span><span class="p" data-group-id="8764151548-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8764151548-7">[</span><span class="p" data-group-id="8764151548-8">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8764151548-9">[</span><span class="p" data-group-id="8764151548-10">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">portc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8764151548-11">{</span><span class="ss">advanced</span><span class="p">,</span><span class="ss">port</span><span class="p" data-group-id="8764151548-11">}</span><span class="p" data-group-id="8764151548-10">}</span><span class="p" data-group-id="8764151548-9">]</span><span class="p" data-group-id="8764151548-8">}</span><span class="p" data-group-id="8764151548-7">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8764151548-1">]</span><span class="p">.</span></code></pre><p>Ensure that the <code class="inline">priv</code> directory, where the C program is located, is included in
│ │ │ +the new release package:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="0549220649-1">(</span><span class="s">&quot;my_release&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0549220649-2">[</span><span class="p" data-group-id="0549220649-3">{</span><span class="ss">dirs</span><span class="p">,</span><span class="p" data-group-id="0549220649-4">[</span><span class="ss">priv</span><span class="p" data-group-id="0549220649-4">]</span><span class="p" data-group-id="0549220649-3">}</span><span class="p" data-group-id="0549220649-2">]</span><span class="p" data-group-id="0549220649-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="runtime-system-restart-and-upgrade" class="section-heading">
│ │ │    <a href="#runtime-system-restart-and-upgrade" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Runtime System Restart and Upgrade</span>
│ │ │  </h2>
│ │ │  <p>Two upgrade instructions restart the runtime system:</p><ul><li><p><code class="inline">restart_new_emulator</code></p><p>Intended when ERTS, Kernel, STDLIB, or SASL is upgraded. It is automatically
│ │ │ @@ -556,22 +556,22 @@
│ │ │  executed before all other upgrade instructions. For more information about
│ │ │  this instruction, see restart_new_emulator (Low-Level) in
│ │ │  <a href="release_handling.html#restart_new_emulator_instr">Release Handling Instructions</a>.</p></li><li><p><code class="inline">restart_emulator</code></p><p>Used when a restart of the runtime system is required after all other upgrade
│ │ │  instructions are executed. For more information about this instruction, see
│ │ │  restart_emulator (Low-Level) in
│ │ │  <a href="release_handling.html#restart_emulator_instr">Release Handling Instructions</a>.</p></li></ul><p>If a runtime system restart is necessary and no upgrade instructions are needed,
│ │ │  that is, if the restart itself is enough for the upgraded applications to start
│ │ │ -running the new versions, a simple <code class="inline">.relup</code> file can be created manually:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0713561285-1">{</span><span class="s">&quot;B&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0713561285-2">[</span><span class="p" data-group-id="0713561285-3">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="0713561285-4">[</span><span class="p" data-group-id="0713561285-4">]</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="0713561285-5">[</span><span class="ss">restart_emulator</span><span class="p" data-group-id="0713561285-5">]</span><span class="p" data-group-id="0713561285-3">}</span><span class="p" data-group-id="0713561285-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0713561285-6">[</span><span class="p" data-group-id="0713561285-7">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="0713561285-8">[</span><span class="p" data-group-id="0713561285-8">]</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="0713561285-9">[</span><span class="ss">restart_emulator</span><span class="p" data-group-id="0713561285-9">]</span><span class="p" data-group-id="0713561285-7">}</span><span class="p" data-group-id="0713561285-6">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0713561285-1">}</span><span class="p">.</span></code></pre><p>In this case, the release handler framework with automatic packing and unpacking
│ │ │ +running the new versions, a simple <code class="inline">.relup</code> file can be created manually:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0635469646-1">{</span><span class="s">&quot;B&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0635469646-2">[</span><span class="p" data-group-id="0635469646-3">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="0635469646-4">[</span><span class="p" data-group-id="0635469646-4">]</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="0635469646-5">[</span><span class="ss">restart_emulator</span><span class="p" data-group-id="0635469646-5">]</span><span class="p" data-group-id="0635469646-3">}</span><span class="p" data-group-id="0635469646-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0635469646-6">[</span><span class="p" data-group-id="0635469646-7">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="0635469646-8">[</span><span class="p" data-group-id="0635469646-8">]</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="0635469646-9">[</span><span class="ss">restart_emulator</span><span class="p" data-group-id="0635469646-9">]</span><span class="p" data-group-id="0635469646-7">}</span><span class="p" data-group-id="0635469646-6">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0635469646-1">}</span><span class="p">.</span></code></pre><p>In this case, the release handler framework with automatic packing and unpacking
│ │ │  of release packages, automatic path updates, and so on, can be used without
│ │ │  having to specify <code class="inline">.appup</code> files.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/benchmarking.html
│ │ │ @@ -144,16 +144,16 @@
│ │ │  fast as possible, what can we do? One way could be to generate more
│ │ │  than two bytes at a time.</p><pre><code class="text">% erlperf 'rand:bytes(100).' 'crypto:strong_rand_bytes(100).'
│ │ │  Code                                   ||        QPS       Time   Rel
│ │ │  rand:bytes(100).                        1    2124 Ki     470 ns  100%
│ │ │  crypto:strong_rand_bytes(100).          1    1915 Ki     522 ns   90%</code></pre><p><a href="../../lib/stdlib-8.0/doc/html/rand.html#bytes/1"><code class="inline">rand:bytes/1</code></a> is still faster when we generate 100 bytes at a time,
│ │ │  but the relative difference is smaller.</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erlperf &#39;rand:bytes(1000).&#39; &#39;crypto:strong_rand_bytes(1000).&#39;</span><span class="w">
│ │ │  </span><span class="n">Code</span><span class="w">                                    </span><span class="p">||</span><span class="w">        </span><span class="n">QPS</span><span class="w">       </span><span class="n">Time</span><span class="w">   </span><span class="n">Rel</span><span class="w">
│ │ │ -</span><span class="nc">crypto</span><span class="p">:</span><span class="nf">strong_rand_bytes</span><span class="p" data-group-id="4435151142-1">(</span><span class="mi">1000</span><span class="p" data-group-id="4435151142-1">)</span><span class="p">.</span><span class="w">          </span><span class="mi">1</span><span class="w">    </span><span class="mi">1518</span><span class="w"> </span><span class="n">Ki</span><span class="w">     </span><span class="mi">658</span><span class="w"> </span><span class="ss">ns</span><span class="w">  </span><span class="mi">100</span><span class="c1">%</span><span class="w">
│ │ │ -</span><span class="nc">rand</span><span class="p">:</span><span class="nf">bytes</span><span class="p" data-group-id="4435151142-2">(</span><span class="mi">1000</span><span class="p" data-group-id="4435151142-2">)</span><span class="p">.</span><span class="w">                        </span><span class="mi">1</span><span class="w">     </span><span class="mi">284</span><span class="w"> </span><span class="n">Ki</span><span class="w">    </span><span class="mi">3521</span><span class="w"> </span><span class="ss">ns</span><span class="w">   </span><span class="mi">19</span><span class="c1">%</span></code></pre><p>When we generate 1000 bytes at a time, <a href="../../lib/crypto-5.9/doc/html/crypto.html#strong_rand_bytes/1"><code class="inline">crypto:strong_rand_bytes/1</code></a> is
│ │ │ +</span><span class="nc">crypto</span><span class="p">:</span><span class="nf">strong_rand_bytes</span><span class="p" data-group-id="5436661148-1">(</span><span class="mi">1000</span><span class="p" data-group-id="5436661148-1">)</span><span class="p">.</span><span class="w">          </span><span class="mi">1</span><span class="w">    </span><span class="mi">1518</span><span class="w"> </span><span class="n">Ki</span><span class="w">     </span><span class="mi">658</span><span class="w"> </span><span class="ss">ns</span><span class="w">  </span><span class="mi">100</span><span class="c1">%</span><span class="w">
│ │ │ +</span><span class="nc">rand</span><span class="p">:</span><span class="nf">bytes</span><span class="p" data-group-id="5436661148-2">(</span><span class="mi">1000</span><span class="p" data-group-id="5436661148-2">)</span><span class="p">.</span><span class="w">                        </span><span class="mi">1</span><span class="w">     </span><span class="mi">284</span><span class="w"> </span><span class="n">Ki</span><span class="w">    </span><span class="mi">3521</span><span class="w"> </span><span class="ss">ns</span><span class="w">   </span><span class="mi">19</span><span class="c1">%</span></code></pre><p>When we generate 1000 bytes at a time, <a href="../../lib/crypto-5.9/doc/html/crypto.html#strong_rand_bytes/1"><code class="inline">crypto:strong_rand_bytes/1</code></a> is
│ │ │  now the fastest.</p><h2 id="benchmarking-using-erlang-otp-functionality" class="section-heading">
│ │ │    <a href="#benchmarking-using-erlang-otp-functionality" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Benchmarking using Erlang/OTP functionality</span>
│ │ │  </h2>
│ │ │  <p>Benchmarks can measure wall-clock time or CPU time.</p><ul><li><p><a href="../../lib/stdlib-8.0/doc/html/timer.html#tc/3"><code class="inline">timer:tc/3</code></a> measures wall-clock time. The advantage with wall-clock time is
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/binaryhandling.html
│ │ │ @@ -114,43 +114,43 @@
│ │ │  
│ │ │      <span>Constructing and Matching Binaries</span>
│ │ │    </h1>
│ │ │  
│ │ │  <p>This section gives a few examples on how to handle binaries in an efficient way.
│ │ │  The sections that follow take an in-depth look at how binaries are implemented
│ │ │  and how to best take advantage of the optimizations done by the compiler and
│ │ │ -runtime system.</p><p>Binaries can be efficiently <em>built</em> in the following way:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_list_to_binary</span><span class="p" data-group-id="5142521448-1">(</span><span class="n">List</span><span class="p" data-group-id="5142521448-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="5142521448-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5142521448-3">&lt;&lt;</span><span class="p" data-group-id="5142521448-3">&gt;&gt;</span><span class="p" data-group-id="5142521448-2">)</span><span class="p">.</span><span class="w">
│ │ │ +runtime system.</p><p>Binaries can be efficiently <em>built</em> in the following way:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_list_to_binary</span><span class="p" data-group-id="8731589574-1">(</span><span class="n">List</span><span class="p" data-group-id="8731589574-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="8731589574-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8731589574-3">&lt;&lt;</span><span class="p" data-group-id="8731589574-3">&gt;&gt;</span><span class="p" data-group-id="8731589574-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="5142521448-4">(</span><span class="p" data-group-id="5142521448-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5142521448-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5142521448-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="5142521448-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5142521448-7">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="5142521448-7">&gt;&gt;</span><span class="p" data-group-id="5142521448-6">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="5142521448-8">(</span><span class="p" data-group-id="5142521448-9">[</span><span class="p" data-group-id="5142521448-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5142521448-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="8731589574-4">(</span><span class="p" data-group-id="8731589574-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8731589574-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="8731589574-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="8731589574-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8731589574-7">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="8731589574-7">&gt;&gt;</span><span class="p" data-group-id="8731589574-6">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="8731589574-8">(</span><span class="p" data-group-id="8731589574-9">[</span><span class="p" data-group-id="8731589574-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="8731589574-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>Appending data to a binary as in the example is efficient because it is
│ │ │  specially optimized by the runtime system to avoid copying the <code class="inline">Acc</code> binary
│ │ │ -every time.</p><p>Prepending data to a binary in a loop is not efficient:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="4598999885-1">(</span><span class="n">List</span><span class="p" data-group-id="4598999885-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="4598999885-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4598999885-3">&lt;&lt;</span><span class="p" data-group-id="4598999885-3">&gt;&gt;</span><span class="p" data-group-id="4598999885-2">)</span><span class="p">.</span><span class="w">
│ │ │ +every time.</p><p>Prepending data to a binary in a loop is not efficient:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="2748724519-1">(</span><span class="n">List</span><span class="p" data-group-id="2748724519-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="2748724519-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2748724519-3">&lt;&lt;</span><span class="p" data-group-id="2748724519-3">&gt;&gt;</span><span class="p" data-group-id="2748724519-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="4598999885-4">(</span><span class="p" data-group-id="4598999885-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4598999885-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="4598999885-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="4598999885-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4598999885-7">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4598999885-7">&gt;&gt;</span><span class="p" data-group-id="4598999885-6">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="4598999885-8">(</span><span class="p" data-group-id="4598999885-9">[</span><span class="p" data-group-id="4598999885-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="4598999885-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="2748724519-4">(</span><span class="p" data-group-id="2748724519-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2748724519-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2748724519-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="2748724519-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2748724519-7">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2748724519-7">&gt;&gt;</span><span class="p" data-group-id="2748724519-6">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="2748724519-8">(</span><span class="p" data-group-id="2748724519-9">[</span><span class="p" data-group-id="2748724519-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2748724519-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>This is not efficient for long lists because the <code class="inline">Acc</code> binary is copied every
│ │ │ -time. One way to make the function more efficient is like this:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="3599229676-1">(</span><span class="n">List</span><span class="p" data-group-id="3599229676-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="3599229676-2">(</span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="3599229676-3">(</span><span class="n">List</span><span class="p" data-group-id="3599229676-3">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3599229676-4">&lt;&lt;</span><span class="p" data-group-id="3599229676-4">&gt;&gt;</span><span class="p" data-group-id="3599229676-2">)</span><span class="p">.</span><span class="w">
│ │ │ +time. One way to make the function more efficient is like this:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8262081752-1">(</span><span class="n">List</span><span class="p" data-group-id="8262081752-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8262081752-2">(</span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="8262081752-3">(</span><span class="n">List</span><span class="p" data-group-id="8262081752-3">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8262081752-4">&lt;&lt;</span><span class="p" data-group-id="8262081752-4">&gt;&gt;</span><span class="p" data-group-id="8262081752-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="3599229676-5">(</span><span class="p" data-group-id="3599229676-6">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3599229676-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3599229676-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="3599229676-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3599229676-8">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="3599229676-8">&gt;&gt;</span><span class="p" data-group-id="3599229676-7">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="3599229676-9">(</span><span class="p" data-group-id="3599229676-10">[</span><span class="p" data-group-id="3599229676-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3599229676-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>Another way to avoid copying the binary each time is like this:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="2902048872-1">(</span><span class="p" data-group-id="2902048872-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2902048872-2">]</span><span class="p" data-group-id="2902048872-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">RevTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="2902048872-3">(</span><span class="n">T</span><span class="p" data-group-id="2902048872-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2902048872-4">&lt;&lt;</span><span class="n">RevTail</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="2902048872-4">&gt;&gt;</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="2902048872-5">(</span><span class="p" data-group-id="2902048872-6">[</span><span class="p" data-group-id="2902048872-6">]</span><span class="p" data-group-id="2902048872-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2902048872-7">&lt;&lt;</span><span class="p" data-group-id="2902048872-7">&gt;&gt;</span><span class="p">.</span></code></pre><p>Note that in each of the <strong>DO</strong> examples, the binary to be appended to is always
│ │ │ -given as the first segment.</p><p>Binaries can be efficiently <em>matched</em> in the following way:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_binary_to_list</span><span class="p" data-group-id="3322448393-1">(</span><span class="p" data-group-id="3322448393-2">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3322448393-2">&gt;&gt;</span><span class="p" data-group-id="3322448393-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3322448393-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="3322448393-4">(</span><span class="n">T</span><span class="p" data-group-id="3322448393-4">)</span><span class="p" data-group-id="3322448393-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="3322448393-5">(</span><span class="p" data-group-id="3322448393-6">&lt;&lt;</span><span class="p" data-group-id="3322448393-6">&gt;&gt;</span><span class="p" data-group-id="3322448393-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3322448393-7">[</span><span class="p" data-group-id="3322448393-7">]</span><span class="p">.</span></code></pre><h2 id="how-binaries-are-implemented" class="section-heading">
│ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8262081752-5">(</span><span class="p" data-group-id="8262081752-6">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8262081752-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="8262081752-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8262081752-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8262081752-8">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="8262081752-8">&gt;&gt;</span><span class="p" data-group-id="8262081752-7">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8262081752-9">(</span><span class="p" data-group-id="8262081752-10">[</span><span class="p" data-group-id="8262081752-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="8262081752-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>Another way to avoid copying the binary each time is like this:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="5271002810-1">(</span><span class="p" data-group-id="5271002810-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5271002810-2">]</span><span class="p" data-group-id="5271002810-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">RevTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="5271002810-3">(</span><span class="n">T</span><span class="p" data-group-id="5271002810-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5271002810-4">&lt;&lt;</span><span class="n">RevTail</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="5271002810-4">&gt;&gt;</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="5271002810-5">(</span><span class="p" data-group-id="5271002810-6">[</span><span class="p" data-group-id="5271002810-6">]</span><span class="p" data-group-id="5271002810-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5271002810-7">&lt;&lt;</span><span class="p" data-group-id="5271002810-7">&gt;&gt;</span><span class="p">.</span></code></pre><p>Note that in each of the <strong>DO</strong> examples, the binary to be appended to is always
│ │ │ +given as the first segment.</p><p>Binaries can be efficiently <em>matched</em> in the following way:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_binary_to_list</span><span class="p" data-group-id="1104897735-1">(</span><span class="p" data-group-id="1104897735-2">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1104897735-2">&gt;&gt;</span><span class="p" data-group-id="1104897735-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1104897735-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="1104897735-4">(</span><span class="n">T</span><span class="p" data-group-id="1104897735-4">)</span><span class="p" data-group-id="1104897735-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="1104897735-5">(</span><span class="p" data-group-id="1104897735-6">&lt;&lt;</span><span class="p" data-group-id="1104897735-6">&gt;&gt;</span><span class="p" data-group-id="1104897735-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1104897735-7">[</span><span class="p" data-group-id="1104897735-7">]</span><span class="p">.</span></code></pre><h2 id="how-binaries-are-implemented" class="section-heading">
│ │ │    <a href="#how-binaries-are-implemented" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">How Binaries are Implemented</span>
│ │ │  </h2>
│ │ │  <p>Internally, binaries and bitstrings are implemented in the same way. In this
│ │ │  section, they are called <em>binaries</em> because that is what they are called in the
│ │ │ @@ -205,29 +205,29 @@
│ │ │  called referential transparency) of Erlang would break.</p><h2 id="constructing-binaries" class="section-heading">
│ │ │    <a href="#constructing-binaries" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Constructing Binaries</span>
│ │ │  </h2>
│ │ │  <p>Appending to a binary or bitstring in the following way is specially optimized
│ │ │ -to avoid copying the binary:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0258569704-1">&lt;&lt;</span><span class="n">Binary</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0258569704-1">&gt;&gt;</span><span class="w">
│ │ │ +to avoid copying the binary:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7950625738-1">&lt;&lt;</span><span class="n">Binary</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7950625738-1">&gt;&gt;</span><span class="w">
│ │ │  </span><span class="c1">%% - OR -</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0258569704-2">&lt;&lt;</span><span class="n">Binary</span><span class="o">/</span><span class="ss">bitstring</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0258569704-2">&gt;&gt;</span></code></pre><p>This optimization is applied by the runtime system in a way that makes it
│ │ │ +</span><span class="p" data-group-id="7950625738-2">&lt;&lt;</span><span class="n">Binary</span><span class="o">/</span><span class="ss">bitstring</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7950625738-2">&gt;&gt;</span></code></pre><p>This optimization is applied by the runtime system in a way that makes it
│ │ │  effective in most circumstances (for exceptions, see
│ │ │  <a href="binaryhandling.html#forced_copying">Circumstances That Force Copying</a>). The
│ │ │  optimization in its basic form does not need any help from the compiler.
│ │ │  However, the compiler adds hints to the runtime system when it is safe to apply
│ │ │  the optimization in a more efficient way.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>The compiler support for making the optimization more efficient was added in
│ │ │  Erlang/OTP 26.</p></section><p>To explain how the basic optimization works, let us examine the following code
│ │ │ -line by line:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5676449043-1">&lt;&lt;</span><span class="mi">0</span><span class="p" data-group-id="5676449043-1">&gt;&gt;</span><span class="p">,</span><span class="w">                    </span><span class="c1">%% 1</span><span class="w">
│ │ │ -</span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5676449043-2">&lt;&lt;</span><span class="n">Bin0</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5676449043-2">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 2</span><span class="w">
│ │ │ -</span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5676449043-3">&lt;&lt;</span><span class="n">Bin1</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="5676449043-3">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 3</span><span class="w">
│ │ │ -</span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5676449043-4">&lt;&lt;</span><span class="n">Bin2</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p" data-group-id="5676449043-4">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 4</span><span class="w">
│ │ │ -</span><span class="n">Bin4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5676449043-5">&lt;&lt;</span><span class="n">Bin1</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="5676449043-5">&gt;&gt;</span><span class="p">,</span><span class="w">       </span><span class="c1">%% 5 !!!</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5676449043-6">{</span><span class="n">Bin4</span><span class="p">,</span><span class="n">Bin3</span><span class="p" data-group-id="5676449043-6">}</span><span class="w">                      </span><span class="c1">%% 6</span></code></pre><ul><li><p>Line 1 (marked with the <code class="inline">%% 1</code> comment), assigns a
│ │ │ +line by line:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2441791714-1">&lt;&lt;</span><span class="mi">0</span><span class="p" data-group-id="2441791714-1">&gt;&gt;</span><span class="p">,</span><span class="w">                    </span><span class="c1">%% 1</span><span class="w">
│ │ │ +</span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2441791714-2">&lt;&lt;</span><span class="n">Bin0</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2441791714-2">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 2</span><span class="w">
│ │ │ +</span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2441791714-3">&lt;&lt;</span><span class="n">Bin1</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2441791714-3">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 3</span><span class="w">
│ │ │ +</span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2441791714-4">&lt;&lt;</span><span class="n">Bin2</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p" data-group-id="2441791714-4">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 4</span><span class="w">
│ │ │ +</span><span class="n">Bin4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2441791714-5">&lt;&lt;</span><span class="n">Bin1</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="2441791714-5">&gt;&gt;</span><span class="p">,</span><span class="w">       </span><span class="c1">%% 5 !!!</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2441791714-6">{</span><span class="n">Bin4</span><span class="p">,</span><span class="n">Bin3</span><span class="p" data-group-id="2441791714-6">}</span><span class="w">                      </span><span class="c1">%% 6</span></code></pre><ul><li><p>Line 1 (marked with the <code class="inline">%% 1</code> comment), assigns a
│ │ │  <a href="binaryhandling.html#heap_binary">heap binary</a> to the <code class="inline">Bin0</code> variable.</p></li><li><p>Line 2 is an append operation. As <code class="inline">Bin0</code> has not been involved in an append
│ │ │  operation, a new <a href="binaryhandling.html#refc_binary">refc binary</a> is created and
│ │ │  the contents of <code class="inline">Bin0</code> is copied into it. The <em>ProcBin</em> part of the refc
│ │ │  binary has its size set to the size of the data stored in the binary, while
│ │ │  the binary object has extra space allocated. The size of the binary object is
│ │ │  either twice the size of <code class="inline">Bin1</code> or 256, whichever is larger. In this case it
│ │ │  is 256.</p></li><li><p>Line 3 is more interesting. <code class="inline">Bin1</code> <em>has</em> been used in an append operation, and
│ │ │ @@ -253,23 +253,23 @@
│ │ │  handle an append operation to a heap binary by copying it to a refc binary (line
│ │ │  2), and also handle an append operation to a previous version of the binary by
│ │ │  copying it (line 5). The support for doing that does not come for free. For
│ │ │  example, to make it possible to know when it is necessary to copy the binary,
│ │ │  for every append operation, the runtime system must create a sub binary.</p><p>When the compiler can determine that none of those situations need to be handled
│ │ │  and that the append operation cannot possibly fail, the compiler generates code
│ │ │  that causes the runtime system to apply a more efficient variant of the
│ │ │ -optimization.</p><p><strong>Example:</strong></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4400088480-1">(</span><span class="ss">repack</span><span class="p" data-group-id="4400088480-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4400088480-2">(</span><span class="p" data-group-id="4400088480-3">[</span><span class="ss">repack</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4400088480-3">]</span><span class="p" data-group-id="4400088480-2">)</span><span class="p">.</span><span class="w">
│ │ │ +optimization.</p><p><strong>Example:</strong></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5031429592-1">(</span><span class="ss">repack</span><span class="p" data-group-id="5031429592-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5031429592-2">(</span><span class="p" data-group-id="5031429592-3">[</span><span class="ss">repack</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5031429592-3">]</span><span class="p" data-group-id="5031429592-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">repack</span><span class="p" data-group-id="4400088480-4">(</span><span class="n">Bin</span><span class="p" data-group-id="4400088480-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_binary</span><span class="p" data-group-id="4400088480-5">(</span><span class="n">Bin</span><span class="p" data-group-id="4400088480-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">repack</span><span class="p" data-group-id="4400088480-6">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4400088480-7">&lt;&lt;</span><span class="p" data-group-id="4400088480-7">&gt;&gt;</span><span class="p" data-group-id="4400088480-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">repack</span><span class="p" data-group-id="5031429592-4">(</span><span class="n">Bin</span><span class="p" data-group-id="5031429592-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_binary</span><span class="p" data-group-id="5031429592-5">(</span><span class="n">Bin</span><span class="p" data-group-id="5031429592-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">repack</span><span class="p" data-group-id="5031429592-6">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5031429592-7">&lt;&lt;</span><span class="p" data-group-id="5031429592-7">&gt;&gt;</span><span class="p" data-group-id="5031429592-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">repack</span><span class="p" data-group-id="4400088480-8">(</span><span class="p" data-group-id="4400088480-9">&lt;&lt;</span><span class="n">C</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4400088480-9">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4400088480-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">repack</span><span class="p" data-group-id="4400088480-10">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4400088480-11">&lt;&lt;</span><span class="n">Result</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="4400088480-11">&gt;&gt;</span><span class="p" data-group-id="4400088480-10">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">repack</span><span class="p" data-group-id="4400088480-12">(</span><span class="p" data-group-id="4400088480-13">&lt;&lt;</span><span class="p" data-group-id="4400088480-13">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4400088480-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">repack</span><span class="p" data-group-id="5031429592-8">(</span><span class="p" data-group-id="5031429592-9">&lt;&lt;</span><span class="n">C</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5031429592-9">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5031429592-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">repack</span><span class="p" data-group-id="5031429592-10">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5031429592-11">&lt;&lt;</span><span class="n">Result</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="5031429592-11">&gt;&gt;</span><span class="p" data-group-id="5031429592-10">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">repack</span><span class="p" data-group-id="5031429592-12">(</span><span class="p" data-group-id="5031429592-13">&lt;&lt;</span><span class="p" data-group-id="5031429592-13">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5031429592-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Result</span><span class="p">.</span></code></pre><p>The <code class="inline">repack/2</code> function only keeps a single version of the binary, so there is
│ │ │  never any need to copy the binary. The compiler rewrites the creation of the
│ │ │  empty binary in <code class="inline">repack/1</code> to instead create a refc binary with 256 bytes
│ │ │  already reserved; thus, the append operation in <code class="inline">repack/2</code> never needs to handle
│ │ │  a binary not prepared for appending.</p><p><a href="" id="forced_copying"></a></p><h3 id="circumstances-that-force-copying" class="section-heading">
│ │ │    <a href="#circumstances-that-force-copying" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -281,72 +281,72 @@
│ │ │  reason is that the binary object can be moved (reallocated) during an append
│ │ │  operation, and when that happens, the pointer in the ProcBin must be updated. If
│ │ │  there would be more than one ProcBin pointing to the binary object, it would not
│ │ │  be possible to find and update all of them.</p><p>Therefore, certain operations on a binary mark it so that any future append
│ │ │  operation will be forced to copy the binary. In most cases, the binary object
│ │ │  will be shrunk at the same time to reclaim the extra space allocated for
│ │ │  growing.</p><p>When appending to a binary as follows, only the binary returned from the latest
│ │ │ -append operation will support further cheap append operations:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7622523335-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7622523335-1">&gt;&gt;</span></code></pre><p>In the code fragment in the beginning of this section, appending to <code class="inline">Bin</code> will
│ │ │ +append operation will support further cheap append operations:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3974017635-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3974017635-1">&gt;&gt;</span></code></pre><p>In the code fragment in the beginning of this section, appending to <code class="inline">Bin</code> will
│ │ │  be cheap, while appending to <code class="inline">Bin0</code> will force the creation of a new binary and
│ │ │  copying of the contents of <code class="inline">Bin0</code>.</p><p>If a binary is sent as a message to a process or port, the binary will be shrunk
│ │ │  and any further append operation will copy the binary data into a new binary.
│ │ │  For example, in the following code fragment <code class="inline">Bin1</code> will be copied in the third
│ │ │ -line:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7685888305-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7685888305-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ +line:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6545820802-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6545820802-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="n">PortOrPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Bin1</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7685888305-2">&lt;&lt;</span><span class="n">Bin1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7685888305-2">&gt;&gt;</span><span class="w">  </span><span class="c1">%% Bin1 will be COPIED</span></code></pre><p>The same happens if you insert a binary into an Ets table, send it to a port
│ │ │ +</span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6545820802-2">&lt;&lt;</span><span class="n">Bin1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6545820802-2">&gt;&gt;</span><span class="w">  </span><span class="c1">%% Bin1 will be COPIED</span></code></pre><p>The same happens if you insert a binary into an Ets table, send it to a port
│ │ │  using <a href="../../erts-17.0/doc/html/erlang.html#port_command/2"><code class="inline">erlang:port_command/2</code></a>, or pass it to
│ │ │  <a href="../../erts-17.0/doc/html/erl_nif.html#enif_inspect_binary">enif_inspect_binary</a> in a NIF.</p><p>Matching a binary will also cause it to shrink and the next append operation
│ │ │ -will copy the binary data:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2462561505-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2462561505-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2462561505-2">&lt;&lt;</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="n">Z</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2462561505-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin1</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2462561505-3">&lt;&lt;</span><span class="n">Bin1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2462561505-3">&gt;&gt;</span><span class="w">  </span><span class="c1">%% Bin1 will be COPIED</span></code></pre><p>The reason is that a <a href="binaryhandling.html#match_context">match context</a> contains a
│ │ │ +will copy the binary data:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1205072098-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1205072098-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1205072098-2">&lt;&lt;</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="n">Z</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1205072098-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin1</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1205072098-3">&lt;&lt;</span><span class="n">Bin1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1205072098-3">&gt;&gt;</span><span class="w">  </span><span class="c1">%% Bin1 will be COPIED</span></code></pre><p>The reason is that a <a href="binaryhandling.html#match_context">match context</a> contains a
│ │ │  direct pointer to the binary data.</p><p>If a process simply keeps binaries (either in &quot;loop data&quot; or in the process
│ │ │  dictionary), the garbage collector can eventually shrink the binaries. If only
│ │ │  one such binary is kept, it will not be shrunk. If the process later appends to
│ │ │  a binary that has been shrunk, the binary object will be reallocated to make
│ │ │  place for the data to be appended.</p><h2 id="matching-binaries" class="section-heading">
│ │ │    <a href="#matching-binaries" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Matching Binaries</span>
│ │ │  </h2>
│ │ │ -<p>Let us revisit the example in the beginning of the previous section:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_binary_to_list</span><span class="p" data-group-id="9606807458-1">(</span><span class="p" data-group-id="9606807458-2">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="9606807458-2">&gt;&gt;</span><span class="p" data-group-id="9606807458-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9606807458-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="9606807458-4">(</span><span class="n">T</span><span class="p" data-group-id="9606807458-4">)</span><span class="p" data-group-id="9606807458-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="9606807458-5">(</span><span class="p" data-group-id="9606807458-6">&lt;&lt;</span><span class="p" data-group-id="9606807458-6">&gt;&gt;</span><span class="p" data-group-id="9606807458-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9606807458-7">[</span><span class="p" data-group-id="9606807458-7">]</span><span class="p">.</span></code></pre><p>The first time <code class="inline">my_binary_to_list/1</code> is called, a
│ │ │ +<p>Let us revisit the example in the beginning of the previous section:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_binary_to_list</span><span class="p" data-group-id="1326284192-1">(</span><span class="p" data-group-id="1326284192-2">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1326284192-2">&gt;&gt;</span><span class="p" data-group-id="1326284192-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1326284192-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="1326284192-4">(</span><span class="n">T</span><span class="p" data-group-id="1326284192-4">)</span><span class="p" data-group-id="1326284192-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="1326284192-5">(</span><span class="p" data-group-id="1326284192-6">&lt;&lt;</span><span class="p" data-group-id="1326284192-6">&gt;&gt;</span><span class="p" data-group-id="1326284192-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1326284192-7">[</span><span class="p" data-group-id="1326284192-7">]</span><span class="p">.</span></code></pre><p>The first time <code class="inline">my_binary_to_list/1</code> is called, a
│ │ │  <a href="binaryhandling.html#match_context">match context</a> is created. The match context
│ │ │  points to the first byte of the binary. 1 byte is matched out and the match
│ │ │  context is updated to point to the second byte in the binary.</p><p>At this point it would make sense to create a
│ │ │  <a href="binaryhandling.html#sub_binary">sub binary</a>, but in this particular example the
│ │ │  compiler sees that there will soon be a call to a function (in this case, to
│ │ │  <code class="inline">my_binary_to_list/1</code> itself) that immediately will create a new match context
│ │ │  and discard the sub binary.</p><p>Therefore <code class="inline">my_binary_to_list/1</code> calls itself with the match context instead of
│ │ │  with a sub binary. The instruction that initializes the matching operation
│ │ │  basically does nothing when it sees that it was passed a match context instead
│ │ │  of a binary.</p><p>When the end of the binary is reached and the second clause matches, the match
│ │ │  context will simply be discarded (removed in the next garbage collection, as
│ │ │  there is no longer any reference to it).</p><p>To summarize, <code class="inline">my_binary_to_list/1</code> only needs to create <em>one</em> match context and
│ │ │  no sub binaries.</p><p>Notice that the match context in <code class="inline">my_binary_to_list/1</code> was discarded when the
│ │ │  entire binary had been traversed. What happens if the iteration stops before it
│ │ │ -has reached the end of the binary? Will the optimization still work?</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="6077009301-1">(</span><span class="p" data-group-id="6077009301-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6077009301-2">&gt;&gt;</span><span class="p" data-group-id="6077009301-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +has reached the end of the binary? Will the optimization still work?</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="2965161287-1">(</span><span class="p" data-group-id="2965161287-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2965161287-2">&gt;&gt;</span><span class="p" data-group-id="2965161287-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">T</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="6077009301-3">(</span><span class="p" data-group-id="6077009301-4">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6077009301-4">&gt;&gt;</span><span class="p" data-group-id="6077009301-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">after_zero</span><span class="p" data-group-id="6077009301-5">(</span><span class="n">T</span><span class="p" data-group-id="6077009301-5">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="6077009301-6">(</span><span class="p" data-group-id="6077009301-7">&lt;&lt;</span><span class="p" data-group-id="6077009301-7">&gt;&gt;</span><span class="p" data-group-id="6077009301-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6077009301-8">&lt;&lt;</span><span class="p" data-group-id="6077009301-8">&gt;&gt;</span><span class="p">.</span></code></pre><p>Yes, it will. The compiler will remove the building of the sub binary in the
│ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="2965161287-3">(</span><span class="p" data-group-id="2965161287-4">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2965161287-4">&gt;&gt;</span><span class="p" data-group-id="2965161287-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">after_zero</span><span class="p" data-group-id="2965161287-5">(</span><span class="n">T</span><span class="p" data-group-id="2965161287-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="2965161287-6">(</span><span class="p" data-group-id="2965161287-7">&lt;&lt;</span><span class="p" data-group-id="2965161287-7">&gt;&gt;</span><span class="p" data-group-id="2965161287-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2965161287-8">&lt;&lt;</span><span class="p" data-group-id="2965161287-8">&gt;&gt;</span><span class="p">.</span></code></pre><p>Yes, it will. The compiler will remove the building of the sub binary in the
│ │ │  second clause:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="3020689112-1">(</span><span class="p" data-group-id="3020689112-2">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3020689112-2">&gt;&gt;</span><span class="p" data-group-id="3020689112-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">after_zero</span><span class="p" data-group-id="3020689112-3">(</span><span class="n">T</span><span class="p" data-group-id="3020689112-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>But it will generate code that builds a sub binary in the first clause:</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="8272989607-1">(</span><span class="p" data-group-id="8272989607-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8272989607-2">&gt;&gt;</span><span class="p" data-group-id="8272989607-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="9120408343-1">(</span><span class="p" data-group-id="9120408343-2">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="9120408343-2">&gt;&gt;</span><span class="p" data-group-id="9120408343-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">after_zero</span><span class="p" data-group-id="9120408343-3">(</span><span class="n">T</span><span class="p" data-group-id="9120408343-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>But it will generate code that builds a sub binary in the first clause:</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="9415300768-1">(</span><span class="p" data-group-id="9415300768-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="9415300768-2">&gt;&gt;</span><span class="p" data-group-id="9415300768-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">T</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Therefore, <code class="inline">after_zero/1</code> builds one match context and one sub binary (assuming
│ │ │ -it is passed a binary that contains a zero byte).</p><p>Code like the following will also be optimized:</p><pre><code class="makeup erlang" translate="no"><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="2749344784-1">(</span><span class="n">Buffer</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="2749344784-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2749344784-2">{</span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="2749344784-3">(</span><span class="n">Acc</span><span class="p" data-group-id="2749344784-3">)</span><span class="p">,</span><span class="n">Buffer</span><span class="p" data-group-id="2749344784-2">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="2749344784-4">(</span><span class="p" data-group-id="2749344784-5">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2749344784-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="p" data-group-id="2749344784-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="2749344784-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="2749344784-6">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="2749344784-7">(</span><span class="p" data-group-id="2749344784-8">&lt;&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2749344784-8">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="p" data-group-id="2749344784-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="2749344784-9">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2749344784-10">[</span><span class="n">Byte</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="2749344784-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="2749344784-9">)</span><span class="p">.</span></code></pre><p>The compiler removes building of sub binaries in the second and third clauses,
│ │ │ +it is passed a binary that contains a zero byte).</p><p>Code like the following will also be optimized:</p><pre><code class="makeup erlang" translate="no"><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="4687616765-1">(</span><span class="n">Buffer</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="4687616765-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4687616765-2">{</span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="4687616765-3">(</span><span class="n">Acc</span><span class="p" data-group-id="4687616765-3">)</span><span class="p">,</span><span class="n">Buffer</span><span class="p" data-group-id="4687616765-2">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="4687616765-4">(</span><span class="p" data-group-id="4687616765-5">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4687616765-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="p" data-group-id="4687616765-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="4687616765-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="4687616765-6">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="4687616765-7">(</span><span class="p" data-group-id="4687616765-8">&lt;&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4687616765-8">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="p" data-group-id="4687616765-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="4687616765-9">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4687616765-10">[</span><span class="n">Byte</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="4687616765-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="4687616765-9">)</span><span class="p">.</span></code></pre><p>The compiler removes building of sub binaries in the second and third clauses,
│ │ │  and it adds an instruction to the first clause that converts <code class="inline">Buffer</code> from a
│ │ │  match context to a sub binary (or does nothing if <code class="inline">Buffer</code> is already a binary).</p><p>But in more complicated code, how can one know whether the optimization is
│ │ │  applied or not?</p><p><a href="" id="bin_opt_info"></a></p><h3 id="option-bin_opt_info" class="section-heading">
│ │ │    <a href="#option-bin_opt_info" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Option bin_opt_info</span>
│ │ │ @@ -354,38 +354,38 @@
│ │ │  <p>Use the <code class="inline">bin_opt_info</code> option to have the compiler print a lot of information
│ │ │  about binary optimizations. It can be given either to the compiler or <code class="inline">erlc</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">erlc</span><span class="w"> </span><span class="o">+</span><span class="ss">bin_opt_info</span><span class="w"> </span><span class="n">Mod</span><span class="p">.</span><span class="ss">erl</span></code></pre><p>or passed through an environment variable:</p><pre><code class="makeup erlang" translate="no"><span class="ss">export</span><span class="w"> </span><span class="n">ERL_COMPILER_OPTIONS</span><span class="o">=</span><span class="ss">bin_opt_info</span></code></pre><p>Notice that the <code class="inline">bin_opt_info</code> is not meant to be a permanent option added to
│ │ │  your <code class="inline">Makefile</code>s, because all messages that it generates cannot be eliminated.
│ │ │  Therefore, passing the option through the environment is in most cases the most
│ │ │  practical approach.</p><p>The warnings look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="o">/</span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">60</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">NOT</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">binary</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">returned</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">function</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="o">/</span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">62</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">match</span><span class="w"> </span><span class="ss">context</span><span class="w"> </span><span class="ss">reused</span></code></pre><p>To make it clearer exactly what code the warnings refer to, the warnings in the
│ │ │  following examples are inserted as comments after the clause they refer to, for
│ │ │ -example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="8495816042-1">(</span><span class="p" data-group-id="8495816042-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8495816042-2">&gt;&gt;</span><span class="p" data-group-id="8495816042-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="0518327715-1">(</span><span class="p" data-group-id="0518327715-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0518327715-2">&gt;&gt;</span><span class="p" data-group-id="0518327715-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │           </span><span class="c1">%% BINARY CREATED: binary is returned from the function</span><span class="w">
│ │ │      </span><span class="n">T</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="8495816042-3">(</span><span class="p" data-group-id="8495816042-4">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8495816042-4">&gt;&gt;</span><span class="p" data-group-id="8495816042-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="0518327715-3">(</span><span class="p" data-group-id="0518327715-4">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0518327715-4">&gt;&gt;</span><span class="p" data-group-id="0518327715-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │           </span><span class="c1">%% OPTIMIZED: match context reused</span><span class="w">
│ │ │ -    </span><span class="nf">after_zero</span><span class="p" data-group-id="8495816042-5">(</span><span class="n">T</span><span class="p" data-group-id="8495816042-5">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="8495816042-6">(</span><span class="p" data-group-id="8495816042-7">&lt;&lt;</span><span class="p" data-group-id="8495816042-7">&gt;&gt;</span><span class="p" data-group-id="8495816042-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8495816042-8">&lt;&lt;</span><span class="p" data-group-id="8495816042-8">&gt;&gt;</span><span class="p">.</span></code></pre><p>The warning for the first clause says that the creation of a sub binary cannot
│ │ │ +    </span><span class="nf">after_zero</span><span class="p" data-group-id="0518327715-5">(</span><span class="n">T</span><span class="p" data-group-id="0518327715-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="0518327715-6">(</span><span class="p" data-group-id="0518327715-7">&lt;&lt;</span><span class="p" data-group-id="0518327715-7">&gt;&gt;</span><span class="p" data-group-id="0518327715-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0518327715-8">&lt;&lt;</span><span class="p" data-group-id="0518327715-8">&gt;&gt;</span><span class="p">.</span></code></pre><p>The warning for the first clause says that the creation of a sub binary cannot
│ │ │  be delayed, because it will be returned. The warning for the second clause says
│ │ │  that a sub binary will not be created (yet).</p><h3 id="unused-variables" class="section-heading">
│ │ │    <a href="#unused-variables" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Unused Variables</span>
│ │ │  </h3>
│ │ │  <p>The compiler figures out if a variable is unused. The same code is generated for
│ │ │ -each of the following functions:</p><pre><code class="makeup erlang" translate="no"><span class="nf">count1</span><span class="p" data-group-id="6014030565-1">(</span><span class="p" data-group-id="6014030565-2">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6014030565-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="6014030565-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count1</span><span class="p" data-group-id="6014030565-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="6014030565-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">count1</span><span class="p" data-group-id="6014030565-4">(</span><span class="p" data-group-id="6014030565-5">&lt;&lt;</span><span class="p" data-group-id="6014030565-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="6014030565-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span><span class="w">
│ │ │ +each of the following functions:</p><pre><code class="makeup erlang" translate="no"><span class="nf">count1</span><span class="p" data-group-id="3355520494-1">(</span><span class="p" data-group-id="3355520494-2">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3355520494-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3355520494-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count1</span><span class="p" data-group-id="3355520494-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="3355520494-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">count1</span><span class="p" data-group-id="3355520494-4">(</span><span class="p" data-group-id="3355520494-5">&lt;&lt;</span><span class="p" data-group-id="3355520494-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3355520494-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">count2</span><span class="p" data-group-id="6014030565-6">(</span><span class="p" data-group-id="6014030565-7">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6014030565-7">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="6014030565-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count2</span><span class="p" data-group-id="6014030565-8">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="6014030565-8">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">count2</span><span class="p" data-group-id="6014030565-9">(</span><span class="p" data-group-id="6014030565-10">&lt;&lt;</span><span class="p" data-group-id="6014030565-10">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="6014030565-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">count2</span><span class="p" data-group-id="3355520494-6">(</span><span class="p" data-group-id="3355520494-7">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3355520494-7">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3355520494-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count2</span><span class="p" data-group-id="3355520494-8">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="3355520494-8">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">count2</span><span class="p" data-group-id="3355520494-9">(</span><span class="p" data-group-id="3355520494-10">&lt;&lt;</span><span class="p" data-group-id="3355520494-10">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3355520494-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">count3</span><span class="p" data-group-id="6014030565-11">(</span><span class="p" data-group-id="6014030565-12">&lt;&lt;</span><span class="p">_</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6014030565-12">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="6014030565-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count3</span><span class="p" data-group-id="6014030565-13">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="6014030565-13">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">count3</span><span class="p" data-group-id="6014030565-14">(</span><span class="p" data-group-id="6014030565-15">&lt;&lt;</span><span class="p" data-group-id="6014030565-15">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="6014030565-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span></code></pre><p>In each iteration, the first 8 bits in the binary will be skipped, not matched
│ │ │ +</span><span class="nf">count3</span><span class="p" data-group-id="3355520494-11">(</span><span class="p" data-group-id="3355520494-12">&lt;&lt;</span><span class="p">_</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3355520494-12">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3355520494-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count3</span><span class="p" data-group-id="3355520494-13">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="3355520494-13">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">count3</span><span class="p" data-group-id="3355520494-14">(</span><span class="p" data-group-id="3355520494-15">&lt;&lt;</span><span class="p" data-group-id="3355520494-15">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3355520494-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span></code></pre><p>In each iteration, the first 8 bits in the binary will be skipped, not matched
│ │ │  out.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="commoncaveats.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/bit_syntax.html
│ │ │ @@ -119,48 +119,48 @@
│ │ │    <a href="#introduction" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Introduction</span>
│ │ │  </h2>
│ │ │  <p>The complete specification for the bit syntax appears in the
│ │ │  <a href="../../doc/system/expressions.html#bit-syntax-expressions">Reference Manual</a>.</p><p>In Erlang, a Bin is used for constructing binaries and matching binary patterns.
│ │ │ -A Bin is written with the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4888084731-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="4888084731-1">&gt;&gt;</span></code></pre><p>A Bin is a low-level sequence of bits or bytes. The purpose of a Bin is to
│ │ │ -enable construction of binaries:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2318324204-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="2318324204-1">&gt;&gt;</span></code></pre><p>All elements must be bound. Or match a binary:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1444353553-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="1444353553-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin</span></code></pre><p>Here, <code class="inline">Bin</code> is bound and the elements are bound or unbound, as in any match.</p><p>A Bin does not need to consist of a whole number of bytes.</p><p>A <em>bitstring</em> is a sequence of zero or more bits, where the number of bits does
│ │ │ +A Bin is written with the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7025536755-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="7025536755-1">&gt;&gt;</span></code></pre><p>A Bin is a low-level sequence of bits or bytes. The purpose of a Bin is to
│ │ │ +enable construction of binaries:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0039539952-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="0039539952-1">&gt;&gt;</span></code></pre><p>All elements must be bound. Or match a binary:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3278784139-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="3278784139-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin</span></code></pre><p>Here, <code class="inline">Bin</code> is bound and the elements are bound or unbound, as in any match.</p><p>A Bin does not need to consist of a whole number of bytes.</p><p>A <em>bitstring</em> is a sequence of zero or more bits, where the number of bits does
│ │ │  not need to be divisible by 8. If the number of bits is divisible by 8, the
│ │ │  bitstring is also a binary.</p><p>Each element specifies a certain <em>segment</em> of the bitstring. A segment is a set
│ │ │  of contiguous bits of the binary (not necessarily on a byte boundary). The first
│ │ │  element specifies the initial segment, the second element specifies the
│ │ │  following segment, and so on.</p><p>The following examples illustrate how binaries are constructed, or matched, and
│ │ │  how elements and tails are specified.</p><h3 id="examples" class="section-heading">
│ │ │    <a href="#examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h3>
│ │ │  <p><em>Example 1:</em> A binary can be constructed from a set of constants or a string
│ │ │ -literal:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin11</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7666528213-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">17</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="7666528213-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Bin12</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7666528213-2">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="7666528213-2">&gt;&gt;</span></code></pre><p>This gives two binaries of size 3, with the following evaluations:</p><ul><li><a href="../../erts-17.0/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin11)</code></a> evaluates to <code class="inline">[1, 17, 42]</code>.</li><li><a href="../../erts-17.0/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin12)</code></a> evaluates to <code class="inline">[97, 98, 99]</code>.</li></ul><p><em>Example 2:</em> Similarly, a binary can be constructed from a set of bound
│ │ │ +literal:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin11</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7628803093-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">17</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="7628803093-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Bin12</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7628803093-2">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="7628803093-2">&gt;&gt;</span></code></pre><p>This gives two binaries of size 3, with the following evaluations:</p><ul><li><a href="../../erts-17.0/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin11)</code></a> evaluates to <code class="inline">[1, 17, 42]</code>.</li><li><a href="../../erts-17.0/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin12)</code></a> evaluates to <code class="inline">[97, 98, 99]</code>.</li></ul><p><em>Example 2:</em> Similarly, a binary can be constructed from a set of bound
│ │ │  variables:</p><pre><code class="makeup erlang" translate="no"><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">17</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2167408698-1">&lt;&lt;</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="2167408698-1">&gt;&gt;</span></code></pre><p>This gives a binary of size 4. Here, a <em>size expression</em> is used for the
│ │ │ +</span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3629635716-1">&lt;&lt;</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="3629635716-1">&gt;&gt;</span></code></pre><p>This gives a binary of size 4. Here, a <em>size expression</em> is used for the
│ │ │  variable <code class="inline">C</code> to specify a 16-bit segment of <code class="inline">Bin2</code>.</p><p><a href="../../erts-17.0/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin2)</code></a> evaluates to <code class="inline">[1, 17, 00, 42]</code>.</p><p><em>Example 3:</em> A Bin can also be used for matching. <code class="inline">D</code>, <code class="inline">E</code>, and <code class="inline">F</code> are unbound
│ │ │ -variables, and <code class="inline">Bin2</code> is bound, as in Example 2:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2414578622-1">&lt;&lt;</span><span class="n">D</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2414578622-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin2</span></code></pre><p>This gives <code class="inline">D = 273</code>, <code class="inline">E = 00</code>, and F binds to a binary of size 1:
│ │ │ +variables, and <code class="inline">Bin2</code> is bound, as in Example 2:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7335648927-1">&lt;&lt;</span><span class="n">D</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7335648927-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin2</span></code></pre><p>This gives <code class="inline">D = 273</code>, <code class="inline">E = 00</code>, and F binds to a binary of size 1:
│ │ │  <code class="inline">binary_to_list(F) = [42]</code>.</p><p><em>Example 4:</em> The following is a more elaborate example of matching. Here,
│ │ │  <code class="inline">Dgram</code> is bound to the consecutive bytes of an IP datagram of IP protocol
│ │ │ -version 4. The ambition is to extract the header and the data of the datagram:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2346990973-1">(</span><span class="n">IP_VERSION</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="2346990973-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2346990973-2">(</span><span class="n">IP_MIN_HDR_LEN</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="2346990973-2">)</span><span class="p">.</span><span class="w">
│ │ │ +version 4. The ambition is to extract the header and the data of the datagram:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5668599459-1">(</span><span class="n">IP_VERSION</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="5668599459-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5668599459-2">(</span><span class="n">IP_MIN_HDR_LEN</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="5668599459-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">DgramSize</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">byte_size</span><span class="p" data-group-id="2346990973-3">(</span><span class="n">Dgram</span><span class="p" data-group-id="2346990973-3">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">DgramSize</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">byte_size</span><span class="p" data-group-id="5668599459-3">(</span><span class="n">Dgram</span><span class="p" data-group-id="5668599459-3">)</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="k">case</span><span class="w"> </span><span class="n">Dgram</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2346990973-4">&lt;&lt;</span><span class="o">?</span><span class="n">IP_VERSION</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">HLen</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">SrvcType</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="n">TotLen</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5668599459-4">&lt;&lt;</span><span class="o">?</span><span class="n">IP_VERSION</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">HLen</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">SrvcType</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="n">TotLen</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w">
│ │ │        </span><span class="n">ID</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w"> </span><span class="n">Flgs</span><span class="p">:</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">FragOff</span><span class="p">:</span><span class="mi">13</span><span class="p">,</span><span class="w">
│ │ │        </span><span class="n">TTL</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="n">Proto</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="n">HdrChkSum</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w">
│ │ │        </span><span class="n">SrcIP</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="w">
│ │ │ -      </span><span class="n">DestIP</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="w"> </span><span class="n">RestDgram</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2346990973-4">&gt;&gt;</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">HLen</span><span class="o">&gt;=</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="o">*</span><span class="n">HLen</span><span class="o">=&lt;</span><span class="n">DgramSize</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="n">OptsLen</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">4</span><span class="o">*</span><span class="p" data-group-id="2346990973-5">(</span><span class="n">HLen</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">?</span><span class="n">IP_MIN_HDR_LEN</span><span class="p" data-group-id="2346990973-5">)</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="2346990973-6">&lt;&lt;</span><span class="n">Opts</span><span class="p">:</span><span class="n">OptsLen</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Data</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2346990973-6">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RestDgram</span><span class="p">,</span><span class="w">
│ │ │ +      </span><span class="n">DestIP</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="w"> </span><span class="n">RestDgram</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5668599459-4">&gt;&gt;</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">HLen</span><span class="o">&gt;=</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="o">*</span><span class="n">HLen</span><span class="o">=&lt;</span><span class="n">DgramSize</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="n">OptsLen</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">4</span><span class="o">*</span><span class="p" data-group-id="5668599459-5">(</span><span class="n">HLen</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">?</span><span class="n">IP_MIN_HDR_LEN</span><span class="p" data-group-id="5668599459-5">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="5668599459-6">&lt;&lt;</span><span class="n">Opts</span><span class="p">:</span><span class="n">OptsLen</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Data</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5668599459-6">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RestDgram</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>Here, the segment corresponding to the <code class="inline">Opts</code> variable has a <em>type modifier</em>,
│ │ │  specifying that <code class="inline">Opts</code> is to bind to a binary. All other variables have the
│ │ │  default type equal to unsigned integer.</p><p>An IP datagram header is of variable length. This length is measured in the
│ │ │  number of 32-bit words and is given in the segment corresponding to <code class="inline">HLen</code>. The
│ │ │  minimum value of <code class="inline">HLen</code> is 5. It is the segment corresponding to <code class="inline">Opts</code> that is
│ │ │  variable, so if <code class="inline">HLen</code> is equal to 5, <code class="inline">Opts</code> becomes an empty binary.</p><p>The tail variables <code class="inline">RestDgram</code> and <code class="inline">Data</code> bind to binaries, as all tail
│ │ │ @@ -218,80 +218,80 @@
│ │ │  <p>This section describes the rules for constructing binaries using the bit syntax.
│ │ │  Unlike when constructing lists or tuples, the construction of a binary can fail
│ │ │  with a <code class="inline">badarg</code> exception.</p><p>There can be zero or more segments in a binary to be constructed. The expression
│ │ │  <code class="inline">&lt;&lt;&gt;&gt;</code> constructs a zero length binary.</p><p>Each segment in a binary can consist of zero or more bits. There are no
│ │ │  alignment rules for individual segments of type <code class="inline">integer</code> and <code class="inline">float</code>. For
│ │ │  binaries and bitstrings without size, the unit specifies the alignment. Since
│ │ │  the default alignment for the <code class="inline">binary</code> type is 8, the size of a binary segment
│ │ │ -must be a multiple of 8 bits, that is, only whole bytes.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3240884115-1">&lt;&lt;</span><span class="n">Bin</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Bitstring</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="3240884115-1">&gt;&gt;</span></code></pre><p>The variable <code class="inline">Bin</code> must contain a whole number of bytes, because the <code class="inline">binary</code>
│ │ │ +must be a multiple of 8 bits, that is, only whole bytes.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0838137482-1">&lt;&lt;</span><span class="n">Bin</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Bitstring</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="0838137482-1">&gt;&gt;</span></code></pre><p>The variable <code class="inline">Bin</code> must contain a whole number of bytes, because the <code class="inline">binary</code>
│ │ │  type defaults to <code class="inline">unit:8</code>. A <code class="inline">badarg</code> exception is generated if <code class="inline">Bin</code> consists
│ │ │  of, for example, 17 bits.</p><p>The <code class="inline">Bitstring</code> variable can consist of any number of bits, for example, 0, 1,
│ │ │  8, 11, 17, 42, and so on. This is because the default <code class="inline">unit</code> for bitstrings
│ │ │  is 1.</p><p>For clarity, it is recommended not to change the unit size for binaries.
│ │ │  Instead, use <code class="inline">binary</code> when you need byte alignment and <code class="inline">bitstring</code> when you need
│ │ │  bit alignment.</p><p>The following example successfully constructs a bitstring of 7 bits, provided
│ │ │ -that all of X and Y are integers:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4278511712-1">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="mi">1</span><span class="p">,</span><span class="n">Y</span><span class="p">:</span><span class="mi">6</span><span class="p" data-group-id="4278511712-1">&gt;&gt;</span></code></pre><p>As mentioned earlier, segments have the following general syntax:</p><p><code class="inline">Value:Size/TypeSpecifierList</code></p><p>When constructing binaries, <code class="inline">Value</code> and <code class="inline">Size</code> can be any Erlang expression.
│ │ │ +that all of X and Y are integers:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9618492818-1">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="mi">1</span><span class="p">,</span><span class="n">Y</span><span class="p">:</span><span class="mi">6</span><span class="p" data-group-id="9618492818-1">&gt;&gt;</span></code></pre><p>As mentioned earlier, segments have the following general syntax:</p><p><code class="inline">Value:Size/TypeSpecifierList</code></p><p>When constructing binaries, <code class="inline">Value</code> and <code class="inline">Size</code> can be any Erlang expression.
│ │ │  However, for syntactical reasons, both <code class="inline">Value</code> and <code class="inline">Size</code> must be enclosed in
│ │ │  parentheses if the expression consists of anything more than a single literal or
│ │ │ -a variable. The following gives a compiler syntax error:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1210127907-1">&lt;&lt;</span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="1210127907-1">&gt;&gt;</span></code></pre><p>This expression must be rewritten into the following, to be accepted by the
│ │ │ -compiler:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2677774367-1">&lt;&lt;</span><span class="p" data-group-id="2677774367-2">(</span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="2677774367-2">)</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="2677774367-1">&gt;&gt;</span></code></pre><h3 id="including-literal-strings" class="section-heading">
│ │ │ +a variable. The following gives a compiler syntax error:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6437238308-1">&lt;&lt;</span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="6437238308-1">&gt;&gt;</span></code></pre><p>This expression must be rewritten into the following, to be accepted by the
│ │ │ +compiler:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7409439767-1">&lt;&lt;</span><span class="p" data-group-id="7409439767-2">(</span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="7409439767-2">)</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="7409439767-1">&gt;&gt;</span></code></pre><h3 id="including-literal-strings" class="section-heading">
│ │ │    <a href="#including-literal-strings" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Including Literal Strings</span>
│ │ │  </h3>
│ │ │ -<p>A literal string can be written instead of an element:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4279699865-1">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="4279699865-1">&gt;&gt;</span></code></pre><p>This is syntactic sugar for the following:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0215834791-1">&lt;&lt;</span><span class="sc">$h</span><span class="p">,</span><span class="sc">$e</span><span class="p">,</span><span class="sc">$l</span><span class="p">,</span><span class="sc">$l</span><span class="p">,</span><span class="sc">$o</span><span class="p" data-group-id="0215834791-1">&gt;&gt;</span></code></pre><h2 id="matching-binaries" class="section-heading">
│ │ │ +<p>A literal string can be written instead of an element:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3624566400-1">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="3624566400-1">&gt;&gt;</span></code></pre><p>This is syntactic sugar for the following:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2944972468-1">&lt;&lt;</span><span class="sc">$h</span><span class="p">,</span><span class="sc">$e</span><span class="p">,</span><span class="sc">$l</span><span class="p">,</span><span class="sc">$l</span><span class="p">,</span><span class="sc">$o</span><span class="p" data-group-id="2944972468-1">&gt;&gt;</span></code></pre><h2 id="matching-binaries" class="section-heading">
│ │ │    <a href="#matching-binaries" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Matching Binaries</span>
│ │ │  </h2>
│ │ │  <p>This section describes the rules for matching binaries, using the bit syntax.</p><p>There can be zero or more segments in a binary pattern. A binary pattern can
│ │ │  occur wherever patterns are allowed, including inside other patterns. Binary
│ │ │  patterns cannot be nested. The pattern <code class="inline">&lt;&lt;&gt;&gt;</code> matches a zero length binary.</p><p>Each segment in a binary can consist of zero or more bits. A segment of type
│ │ │  <code class="inline">binary</code> must have a size evenly divisible by 8 (or divisible by the unit size,
│ │ │  if the unit size has been changed). A segment of type <code class="inline">bitstring</code> has no
│ │ │  restrictions on the size. A segment of type <code class="inline">float</code> must have size 64 or 32.</p><p>As mentioned earlier, segments have the following general syntax:</p><p><code class="inline">Value:Size/TypeSpecifierList</code></p><p>When matching <code class="inline">Value</code>, <code class="inline">Value</code> must be either a variable or an integer, or a
│ │ │  floating point literal. Expressions are not allowed.</p><p><code class="inline">Size</code> must be a
│ │ │  <a href="../../doc/system/expressions.html#guard-expressions">guard expression</a>, which can use
│ │ │ -literals and previously bound variables. The following is not allowed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="1059201404-1">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1059201404-2">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">N</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1059201404-2">&gt;&gt;</span><span class="p" data-group-id="1059201404-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="1059201404-3">{</span><span class="n">X</span><span class="p">,</span><span class="n">T</span><span class="p" data-group-id="1059201404-3">}</span><span class="p">.</span></code></pre><p>The two occurrences of <code class="inline">N</code> are not related. The compiler will complain that the
│ │ │ -<code class="inline">N</code> in the size field is unbound.</p><p>The correct way to write this example is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="8549664174-1">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Bin</span><span class="p" data-group-id="8549664174-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="8549664174-2">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">N</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8549664174-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="8549664174-3">{</span><span class="n">X</span><span class="p">,</span><span class="n">T</span><span class="p" data-group-id="8549664174-3">}</span><span class="p">.</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Before OTP 23, <code class="inline">Size</code> was restricted to be an integer or a variable bound to
│ │ │ +literals and previously bound variables. The following is not allowed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="0676445299-1">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0676445299-2">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">N</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0676445299-2">&gt;&gt;</span><span class="p" data-group-id="0676445299-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="0676445299-3">{</span><span class="n">X</span><span class="p">,</span><span class="n">T</span><span class="p" data-group-id="0676445299-3">}</span><span class="p">.</span></code></pre><p>The two occurrences of <code class="inline">N</code> are not related. The compiler will complain that the
│ │ │ +<code class="inline">N</code> in the size field is unbound.</p><p>The correct way to write this example is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="6078827860-1">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Bin</span><span class="p" data-group-id="6078827860-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="6078827860-2">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">N</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6078827860-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="6078827860-3">{</span><span class="n">X</span><span class="p">,</span><span class="n">T</span><span class="p" data-group-id="6078827860-3">}</span><span class="p">.</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Before OTP 23, <code class="inline">Size</code> was restricted to be an integer or a variable bound to
│ │ │  an integer.</p></section><h3 id="binding-and-using-a-size-variable" class="section-heading">
│ │ │    <a href="#binding-and-using-a-size-variable" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Binding and Using a Size Variable</span>
│ │ │  </h3>
│ │ │  <p>There is one exception to the rule that a variable that is used as size must be
│ │ │  previously bound. It is possible to match and bind a variable, and use it as a
│ │ │ -size within the same binary pattern. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="9640400963-1">(</span><span class="p" data-group-id="9640400963-2">&lt;&lt;</span><span class="n">Sz</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Payload</span><span class="p">:</span><span class="n">Sz</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="9640400963-2">&gt;&gt;</span><span class="p" data-group-id="9640400963-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="9640400963-3">{</span><span class="n">Payload</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="9640400963-3">}</span><span class="p">.</span></code></pre><p>Here <code class="inline">Sz</code> is bound to the value in the first byte of the binary. <code class="inline">Sz</code> is then
│ │ │ -used as the number of bytes to match out as a binary.</p><p>Starting in OTP 23, the size can be a guard expression:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="9273629439-1">(</span><span class="p" data-group-id="9273629439-2">&lt;&lt;</span><span class="n">Sz</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Payload</span><span class="p">:</span><span class="p" data-group-id="9273629439-3">(</span><span class="p" data-group-id="9273629439-4">(</span><span class="n">Sz</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="9273629439-4">)</span><span class="o">*</span><span class="mi">8</span><span class="p" data-group-id="9273629439-3">)</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="9273629439-2">&gt;&gt;</span><span class="p" data-group-id="9273629439-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="9273629439-5">{</span><span class="n">Payload</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="9273629439-5">}</span><span class="p">.</span></code></pre><p>Here <code class="inline">Sz</code> is the combined size of the header and the payload, so we will need to
│ │ │ +size within the same binary pattern. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="3285391359-1">(</span><span class="p" data-group-id="3285391359-2">&lt;&lt;</span><span class="n">Sz</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Payload</span><span class="p">:</span><span class="n">Sz</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3285391359-2">&gt;&gt;</span><span class="p" data-group-id="3285391359-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="3285391359-3">{</span><span class="n">Payload</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="3285391359-3">}</span><span class="p">.</span></code></pre><p>Here <code class="inline">Sz</code> is bound to the value in the first byte of the binary. <code class="inline">Sz</code> is then
│ │ │ +used as the number of bytes to match out as a binary.</p><p>Starting in OTP 23, the size can be a guard expression:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="6876195403-1">(</span><span class="p" data-group-id="6876195403-2">&lt;&lt;</span><span class="n">Sz</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Payload</span><span class="p">:</span><span class="p" data-group-id="6876195403-3">(</span><span class="p" data-group-id="6876195403-4">(</span><span class="n">Sz</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="6876195403-4">)</span><span class="o">*</span><span class="mi">8</span><span class="p" data-group-id="6876195403-3">)</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6876195403-2">&gt;&gt;</span><span class="p" data-group-id="6876195403-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="6876195403-5">{</span><span class="n">Payload</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="6876195403-5">}</span><span class="p">.</span></code></pre><p>Here <code class="inline">Sz</code> is the combined size of the header and the payload, so we will need to
│ │ │  subtract one byte to get the size of the payload.</p><h3 id="getting-the-rest-of-the-binary-or-bitstring" class="section-heading">
│ │ │    <a href="#getting-the-rest-of-the-binary-or-bitstring" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Getting the Rest of the Binary or Bitstring</span>
│ │ │  </h3>
│ │ │ -<p>To match out the rest of a binary, specify a binary field without size:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="3894739962-1">(</span><span class="p" data-group-id="3894739962-2">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3894739962-2">&gt;&gt;</span><span class="p" data-group-id="3894739962-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>The size of the tail must be evenly divisible by 8.</p><p>To match out the rest of a bitstring, specify a field without size:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="7293756070-1">(</span><span class="p" data-group-id="7293756070-2">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="7293756070-2">&gt;&gt;</span><span class="p" data-group-id="7293756070-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>There are no restrictions on the number of bits in the tail.</p><h2 id="appending-to-a-binary" class="section-heading">
│ │ │ +<p>To match out the rest of a binary, specify a binary field without size:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="1398990401-1">(</span><span class="p" data-group-id="1398990401-2">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1398990401-2">&gt;&gt;</span><span class="p" data-group-id="1398990401-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>The size of the tail must be evenly divisible by 8.</p><p>To match out the rest of a bitstring, specify a field without size:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="0388288262-1">(</span><span class="p" data-group-id="0388288262-2">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="0388288262-2">&gt;&gt;</span><span class="p" data-group-id="0388288262-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>There are no restrictions on the number of bits in the tail.</p><h2 id="appending-to-a-binary" class="section-heading">
│ │ │    <a href="#appending-to-a-binary" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Appending to a Binary</span>
│ │ │  </h2>
│ │ │ -<p>Appending to a binary in an efficient way can be done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">triples_to_bin</span><span class="p" data-group-id="3764413594-1">(</span><span class="n">T</span><span class="p" data-group-id="3764413594-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">triples_to_bin</span><span class="p" data-group-id="3764413594-2">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3764413594-3">&lt;&lt;</span><span class="p" data-group-id="3764413594-3">&gt;&gt;</span><span class="p" data-group-id="3764413594-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Appending to a binary in an efficient way can be done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">triples_to_bin</span><span class="p" data-group-id="0056324239-1">(</span><span class="n">T</span><span class="p" data-group-id="0056324239-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">triples_to_bin</span><span class="p" data-group-id="0056324239-2">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0056324239-3">&lt;&lt;</span><span class="p" data-group-id="0056324239-3">&gt;&gt;</span><span class="p" data-group-id="0056324239-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">triples_to_bin</span><span class="p" data-group-id="3764413594-4">(</span><span class="p" data-group-id="3764413594-5">[</span><span class="p" data-group-id="3764413594-6">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="n">Z</span><span class="p" data-group-id="3764413594-6">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="3764413594-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3764413594-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">triples_to_bin</span><span class="p" data-group-id="3764413594-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3764413594-8">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">X</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="n">Y</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="n">Z</span><span class="p">:</span><span class="mi">32</span><span class="p" data-group-id="3764413594-8">&gt;&gt;</span><span class="p" data-group-id="3764413594-7">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">triples_to_bin</span><span class="p" data-group-id="3764413594-9">(</span><span class="p" data-group-id="3764413594-10">[</span><span class="p" data-group-id="3764413594-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3764413594-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">triples_to_bin</span><span class="p" data-group-id="0056324239-4">(</span><span class="p" data-group-id="0056324239-5">[</span><span class="p" data-group-id="0056324239-6">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="n">Z</span><span class="p" data-group-id="0056324239-6">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="0056324239-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="0056324239-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">triples_to_bin</span><span class="p" data-group-id="0056324239-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0056324239-8">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">X</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="n">Y</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="n">Z</span><span class="p">:</span><span class="mi">32</span><span class="p" data-group-id="0056324239-8">&gt;&gt;</span><span class="p" data-group-id="0056324239-7">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">triples_to_bin</span><span class="p" data-group-id="0056324239-9">(</span><span class="p" data-group-id="0056324239-10">[</span><span class="p" data-group-id="0056324239-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="0056324239-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="list_comprehensions.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/c_port.html
│ │ │ @@ -148,101 +148,101 @@
│ │ │  external program, if it is written properly).</p><p>The port is created using the BIF <a href="../../erts-17.0/doc/html/erlang.html#open_port/2"><code class="inline">open_port/2</code></a> with
│ │ │  <code class="inline">{spawn,ExtPrg}</code> as the first argument. The string <code class="inline">ExtPrg</code> is the name of the
│ │ │  external program, including any command line arguments. The second argument is a
│ │ │  list of options, in this case only <code class="inline">{packet,2}</code>. This option says that a 2 byte
│ │ │  length indicator is to be used to simplify the communication between C and
│ │ │  Erlang. The Erlang port automatically adds the length indicator, but this must
│ │ │  be done explicitly in the external C program.</p><p>The process is also set to trap exits, which enables detection of failure of the
│ │ │ -external program:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6085707992-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="6085707992-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6085707992-2">(</span><span class="p" data-group-id="6085707992-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6085707992-3">]</span><span class="p" data-group-id="6085707992-2">)</span><span class="p">.</span><span class="w">
│ │ │ +external program:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2881660939-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="2881660939-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2881660939-2">(</span><span class="p" data-group-id="2881660939-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2881660939-3">]</span><span class="p" data-group-id="2881660939-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="6085707992-4">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="6085707992-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="nf">spawn</span><span class="p" data-group-id="6085707992-5">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6085707992-6">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="6085707992-6">]</span><span class="p" data-group-id="6085707992-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="2881660939-4">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="2881660939-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="nf">spawn</span><span class="p" data-group-id="2881660939-5">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2881660939-6">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="2881660939-6">]</span><span class="p" data-group-id="2881660939-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="6085707992-7">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="6085707992-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="nf">register</span><span class="p" data-group-id="6085707992-8">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6085707992-9">(</span><span class="p" data-group-id="6085707992-9">)</span><span class="p" data-group-id="6085707992-8">)</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="nf">process_flag</span><span class="p" data-group-id="6085707992-10">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="6085707992-10">)</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="6085707992-11">(</span><span class="p" data-group-id="6085707992-12">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="6085707992-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6085707992-13">[</span><span class="p" data-group-id="6085707992-14">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="6085707992-14">}</span><span class="p" data-group-id="6085707992-13">]</span><span class="p" data-group-id="6085707992-11">)</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="nf">loop</span><span class="p" data-group-id="6085707992-15">(</span><span class="n">Port</span><span class="p" data-group-id="6085707992-15">)</span><span class="p">.</span></code></pre><p>Now <code class="inline">complex1:foo/1</code> and <code class="inline">complex1:bar/1</code> can be implemented. Both send a
│ │ │ -message to the <code class="inline">complex</code> process and receive the following replies:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="0141838747-1">(</span><span class="n">X</span><span class="p" data-group-id="0141838747-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="nf">call_port</span><span class="p" data-group-id="0141838747-2">(</span><span class="p" data-group-id="0141838747-3">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0141838747-3">}</span><span class="p" data-group-id="0141838747-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="0141838747-4">(</span><span class="n">Y</span><span class="p" data-group-id="0141838747-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="nf">call_port</span><span class="p" data-group-id="0141838747-5">(</span><span class="p" data-group-id="0141838747-6">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0141838747-6">}</span><span class="p" data-group-id="0141838747-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="2881660939-7">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="2881660939-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="nf">register</span><span class="p" data-group-id="2881660939-8">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2881660939-9">(</span><span class="p" data-group-id="2881660939-9">)</span><span class="p" data-group-id="2881660939-8">)</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="nf">process_flag</span><span class="p" data-group-id="2881660939-10">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="2881660939-10">)</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="2881660939-11">(</span><span class="p" data-group-id="2881660939-12">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="2881660939-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2881660939-13">[</span><span class="p" data-group-id="2881660939-14">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="2881660939-14">}</span><span class="p" data-group-id="2881660939-13">]</span><span class="p" data-group-id="2881660939-11">)</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="nf">loop</span><span class="p" data-group-id="2881660939-15">(</span><span class="n">Port</span><span class="p" data-group-id="2881660939-15">)</span><span class="p">.</span></code></pre><p>Now <code class="inline">complex1:foo/1</code> and <code class="inline">complex1:bar/1</code> can be implemented. Both send a
│ │ │ +message to the <code class="inline">complex</code> process and receive the following replies:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="1323331921-1">(</span><span class="n">X</span><span class="p" data-group-id="1323331921-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="nf">call_port</span><span class="p" data-group-id="1323331921-2">(</span><span class="p" data-group-id="1323331921-3">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1323331921-3">}</span><span class="p" data-group-id="1323331921-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="1323331921-4">(</span><span class="n">Y</span><span class="p" data-group-id="1323331921-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="nf">call_port</span><span class="p" data-group-id="1323331921-5">(</span><span class="p" data-group-id="1323331921-6">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1323331921-6">}</span><span class="p" data-group-id="1323331921-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="0141838747-7">(</span><span class="n">Msg</span><span class="p" data-group-id="0141838747-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0141838747-8">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0141838747-9">(</span><span class="p" data-group-id="0141838747-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0141838747-8">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="1323331921-7">(</span><span class="n">Msg</span><span class="p" data-group-id="1323331921-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1323331921-8">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1323331921-9">(</span><span class="p" data-group-id="1323331921-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="1323331921-8">}</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0141838747-10">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0141838747-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1323331921-10">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1323331921-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │        </span><span class="n">Result</span><span class="w">
│ │ │ -  </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">complex</code> process does the following:</p><ul><li>Encodes the message into a sequence of bytes.</li><li>Sends it to the port.</li><li>Waits for a reply.</li><li>Decodes the reply.</li><li>Sends it back to the caller:</li></ul><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="4533990246-1">(</span><span class="n">Port</span><span class="p" data-group-id="4533990246-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">complex</code> process does the following:</p><ul><li>Encodes the message into a sequence of bytes.</li><li>Sends it to the port.</li><li>Waits for a reply.</li><li>Decodes the reply.</li><li>Sends it back to the caller:</li></ul><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="0420300121-1">(</span><span class="n">Port</span><span class="p" data-group-id="0420300121-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │    </span><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4533990246-2">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4533990246-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -      </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4533990246-3">{</span><span class="nf">self</span><span class="p" data-group-id="4533990246-4">(</span><span class="p" data-group-id="4533990246-4">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4533990246-5">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="4533990246-6">(</span><span class="n">Msg</span><span class="p" data-group-id="4533990246-6">)</span><span class="p" data-group-id="4533990246-5">}</span><span class="p" data-group-id="4533990246-3">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0420300121-2">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0420300121-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +      </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0420300121-3">{</span><span class="nf">self</span><span class="p" data-group-id="0420300121-4">(</span><span class="p" data-group-id="0420300121-4">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0420300121-5">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="0420300121-6">(</span><span class="n">Msg</span><span class="p" data-group-id="0420300121-6">)</span><span class="p" data-group-id="0420300121-5">}</span><span class="p" data-group-id="0420300121-3">}</span><span class="p">,</span><span class="w">
│ │ │        </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="4533990246-7">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4533990246-8">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4533990246-8">}</span><span class="p" data-group-id="4533990246-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -          </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4533990246-9">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="4533990246-10">(</span><span class="n">Data</span><span class="p" data-group-id="4533990246-10">)</span><span class="p" data-group-id="4533990246-9">}</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0420300121-7">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0420300121-8">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0420300121-8">}</span><span class="p" data-group-id="0420300121-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +          </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0420300121-9">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="0420300121-10">(</span><span class="n">Data</span><span class="p" data-group-id="0420300121-10">)</span><span class="p" data-group-id="0420300121-9">}</span><span class="w">
│ │ │        </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -      </span><span class="nf">loop</span><span class="p" data-group-id="4533990246-11">(</span><span class="n">Port</span><span class="p" data-group-id="4533990246-11">)</span><span class="w">
│ │ │ +      </span><span class="nf">loop</span><span class="p" data-group-id="0420300121-11">(</span><span class="n">Port</span><span class="p" data-group-id="0420300121-11">)</span><span class="w">
│ │ │    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Assuming that both the arguments and the results from the C functions are less
│ │ │  than 256, a simple encoding/decoding scheme is employed. In this scheme, <code class="inline">foo</code>
│ │ │  is represented by byte 1, <code class="inline">bar</code> is represented by 2, and the argument/result is
│ │ │ -represented by a single byte as well:</p><pre><code class="makeup erlang" translate="no"><span class="nf">encode</span><span class="p" data-group-id="7241450971-1">(</span><span class="p" data-group-id="7241450971-2">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="7241450971-2">}</span><span class="p" data-group-id="7241450971-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7241450971-3">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="7241450971-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="7241450971-4">(</span><span class="p" data-group-id="7241450971-5">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7241450971-5">}</span><span class="p" data-group-id="7241450971-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7241450971-6">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7241450971-6">]</span><span class="p">.</span><span class="w">
│ │ │ +represented by a single byte as well:</p><pre><code class="makeup erlang" translate="no"><span class="nf">encode</span><span class="p" data-group-id="6081169342-1">(</span><span class="p" data-group-id="6081169342-2">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="6081169342-2">}</span><span class="p" data-group-id="6081169342-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6081169342-3">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="6081169342-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="6081169342-4">(</span><span class="p" data-group-id="6081169342-5">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6081169342-5">}</span><span class="p" data-group-id="6081169342-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6081169342-6">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6081169342-6">]</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="7241450971-7">(</span><span class="p" data-group-id="7241450971-8">[</span><span class="n">Int</span><span class="p" data-group-id="7241450971-8">]</span><span class="p" data-group-id="7241450971-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>The resulting Erlang program, including functionality for stopping the port and
│ │ │ -detecting port failures, is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5948969679-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="5948969679-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5948969679-2">(</span><span class="p" data-group-id="5948969679-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5948969679-3">]</span><span class="p" data-group-id="5948969679-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5948969679-4">(</span><span class="p" data-group-id="5948969679-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5948969679-5">]</span><span class="p" data-group-id="5948969679-4">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="5948969679-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="5948969679-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="5948969679-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5948969679-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="5948969679-8">]</span><span class="p" data-group-id="5948969679-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="5948969679-9">(</span><span class="p" data-group-id="5948969679-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="6081169342-7">(</span><span class="p" data-group-id="6081169342-8">[</span><span class="n">Int</span><span class="p" data-group-id="6081169342-8">]</span><span class="p" data-group-id="6081169342-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>The resulting Erlang program, including functionality for stopping the port and
│ │ │ +detecting port failures, is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2966676223-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="2966676223-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2966676223-2">(</span><span class="p" data-group-id="2966676223-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2966676223-3">]</span><span class="p" data-group-id="2966676223-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2966676223-4">(</span><span class="p" data-group-id="2966676223-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2966676223-5">]</span><span class="p" data-group-id="2966676223-4">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="2966676223-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="2966676223-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="2966676223-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2966676223-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="2966676223-8">]</span><span class="p" data-group-id="2966676223-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="2966676223-9">(</span><span class="p" data-group-id="2966676223-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">stop</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="5948969679-10">(</span><span class="n">X</span><span class="p" data-group-id="5948969679-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="5948969679-11">(</span><span class="p" data-group-id="5948969679-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="5948969679-12">}</span><span class="p" data-group-id="5948969679-11">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="5948969679-13">(</span><span class="n">Y</span><span class="p" data-group-id="5948969679-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="5948969679-14">(</span><span class="p" data-group-id="5948969679-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5948969679-15">}</span><span class="p" data-group-id="5948969679-14">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="2966676223-10">(</span><span class="n">X</span><span class="p" data-group-id="2966676223-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="2966676223-11">(</span><span class="p" data-group-id="2966676223-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="2966676223-12">}</span><span class="p" data-group-id="2966676223-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="2966676223-13">(</span><span class="n">Y</span><span class="p" data-group-id="2966676223-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="2966676223-14">(</span><span class="p" data-group-id="2966676223-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2966676223-15">}</span><span class="p" data-group-id="2966676223-14">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="5948969679-16">(</span><span class="n">Msg</span><span class="p" data-group-id="5948969679-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5948969679-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5948969679-18">(</span><span class="p" data-group-id="5948969679-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="5948969679-17">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="2966676223-16">(</span><span class="n">Msg</span><span class="p" data-group-id="2966676223-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2966676223-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2966676223-18">(</span><span class="p" data-group-id="2966676223-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="2966676223-17">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="5948969679-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5948969679-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="2966676223-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="2966676223-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  	    </span><span class="n">Result</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="5948969679-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="5948969679-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="5948969679-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5948969679-22">(</span><span class="p" data-group-id="5948969679-22">)</span><span class="p" data-group-id="5948969679-21">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="5948969679-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="5948969679-23">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="5948969679-24">(</span><span class="p" data-group-id="5948969679-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="5948969679-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5948969679-26">[</span><span class="p" data-group-id="5948969679-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="5948969679-27">}</span><span class="p" data-group-id="5948969679-26">]</span><span class="p" data-group-id="5948969679-24">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="5948969679-28">(</span><span class="n">Port</span><span class="p" data-group-id="5948969679-28">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="2966676223-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="2966676223-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="2966676223-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2966676223-22">(</span><span class="p" data-group-id="2966676223-22">)</span><span class="p" data-group-id="2966676223-21">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="2966676223-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="2966676223-23">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="2966676223-24">(</span><span class="p" data-group-id="2966676223-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="2966676223-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2966676223-26">[</span><span class="p" data-group-id="2966676223-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="2966676223-27">}</span><span class="p" data-group-id="2966676223-26">]</span><span class="p" data-group-id="2966676223-24">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="2966676223-28">(</span><span class="n">Port</span><span class="p" data-group-id="2966676223-28">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="5948969679-29">(</span><span class="n">Port</span><span class="p" data-group-id="5948969679-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="2966676223-29">(</span><span class="n">Port</span><span class="p" data-group-id="2966676223-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="5948969679-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="5948969679-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5948969679-31">{</span><span class="nf">self</span><span class="p" data-group-id="5948969679-32">(</span><span class="p" data-group-id="5948969679-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5948969679-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="5948969679-34">(</span><span class="n">Msg</span><span class="p" data-group-id="5948969679-34">)</span><span class="p" data-group-id="5948969679-33">}</span><span class="p" data-group-id="5948969679-31">}</span><span class="p">,</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="2966676223-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="2966676223-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2966676223-31">{</span><span class="nf">self</span><span class="p" data-group-id="2966676223-32">(</span><span class="p" data-group-id="2966676223-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2966676223-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="2966676223-34">(</span><span class="n">Msg</span><span class="p" data-group-id="2966676223-34">)</span><span class="p" data-group-id="2966676223-33">}</span><span class="p" data-group-id="2966676223-31">}</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="5948969679-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5948969679-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5948969679-36">}</span><span class="p" data-group-id="5948969679-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5948969679-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="5948969679-38">(</span><span class="n">Data</span><span class="p" data-group-id="5948969679-38">)</span><span class="p" data-group-id="5948969679-37">}</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="2966676223-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2966676223-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2966676223-36">}</span><span class="p" data-group-id="2966676223-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2966676223-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="2966676223-38">(</span><span class="n">Data</span><span class="p" data-group-id="2966676223-38">)</span><span class="p" data-group-id="2966676223-37">}</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -	    </span><span class="nf">loop</span><span class="p" data-group-id="5948969679-39">(</span><span class="n">Port</span><span class="p" data-group-id="5948969679-39">)</span><span class="p">;</span><span class="w">
│ │ │ +	    </span><span class="nf">loop</span><span class="p" data-group-id="2966676223-39">(</span><span class="n">Port</span><span class="p" data-group-id="2966676223-39">)</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">stop</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5948969679-40">{</span><span class="nf">self</span><span class="p" data-group-id="5948969679-41">(</span><span class="p" data-group-id="5948969679-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="5948969679-40">}</span><span class="p">,</span><span class="w">
│ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2966676223-40">{</span><span class="nf">self</span><span class="p" data-group-id="2966676223-41">(</span><span class="p" data-group-id="2966676223-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="2966676223-40">}</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="5948969679-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="5948969679-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="nf">exit</span><span class="p" data-group-id="5948969679-43">(</span><span class="ss">normal</span><span class="p" data-group-id="5948969679-43">)</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="2966676223-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="2966676223-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="nf">exit</span><span class="p" data-group-id="2966676223-43">(</span><span class="ss">normal</span><span class="p" data-group-id="2966676223-43">)</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="5948969679-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="5948969679-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="nf">exit</span><span class="p" data-group-id="5948969679-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="5948969679-45">)</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="2966676223-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="2966676223-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	    </span><span class="nf">exit</span><span class="p" data-group-id="2966676223-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="2966676223-45">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="5948969679-46">(</span><span class="p" data-group-id="5948969679-47">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="5948969679-47">}</span><span class="p" data-group-id="5948969679-46">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5948969679-48">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="5948969679-48">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="5948969679-49">(</span><span class="p" data-group-id="5948969679-50">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5948969679-50">}</span><span class="p" data-group-id="5948969679-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5948969679-51">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5948969679-51">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="2966676223-46">(</span><span class="p" data-group-id="2966676223-47">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="2966676223-47">}</span><span class="p" data-group-id="2966676223-46">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2966676223-48">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="2966676223-48">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="2966676223-49">(</span><span class="p" data-group-id="2966676223-50">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2966676223-50">}</span><span class="p" data-group-id="2966676223-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2966676223-51">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2966676223-51">]</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="5948969679-52">(</span><span class="p" data-group-id="5948969679-53">[</span><span class="n">Int</span><span class="p" data-group-id="5948969679-53">]</span><span class="p" data-group-id="5948969679-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><h2 id="c-program" class="section-heading">
│ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="2966676223-52">(</span><span class="p" data-group-id="2966676223-53">[</span><span class="n">Int</span><span class="p" data-group-id="2966676223-53">]</span><span class="p" data-group-id="2966676223-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><h2 id="c-program" class="section-heading">
│ │ │    <a href="#c-program" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">C Program</span>
│ │ │  </h2>
│ │ │  <p>On the C side, it is necessary to write functions for receiving and sending data
│ │ │  with 2 byte length indicators from/to Erlang. By default, the C program is to
│ │ │ @@ -333,25 +333,25 @@
│ │ │  and terminates.</p><h2 id="running-the-example" class="section-heading">
│ │ │    <a href="#running-the-example" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Running the Example</span>
│ │ │  </h2>
│ │ │  <p><em>Step 1.</em> Compile the C code:</p><pre><code class="text">$ gcc -o extprg complex.c erl_comm.c port.c</code></pre><p><em>Step 2.</em> Start Erlang and compile the Erlang code:</p><pre><code class="makeup erlang" translate="no"><span class="sc">$ </span><span class="ss">erl</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="4671471750-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="4671471750-1">]</span><span class="w"> </span><span class="p" data-group-id="4671471750-2">[</span><span class="ss">source</span><span class="p" data-group-id="4671471750-2">]</span><span class="w"> </span><span class="p" data-group-id="4671471750-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="4671471750-3">]</span><span class="w"> </span><span class="p" data-group-id="4671471750-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="4671471750-4">]</span><span class="w"> </span><span class="p" data-group-id="4671471750-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="4671471750-5">]</span><span class="w"> </span><span class="p" data-group-id="4671471750-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4671471750-6">]</span><span class="w"> </span><span class="p" data-group-id="4671471750-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="4671471750-7">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="6731227243-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="6731227243-1">]</span><span class="w"> </span><span class="p" data-group-id="6731227243-2">[</span><span class="ss">source</span><span class="p" data-group-id="6731227243-2">]</span><span class="w"> </span><span class="p" data-group-id="6731227243-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="6731227243-3">]</span><span class="w"> </span><span class="p" data-group-id="6731227243-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="6731227243-4">]</span><span class="w"> </span><span class="p" data-group-id="6731227243-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="6731227243-5">]</span><span class="w"> </span><span class="p" data-group-id="6731227243-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="6731227243-6">]</span><span class="w"> </span><span class="p" data-group-id="6731227243-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="6731227243-7">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="4671471750-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="4671471750-9">(</span><span class="p" data-group-id="4671471750-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="4671471750-8">)</span><span class="w">
│ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="4671471750-10">(</span><span class="ss">complex1</span><span class="p" data-group-id="4671471750-10">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4671471750-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex1</span><span class="p" data-group-id="4671471750-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="4534035356-1">(</span><span class="s">&quot;./extprg&quot;</span><span class="p" data-group-id="4534035356-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="6731227243-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="6731227243-9">(</span><span class="p" data-group-id="6731227243-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="6731227243-8">)</span><span class="w">
│ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="6731227243-10">(</span><span class="ss">complex1</span><span class="p" data-group-id="6731227243-10">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6731227243-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex1</span><span class="p" data-group-id="6731227243-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="3980564811-1">(</span><span class="s">&quot;./extprg&quot;</span><span class="p" data-group-id="3980564811-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.34</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="4534035356-2">(</span><span class="mi">3</span><span class="p" data-group-id="4534035356-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="3980564811-2">(</span><span class="mi">3</span><span class="p" data-group-id="3980564811-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="4534035356-3">(</span><span class="mi">5</span><span class="p" data-group-id="4534035356-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="3980564811-3">(</span><span class="mi">5</span><span class="p" data-group-id="3980564811-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">10</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="4534035356-4">(</span><span class="p" data-group-id="4534035356-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="3980564811-4">(</span><span class="p" data-group-id="3980564811-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">stop</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="example.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/c_portdriver.html
│ │ │ @@ -151,112 +151,112 @@
│ │ │  <p>Like a port program, the port communicates with an Erlang process. All
│ │ │  communication goes through one Erlang process that is the <em>connected process</em> of
│ │ │  the port driver. Terminating this process closes the port driver.</p><p>Before the port is created, the driver must be loaded. This is done with the
│ │ │  function <a href="../../lib/kernel-11.0/doc/html/erl_ddll.html#load_driver/2"><code class="inline">erl_ddll:load_driver/2</code></a>, with the name of the shared library as
│ │ │  argument.</p><p>The port is then created using the BIF <a href="../../erts-17.0/doc/html/erlang.html#open_port/2"><code class="inline">open_port/2</code></a>, with the
│ │ │  tuple <code class="inline">{spawn, DriverName}</code> as the first argument. The string <code class="inline">SharedLib</code> is the
│ │ │  name of the port driver. The second argument is a list of options, none in this
│ │ │ -case:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7163105163-1">(</span><span class="ss">complex5</span><span class="p" data-group-id="7163105163-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7163105163-2">(</span><span class="p" data-group-id="7163105163-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7163105163-3">]</span><span class="p" data-group-id="7163105163-2">)</span><span class="p">.</span><span class="w">
│ │ │ +case:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1203432107-1">(</span><span class="ss">complex5</span><span class="p" data-group-id="1203432107-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1203432107-2">(</span><span class="p" data-group-id="1203432107-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1203432107-3">]</span><span class="p" data-group-id="1203432107-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="7163105163-4">(</span><span class="n">SharedLib</span><span class="p" data-group-id="7163105163-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="7163105163-5">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="7163105163-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="1203432107-4">(</span><span class="n">SharedLib</span><span class="p" data-group-id="1203432107-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="1203432107-5">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="1203432107-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="7163105163-6">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="7163105163-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="7163105163-7">(</span><span class="p" data-group-id="7163105163-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="7163105163-8">}</span><span class="p" data-group-id="7163105163-7">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="1203432107-6">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="1203432107-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="1203432107-7">(</span><span class="p" data-group-id="1203432107-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="1203432107-8">}</span><span class="p" data-group-id="1203432107-7">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="7163105163-9">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7163105163-10">[</span><span class="n">SharedLib</span><span class="p" data-group-id="7163105163-10">]</span><span class="p" data-group-id="7163105163-9">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="1203432107-9">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1203432107-10">[</span><span class="n">SharedLib</span><span class="p" data-group-id="1203432107-10">]</span><span class="p" data-group-id="1203432107-9">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="7163105163-11">(</span><span class="n">SharedLib</span><span class="p" data-group-id="7163105163-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="nf">register</span><span class="p" data-group-id="7163105163-12">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7163105163-13">(</span><span class="p" data-group-id="7163105163-13">)</span><span class="p" data-group-id="7163105163-12">)</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="7163105163-14">(</span><span class="p" data-group-id="7163105163-15">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="7163105163-15">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7163105163-16">[</span><span class="p" data-group-id="7163105163-16">]</span><span class="p" data-group-id="7163105163-14">)</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="nf">loop</span><span class="p" data-group-id="7163105163-17">(</span><span class="n">Port</span><span class="p" data-group-id="7163105163-17">)</span><span class="p">.</span></code></pre><p>Now <code class="inline">complex5:foo/1</code> and <code class="inline">complex5:bar/1</code> can be implemented. Both send a
│ │ │ -message to the <code class="inline">complex</code> process and receive the following reply:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="0112609463-1">(</span><span class="n">X</span><span class="p" data-group-id="0112609463-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="0112609463-2">(</span><span class="p" data-group-id="0112609463-3">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0112609463-3">}</span><span class="p" data-group-id="0112609463-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="0112609463-4">(</span><span class="n">Y</span><span class="p" data-group-id="0112609463-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="0112609463-5">(</span><span class="p" data-group-id="0112609463-6">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0112609463-6">}</span><span class="p" data-group-id="0112609463-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="1203432107-11">(</span><span class="n">SharedLib</span><span class="p" data-group-id="1203432107-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="nf">register</span><span class="p" data-group-id="1203432107-12">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1203432107-13">(</span><span class="p" data-group-id="1203432107-13">)</span><span class="p" data-group-id="1203432107-12">)</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="1203432107-14">(</span><span class="p" data-group-id="1203432107-15">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="1203432107-15">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1203432107-16">[</span><span class="p" data-group-id="1203432107-16">]</span><span class="p" data-group-id="1203432107-14">)</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="nf">loop</span><span class="p" data-group-id="1203432107-17">(</span><span class="n">Port</span><span class="p" data-group-id="1203432107-17">)</span><span class="p">.</span></code></pre><p>Now <code class="inline">complex5:foo/1</code> and <code class="inline">complex5:bar/1</code> can be implemented. Both send a
│ │ │ +message to the <code class="inline">complex</code> process and receive the following reply:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="6523646448-1">(</span><span class="n">X</span><span class="p" data-group-id="6523646448-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="6523646448-2">(</span><span class="p" data-group-id="6523646448-3">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="6523646448-3">}</span><span class="p" data-group-id="6523646448-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="6523646448-4">(</span><span class="n">Y</span><span class="p" data-group-id="6523646448-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="6523646448-5">(</span><span class="p" data-group-id="6523646448-6">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6523646448-6">}</span><span class="p" data-group-id="6523646448-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="0112609463-7">(</span><span class="n">Msg</span><span class="p" data-group-id="0112609463-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0112609463-8">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0112609463-9">(</span><span class="p" data-group-id="0112609463-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0112609463-8">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="6523646448-7">(</span><span class="n">Msg</span><span class="p" data-group-id="6523646448-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6523646448-8">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6523646448-9">(</span><span class="p" data-group-id="6523646448-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="6523646448-8">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0112609463-10">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0112609463-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="6523646448-10">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="6523646448-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="n">Result</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">complex</code> process performs the following:</p><ul><li>Encodes the message into a sequence of bytes.</li><li>Sends it to the port.</li><li>Waits for a reply.</li><li>Decodes the reply.</li><li>Sends it back to the caller:</li></ul><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="0111698555-1">(</span><span class="n">Port</span><span class="p" data-group-id="0111698555-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">complex</code> process performs the following:</p><ul><li>Encodes the message into a sequence of bytes.</li><li>Sends it to the port.</li><li>Waits for a reply.</li><li>Decodes the reply.</li><li>Sends it back to the caller:</li></ul><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="1170280603-1">(</span><span class="n">Port</span><span class="p" data-group-id="1170280603-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0111698555-2">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0111698555-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0111698555-3">{</span><span class="nf">self</span><span class="p" data-group-id="0111698555-4">(</span><span class="p" data-group-id="0111698555-4">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0111698555-5">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="0111698555-6">(</span><span class="n">Msg</span><span class="p" data-group-id="0111698555-6">)</span><span class="p" data-group-id="0111698555-5">}</span><span class="p" data-group-id="0111698555-3">}</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="1170280603-2">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="1170280603-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1170280603-3">{</span><span class="nf">self</span><span class="p" data-group-id="1170280603-4">(</span><span class="p" data-group-id="1170280603-4">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1170280603-5">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="1170280603-6">(</span><span class="n">Msg</span><span class="p" data-group-id="1170280603-6">)</span><span class="p" data-group-id="1170280603-5">}</span><span class="p" data-group-id="1170280603-3">}</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="k">receive</span><span class="w">
│ │ │ -                </span><span class="p" data-group-id="0111698555-7">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0111698555-8">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0111698555-8">}</span><span class="p" data-group-id="0111698555-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0111698555-9">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="0111698555-10">(</span><span class="n">Data</span><span class="p" data-group-id="0111698555-10">)</span><span class="p" data-group-id="0111698555-9">}</span><span class="w">
│ │ │ +                </span><span class="p" data-group-id="1170280603-7">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1170280603-8">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1170280603-8">}</span><span class="p" data-group-id="1170280603-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1170280603-9">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="1170280603-10">(</span><span class="n">Data</span><span class="p" data-group-id="1170280603-10">)</span><span class="p" data-group-id="1170280603-9">}</span><span class="w">
│ │ │              </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="0111698555-11">(</span><span class="n">Port</span><span class="p" data-group-id="0111698555-11">)</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="1170280603-11">(</span><span class="n">Port</span><span class="p" data-group-id="1170280603-11">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Assuming that both the arguments and the results from the C functions are less
│ │ │  than 256, a simple encoding/decoding scheme is employed. In this scheme, <code class="inline">foo</code>
│ │ │  is represented by byte 1, <code class="inline">bar</code> is represented by 2, and the argument/result is
│ │ │ -represented by a single byte as well:</p><pre><code class="makeup erlang" translate="no"><span class="nf">encode</span><span class="p" data-group-id="3481367309-1">(</span><span class="p" data-group-id="3481367309-2">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="3481367309-2">}</span><span class="p" data-group-id="3481367309-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3481367309-3">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="3481367309-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="3481367309-4">(</span><span class="p" data-group-id="3481367309-5">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3481367309-5">}</span><span class="p" data-group-id="3481367309-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3481367309-6">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3481367309-6">]</span><span class="p">.</span><span class="w">
│ │ │ +represented by a single byte as well:</p><pre><code class="makeup erlang" translate="no"><span class="nf">encode</span><span class="p" data-group-id="4811975616-1">(</span><span class="p" data-group-id="4811975616-2">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4811975616-2">}</span><span class="p" data-group-id="4811975616-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4811975616-3">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4811975616-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="4811975616-4">(</span><span class="p" data-group-id="4811975616-5">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4811975616-5">}</span><span class="p" data-group-id="4811975616-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4811975616-6">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4811975616-6">]</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="3481367309-7">(</span><span class="p" data-group-id="3481367309-8">[</span><span class="n">Int</span><span class="p" data-group-id="3481367309-8">]</span><span class="p" data-group-id="3481367309-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>The resulting Erlang program, including functions for stopping the port and
│ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="4811975616-7">(</span><span class="p" data-group-id="4811975616-8">[</span><span class="n">Int</span><span class="p" data-group-id="4811975616-8">]</span><span class="p" data-group-id="4811975616-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>The resulting Erlang program, including functions for stopping the port and
│ │ │  detecting port failures, is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3478326516-1">(</span><span class="ss">complex5</span><span class="p" data-group-id="3478326516-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3478326516-2">(</span><span class="p" data-group-id="3478326516-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3478326516-3">]</span><span class="p" data-group-id="3478326516-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3478326516-4">(</span><span class="p" data-group-id="3478326516-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3478326516-5">]</span><span class="p" data-group-id="3478326516-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7664791780-1">(</span><span class="ss">complex5</span><span class="p" data-group-id="7664791780-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7664791780-2">(</span><span class="p" data-group-id="7664791780-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7664791780-3">]</span><span class="p" data-group-id="7664791780-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7664791780-4">(</span><span class="p" data-group-id="7664791780-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7664791780-5">]</span><span class="p" data-group-id="7664791780-4">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="3478326516-6">(</span><span class="n">SharedLib</span><span class="p" data-group-id="3478326516-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="3478326516-7">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="3478326516-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="7664791780-6">(</span><span class="n">SharedLib</span><span class="p" data-group-id="7664791780-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="7664791780-7">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="7664791780-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │  	</span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="3478326516-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="3478326516-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -	</span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="3478326516-9">(</span><span class="p" data-group-id="3478326516-10">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="3478326516-10">}</span><span class="p" data-group-id="3478326516-9">)</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="7664791780-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="7664791780-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ +	</span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="7664791780-9">(</span><span class="p" data-group-id="7664791780-10">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="7664791780-10">}</span><span class="p" data-group-id="7664791780-9">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="3478326516-11">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3478326516-12">[</span><span class="n">SharedLib</span><span class="p" data-group-id="3478326516-12">]</span><span class="p" data-group-id="3478326516-11">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="7664791780-11">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7664791780-12">[</span><span class="n">SharedLib</span><span class="p" data-group-id="7664791780-12">]</span><span class="p" data-group-id="7664791780-11">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="3478326516-13">(</span><span class="n">SharedLib</span><span class="p" data-group-id="3478326516-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="3478326516-14">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3478326516-15">(</span><span class="p" data-group-id="3478326516-15">)</span><span class="p" data-group-id="3478326516-14">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="3478326516-16">(</span><span class="p" data-group-id="3478326516-17">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="3478326516-17">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3478326516-18">[</span><span class="p" data-group-id="3478326516-18">]</span><span class="p" data-group-id="3478326516-16">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="3478326516-19">(</span><span class="n">Port</span><span class="p" data-group-id="3478326516-19">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="7664791780-13">(</span><span class="n">SharedLib</span><span class="p" data-group-id="7664791780-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="7664791780-14">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7664791780-15">(</span><span class="p" data-group-id="7664791780-15">)</span><span class="p" data-group-id="7664791780-14">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="7664791780-16">(</span><span class="p" data-group-id="7664791780-17">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="7664791780-17">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7664791780-18">[</span><span class="p" data-group-id="7664791780-18">]</span><span class="p" data-group-id="7664791780-16">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="7664791780-19">(</span><span class="n">Port</span><span class="p" data-group-id="7664791780-19">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="3478326516-20">(</span><span class="p" data-group-id="3478326516-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="7664791780-20">(</span><span class="p" data-group-id="7664791780-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">stop</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="3478326516-21">(</span><span class="n">X</span><span class="p" data-group-id="3478326516-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="3478326516-22">(</span><span class="p" data-group-id="3478326516-23">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="3478326516-23">}</span><span class="p" data-group-id="3478326516-22">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="3478326516-24">(</span><span class="n">Y</span><span class="p" data-group-id="3478326516-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="3478326516-25">(</span><span class="p" data-group-id="3478326516-26">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3478326516-26">}</span><span class="p" data-group-id="3478326516-25">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="7664791780-21">(</span><span class="n">X</span><span class="p" data-group-id="7664791780-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="7664791780-22">(</span><span class="p" data-group-id="7664791780-23">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="7664791780-23">}</span><span class="p" data-group-id="7664791780-22">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="7664791780-24">(</span><span class="n">Y</span><span class="p" data-group-id="7664791780-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="7664791780-25">(</span><span class="p" data-group-id="7664791780-26">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7664791780-26">}</span><span class="p" data-group-id="7664791780-25">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="3478326516-27">(</span><span class="n">Msg</span><span class="p" data-group-id="3478326516-27">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3478326516-28">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3478326516-29">(</span><span class="p" data-group-id="3478326516-29">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="3478326516-28">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="7664791780-27">(</span><span class="n">Msg</span><span class="p" data-group-id="7664791780-27">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7664791780-28">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7664791780-29">(</span><span class="p" data-group-id="7664791780-29">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="7664791780-28">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="3478326516-30">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="3478326516-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="7664791780-30">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7664791780-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  	    </span><span class="n">Result</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="3478326516-31">(</span><span class="n">Port</span><span class="p" data-group-id="3478326516-31">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="7664791780-31">(</span><span class="n">Port</span><span class="p" data-group-id="7664791780-31">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="3478326516-32">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="3478326516-32">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3478326516-33">{</span><span class="nf">self</span><span class="p" data-group-id="3478326516-34">(</span><span class="p" data-group-id="3478326516-34">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3478326516-35">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="3478326516-36">(</span><span class="n">Msg</span><span class="p" data-group-id="3478326516-36">)</span><span class="p" data-group-id="3478326516-35">}</span><span class="p" data-group-id="3478326516-33">}</span><span class="p">,</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="7664791780-32">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="7664791780-32">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7664791780-33">{</span><span class="nf">self</span><span class="p" data-group-id="7664791780-34">(</span><span class="p" data-group-id="7664791780-34">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7664791780-35">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="7664791780-36">(</span><span class="n">Msg</span><span class="p" data-group-id="7664791780-36">)</span><span class="p" data-group-id="7664791780-35">}</span><span class="p" data-group-id="7664791780-33">}</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="3478326516-37">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3478326516-38">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3478326516-38">}</span><span class="p" data-group-id="3478326516-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3478326516-39">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="3478326516-40">(</span><span class="n">Data</span><span class="p" data-group-id="3478326516-40">)</span><span class="p" data-group-id="3478326516-39">}</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="7664791780-37">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7664791780-38">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7664791780-38">}</span><span class="p" data-group-id="7664791780-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7664791780-39">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="7664791780-40">(</span><span class="n">Data</span><span class="p" data-group-id="7664791780-40">)</span><span class="p" data-group-id="7664791780-39">}</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -	    </span><span class="nf">loop</span><span class="p" data-group-id="3478326516-41">(</span><span class="n">Port</span><span class="p" data-group-id="3478326516-41">)</span><span class="p">;</span><span class="w">
│ │ │ +	    </span><span class="nf">loop</span><span class="p" data-group-id="7664791780-41">(</span><span class="n">Port</span><span class="p" data-group-id="7664791780-41">)</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">stop</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3478326516-42">{</span><span class="nf">self</span><span class="p" data-group-id="3478326516-43">(</span><span class="p" data-group-id="3478326516-43">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="3478326516-42">}</span><span class="p">,</span><span class="w">
│ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7664791780-42">{</span><span class="nf">self</span><span class="p" data-group-id="7664791780-43">(</span><span class="p" data-group-id="7664791780-43">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="7664791780-42">}</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="3478326516-44">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="3478326516-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="nf">exit</span><span class="p" data-group-id="3478326516-45">(</span><span class="ss">normal</span><span class="p" data-group-id="3478326516-45">)</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="7664791780-44">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="7664791780-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="nf">exit</span><span class="p" data-group-id="7664791780-45">(</span><span class="ss">normal</span><span class="p" data-group-id="7664791780-45">)</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="3478326516-46">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="3478326516-46">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3478326516-47">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3478326516-48">[</span><span class="n">Reason</span><span class="p" data-group-id="3478326516-48">]</span><span class="p" data-group-id="3478326516-47">)</span><span class="p">,</span><span class="w">
│ │ │ -	    </span><span class="nf">exit</span><span class="p" data-group-id="3478326516-49">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="3478326516-49">)</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="7664791780-46">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="7664791780-46">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7664791780-47">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7664791780-48">[</span><span class="n">Reason</span><span class="p" data-group-id="7664791780-48">]</span><span class="p" data-group-id="7664791780-47">)</span><span class="p">,</span><span class="w">
│ │ │ +	    </span><span class="nf">exit</span><span class="p" data-group-id="7664791780-49">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="7664791780-49">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="3478326516-50">(</span><span class="p" data-group-id="3478326516-51">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="3478326516-51">}</span><span class="p" data-group-id="3478326516-50">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3478326516-52">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="3478326516-52">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="3478326516-53">(</span><span class="p" data-group-id="3478326516-54">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3478326516-54">}</span><span class="p" data-group-id="3478326516-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3478326516-55">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3478326516-55">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="7664791780-50">(</span><span class="p" data-group-id="7664791780-51">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="7664791780-51">}</span><span class="p" data-group-id="7664791780-50">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7664791780-52">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="7664791780-52">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="7664791780-53">(</span><span class="p" data-group-id="7664791780-54">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7664791780-54">}</span><span class="p" data-group-id="7664791780-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7664791780-55">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7664791780-55">]</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="3478326516-56">(</span><span class="p" data-group-id="3478326516-57">[</span><span class="n">Int</span><span class="p" data-group-id="3478326516-57">]</span><span class="p" data-group-id="3478326516-56">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><h2 id="c-driver" class="section-heading">
│ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="7664791780-56">(</span><span class="p" data-group-id="7664791780-57">[</span><span class="n">Int</span><span class="p" data-group-id="7664791780-57">]</span><span class="p" data-group-id="7664791780-56">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><h2 id="c-driver" class="section-heading">
│ │ │    <a href="#c-driver" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">C Driver</span>
│ │ │  </h2>
│ │ │  <p>The C driver is a module that is compiled and linked into a shared library. It
│ │ │  uses a driver structure and includes the header file <code class="inline">erl_driver.h</code>.</p><p>The driver structure is filled with the driver name and function pointers. It is
│ │ │ @@ -347,25 +347,25 @@
│ │ │    <a href="#running-the-example" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Running the Example</span>
│ │ │  </h2>
│ │ │  <p><em>Step 1.</em> Compile the C code:</p><pre><code class="text">unix&gt; gcc -o example_drv.so -fpic -shared complex.c port_driver.c
│ │ │  windows&gt; cl -LD -MD -Fe example_drv.dll complex.c port_driver.c</code></pre><p><em>Step 2.</em> Start Erlang and compile the Erlang code:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="ss">erl</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="7257435821-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="7257435821-1">]</span><span class="w"> </span><span class="p" data-group-id="7257435821-2">[</span><span class="ss">source</span><span class="p" data-group-id="7257435821-2">]</span><span class="w"> </span><span class="p" data-group-id="7257435821-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="7257435821-3">]</span><span class="w"> </span><span class="p" data-group-id="7257435821-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="7257435821-4">]</span><span class="w"> </span><span class="p" data-group-id="7257435821-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="7257435821-5">]</span><span class="w"> </span><span class="p" data-group-id="7257435821-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="7257435821-6">]</span><span class="w"> </span><span class="p" data-group-id="7257435821-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="7257435821-7">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="4568134323-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="4568134323-1">]</span><span class="w"> </span><span class="p" data-group-id="4568134323-2">[</span><span class="ss">source</span><span class="p" data-group-id="4568134323-2">]</span><span class="w"> </span><span class="p" data-group-id="4568134323-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="4568134323-3">]</span><span class="w"> </span><span class="p" data-group-id="4568134323-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="4568134323-4">]</span><span class="w"> </span><span class="p" data-group-id="4568134323-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="4568134323-5">]</span><span class="w"> </span><span class="p" data-group-id="4568134323-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4568134323-6">]</span><span class="w"> </span><span class="p" data-group-id="4568134323-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="4568134323-7">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="7257435821-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="7257435821-9">(</span><span class="p" data-group-id="7257435821-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="7257435821-8">)</span><span class="w">
│ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="7257435821-10">(</span><span class="ss">complex5</span><span class="p" data-group-id="7257435821-10">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7257435821-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex5</span><span class="p" data-group-id="7257435821-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1018817403-1">(</span><span class="s">&quot;example_drv&quot;</span><span class="p" data-group-id="1018817403-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="4568134323-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="4568134323-9">(</span><span class="p" data-group-id="4568134323-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="4568134323-8">)</span><span class="w">
│ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="4568134323-10">(</span><span class="ss">complex5</span><span class="p" data-group-id="4568134323-10">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4568134323-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex5</span><span class="p" data-group-id="4568134323-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1391989848-1">(</span><span class="s">&quot;example_drv&quot;</span><span class="p" data-group-id="1391989848-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.34</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="1018817403-2">(</span><span class="mi">3</span><span class="p" data-group-id="1018817403-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="1391989848-2">(</span><span class="mi">3</span><span class="p" data-group-id="1391989848-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="1018817403-3">(</span><span class="mi">5</span><span class="p" data-group-id="1018817403-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="1391989848-3">(</span><span class="mi">5</span><span class="p" data-group-id="1391989848-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">10</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="1018817403-4">(</span><span class="p" data-group-id="1018817403-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="1391989848-4">(</span><span class="p" data-group-id="1391989848-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">stop</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="erl_interface.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/code_loading.html
│ │ │ @@ -122,16 +122,16 @@
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Compilation</span>
│ │ │  </h2>
│ │ │  <p>Erlang programs must be <em>compiled</em> to object code. The compiler can generate a
│ │ │  new file that contains the object code. The current abstract machine, which runs
│ │ │  the object code, is called BEAM and therefore the object files get the suffix
│ │ │ -<code class="inline">.beam</code>. The compiler can also generate a binary which can be loaded directly.</p><p>The compiler is located in the module <a href="../../lib/compiler-10.0/doc/html/compile.html"><code class="inline">compile</code></a> in Compiler.</p><pre><code class="makeup erlang" translate="no"><span class="nc">compile</span><span class="p">:</span><span class="nf">file</span><span class="p" data-group-id="3707243024-1">(</span><span class="n">Module</span><span class="p" data-group-id="3707243024-1">)</span><span class="w">
│ │ │ -</span><span class="nc">compile</span><span class="p">:</span><span class="nf">file</span><span class="p" data-group-id="3707243024-2">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="3707243024-2">)</span></code></pre><p>The Erlang shell understands the command <code class="inline">c(Module)</code>, which both compiles and
│ │ │ +<code class="inline">.beam</code>. The compiler can also generate a binary which can be loaded directly.</p><p>The compiler is located in the module <a href="../../lib/compiler-10.0/doc/html/compile.html"><code class="inline">compile</code></a> in Compiler.</p><pre><code class="makeup erlang" translate="no"><span class="nc">compile</span><span class="p">:</span><span class="nf">file</span><span class="p" data-group-id="8122848135-1">(</span><span class="n">Module</span><span class="p" data-group-id="8122848135-1">)</span><span class="w">
│ │ │ +</span><span class="nc">compile</span><span class="p">:</span><span class="nf">file</span><span class="p" data-group-id="8122848135-2">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="8122848135-2">)</span></code></pre><p>The Erlang shell understands the command <code class="inline">c(Module)</code>, which both compiles and
│ │ │  loads <code class="inline">Module</code>.</p><p>There is also a module <code class="inline">make</code>, which provides a set of functions similar to the
│ │ │  UNIX type Make functions, see module <a href="../../lib/tools-4.2/doc/html/make.html"><code class="inline">make</code></a> in Tools.</p><p>The compiler can also be accessed from the OS prompt using the
│ │ │  <a href="../../erts-17.0/doc/html/erl_cmd.html">erl</a> executable in ERTS.</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -compile Module1...ModuleN</span><span class="w">
│ │ │  </span><span class="c1">% erl -make</span></code></pre><p>The <code class="inline">erlc</code> program provides a way to compile modules from the OS
│ │ │  shell, see the <a href="../../erts-17.0/doc/html/erlc_cmd.html">erlc</a> executable in ERTS. It
│ │ │  understands a number of flags that can be used to define macros, add search
│ │ │  paths for include files, and more.</p><pre><code class="text">% erlc &lt;flags&gt; File1.erl...FileN.erl</code></pre><p><a href="" id="loading"></a></p><h2 id="code-loading" class="section-heading">
│ │ │ @@ -156,54 +156,54 @@
│ │ │  When a module is loaded into the system for the first time, the code becomes
│ │ │  'current'. If then a new instance of the module is loaded, the code of the
│ │ │  previous instance becomes 'old' and the new instance becomes 'current'.</p><p>Both old and current code are valid, and can be evaluated concurrently. Fully
│ │ │  qualified function calls always refer to current code. Old code can still be
│ │ │  evaluated because of processes lingering in the old code.</p><p>If a third instance of the module is loaded, the code server removes (purges)
│ │ │  the old code and any processes lingering in it are terminated. Then the third
│ │ │  instance becomes 'current' and the previously current code becomes 'old'.</p><p>To change from old code to current code, a process must make a fully qualified
│ │ │ -function call.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8492421993-1">(</span><span class="ss">m</span><span class="p" data-group-id="8492421993-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8492421993-2">(</span><span class="p" data-group-id="8492421993-3">[</span><span class="ss">loop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8492421993-3">]</span><span class="p" data-group-id="8492421993-2">)</span><span class="p">.</span><span class="w">
│ │ │ +function call.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1835460289-1">(</span><span class="ss">m</span><span class="p" data-group-id="1835460289-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1835460289-2">(</span><span class="p" data-group-id="1835460289-3">[</span><span class="ss">loop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1835460289-3">]</span><span class="p" data-group-id="1835460289-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="8492421993-4">(</span><span class="p" data-group-id="8492421993-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="1835460289-4">(</span><span class="p" data-group-id="1835460289-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">code_switch</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">m</span><span class="p">:</span><span class="nf">loop</span><span class="p" data-group-id="8492421993-5">(</span><span class="p" data-group-id="8492421993-5">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="nc">m</span><span class="p">:</span><span class="nf">loop</span><span class="p" data-group-id="1835460289-5">(</span><span class="p" data-group-id="1835460289-5">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="n">Msg</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="8492421993-6">(</span><span class="p" data-group-id="8492421993-6">)</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="1835460289-6">(</span><span class="p" data-group-id="1835460289-6">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>To make the process change code, send the message <code class="inline">code_switch</code> to it. The
│ │ │  process then makes a fully qualified call to <code class="inline">m:loop()</code> and changes to current
│ │ │  code. Notice that <code class="inline">m:loop/0</code> must be exported.</p><p>For code replacement of funs to work, use the syntax
│ │ │  <code class="inline">fun Module:FunctionName/Arity</code>.</p><p><a href="" id="on_load"></a></p><h2 id="running-a-function-when-a-module-is-loaded" class="section-heading">
│ │ │    <a href="#running-a-function-when-a-module-is-loaded" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Running a Function When a Module is Loaded</span>
│ │ │  </h2>
│ │ │  <p>The <code class="inline">-on_load()</code> directive names a function that is to be run automatically when
│ │ │ -a module is loaded.</p><p>Its syntax is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="7575893821-1">(</span><span class="n">Name</span><span class="o">/</span><span class="mi">0</span><span class="p" data-group-id="7575893821-1">)</span><span class="p">.</span></code></pre><p>It is not necessary to export the function. It is called in a freshly spawned
│ │ │ +a module is loaded.</p><p>Its syntax is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="7838486752-1">(</span><span class="n">Name</span><span class="o">/</span><span class="mi">0</span><span class="p" data-group-id="7838486752-1">)</span><span class="p">.</span></code></pre><p>It is not necessary to export the function. It is called in a freshly spawned
│ │ │  process (which terminates as soon as the function returns).</p><p>The function must return <code class="inline">ok</code> if the module is to become the new current code
│ │ │  for the module and become callable.</p><p>Returning any other value or generating an exception causes the new code to be
│ │ │  unloaded. If the return value is not an atom, a warning error report is sent to
│ │ │  the error logger.</p><p>If there already is current code for the module, that code will remain current
│ │ │  and can be called until the <code class="inline">on_load</code> function has returned. If the <code class="inline">on_load</code>
│ │ │  function fails, the current code (if any) will remain current. If there is no
│ │ │  current code for a module, any process that makes an external call to the module
│ │ │  before the <code class="inline">on_load</code> function has finished will be suspended until the <code class="inline">on_load</code>
│ │ │  function has finished.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 19, if the <code class="inline">on_load</code> function failed, any previously current
│ │ │  code would become old, essentially leaving the system without any working and
│ │ │  reachable instance of the module.</p></section><p>In embedded mode, first all modules are loaded. Then all <code class="inline">on_load</code> functions are
│ │ │  called. The system is terminated unless all of the <code class="inline">on_load</code> functions return
│ │ │ -<code class="inline">ok</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5235332834-1">(</span><span class="ss">m</span><span class="p" data-group-id="5235332834-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="5235332834-2">(</span><span class="ss">load_my_nifs</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5235332834-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">ok</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5222213879-1">(</span><span class="ss">m</span><span class="p" data-group-id="5222213879-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="5222213879-2">(</span><span class="ss">load_my_nifs</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5222213879-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">load_my_nifs</span><span class="p" data-group-id="5235332834-3">(</span><span class="p" data-group-id="5235332834-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">load_my_nifs</span><span class="p" data-group-id="5222213879-3">(</span><span class="p" data-group-id="5222213879-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">NifPath</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">    </span><span class="c1">%Set up the path to the NIF library.</span><span class="w">
│ │ │      </span><span class="n">Info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">       </span><span class="c1">%Initialize the Info term</span><span class="w">
│ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="5235332834-4">(</span><span class="n">NifPath</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p" data-group-id="5235332834-4">)</span><span class="p">.</span></code></pre><p>If the call to <a href="../../erts-17.0/doc/html/erlang.html#load_nif/2"><code class="inline">erlang:load_nif/2</code></a> fails, the module is unloaded and a warning
│ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="5222213879-4">(</span><span class="n">NifPath</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p" data-group-id="5222213879-4">)</span><span class="p">.</span></code></pre><p>If the call to <a href="../../erts-17.0/doc/html/erlang.html#load_nif/2"><code class="inline">erlang:load_nif/2</code></a> fails, the module is unloaded and a warning
│ │ │  report is sent to the error logger.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="distributed.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/commoncaveats.html
│ │ │ @@ -118,31 +118,31 @@
│ │ │  <p>This section lists a few constructs to watch out for.</p><h2 id="operator" class="section-heading">
│ │ │    <a href="#operator" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Operator <code class="inline">++</code></span>
│ │ │  </h2>
│ │ │  <p>The <code class="inline">++</code> operator copies its left-hand side operand. That is clearly
│ │ │ -seen if we do our own implementation in Erlang:</p><pre><code class="makeup erlang" translate="no"><span class="nf">my_plus_plus</span><span class="p" data-group-id="2045110797-1">(</span><span class="p" data-group-id="2045110797-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2045110797-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="2045110797-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2045110797-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_plus_plus</span><span class="p" data-group-id="2045110797-4">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="2045110797-4">)</span><span class="p" data-group-id="2045110797-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">my_plus_plus</span><span class="p" data-group-id="2045110797-5">(</span><span class="p" data-group-id="2045110797-6">[</span><span class="p" data-group-id="2045110797-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="2045110797-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Tail</span><span class="p">.</span></code></pre><p>We must be careful how we use <code class="inline">++</code> in a loop. First is how not to use it:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">naive_reverse</span><span class="p" data-group-id="4012487050-1">(</span><span class="p" data-group-id="4012487050-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4012487050-2">]</span><span class="p" data-group-id="4012487050-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">naive_reverse</span><span class="p" data-group-id="4012487050-3">(</span><span class="n">T</span><span class="p" data-group-id="4012487050-3">)</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="4012487050-4">[</span><span class="n">H</span><span class="p" data-group-id="4012487050-4">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">naive_reverse</span><span class="p" data-group-id="4012487050-5">(</span><span class="p" data-group-id="4012487050-6">[</span><span class="p" data-group-id="4012487050-6">]</span><span class="p" data-group-id="4012487050-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4012487050-7">[</span><span class="p" data-group-id="4012487050-7">]</span><span class="p">.</span></code></pre><p>As the <code class="inline">++</code> operator copies its left-hand side operand, the growing
│ │ │ -result is copied repeatedly, leading to quadratic complexity.</p><p>On the other hand, using <code class="inline">++</code> in a loop like this is perfectly fine:</p><p><strong>OK</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="1248839605-1">(</span><span class="n">List</span><span class="p" data-group-id="1248839605-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="1248839605-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1248839605-3">[</span><span class="p" data-group-id="1248839605-3">]</span><span class="p" data-group-id="1248839605-2">)</span><span class="p">.</span><span class="w">
│ │ │ +seen if we do our own implementation in Erlang:</p><pre><code class="makeup erlang" translate="no"><span class="nf">my_plus_plus</span><span class="p" data-group-id="4592116571-1">(</span><span class="p" data-group-id="4592116571-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4592116571-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="4592116571-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4592116571-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_plus_plus</span><span class="p" data-group-id="4592116571-4">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="4592116571-4">)</span><span class="p" data-group-id="4592116571-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">my_plus_plus</span><span class="p" data-group-id="4592116571-5">(</span><span class="p" data-group-id="4592116571-6">[</span><span class="p" data-group-id="4592116571-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="4592116571-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Tail</span><span class="p">.</span></code></pre><p>We must be careful how we use <code class="inline">++</code> in a loop. First is how not to use it:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">naive_reverse</span><span class="p" data-group-id="4777315048-1">(</span><span class="p" data-group-id="4777315048-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4777315048-2">]</span><span class="p" data-group-id="4777315048-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">naive_reverse</span><span class="p" data-group-id="4777315048-3">(</span><span class="n">T</span><span class="p" data-group-id="4777315048-3">)</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="4777315048-4">[</span><span class="n">H</span><span class="p" data-group-id="4777315048-4">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">naive_reverse</span><span class="p" data-group-id="4777315048-5">(</span><span class="p" data-group-id="4777315048-6">[</span><span class="p" data-group-id="4777315048-6">]</span><span class="p" data-group-id="4777315048-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4777315048-7">[</span><span class="p" data-group-id="4777315048-7">]</span><span class="p">.</span></code></pre><p>As the <code class="inline">++</code> operator copies its left-hand side operand, the growing
│ │ │ +result is copied repeatedly, leading to quadratic complexity.</p><p>On the other hand, using <code class="inline">++</code> in a loop like this is perfectly fine:</p><p><strong>OK</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="3592347644-1">(</span><span class="n">List</span><span class="p" data-group-id="3592347644-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="3592347644-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3592347644-3">[</span><span class="p" data-group-id="3592347644-3">]</span><span class="p" data-group-id="3592347644-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="1248839605-4">(</span><span class="p" data-group-id="1248839605-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1248839605-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="1248839605-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="1248839605-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1248839605-7">[</span><span class="n">H</span><span class="p" data-group-id="1248839605-7">]</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="1248839605-6">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="1248839605-8">(</span><span class="p" data-group-id="1248839605-9">[</span><span class="p" data-group-id="1248839605-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="1248839605-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="3592347644-4">(</span><span class="p" data-group-id="3592347644-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3592347644-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3592347644-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="3592347644-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3592347644-7">[</span><span class="n">H</span><span class="p" data-group-id="3592347644-7">]</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3592347644-6">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="3592347644-8">(</span><span class="p" data-group-id="3592347644-9">[</span><span class="p" data-group-id="3592347644-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3592347644-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>Each list element is copied only once. The growing result <code class="inline">Acc</code> is the right-hand
│ │ │ -side operand, which is <em>not</em> copied.</p><p>Experienced Erlang programmers would probably write as follows:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">vanilla_reverse</span><span class="p" data-group-id="0676959861-1">(</span><span class="p" data-group-id="0676959861-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0676959861-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="0676959861-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">vanilla_reverse</span><span class="p" data-group-id="0676959861-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0676959861-4">[</span><span class="n">H</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="0676959861-4">]</span><span class="p" data-group-id="0676959861-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">vanilla_reverse</span><span class="p" data-group-id="0676959861-5">(</span><span class="p" data-group-id="0676959861-6">[</span><span class="p" data-group-id="0676959861-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="0676959861-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +side operand, which is <em>not</em> copied.</p><p>Experienced Erlang programmers would probably write as follows:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">vanilla_reverse</span><span class="p" data-group-id="6557733786-1">(</span><span class="p" data-group-id="6557733786-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6557733786-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6557733786-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">vanilla_reverse</span><span class="p" data-group-id="6557733786-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6557733786-4">[</span><span class="n">H</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="6557733786-4">]</span><span class="p" data-group-id="6557733786-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">vanilla_reverse</span><span class="p" data-group-id="6557733786-5">(</span><span class="p" data-group-id="6557733786-6">[</span><span class="p" data-group-id="6557733786-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6557733786-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>In principle, this is slightly more efficient because the list element <code class="inline">[H]</code>
│ │ │  is not built before being copied and discarded. In practice, the compiler
│ │ │  rewrites <code class="inline">[H] ++ Acc</code> to <code class="inline">[H|Acc]</code>.</p><h2 id="timer-module" class="section-heading">
│ │ │    <a href="#timer-module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Timer Module</span>
│ │ │ @@ -160,49 +160,49 @@
│ │ │  therefore harmless.</p><h2 id="accidental-copying-and-loss-of-sharing" class="section-heading">
│ │ │    <a href="#accidental-copying-and-loss-of-sharing" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Accidental Copying and Loss of Sharing</span>
│ │ │  </h2>
│ │ │  <p>When spawning a new process using a fun, one can accidentally copy more data to
│ │ │ -the process than intended. For example:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">accidental1</span><span class="p" data-group-id="3769830657-1">(</span><span class="n">State</span><span class="p" data-group-id="3769830657-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="3769830657-2">(</span><span class="nf">fun</span><span class="p" data-group-id="3769830657-3">(</span><span class="p" data-group-id="3769830657-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3769830657-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3769830657-5">[</span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">info</span><span class="p" data-group-id="3769830657-5">]</span><span class="p" data-group-id="3769830657-4">)</span><span class="w">
│ │ │ -          </span><span class="k">end</span><span class="p" data-group-id="3769830657-2">)</span><span class="p">.</span></code></pre><p>The code in the fun will extract one element from the record and print it. The
│ │ │ +the process than intended. For example:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">accidental1</span><span class="p" data-group-id="5707264425-1">(</span><span class="n">State</span><span class="p" data-group-id="5707264425-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="5707264425-2">(</span><span class="nf">fun</span><span class="p" data-group-id="5707264425-3">(</span><span class="p" data-group-id="5707264425-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5707264425-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5707264425-5">[</span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">info</span><span class="p" data-group-id="5707264425-5">]</span><span class="p" data-group-id="5707264425-4">)</span><span class="w">
│ │ │ +          </span><span class="k">end</span><span class="p" data-group-id="5707264425-2">)</span><span class="p">.</span></code></pre><p>The code in the fun will extract one element from the record and print it. The
│ │ │  rest of the <code class="inline">state</code> record is not used. However, when the <a href="../../erts-17.0/doc/html/erlang.html#spawn/1"><code class="inline">spawn/1</code></a>
│ │ │ -function is executed, the entire record is copied to the newly created process.</p><p>The same kind of problem can happen with a map:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">accidental2</span><span class="p" data-group-id="5188968774-1">(</span><span class="n">State</span><span class="p" data-group-id="5188968774-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="5188968774-2">(</span><span class="nf">fun</span><span class="p" data-group-id="5188968774-3">(</span><span class="p" data-group-id="5188968774-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5188968774-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5188968774-5">[</span><span class="nf">map_get</span><span class="p" data-group-id="5188968774-6">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5188968774-6">)</span><span class="p" data-group-id="5188968774-5">]</span><span class="p" data-group-id="5188968774-4">)</span><span class="w">
│ │ │ -          </span><span class="k">end</span><span class="p" data-group-id="5188968774-2">)</span><span class="p">.</span></code></pre><p>In the following example (part of a module implementing the <a href="../../lib/stdlib-8.0/doc/html/gen_server.html"><code class="inline">gen_server</code></a>
│ │ │ -behavior) the created fun is sent to another process:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_call</span><span class="p" data-group-id="4114451759-1">(</span><span class="ss">give_me_a_fun</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4114451759-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="4114451759-2">(</span><span class="p" data-group-id="4114451759-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="nb">size</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4114451759-3">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4114451759-3">}</span><span class="p">.</span></code></pre><p>How bad that unnecessary copy is depends on the contents of the record or the
│ │ │ -map.</p><p>For example, if the <code class="inline">state</code> record is initialized like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init1</span><span class="p" data-group-id="8993739540-1">(</span><span class="p" data-group-id="8993739540-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="8993739540-2">{</span><span class="ss">data</span><span class="o">=</span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="8993739540-3">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">10000</span><span class="p" data-group-id="8993739540-3">)</span><span class="p" data-group-id="8993739540-2">}</span><span class="p">.</span></code></pre><p>a list with 10000 elements (or about 20000 heap words) will be copied to the
│ │ │ +function is executed, the entire record is copied to the newly created process.</p><p>The same kind of problem can happen with a map:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">accidental2</span><span class="p" data-group-id="4330552339-1">(</span><span class="n">State</span><span class="p" data-group-id="4330552339-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="4330552339-2">(</span><span class="nf">fun</span><span class="p" data-group-id="4330552339-3">(</span><span class="p" data-group-id="4330552339-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4330552339-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4330552339-5">[</span><span class="nf">map_get</span><span class="p" data-group-id="4330552339-6">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4330552339-6">)</span><span class="p" data-group-id="4330552339-5">]</span><span class="p" data-group-id="4330552339-4">)</span><span class="w">
│ │ │ +          </span><span class="k">end</span><span class="p" data-group-id="4330552339-2">)</span><span class="p">.</span></code></pre><p>In the following example (part of a module implementing the <a href="../../lib/stdlib-8.0/doc/html/gen_server.html"><code class="inline">gen_server</code></a>
│ │ │ +behavior) the created fun is sent to another process:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_call</span><span class="p" data-group-id="5083580888-1">(</span><span class="ss">give_me_a_fun</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5083580888-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="5083580888-2">(</span><span class="p" data-group-id="5083580888-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="nb">size</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5083580888-3">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5083580888-3">}</span><span class="p">.</span></code></pre><p>How bad that unnecessary copy is depends on the contents of the record or the
│ │ │ +map.</p><p>For example, if the <code class="inline">state</code> record is initialized like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init1</span><span class="p" data-group-id="3569416543-1">(</span><span class="p" data-group-id="3569416543-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="3569416543-2">{</span><span class="ss">data</span><span class="o">=</span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="3569416543-3">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">10000</span><span class="p" data-group-id="3569416543-3">)</span><span class="p" data-group-id="3569416543-2">}</span><span class="p">.</span></code></pre><p>a list with 10000 elements (or about 20000 heap words) will be copied to the
│ │ │  newly created process.</p><p>An unnecessary copy of 10000 element list can be bad enough, but it can get even
│ │ │  worse if the <code class="inline">state</code> record contains <em>shared subterms</em>. Here is a simple example
│ │ │ -of a term with a shared subterm:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6636376793-1">{</span><span class="n">SubTerm</span><span class="p">,</span><span class="w"> </span><span class="n">SubTerm</span><span class="p" data-group-id="6636376793-1">}</span></code></pre><p>When a term is copied to another process, sharing of subterms will be lost and
│ │ │ -the copied term can be many times larger than the original term. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init2</span><span class="p" data-group-id="2388502474-1">(</span><span class="p" data-group-id="2388502474-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SharedSubTerms</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="2388502474-2">(</span><span class="nf">fun</span><span class="p" data-group-id="2388502474-3">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="2388502474-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2388502474-4">[</span><span class="n">A</span><span class="p">|</span><span class="n">A</span><span class="p" data-group-id="2388502474-4">]</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2388502474-5">[</span><span class="mi">0</span><span class="p" data-group-id="2388502474-5">]</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="2388502474-6">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">15</span><span class="p" data-group-id="2388502474-6">)</span><span class="p" data-group-id="2388502474-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="2388502474-7">{</span><span class="ss">data</span><span class="o">=</span><span class="n">SharedSubTerms</span><span class="p" data-group-id="2388502474-7">}</span><span class="p">.</span></code></pre><p>In the process that calls <code class="inline">init2/0</code>, the size of the <code class="inline">data</code> field in the <code class="inline">state</code>
│ │ │ +of a term with a shared subterm:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9311830599-1">{</span><span class="n">SubTerm</span><span class="p">,</span><span class="w"> </span><span class="n">SubTerm</span><span class="p" data-group-id="9311830599-1">}</span></code></pre><p>When a term is copied to another process, sharing of subterms will be lost and
│ │ │ +the copied term can be many times larger than the original term. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init2</span><span class="p" data-group-id="8159624578-1">(</span><span class="p" data-group-id="8159624578-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SharedSubTerms</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="8159624578-2">(</span><span class="nf">fun</span><span class="p" data-group-id="8159624578-3">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="8159624578-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8159624578-4">[</span><span class="n">A</span><span class="p">|</span><span class="n">A</span><span class="p" data-group-id="8159624578-4">]</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8159624578-5">[</span><span class="mi">0</span><span class="p" data-group-id="8159624578-5">]</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="8159624578-6">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">15</span><span class="p" data-group-id="8159624578-6">)</span><span class="p" data-group-id="8159624578-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="8159624578-7">{</span><span class="ss">data</span><span class="o">=</span><span class="n">SharedSubTerms</span><span class="p" data-group-id="8159624578-7">}</span><span class="p">.</span></code></pre><p>In the process that calls <code class="inline">init2/0</code>, the size of the <code class="inline">data</code> field in the <code class="inline">state</code>
│ │ │  record will be 32 heap words. When the record is copied to the newly created
│ │ │  process, sharing will be lost and the size of the copied <code class="inline">data</code> field will be
│ │ │  131070 heap words. More details about
│ │ │  <a href="eff_guide_processes.html#loss-of-sharing">loss of sharing</a> are found in a later
│ │ │  section.</p><p>To avoid the problem, outside of the fun extract only the fields of the record
│ │ │ -that are actually used:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">fixed_accidental1</span><span class="p" data-group-id="5639138510-1">(</span><span class="n">State</span><span class="p" data-group-id="5639138510-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +that are actually used:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">fixed_accidental1</span><span class="p" data-group-id="8239319898-1">(</span><span class="n">State</span><span class="p" data-group-id="8239319898-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">info</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="5639138510-2">(</span><span class="nf">fun</span><span class="p" data-group-id="5639138510-3">(</span><span class="p" data-group-id="5639138510-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5639138510-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5639138510-5">[</span><span class="n">Info</span><span class="p" data-group-id="5639138510-5">]</span><span class="p" data-group-id="5639138510-4">)</span><span class="w">
│ │ │ -          </span><span class="k">end</span><span class="p" data-group-id="5639138510-2">)</span><span class="p">.</span></code></pre><p>Similarly, outside of the fun extract only the map elements that are actually
│ │ │ -used:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">fixed_accidental2</span><span class="p" data-group-id="5939711705-1">(</span><span class="n">State</span><span class="p" data-group-id="5939711705-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">map_get</span><span class="p" data-group-id="5939711705-2">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5939711705-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="5939711705-3">(</span><span class="nf">fun</span><span class="p" data-group-id="5939711705-4">(</span><span class="p" data-group-id="5939711705-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5939711705-5">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5939711705-6">[</span><span class="n">Info</span><span class="p" data-group-id="5939711705-6">]</span><span class="p" data-group-id="5939711705-5">)</span><span class="w">
│ │ │ -          </span><span class="k">end</span><span class="p" data-group-id="5939711705-3">)</span><span class="p">.</span></code></pre><h2 id="list_to_atom-1-binary_to_atom-1-2" class="section-heading">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="8239319898-2">(</span><span class="nf">fun</span><span class="p" data-group-id="8239319898-3">(</span><span class="p" data-group-id="8239319898-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8239319898-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8239319898-5">[</span><span class="n">Info</span><span class="p" data-group-id="8239319898-5">]</span><span class="p" data-group-id="8239319898-4">)</span><span class="w">
│ │ │ +          </span><span class="k">end</span><span class="p" data-group-id="8239319898-2">)</span><span class="p">.</span></code></pre><p>Similarly, outside of the fun extract only the map elements that are actually
│ │ │ +used:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">fixed_accidental2</span><span class="p" data-group-id="5520131356-1">(</span><span class="n">State</span><span class="p" data-group-id="5520131356-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">map_get</span><span class="p" data-group-id="5520131356-2">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5520131356-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="5520131356-3">(</span><span class="nf">fun</span><span class="p" data-group-id="5520131356-4">(</span><span class="p" data-group-id="5520131356-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5520131356-5">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5520131356-6">[</span><span class="n">Info</span><span class="p" data-group-id="5520131356-6">]</span><span class="p" data-group-id="5520131356-5">)</span><span class="w">
│ │ │ +          </span><span class="k">end</span><span class="p" data-group-id="5520131356-3">)</span><span class="p">.</span></code></pre><h2 id="list_to_atom-1-binary_to_atom-1-2" class="section-heading">
│ │ │    <a href="#list_to_atom-1-binary_to_atom-1-2" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">list_to_atom/1, binary_to_atom/1,2</span>
│ │ │  </h2>
│ │ │  <p>Atoms are not garbage-collected. Once an atom is created, it is never removed.
│ │ │  The emulator terminates if the limit for the number of atoms (1,048,576 by
│ │ │ @@ -211,28 +211,28 @@
│ │ │  input, <a href="../../erts-17.0/doc/html/erlang.html#list_to_existing_atom/1"><code class="inline">list_to_existing_atom/1</code></a>,
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#binary_to_existing_atom/1"><code class="inline">binary_to_existing_atom/1</code></a>, or
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#binary_to_existing_atom/2"><code class="inline">binary_to_existing_atom/2</code></a> can be used
│ │ │  to guard against a denial-of-service attack. All atoms that are allowed must
│ │ │  have been created earlier, for example, by using all of them in a module
│ │ │  and loading that module.</p><p>Using <a href="../../erts-17.0/doc/html/erlang.html#list_to_atom/1"><code class="inline">list_to_atom/1</code></a>, <a href="../../erts-17.0/doc/html/erlang.html#binary_to_atom/1"><code class="inline">binary_to_atom/1</code></a>, or
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#binary_to_atom/2"><code class="inline">binary_to_atom/2</code></a> to construct an atom that
│ │ │ -is passed to <a href="../../erts-17.0/doc/html/erlang.html#apply/3"><code class="inline">apply/3</code></a> is quite expensive.</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">apply</span><span class="p" data-group-id="7657101897-1">(</span><span class="nf">list_to_atom</span><span class="p" data-group-id="7657101897-2">(</span><span class="s">&quot;some_prefix&quot;</span><span class="o">++</span><span class="n">Var</span><span class="p" data-group-id="7657101897-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="7657101897-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">apply</span><span class="p" data-group-id="3956154490-1">(</span><span class="nf">binary_to_atom</span><span class="p" data-group-id="3956154490-2">(</span><span class="p" data-group-id="3956154490-3">&lt;&lt;</span><span class="s">&quot;some_prefix&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Var</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3956154490-3">&gt;&gt;</span><span class="p" data-group-id="3956154490-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="3956154490-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">apply</span><span class="p" data-group-id="6410570356-1">(</span><span class="nf">binary_to_atom</span><span class="p" data-group-id="6410570356-2">(</span><span class="p" data-group-id="6410570356-3">&lt;&lt;</span><span class="s">&quot;some_prefix&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Var</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6410570356-3">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="ss">utf8</span><span class="p" data-group-id="6410570356-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="6410570356-1">)</span></code></pre><h2 id="length-1" class="section-heading">
│ │ │ +is passed to <a href="../../erts-17.0/doc/html/erlang.html#apply/3"><code class="inline">apply/3</code></a> is quite expensive.</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">apply</span><span class="p" data-group-id="0568307424-1">(</span><span class="nf">list_to_atom</span><span class="p" data-group-id="0568307424-2">(</span><span class="s">&quot;some_prefix&quot;</span><span class="o">++</span><span class="n">Var</span><span class="p" data-group-id="0568307424-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="0568307424-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">apply</span><span class="p" data-group-id="2785092886-1">(</span><span class="nf">binary_to_atom</span><span class="p" data-group-id="2785092886-2">(</span><span class="p" data-group-id="2785092886-3">&lt;&lt;</span><span class="s">&quot;some_prefix&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Var</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2785092886-3">&gt;&gt;</span><span class="p" data-group-id="2785092886-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="2785092886-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">apply</span><span class="p" data-group-id="8172017285-1">(</span><span class="nf">binary_to_atom</span><span class="p" data-group-id="8172017285-2">(</span><span class="p" data-group-id="8172017285-3">&lt;&lt;</span><span class="s">&quot;some_prefix&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Var</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8172017285-3">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="ss">utf8</span><span class="p" data-group-id="8172017285-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="8172017285-1">)</span></code></pre><h2 id="length-1" class="section-heading">
│ │ │    <a href="#length-1" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">length/1</span>
│ │ │  </h2>
│ │ │  <p>The time for calculating the length of a list is proportional to the length of
│ │ │  the list, as opposed to <a href="../../erts-17.0/doc/html/erlang.html#tuple_size/1"><code class="inline">tuple_size/1</code></a>,
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#byte_size/1"><code class="inline">byte_size/1</code></a>, and <a href="../../erts-17.0/doc/html/erlang.html#bit_size/1"><code class="inline">bit_size/1</code></a>, which all
│ │ │  execute in constant time.</p><p>Normally, there is no need to worry about the speed of <a href="../../erts-17.0/doc/html/erlang.html#length/1"><code class="inline">length/1</code></a>,
│ │ │  because it is efficiently implemented in C. In time-critical code, you might
│ │ │  want to avoid it if the input list could potentially be very long.</p><p>Some uses of <a href="../../erts-17.0/doc/html/erlang.html#length/1"><code class="inline">length/1</code></a> can be replaced by matching. For example,
│ │ │ -the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="5065918959-1">(</span><span class="n">L</span><span class="p" data-group-id="5065918959-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="5065918959-2">(</span><span class="n">L</span><span class="p" data-group-id="5065918959-2">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>can be rewritten to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="7748945849-1">(</span><span class="p" data-group-id="7748945849-2">[</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="7748945849-2">]</span><span class="o">=</span><span class="n">L</span><span class="p" data-group-id="7748945849-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="8796480620-1">(</span><span class="n">L</span><span class="p" data-group-id="8796480620-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="8796480620-2">(</span><span class="n">L</span><span class="p" data-group-id="8796480620-2">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>can be rewritten to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="2120635059-1">(</span><span class="p" data-group-id="2120635059-2">[</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="2120635059-2">]</span><span class="o">=</span><span class="n">L</span><span class="p" data-group-id="2120635059-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>One slight difference is that <a href="../../erts-17.0/doc/html/erlang.html#length/1"><code class="inline">length(L)</code></a> fails if <code class="inline">L</code> is an
│ │ │  improper list, while the pattern in the second code fragment accepts an improper
│ │ │  list.</p><h2 id="setelement-3" class="section-heading">
│ │ │    <a href="#setelement-3" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">setelement/3</span>
│ │ │ @@ -243,18 +243,18 @@
│ │ │    <a href="#compiler-optimizations-of-setelement-3" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Compiler optimizations of setelement/3</span>
│ │ │  </h3>
│ │ │  <p>Under certain conditions, the compiler can coalesce multiple calls to
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> into a single operation, avoiding
│ │ │ -the cost of copying the tuple for each call.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">multiple_setelement</span><span class="p" data-group-id="9448319898-1">(</span><span class="n">T0</span><span class="p" data-group-id="9448319898-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">tuple_size</span><span class="p" data-group-id="9448319898-2">(</span><span class="n">T0</span><span class="p" data-group-id="9448319898-2">)</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">9</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">T1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="9448319898-3">(</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="n">T0</span><span class="p">,</span><span class="w"> </span><span class="ss">new_value</span><span class="p" data-group-id="9448319898-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">T2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="9448319898-4">(</span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p">,</span><span class="w"> </span><span class="ss">foobar</span><span class="p" data-group-id="9448319898-4">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">setelement</span><span class="p" data-group-id="9448319898-5">(</span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p" data-group-id="9448319898-5">)</span><span class="p">.</span></code></pre><p>The compiler will replace the three <a href="../../erts-17.0/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> calls with code that
│ │ │ +the cost of copying the tuple for each call.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">multiple_setelement</span><span class="p" data-group-id="7054464406-1">(</span><span class="n">T0</span><span class="p" data-group-id="7054464406-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">tuple_size</span><span class="p" data-group-id="7054464406-2">(</span><span class="n">T0</span><span class="p" data-group-id="7054464406-2">)</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">9</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">T1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="7054464406-3">(</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="n">T0</span><span class="p">,</span><span class="w"> </span><span class="ss">new_value</span><span class="p" data-group-id="7054464406-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">T2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="7054464406-4">(</span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p">,</span><span class="w"> </span><span class="ss">foobar</span><span class="p" data-group-id="7054464406-4">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">setelement</span><span class="p" data-group-id="7054464406-5">(</span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p" data-group-id="7054464406-5">)</span><span class="p">.</span></code></pre><p>The compiler will replace the three <a href="../../erts-17.0/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> calls with code that
│ │ │  copies the tuple once and updates the elements at positions 5, 7, and 9.</p><p>Starting with Erlang/OTP 26, the following conditions must be met for
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> calls to be coalesced into a single
│ │ │  operation:</p><ul><li><p>The tuple argument must be known at compile time to be a tuple of a
│ │ │  specific size.</p></li><li><p>The element indices must be integer literals, not variables or expressions.</p></li><li><p>There must be no intervening expressions between the calls to
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a>.</p></li><li><p>The tuple returned from one <a href="../../erts-17.0/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> call must be
│ │ │  used only in the subsequent <a href="../../erts-17.0/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> call.</p></li></ul><p>Before Erlang/OTP 26, an additional condition was that
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> calls had to be made in descending
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/conc_prog.html
│ │ │ @@ -132,107 +132,107 @@
│ │ │  threads of execution in an Erlang program and to allow these threads to
│ │ │  communicate with each other. In Erlang, each thread of execution is called a
│ │ │  <em>process</em>.</p><p>(Aside: the term &quot;process&quot; is usually used when the threads of execution share
│ │ │  no data with each other and the term &quot;thread&quot; when they share data in some way.
│ │ │  Threads of execution in Erlang share no data, that is why they are called
│ │ │  processes).</p><p>The Erlang BIF <code class="inline">spawn</code> is used to create a new process:
│ │ │  <code class="inline">spawn(Module, Exported_Function, List of Arguments)</code>. Consider the following
│ │ │ -module:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3436740377-1">(</span><span class="ss">tut14</span><span class="p" data-group-id="3436740377-1">)</span><span class="p">.</span><span class="w">
│ │ │ +module:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4080385404-1">(</span><span class="ss">tut14</span><span class="p" data-group-id="4080385404-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3436740377-2">(</span><span class="p" data-group-id="3436740377-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3436740377-3">]</span><span class="p" data-group-id="3436740377-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4080385404-2">(</span><span class="p" data-group-id="4080385404-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4080385404-3">]</span><span class="p" data-group-id="4080385404-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">say_something</span><span class="p" data-group-id="3436740377-4">(</span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="3436740377-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">say_something</span><span class="p" data-group-id="4080385404-4">(</span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="4080385404-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">done</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">say_something</span><span class="p" data-group-id="3436740377-5">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="n">Times</span><span class="p" data-group-id="3436740377-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3436740377-6">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3436740377-7">[</span><span class="n">What</span><span class="p" data-group-id="3436740377-7">]</span><span class="p" data-group-id="3436740377-6">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">say_something</span><span class="p" data-group-id="3436740377-8">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="n">Times</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="3436740377-8">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="3436740377-9">(</span><span class="p" data-group-id="3436740377-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="3436740377-10">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3436740377-11">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3436740377-11">]</span><span class="p" data-group-id="3436740377-10">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="3436740377-12">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3436740377-13">[</span><span class="ss">goodbye</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3436740377-13">]</span><span class="p" data-group-id="3436740377-12">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nf">c</span><span class="p" data-group-id="8042246481-1">(</span><span class="ss">tut14</span><span class="p" data-group-id="8042246481-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8042246481-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut14</span><span class="p" data-group-id="8042246481-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nc">tut14</span><span class="p">:</span><span class="nf">say_something</span><span class="p" data-group-id="8042246481-3">(</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="8042246481-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">say_something</span><span class="p" data-group-id="4080385404-5">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="n">Times</span><span class="p" data-group-id="4080385404-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4080385404-6">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4080385404-7">[</span><span class="n">What</span><span class="p" data-group-id="4080385404-7">]</span><span class="p" data-group-id="4080385404-6">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">say_something</span><span class="p" data-group-id="4080385404-8">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="n">Times</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="4080385404-8">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="4080385404-9">(</span><span class="p" data-group-id="4080385404-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="4080385404-10">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4080385404-11">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="4080385404-11">]</span><span class="p" data-group-id="4080385404-10">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="4080385404-12">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4080385404-13">[</span><span class="ss">goodbye</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="4080385404-13">]</span><span class="p" data-group-id="4080385404-12">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nf">c</span><span class="p" data-group-id="8626479935-1">(</span><span class="ss">tut14</span><span class="p" data-group-id="8626479935-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8626479935-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut14</span><span class="p" data-group-id="8626479935-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nc">tut14</span><span class="p">:</span><span class="nf">say_something</span><span class="p" data-group-id="8626479935-3">(</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="8626479935-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │  </span><span class="ss">done</span></code></pre><p>As shown, the function <code class="inline">say_something</code> writes its first argument the number of
│ │ │  times specified by the second argument. The function <code class="inline">start</code> starts two Erlang
│ │ │  processes, one that writes &quot;hello&quot; three times and one that writes &quot;goodbye&quot;
│ │ │  three times. Both processes use the function <code class="inline">say_something</code>. Notice that a
│ │ │  function used in this way by <code class="inline">spawn</code>, to start a process, must be exported from
│ │ │ -the module (that is, in the <code class="inline">-export</code> at the start of the module).</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">9&gt; </span><span class="nc">tut14</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8051993977-1">(</span><span class="p" data-group-id="8051993977-1">)</span><span class="p">.</span><span class="w">
│ │ │ +the module (that is, in the <code class="inline">-export</code> at the start of the module).</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">9&gt; </span><span class="nc">tut14</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="0718271530-1">(</span><span class="p" data-group-id="0718271530-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │  </span><span class="ss">goodbye</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.63</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │  </span><span class="ss">goodbye</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │  </span><span class="ss">goodbye</span></code></pre><p>Notice that it did not write &quot;hello&quot; three times and then &quot;goodbye&quot; three times.
│ │ │  Instead, the first process wrote a &quot;hello&quot;, the second a &quot;goodbye&quot;, the first
│ │ │  another &quot;hello&quot; and so forth. But where did the <code class="inline">&lt;0.63.0&gt;</code> come from? The return
│ │ │  value of a function is the return value of the last &quot;thing&quot; in the function. The
│ │ │ -last thing in the function <code class="inline">start</code> is</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="2976447738-1">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2976447738-2">[</span><span class="ss">goodbye</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="2976447738-2">]</span><span class="p" data-group-id="2976447738-1">)</span><span class="p">.</span></code></pre><p><code class="inline">spawn</code> returns a <em>process identifier</em>, or <em>pid</em>, which uniquely identifies the
│ │ │ +last thing in the function <code class="inline">start</code> is</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="1978626183-1">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1978626183-2">[</span><span class="ss">goodbye</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="1978626183-2">]</span><span class="p" data-group-id="1978626183-1">)</span><span class="p">.</span></code></pre><p><code class="inline">spawn</code> returns a <em>process identifier</em>, or <em>pid</em>, which uniquely identifies the
│ │ │  process. So <code class="inline">&lt;0.63.0&gt;</code> is the pid of the <code class="inline">spawn</code> function call above. The next
│ │ │  example shows how to use pids.</p><p>Notice also that ~p is used instead of ~w in <a href="../../lib/stdlib-8.0/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a>. To quote <a href="../../lib/stdlib-8.0/doc/html/io.html#tilde_p">the manual</a>:</p><blockquote><p>~p Writes the data with standard syntax in the same way as ~w, but breaks terms
│ │ │  whose printed representation is longer than one line into many lines and indents
│ │ │  each line sensibly. It also tries to detect flat lists of printable characters and
│ │ │  to output these as strings</p></blockquote><h2 id="message-passing" class="section-heading">
│ │ │    <a href="#message-passing" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Message Passing</span>
│ │ │  </h2>
│ │ │  <p>In the following example two processes are created and they send messages to
│ │ │ -each other a number of times.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7345809130-1">(</span><span class="ss">tut15</span><span class="p" data-group-id="7345809130-1">)</span><span class="p">.</span><span class="w">
│ │ │ +each other a number of times.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9218373487-1">(</span><span class="ss">tut15</span><span class="p" data-group-id="9218373487-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7345809130-2">(</span><span class="p" data-group-id="7345809130-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7345809130-3">]</span><span class="p" data-group-id="7345809130-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9218373487-2">(</span><span class="p" data-group-id="9218373487-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9218373487-3">]</span><span class="p" data-group-id="9218373487-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="7345809130-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="7345809130-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="9218373487-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="9218373487-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7345809130-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7345809130-6">[</span><span class="p" data-group-id="7345809130-6">]</span><span class="p" data-group-id="7345809130-5">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9218373487-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9218373487-6">[</span><span class="p" data-group-id="9218373487-6">]</span><span class="p" data-group-id="9218373487-5">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="7345809130-7">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="7345809130-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7345809130-8">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7345809130-9">(</span><span class="p" data-group-id="7345809130-9">)</span><span class="p" data-group-id="7345809130-8">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="9218373487-7">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="9218373487-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9218373487-8">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9218373487-9">(</span><span class="p" data-group-id="9218373487-9">)</span><span class="p" data-group-id="9218373487-8">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7345809130-10">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7345809130-11">[</span><span class="p" data-group-id="7345809130-11">]</span><span class="p" data-group-id="7345809130-10">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9218373487-10">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9218373487-11">[</span><span class="p" data-group-id="9218373487-11">]</span><span class="p" data-group-id="9218373487-10">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="7345809130-12">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="7345809130-12">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="9218373487-12">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="9218373487-12">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="7345809130-13">(</span><span class="p" data-group-id="7345809130-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="9218373487-13">(</span><span class="p" data-group-id="9218373487-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7345809130-14">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7345809130-15">[</span><span class="p" data-group-id="7345809130-15">]</span><span class="p" data-group-id="7345809130-14">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="7345809130-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="7345809130-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7345809130-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7345809130-18">[</span><span class="p" data-group-id="7345809130-18">]</span><span class="p" data-group-id="7345809130-17">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9218373487-14">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9218373487-15">[</span><span class="p" data-group-id="9218373487-15">]</span><span class="p" data-group-id="9218373487-14">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9218373487-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="9218373487-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9218373487-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9218373487-18">[</span><span class="p" data-group-id="9218373487-18">]</span><span class="p" data-group-id="9218373487-17">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="7345809130-19">(</span><span class="p" data-group-id="7345809130-19">)</span><span class="w">
│ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="9218373487-19">(</span><span class="p" data-group-id="9218373487-19">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="7345809130-20">(</span><span class="p" data-group-id="7345809130-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="7345809130-21">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7345809130-22">[</span><span class="p" data-group-id="7345809130-22">]</span><span class="p" data-group-id="7345809130-21">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="7345809130-23">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7345809130-24">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="7345809130-24">]</span><span class="p" data-group-id="7345809130-23">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="8766440155-1">(</span><span class="ss">tut15</span><span class="p" data-group-id="8766440155-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8766440155-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut15</span><span class="p" data-group-id="8766440155-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">tut15</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8766440155-3">(</span><span class="p" data-group-id="8766440155-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="9218373487-20">(</span><span class="p" data-group-id="9218373487-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="9218373487-21">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9218373487-22">[</span><span class="p" data-group-id="9218373487-22">]</span><span class="p" data-group-id="9218373487-21">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="9218373487-23">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9218373487-24">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="9218373487-24">]</span><span class="p" data-group-id="9218373487-23">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="8438582897-1">(</span><span class="ss">tut15</span><span class="p" data-group-id="8438582897-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8438582897-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut15</span><span class="p" data-group-id="8438582897-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">tut15</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8438582897-3">(</span><span class="p" data-group-id="8438582897-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.36</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="ss">ping</span><span class="w"> </span><span class="ss">finished</span><span class="w">
│ │ │ -</span><span class="n">Pong</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>The function <code class="inline">start</code> first creates a process, let us call it &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pong_PID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="8410614273-1">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8410614273-2">[</span><span class="p" data-group-id="8410614273-2">]</span><span class="p" data-group-id="8410614273-1">)</span></code></pre><p>This process executes <code class="inline">tut15:pong()</code>. <code class="inline">Pong_PID</code> is the process identity of the
│ │ │ -&quot;pong&quot; process. The function <code class="inline">start</code> now creates another process &quot;ping&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="7557144660-1">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7557144660-2">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="7557144660-2">]</span><span class="p" data-group-id="7557144660-1">)</span><span class="p">,</span></code></pre><p>This process executes:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut15</span><span class="p">:</span><span class="nf">ping</span><span class="p" data-group-id="3340177129-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="3340177129-1">)</span></code></pre><p><code class="inline">&lt;0.36.0&gt;</code> is the return value from the <code class="inline">start</code> function.</p><p>The process &quot;pong&quot; now does:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ +</span><span class="n">Pong</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>The function <code class="inline">start</code> first creates a process, let us call it &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pong_PID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="7465194617-1">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7465194617-2">[</span><span class="p" data-group-id="7465194617-2">]</span><span class="p" data-group-id="7465194617-1">)</span></code></pre><p>This process executes <code class="inline">tut15:pong()</code>. <code class="inline">Pong_PID</code> is the process identity of the
│ │ │ +&quot;pong&quot; process. The function <code class="inline">start</code> now creates another process &quot;ping&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="5176101441-1">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5176101441-2">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="5176101441-2">]</span><span class="p" data-group-id="5176101441-1">)</span><span class="p">,</span></code></pre><p>This process executes:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut15</span><span class="p">:</span><span class="nf">ping</span><span class="p" data-group-id="0676874986-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="0676874986-1">)</span></code></pre><p><code class="inline">&lt;0.36.0&gt;</code> is the return value from the <code class="inline">start</code> function.</p><p>The process &quot;pong&quot; now does:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │      </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5639043586-1">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5639043586-2">[</span><span class="p" data-group-id="5639043586-2">]</span><span class="p" data-group-id="5639043586-1">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5639043586-3">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="5639043586-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5639043586-4">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5639043586-5">[</span><span class="p" data-group-id="5639043586-5">]</span><span class="p" data-group-id="5639043586-4">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4526460381-1">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4526460381-2">[</span><span class="p" data-group-id="4526460381-2">]</span><span class="p" data-group-id="4526460381-1">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4526460381-3">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="4526460381-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4526460381-4">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4526460381-5">[</span><span class="p" data-group-id="4526460381-5">]</span><span class="p" data-group-id="4526460381-4">)</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="nf">pong</span><span class="p" data-group-id="5639043586-6">(</span><span class="p" data-group-id="5639043586-6">)</span><span class="w">
│ │ │ +        </span><span class="nf">pong</span><span class="p" data-group-id="4526460381-6">(</span><span class="p" data-group-id="4526460381-6">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">receive</code> construct is used to allow processes to wait for messages from
│ │ │  other processes. It has the following format:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │     </span><span class="ss">pattern1</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │         </span><span class="ss">actions1</span><span class="p">;</span><span class="w">
│ │ │     </span><span class="ss">pattern2</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │         </span><span class="ss">actions2</span><span class="p">;</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ @@ -253,84 +253,84 @@
│ │ │  queue (keeping the first message and any other messages in the queue). If the
│ │ │  second message does not match, the third message is tried, and so on, until the
│ │ │  end of the queue is reached. If the end of the queue is reached, the process
│ │ │  blocks (stops execution) and waits until a new message is received and this
│ │ │  procedure is repeated.</p><p>The Erlang implementation is &quot;clever&quot; and minimizes the number of times each
│ │ │  message is tested against the patterns in each <code class="inline">receive</code>.</p><p>Now back to the ping pong example.</p><p>&quot;Pong&quot; is waiting for messages. If the atom <code class="inline">finished</code> is received, &quot;pong&quot;
│ │ │  writes &quot;Pong finished&quot; to the output and, as it has nothing more to do,
│ │ │ -terminates. If it receives a message with the format:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5268599946-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="5268599946-1">}</span></code></pre><p>it writes &quot;Pong received ping&quot; to the output and sends the atom <code class="inline">pong</code> to the
│ │ │ +terminates. If it receives a message with the format:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2682528251-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="2682528251-1">}</span></code></pre><p>it writes &quot;Pong received ping&quot; to the output and sends the atom <code class="inline">pong</code> to the
│ │ │  process &quot;ping&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span></code></pre><p>Notice how the operator <code class="inline">!</code> is used to send messages. The syntax of <code class="inline">!</code> is:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Message</span></code></pre><p>That is, <code class="inline">Message</code> (any Erlang term) is sent to the process with identity <code class="inline">Pid</code>.</p><p>After sending the message <code class="inline">pong</code> to the process &quot;ping&quot;, &quot;pong&quot; calls the <code class="inline">pong</code>
│ │ │  function again, which causes it to get back to the <code class="inline">receive</code> again and wait for
│ │ │ -another message.</p><p>Now let us look at the process &quot;ping&quot;. Recall that it was started by executing:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut15</span><span class="p">:</span><span class="nf">ping</span><span class="p" data-group-id="0769991890-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="0769991890-1">)</span></code></pre><p>Looking at the function <code class="inline">ping/2</code>, the second clause of <code class="inline">ping/2</code> is executed
│ │ │ +another message.</p><p>Now let us look at the process &quot;ping&quot;. Recall that it was started by executing:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut15</span><span class="p">:</span><span class="nf">ping</span><span class="p" data-group-id="7261671604-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="7261671604-1">)</span></code></pre><p>Looking at the function <code class="inline">ping/2</code>, the second clause of <code class="inline">ping/2</code> is executed
│ │ │  since the value of the first argument is 3 (not 0) (first clause head is
│ │ │ -<code class="inline">ping(0,Pong_PID)</code>, second clause head is <code class="inline">ping(N,Pong_PID)</code>, so <code class="inline">N</code> becomes 3).</p><p>The second clause sends a message to &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7424356504-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7424356504-2">(</span><span class="p" data-group-id="7424356504-2">)</span><span class="p" data-group-id="7424356504-1">}</span><span class="p">,</span></code></pre><p><a href="../../erts-17.0/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a> returns the pid of the process that executes <a href="../../erts-17.0/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a>, in this case the
│ │ │ +<code class="inline">ping(0,Pong_PID)</code>, second clause head is <code class="inline">ping(N,Pong_PID)</code>, so <code class="inline">N</code> becomes 3).</p><p>The second clause sends a message to &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2424392730-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2424392730-2">(</span><span class="p" data-group-id="2424392730-2">)</span><span class="p" data-group-id="2424392730-1">}</span><span class="p">,</span></code></pre><p><a href="../../erts-17.0/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a> returns the pid of the process that executes <a href="../../erts-17.0/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a>, in this case the
│ │ │  pid of &quot;ping&quot;. (Recall the code for &quot;pong&quot;, this ends up in the variable
│ │ │  <code class="inline">Ping_PID</code> in the <code class="inline">receive</code> previously explained.)</p><p>&quot;Ping&quot; now waits for a reply from &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │      </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0724946362-1">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0724946362-2">[</span><span class="p" data-group-id="0724946362-2">]</span><span class="p" data-group-id="0724946362-1">)</span><span class="w">
│ │ │ +        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5408333425-1">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5408333425-2">[</span><span class="p" data-group-id="5408333425-2">]</span><span class="p" data-group-id="5408333425-1">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">,</span></code></pre><p>It writes &quot;Ping received pong&quot; when this reply arrives, after which &quot;ping&quot; calls
│ │ │ -the <code class="inline">ping</code> function again.</p><pre><code class="makeup erlang" translate="no"><span class="nf">ping</span><span class="p" data-group-id="3043721242-1">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="3043721242-1">)</span></code></pre><p><code class="inline">N-1</code> causes the first argument to be decremented until it becomes 0. When this
│ │ │ -occurs, the first clause of <code class="inline">ping/2</code> is executed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">ping</span><span class="p" data-group-id="3633547549-1">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="3633547549-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +the <code class="inline">ping</code> function again.</p><pre><code class="makeup erlang" translate="no"><span class="nf">ping</span><span class="p" data-group-id="2410107403-1">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="2410107403-1">)</span></code></pre><p><code class="inline">N-1</code> causes the first argument to be decremented until it becomes 0. When this
│ │ │ +occurs, the first clause of <code class="inline">ping/2</code> is executed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">ping</span><span class="p" data-group-id="1253794794-1">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="1253794794-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w">  </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3633547549-2">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3633547549-3">[</span><span class="p" data-group-id="3633547549-3">]</span><span class="p" data-group-id="3633547549-2">)</span><span class="p">;</span></code></pre><p>The atom <code class="inline">finished</code> is sent to &quot;pong&quot; (causing it to terminate as described
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1253794794-2">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1253794794-3">[</span><span class="p" data-group-id="1253794794-3">]</span><span class="p" data-group-id="1253794794-2">)</span><span class="p">;</span></code></pre><p>The atom <code class="inline">finished</code> is sent to &quot;pong&quot; (causing it to terminate as described
│ │ │  above) and &quot;ping finished&quot; is written to the output. &quot;Ping&quot; then terminates as
│ │ │  it has nothing left to do.</p><h2 id="registered-process-names" class="section-heading">
│ │ │    <a href="#registered-process-names" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Registered Process Names</span>
│ │ │  </h2>
│ │ │  <p>In the above example, &quot;pong&quot; was first created to be able to give the identity
│ │ │  of &quot;pong&quot; when &quot;ping&quot; was started. That is, in some way &quot;ping&quot; must be able to
│ │ │  know the identity of &quot;pong&quot; to be able to send a message to it. Sometimes
│ │ │  processes which need to know each other's identities are started independently
│ │ │  of each other. Erlang thus provides a mechanism for processes to be given names
│ │ │  so that these names can be used as identities instead of pids. This is done by
│ │ │ -using the <code class="inline">register</code> BIF:</p><pre><code class="makeup erlang" translate="no"><span class="nf">register</span><span class="p" data-group-id="8295032977-1">(</span><span class="ss">some_atom</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="8295032977-1">)</span></code></pre><p>Let us now rewrite the ping pong example using this and give the name <code class="inline">pong</code> to
│ │ │ -the &quot;pong&quot; process:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7776118344-1">(</span><span class="ss">tut16</span><span class="p" data-group-id="7776118344-1">)</span><span class="p">.</span><span class="w">
│ │ │ +using the <code class="inline">register</code> BIF:</p><pre><code class="makeup erlang" translate="no"><span class="nf">register</span><span class="p" data-group-id="7662946490-1">(</span><span class="ss">some_atom</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="7662946490-1">)</span></code></pre><p>Let us now rewrite the ping pong example using this and give the name <code class="inline">pong</code> to
│ │ │ +the &quot;pong&quot; process:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4227419060-1">(</span><span class="ss">tut16</span><span class="p" data-group-id="4227419060-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7776118344-2">(</span><span class="p" data-group-id="7776118344-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7776118344-3">]</span><span class="p" data-group-id="7776118344-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4227419060-2">(</span><span class="p" data-group-id="4227419060-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4227419060-3">]</span><span class="p" data-group-id="4227419060-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="7776118344-4">(</span><span class="mi">0</span><span class="p" data-group-id="7776118344-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="4227419060-4">(</span><span class="mi">0</span><span class="p" data-group-id="4227419060-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7776118344-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7776118344-6">[</span><span class="p" data-group-id="7776118344-6">]</span><span class="p" data-group-id="7776118344-5">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4227419060-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4227419060-6">[</span><span class="p" data-group-id="4227419060-6">]</span><span class="p" data-group-id="4227419060-5">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="7776118344-7">(</span><span class="n">N</span><span class="p" data-group-id="7776118344-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7776118344-8">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7776118344-9">(</span><span class="p" data-group-id="7776118344-9">)</span><span class="p" data-group-id="7776118344-8">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="4227419060-7">(</span><span class="n">N</span><span class="p" data-group-id="4227419060-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4227419060-8">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4227419060-9">(</span><span class="p" data-group-id="4227419060-9">)</span><span class="p" data-group-id="4227419060-8">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7776118344-10">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7776118344-11">[</span><span class="p" data-group-id="7776118344-11">]</span><span class="p" data-group-id="7776118344-10">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4227419060-10">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4227419060-11">[</span><span class="p" data-group-id="4227419060-11">]</span><span class="p" data-group-id="4227419060-10">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="7776118344-12">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="7776118344-12">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="4227419060-12">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="4227419060-12">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="7776118344-13">(</span><span class="p" data-group-id="7776118344-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="4227419060-13">(</span><span class="p" data-group-id="4227419060-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7776118344-14">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7776118344-15">[</span><span class="p" data-group-id="7776118344-15">]</span><span class="p" data-group-id="7776118344-14">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="7776118344-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="7776118344-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7776118344-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7776118344-18">[</span><span class="p" data-group-id="7776118344-18">]</span><span class="p" data-group-id="7776118344-17">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4227419060-14">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4227419060-15">[</span><span class="p" data-group-id="4227419060-15">]</span><span class="p" data-group-id="4227419060-14">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="4227419060-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="4227419060-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4227419060-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4227419060-18">[</span><span class="p" data-group-id="4227419060-18">]</span><span class="p" data-group-id="4227419060-17">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="7776118344-19">(</span><span class="p" data-group-id="7776118344-19">)</span><span class="w">
│ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="4227419060-19">(</span><span class="p" data-group-id="4227419060-19">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="7776118344-20">(</span><span class="p" data-group-id="7776118344-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="7776118344-21">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="7776118344-22">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7776118344-23">[</span><span class="p" data-group-id="7776118344-23">]</span><span class="p" data-group-id="7776118344-22">)</span><span class="p" data-group-id="7776118344-21">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="7776118344-24">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7776118344-25">[</span><span class="mi">3</span><span class="p" data-group-id="7776118344-25">]</span><span class="p" data-group-id="7776118344-24">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nf">c</span><span class="p" data-group-id="5972313931-1">(</span><span class="ss">tut16</span><span class="p" data-group-id="5972313931-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5972313931-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut16</span><span class="p" data-group-id="5972313931-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">tut16</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="5972313931-3">(</span><span class="p" data-group-id="5972313931-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="4227419060-20">(</span><span class="p" data-group-id="4227419060-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="4227419060-21">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="4227419060-22">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4227419060-23">[</span><span class="p" data-group-id="4227419060-23">]</span><span class="p" data-group-id="4227419060-22">)</span><span class="p" data-group-id="4227419060-21">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="4227419060-24">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4227419060-25">[</span><span class="mi">3</span><span class="p" data-group-id="4227419060-25">]</span><span class="p" data-group-id="4227419060-24">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nf">c</span><span class="p" data-group-id="9148740519-1">(</span><span class="ss">tut16</span><span class="p" data-group-id="9148740519-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9148740519-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut16</span><span class="p" data-group-id="9148740519-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">tut16</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="9148740519-3">(</span><span class="p" data-group-id="9148740519-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.38</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="ss">ping</span><span class="w"> </span><span class="ss">finished</span><span class="w">
│ │ │ -</span><span class="n">Pong</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>Here the <code class="inline">start/0</code> function,</p><pre><code class="makeup erlang" translate="no"><span class="nf">register</span><span class="p" data-group-id="1860562214-1">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="1860562214-2">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1860562214-3">[</span><span class="p" data-group-id="1860562214-3">]</span><span class="p" data-group-id="1860562214-2">)</span><span class="p" data-group-id="1860562214-1">)</span><span class="p">,</span></code></pre><p>both spawns the &quot;pong&quot; process and gives it the name <code class="inline">pong</code>. In the &quot;ping&quot;
│ │ │ -process, messages can be sent to <code class="inline">pong</code> by:</p><pre><code class="makeup erlang" translate="no"><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3455281146-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3455281146-2">(</span><span class="p" data-group-id="3455281146-2">)</span><span class="p" data-group-id="3455281146-1">}</span><span class="p">,</span></code></pre><p><code class="inline">ping/2</code> now becomes <code class="inline">ping/1</code> as the argument <code class="inline">Pong_PID</code> is not needed.</p><h2 id="distributed-programming" class="section-heading">
│ │ │ +</span><span class="n">Pong</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>Here the <code class="inline">start/0</code> function,</p><pre><code class="makeup erlang" translate="no"><span class="nf">register</span><span class="p" data-group-id="5112983907-1">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="5112983907-2">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5112983907-3">[</span><span class="p" data-group-id="5112983907-3">]</span><span class="p" data-group-id="5112983907-2">)</span><span class="p" data-group-id="5112983907-1">)</span><span class="p">,</span></code></pre><p>both spawns the &quot;pong&quot; process and gives it the name <code class="inline">pong</code>. In the &quot;ping&quot;
│ │ │ +process, messages can be sent to <code class="inline">pong</code> by:</p><pre><code class="makeup erlang" translate="no"><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3587438488-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3587438488-2">(</span><span class="p" data-group-id="3587438488-2">)</span><span class="p" data-group-id="3587438488-1">}</span><span class="p">,</span></code></pre><p><code class="inline">ping/2</code> now becomes <code class="inline">ping/1</code> as the argument <code class="inline">Pong_PID</code> is not needed.</p><h2 id="distributed-programming" class="section-heading">
│ │ │    <a href="#distributed-programming" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Distributed Programming</span>
│ │ │  </h2>
│ │ │  <p>Let us rewrite the ping pong program with &quot;ping&quot; and &quot;pong&quot; on different
│ │ │  computers. First a few things need to be set up to get this to work. The
│ │ │ @@ -350,106 +350,106 @@
│ │ │  of the file. This is a requirement.</p><p>When you start an Erlang system that is going to talk to other Erlang systems,
│ │ │  you must give it a name, for example:</p><pre><code class="text">$ erl -sname my_name</code></pre><p>We will see more details of this later. If you want to experiment with
│ │ │  distributed Erlang, but you only have one computer to work on, you can start two
│ │ │  separate Erlang systems on the same computer but give them different names. Each
│ │ │  Erlang system running on a computer is called an <em>Erlang node</em>.</p><p>(Note: <code class="inline">erl -sname</code> assumes that all nodes are in the same IP domain and we can
│ │ │  use only the first component of the IP address, if we want to use nodes in
│ │ │  different domains we use <code class="inline">-name</code> instead, but then all IP addresses must be given
│ │ │ -in full.)</p><p>Here is the ping pong example modified to run on two separate nodes:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5549743915-1">(</span><span class="ss">tut17</span><span class="p" data-group-id="5549743915-1">)</span><span class="p">.</span><span class="w">
│ │ │ +in full.)</p><p>Here is the ping pong example modified to run on two separate nodes:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7921432818-1">(</span><span class="ss">tut17</span><span class="p" data-group-id="7921432818-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5549743915-2">(</span><span class="p" data-group-id="5549743915-3">[</span><span class="ss">start_ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">start_pong</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5549743915-3">]</span><span class="p" data-group-id="5549743915-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7921432818-2">(</span><span class="p" data-group-id="7921432818-3">[</span><span class="ss">start_ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">start_pong</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7921432818-3">]</span><span class="p" data-group-id="7921432818-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="5549743915-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="5549743915-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5549743915-5">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="5549743915-5">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5549743915-6">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5549743915-7">[</span><span class="p" data-group-id="5549743915-7">]</span><span class="p" data-group-id="5549743915-6">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="7921432818-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="7921432818-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7921432818-5">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="7921432818-5">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7921432818-6">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7921432818-7">[</span><span class="p" data-group-id="7921432818-7">]</span><span class="p" data-group-id="7921432818-6">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="5549743915-8">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="5549743915-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5549743915-9">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="5549743915-9">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5549743915-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5549743915-11">(</span><span class="p" data-group-id="5549743915-11">)</span><span class="p" data-group-id="5549743915-10">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="7921432818-8">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="7921432818-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7921432818-9">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="7921432818-9">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7921432818-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7921432818-11">(</span><span class="p" data-group-id="7921432818-11">)</span><span class="p" data-group-id="7921432818-10">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5549743915-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5549743915-13">[</span><span class="p" data-group-id="5549743915-13">]</span><span class="p" data-group-id="5549743915-12">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7921432818-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7921432818-13">[</span><span class="p" data-group-id="7921432818-13">]</span><span class="p" data-group-id="7921432818-12">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="5549743915-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="5549743915-14">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="7921432818-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="7921432818-14">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="5549743915-15">(</span><span class="p" data-group-id="5549743915-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="7921432818-15">(</span><span class="p" data-group-id="7921432818-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5549743915-16">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5549743915-17">[</span><span class="p" data-group-id="5549743915-17">]</span><span class="p" data-group-id="5549743915-16">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5549743915-18">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="5549743915-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5549743915-19">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5549743915-20">[</span><span class="p" data-group-id="5549743915-20">]</span><span class="p" data-group-id="5549743915-19">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7921432818-16">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7921432818-17">[</span><span class="p" data-group-id="7921432818-17">]</span><span class="p" data-group-id="7921432818-16">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7921432818-18">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="7921432818-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7921432818-19">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7921432818-20">[</span><span class="p" data-group-id="7921432818-20">]</span><span class="p" data-group-id="7921432818-19">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="5549743915-21">(</span><span class="p" data-group-id="5549743915-21">)</span><span class="w">
│ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="7921432818-21">(</span><span class="p" data-group-id="7921432818-21">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_pong</span><span class="p" data-group-id="5549743915-22">(</span><span class="p" data-group-id="5549743915-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="5549743915-23">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="5549743915-24">(</span><span class="ss">tut17</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5549743915-25">[</span><span class="p" data-group-id="5549743915-25">]</span><span class="p" data-group-id="5549743915-24">)</span><span class="p" data-group-id="5549743915-23">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_pong</span><span class="p" data-group-id="7921432818-22">(</span><span class="p" data-group-id="7921432818-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="7921432818-23">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="7921432818-24">(</span><span class="ss">tut17</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7921432818-25">[</span><span class="p" data-group-id="7921432818-25">]</span><span class="p" data-group-id="7921432818-24">)</span><span class="p" data-group-id="7921432818-23">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_ping</span><span class="p" data-group-id="5549743915-26">(</span><span class="n">Pong_Node</span><span class="p" data-group-id="5549743915-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="5549743915-27">(</span><span class="ss">tut17</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5549743915-28">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="5549743915-28">]</span><span class="p" data-group-id="5549743915-27">)</span><span class="p">.</span></code></pre><p>Let us assume there are two computers called gollum and kosken. First a node is
│ │ │ +</span><span class="nf">start_ping</span><span class="p" data-group-id="7921432818-26">(</span><span class="n">Pong_Node</span><span class="p" data-group-id="7921432818-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="7921432818-27">(</span><span class="ss">tut17</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7921432818-28">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="7921432818-28">]</span><span class="p" data-group-id="7921432818-27">)</span><span class="p">.</span></code></pre><p>Let us assume there are two computers called gollum and kosken. First a node is
│ │ │  started on kosken, called ping, and then a node on gollum, called pong.</p><p>On kosken (on a Linux/UNIX system):</p><pre><code class="text">kosken$ erl -sname ping
│ │ │  Erlang/OTP 28 [erts-16.3] [source] [64-bit] [smp:16:16] [ds:16:16:10] [async-threads:1] [jit:ns]
│ │ │  
│ │ │  Eshell V16.3 (press Ctrl+G to abort, type help(). for help)
│ │ │  (ping@kosken)1&gt;</code></pre><p>On gollum:</p><pre><code class="text">gollum$ erl -sname pong
│ │ │  Erlang/OTP 28 [erts-16.3] [source] [64-bit] [smp:16:16] [ds:16:16:10] [async-threads:1] [jit:ns]
│ │ │  
│ │ │  Eshell V16.3 (press Ctrl+G to abort, type help(). for help)
│ │ │ -(pong@gollum)1&gt;</code></pre><p>Now the &quot;pong&quot; process on gollum is started:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)1&gt; </span><span class="nc">tut17</span><span class="p">:</span><span class="nf">start_pong</span><span class="p" data-group-id="8045168870-1">(</span><span class="p" data-group-id="8045168870-1">)</span><span class="p">.</span><span class="w">
│ │ │ +(pong@gollum)1&gt;</code></pre><p>Now the &quot;pong&quot; process on gollum is started:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)1&gt; </span><span class="nc">tut17</span><span class="p">:</span><span class="nf">start_pong</span><span class="p" data-group-id="8375448136-1">(</span><span class="p" data-group-id="8375448136-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span></code></pre><p>And the &quot;ping&quot; process on kosken is started (from the code above you can see
│ │ │  that a parameter of the <code class="inline">start_ping</code> function is the node name of the Erlang
│ │ │ -system where &quot;pong&quot; is running):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(ping@kosken)1&gt; </span><span class="nc">tut17</span><span class="p">:</span><span class="nf">start_ping</span><span class="p" data-group-id="9514521309-1">(</span><span class="ss">pong@gollum</span><span class="p" data-group-id="9514521309-1">)</span><span class="p">.</span><span class="w">
│ │ │ +system where &quot;pong&quot; is running):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(ping@kosken)1&gt; </span><span class="nc">tut17</span><span class="p">:</span><span class="nf">start_ping</span><span class="p" data-group-id="2120042090-1">(</span><span class="ss">pong@gollum</span><span class="p" data-group-id="2120042090-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.37</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="ss">ping</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>As shown, the ping pong program has run. On the &quot;pong&quot; side:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)2&gt; </span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="nf">finished</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4923169401-1">(</span><span class="ss">pong@gollum</span><span class="p" data-group-id="4923169401-1">)</span><span class="mi">2</span><span class="o">&gt;</span><span class="w"> </span></code></pre><p>Looking at the <code class="inline">tut17</code> code, you see that the <code class="inline">pong</code> function itself is
│ │ │ +</span><span class="p" data-group-id="3691780112-1">(</span><span class="ss">pong@gollum</span><span class="p" data-group-id="3691780112-1">)</span><span class="mi">2</span><span class="o">&gt;</span><span class="w"> </span></code></pre><p>Looking at the <code class="inline">tut17</code> code, you see that the <code class="inline">pong</code> function itself is
│ │ │  unchanged, the following lines work in the same way irrespective of on which
│ │ │ -node the &quot;ping&quot; process is executed:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5819985701-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="5819985701-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5819985701-2">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5819985701-3">[</span><span class="p" data-group-id="5819985701-3">]</span><span class="p" data-group-id="5819985701-2">)</span><span class="p">,</span><span class="w">
│ │ │ +node the &quot;ping&quot; process is executed:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0931612739-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="0931612739-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0931612739-2">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0931612739-3">[</span><span class="p" data-group-id="0931612739-3">]</span><span class="p" data-group-id="0931612739-2">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span></code></pre><p>Thus, Erlang pids contain information about where the process executes. So if
│ │ │  you know the pid of a process, the <code class="inline">!</code> operator can be used to send it a
│ │ │ -message disregarding if the process is on the same node or on a different node.</p><p>A difference is how messages are sent to a registered process on another node:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1143475220-1">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="1143475220-1">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1143475220-2">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1143475220-3">(</span><span class="p" data-group-id="1143475220-3">)</span><span class="p" data-group-id="1143475220-2">}</span><span class="p">,</span></code></pre><p>A tuple <code class="inline">{registered_name,node_name}</code> is used instead of just the
│ │ │ +message disregarding if the process is on the same node or on a different node.</p><p>A difference is how messages are sent to a registered process on another node:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4627512787-1">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="4627512787-1">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4627512787-2">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4627512787-3">(</span><span class="p" data-group-id="4627512787-3">)</span><span class="p" data-group-id="4627512787-2">}</span><span class="p">,</span></code></pre><p>A tuple <code class="inline">{registered_name,node_name}</code> is used instead of just the
│ │ │  <code class="inline">registered_name</code>.</p><p>In the previous example, &quot;ping&quot; and &quot;pong&quot; were started from the shells of two
│ │ │  separate Erlang nodes. <code class="inline">spawn</code> can also be used to start processes in other
│ │ │  nodes.</p><p>The next example is the ping pong program, yet again, but this time &quot;ping&quot; is
│ │ │ -started in another node:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2201740200-1">(</span><span class="ss">tut18</span><span class="p" data-group-id="2201740200-1">)</span><span class="p">.</span><span class="w">
│ │ │ +started in another node:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7952222805-1">(</span><span class="ss">tut18</span><span class="p" data-group-id="7952222805-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2201740200-2">(</span><span class="p" data-group-id="2201740200-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2201740200-3">]</span><span class="p" data-group-id="2201740200-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7952222805-2">(</span><span class="p" data-group-id="7952222805-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7952222805-3">]</span><span class="p" data-group-id="7952222805-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="2201740200-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2201740200-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2201740200-5">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2201740200-5">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2201740200-6">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2201740200-7">[</span><span class="p" data-group-id="2201740200-7">]</span><span class="p" data-group-id="2201740200-6">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="7952222805-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="7952222805-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7952222805-5">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="7952222805-5">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7952222805-6">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7952222805-7">[</span><span class="p" data-group-id="7952222805-7">]</span><span class="p" data-group-id="7952222805-6">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="2201740200-8">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2201740200-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2201740200-9">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2201740200-9">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2201740200-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2201740200-11">(</span><span class="p" data-group-id="2201740200-11">)</span><span class="p" data-group-id="2201740200-10">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="7952222805-8">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="7952222805-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7952222805-9">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="7952222805-9">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7952222805-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7952222805-11">(</span><span class="p" data-group-id="7952222805-11">)</span><span class="p" data-group-id="7952222805-10">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2201740200-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2201740200-13">[</span><span class="p" data-group-id="2201740200-13">]</span><span class="p" data-group-id="2201740200-12">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7952222805-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7952222805-13">[</span><span class="p" data-group-id="7952222805-13">]</span><span class="p" data-group-id="7952222805-12">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="2201740200-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2201740200-14">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="7952222805-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="7952222805-14">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="2201740200-15">(</span><span class="p" data-group-id="2201740200-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="7952222805-15">(</span><span class="p" data-group-id="7952222805-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2201740200-16">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2201740200-17">[</span><span class="p" data-group-id="2201740200-17">]</span><span class="p" data-group-id="2201740200-16">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="2201740200-18">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="2201740200-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2201740200-19">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2201740200-20">[</span><span class="p" data-group-id="2201740200-20">]</span><span class="p" data-group-id="2201740200-19">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7952222805-16">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7952222805-17">[</span><span class="p" data-group-id="7952222805-17">]</span><span class="p" data-group-id="7952222805-16">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7952222805-18">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="7952222805-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7952222805-19">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7952222805-20">[</span><span class="p" data-group-id="7952222805-20">]</span><span class="p" data-group-id="7952222805-19">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="2201740200-21">(</span><span class="p" data-group-id="2201740200-21">)</span><span class="w">
│ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="7952222805-21">(</span><span class="p" data-group-id="7952222805-21">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="2201740200-22">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="2201740200-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="2201740200-23">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="2201740200-24">(</span><span class="ss">tut18</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2201740200-25">[</span><span class="p" data-group-id="2201740200-25">]</span><span class="p" data-group-id="2201740200-24">)</span><span class="p" data-group-id="2201740200-23">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="2201740200-26">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut18</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2201740200-27">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="nf">node</span><span class="p" data-group-id="2201740200-28">(</span><span class="p" data-group-id="2201740200-28">)</span><span class="p" data-group-id="2201740200-27">]</span><span class="p" data-group-id="2201740200-26">)</span><span class="p">.</span></code></pre><p>Assuming an Erlang system called ping (but not the &quot;ping&quot; process) has already
│ │ │ -been started on kosken, then on gollum this is done:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)1&gt; </span><span class="nc">tut18</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1845867212-1">(</span><span class="ss">ping@kosken</span><span class="p" data-group-id="1845867212-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="7952222805-22">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="7952222805-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="7952222805-23">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="7952222805-24">(</span><span class="ss">tut18</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7952222805-25">[</span><span class="p" data-group-id="7952222805-25">]</span><span class="p" data-group-id="7952222805-24">)</span><span class="p" data-group-id="7952222805-23">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="7952222805-26">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut18</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7952222805-27">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="nf">node</span><span class="p" data-group-id="7952222805-28">(</span><span class="p" data-group-id="7952222805-28">)</span><span class="p" data-group-id="7952222805-27">]</span><span class="p" data-group-id="7952222805-26">)</span><span class="p">.</span></code></pre><p>Assuming an Erlang system called ping (but not the &quot;ping&quot; process) has already
│ │ │ +been started on kosken, then on gollum this is done:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)1&gt; </span><span class="nc">tut18</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="4718477621-1">(</span><span class="ss">ping@kosken</span><span class="p" data-group-id="4718477621-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">3934.39</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ @@ -513,188 +513,188 @@
│ │ │  </span><span class="c1">%%% Started: messenger:client(Server_Node, Name)</span><span class="w">
│ │ │  </span><span class="c1">%%% To client: logoff</span><span class="w">
│ │ │  </span><span class="c1">%%% To client: {message_to, ToName, Message}</span><span class="w">
│ │ │  </span><span class="c1">%%%</span><span class="w">
│ │ │  </span><span class="c1">%%% Configuration: change the server_node() function to return the</span><span class="w">
│ │ │  </span><span class="c1">%%% name of the node where the messenger server runs</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5615306910-1">(</span><span class="ss">messenger</span><span class="p" data-group-id="5615306910-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5615306910-2">(</span><span class="p" data-group-id="5615306910-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5615306910-3">]</span><span class="p" data-group-id="5615306910-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9834058101-1">(</span><span class="ss">messenger</span><span class="p" data-group-id="9834058101-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9834058101-2">(</span><span class="p" data-group-id="9834058101-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9834058101-3">]</span><span class="p" data-group-id="9834058101-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Change the function below to return the name of the node where the</span><span class="w">
│ │ │  </span><span class="c1">%%% messenger server runs</span><span class="w">
│ │ │ -</span><span class="nf">server_node</span><span class="p" data-group-id="5615306910-4">(</span><span class="p" data-group-id="5615306910-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_node</span><span class="p" data-group-id="9834058101-4">(</span><span class="p" data-group-id="9834058101-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">messenger@super</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% This is the server process for the &quot;messenger&quot;</span><span class="w">
│ │ │  </span><span class="c1">%%% the user list has the format [{ClientPid1, Name1},{ClientPid2, Name2},...]</span><span class="w">
│ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="5615306910-5">(</span><span class="n">User_List</span><span class="p" data-group-id="5615306910-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="9834058101-5">(</span><span class="n">User_List</span><span class="p" data-group-id="9834058101-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5615306910-6">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5615306910-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="5615306910-7">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5615306910-7">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="5615306910-8">(</span><span class="n">New_User_List</span><span class="p" data-group-id="5615306910-8">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5615306910-9">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p" data-group-id="5615306910-9">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="5615306910-10">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5615306910-10">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="5615306910-11">(</span><span class="n">New_User_List</span><span class="p" data-group-id="5615306910-11">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5615306910-12">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5615306910-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="5615306910-13">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5615306910-13">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5615306910-14">(</span><span class="s">&quot;list is now: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5615306910-15">[</span><span class="n">User_List</span><span class="p" data-group-id="5615306910-15">]</span><span class="p" data-group-id="5615306910-14">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="5615306910-16">(</span><span class="n">User_List</span><span class="p" data-group-id="5615306910-16">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9834058101-6">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9834058101-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="9834058101-7">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9834058101-7">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="9834058101-8">(</span><span class="n">New_User_List</span><span class="p" data-group-id="9834058101-8">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9834058101-9">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p" data-group-id="9834058101-9">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="9834058101-10">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9834058101-10">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="9834058101-11">(</span><span class="n">New_User_List</span><span class="p" data-group-id="9834058101-11">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9834058101-12">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9834058101-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="9834058101-13">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9834058101-13">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9834058101-14">(</span><span class="s">&quot;list is now: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9834058101-15">[</span><span class="n">User_List</span><span class="p" data-group-id="9834058101-15">]</span><span class="p" data-group-id="9834058101-14">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="9834058101-16">(</span><span class="n">User_List</span><span class="p" data-group-id="9834058101-16">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Start the server</span><span class="w">
│ │ │ -</span><span class="nf">start_server</span><span class="p" data-group-id="5615306910-17">(</span><span class="p" data-group-id="5615306910-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="5615306910-18">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="5615306910-19">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5615306910-20">[</span><span class="p" data-group-id="5615306910-21">[</span><span class="p" data-group-id="5615306910-21">]</span><span class="p" data-group-id="5615306910-20">]</span><span class="p" data-group-id="5615306910-19">)</span><span class="p" data-group-id="5615306910-18">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_server</span><span class="p" data-group-id="9834058101-17">(</span><span class="p" data-group-id="9834058101-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="9834058101-18">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="9834058101-19">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9834058101-20">[</span><span class="p" data-group-id="9834058101-21">[</span><span class="p" data-group-id="9834058101-21">]</span><span class="p" data-group-id="9834058101-20">]</span><span class="p" data-group-id="9834058101-19">)</span><span class="p" data-group-id="9834058101-18">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  
│ │ │  </span><span class="c1">%%% Server adds a new user to the user list</span><span class="w">
│ │ │ -</span><span class="nf">server_logon</span><span class="p" data-group-id="5615306910-22">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5615306910-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_logon</span><span class="p" data-group-id="9834058101-22">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9834058101-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% check if logged on anywhere else</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="5615306910-23">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5615306910-23">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="9834058101-23">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9834058101-23">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5615306910-24">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="5615306910-24">}</span><span class="p">,</span><span class="w">  </span><span class="c1">%reject logon</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9834058101-24">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="9834058101-24">}</span><span class="p">,</span><span class="w">  </span><span class="c1">%reject logon</span><span class="w">
│ │ │              </span><span class="n">User_List</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5615306910-25">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">logged_on</span><span class="p" data-group-id="5615306910-25">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="5615306910-26">[</span><span class="p" data-group-id="5615306910-27">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5615306910-27">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5615306910-26">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9834058101-25">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">logged_on</span><span class="p" data-group-id="9834058101-25">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="9834058101-26">[</span><span class="p" data-group-id="9834058101-27">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9834058101-27">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9834058101-26">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Server deletes a user from the user list</span><span class="w">
│ │ │ -</span><span class="nf">server_logoff</span><span class="p" data-group-id="5615306910-28">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5615306910-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="5615306910-29">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5615306910-29">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">server_logoff</span><span class="p" data-group-id="9834058101-28">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9834058101-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="9834058101-29">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9834058101-29">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  
│ │ │  </span><span class="c1">%%% Server transfers a message between users</span><span class="w">
│ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="5615306910-30">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5615306910-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="9834058101-30">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9834058101-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% check that the user is logged on and who he is</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="5615306910-31">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5615306910-31">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="9834058101-31">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9834058101-31">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5615306910-32">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="5615306910-32">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5615306910-33">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5615306910-33">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="5615306910-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5615306910-34">)</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9834058101-32">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="9834058101-32">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9834058101-33">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9834058101-33">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="9834058101-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9834058101-34">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%% If the user exists, send the message</span><span class="w">
│ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="5615306910-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5615306910-35">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="9834058101-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9834058101-35">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Find the receiver and send the message</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="5615306910-36">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5615306910-36">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="9834058101-36">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9834058101-36">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5615306910-37">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="5615306910-37">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5615306910-38">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="5615306910-38">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5615306910-39">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5615306910-39">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5615306910-40">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="5615306910-40">}</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9834058101-37">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="9834058101-37">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9834058101-38">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="9834058101-38">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9834058101-39">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9834058101-39">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9834058101-40">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="9834058101-40">}</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  
│ │ │  </span><span class="c1">%%% User Commands</span><span class="w">
│ │ │ -</span><span class="nf">logon</span><span class="p" data-group-id="5615306910-41">(</span><span class="n">Name</span><span class="p" data-group-id="5615306910-41">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="5615306910-42">(</span><span class="ss">mess_client</span><span class="p" data-group-id="5615306910-42">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">logon</span><span class="p" data-group-id="9834058101-41">(</span><span class="n">Name</span><span class="p" data-group-id="9834058101-41">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="9834058101-42">(</span><span class="ss">mess_client</span><span class="p" data-group-id="9834058101-42">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">register</span><span class="p" data-group-id="5615306910-43">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ -                     </span><span class="nf">spawn</span><span class="p" data-group-id="5615306910-44">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5615306910-45">[</span><span class="nf">server_node</span><span class="p" data-group-id="5615306910-46">(</span><span class="p" data-group-id="5615306910-46">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5615306910-45">]</span><span class="p" data-group-id="5615306910-44">)</span><span class="p" data-group-id="5615306910-43">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="nf">register</span><span class="p" data-group-id="9834058101-43">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ +                     </span><span class="nf">spawn</span><span class="p" data-group-id="9834058101-44">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9834058101-45">[</span><span class="nf">server_node</span><span class="p" data-group-id="9834058101-46">(</span><span class="p" data-group-id="9834058101-46">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9834058101-45">]</span><span class="p" data-group-id="9834058101-44">)</span><span class="p" data-group-id="9834058101-43">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">already_logged_on</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">logoff</span><span class="p" data-group-id="5615306910-47">(</span><span class="p" data-group-id="5615306910-47">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">logoff</span><span class="p" data-group-id="9834058101-47">(</span><span class="p" data-group-id="9834058101-47">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">logoff</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">message</span><span class="p" data-group-id="5615306910-48">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5615306910-48">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="5615306910-49">(</span><span class="ss">mess_client</span><span class="p" data-group-id="5615306910-49">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ +</span><span class="nf">message</span><span class="p" data-group-id="9834058101-48">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9834058101-48">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="9834058101-49">(</span><span class="ss">mess_client</span><span class="p" data-group-id="9834058101-49">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">not_logged_on</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5615306910-50">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5615306910-50">}</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9834058101-50">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9834058101-50">}</span><span class="p">,</span><span class="w">
│ │ │               </span><span class="ss">ok</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  
│ │ │  </span><span class="c1">%%% The client process which runs on each server node</span><span class="w">
│ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="5615306910-51">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5615306910-51">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5615306910-52">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="5615306910-52">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5615306910-53">{</span><span class="nf">self</span><span class="p" data-group-id="5615306910-54">(</span><span class="p" data-group-id="5615306910-54">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5615306910-53">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">await_result</span><span class="p" data-group-id="5615306910-55">(</span><span class="p" data-group-id="5615306910-55">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="5615306910-56">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5615306910-56">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="9834058101-51">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9834058101-51">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9834058101-52">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="9834058101-52">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9834058101-53">{</span><span class="nf">self</span><span class="p" data-group-id="9834058101-54">(</span><span class="p" data-group-id="9834058101-54">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9834058101-53">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">await_result</span><span class="p" data-group-id="9834058101-55">(</span><span class="p" data-group-id="9834058101-55">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="9834058101-56">(</span><span class="n">Server_Node</span><span class="p" data-group-id="9834058101-56">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="5615306910-57">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5615306910-57">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="9834058101-57">(</span><span class="n">Server_Node</span><span class="p" data-group-id="9834058101-57">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">logoff</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="5615306910-58">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="5615306910-58">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5615306910-59">{</span><span class="nf">self</span><span class="p" data-group-id="5615306910-60">(</span><span class="p" data-group-id="5615306910-60">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p" data-group-id="5615306910-59">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="5615306910-61">(</span><span class="ss">normal</span><span class="p" data-group-id="5615306910-61">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5615306910-62">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5615306910-62">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="5615306910-63">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="5615306910-63">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5615306910-64">{</span><span class="nf">self</span><span class="p" data-group-id="5615306910-65">(</span><span class="p" data-group-id="5615306910-65">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5615306910-64">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">await_result</span><span class="p" data-group-id="5615306910-66">(</span><span class="p" data-group-id="5615306910-66">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5615306910-67">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5615306910-67">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5615306910-68">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5615306910-69">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5615306910-69">]</span><span class="p" data-group-id="5615306910-68">)</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="9834058101-58">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="9834058101-58">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9834058101-59">{</span><span class="nf">self</span><span class="p" data-group-id="9834058101-60">(</span><span class="p" data-group-id="9834058101-60">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p" data-group-id="9834058101-59">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="9834058101-61">(</span><span class="ss">normal</span><span class="p" data-group-id="9834058101-61">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9834058101-62">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9834058101-62">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="9834058101-63">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="9834058101-63">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9834058101-64">{</span><span class="nf">self</span><span class="p" data-group-id="9834058101-65">(</span><span class="p" data-group-id="9834058101-65">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9834058101-64">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">await_result</span><span class="p" data-group-id="9834058101-66">(</span><span class="p" data-group-id="9834058101-66">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9834058101-67">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9834058101-67">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9834058101-68">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9834058101-69">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9834058101-69">]</span><span class="p" data-group-id="9834058101-68">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="5615306910-70">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5615306910-70">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="9834058101-70">(</span><span class="n">Server_Node</span><span class="p" data-group-id="9834058101-70">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% wait for a response from the server</span><span class="w">
│ │ │ -</span><span class="nf">await_result</span><span class="p" data-group-id="5615306910-71">(</span><span class="p" data-group-id="5615306910-71">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">await_result</span><span class="p" data-group-id="9834058101-71">(</span><span class="p" data-group-id="9834058101-71">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5615306910-72">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">Why</span><span class="p" data-group-id="5615306910-72">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Stop the client</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5615306910-73">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5615306910-74">[</span><span class="n">Why</span><span class="p" data-group-id="5615306910-74">]</span><span class="p" data-group-id="5615306910-73">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="5615306910-75">(</span><span class="ss">normal</span><span class="p" data-group-id="5615306910-75">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5615306910-76">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">What</span><span class="p" data-group-id="5615306910-76">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Normal response</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5615306910-77">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5615306910-78">[</span><span class="n">What</span><span class="p" data-group-id="5615306910-78">]</span><span class="p" data-group-id="5615306910-77">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9834058101-72">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">Why</span><span class="p" data-group-id="9834058101-72">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Stop the client</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9834058101-73">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9834058101-74">[</span><span class="n">Why</span><span class="p" data-group-id="9834058101-74">]</span><span class="p" data-group-id="9834058101-73">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="9834058101-75">(</span><span class="ss">normal</span><span class="p" data-group-id="9834058101-75">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9834058101-76">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">What</span><span class="p" data-group-id="9834058101-76">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Normal response</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9834058101-77">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9834058101-78">[</span><span class="n">What</span><span class="p" data-group-id="9834058101-78">]</span><span class="p" data-group-id="9834058101-77">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>To use this program, you need to:</p><ul><li>Configure the <code class="inline">server_node()</code> function.</li><li>Copy the compiled code (<code class="inline">messenger.beam</code>) to the directory on each computer
│ │ │  where you start Erlang.</li></ul><p>In the following example using this program, nodes are started on four different
│ │ │  computers. If you do not have that many machines available on your network, you
│ │ │  can start several nodes on the same machine.</p><p>Four Erlang nodes are started up: messenger@super, c1@bilbo, c2@kosken,
│ │ │ -c3@gollum.</p><p>First the server at messenger@super is started up:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(messenger@super)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">start_server</span><span class="p" data-group-id="1992219093-1">(</span><span class="p" data-group-id="1992219093-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="ss">true</span></code></pre><p>Now Peter logs on at c1@bilbo:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c1@bilbo)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="0941285644-1">(</span><span class="ss">peter</span><span class="p" data-group-id="0941285644-1">)</span><span class="p">.</span><span class="w">
│ │ │ +c3@gollum.</p><p>First the server at messenger@super is started up:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(messenger@super)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">start_server</span><span class="p" data-group-id="5634288676-1">(</span><span class="p" data-group-id="5634288676-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">true</span></code></pre><p>Now Peter logs on at c1@bilbo:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c1@bilbo)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="4781392207-1">(</span><span class="ss">peter</span><span class="p" data-group-id="4781392207-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="ss">logged_on</span></code></pre><p>James logs on at c2@kosken:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c2@kosken)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="3291819525-1">(</span><span class="ss">james</span><span class="p" data-group-id="3291819525-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">logged_on</span></code></pre><p>James logs on at c2@kosken:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c2@kosken)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="7458535530-1">(</span><span class="ss">james</span><span class="p" data-group-id="7458535530-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="ss">logged_on</span></code></pre><p>And Fred logs on at c3@gollum:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c3@gollum)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="8619778056-1">(</span><span class="ss">fred</span><span class="p" data-group-id="8619778056-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">logged_on</span></code></pre><p>And Fred logs on at c3@gollum:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c3@gollum)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="3522841092-1">(</span><span class="ss">fred</span><span class="p" data-group-id="3522841092-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="ss">logged_on</span></code></pre><p>Now Peter sends Fred a message:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c1@bilbo)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="8088616090-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="8088616090-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">logged_on</span></code></pre><p>Now Peter sends Fred a message:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c1@bilbo)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="2140571321-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="2140571321-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │  </span><span class="ss">sent</span></code></pre><p>Fred receives the message and sends a message to Peter and logs off:</p><pre><code class="makeup erlang" translate="no"><span class="n">Message</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="nc">peter</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">(c3@gollum)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="6626642396-1">(</span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;go away, I&#39;m busy&quot;</span><span class="p" data-group-id="6626642396-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">(c3@gollum)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="5569739174-1">(</span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;go away, I&#39;m busy&quot;</span><span class="p" data-group-id="5569739174-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │  </span><span class="nf">sent</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6626642396-2">(</span><span class="ss">c3@gollum</span><span class="p" data-group-id="6626642396-2">)</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logoff</span><span class="p" data-group-id="6626642396-3">(</span><span class="p" data-group-id="6626642396-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="ss">logoff</span></code></pre><p>James now tries to send a message to Fred:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c2@kosken)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="2553526754-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;peter doesn&#39;t like you&quot;</span><span class="p" data-group-id="2553526754-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5569739174-2">(</span><span class="ss">c3@gollum</span><span class="p" data-group-id="5569739174-2">)</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logoff</span><span class="p" data-group-id="5569739174-3">(</span><span class="p" data-group-id="5569739174-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">logoff</span></code></pre><p>James now tries to send a message to Fred:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c2@kosken)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="8723281242-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;peter doesn&#39;t like you&quot;</span><span class="p" data-group-id="8723281242-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │  </span><span class="ss">receiver_not_found</span></code></pre><p>But this fails as Fred has already logged off.</p><p>First let us look at some of the new concepts that have been introduced.</p><p>There are two versions of the <code class="inline">server_transfer</code> function: one with four
│ │ │  arguments (<code class="inline">server_transfer/4</code>) and one with five (<code class="inline">server_transfer/5</code>). These
│ │ │  are regarded by Erlang as two separate functions.</p><p>Notice how to write the <code class="inline">server</code> function so that it calls itself, through
│ │ │  <code class="inline">server(User_List)</code>, and thus creates a loop. The Erlang compiler is &quot;clever&quot;
│ │ │  and optimizes the code so that this really is a sort of loop and not a proper
│ │ │  function call. But this only works if there is no code after the call.
│ │ │  Otherwise, the compiler expects the call to return and make a proper function
│ │ │  call. This would result in the process getting bigger and bigger for every loop.</p><p>Functions in the <code class="inline">lists</code> module are used. This is a very useful module and a
│ │ │  study of the manual page is recommended (<code class="inline">erl -man lists</code>).
│ │ │  <code class="inline">lists:keymember(Key,Position,List)</code> looks through a list of tuples and looks
│ │ │  at <code class="inline">Position</code> in each tuple to see if it is the same as <code class="inline">Key</code>. The first element
│ │ │  is position 1. If it finds a tuple where the element at <code class="inline">Position</code> is the same
│ │ │ -as <code class="inline">Key</code>, it returns <code class="inline">true</code>, otherwise <code class="inline">false</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="6995063270-1">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6995063270-2">[</span><span class="p" data-group-id="6995063270-3">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="6995063270-3">}</span><span class="p">,</span><span class="p" data-group-id="6995063270-4">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6995063270-4">}</span><span class="p">,</span><span class="p" data-group-id="6995063270-5">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6995063270-5">}</span><span class="p">,</span><span class="p" data-group-id="6995063270-6">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="6995063270-6">}</span><span class="p" data-group-id="6995063270-2">]</span><span class="p" data-group-id="6995063270-1">)</span><span class="p">.</span><span class="w">
│ │ │ +as <code class="inline">Key</code>, it returns <code class="inline">true</code>, otherwise <code class="inline">false</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="6934446739-1">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6934446739-2">[</span><span class="p" data-group-id="6934446739-3">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="6934446739-3">}</span><span class="p">,</span><span class="p" data-group-id="6934446739-4">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6934446739-4">}</span><span class="p">,</span><span class="p" data-group-id="6934446739-5">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6934446739-5">}</span><span class="p">,</span><span class="p" data-group-id="6934446739-6">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="6934446739-6">}</span><span class="p" data-group-id="6934446739-2">]</span><span class="p" data-group-id="6934446739-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="6995063270-7">(</span><span class="ss">p</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6995063270-8">[</span><span class="p" data-group-id="6995063270-9">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="6995063270-9">}</span><span class="p">,</span><span class="p" data-group-id="6995063270-10">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6995063270-10">}</span><span class="p">,</span><span class="p" data-group-id="6995063270-11">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6995063270-11">}</span><span class="p">,</span><span class="p" data-group-id="6995063270-12">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="6995063270-12">}</span><span class="p" data-group-id="6995063270-8">]</span><span class="p" data-group-id="6995063270-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="6934446739-7">(</span><span class="ss">p</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6934446739-8">[</span><span class="p" data-group-id="6934446739-9">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="6934446739-9">}</span><span class="p">,</span><span class="p" data-group-id="6934446739-10">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6934446739-10">}</span><span class="p">,</span><span class="p" data-group-id="6934446739-11">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6934446739-11">}</span><span class="p">,</span><span class="p" data-group-id="6934446739-12">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="6934446739-12">}</span><span class="p" data-group-id="6934446739-8">]</span><span class="p" data-group-id="6934446739-7">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span></code></pre><p><code class="inline">lists:keydelete</code> works in the same way but deletes the first tuple found (if
│ │ │ -any) and returns the remaining list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="7833943583-1">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7833943583-2">[</span><span class="p" data-group-id="7833943583-3">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="7833943583-3">}</span><span class="p">,</span><span class="p" data-group-id="7833943583-4">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7833943583-4">}</span><span class="p">,</span><span class="p" data-group-id="7833943583-5">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="7833943583-5">}</span><span class="p">,</span><span class="p" data-group-id="7833943583-6">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="7833943583-6">}</span><span class="p" data-group-id="7833943583-2">]</span><span class="p" data-group-id="7833943583-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7833943583-7">[</span><span class="p" data-group-id="7833943583-8">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="7833943583-8">}</span><span class="p">,</span><span class="p" data-group-id="7833943583-9">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7833943583-9">}</span><span class="p">,</span><span class="p" data-group-id="7833943583-10">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="7833943583-10">}</span><span class="p" data-group-id="7833943583-7">]</span></code></pre><p><code class="inline">lists:keyfind</code> is like <code class="inline">lists:keymember</code>, but it returns
│ │ │ +any) and returns the remaining list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="3167368541-1">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3167368541-2">[</span><span class="p" data-group-id="3167368541-3">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="3167368541-3">}</span><span class="p">,</span><span class="p" data-group-id="3167368541-4">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3167368541-4">}</span><span class="p">,</span><span class="p" data-group-id="3167368541-5">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3167368541-5">}</span><span class="p">,</span><span class="p" data-group-id="3167368541-6">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="3167368541-6">}</span><span class="p" data-group-id="3167368541-2">]</span><span class="p" data-group-id="3167368541-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3167368541-7">[</span><span class="p" data-group-id="3167368541-8">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="3167368541-8">}</span><span class="p">,</span><span class="p" data-group-id="3167368541-9">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3167368541-9">}</span><span class="p">,</span><span class="p" data-group-id="3167368541-10">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="3167368541-10">}</span><span class="p" data-group-id="3167368541-7">]</span></code></pre><p><code class="inline">lists:keyfind</code> is like <code class="inline">lists:keymember</code>, but it returns
│ │ │  <code class="inline">Tuple_Found</code> or the atom <code class="inline">false</code>.</p><p>There are many very useful functions in the <code class="inline">lists</code> module.</p><p>An Erlang process (conceptually) runs until it does a <code class="inline">receive</code> and there is no
│ │ │  message which it wants to receive in the message queue. &quot;conceptually&quot; is used
│ │ │  here because the Erlang system shares the CPU time between the active processes
│ │ │  in the system.</p><p>A process terminates when there is nothing more for it to do, that is, the last
│ │ │  function it calls simply returns and does not call another function. Another way
│ │ │  for a process to terminate is for it to call <a href="../../erts-17.0/doc/html/erlang.html#exit/1"><code class="inline">exit/1</code></a>. The argument
│ │ │  to <a href="../../erts-17.0/doc/html/erlang.html#exit/1"><code class="inline">exit/1</code></a> has a special meaning, which is discussed later. In this
│ │ │  example, <a href="../../erts-17.0/doc/html/erlang.html#exit/1"><code class="inline">exit(normal)</code></a> is done, which has the same effect as a
│ │ │  process running out of functions to call.</p><p>The BIF <a href="../../erts-17.0/doc/html/erlang.html#whereis/1"><code class="inline">whereis(RegisteredName)</code></a> checks if a registered process
│ │ │  of name <code class="inline">RegisteredName</code> exists. If it exists, the pid of that process is
│ │ │  returned. If it does not exist, the atom <code class="inline">undefined</code> is returned.</p><p>You should by now be able to understand most of the code in the
│ │ │  messenger-module. Let us study one case in detail: a message is sent from one
│ │ │ -user to another.</p><p>The first user &quot;sends&quot; the message in the example above by:</p><pre><code class="makeup erlang" translate="no"><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="3660038805-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="3660038805-1">)</span></code></pre><p>After testing that the client process exists:</p><pre><code class="makeup erlang" translate="no"><span class="nf">whereis</span><span class="p" data-group-id="2159464428-1">(</span><span class="ss">mess_client</span><span class="p" data-group-id="2159464428-1">)</span></code></pre><p>And a message is sent to <code class="inline">mess_client</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0032201508-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="0032201508-1">}</span></code></pre><p>The client sends the message to the server by:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6911451854-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="6911451854-1">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6911451854-2">{</span><span class="nf">self</span><span class="p" data-group-id="6911451854-3">(</span><span class="p" data-group-id="6911451854-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="6911451854-2">}</span><span class="p">,</span></code></pre><p>And waits for a reply from the server.</p><p>The server receives this message and calls:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server_transfer</span><span class="p" data-group-id="0199677494-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0199677494-1">)</span><span class="p">,</span></code></pre><p>This checks that the pid <code class="inline">From</code> is in the <code class="inline">User_List</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="6820243544-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6820243544-1">)</span></code></pre><p>If <code class="inline">keyfind</code> returns the atom <code class="inline">false</code>, some error has occurred and the server
│ │ │ -sends back the message:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9509464720-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="9509464720-1">}</span></code></pre><p>This is received by the client, which in turn does <a href="../../erts-17.0/doc/html/erlang.html#exit/1"><code class="inline">exit(normal)</code></a>
│ │ │ +user to another.</p><p>The first user &quot;sends&quot; the message in the example above by:</p><pre><code class="makeup erlang" translate="no"><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="6004812100-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="6004812100-1">)</span></code></pre><p>After testing that the client process exists:</p><pre><code class="makeup erlang" translate="no"><span class="nf">whereis</span><span class="p" data-group-id="7035552021-1">(</span><span class="ss">mess_client</span><span class="p" data-group-id="7035552021-1">)</span></code></pre><p>And a message is sent to <code class="inline">mess_client</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4689223392-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="4689223392-1">}</span></code></pre><p>The client sends the message to the server by:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9553889774-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="9553889774-1">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9553889774-2">{</span><span class="nf">self</span><span class="p" data-group-id="9553889774-3">(</span><span class="p" data-group-id="9553889774-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="9553889774-2">}</span><span class="p">,</span></code></pre><p>And waits for a reply from the server.</p><p>The server receives this message and calls:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server_transfer</span><span class="p" data-group-id="8623398860-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="8623398860-1">)</span><span class="p">,</span></code></pre><p>This checks that the pid <code class="inline">From</code> is in the <code class="inline">User_List</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="1001136820-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1001136820-1">)</span></code></pre><p>If <code class="inline">keyfind</code> returns the atom <code class="inline">false</code>, some error has occurred and the server
│ │ │ +sends back the message:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3131947518-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="3131947518-1">}</span></code></pre><p>This is received by the client, which in turn does <a href="../../erts-17.0/doc/html/erlang.html#exit/1"><code class="inline">exit(normal)</code></a>
│ │ │  and terminates. If <code class="inline">keyfind</code> returns <code class="inline">{From,Name}</code> it is certain that
│ │ │ -the user is logged on and that their name (peter) is in the variable <code class="inline">Name</code>.</p><p>Let us now call:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server_transfer</span><span class="p" data-group-id="6385732102-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6385732102-1">)</span></code></pre><p>Notice that as this is <code class="inline">server_transfer/5</code>, it is not the same as the previous
│ │ │ +the user is logged on and that their name (peter) is in the variable <code class="inline">Name</code>.</p><p>Let us now call:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server_transfer</span><span class="p" data-group-id="5296536468-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5296536468-1">)</span></code></pre><p>Notice that as this is <code class="inline">server_transfer/5</code>, it is not the same as the previous
│ │ │  function <code class="inline">server_transfer/4</code>. Another <code class="inline">keyfind</code> is done on <code class="inline">User_List</code> to find
│ │ │ -the pid of the client corresponding to fred:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="9741456786-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9741456786-1">)</span></code></pre><p>This time argument 2 is used, which is the second element in the tuple. If this
│ │ │ +the pid of the client corresponding to fred:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="5382301848-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5382301848-1">)</span></code></pre><p>This time argument 2 is used, which is the second element in the tuple. If this
│ │ │  returns the atom <code class="inline">false</code>, fred is not logged on and the following message is
│ │ │ -sent:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6285189480-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="6285189480-1">}</span><span class="p">;</span></code></pre><p>This is received by the client.</p><p>If <code class="inline">keyfind</code> returns:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7506159901-1">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p" data-group-id="7506159901-1">}</span></code></pre><p>The following message is sent to fred's client:</p><pre><code class="makeup erlang" translate="no"><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7811698524-1">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="7811698524-1">}</span><span class="p">,</span></code></pre><p>The following message is sent to peter's client:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1189823601-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="1189823601-1">}</span></code></pre><p>Fred's client receives the message and prints it:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5070276089-1">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="5070276089-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5070276089-2">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5070276089-3">[</span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="5070276089-3">]</span><span class="p" data-group-id="5070276089-2">)</span></code></pre><p>Peter's client receives the message in the <code class="inline">await_result</code> function.</p>
│ │ │ +sent:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2263930075-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="2263930075-1">}</span><span class="p">;</span></code></pre><p>This is received by the client.</p><p>If <code class="inline">keyfind</code> returns:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8429967040-1">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p" data-group-id="8429967040-1">}</span></code></pre><p>The following message is sent to fred's client:</p><pre><code class="makeup erlang" translate="no"><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6758102376-1">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="6758102376-1">}</span><span class="p">,</span></code></pre><p>The following message is sent to peter's client:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9138701102-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="9138701102-1">}</span></code></pre><p>Fred's client receives the message and prints it:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6746315703-1">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="6746315703-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6746315703-2">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6746315703-3">[</span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="6746315703-3">]</span><span class="p" data-group-id="6746315703-2">)</span></code></pre><p>Peter's client receives the message in the <code class="inline">await_result</code> function.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="seq_prog.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/create_target.html
│ │ │ @@ -138,21 +138,21 @@
│ │ │    <span class="text">Creating a Target System</span>
│ │ │  </h2>
│ │ │  <p>It is assumed that you have a working Erlang/OTP system structured according to
│ │ │  the OTP design principles.</p><p><em>Step 1.</em> Create a <code class="inline">.rel</code> file (see the <a href="../../lib/sasl-4.4/doc/html/rel.html">rel(4)</a> manual page in
│ │ │  SASL), which specifies the ERTS version and lists all applications that are to
│ │ │  be included in the new basic target system. An example is the following
│ │ │  <code class="inline">mysystem.rel</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% mysystem.rel</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6270915992-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="6270915992-2">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;FIRST&quot;</span><span class="p" data-group-id="6270915992-2">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="6270915992-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.10.4&quot;</span><span class="p" data-group-id="6270915992-3">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="6270915992-4">[</span><span class="p" data-group-id="6270915992-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.16.4&quot;</span><span class="p" data-group-id="6270915992-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="6270915992-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1.19.4&quot;</span><span class="p" data-group-id="6270915992-6">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="6270915992-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.3.4&quot;</span><span class="p" data-group-id="6270915992-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="6270915992-8">{</span><span class="ss">pea</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="6270915992-8">}</span><span class="p" data-group-id="6270915992-4">]</span><span class="p" data-group-id="6270915992-1">}</span><span class="p">.</span></code></pre><p>The listed applications are not only original Erlang/OTP applications but
│ │ │ +</span><span class="p" data-group-id="5613075378-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5613075378-2">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;FIRST&quot;</span><span class="p" data-group-id="5613075378-2">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5613075378-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.10.4&quot;</span><span class="p" data-group-id="5613075378-3">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5613075378-4">[</span><span class="p" data-group-id="5613075378-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.16.4&quot;</span><span class="p" data-group-id="5613075378-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="5613075378-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1.19.4&quot;</span><span class="p" data-group-id="5613075378-6">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="5613075378-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.3.4&quot;</span><span class="p" data-group-id="5613075378-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="5613075378-8">{</span><span class="ss">pea</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="5613075378-8">}</span><span class="p" data-group-id="5613075378-4">]</span><span class="p" data-group-id="5613075378-1">}</span><span class="p">.</span></code></pre><p>The listed applications are not only original Erlang/OTP applications but
│ │ │  possibly also new applications that you have written (here exemplified by the
│ │ │  application Pea (<code class="inline">pea</code>)).</p><p><em>Step 2.</em> Start Erlang/OTP from the directory where the <code class="inline">mysystem.rel</code> file
│ │ │  resides:</p><pre><code class="text">% erl -pa /home/user/target_system/myapps/pea-1.0/ebin</code></pre><p>The <code class="inline">-pa</code> argument prepends the path to the <code class="inline">ebin</code> directory for
│ │ │  the Pea application to the code path.</p><p><em>Step 3.</em> Create the target system:</p><pre><code class="text">1&gt; target_system:create(&quot;mysystem&quot;).</code></pre><p>The function <code class="inline">target_system:create/1</code> performs the following:</p><ol><li><p>Reads the file <code class="inline">mysystem.rel</code> and creates a new file <code class="inline">plain.rel</code>.
│ │ │  The new file is identical to the original, except that it only
│ │ │  lists the Kernel and STDLIB applications.</p></li><li><p>From the files <code class="inline">mysystem.rel</code> and <code class="inline">plain.rel</code> creates the files
│ │ │  <code class="inline">mysystem.script</code>, <code class="inline">mysystem.boot</code>, <code class="inline">plain.script</code>, and <code class="inline">plain.boot</code>
│ │ │ @@ -242,25 +242,25 @@
│ │ │    <a href="#creating-the-next-version" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Creating the Next Version</span>
│ │ │  </h2>
│ │ │  <p>In this example the Pea application has been changed, and so have the
│ │ │  applications ERTS, Kernel, STDLIB and SASL.</p><p><em>Step 1.</em> Create the file <code class="inline">.rel</code>:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% mysystem2.rel</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7117499566-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7117499566-2">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;SECOND&quot;</span><span class="p" data-group-id="7117499566-2">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7117499566-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;6.0&quot;</span><span class="p" data-group-id="7117499566-3">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7117499566-4">[</span><span class="p" data-group-id="7117499566-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;3.0&quot;</span><span class="p" data-group-id="7117499566-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="7117499566-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="7117499566-6">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="7117499566-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.4&quot;</span><span class="p" data-group-id="7117499566-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="7117499566-8">{</span><span class="ss">pea</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="7117499566-8">}</span><span class="p" data-group-id="7117499566-4">]</span><span class="p" data-group-id="7117499566-1">}</span><span class="p">.</span></code></pre><p><em>Step 2.</em> Create the application upgrade file (see
│ │ │ +</span><span class="p" data-group-id="0867049380-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0867049380-2">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;SECOND&quot;</span><span class="p" data-group-id="0867049380-2">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0867049380-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;6.0&quot;</span><span class="p" data-group-id="0867049380-3">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0867049380-4">[</span><span class="p" data-group-id="0867049380-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;3.0&quot;</span><span class="p" data-group-id="0867049380-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="0867049380-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="0867049380-6">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="0867049380-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.4&quot;</span><span class="p" data-group-id="0867049380-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="0867049380-8">{</span><span class="ss">pea</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="0867049380-8">}</span><span class="p" data-group-id="0867049380-4">]</span><span class="p" data-group-id="0867049380-1">}</span><span class="p">.</span></code></pre><p><em>Step 2.</em> Create the application upgrade file (see
│ │ │  <a href="../../lib/sasl-4.4/doc/html/appup.html">appup</a> in SASL) for Pea, for example:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% pea.appup</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0690008998-1">{</span><span class="s">&quot;2.0&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0690008998-2">[</span><span class="p" data-group-id="0690008998-3">{</span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="p" data-group-id="0690008998-4">[</span><span class="p" data-group-id="0690008998-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="ss">pea_lib</span><span class="p" data-group-id="0690008998-5">}</span><span class="p" data-group-id="0690008998-4">]</span><span class="p" data-group-id="0690008998-3">}</span><span class="p" data-group-id="0690008998-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0690008998-6">[</span><span class="p" data-group-id="0690008998-7">{</span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="p" data-group-id="0690008998-8">[</span><span class="p" data-group-id="0690008998-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="ss">pea_lib</span><span class="p" data-group-id="0690008998-9">}</span><span class="p" data-group-id="0690008998-8">]</span><span class="p" data-group-id="0690008998-7">}</span><span class="p" data-group-id="0690008998-6">]</span><span class="p" data-group-id="0690008998-1">}</span><span class="p">.</span></code></pre><p><em>Step 3.</em> From the directory where the file <code class="inline">mysystem2.rel</code> resides, start the
│ │ │ +</span><span class="p" data-group-id="7490597071-1">{</span><span class="s">&quot;2.0&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7490597071-2">[</span><span class="p" data-group-id="7490597071-3">{</span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="p" data-group-id="7490597071-4">[</span><span class="p" data-group-id="7490597071-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="ss">pea_lib</span><span class="p" data-group-id="7490597071-5">}</span><span class="p" data-group-id="7490597071-4">]</span><span class="p" data-group-id="7490597071-3">}</span><span class="p" data-group-id="7490597071-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7490597071-6">[</span><span class="p" data-group-id="7490597071-7">{</span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="p" data-group-id="7490597071-8">[</span><span class="p" data-group-id="7490597071-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="ss">pea_lib</span><span class="p" data-group-id="7490597071-9">}</span><span class="p" data-group-id="7490597071-8">]</span><span class="p" data-group-id="7490597071-7">}</span><span class="p" data-group-id="7490597071-6">]</span><span class="p" data-group-id="7490597071-1">}</span><span class="p">.</span></code></pre><p><em>Step 3.</em> From the directory where the file <code class="inline">mysystem2.rel</code> resides, start the
│ │ │  Erlang/OTP system, giving the path to the new version of Pea:</p><pre><code class="text">% erl -pa /home/user/target_system/myapps/pea-2.0/ebin</code></pre><p><em>Step 4.</em> Create the release upgrade file (see <a href="../../lib/sasl-4.4/doc/html/relup.html">relup</a>
│ │ │  in SASL):</p><pre><code class="text">1&gt; systools:make_relup(&quot;mysystem2&quot;,[&quot;mysystem&quot;],[&quot;mysystem&quot;],
│ │ │      [{path,[&quot;/home/user/target_system/myapps/pea-1.0/ebin&quot;,
│ │ │      &quot;/my/old/erlang/lib/*/ebin&quot;]}]).</code></pre><p>Here <code class="inline">&quot;mysystem&quot;</code> is the base release and <code class="inline">&quot;mysystem2&quot;</code> is the release to
│ │ │  upgrade to.</p><p>The <code class="inline">path</code> option is used for pointing out the old version of all applications.
│ │ │  (The new versions are already in the code path - assuming of course that the
│ │ │  Erlang node on which this is executed is running the correct version of
│ │ │ @@ -292,291 +292,291 @@
│ │ │  {continue_after_restart,&quot;FIRST&quot;,[]}
│ │ │  heart: Tue Apr  1 12:15:10 2014: Erlang has closed.
│ │ │  heart: Tue Apr  1 12:15:11 2014: Executed &quot;/usr/local/erl-target/bin/start /usr/local/erl-target/releases/new_start_erl.data&quot; -&gt; 0. Terminating.
│ │ │  [End]</code></pre><p>The above return value and output after the call to
│ │ │  <a href="../../lib/sasl-4.4/doc/html/release_handler.html#install_release/1"><code class="inline">release_handler:install_release/1</code></a> means that the <code class="inline">release_handler</code> has
│ │ │  restarted the node by using <code class="inline">heart</code>. This is always done when the upgrade
│ │ │  involves a change of the applications ERTS, Kernel, STDLIB, or SASL. For more
│ │ │ -information, see <a href="upgrade.html">Upgrade when Erlang/OTP has Changed</a>.</p><p>The node is accessible through a new pipe:</p><pre><code class="text">% /usr/local/erl-target/bin/to_erl /tmp/erlang.pipe.2</code></pre><p>List the available releases in the system:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">which_releases</span><span class="p" data-group-id="7310660715-1">(</span><span class="p" data-group-id="7310660715-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7310660715-2">[</span><span class="p" data-group-id="7310660715-3">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;SECOND&quot;</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="7310660715-4">[</span><span class="s">&quot;kernel-3.0&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-2.0&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-2.0&quot;</span><span class="p" data-group-id="7310660715-4">]</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">current</span><span class="p" data-group-id="7310660715-3">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7310660715-5">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;FIRST&quot;</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="7310660715-6">[</span><span class="s">&quot;kernel-2.16.4&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-1.19.4&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.3.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-1.0&quot;</span><span class="p" data-group-id="7310660715-6">]</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">permanent</span><span class="p" data-group-id="7310660715-5">}</span><span class="p" data-group-id="7310660715-2">]</span></code></pre><p>Our new release, &quot;SECOND&quot;, is now the current release, but we can also see that
│ │ │ +information, see <a href="upgrade.html">Upgrade when Erlang/OTP has Changed</a>.</p><p>The node is accessible through a new pipe:</p><pre><code class="text">% /usr/local/erl-target/bin/to_erl /tmp/erlang.pipe.2</code></pre><p>List the available releases in the system:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">which_releases</span><span class="p" data-group-id="6475051422-1">(</span><span class="p" data-group-id="6475051422-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6475051422-2">[</span><span class="p" data-group-id="6475051422-3">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;SECOND&quot;</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6475051422-4">[</span><span class="s">&quot;kernel-3.0&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-2.0&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-2.0&quot;</span><span class="p" data-group-id="6475051422-4">]</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="ss">current</span><span class="p" data-group-id="6475051422-3">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="6475051422-5">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;FIRST&quot;</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6475051422-6">[</span><span class="s">&quot;kernel-2.16.4&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-1.19.4&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.3.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-1.0&quot;</span><span class="p" data-group-id="6475051422-6">]</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="ss">permanent</span><span class="p" data-group-id="6475051422-5">}</span><span class="p" data-group-id="6475051422-2">]</span></code></pre><p>Our new release, &quot;SECOND&quot;, is now the current release, but we can also see that
│ │ │  our &quot;FIRST&quot; release is still permanent. This means that if the node would be
│ │ │ -restarted now, it would come up running the &quot;FIRST&quot; release again.</p><p><em>Step 3.</em> Make the new release permanent:</p><pre><code class="text">2&gt; release_handler:make_permanent(&quot;SECOND&quot;).</code></pre><p>Check the releases again:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">which_releases</span><span class="p" data-group-id="9077076473-1">(</span><span class="p" data-group-id="9077076473-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9077076473-2">[</span><span class="p" data-group-id="9077076473-3">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;SECOND&quot;</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9077076473-4">[</span><span class="s">&quot;kernel-3.0&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-2.0&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-2.0&quot;</span><span class="p" data-group-id="9077076473-4">]</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">permanent</span><span class="p" data-group-id="9077076473-3">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9077076473-5">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;FIRST&quot;</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9077076473-6">[</span><span class="s">&quot;kernel-2.16.4&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-1.19.4&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.3.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-1.0&quot;</span><span class="p" data-group-id="9077076473-6">]</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">old</span><span class="p" data-group-id="9077076473-5">}</span><span class="p" data-group-id="9077076473-2">]</span></code></pre><p>We see that the new release version is <code class="inline">permanent</code>, so it would be safe to
│ │ │ +restarted now, it would come up running the &quot;FIRST&quot; release again.</p><p><em>Step 3.</em> Make the new release permanent:</p><pre><code class="text">2&gt; release_handler:make_permanent(&quot;SECOND&quot;).</code></pre><p>Check the releases again:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">which_releases</span><span class="p" data-group-id="4250552153-1">(</span><span class="p" data-group-id="4250552153-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4250552153-2">[</span><span class="p" data-group-id="4250552153-3">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;SECOND&quot;</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4250552153-4">[</span><span class="s">&quot;kernel-3.0&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-2.0&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-2.0&quot;</span><span class="p" data-group-id="4250552153-4">]</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="ss">permanent</span><span class="p" data-group-id="4250552153-3">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4250552153-5">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;FIRST&quot;</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4250552153-6">[</span><span class="s">&quot;kernel-2.16.4&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-1.19.4&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.3.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-1.0&quot;</span><span class="p" data-group-id="4250552153-6">]</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="ss">old</span><span class="p" data-group-id="4250552153-5">}</span><span class="p" data-group-id="4250552153-2">]</span></code></pre><p>We see that the new release version is <code class="inline">permanent</code>, so it would be safe to
│ │ │  restart the node.</p><p><a href="" id="listing-of-target-system"></a></p><h2 id="listing-of-target_system-erl" class="section-heading">
│ │ │    <a href="#listing-of-target_system-erl" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Listing of target_system.erl</span>
│ │ │  </h2>
│ │ │  <p>This module can also be found in the <code class="inline">examples</code> directory of the SASL
│ │ │  application.</p><pre><code class="makeup erlang" translate="no"><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9366906968-1">(</span><span class="ss">target_system</span><span class="p" data-group-id="9366906968-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9366906968-2">(</span><span class="p" data-group-id="9366906968-3">[</span><span class="ss">create</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">create</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">install</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9366906968-3">]</span><span class="p" data-group-id="9366906968-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5165383622-1">(</span><span class="ss">target_system</span><span class="p" data-group-id="5165383622-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5165383622-2">(</span><span class="p" data-group-id="5165383622-3">[</span><span class="ss">create</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">create</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">install</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5165383622-3">]</span><span class="p" data-group-id="5165383622-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% Note: RelFileName below is the *stem* without trailing .rel,</span><span class="w">
│ │ │  </span><span class="c1">%% .script etc.</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% create(RelFileName)</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ -</span><span class="nf">create</span><span class="p" data-group-id="9366906968-4">(</span><span class="n">RelFileName</span><span class="p" data-group-id="9366906968-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">create</span><span class="p" data-group-id="9366906968-5">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="p" data-group-id="9366906968-6">[</span><span class="p" data-group-id="9366906968-6">]</span><span class="p" data-group-id="9366906968-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">create</span><span class="p" data-group-id="5165383622-4">(</span><span class="n">RelFileName</span><span class="p" data-group-id="5165383622-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">create</span><span class="p" data-group-id="5165383622-5">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="p" data-group-id="5165383622-6">[</span><span class="p" data-group-id="5165383622-6">]</span><span class="p" data-group-id="5165383622-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">create</span><span class="p" data-group-id="9366906968-7">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="9366906968-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">create</span><span class="p" data-group-id="5165383622-7">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="5165383622-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">RelFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.rel&quot;</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Dir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="9366906968-8">(</span><span class="n">RelFileName</span><span class="p" data-group-id="9366906968-8">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">PlainRelFileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-9">(</span><span class="n">Dir</span><span class="p">,</span><span class="s">&quot;plain&quot;</span><span class="p" data-group-id="9366906968-9">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Dir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="5165383622-8">(</span><span class="n">RelFileName</span><span class="p" data-group-id="5165383622-8">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">PlainRelFileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-9">(</span><span class="n">Dir</span><span class="p">,</span><span class="s">&quot;plain&quot;</span><span class="p" data-group-id="5165383622-9">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="n">PlainRelFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">PlainRelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.rel&quot;</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-10">(</span><span class="s">&quot;Reading file: ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-11">[</span><span class="n">RelFile</span><span class="p" data-group-id="9366906968-11">]</span><span class="p" data-group-id="9366906968-10">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9366906968-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-13">[</span><span class="n">RelSpec</span><span class="p" data-group-id="9366906968-13">]</span><span class="p" data-group-id="9366906968-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">consult</span><span class="p" data-group-id="9366906968-14">(</span><span class="n">RelFile</span><span class="p" data-group-id="9366906968-14">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-15">(</span><span class="s">&quot;Creating file: ~ts from ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="9366906968-16">[</span><span class="n">PlainRelFile</span><span class="p">,</span><span class="w"> </span><span class="n">RelFile</span><span class="p" data-group-id="9366906968-16">]</span><span class="p" data-group-id="9366906968-15">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9366906968-17">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="9366906968-18">{</span><span class="n">RelName</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="9366906968-18">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="9366906968-19">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p" data-group-id="9366906968-19">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="n">AppVsns</span><span class="p" data-group-id="9366906968-17">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelSpec</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">PlainRelSpec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9366906968-20">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="9366906968-21">{</span><span class="n">RelName</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="9366906968-21">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="9366906968-22">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p" data-group-id="9366906968-22">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="9366906968-23">(</span><span class="nf">fun</span><span class="p" data-group-id="9366906968-24">(</span><span class="p" data-group-id="9366906968-25">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9366906968-25">}</span><span class="p" data-group-id="9366906968-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-10">(</span><span class="s">&quot;Reading file: ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-11">[</span><span class="n">RelFile</span><span class="p" data-group-id="5165383622-11">]</span><span class="p" data-group-id="5165383622-10">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5165383622-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-13">[</span><span class="n">RelSpec</span><span class="p" data-group-id="5165383622-13">]</span><span class="p" data-group-id="5165383622-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">consult</span><span class="p" data-group-id="5165383622-14">(</span><span class="n">RelFile</span><span class="p" data-group-id="5165383622-14">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-15">(</span><span class="s">&quot;Creating file: ~ts from ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="5165383622-16">[</span><span class="n">PlainRelFile</span><span class="p">,</span><span class="w"> </span><span class="n">RelFile</span><span class="p" data-group-id="5165383622-16">]</span><span class="p" data-group-id="5165383622-15">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5165383622-17">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="5165383622-18">{</span><span class="n">RelName</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="5165383622-18">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="5165383622-19">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p" data-group-id="5165383622-19">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="n">AppVsns</span><span class="p" data-group-id="5165383622-17">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelSpec</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">PlainRelSpec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5165383622-20">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="5165383622-21">{</span><span class="n">RelName</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="5165383622-21">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="5165383622-22">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p" data-group-id="5165383622-22">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="5165383622-23">(</span><span class="nf">fun</span><span class="p" data-group-id="5165383622-24">(</span><span class="p" data-group-id="5165383622-25">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="5165383622-25">}</span><span class="p" data-group-id="5165383622-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                                           </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ -                                    </span><span class="p" data-group-id="9366906968-26">(</span><span class="p" data-group-id="9366906968-27">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9366906968-27">}</span><span class="p" data-group-id="9366906968-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                                    </span><span class="p" data-group-id="5165383622-26">(</span><span class="p" data-group-id="5165383622-27">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="5165383622-27">}</span><span class="p" data-group-id="5165383622-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                                           </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ -                                    </span><span class="p" data-group-id="9366906968-28">(</span><span class="p">_</span><span class="p" data-group-id="9366906968-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                                    </span><span class="p" data-group-id="5165383622-28">(</span><span class="p">_</span><span class="p" data-group-id="5165383622-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                                           </span><span class="ss">false</span><span class="w">
│ │ │ -                                 </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsns</span><span class="p" data-group-id="9366906968-23">)</span><span class="w">
│ │ │ -                   </span><span class="p" data-group-id="9366906968-20">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9366906968-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="9366906968-29">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="9366906968-30">(</span><span class="n">PlainRelFile</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-31">[</span><span class="ss">write</span><span class="p" data-group-id="9366906968-31">]</span><span class="p" data-group-id="9366906968-30">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-32">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s">.</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-33">[</span><span class="n">PlainRelSpec</span><span class="p" data-group-id="9366906968-33">]</span><span class="p" data-group-id="9366906968-32">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="9366906968-34">(</span><span class="n">Fd</span><span class="p" data-group-id="9366906968-34">)</span><span class="p">,</span><span class="w">
│ │ │ -
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-35">(</span><span class="s">&quot;Making \&quot;~ts.script\&quot; and \&quot;~ts.boot\&quot; files ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -	      </span><span class="p" data-group-id="9366906968-36">[</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="n">PlainRelFileName</span><span class="p" data-group-id="9366906968-36">]</span><span class="p" data-group-id="9366906968-35">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">make_script</span><span class="p" data-group-id="9366906968-37">(</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="9366906968-37">)</span><span class="p">,</span><span class="w">
│ │ │ -
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-38">(</span><span class="s">&quot;Making \&quot;~ts.script\&quot; and \&quot;~ts.boot\&quot; files ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="9366906968-39">[</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="p" data-group-id="9366906968-39">]</span><span class="p" data-group-id="9366906968-38">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">make_script</span><span class="p" data-group-id="9366906968-40">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="9366906968-40">)</span><span class="p">,</span><span class="w">
│ │ │ +                                 </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsns</span><span class="p" data-group-id="5165383622-23">)</span><span class="w">
│ │ │ +                   </span><span class="p" data-group-id="5165383622-20">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5165383622-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="5165383622-29">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="5165383622-30">(</span><span class="n">PlainRelFile</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-31">[</span><span class="ss">write</span><span class="p" data-group-id="5165383622-31">]</span><span class="p" data-group-id="5165383622-30">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-32">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s">.</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-33">[</span><span class="n">PlainRelSpec</span><span class="p" data-group-id="5165383622-33">]</span><span class="p" data-group-id="5165383622-32">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="5165383622-34">(</span><span class="n">Fd</span><span class="p" data-group-id="5165383622-34">)</span><span class="p">,</span><span class="w">
│ │ │ +
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-35">(</span><span class="s">&quot;Making \&quot;~ts.script\&quot; and \&quot;~ts.boot\&quot; files ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +	      </span><span class="p" data-group-id="5165383622-36">[</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="n">PlainRelFileName</span><span class="p" data-group-id="5165383622-36">]</span><span class="p" data-group-id="5165383622-35">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">make_script</span><span class="p" data-group-id="5165383622-37">(</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="5165383622-37">)</span><span class="p">,</span><span class="w">
│ │ │ +
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-38">(</span><span class="s">&quot;Making \&quot;~ts.script\&quot; and \&quot;~ts.boot\&quot; files ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="5165383622-39">[</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="p" data-group-id="5165383622-39">]</span><span class="p" data-group-id="5165383622-38">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">make_script</span><span class="p" data-group-id="5165383622-40">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="5165383622-40">)</span><span class="p">,</span><span class="w">
│ │ │  
│ │ │      </span><span class="n">TarFileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.tar.gz&quot;</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-41">(</span><span class="s">&quot;Creating tar file ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-42">[</span><span class="n">TarFileName</span><span class="p" data-group-id="9366906968-42">]</span><span class="p" data-group-id="9366906968-41">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">make_tar</span><span class="p" data-group-id="9366906968-43">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="9366906968-43">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-41">(</span><span class="s">&quot;Creating tar file ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-42">[</span><span class="n">TarFileName</span><span class="p" data-group-id="5165383622-42">]</span><span class="p" data-group-id="5165383622-41">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">make_tar</span><span class="p" data-group-id="5165383622-43">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="5165383622-43">)</span><span class="p">,</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="n">TmpDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-44">(</span><span class="n">Dir</span><span class="p">,</span><span class="s">&quot;tmp&quot;</span><span class="p" data-group-id="9366906968-44">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-45">(</span><span class="s">&quot;Creating directory ~tp ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="9366906968-46">[</span><span class="n">TmpDir</span><span class="p" data-group-id="9366906968-46">]</span><span class="p" data-group-id="9366906968-45">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="9366906968-47">(</span><span class="n">TmpDir</span><span class="p" data-group-id="9366906968-47">)</span><span class="p">,</span><span class="w">
│ │ │ -
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-48">(</span><span class="s">&quot;Extracting ~ts into directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-49">[</span><span class="n">TarFileName</span><span class="p">,</span><span class="n">TmpDir</span><span class="p" data-group-id="9366906968-49">]</span><span class="p" data-group-id="9366906968-48">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">extract_tar</span><span class="p" data-group-id="9366906968-50">(</span><span class="n">TarFileName</span><span class="p">,</span><span class="w"> </span><span class="n">TmpDir</span><span class="p" data-group-id="9366906968-50">)</span><span class="p">,</span><span class="w">
│ │ │ -
│ │ │ -    </span><span class="n">TmpBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-51">(</span><span class="p" data-group-id="9366906968-52">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="9366906968-52">]</span><span class="p" data-group-id="9366906968-51">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">ErtsBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-53">(</span><span class="p" data-group-id="9366906968-54">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="9366906968-54">]</span><span class="p" data-group-id="9366906968-53">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-55">(</span><span class="s">&quot;Deleting \&quot;erl\&quot; and \&quot;start\&quot; in directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="9366906968-56">[</span><span class="n">ErtsBinDir</span><span class="p" data-group-id="9366906968-56">]</span><span class="p" data-group-id="9366906968-55">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="9366906968-57">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-58">(</span><span class="p" data-group-id="9366906968-59">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erl&quot;</span><span class="p" data-group-id="9366906968-59">]</span><span class="p" data-group-id="9366906968-58">)</span><span class="p" data-group-id="9366906968-57">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="9366906968-60">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-61">(</span><span class="p" data-group-id="9366906968-62">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start&quot;</span><span class="p" data-group-id="9366906968-62">]</span><span class="p" data-group-id="9366906968-61">)</span><span class="p" data-group-id="9366906968-60">)</span><span class="p">,</span><span class="w">
│ │ │ -
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-63">(</span><span class="s">&quot;Creating temporary directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-64">[</span><span class="n">TmpBinDir</span><span class="p" data-group-id="9366906968-64">]</span><span class="p" data-group-id="9366906968-63">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="9366906968-65">(</span><span class="n">TmpBinDir</span><span class="p" data-group-id="9366906968-65">)</span><span class="p">,</span><span class="w">
│ │ │ -
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-66">(</span><span class="s">&quot;Copying file \&quot;~ts.boot\&quot; to ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="9366906968-67">[</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-68">(</span><span class="p" data-group-id="9366906968-69">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start.boot&quot;</span><span class="p" data-group-id="9366906968-69">]</span><span class="p" data-group-id="9366906968-68">)</span><span class="p" data-group-id="9366906968-67">]</span><span class="p" data-group-id="9366906968-66">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="9366906968-70">(</span><span class="n">PlainRelFileName</span><span class="o">++</span><span class="s">&quot;.boot&quot;</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-71">(</span><span class="p" data-group-id="9366906968-72">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start.boot&quot;</span><span class="p" data-group-id="9366906968-72">]</span><span class="p" data-group-id="9366906968-71">)</span><span class="p" data-group-id="9366906968-70">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">TmpDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-44">(</span><span class="n">Dir</span><span class="p">,</span><span class="s">&quot;tmp&quot;</span><span class="p" data-group-id="5165383622-44">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-45">(</span><span class="s">&quot;Creating directory ~tp ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="5165383622-46">[</span><span class="n">TmpDir</span><span class="p" data-group-id="5165383622-46">]</span><span class="p" data-group-id="5165383622-45">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="5165383622-47">(</span><span class="n">TmpDir</span><span class="p" data-group-id="5165383622-47">)</span><span class="p">,</span><span class="w">
│ │ │ +
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-48">(</span><span class="s">&quot;Extracting ~ts into directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-49">[</span><span class="n">TarFileName</span><span class="p">,</span><span class="n">TmpDir</span><span class="p" data-group-id="5165383622-49">]</span><span class="p" data-group-id="5165383622-48">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">extract_tar</span><span class="p" data-group-id="5165383622-50">(</span><span class="n">TarFileName</span><span class="p">,</span><span class="w"> </span><span class="n">TmpDir</span><span class="p" data-group-id="5165383622-50">)</span><span class="p">,</span><span class="w">
│ │ │ +
│ │ │ +    </span><span class="n">TmpBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-51">(</span><span class="p" data-group-id="5165383622-52">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="5165383622-52">]</span><span class="p" data-group-id="5165383622-51">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">ErtsBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-53">(</span><span class="p" data-group-id="5165383622-54">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="5165383622-54">]</span><span class="p" data-group-id="5165383622-53">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-55">(</span><span class="s">&quot;Deleting \&quot;erl\&quot; and \&quot;start\&quot; in directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="5165383622-56">[</span><span class="n">ErtsBinDir</span><span class="p" data-group-id="5165383622-56">]</span><span class="p" data-group-id="5165383622-55">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="5165383622-57">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-58">(</span><span class="p" data-group-id="5165383622-59">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erl&quot;</span><span class="p" data-group-id="5165383622-59">]</span><span class="p" data-group-id="5165383622-58">)</span><span class="p" data-group-id="5165383622-57">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="5165383622-60">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-61">(</span><span class="p" data-group-id="5165383622-62">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start&quot;</span><span class="p" data-group-id="5165383622-62">]</span><span class="p" data-group-id="5165383622-61">)</span><span class="p" data-group-id="5165383622-60">)</span><span class="p">,</span><span class="w">
│ │ │ +
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-63">(</span><span class="s">&quot;Creating temporary directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-64">[</span><span class="n">TmpBinDir</span><span class="p" data-group-id="5165383622-64">]</span><span class="p" data-group-id="5165383622-63">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="5165383622-65">(</span><span class="n">TmpBinDir</span><span class="p" data-group-id="5165383622-65">)</span><span class="p">,</span><span class="w">
│ │ │ +
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-66">(</span><span class="s">&quot;Copying file \&quot;~ts.boot\&quot; to ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="5165383622-67">[</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-68">(</span><span class="p" data-group-id="5165383622-69">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start.boot&quot;</span><span class="p" data-group-id="5165383622-69">]</span><span class="p" data-group-id="5165383622-68">)</span><span class="p" data-group-id="5165383622-67">]</span><span class="p" data-group-id="5165383622-66">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="5165383622-70">(</span><span class="n">PlainRelFileName</span><span class="o">++</span><span class="s">&quot;.boot&quot;</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-71">(</span><span class="p" data-group-id="5165383622-72">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start.boot&quot;</span><span class="p" data-group-id="5165383622-72">]</span><span class="p" data-group-id="5165383622-71">)</span><span class="p" data-group-id="5165383622-70">)</span><span class="p">,</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-73">(</span><span class="s">&quot;Copying files \&quot;epmd\&quot;, \&quot;run_erl\&quot; and \&quot;to_erl\&quot; from \n&quot;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-73">(</span><span class="s">&quot;Copying files \&quot;epmd\&quot;, \&quot;run_erl\&quot; and \&quot;to_erl\&quot; from \n&quot;</span><span class="w">
│ │ │                </span><span class="s">&quot;~ts to ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="9366906968-74">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="n">TmpBinDir</span><span class="p" data-group-id="9366906968-74">]</span><span class="p" data-group-id="9366906968-73">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="9366906968-75">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-76">(</span><span class="p" data-group-id="9366906968-77">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;epmd&quot;</span><span class="p" data-group-id="9366906968-77">]</span><span class="p" data-group-id="9366906968-76">)</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-78">(</span><span class="p" data-group-id="9366906968-79">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;epmd&quot;</span><span class="p" data-group-id="9366906968-79">]</span><span class="p" data-group-id="9366906968-78">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-80">[</span><span class="ss">preserve</span><span class="p" data-group-id="9366906968-80">]</span><span class="p" data-group-id="9366906968-75">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="9366906968-81">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-82">(</span><span class="p" data-group-id="9366906968-83">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;run_erl&quot;</span><span class="p" data-group-id="9366906968-83">]</span><span class="p" data-group-id="9366906968-82">)</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-84">(</span><span class="p" data-group-id="9366906968-85">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;run_erl&quot;</span><span class="p" data-group-id="9366906968-85">]</span><span class="p" data-group-id="9366906968-84">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-86">[</span><span class="ss">preserve</span><span class="p" data-group-id="9366906968-86">]</span><span class="p" data-group-id="9366906968-81">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="9366906968-87">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-88">(</span><span class="p" data-group-id="9366906968-89">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;to_erl&quot;</span><span class="p" data-group-id="9366906968-89">]</span><span class="p" data-group-id="9366906968-88">)</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-90">(</span><span class="p" data-group-id="9366906968-91">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;to_erl&quot;</span><span class="p" data-group-id="9366906968-91">]</span><span class="p" data-group-id="9366906968-90">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-92">[</span><span class="ss">preserve</span><span class="p" data-group-id="9366906968-92">]</span><span class="p" data-group-id="9366906968-87">)</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="5165383622-74">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="n">TmpBinDir</span><span class="p" data-group-id="5165383622-74">]</span><span class="p" data-group-id="5165383622-73">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="5165383622-75">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-76">(</span><span class="p" data-group-id="5165383622-77">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;epmd&quot;</span><span class="p" data-group-id="5165383622-77">]</span><span class="p" data-group-id="5165383622-76">)</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-78">(</span><span class="p" data-group-id="5165383622-79">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;epmd&quot;</span><span class="p" data-group-id="5165383622-79">]</span><span class="p" data-group-id="5165383622-78">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-80">[</span><span class="ss">preserve</span><span class="p" data-group-id="5165383622-80">]</span><span class="p" data-group-id="5165383622-75">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="5165383622-81">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-82">(</span><span class="p" data-group-id="5165383622-83">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;run_erl&quot;</span><span class="p" data-group-id="5165383622-83">]</span><span class="p" data-group-id="5165383622-82">)</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-84">(</span><span class="p" data-group-id="5165383622-85">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;run_erl&quot;</span><span class="p" data-group-id="5165383622-85">]</span><span class="p" data-group-id="5165383622-84">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-86">[</span><span class="ss">preserve</span><span class="p" data-group-id="5165383622-86">]</span><span class="p" data-group-id="5165383622-81">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="5165383622-87">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-88">(</span><span class="p" data-group-id="5165383622-89">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;to_erl&quot;</span><span class="p" data-group-id="5165383622-89">]</span><span class="p" data-group-id="5165383622-88">)</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-90">(</span><span class="p" data-group-id="5165383622-91">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;to_erl&quot;</span><span class="p" data-group-id="5165383622-91">]</span><span class="p" data-group-id="5165383622-90">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-92">[</span><span class="ss">preserve</span><span class="p" data-group-id="5165383622-92">]</span><span class="p" data-group-id="5165383622-87">)</span><span class="p">,</span><span class="w">
│ │ │  
│ │ │      </span><span class="c1">%% This is needed if &#39;start&#39; script created from &#39;start.src&#39; shall</span><span class="w">
│ │ │      </span><span class="c1">%% be used as it points out this directory as log dir for &#39;run_erl&#39;</span><span class="w">
│ │ │ -    </span><span class="n">TmpLogDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-93">(</span><span class="p" data-group-id="9366906968-94">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;log&quot;</span><span class="p" data-group-id="9366906968-94">]</span><span class="p" data-group-id="9366906968-93">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-95">(</span><span class="s">&quot;Creating temporary directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-96">[</span><span class="n">TmpLogDir</span><span class="p" data-group-id="9366906968-96">]</span><span class="p" data-group-id="9366906968-95">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="9366906968-97">(</span><span class="n">TmpLogDir</span><span class="p" data-group-id="9366906968-97">)</span><span class="p">,</span><span class="w">
│ │ │ -
│ │ │ -    </span><span class="n">StartErlDataFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-98">(</span><span class="p" data-group-id="9366906968-99">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl.data&quot;</span><span class="p" data-group-id="9366906968-99">]</span><span class="p" data-group-id="9366906968-98">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-100">(</span><span class="s">&quot;Creating ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-101">[</span><span class="n">StartErlDataFile</span><span class="p" data-group-id="9366906968-101">]</span><span class="p" data-group-id="9366906968-100">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">StartErlData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">io_lib</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-102">(</span><span class="s">&quot;</span><span class="si">~s</span><span class="s"> </span><span class="si">~s</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-103">[</span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="9366906968-103">]</span><span class="p" data-group-id="9366906968-102">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">write_file</span><span class="p" data-group-id="9366906968-104">(</span><span class="n">StartErlDataFile</span><span class="p">,</span><span class="w"> </span><span class="n">StartErlData</span><span class="p" data-group-id="9366906968-104">)</span><span class="p">,</span><span class="w">
│ │ │ -
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-105">(</span><span class="s">&quot;Recreating tar file ~ts from contents in directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -	      </span><span class="p" data-group-id="9366906968-106">[</span><span class="n">TarFileName</span><span class="p">,</span><span class="n">TmpDir</span><span class="p" data-group-id="9366906968-106">]</span><span class="p" data-group-id="9366906968-105">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9366906968-107">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Tar</span><span class="p" data-group-id="9366906968-107">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="9366906968-108">(</span><span class="n">TarFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-109">[</span><span class="ss">write</span><span class="p">,</span><span class="w"> </span><span class="ss">compressed</span><span class="p" data-group-id="9366906968-109">]</span><span class="p" data-group-id="9366906968-108">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">TmpLogDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-93">(</span><span class="p" data-group-id="5165383622-94">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;log&quot;</span><span class="p" data-group-id="5165383622-94">]</span><span class="p" data-group-id="5165383622-93">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-95">(</span><span class="s">&quot;Creating temporary directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-96">[</span><span class="n">TmpLogDir</span><span class="p" data-group-id="5165383622-96">]</span><span class="p" data-group-id="5165383622-95">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="5165383622-97">(</span><span class="n">TmpLogDir</span><span class="p" data-group-id="5165383622-97">)</span><span class="p">,</span><span class="w">
│ │ │ +
│ │ │ +    </span><span class="n">StartErlDataFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-98">(</span><span class="p" data-group-id="5165383622-99">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl.data&quot;</span><span class="p" data-group-id="5165383622-99">]</span><span class="p" data-group-id="5165383622-98">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-100">(</span><span class="s">&quot;Creating ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-101">[</span><span class="n">StartErlDataFile</span><span class="p" data-group-id="5165383622-101">]</span><span class="p" data-group-id="5165383622-100">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">StartErlData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">io_lib</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-102">(</span><span class="s">&quot;</span><span class="si">~s</span><span class="s"> </span><span class="si">~s</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-103">[</span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="5165383622-103">]</span><span class="p" data-group-id="5165383622-102">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">write_file</span><span class="p" data-group-id="5165383622-104">(</span><span class="n">StartErlDataFile</span><span class="p">,</span><span class="w"> </span><span class="n">StartErlData</span><span class="p" data-group-id="5165383622-104">)</span><span class="p">,</span><span class="w">
│ │ │ +
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-105">(</span><span class="s">&quot;Recreating tar file ~ts from contents in directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +	      </span><span class="p" data-group-id="5165383622-106">[</span><span class="n">TarFileName</span><span class="p">,</span><span class="n">TmpDir</span><span class="p" data-group-id="5165383622-106">]</span><span class="p" data-group-id="5165383622-105">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5165383622-107">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Tar</span><span class="p" data-group-id="5165383622-107">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="5165383622-108">(</span><span class="n">TarFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-109">[</span><span class="ss">write</span><span class="p">,</span><span class="w"> </span><span class="ss">compressed</span><span class="p" data-group-id="5165383622-109">]</span><span class="p" data-group-id="5165383622-108">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="c1">%% {ok, Cwd} = file:get_cwd(),</span><span class="w">
│ │ │      </span><span class="c1">%% file:set_cwd(&quot;tmp&quot;),</span><span class="w">
│ │ │      </span><span class="n">ErtsDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="o">++</span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="9366906968-110">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-111">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="9366906968-111">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-112">[</span><span class="p" data-group-id="9366906968-112">]</span><span class="p" data-group-id="9366906968-110">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="9366906968-113">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-114">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="n">ErtsDir</span><span class="p" data-group-id="9366906968-114">)</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsDir</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-115">[</span><span class="p" data-group-id="9366906968-115">]</span><span class="p" data-group-id="9366906968-113">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="9366906968-116">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-117">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;releases&quot;</span><span class="p" data-group-id="9366906968-117">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-118">[</span><span class="p" data-group-id="9366906968-118">]</span><span class="p" data-group-id="9366906968-116">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="9366906968-119">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-120">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;lib&quot;</span><span class="p" data-group-id="9366906968-120">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;lib&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-121">[</span><span class="p" data-group-id="9366906968-121">]</span><span class="p" data-group-id="9366906968-119">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="9366906968-122">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-123">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;log&quot;</span><span class="p" data-group-id="9366906968-123">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;log&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-124">[</span><span class="p" data-group-id="9366906968-124">]</span><span class="p" data-group-id="9366906968-122">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="9366906968-125">(</span><span class="n">Tar</span><span class="p" data-group-id="9366906968-125">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="5165383622-110">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-111">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="5165383622-111">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-112">[</span><span class="p" data-group-id="5165383622-112">]</span><span class="p" data-group-id="5165383622-110">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="5165383622-113">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-114">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="n">ErtsDir</span><span class="p" data-group-id="5165383622-114">)</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsDir</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-115">[</span><span class="p" data-group-id="5165383622-115">]</span><span class="p" data-group-id="5165383622-113">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="5165383622-116">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-117">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;releases&quot;</span><span class="p" data-group-id="5165383622-117">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-118">[</span><span class="p" data-group-id="5165383622-118">]</span><span class="p" data-group-id="5165383622-116">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="5165383622-119">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-120">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;lib&quot;</span><span class="p" data-group-id="5165383622-120">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;lib&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-121">[</span><span class="p" data-group-id="5165383622-121">]</span><span class="p" data-group-id="5165383622-119">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="5165383622-122">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-123">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;log&quot;</span><span class="p" data-group-id="5165383622-123">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;log&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-124">[</span><span class="p" data-group-id="5165383622-124">]</span><span class="p" data-group-id="5165383622-122">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="5165383622-125">(</span><span class="n">Tar</span><span class="p" data-group-id="5165383622-125">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="c1">%% file:set_cwd(Cwd),</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-126">(</span><span class="s">&quot;Removing directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="9366906968-127">[</span><span class="n">TmpDir</span><span class="p" data-group-id="9366906968-127">]</span><span class="p" data-group-id="9366906968-126">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">remove_dir_tree</span><span class="p" data-group-id="9366906968-128">(</span><span class="n">TmpDir</span><span class="p" data-group-id="9366906968-128">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-126">(</span><span class="s">&quot;Removing directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="5165383622-127">[</span><span class="n">TmpDir</span><span class="p" data-group-id="5165383622-127">]</span><span class="p" data-group-id="5165383622-126">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">remove_dir_tree</span><span class="p" data-group-id="5165383622-128">(</span><span class="n">TmpDir</span><span class="p" data-group-id="5165383622-128">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  
│ │ │ -</span><span class="nf">install</span><span class="p" data-group-id="9366906968-129">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="9366906968-129">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">install</span><span class="p" data-group-id="5165383622-129">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="5165383622-129">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">TarFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.tar.gz&quot;</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-130">(</span><span class="s">&quot;Extracting ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-131">[</span><span class="n">TarFile</span><span class="p" data-group-id="9366906968-131">]</span><span class="p" data-group-id="9366906968-130">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">extract_tar</span><span class="p" data-group-id="9366906968-132">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="9366906968-132">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">StartErlDataFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-133">(</span><span class="p" data-group-id="9366906968-134">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl.data&quot;</span><span class="p" data-group-id="9366906968-134">]</span><span class="p" data-group-id="9366906968-133">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9366906968-135">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">StartErlData</span><span class="p" data-group-id="9366906968-135">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">read_txt_file</span><span class="p" data-group-id="9366906968-136">(</span><span class="n">StartErlDataFile</span><span class="p" data-group-id="9366906968-136">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9366906968-137">[</span><span class="n">ErlVsn</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">RelVsn</span><span class="p">|</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9366906968-137">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">string</span><span class="p">:</span><span class="nf">tokens</span><span class="p" data-group-id="9366906968-138">(</span><span class="n">StartErlData</span><span class="p">,</span><span class="w"> </span><span class="s">&quot; \n&quot;</span><span class="p" data-group-id="9366906968-138">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">ErtsBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-139">(</span><span class="p" data-group-id="9366906968-140">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">ErlVsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="9366906968-140">]</span><span class="p" data-group-id="9366906968-139">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">BinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-141">(</span><span class="p" data-group-id="9366906968-142">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="9366906968-142">]</span><span class="p" data-group-id="9366906968-141">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-143">(</span><span class="s">&quot;Substituting in erl.src, start.src and start_erl.src to &quot;</span><span class="w">
│ │ │ -              </span><span class="s">&quot;form erl, start and start_erl ...\n&quot;</span><span class="p" data-group-id="9366906968-143">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">subst_src_scripts</span><span class="p" data-group-id="9366906968-144">(</span><span class="p" data-group-id="9366906968-145">[</span><span class="s">&quot;erl&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl&quot;</span><span class="p" data-group-id="9366906968-145">]</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="n">BinDir</span><span class="p">,</span><span class="w">
│ │ │ -                      </span><span class="p" data-group-id="9366906968-146">[</span><span class="p" data-group-id="9366906968-147">{</span><span class="s">&quot;FINAL_ROOTDIR&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="9366906968-147">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-148">{</span><span class="s">&quot;EMU&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;beam&quot;</span><span class="p" data-group-id="9366906968-148">}</span><span class="p" data-group-id="9366906968-146">]</span><span class="p">,</span><span class="w">
│ │ │ -                      </span><span class="p" data-group-id="9366906968-149">[</span><span class="ss">preserve</span><span class="p" data-group-id="9366906968-149">]</span><span class="p" data-group-id="9366906968-144">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-130">(</span><span class="s">&quot;Extracting ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-131">[</span><span class="n">TarFile</span><span class="p" data-group-id="5165383622-131">]</span><span class="p" data-group-id="5165383622-130">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">extract_tar</span><span class="p" data-group-id="5165383622-132">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="5165383622-132">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">StartErlDataFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-133">(</span><span class="p" data-group-id="5165383622-134">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl.data&quot;</span><span class="p" data-group-id="5165383622-134">]</span><span class="p" data-group-id="5165383622-133">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5165383622-135">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">StartErlData</span><span class="p" data-group-id="5165383622-135">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">read_txt_file</span><span class="p" data-group-id="5165383622-136">(</span><span class="n">StartErlDataFile</span><span class="p" data-group-id="5165383622-136">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5165383622-137">[</span><span class="n">ErlVsn</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">RelVsn</span><span class="p">|</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="5165383622-137">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">string</span><span class="p">:</span><span class="nf">tokens</span><span class="p" data-group-id="5165383622-138">(</span><span class="n">StartErlData</span><span class="p">,</span><span class="w"> </span><span class="s">&quot; \n&quot;</span><span class="p" data-group-id="5165383622-138">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">ErtsBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-139">(</span><span class="p" data-group-id="5165383622-140">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">ErlVsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="5165383622-140">]</span><span class="p" data-group-id="5165383622-139">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">BinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-141">(</span><span class="p" data-group-id="5165383622-142">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="5165383622-142">]</span><span class="p" data-group-id="5165383622-141">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-143">(</span><span class="s">&quot;Substituting in erl.src, start.src and start_erl.src to &quot;</span><span class="w">
│ │ │ +              </span><span class="s">&quot;form erl, start and start_erl ...\n&quot;</span><span class="p" data-group-id="5165383622-143">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">subst_src_scripts</span><span class="p" data-group-id="5165383622-144">(</span><span class="p" data-group-id="5165383622-145">[</span><span class="s">&quot;erl&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl&quot;</span><span class="p" data-group-id="5165383622-145">]</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="n">BinDir</span><span class="p">,</span><span class="w">
│ │ │ +                      </span><span class="p" data-group-id="5165383622-146">[</span><span class="p" data-group-id="5165383622-147">{</span><span class="s">&quot;FINAL_ROOTDIR&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="5165383622-147">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-148">{</span><span class="s">&quot;EMU&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;beam&quot;</span><span class="p" data-group-id="5165383622-148">}</span><span class="p" data-group-id="5165383622-146">]</span><span class="p">,</span><span class="w">
│ │ │ +                      </span><span class="p" data-group-id="5165383622-149">[</span><span class="ss">preserve</span><span class="p" data-group-id="5165383622-149">]</span><span class="p" data-group-id="5165383622-144">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="c1">%%! Workaround for pre OTP 17.0: start.src and start_erl.src did</span><span class="w">
│ │ │      </span><span class="c1">%%! not have correct permissions, so the above &#39;preserve&#39; option did not help</span><span class="w">
│ │ │ -    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">change_mode</span><span class="p" data-group-id="9366906968-150">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-151">(</span><span class="n">BinDir</span><span class="p">,</span><span class="s">&quot;start&quot;</span><span class="p" data-group-id="9366906968-151">)</span><span class="p">,</span><span class="mi">8#0755</span><span class="p" data-group-id="9366906968-150">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">change_mode</span><span class="p" data-group-id="9366906968-152">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-153">(</span><span class="n">BinDir</span><span class="p">,</span><span class="s">&quot;start_erl&quot;</span><span class="p" data-group-id="9366906968-153">)</span><span class="p">,</span><span class="mi">8#0755</span><span class="p" data-group-id="9366906968-152">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">change_mode</span><span class="p" data-group-id="5165383622-150">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-151">(</span><span class="n">BinDir</span><span class="p">,</span><span class="s">&quot;start&quot;</span><span class="p" data-group-id="5165383622-151">)</span><span class="p">,</span><span class="mi">8#0755</span><span class="p" data-group-id="5165383622-150">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">change_mode</span><span class="p" data-group-id="5165383622-152">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-153">(</span><span class="n">BinDir</span><span class="p">,</span><span class="s">&quot;start_erl&quot;</span><span class="p" data-group-id="5165383622-153">)</span><span class="p">,</span><span class="mi">8#0755</span><span class="p" data-group-id="5165383622-152">)</span><span class="p">,</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="9366906968-154">(</span><span class="s">&quot;Creating the RELEASES file ...\n&quot;</span><span class="p" data-group-id="9366906968-154">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">create_RELEASES</span><span class="p" data-group-id="9366906968-155">(</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-156">(</span><span class="p" data-group-id="9366906968-157">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w">
│ │ │ -					    </span><span class="nc">filename</span><span class="p">:</span><span class="nf">basename</span><span class="p" data-group-id="9366906968-158">(</span><span class="n">RelFileName</span><span class="p" data-group-id="9366906968-158">)</span><span class="p" data-group-id="9366906968-157">]</span><span class="p" data-group-id="9366906968-156">)</span><span class="p" data-group-id="9366906968-155">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="5165383622-154">(</span><span class="s">&quot;Creating the RELEASES file ...\n&quot;</span><span class="p" data-group-id="5165383622-154">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">create_RELEASES</span><span class="p" data-group-id="5165383622-155">(</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-156">(</span><span class="p" data-group-id="5165383622-157">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w">
│ │ │ +					    </span><span class="nc">filename</span><span class="p">:</span><span class="nf">basename</span><span class="p" data-group-id="5165383622-158">(</span><span class="n">RelFileName</span><span class="p" data-group-id="5165383622-158">)</span><span class="p" data-group-id="5165383622-157">]</span><span class="p" data-group-id="5165383622-156">)</span><span class="p" data-group-id="5165383622-155">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% LOCALS</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% make_script(RelFileName,Opts)</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ -</span><span class="nf">make_script</span><span class="p" data-group-id="9366906968-159">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">Opts</span><span class="p" data-group-id="9366906968-159">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="9366906968-160">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-161">[</span><span class="ss">no_module_tests</span><span class="p">,</span><span class="w">
│ │ │ -				       </span><span class="p" data-group-id="9366906968-162">{</span><span class="ss">outdir</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="9366906968-163">(</span><span class="n">RelFileName</span><span class="p" data-group-id="9366906968-163">)</span><span class="p" data-group-id="9366906968-162">}</span><span class="w">
│ │ │ -				       </span><span class="p">|</span><span class="n">Opts</span><span class="p" data-group-id="9366906968-161">]</span><span class="p" data-group-id="9366906968-160">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">make_script</span><span class="p" data-group-id="5165383622-159">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">Opts</span><span class="p" data-group-id="5165383622-159">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="5165383622-160">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-161">[</span><span class="ss">no_module_tests</span><span class="p">,</span><span class="w">
│ │ │ +				       </span><span class="p" data-group-id="5165383622-162">{</span><span class="ss">outdir</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="5165383622-163">(</span><span class="n">RelFileName</span><span class="p" data-group-id="5165383622-163">)</span><span class="p" data-group-id="5165383622-162">}</span><span class="w">
│ │ │ +				       </span><span class="p">|</span><span class="n">Opts</span><span class="p" data-group-id="5165383622-161">]</span><span class="p" data-group-id="5165383622-160">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% make_tar(RelFileName,Opts)</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ -</span><span class="nf">make_tar</span><span class="p" data-group-id="9366906968-164">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">Opts</span><span class="p" data-group-id="9366906968-164">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">RootDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">code</span><span class="p">:</span><span class="nf">root_dir</span><span class="p" data-group-id="9366906968-165">(</span><span class="p" data-group-id="9366906968-165">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="9366906968-166">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-167">[</span><span class="p" data-group-id="9366906968-168">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="9366906968-168">}</span><span class="p">,</span><span class="w">
│ │ │ -				    </span><span class="p" data-group-id="9366906968-169">{</span><span class="ss">outdir</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="9366906968-170">(</span><span class="n">RelFileName</span><span class="p" data-group-id="9366906968-170">)</span><span class="p" data-group-id="9366906968-169">}</span><span class="w">
│ │ │ -				    </span><span class="p">|</span><span class="n">Opts</span><span class="p" data-group-id="9366906968-167">]</span><span class="p" data-group-id="9366906968-166">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">make_tar</span><span class="p" data-group-id="5165383622-164">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">Opts</span><span class="p" data-group-id="5165383622-164">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">RootDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">code</span><span class="p">:</span><span class="nf">root_dir</span><span class="p" data-group-id="5165383622-165">(</span><span class="p" data-group-id="5165383622-165">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="5165383622-166">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-167">[</span><span class="p" data-group-id="5165383622-168">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="5165383622-168">}</span><span class="p">,</span><span class="w">
│ │ │ +				    </span><span class="p" data-group-id="5165383622-169">{</span><span class="ss">outdir</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="5165383622-170">(</span><span class="n">RelFileName</span><span class="p" data-group-id="5165383622-170">)</span><span class="p" data-group-id="5165383622-169">}</span><span class="w">
│ │ │ +				    </span><span class="p">|</span><span class="n">Opts</span><span class="p" data-group-id="5165383622-167">]</span><span class="p" data-group-id="5165383622-166">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% extract_tar(TarFile, DestDir)</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ -</span><span class="nf">extract_tar</span><span class="p" data-group-id="9366906968-171">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p" data-group-id="9366906968-171">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">extract</span><span class="p" data-group-id="9366906968-172">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-173">[</span><span class="p" data-group-id="9366906968-174">{</span><span class="ss">cwd</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p" data-group-id="9366906968-174">}</span><span class="p">,</span><span class="w"> </span><span class="ss">compressed</span><span class="p" data-group-id="9366906968-173">]</span><span class="p" data-group-id="9366906968-172">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">extract_tar</span><span class="p" data-group-id="5165383622-171">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p" data-group-id="5165383622-171">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">extract</span><span class="p" data-group-id="5165383622-172">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-173">[</span><span class="p" data-group-id="5165383622-174">{</span><span class="ss">cwd</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p" data-group-id="5165383622-174">}</span><span class="p">,</span><span class="w"> </span><span class="ss">compressed</span><span class="p" data-group-id="5165383622-173">]</span><span class="p" data-group-id="5165383622-172">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">create_RELEASES</span><span class="p" data-group-id="9366906968-175">(</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="p" data-group-id="9366906968-175">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">create_RELEASES</span><span class="p" data-group-id="9366906968-176">(</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.rel&quot;</span><span class="p" data-group-id="9366906968-176">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">create_RELEASES</span><span class="p" data-group-id="5165383622-175">(</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="p" data-group-id="5165383622-175">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">create_RELEASES</span><span class="p" data-group-id="5165383622-176">(</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.rel&quot;</span><span class="p" data-group-id="5165383622-176">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">subst_src_scripts</span><span class="p" data-group-id="9366906968-177">(</span><span class="n">Scripts</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="9366906968-177">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="9366906968-178">(</span><span class="nf">fun</span><span class="p" data-group-id="9366906968-179">(</span><span class="n">Script</span><span class="p" data-group-id="9366906968-179">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                          </span><span class="nf">subst_src_script</span><span class="p" data-group-id="9366906968-180">(</span><span class="n">Script</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w">
│ │ │ -                                           </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="9366906968-180">)</span><span class="w">
│ │ │ -                  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Scripts</span><span class="p" data-group-id="9366906968-178">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">subst_src_script</span><span class="p" data-group-id="9366906968-181">(</span><span class="n">Script</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="9366906968-181">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">subst_file</span><span class="p" data-group-id="9366906968-182">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-183">(</span><span class="p" data-group-id="9366906968-184">[</span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">Script</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.src&quot;</span><span class="p" data-group-id="9366906968-184">]</span><span class="p" data-group-id="9366906968-183">)</span><span class="p">,</span><span class="w">
│ │ │ -               </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-185">(</span><span class="p" data-group-id="9366906968-186">[</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Script</span><span class="p" data-group-id="9366906968-186">]</span><span class="p" data-group-id="9366906968-185">)</span><span class="p">,</span><span class="w">
│ │ │ -               </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="9366906968-182">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">subst_file</span><span class="p" data-group-id="9366906968-187">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="9366906968-187">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9366906968-188">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Conts</span><span class="p" data-group-id="9366906968-188">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">read_txt_file</span><span class="p" data-group-id="9366906968-189">(</span><span class="n">Src</span><span class="p" data-group-id="9366906968-189">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">NConts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">subst</span><span class="p" data-group-id="9366906968-190">(</span><span class="n">Conts</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="9366906968-190">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">write_file</span><span class="p" data-group-id="9366906968-191">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">NConts</span><span class="p" data-group-id="9366906968-191">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="9366906968-192">(</span><span class="ss">preserve</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="9366906968-192">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">subst_src_scripts</span><span class="p" data-group-id="5165383622-177">(</span><span class="n">Scripts</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="5165383622-177">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="5165383622-178">(</span><span class="nf">fun</span><span class="p" data-group-id="5165383622-179">(</span><span class="n">Script</span><span class="p" data-group-id="5165383622-179">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                          </span><span class="nf">subst_src_script</span><span class="p" data-group-id="5165383622-180">(</span><span class="n">Script</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w">
│ │ │ +                                           </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="5165383622-180">)</span><span class="w">
│ │ │ +                  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Scripts</span><span class="p" data-group-id="5165383622-178">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">subst_src_script</span><span class="p" data-group-id="5165383622-181">(</span><span class="n">Script</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="5165383622-181">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">subst_file</span><span class="p" data-group-id="5165383622-182">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-183">(</span><span class="p" data-group-id="5165383622-184">[</span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">Script</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.src&quot;</span><span class="p" data-group-id="5165383622-184">]</span><span class="p" data-group-id="5165383622-183">)</span><span class="p">,</span><span class="w">
│ │ │ +               </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-185">(</span><span class="p" data-group-id="5165383622-186">[</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Script</span><span class="p" data-group-id="5165383622-186">]</span><span class="p" data-group-id="5165383622-185">)</span><span class="p">,</span><span class="w">
│ │ │ +               </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="5165383622-182">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">subst_file</span><span class="p" data-group-id="5165383622-187">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="5165383622-187">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5165383622-188">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Conts</span><span class="p" data-group-id="5165383622-188">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">read_txt_file</span><span class="p" data-group-id="5165383622-189">(</span><span class="n">Src</span><span class="p" data-group-id="5165383622-189">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">NConts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">subst</span><span class="p" data-group-id="5165383622-190">(</span><span class="n">Conts</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="5165383622-190">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">write_file</span><span class="p" data-group-id="5165383622-191">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">NConts</span><span class="p" data-group-id="5165383622-191">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="5165383622-192">(</span><span class="ss">preserve</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="5165383622-192">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="9366906968-193">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="9366906968-193">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file_info</span><span class="p" data-group-id="9366906968-194">(</span><span class="n">Src</span><span class="p" data-group-id="9366906968-194">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nc">file</span><span class="p">:</span><span class="nf">write_file_info</span><span class="p" data-group-id="9366906968-195">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="9366906968-195">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="5165383622-193">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="5165383622-193">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file_info</span><span class="p" data-group-id="5165383622-194">(</span><span class="n">Src</span><span class="p" data-group-id="5165383622-194">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">file</span><span class="p">:</span><span class="nf">write_file_info</span><span class="p" data-group-id="5165383622-195">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="5165383622-195">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">ok</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% subst(Str, Vars)</span><span class="w">
│ │ │  </span><span class="c1">%% Vars = [{Var, Val}]</span><span class="w">
│ │ │  </span><span class="c1">%% Var = Val = string()</span><span class="w">
│ │ │  </span><span class="c1">%% Substitute all occurrences of %Var% for Val in Str, using the list</span><span class="w">
│ │ │  </span><span class="c1">%% of variables in Vars.</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="9366906968-196">(</span><span class="n">Str</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="9366906968-196">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">subst</span><span class="p" data-group-id="9366906968-197">(</span><span class="n">Str</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-198">[</span><span class="p" data-group-id="9366906968-198">]</span><span class="p" data-group-id="9366906968-197">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="5165383622-196">(</span><span class="n">Str</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="5165383622-196">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">subst</span><span class="p" data-group-id="5165383622-197">(</span><span class="n">Str</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-198">[</span><span class="p" data-group-id="5165383622-198">]</span><span class="p" data-group-id="5165383622-197">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="9366906968-199">(</span><span class="p" data-group-id="9366906968-200">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9366906968-200">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="9366906968-199">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$A</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$Z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">subst_var</span><span class="p" data-group-id="9366906968-201">(</span><span class="p" data-group-id="9366906968-202">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9366906968-202">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-203">[</span><span class="p" data-group-id="9366906968-203">]</span><span class="p" data-group-id="9366906968-201">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="9366906968-204">(</span><span class="p" data-group-id="9366906968-205">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9366906968-205">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="9366906968-204">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$a</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">subst_var</span><span class="p" data-group-id="9366906968-206">(</span><span class="p" data-group-id="9366906968-207">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9366906968-207">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-208">[</span><span class="p" data-group-id="9366906968-208">]</span><span class="p" data-group-id="9366906968-206">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="9366906968-209">(</span><span class="p" data-group-id="9366906968-210">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9366906968-210">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="9366906968-209">)</span><span class="w"> </span><span class="k">when</span><span class="w">  </span><span class="n">C</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="sc">$_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">subst_var</span><span class="p" data-group-id="9366906968-211">(</span><span class="p" data-group-id="9366906968-212">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9366906968-212">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-213">[</span><span class="p" data-group-id="9366906968-213">]</span><span class="p" data-group-id="9366906968-211">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="9366906968-214">(</span><span class="p" data-group-id="9366906968-215">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9366906968-215">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="9366906968-214">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">subst</span><span class="p" data-group-id="9366906968-216">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-217">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="9366906968-217">]</span><span class="p" data-group-id="9366906968-216">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="9366906968-218">(</span><span class="p" data-group-id="9366906968-219">[</span><span class="p" data-group-id="9366906968-219">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="9366906968-218">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="9366906968-220">(</span><span class="n">Result</span><span class="p" data-group-id="9366906968-220">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">subst_var</span><span class="p" data-group-id="9366906968-221">(</span><span class="p" data-group-id="9366906968-222">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9366906968-222">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="9366906968-221">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Key</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="9366906968-223">(</span><span class="n">VarAcc</span><span class="p" data-group-id="9366906968-223">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="9366906968-224">(</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="9366906968-224">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9366906968-225">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-226">{</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="9366906968-226">}</span><span class="p" data-group-id="9366906968-225">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">subst</span><span class="p" data-group-id="9366906968-227">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="9366906968-228">(</span><span class="n">Value</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="9366906968-228">)</span><span class="p" data-group-id="9366906968-227">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="5165383622-199">(</span><span class="p" data-group-id="5165383622-200">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5165383622-200">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5165383622-199">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$A</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$Z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">subst_var</span><span class="p" data-group-id="5165383622-201">(</span><span class="p" data-group-id="5165383622-202">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5165383622-202">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-203">[</span><span class="p" data-group-id="5165383622-203">]</span><span class="p" data-group-id="5165383622-201">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="5165383622-204">(</span><span class="p" data-group-id="5165383622-205">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5165383622-205">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5165383622-204">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$a</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">subst_var</span><span class="p" data-group-id="5165383622-206">(</span><span class="p" data-group-id="5165383622-207">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5165383622-207">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-208">[</span><span class="p" data-group-id="5165383622-208">]</span><span class="p" data-group-id="5165383622-206">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="5165383622-209">(</span><span class="p" data-group-id="5165383622-210">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5165383622-210">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5165383622-209">)</span><span class="w"> </span><span class="k">when</span><span class="w">  </span><span class="n">C</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="sc">$_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">subst_var</span><span class="p" data-group-id="5165383622-211">(</span><span class="p" data-group-id="5165383622-212">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5165383622-212">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-213">[</span><span class="p" data-group-id="5165383622-213">]</span><span class="p" data-group-id="5165383622-211">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="5165383622-214">(</span><span class="p" data-group-id="5165383622-215">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5165383622-215">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5165383622-214">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">subst</span><span class="p" data-group-id="5165383622-216">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-217">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5165383622-217">]</span><span class="p" data-group-id="5165383622-216">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="5165383622-218">(</span><span class="p" data-group-id="5165383622-219">[</span><span class="p" data-group-id="5165383622-219">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5165383622-218">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="5165383622-220">(</span><span class="n">Result</span><span class="p" data-group-id="5165383622-220">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">subst_var</span><span class="p" data-group-id="5165383622-221">(</span><span class="p" data-group-id="5165383622-222">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5165383622-222">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="5165383622-221">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Key</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="5165383622-223">(</span><span class="n">VarAcc</span><span class="p" data-group-id="5165383622-223">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="5165383622-224">(</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="5165383622-224">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="5165383622-225">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-226">{</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="5165383622-226">}</span><span class="p" data-group-id="5165383622-225">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">subst</span><span class="p" data-group-id="5165383622-227">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="5165383622-228">(</span><span class="n">Value</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5165383622-228">)</span><span class="p" data-group-id="5165383622-227">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">subst</span><span class="p" data-group-id="9366906968-229">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-230">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">VarAcc</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="9366906968-231">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="9366906968-231">]</span><span class="p" data-group-id="9366906968-230">]</span><span class="p" data-group-id="9366906968-229">)</span><span class="w">
│ │ │ +            </span><span class="nf">subst</span><span class="p" data-group-id="5165383622-229">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-230">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">VarAcc</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="5165383622-231">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5165383622-231">]</span><span class="p" data-group-id="5165383622-230">]</span><span class="p" data-group-id="5165383622-229">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">subst_var</span><span class="p" data-group-id="9366906968-232">(</span><span class="p" data-group-id="9366906968-233">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9366906968-233">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="9366906968-232">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">subst_var</span><span class="p" data-group-id="9366906968-234">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-235">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="9366906968-235">]</span><span class="p" data-group-id="9366906968-234">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">subst_var</span><span class="p" data-group-id="9366906968-236">(</span><span class="p" data-group-id="9366906968-237">[</span><span class="p" data-group-id="9366906968-237">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="9366906968-236">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">subst</span><span class="p" data-group-id="9366906968-238">(</span><span class="p" data-group-id="9366906968-239">[</span><span class="p" data-group-id="9366906968-239">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-240">[</span><span class="n">VarAcc</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="9366906968-241">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="9366906968-241">]</span><span class="p" data-group-id="9366906968-240">]</span><span class="p" data-group-id="9366906968-238">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">copy_file</span><span class="p" data-group-id="9366906968-242">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p" data-group-id="9366906968-242">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="9366906968-243">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-244">[</span><span class="p" data-group-id="9366906968-244">]</span><span class="p" data-group-id="9366906968-243">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">copy_file</span><span class="p" data-group-id="9366906968-245">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="9366906968-245">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9366906968-246">{</span><span class="ss">ok</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9366906968-246">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">copy</span><span class="p" data-group-id="9366906968-247">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p" data-group-id="9366906968-247">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="9366906968-248">(</span><span class="ss">preserve</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="9366906968-248">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">subst_var</span><span class="p" data-group-id="5165383622-232">(</span><span class="p" data-group-id="5165383622-233">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5165383622-233">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="5165383622-232">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">subst_var</span><span class="p" data-group-id="5165383622-234">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-235">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="5165383622-235">]</span><span class="p" data-group-id="5165383622-234">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">subst_var</span><span class="p" data-group-id="5165383622-236">(</span><span class="p" data-group-id="5165383622-237">[</span><span class="p" data-group-id="5165383622-237">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="5165383622-236">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">subst</span><span class="p" data-group-id="5165383622-238">(</span><span class="p" data-group-id="5165383622-239">[</span><span class="p" data-group-id="5165383622-239">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-240">[</span><span class="n">VarAcc</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="5165383622-241">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5165383622-241">]</span><span class="p" data-group-id="5165383622-240">]</span><span class="p" data-group-id="5165383622-238">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">copy_file</span><span class="p" data-group-id="5165383622-242">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p" data-group-id="5165383622-242">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="5165383622-243">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-244">[</span><span class="p" data-group-id="5165383622-244">]</span><span class="p" data-group-id="5165383622-243">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">copy_file</span><span class="p" data-group-id="5165383622-245">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="5165383622-245">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5165383622-246">{</span><span class="ss">ok</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5165383622-246">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">copy</span><span class="p" data-group-id="5165383622-247">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p" data-group-id="5165383622-247">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="5165383622-248">(</span><span class="ss">preserve</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="5165383622-248">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="9366906968-249">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="9366906968-249">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file_info</span><span class="p" data-group-id="9366906968-250">(</span><span class="n">Src</span><span class="p" data-group-id="9366906968-250">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nc">file</span><span class="p">:</span><span class="nf">write_file_info</span><span class="p" data-group-id="9366906968-251">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="9366906968-251">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="5165383622-249">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="5165383622-249">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file_info</span><span class="p" data-group-id="5165383622-250">(</span><span class="n">Src</span><span class="p" data-group-id="5165383622-250">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">file</span><span class="p">:</span><span class="nf">write_file_info</span><span class="p" data-group-id="5165383622-251">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="5165383622-251">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">ok</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">write_file</span><span class="p" data-group-id="9366906968-252">(</span><span class="n">FName</span><span class="p">,</span><span class="w"> </span><span class="n">Conts</span><span class="p" data-group-id="9366906968-252">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Enc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">native_name_encoding</span><span class="p" data-group-id="9366906968-253">(</span><span class="p" data-group-id="9366906968-253">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9366906968-254">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="9366906968-254">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="9366906968-255">(</span><span class="n">FName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-256">[</span><span class="ss">write</span><span class="p" data-group-id="9366906968-256">]</span><span class="p" data-group-id="9366906968-255">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">write</span><span class="p" data-group-id="9366906968-257">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="nc">unicode</span><span class="p">:</span><span class="nf">characters_to_binary</span><span class="p" data-group-id="9366906968-258">(</span><span class="n">Conts</span><span class="p">,</span><span class="n">Enc</span><span class="p">,</span><span class="n">Enc</span><span class="p" data-group-id="9366906968-258">)</span><span class="p" data-group-id="9366906968-257">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="9366906968-259">(</span><span class="n">Fd</span><span class="p" data-group-id="9366906968-259">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">read_txt_file</span><span class="p" data-group-id="9366906968-260">(</span><span class="n">File</span><span class="p" data-group-id="9366906968-260">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9366906968-261">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Bin</span><span class="p" data-group-id="9366906968-261">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file</span><span class="p" data-group-id="9366906968-262">(</span><span class="n">File</span><span class="p" data-group-id="9366906968-262">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9366906968-263">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_list</span><span class="p" data-group-id="9366906968-264">(</span><span class="n">Bin</span><span class="p" data-group-id="9366906968-264">)</span><span class="p" data-group-id="9366906968-263">}</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">remove_dir_tree</span><span class="p" data-group-id="9366906968-265">(</span><span class="n">Dir</span><span class="p" data-group-id="9366906968-265">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">remove_all_files</span><span class="p" data-group-id="9366906968-266">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9366906968-267">[</span><span class="n">Dir</span><span class="p" data-group-id="9366906968-267">]</span><span class="p" data-group-id="9366906968-266">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">remove_all_files</span><span class="p" data-group-id="9366906968-268">(</span><span class="n">Dir</span><span class="p">,</span><span class="w"> </span><span class="n">Files</span><span class="p" data-group-id="9366906968-268">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="9366906968-269">(</span><span class="nf">fun</span><span class="p" data-group-id="9366906968-270">(</span><span class="n">File</span><span class="p" data-group-id="9366906968-270">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                          </span><span class="n">FilePath</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9366906968-271">(</span><span class="p" data-group-id="9366906968-272">[</span><span class="n">Dir</span><span class="p">,</span><span class="w"> </span><span class="n">File</span><span class="p" data-group-id="9366906968-272">]</span><span class="p" data-group-id="9366906968-271">)</span><span class="p">,</span><span class="w">
│ │ │ -                          </span><span class="k">case</span><span class="w"> </span><span class="nc">filelib</span><span class="p">:</span><span class="nf">is_dir</span><span class="p" data-group-id="9366906968-273">(</span><span class="n">FilePath</span><span class="p" data-group-id="9366906968-273">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">write_file</span><span class="p" data-group-id="5165383622-252">(</span><span class="n">FName</span><span class="p">,</span><span class="w"> </span><span class="n">Conts</span><span class="p" data-group-id="5165383622-252">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Enc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">native_name_encoding</span><span class="p" data-group-id="5165383622-253">(</span><span class="p" data-group-id="5165383622-253">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5165383622-254">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="5165383622-254">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="5165383622-255">(</span><span class="n">FName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-256">[</span><span class="ss">write</span><span class="p" data-group-id="5165383622-256">]</span><span class="p" data-group-id="5165383622-255">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">write</span><span class="p" data-group-id="5165383622-257">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="nc">unicode</span><span class="p">:</span><span class="nf">characters_to_binary</span><span class="p" data-group-id="5165383622-258">(</span><span class="n">Conts</span><span class="p">,</span><span class="n">Enc</span><span class="p">,</span><span class="n">Enc</span><span class="p" data-group-id="5165383622-258">)</span><span class="p" data-group-id="5165383622-257">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="5165383622-259">(</span><span class="n">Fd</span><span class="p" data-group-id="5165383622-259">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">read_txt_file</span><span class="p" data-group-id="5165383622-260">(</span><span class="n">File</span><span class="p" data-group-id="5165383622-260">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5165383622-261">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Bin</span><span class="p" data-group-id="5165383622-261">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file</span><span class="p" data-group-id="5165383622-262">(</span><span class="n">File</span><span class="p" data-group-id="5165383622-262">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5165383622-263">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_list</span><span class="p" data-group-id="5165383622-264">(</span><span class="n">Bin</span><span class="p" data-group-id="5165383622-264">)</span><span class="p" data-group-id="5165383622-263">}</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">remove_dir_tree</span><span class="p" data-group-id="5165383622-265">(</span><span class="n">Dir</span><span class="p" data-group-id="5165383622-265">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">remove_all_files</span><span class="p" data-group-id="5165383622-266">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5165383622-267">[</span><span class="n">Dir</span><span class="p" data-group-id="5165383622-267">]</span><span class="p" data-group-id="5165383622-266">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">remove_all_files</span><span class="p" data-group-id="5165383622-268">(</span><span class="n">Dir</span><span class="p">,</span><span class="w"> </span><span class="n">Files</span><span class="p" data-group-id="5165383622-268">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="5165383622-269">(</span><span class="nf">fun</span><span class="p" data-group-id="5165383622-270">(</span><span class="n">File</span><span class="p" data-group-id="5165383622-270">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                          </span><span class="n">FilePath</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="5165383622-271">(</span><span class="p" data-group-id="5165383622-272">[</span><span class="n">Dir</span><span class="p">,</span><span class="w"> </span><span class="n">File</span><span class="p" data-group-id="5165383622-272">]</span><span class="p" data-group-id="5165383622-271">)</span><span class="p">,</span><span class="w">
│ │ │ +                          </span><span class="k">case</span><span class="w"> </span><span class="nc">filelib</span><span class="p">:</span><span class="nf">is_dir</span><span class="p" data-group-id="5165383622-273">(</span><span class="n">FilePath</span><span class="p" data-group-id="5165383622-273">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │                                </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                                  </span><span class="p" data-group-id="9366906968-274">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">DirFiles</span><span class="p" data-group-id="9366906968-274">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">list_dir</span><span class="p" data-group-id="9366906968-275">(</span><span class="n">FilePath</span><span class="p" data-group-id="9366906968-275">)</span><span class="p">,</span><span class="w">
│ │ │ -                                  </span><span class="nf">remove_all_files</span><span class="p" data-group-id="9366906968-276">(</span><span class="n">FilePath</span><span class="p">,</span><span class="w"> </span><span class="n">DirFiles</span><span class="p" data-group-id="9366906968-276">)</span><span class="p">,</span><span class="w">
│ │ │ -                                  </span><span class="nc">file</span><span class="p">:</span><span class="nf">del_dir</span><span class="p" data-group-id="9366906968-277">(</span><span class="n">FilePath</span><span class="p" data-group-id="9366906968-277">)</span><span class="p">;</span><span class="w">
│ │ │ +                                  </span><span class="p" data-group-id="5165383622-274">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">DirFiles</span><span class="p" data-group-id="5165383622-274">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">list_dir</span><span class="p" data-group-id="5165383622-275">(</span><span class="n">FilePath</span><span class="p" data-group-id="5165383622-275">)</span><span class="p">,</span><span class="w">
│ │ │ +                                  </span><span class="nf">remove_all_files</span><span class="p" data-group-id="5165383622-276">(</span><span class="n">FilePath</span><span class="p">,</span><span class="w"> </span><span class="n">DirFiles</span><span class="p" data-group-id="5165383622-276">)</span><span class="p">,</span><span class="w">
│ │ │ +                                  </span><span class="nc">file</span><span class="p">:</span><span class="nf">del_dir</span><span class="p" data-group-id="5165383622-277">(</span><span class="n">FilePath</span><span class="p" data-group-id="5165383622-277">)</span><span class="p">;</span><span class="w">
│ │ │                                </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                                  </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="9366906968-278">(</span><span class="n">FilePath</span><span class="p" data-group-id="9366906968-278">)</span><span class="w">
│ │ │ +                                  </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="5165383622-278">(</span><span class="n">FilePath</span><span class="p" data-group-id="5165383622-278">)</span><span class="w">
│ │ │                            </span><span class="k">end</span><span class="w">
│ │ │ -                  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Files</span><span class="p" data-group-id="9366906968-269">)</span><span class="p">.</span></code></pre>
│ │ │ +                  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Files</span><span class="p" data-group-id="5165383622-269">)</span><span class="p">.</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="error_logging.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/data_types.html
│ │ │ @@ -199,18 +199,18 @@
│ │ │    </a>
│ │ │    <span class="text">Representation of Floating-Point Numbers</span>
│ │ │  </h3>
│ │ │  <p>When working with floats, you may not see what you expect when printing or doing
│ │ │  arithmetic operations. This is because floats are represented by a fixed number
│ │ │  of bits in a base-2 system while printed floats are represented with a base-10
│ │ │  system. Erlang uses 64-bit floats. Here are examples of this phenomenon:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="mf">0.1</span><span class="o">+</span><span class="mf">0.2</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mf">0.30000000000000004</span></code></pre><p>The real numbers <code class="inline">0.1</code> and <code class="inline">0.2</code> cannot be represented exactly as floats.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3807618092-1">{</span><span class="mf">36028797018963968.0</span><span class="p">,</span><span class="w"> </span><span class="mi">36028797018963968</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mf">36028797018963968.0</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="mf">36028797018963970.0</span><span class="p">,</span><span class="w"> </span><span class="mi">36028797018963970</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mf">36028797018963970.0</span><span class="p" data-group-id="3807618092-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3807618092-2">{</span><span class="mf">3.602879701896397e16</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="mf">3.602879701896397e16</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="3807618092-2">}</span><span class="p">.</span></code></pre><p>The value <code class="inline">36028797018963968</code> can be represented exactly as a float value but
│ │ │ +</span><span class="mf">0.30000000000000004</span></code></pre><p>The real numbers <code class="inline">0.1</code> and <code class="inline">0.2</code> cannot be represented exactly as floats.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8312542819-1">{</span><span class="mf">36028797018963968.0</span><span class="p">,</span><span class="w"> </span><span class="mi">36028797018963968</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mf">36028797018963968.0</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="mf">36028797018963970.0</span><span class="p">,</span><span class="w"> </span><span class="mi">36028797018963970</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mf">36028797018963970.0</span><span class="p" data-group-id="8312542819-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8312542819-2">{</span><span class="mf">3.602879701896397e16</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="mf">3.602879701896397e16</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="8312542819-2">}</span><span class="p">.</span></code></pre><p>The value <code class="inline">36028797018963968</code> can be represented exactly as a float value but
│ │ │  Erlang's pretty printer rounds <code class="inline">36028797018963968.0</code> to <code class="inline">3.602879701896397e16</code>
│ │ │  (<code class="inline">=36028797018963970.0</code>) as all values in the range
│ │ │  <code class="inline">[36028797018963966.0, 36028797018963972.0]</code> are represented by
│ │ │  <code class="inline">36028797018963968.0</code>.</p><p>For more information about floats and issues with them, see:</p><ul><li><a href="https://floating-point-gui.de/">What Every Programmer Should Know About Floating-Point Arithmetic</a></li><li><a href="https://0.30000000000000004.com/">0.30000000000000004.com/</a></li><li><a href="https://docs.python.org/3/tutorial/floatingpoint.html">Floating Point Arithmetic: Issues and Limitations</a></li></ul><p>If you need to work with exact decimal fractions, for instance to represent
│ │ │  money, it is recommended to use a library that handles that, or work in
│ │ │  cents instead of dollars or euros so that decimal fractions are not needed.</p><p>Also note that Erlang's floats do not exactly match IEEE 754 floats,
│ │ │  in that neither <em>Inf</em> nor <em>NaN</em> are supported in Erlang. Any
│ │ │ @@ -244,52 +244,52 @@
│ │ │  by eight are called <em>binaries</em>.</p><p><em>Examples:</em></p><pre><code class="text">1&gt; &lt;&lt;10,20&gt;&gt;.
│ │ │  &lt;&lt;10,20&gt;&gt;
│ │ │  2&gt; &lt;&lt;&quot;ABC&quot;&gt;&gt;.
│ │ │  &lt;&lt;&quot;ABC&quot;&gt;&gt;
│ │ │  3&gt; &lt;&lt;1:1,0:1&gt;&gt;.
│ │ │  &lt;&lt;2:2&gt;&gt;</code></pre><p>The <a href="../../erts-17.0/doc/html/erlang.html#is_bitstring/1"><code class="inline">is_bitstring/1</code></a> BIF tests whether a
│ │ │  term is a bit string, and the <a href="../../erts-17.0/doc/html/erlang.html#is_binary/1"><code class="inline">is_binary/1</code></a>
│ │ │ -BIF tests whether a term is a binary.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">is_bitstring</span><span class="p" data-group-id="8515710215-1">(</span><span class="p" data-group-id="8515710215-2">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="8515710215-2">&gt;&gt;</span><span class="p" data-group-id="8515710215-1">)</span><span class="p">.</span><span class="w">
│ │ │ +BIF tests whether a term is a binary.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">is_bitstring</span><span class="p" data-group-id="3453414793-1">(</span><span class="p" data-group-id="3453414793-2">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="3453414793-2">&gt;&gt;</span><span class="p" data-group-id="3453414793-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">is_binary</span><span class="p" data-group-id="8515710215-3">(</span><span class="p" data-group-id="8515710215-4">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="8515710215-4">&gt;&gt;</span><span class="p" data-group-id="8515710215-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">is_binary</span><span class="p" data-group-id="3453414793-3">(</span><span class="p" data-group-id="3453414793-4">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="3453414793-4">&gt;&gt;</span><span class="p" data-group-id="3453414793-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">is_binary</span><span class="p" data-group-id="8515710215-5">(</span><span class="p" data-group-id="8515710215-6">&lt;&lt;</span><span class="mi">42</span><span class="p" data-group-id="8515710215-6">&gt;&gt;</span><span class="p" data-group-id="8515710215-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">is_binary</span><span class="p" data-group-id="3453414793-5">(</span><span class="p" data-group-id="3453414793-6">&lt;&lt;</span><span class="mi">42</span><span class="p" data-group-id="3453414793-6">&gt;&gt;</span><span class="p" data-group-id="3453414793-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │  </span></code></pre><p>For more examples, see <a href="../../doc/system/bit_syntax.html">Programming Examples</a>.</p><h2 id="reference" class="section-heading">
│ │ │    <a href="#reference" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Reference</span>
│ │ │  </h2>
│ │ │  <p>A term that is <a href="../../doc/system/system_limits.html#unique_references">unique</a>
│ │ │  among connected nodes. A reference is created by calling the
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#make_ref/0"><code class="inline">make_ref/0</code></a> BIF. The
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#is_reference/1"><code class="inline">is_reference/1</code></a> BIF tests whether a term
│ │ │ -is a reference.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Ref</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="4028620510-1">(</span><span class="p" data-group-id="4028620510-1">)</span><span class="p">.</span><span class="w">
│ │ │ +is a reference.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Ref</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="1532470128-1">(</span><span class="p" data-group-id="1532470128-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Ref</span><span class="o">&lt;</span><span class="mf">0.76482849</span><span class="p">.</span><span class="mf">3801088007.198204</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">is_reference</span><span class="p" data-group-id="4028620510-2">(</span><span class="n">Ref</span><span class="p" data-group-id="4028620510-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">is_reference</span><span class="p" data-group-id="1532470128-2">(</span><span class="n">Ref</span><span class="p" data-group-id="1532470128-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span></code></pre><h2 id="fun" class="section-heading">
│ │ │    <a href="#fun" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Fun</span>
│ │ │  </h2>
│ │ │  <p>A fun is a functional object. Funs make it possible to create an anonymous
│ │ │  function and pass the function itself — not its name — as an argument to other
│ │ │ -functions.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="1381955700-1">(</span><span class="n">X</span><span class="p" data-group-id="1381955700-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +functions.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="6235912704-1">(</span><span class="n">X</span><span class="p" data-group-id="6235912704-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.39074546</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">Fun1</span><span class="p" data-group-id="1381955700-2">(</span><span class="mi">2</span><span class="p" data-group-id="1381955700-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">Fun1</span><span class="p" data-group-id="6235912704-2">(</span><span class="mi">2</span><span class="p" data-group-id="6235912704-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span></code></pre><p>The <a href="../../erts-17.0/doc/html/erlang.html#is_function/1"><code class="inline">is_function/1</code></a> and <a href="../../erts-17.0/doc/html/erlang.html#is_function/2"><code class="inline">is_function/2</code></a>
│ │ │ -BIFs test whether a term is a fun.</p><p><em>Examples</em>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="2597946577-1">(</span><span class="p" data-group-id="2597946577-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +BIFs test whether a term is a fun.</p><p><em>Examples</em>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0146898483-1">(</span><span class="p" data-group-id="0146898483-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">43.105768164</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="2597946577-2">(</span><span class="n">F</span><span class="p" data-group-id="2597946577-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="0146898483-2">(</span><span class="n">F</span><span class="p" data-group-id="0146898483-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="2597946577-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="2597946577-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="0146898483-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="0146898483-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="2597946577-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2597946577-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="0146898483-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="0146898483-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span></code></pre><p>Read more about funs in <a href="expressions.html#fun-expressions">Fun Expressions</a>. For more
│ │ │  examples, see <a href="../../doc/system/funs.html">Programming Examples</a>.</p><h2 id="port-identifier" class="section-heading">
│ │ │    <a href="#port-identifier" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Port Identifier</span>
│ │ │  </h2>
│ │ │ @@ -307,94 +307,94 @@
│ │ │  for a new process after a while.</p><p>The BIF <a href="../../erts-17.0/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a> returns the Pid of the calling process. When
│ │ │  <a href="ref_man_processes.html#process-creation">creating a new process</a>, the parent
│ │ │  process will be able to get the Pid of the child process either via the return
│ │ │  value, as is the case when calling the <a href="../../erts-17.0/doc/html/erlang.html#spawn/3"><code class="inline">spawn/3</code></a> BIF, or via
│ │ │  a message, which is the case when calling the
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#spawn_request/5"><code class="inline">spawn_request/5</code></a> BIF. A Pid is typically used
│ │ │  when sending a process a <a href="ref_man_processes.html#signals">signal</a>. The
│ │ │ -<a href="../../erts-17.0/doc/html/erlang.html#is_pid/1"><code class="inline">is_pid/1</code></a> BIF tests whether a term is a Pid.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1282723716-1">(</span><span class="ss">m</span><span class="p" data-group-id="1282723716-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1282723716-2">(</span><span class="p" data-group-id="1282723716-3">[</span><span class="ss">loop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1282723716-3">]</span><span class="p" data-group-id="1282723716-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<a href="../../erts-17.0/doc/html/erlang.html#is_pid/1"><code class="inline">is_pid/1</code></a> BIF tests whether a term is a Pid.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3497142605-1">(</span><span class="ss">m</span><span class="p" data-group-id="3497142605-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3497142605-2">(</span><span class="p" data-group-id="3497142605-3">[</span><span class="ss">loop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3497142605-3">]</span><span class="p" data-group-id="3497142605-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="1282723716-4">(</span><span class="p" data-group-id="1282723716-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="3497142605-4">(</span><span class="p" data-group-id="3497142605-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">who_are_you</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1282723716-5">(</span><span class="s">&quot;I am </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1282723716-6">[</span><span class="nf">self</span><span class="p" data-group-id="1282723716-7">(</span><span class="p" data-group-id="1282723716-7">)</span><span class="p" data-group-id="1282723716-6">]</span><span class="p" data-group-id="1282723716-5">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="1282723716-8">(</span><span class="p" data-group-id="1282723716-8">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3497142605-5">(</span><span class="s">&quot;I am </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3497142605-6">[</span><span class="nf">self</span><span class="p" data-group-id="3497142605-7">(</span><span class="p" data-group-id="3497142605-7">)</span><span class="p" data-group-id="3497142605-6">]</span><span class="p" data-group-id="3497142605-5">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="3497142605-8">(</span><span class="p" data-group-id="3497142605-8">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="1282723716-9">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">loop</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1282723716-10">[</span><span class="p" data-group-id="1282723716-10">]</span><span class="p" data-group-id="1282723716-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="3497142605-9">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">loop</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3497142605-10">[</span><span class="p" data-group-id="3497142605-10">]</span><span class="p" data-group-id="3497142605-9">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.58</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="gp unselectable">2&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">who_are_you</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="n">I</span><span class="w"> </span><span class="ss">am</span><span class="w"> </span><span class="o">&lt;</span><span class="mf">0.58</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="ss">who_are_you</span></code></pre><p>Read more about processes in <a href="ref_man_processes.html">Processes</a>.</p><h2 id="tuple" class="section-heading">
│ │ │    <a href="#tuple" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Tuple</span>
│ │ │  </h2>
│ │ │  <p>A tuple is a compound data type with a fixed number of terms:</p><pre><code class="text">{Term1,...,TermN}</code></pre><p>Each term <code class="inline">Term</code> in the tuple is called an <em>element</em>. The number of elements is
│ │ │ -said to be the <em>size</em> of the tuple.</p><p>There are a number of BIFs to manipulate tuples.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2018155683-1">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">24</span><span class="p">,</span><span class="p" data-group-id="2018155683-2">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="2018155683-2">}</span><span class="p" data-group-id="2018155683-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2018155683-3">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">24</span><span class="p">,</span><span class="p" data-group-id="2018155683-4">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="2018155683-4">}</span><span class="p" data-group-id="2018155683-3">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">element</span><span class="p" data-group-id="2018155683-5">(</span><span class="mi">1</span><span class="p">,</span><span class="n">P</span><span class="p" data-group-id="2018155683-5">)</span><span class="p">.</span><span class="w">
│ │ │ +said to be the <em>size</em> of the tuple.</p><p>There are a number of BIFs to manipulate tuples.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9561341834-1">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">24</span><span class="p">,</span><span class="p" data-group-id="9561341834-2">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="9561341834-2">}</span><span class="p" data-group-id="9561341834-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9561341834-3">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">24</span><span class="p">,</span><span class="p" data-group-id="9561341834-4">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="9561341834-4">}</span><span class="p" data-group-id="9561341834-3">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">element</span><span class="p" data-group-id="9561341834-5">(</span><span class="mi">1</span><span class="p">,</span><span class="n">P</span><span class="p" data-group-id="9561341834-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">adam</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">element</span><span class="p" data-group-id="2018155683-6">(</span><span class="mi">3</span><span class="p">,</span><span class="n">P</span><span class="p" data-group-id="2018155683-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2018155683-7">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="2018155683-7">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="n">P2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="2018155683-8">(</span><span class="mi">2</span><span class="p">,</span><span class="n">P</span><span class="p">,</span><span class="mi">25</span><span class="p" data-group-id="2018155683-8">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2018155683-9">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">25</span><span class="p">,</span><span class="p" data-group-id="2018155683-10">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="2018155683-10">}</span><span class="p" data-group-id="2018155683-9">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="2018155683-11">(</span><span class="n">P</span><span class="p" data-group-id="2018155683-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">element</span><span class="p" data-group-id="9561341834-6">(</span><span class="mi">3</span><span class="p">,</span><span class="n">P</span><span class="p" data-group-id="9561341834-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9561341834-7">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="9561341834-7">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="n">P2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="9561341834-8">(</span><span class="mi">2</span><span class="p">,</span><span class="n">P</span><span class="p">,</span><span class="mi">25</span><span class="p" data-group-id="9561341834-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9561341834-9">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">25</span><span class="p">,</span><span class="p" data-group-id="9561341834-10">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="9561341834-10">}</span><span class="p" data-group-id="9561341834-9">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="9561341834-11">(</span><span class="n">P</span><span class="p" data-group-id="9561341834-11">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="2018155683-12">(</span><span class="p" data-group-id="2018155683-13">{</span><span class="p" data-group-id="2018155683-13">}</span><span class="p" data-group-id="2018155683-12">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="9561341834-12">(</span><span class="p" data-group-id="9561341834-13">{</span><span class="p" data-group-id="9561341834-13">}</span><span class="p" data-group-id="9561341834-12">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">0</span><span class="w">
│ │ │ -</span><span class="gp unselectable">7&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="2018155683-14">(</span><span class="p" data-group-id="2018155683-15">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="2018155683-15">}</span><span class="p" data-group-id="2018155683-14">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">7&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="9561341834-14">(</span><span class="p" data-group-id="9561341834-15">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="9561341834-15">}</span><span class="p" data-group-id="9561341834-14">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span></code></pre><h2 id="map" class="section-heading">
│ │ │    <a href="#map" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Map</span>
│ │ │  </h2>
│ │ │  <p>A map is a compound data type with a variable number of key-value associations:</p><pre><code class="text">#{Key1 =&gt; Value1, ..., KeyN =&gt; ValueN}</code></pre><p>Each key-value association in the map is called an <em>association pair</em>. The key
│ │ │  and value parts of the pair are called <em>elements</em>. The number of association
│ │ │ -pairs is said to be the <em>size</em> of the map.</p><p>There are a number of BIFs to manipulate maps.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2369977455-1">#{</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">24</span><span class="p">,</span><span class="w"> </span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2369977455-2">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="2369977455-2">}</span><span class="p" data-group-id="2369977455-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2369977455-3">#{</span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">24</span><span class="p">,</span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2369977455-4">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="2369977455-4">}</span><span class="p">,</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p" data-group-id="2369977455-3">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">maps</span><span class="p">:</span><span class="nf">get</span><span class="p" data-group-id="2369977455-5">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="2369977455-5">)</span><span class="p">.</span><span class="w">
│ │ │ +pairs is said to be the <em>size</em> of the map.</p><p>There are a number of BIFs to manipulate maps.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6668376427-1">#{</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">24</span><span class="p">,</span><span class="w"> </span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6668376427-2">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="6668376427-2">}</span><span class="p" data-group-id="6668376427-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6668376427-3">#{</span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">24</span><span class="p">,</span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6668376427-4">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="6668376427-4">}</span><span class="p">,</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p" data-group-id="6668376427-3">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">maps</span><span class="p">:</span><span class="nf">get</span><span class="p" data-group-id="6668376427-5">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="6668376427-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">adam</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">maps</span><span class="p">:</span><span class="nf">get</span><span class="p" data-group-id="2369977455-6">(</span><span class="ss">date</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="2369977455-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2369977455-7">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="2369977455-7">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="2369977455-8">(</span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="mi">25</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="2369977455-8">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2369977455-9">#{</span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">25</span><span class="p">,</span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2369977455-10">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="2369977455-10">}</span><span class="p">,</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p" data-group-id="2369977455-9">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="2369977455-11">(</span><span class="n">M2</span><span class="p" data-group-id="2369977455-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">maps</span><span class="p">:</span><span class="nf">get</span><span class="p" data-group-id="6668376427-6">(</span><span class="ss">date</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="6668376427-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6668376427-7">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="6668376427-7">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="6668376427-8">(</span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="mi">25</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="6668376427-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6668376427-9">#{</span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">25</span><span class="p">,</span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6668376427-10">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="6668376427-10">}</span><span class="p">,</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p" data-group-id="6668376427-9">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="6668376427-11">(</span><span class="n">M2</span><span class="p" data-group-id="6668376427-11">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="2369977455-12">(</span><span class="p" data-group-id="2369977455-13">#{</span><span class="p" data-group-id="2369977455-13">}</span><span class="p" data-group-id="2369977455-12">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="6668376427-12">(</span><span class="p" data-group-id="6668376427-13">#{</span><span class="p" data-group-id="6668376427-13">}</span><span class="p" data-group-id="6668376427-12">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">0</span></code></pre><p>A collection of map-processing functions can be found in the module <a href="../../lib/stdlib-8.0/doc/html/maps.html"><code class="inline">maps</code></a>
│ │ │  in STDLIB.</p><p>Read more about maps in <a href="expressions.html#map-expressions">Map Expressions</a>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Maps were introduced as an experimental feature in Erlang/OTP R17. Their
│ │ │  functionality was extended and became fully supported in Erlang/OTP 18.</p></section><h2 id="list" class="section-heading">
│ │ │    <a href="#list" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">List</span>
│ │ │  </h2>
│ │ │  <p>A list is a compound data type with a variable number of terms.</p><pre><code class="text">[Term1,...,TermN]</code></pre><p>Each term <code class="inline">Term</code> in the list is called an <em>element</em>. The number of elements is
│ │ │  said to be the <em>length</em> of the list.</p><p>Formally, a list is either the empty list <code class="inline">[]</code> or consists of a <em>head</em> (first
│ │ │  element) and a <em>tail</em> (remainder of the list). The <em>tail</em> is also a list. The
│ │ │  latter can be expressed as <code class="inline">[H|T]</code>. The notation <code class="inline">[Term1,...,TermN]</code> above is
│ │ │  equivalent to the list <code class="inline">[Term1|[...|[TermN|[]]]]</code>.</p><p><em>Example:</em></p><p><code class="inline">[]</code> is a list, thus<br/><code class="inline">[c|[]]</code> is a list, thus<br/><code class="inline">[b|[c|[]]]</code> is a list, thus<br/><code class="inline">[a|[b|[c|[]]]]</code> is a list, or in short <code class="inline">[a,b,c]</code></p><p>A list where the tail is a list is sometimes called a <em>proper list</em>. It is
│ │ │  allowed to have a list where the tail is not a list, for example, <code class="inline">[a|b]</code>.
│ │ │ -However, this type of list is of little practical use.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">L1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0820601765-1">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="0820601765-2">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0820601765-2">}</span><span class="p" data-group-id="0820601765-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0820601765-3">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="0820601765-4">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0820601765-4">}</span><span class="p" data-group-id="0820601765-3">]</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="0820601765-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0820601765-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L1</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0820601765-6">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="0820601765-7">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0820601765-7">}</span><span class="p" data-group-id="0820601765-6">]</span><span class="w">
│ │ │ +However, this type of list is of little practical use.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">L1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6778355467-1">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6778355467-2">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6778355467-2">}</span><span class="p" data-group-id="6778355467-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6778355467-3">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6778355467-4">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6778355467-4">}</span><span class="p" data-group-id="6778355467-3">]</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="6778355467-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6778355467-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L1</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6778355467-6">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6778355467-7">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6778355467-7">}</span><span class="p" data-group-id="6778355467-6">]</span><span class="w">
│ │ │  </span><span class="gp unselectable">3&gt; </span><span class="n">H</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">a</span><span class="w">
│ │ │  </span><span class="gp unselectable">4&gt; </span><span class="n">T</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0820601765-8">[</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="0820601765-9">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0820601765-9">}</span><span class="p" data-group-id="0820601765-8">]</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="n">L2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0820601765-10">[</span><span class="ss">d</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0820601765-10">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0820601765-11">[</span><span class="ss">d</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="0820601765-12">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0820601765-12">}</span><span class="p" data-group-id="0820601765-11">]</span><span class="w">
│ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nf">length</span><span class="p" data-group-id="0820601765-13">(</span><span class="n">L1</span><span class="p" data-group-id="0820601765-13">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6778355467-8">[</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6778355467-9">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6778355467-9">}</span><span class="p" data-group-id="6778355467-8">]</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="n">L2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6778355467-10">[</span><span class="ss">d</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6778355467-10">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6778355467-11">[</span><span class="ss">d</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6778355467-12">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6778355467-12">}</span><span class="p" data-group-id="6778355467-11">]</span><span class="w">
│ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nf">length</span><span class="p" data-group-id="6778355467-13">(</span><span class="n">L1</span><span class="p" data-group-id="6778355467-13">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ -</span><span class="gp unselectable">7&gt; </span><span class="nf">length</span><span class="p" data-group-id="0820601765-14">(</span><span class="p" data-group-id="0820601765-15">[</span><span class="p" data-group-id="0820601765-15">]</span><span class="p" data-group-id="0820601765-14">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">7&gt; </span><span class="nf">length</span><span class="p" data-group-id="6778355467-14">(</span><span class="p" data-group-id="6778355467-15">[</span><span class="p" data-group-id="6778355467-15">]</span><span class="p" data-group-id="6778355467-14">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">0</span></code></pre><p>A collection of list-processing functions can be found in the module
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/lists.html"><code class="inline">lists</code></a> in STDLIB.</p><h2 id="string" class="section-heading">
│ │ │    <a href="#string" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">String</span>
│ │ │  </h2>
│ │ │ @@ -514,64 +514,64 @@
│ │ │    <span class="text">Record</span>
│ │ │  </h2>
│ │ │  <p>A record is a data structure for storing a fixed number of elements. It has
│ │ │  named fields and is similar to a struct in C. However, a record is not a true
│ │ │  data type. Instead, record expressions are translated to tuple expressions
│ │ │  during compilation. Therefore, record expressions are not understood by the
│ │ │  shell unless special actions are taken. For details, see module <a href="../../lib/stdlib-8.0/doc/html/shell.html"><code class="inline">shell</code></a>
│ │ │ -in STDLIB.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9524601924-1">(</span><span class="ss">person</span><span class="p" data-group-id="9524601924-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9524601924-2">(</span><span class="p" data-group-id="9524601924-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9524601924-3">]</span><span class="p" data-group-id="9524601924-2">)</span><span class="p">.</span><span class="w">
│ │ │ +in STDLIB.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6351471568-1">(</span><span class="ss">person</span><span class="p" data-group-id="6351471568-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6351471568-2">(</span><span class="p" data-group-id="6351471568-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6351471568-3">]</span><span class="p" data-group-id="6351471568-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9524601924-4">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9524601924-5">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="9524601924-5">}</span><span class="p" data-group-id="9524601924-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6351471568-4">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6351471568-5">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="6351471568-5">}</span><span class="p" data-group-id="6351471568-4">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">new</span><span class="p" data-group-id="9524601924-6">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="9524601924-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9524601924-7">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="o">=</span><span class="n">Age</span><span class="p" data-group-id="9524601924-7">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">new</span><span class="p" data-group-id="6351471568-6">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="6351471568-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6351471568-7">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="o">=</span><span class="n">Age</span><span class="p" data-group-id="6351471568-7">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nc">person</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="9524601924-8">(</span><span class="ss">ernie</span><span class="p">,</span><span class="w"> </span><span class="mi">44</span><span class="p" data-group-id="9524601924-8">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9524601924-9">{</span><span class="ss">person</span><span class="p">,</span><span class="ss">ernie</span><span class="p">,</span><span class="mi">44</span><span class="p" data-group-id="9524601924-9">}</span></code></pre><p>Read more about records in <a href="ref_man_records.html">Records</a>. More examples are
│ │ │ +</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nc">person</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="6351471568-8">(</span><span class="ss">ernie</span><span class="p">,</span><span class="w"> </span><span class="mi">44</span><span class="p" data-group-id="6351471568-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6351471568-9">{</span><span class="ss">person</span><span class="p">,</span><span class="ss">ernie</span><span class="p">,</span><span class="mi">44</span><span class="p" data-group-id="6351471568-9">}</span></code></pre><p>Read more about records in <a href="ref_man_records.html">Records</a>. More examples are
│ │ │  found in <a href="../../doc/system/prog_ex_records.html">Programming Examples</a>.</p><h2 id="native-record" class="section-heading">
│ │ │    <a href="#native-record" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Native Record</span>
│ │ │  </h2>
│ │ │  <p>A native record is a data structure for storing a fixed number
│ │ │  of elements. It is similar to the traditional <a href="#record">tuple-based records</a>,
│ │ │ -except that it is a true data type.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3746051790-1">(</span><span class="ss">person</span><span class="p" data-group-id="3746051790-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3746051790-2">(</span><span class="p" data-group-id="3746051790-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3746051790-3">]</span><span class="p" data-group-id="3746051790-2">)</span><span class="p">.</span><span class="w">
│ │ │ +except that it is a true data type.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3225992253-1">(</span><span class="ss">person</span><span class="p" data-group-id="3225992253-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3225992253-2">(</span><span class="p" data-group-id="3225992253-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3225992253-3">]</span><span class="p" data-group-id="3225992253-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3746051790-4">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="3746051790-4">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3225992253-4">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="3225992253-4">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">new</span><span class="p" data-group-id="3746051790-5">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="3746051790-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3746051790-6">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="o">=</span><span class="n">Age</span><span class="p" data-group-id="3746051790-6">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">person</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="4260027096-1">(</span><span class="ss">ernie</span><span class="p">,</span><span class="w"> </span><span class="mi">44</span><span class="p" data-group-id="4260027096-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">#</span><span class="nc">person</span><span class="p">:</span><span class="ss">person</span><span class="p" data-group-id="4260027096-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">ernie</span><span class="p">,</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">44</span><span class="p" data-group-id="4260027096-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">is_record</span><span class="p" data-group-id="4260027096-3">(</span><span class="n">P</span><span class="p" data-group-id="4260027096-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">new</span><span class="p" data-group-id="3225992253-5">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="3225992253-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3225992253-6">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="o">=</span><span class="n">Age</span><span class="p" data-group-id="3225992253-6">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">person</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="4635016296-1">(</span><span class="ss">ernie</span><span class="p">,</span><span class="w"> </span><span class="mi">44</span><span class="p" data-group-id="4635016296-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">#</span><span class="nc">person</span><span class="p">:</span><span class="ss">person</span><span class="p" data-group-id="4635016296-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">ernie</span><span class="p">,</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">44</span><span class="p" data-group-id="4635016296-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">is_record</span><span class="p" data-group-id="4635016296-3">(</span><span class="n">P</span><span class="p" data-group-id="4635016296-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="4260027096-4">(</span><span class="n">P</span><span class="p" data-group-id="4260027096-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="4635016296-4">(</span><span class="n">P</span><span class="p" data-group-id="4635016296-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nf">is_map</span><span class="p" data-group-id="4260027096-5">(</span><span class="n">P</span><span class="p" data-group-id="4260027096-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nf">is_map</span><span class="p" data-group-id="4635016296-5">(</span><span class="n">P</span><span class="p" data-group-id="4635016296-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span></code></pre><section role="note" class="admonition warning"><h4 class="admonition-title warning">Warning</h4><p>Native records are considered experimental in Erlang/OTP 29. This
│ │ │  means that their behavior may change, potentially requiring updates
│ │ │  to applications that use them.</p></section><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Native records were introduced in Erlang/OTP 29.</p></section><h2 id="boolean" class="section-heading">
│ │ │    <a href="#boolean" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Boolean</span>
│ │ │  </h2>
│ │ │  <p>There is no Boolean data type in Erlang. Instead, the atoms <code class="inline">true</code> and <code class="inline">false</code>
│ │ │  are used to denote Boolean values. The <a href="../../erts-17.0/doc/html/erlang.html#is_boolean/1"><code class="inline">is_boolean/1</code></a>
│ │ │  BIF tests whether a term is a boolean.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="mi">2</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │  </span><span class="gp unselectable">2&gt; </span><span class="ss">true</span><span class="w"> </span><span class="ow">or</span><span class="w"> </span><span class="ss">false</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="0931355987-1">(</span><span class="ss">true</span><span class="p" data-group-id="0931355987-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="1886171526-1">(</span><span class="ss">true</span><span class="p" data-group-id="1886171526-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="0931355987-2">(</span><span class="ss">false</span><span class="p" data-group-id="0931355987-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="1886171526-2">(</span><span class="ss">false</span><span class="p" data-group-id="1886171526-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="0931355987-3">(</span><span class="ss">ok</span><span class="p" data-group-id="0931355987-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="1886171526-3">(</span><span class="ss">ok</span><span class="p" data-group-id="1886171526-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span></code></pre><h2 id="escape-sequences" class="section-heading">
│ │ │    <a href="#escape-sequences" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Escape Sequences</span>
│ │ │  </h2>
│ │ │  <p>Within strings (<code class="inline">&quot;</code>-delimited), quoted atoms, and the content of
│ │ │ @@ -589,47 +589,47 @@
│ │ │  <a href="data_types.html#sigil"><code class="inline">~b</code> or <code class="inline">~s</code> sigils</a> the escape sequences for normal
│ │ │  strings, above, are used.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Triple-quoted strings and sigils were introduced in Erlang/OTP 27.</p></section><h2 id="type-conversions" class="section-heading">
│ │ │    <a href="#type-conversions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Type Conversions</span>
│ │ │  </h2>
│ │ │ -<p>There are a number of BIFs for type conversions.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="7556239687-1">(</span><span class="ss">hello</span><span class="p" data-group-id="7556239687-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>There are a number of BIFs for type conversions.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="3165051058-1">(</span><span class="ss">hello</span><span class="p" data-group-id="3165051058-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;hello&quot;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="7556239687-2">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="7556239687-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="3165051058-2">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="3165051058-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="7556239687-3">(</span><span class="p" data-group-id="7556239687-4">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="7556239687-4">&gt;&gt;</span><span class="p" data-group-id="7556239687-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="3165051058-3">(</span><span class="p" data-group-id="3165051058-4">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="3165051058-4">&gt;&gt;</span><span class="p" data-group-id="3165051058-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;hello&quot;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="7556239687-5">(</span><span class="p" data-group-id="7556239687-6">&lt;&lt;</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="7556239687-6">&gt;&gt;</span><span class="p" data-group-id="7556239687-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="3165051058-5">(</span><span class="p" data-group-id="3165051058-6">&lt;&lt;</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="3165051058-6">&gt;&gt;</span><span class="p" data-group-id="3165051058-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;hello&quot;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nf">list_to_binary</span><span class="p" data-group-id="7556239687-7">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="7556239687-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7556239687-8">&lt;&lt;</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="7556239687-8">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="7556239687-9">(</span><span class="mf">7.0</span><span class="p" data-group-id="7556239687-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nf">list_to_binary</span><span class="p" data-group-id="3165051058-7">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="3165051058-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3165051058-8">&lt;&lt;</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="3165051058-8">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="3165051058-9">(</span><span class="mf">7.0</span><span class="p" data-group-id="3165051058-9">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;7.00000000000000000000e+00&quot;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">7&gt; </span><span class="nf">list_to_float</span><span class="p" data-group-id="7556239687-10">(</span><span class="s">&quot;7.000e+00&quot;</span><span class="p" data-group-id="7556239687-10">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">7&gt; </span><span class="nf">list_to_float</span><span class="p" data-group-id="3165051058-10">(</span><span class="s">&quot;7.000e+00&quot;</span><span class="p" data-group-id="3165051058-10">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">7.0</span><span class="w">
│ │ │ -</span><span class="gp unselectable">8&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="7556239687-11">(</span><span class="mi">77</span><span class="p" data-group-id="7556239687-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">8&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="3165051058-11">(</span><span class="mi">77</span><span class="p" data-group-id="3165051058-11">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;77&quot;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">9&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="7556239687-12">(</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="7556239687-12">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">9&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="3165051058-12">(</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="3165051058-12">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">77</span><span class="w">
│ │ │ -</span><span class="gp unselectable">10&gt; </span><span class="nf">tuple_to_list</span><span class="p" data-group-id="7556239687-13">(</span><span class="p" data-group-id="7556239687-14">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="7556239687-14">}</span><span class="p" data-group-id="7556239687-13">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7556239687-15">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="7556239687-15">]</span><span class="w">
│ │ │ -</span><span class="gp unselectable">11&gt; </span><span class="nf">list_to_tuple</span><span class="p" data-group-id="7556239687-16">(</span><span class="p" data-group-id="7556239687-17">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="7556239687-17">]</span><span class="p" data-group-id="7556239687-16">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7556239687-18">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="7556239687-18">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">12&gt; </span><span class="nf">term_to_binary</span><span class="p" data-group-id="7556239687-19">(</span><span class="p" data-group-id="7556239687-20">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="7556239687-20">}</span><span class="p" data-group-id="7556239687-19">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7556239687-21">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">97</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="7556239687-21">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">13&gt; </span><span class="nf">binary_to_term</span><span class="p" data-group-id="7556239687-22">(</span><span class="p" data-group-id="7556239687-23">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">97</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="7556239687-23">&gt;&gt;</span><span class="p" data-group-id="7556239687-22">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7556239687-24">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="7556239687-24">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">14&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="7556239687-25">(</span><span class="p" data-group-id="7556239687-26">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="7556239687-26">&gt;&gt;</span><span class="p" data-group-id="7556239687-25">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">10&gt; </span><span class="nf">tuple_to_list</span><span class="p" data-group-id="3165051058-13">(</span><span class="p" data-group-id="3165051058-14">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3165051058-14">}</span><span class="p" data-group-id="3165051058-13">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3165051058-15">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3165051058-15">]</span><span class="w">
│ │ │ +</span><span class="gp unselectable">11&gt; </span><span class="nf">list_to_tuple</span><span class="p" data-group-id="3165051058-16">(</span><span class="p" data-group-id="3165051058-17">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3165051058-17">]</span><span class="p" data-group-id="3165051058-16">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3165051058-18">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3165051058-18">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">12&gt; </span><span class="nf">term_to_binary</span><span class="p" data-group-id="3165051058-19">(</span><span class="p" data-group-id="3165051058-20">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3165051058-20">}</span><span class="p" data-group-id="3165051058-19">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3165051058-21">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">97</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="3165051058-21">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">13&gt; </span><span class="nf">binary_to_term</span><span class="p" data-group-id="3165051058-22">(</span><span class="p" data-group-id="3165051058-23">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">97</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="3165051058-23">&gt;&gt;</span><span class="p" data-group-id="3165051058-22">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3165051058-24">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3165051058-24">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">14&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="3165051058-25">(</span><span class="p" data-group-id="3165051058-26">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="3165051058-26">&gt;&gt;</span><span class="p" data-group-id="3165051058-25">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">77</span><span class="w">
│ │ │ -</span><span class="gp unselectable">15&gt; </span><span class="nf">integer_to_binary</span><span class="p" data-group-id="7556239687-27">(</span><span class="mi">77</span><span class="p" data-group-id="7556239687-27">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7556239687-28">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="7556239687-28">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">16&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="7556239687-29">(</span><span class="mf">7.0</span><span class="p" data-group-id="7556239687-29">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7556239687-30">&lt;&lt;</span><span class="s">&quot;7.00000000000000000000e+00&quot;</span><span class="p" data-group-id="7556239687-30">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">17&gt; </span><span class="nf">binary_to_float</span><span class="p" data-group-id="7556239687-31">(</span><span class="p" data-group-id="7556239687-32">&lt;&lt;</span><span class="s">&quot;7.000e+00&quot;</span><span class="p" data-group-id="7556239687-32">&gt;&gt;</span><span class="p" data-group-id="7556239687-31">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">15&gt; </span><span class="nf">integer_to_binary</span><span class="p" data-group-id="3165051058-27">(</span><span class="mi">77</span><span class="p" data-group-id="3165051058-27">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3165051058-28">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="3165051058-28">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">16&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="3165051058-29">(</span><span class="mf">7.0</span><span class="p" data-group-id="3165051058-29">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3165051058-30">&lt;&lt;</span><span class="s">&quot;7.00000000000000000000e+00&quot;</span><span class="p" data-group-id="3165051058-30">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">17&gt; </span><span class="nf">binary_to_float</span><span class="p" data-group-id="3165051058-31">(</span><span class="p" data-group-id="3165051058-32">&lt;&lt;</span><span class="s">&quot;7.000e+00&quot;</span><span class="p" data-group-id="3165051058-32">&gt;&gt;</span><span class="p" data-group-id="3165051058-31">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">7.0</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="character_set.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/design_principles.html
│ │ │ @@ -152,135 +152,135 @@
│ │ │  the code for a process in a generic part (a behaviour module) and a specific
│ │ │  part (a <em>callback module</em>).</p><p>The behaviour module is part of Erlang/OTP. To implement a process such as a
│ │ │  supervisor, the user only needs to implement the callback module, which is to
│ │ │  export a pre-defined set of functions, the <em>callback functions</em>.</p><p>The following example illustrates how code can be divided into a generic and a
│ │ │  specific part. Consider the following code (written in plain Erlang) for a
│ │ │  simple server, which keeps track of a number of &quot;channels&quot;. Other processes can
│ │ │  allocate and free the channels by calling the functions <code class="inline">alloc/0</code> and <code class="inline">free/1</code>,
│ │ │ -respectively.</p><p><a href="" id="ch1"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8432097842-1">(</span><span class="ss">ch1</span><span class="p" data-group-id="8432097842-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8432097842-2">(</span><span class="p" data-group-id="8432097842-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8432097842-3">]</span><span class="p" data-group-id="8432097842-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8432097842-4">(</span><span class="p" data-group-id="8432097842-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8432097842-5">]</span><span class="p" data-group-id="8432097842-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8432097842-6">(</span><span class="p" data-group-id="8432097842-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8432097842-7">]</span><span class="p" data-group-id="8432097842-6">)</span><span class="p">.</span><span class="w">
│ │ │ +respectively.</p><p><a href="" id="ch1"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3726411666-1">(</span><span class="ss">ch1</span><span class="p" data-group-id="3726411666-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3726411666-2">(</span><span class="p" data-group-id="3726411666-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3726411666-3">]</span><span class="p" data-group-id="3726411666-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3726411666-4">(</span><span class="p" data-group-id="3726411666-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3726411666-5">]</span><span class="p" data-group-id="3726411666-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3726411666-6">(</span><span class="p" data-group-id="3726411666-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3726411666-7">]</span><span class="p" data-group-id="3726411666-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="8432097842-8">(</span><span class="p" data-group-id="8432097842-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="8432097842-9">(</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8432097842-10">[</span><span class="p" data-group-id="8432097842-10">]</span><span class="p" data-group-id="8432097842-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="3726411666-8">(</span><span class="p" data-group-id="3726411666-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="3726411666-9">(</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3726411666-10">[</span><span class="p" data-group-id="3726411666-10">]</span><span class="p" data-group-id="3726411666-9">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="8432097842-11">(</span><span class="p" data-group-id="8432097842-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ch1</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8432097842-12">{</span><span class="nf">self</span><span class="p" data-group-id="8432097842-13">(</span><span class="p" data-group-id="8432097842-13">)</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="8432097842-12">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="3726411666-11">(</span><span class="p" data-group-id="3726411666-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ch1</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3726411666-12">{</span><span class="nf">self</span><span class="p" data-group-id="3726411666-13">(</span><span class="p" data-group-id="3726411666-13">)</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="3726411666-12">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="8432097842-14">{</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="8432097842-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3726411666-14">{</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="3726411666-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="n">Res</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="8432097842-15">(</span><span class="n">Ch</span><span class="p" data-group-id="8432097842-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ch1</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8432097842-16">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="8432097842-16">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="3726411666-15">(</span><span class="n">Ch</span><span class="p" data-group-id="3726411666-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ch1</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3726411666-16">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3726411666-16">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="8432097842-17">(</span><span class="p" data-group-id="8432097842-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="8432097842-18">(</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8432097842-19">(</span><span class="p" data-group-id="8432097842-19">)</span><span class="p" data-group-id="8432097842-18">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Chs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="8432097842-20">(</span><span class="p" data-group-id="8432097842-20">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="8432097842-21">(</span><span class="n">Chs</span><span class="p" data-group-id="8432097842-21">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="3726411666-17">(</span><span class="p" data-group-id="3726411666-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="3726411666-18">(</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3726411666-19">(</span><span class="p" data-group-id="3726411666-19">)</span><span class="p" data-group-id="3726411666-18">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Chs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="3726411666-20">(</span><span class="p" data-group-id="3726411666-20">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="3726411666-21">(</span><span class="n">Chs</span><span class="p" data-group-id="3726411666-21">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="8432097842-22">(</span><span class="n">Chs</span><span class="p" data-group-id="8432097842-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="3726411666-22">(</span><span class="n">Chs</span><span class="p" data-group-id="3726411666-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="8432097842-23">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="8432097842-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="8432097842-24">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="8432097842-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="8432097842-25">(</span><span class="n">Chs</span><span class="p" data-group-id="8432097842-25">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8432097842-26">{</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="8432097842-26">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="8432097842-27">(</span><span class="n">Chs2</span><span class="p" data-group-id="8432097842-27">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="8432097842-28">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="8432097842-28">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="8432097842-29">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="8432097842-29">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="8432097842-30">(</span><span class="n">Chs2</span><span class="p" data-group-id="8432097842-30">)</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>The code for the server can be rewritten into a generic part <code class="inline">server.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6671840160-1">(</span><span class="ss">server</span><span class="p" data-group-id="6671840160-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6671840160-2">(</span><span class="p" data-group-id="6671840160-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6671840160-3">]</span><span class="p" data-group-id="6671840160-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6671840160-4">(</span><span class="p" data-group-id="6671840160-5">[</span><span class="ss">call</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6671840160-5">]</span><span class="p" data-group-id="6671840160-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6671840160-6">(</span><span class="p" data-group-id="6671840160-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6671840160-7">]</span><span class="p" data-group-id="6671840160-6">)</span><span class="p">.</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3726411666-23">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="3726411666-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="3726411666-24">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="3726411666-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="3726411666-25">(</span><span class="n">Chs</span><span class="p" data-group-id="3726411666-25">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3726411666-26">{</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3726411666-26">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="3726411666-27">(</span><span class="n">Chs2</span><span class="p" data-group-id="3726411666-27">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3726411666-28">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3726411666-28">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="3726411666-29">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3726411666-29">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="3726411666-30">(</span><span class="n">Chs2</span><span class="p" data-group-id="3726411666-30">)</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>The code for the server can be rewritten into a generic part <code class="inline">server.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2874132227-1">(</span><span class="ss">server</span><span class="p" data-group-id="2874132227-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2874132227-2">(</span><span class="p" data-group-id="2874132227-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2874132227-3">]</span><span class="p" data-group-id="2874132227-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2874132227-4">(</span><span class="p" data-group-id="2874132227-5">[</span><span class="ss">call</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2874132227-5">]</span><span class="p" data-group-id="2874132227-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2874132227-6">(</span><span class="p" data-group-id="2874132227-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2874132227-7">]</span><span class="p" data-group-id="2874132227-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="6671840160-8">(</span><span class="n">Mod</span><span class="p" data-group-id="6671840160-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="6671840160-9">(</span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6671840160-10">[</span><span class="n">Mod</span><span class="p" data-group-id="6671840160-10">]</span><span class="p" data-group-id="6671840160-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="2874132227-8">(</span><span class="n">Mod</span><span class="p" data-group-id="2874132227-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="2874132227-9">(</span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2874132227-10">[</span><span class="n">Mod</span><span class="p" data-group-id="2874132227-10">]</span><span class="p" data-group-id="2874132227-9">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">call</span><span class="p" data-group-id="6671840160-11">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="6671840160-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Name</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6671840160-12">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6671840160-13">(</span><span class="p" data-group-id="6671840160-13">)</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="6671840160-12">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">call</span><span class="p" data-group-id="2874132227-11">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2874132227-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Name</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2874132227-12">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2874132227-13">(</span><span class="p" data-group-id="2874132227-13">)</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2874132227-12">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="6671840160-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="6671840160-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2874132227-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="2874132227-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="n">Res</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">cast</span><span class="p" data-group-id="6671840160-15">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="6671840160-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Name</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6671840160-16">{</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="6671840160-16">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">cast</span><span class="p" data-group-id="2874132227-15">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2874132227-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Name</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2874132227-16">{</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2874132227-16">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="6671840160-17">(</span><span class="n">Mod</span><span class="p" data-group-id="6671840160-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="6671840160-18">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6671840160-19">(</span><span class="p" data-group-id="6671840160-19">)</span><span class="p" data-group-id="6671840160-18">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">init</span><span class="p" data-group-id="6671840160-20">(</span><span class="p" data-group-id="6671840160-20">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="6671840160-21">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="6671840160-21">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="2874132227-17">(</span><span class="n">Mod</span><span class="p" data-group-id="2874132227-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="2874132227-18">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2874132227-19">(</span><span class="p" data-group-id="2874132227-19">)</span><span class="p" data-group-id="2874132227-18">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">init</span><span class="p" data-group-id="2874132227-20">(</span><span class="p" data-group-id="2874132227-20">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="2874132227-21">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2874132227-21">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="6671840160-22">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="6671840160-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="2874132227-22">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2874132227-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="6671840160-23">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="6671840160-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="6671840160-24">{</span><span class="n">Res</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="6671840160-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">handle_call</span><span class="p" data-group-id="6671840160-25">(</span><span class="n">Req</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="6671840160-25">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6671840160-26">{</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="6671840160-26">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="6671840160-27">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="6671840160-27">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="6671840160-28">{</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="6671840160-28">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">State2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">handle_cast</span><span class="p" data-group-id="6671840160-29">(</span><span class="n">Req</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="6671840160-29">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="6671840160-30">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="6671840160-30">)</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>And a callback module <code class="inline">ch2.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2625608772-1">(</span><span class="ss">ch2</span><span class="p" data-group-id="2625608772-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2625608772-2">(</span><span class="p" data-group-id="2625608772-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2625608772-3">]</span><span class="p" data-group-id="2625608772-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2625608772-4">(</span><span class="p" data-group-id="2625608772-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2625608772-5">]</span><span class="p" data-group-id="2625608772-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2625608772-6">(</span><span class="p" data-group-id="2625608772-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2625608772-7">]</span><span class="p" data-group-id="2625608772-6">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="2625608772-8">(</span><span class="p" data-group-id="2625608772-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2625608772-9">(</span><span class="ss">ch2</span><span class="p" data-group-id="2625608772-9">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="2625608772-10">(</span><span class="p" data-group-id="2625608772-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="2625608772-11">(</span><span class="ss">ch2</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="2625608772-11">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="2625608772-12">(</span><span class="n">Ch</span><span class="p" data-group-id="2625608772-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="2625608772-13">(</span><span class="ss">ch2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2625608772-14">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2625608772-14">}</span><span class="p" data-group-id="2625608772-13">)</span><span class="p">.</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2874132227-23">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2874132227-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="2874132227-24">{</span><span class="n">Res</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="2874132227-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">handle_call</span><span class="p" data-group-id="2874132227-25">(</span><span class="n">Req</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2874132227-25">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2874132227-26">{</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="2874132227-26">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="2874132227-27">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="2874132227-27">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2874132227-28">{</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2874132227-28">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">State2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">handle_cast</span><span class="p" data-group-id="2874132227-29">(</span><span class="n">Req</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2874132227-29">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="2874132227-30">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="2874132227-30">)</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>And a callback module <code class="inline">ch2.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6818563174-1">(</span><span class="ss">ch2</span><span class="p" data-group-id="6818563174-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6818563174-2">(</span><span class="p" data-group-id="6818563174-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6818563174-3">]</span><span class="p" data-group-id="6818563174-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6818563174-4">(</span><span class="p" data-group-id="6818563174-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6818563174-5">]</span><span class="p" data-group-id="6818563174-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6818563174-6">(</span><span class="p" data-group-id="6818563174-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6818563174-7">]</span><span class="p" data-group-id="6818563174-6">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="6818563174-8">(</span><span class="p" data-group-id="6818563174-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="6818563174-9">(</span><span class="ss">ch2</span><span class="p" data-group-id="6818563174-9">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="6818563174-10">(</span><span class="p" data-group-id="6818563174-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="6818563174-11">(</span><span class="ss">ch2</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="6818563174-11">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="6818563174-12">(</span><span class="n">Ch</span><span class="p" data-group-id="6818563174-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="6818563174-13">(</span><span class="ss">ch2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6818563174-14">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="6818563174-14">}</span><span class="p" data-group-id="6818563174-13">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="2625608772-15">(</span><span class="p" data-group-id="2625608772-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">channels</span><span class="p" data-group-id="2625608772-16">(</span><span class="p" data-group-id="2625608772-16">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="6818563174-15">(</span><span class="p" data-group-id="6818563174-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">channels</span><span class="p" data-group-id="6818563174-16">(</span><span class="p" data-group-id="6818563174-16">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="2625608772-17">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2625608772-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">alloc</span><span class="p" data-group-id="2625608772-18">(</span><span class="n">Chs</span><span class="p" data-group-id="2625608772-18">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% =&gt; {Ch,Chs2}</span><span class="w">
│ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="6818563174-17">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6818563174-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">alloc</span><span class="p" data-group-id="6818563174-18">(</span><span class="n">Chs</span><span class="p" data-group-id="6818563174-18">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% =&gt; {Ch,Chs2}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="2625608772-19">(</span><span class="p" data-group-id="2625608772-20">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2625608772-20">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2625608772-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">free</span><span class="p" data-group-id="2625608772-21">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2625608772-21">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% =&gt; Chs2</span></code></pre><p>Notice the following:</p><ul><li>The code in <code class="inline">server</code> can be reused to build many different servers.</li><li>The server name, in this example the atom <code class="inline">ch2</code>, is hidden from the users of
│ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="6818563174-19">(</span><span class="p" data-group-id="6818563174-20">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="6818563174-20">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6818563174-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">free</span><span class="p" data-group-id="6818563174-21">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6818563174-21">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% =&gt; Chs2</span></code></pre><p>Notice the following:</p><ul><li>The code in <code class="inline">server</code> can be reused to build many different servers.</li><li>The server name, in this example the atom <code class="inline">ch2</code>, is hidden from the users of
│ │ │  the client functions. This means that the name can be changed without
│ │ │  affecting them.</li><li>The protocol (messages sent to and received from the server) is also hidden.
│ │ │  This is good programming practice and allows one to change the protocol
│ │ │  without changing the code using the interface functions.</li><li>The functionality of <code class="inline">server</code> can be extended without having to change <code class="inline">ch2</code>
│ │ │  or any other callback module.</li></ul><p>In <code class="inline">ch1.erl</code> and <code class="inline">ch2.erl</code> above, the implementation of <code class="inline">channels/0</code>, <code class="inline">alloc/1</code>,
│ │ │  and <code class="inline">free/2</code> has been intentionally left out, as it is not relevant to the
│ │ │  example. For completeness, one way to write these functions is given below. This
│ │ │  is an example only, a realistic implementation must be able to handle situations
│ │ │ -like running out of channels to allocate, and so on.</p><p><a href="" id="channels-implementation"></a></p><pre><code class="makeup erlang" translate="no"><span class="nf">channels</span><span class="p" data-group-id="2595888410-1">(</span><span class="p" data-group-id="2595888410-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="2595888410-2">{</span><span class="p">_</span><span class="n">Allocated</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2595888410-3">[</span><span class="p" data-group-id="2595888410-3">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Free</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="2595888410-4">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">100</span><span class="p" data-group-id="2595888410-4">)</span><span class="p" data-group-id="2595888410-2">}</span><span class="p">.</span><span class="w">
│ │ │ +like running out of channels to allocate, and so on.</p><p><a href="" id="channels-implementation"></a></p><pre><code class="makeup erlang" translate="no"><span class="nf">channels</span><span class="p" data-group-id="3433249860-1">(</span><span class="p" data-group-id="3433249860-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="3433249860-2">{</span><span class="p">_</span><span class="n">Allocated</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3433249860-3">[</span><span class="p" data-group-id="3433249860-3">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Free</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="3433249860-4">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">100</span><span class="p" data-group-id="3433249860-4">)</span><span class="p" data-group-id="3433249860-2">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="2595888410-5">(</span><span class="p" data-group-id="2595888410-6">{</span><span class="n">Allocated</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2595888410-7">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2595888410-7">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">_</span><span class="n">Free</span><span class="p" data-group-id="2595888410-6">}</span><span class="p" data-group-id="2595888410-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="2595888410-8">{</span><span class="n">H</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2595888410-9">{</span><span class="p" data-group-id="2595888410-10">[</span><span class="n">H</span><span class="p">|</span><span class="n">Allocated</span><span class="p" data-group-id="2595888410-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="2595888410-9">}</span><span class="p" data-group-id="2595888410-8">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="3433249860-5">(</span><span class="p" data-group-id="3433249860-6">{</span><span class="n">Allocated</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3433249860-7">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3433249860-7">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">_</span><span class="n">Free</span><span class="p" data-group-id="3433249860-6">}</span><span class="p" data-group-id="3433249860-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="3433249860-8">{</span><span class="n">H</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3433249860-9">{</span><span class="p" data-group-id="3433249860-10">[</span><span class="n">H</span><span class="p">|</span><span class="n">Allocated</span><span class="p" data-group-id="3433249860-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="3433249860-9">}</span><span class="p" data-group-id="3433249860-8">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="2595888410-11">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2595888410-12">{</span><span class="n">Alloc</span><span class="p">,</span><span class="w"> </span><span class="n">Free</span><span class="p" data-group-id="2595888410-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Channels</span><span class="p" data-group-id="2595888410-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="2595888410-13">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="2595888410-13">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="3433249860-11">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3433249860-12">{</span><span class="n">Alloc</span><span class="p">,</span><span class="w"> </span><span class="n">Free</span><span class="p" data-group-id="3433249860-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Channels</span><span class="p" data-group-id="3433249860-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="3433249860-13">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="3433249860-13">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │        </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="2595888410-14">{</span><span class="nc">lists</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="2595888410-15">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="2595888410-15">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2595888410-16">[</span><span class="n">Ch</span><span class="p">|</span><span class="n">Free</span><span class="p" data-group-id="2595888410-16">]</span><span class="p" data-group-id="2595888410-14">}</span><span class="p">;</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="3433249860-14">{</span><span class="nc">lists</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="3433249860-15">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="3433249860-15">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3433249860-16">[</span><span class="n">Ch</span><span class="p">|</span><span class="n">Free</span><span class="p" data-group-id="3433249860-16">]</span><span class="p" data-group-id="3433249860-14">}</span><span class="p">;</span><span class="w">
│ │ │        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │           </span><span class="n">Channels</span><span class="w">
│ │ │     </span><span class="k">end</span><span class="p">.</span></code></pre><p>Code written without using behaviours can be more efficient, but the increased
│ │ │  efficiency is at the expense of generality. The ability to manage all
│ │ │  applications in the system in a consistent manner is important.</p><p>Using behaviours also makes it easier to read and understand code written by
│ │ │  other programmers. Improvised programming structures, while possibly more
│ │ │  efficient, are always more difficult to understand.</p><p>The <code class="inline">server</code> module corresponds, greatly simplified, to the Erlang/OTP behaviour
│ │ │  <code class="inline">gen_server</code>.</p><p>The standard Erlang/OTP behaviours are:</p><ul><li><p><a href="gen_server_concepts.html">gen_server</a></p><p>For implementing the server of a client-server relation</p></li><li><p><a href="statem.html">gen_statem</a></p><p>For implementing state machines</p></li><li><p><a href="events.html">gen_event</a></p><p>For implementing event handling functionality</p></li><li><p><a href="sup_princ.html">supervisor</a></p><p>For implementing a supervisor in a supervision tree</p></li></ul><p>The compiler understands the module attribute <code class="inline">-behaviour(Behaviour)</code> and issues
│ │ │ -warnings about missing callback functions, for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7921289049-1">(</span><span class="ss">chs3</span><span class="p" data-group-id="7921289049-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="7921289049-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="7921289049-2">)</span><span class="p">.</span><span class="w">
│ │ │ +warnings about missing callback functions, for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5251444349-1">(</span><span class="ss">chs3</span><span class="p" data-group-id="5251444349-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="5251444349-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="5251444349-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">c</span><span class="p" data-group-id="7921289049-3">(</span><span class="ss">chs3</span><span class="p" data-group-id="7921289049-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">c</span><span class="p" data-group-id="5251444349-3">(</span><span class="ss">chs3</span><span class="p" data-group-id="5251444349-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="o">/</span><span class="ss">chs3</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">10</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="ss">undefined</span><span class="w"> </span><span class="ss">call</span><span class="o">-</span><span class="ss">back</span><span class="w"> </span><span class="ss">function</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7921289049-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">chs3</span><span class="p" data-group-id="7921289049-4">}</span></code></pre><h2 id="applications" class="section-heading">
│ │ │ +</span><span class="p" data-group-id="5251444349-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">chs3</span><span class="p" data-group-id="5251444349-4">}</span></code></pre><h2 id="applications" class="section-heading">
│ │ │    <a href="#applications" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Applications</span>
│ │ │  </h2>
│ │ │  <p>Erlang/OTP comes with a number of components, each implementing some specific
│ │ │  functionality. Components are with Erlang/OTP terminology called <em>applications</em>.
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/distributed.html
│ │ │ @@ -143,25 +143,25 @@
│ │ │  <p>A <em>node</em> is an executing Erlang runtime system that has been given a name, using
│ │ │  the command-line flag <a href="../../erts-17.0/doc/html/erl_cmd.html#name"><code class="inline">-name</code></a> (long names) or
│ │ │  <a href="../../erts-17.0/doc/html/erl_cmd.html#sname"><code class="inline">-sname</code></a> (short names).</p><p>The format of the node name is an atom <code class="inline">name@host</code>. <code class="inline">name</code> is the name given by
│ │ │  the user, and consists of alphanumerics, <code class="inline">-</code>, <code class="inline">_</code>, and <code class="inline">\</code>.
│ │ │  <code class="inline">host</code> is the full host name if long names are used, or the first part
│ │ │  of the host name if short names are used. Function <a href="../../erts-17.0/doc/html/erlang.html#node/0"><code class="inline">node()</code></a>
│ │ │  returns the name of the node.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -name dilbert</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0400198301-1">(</span><span class="ss">dilbert@uab</span><span class="p">.</span><span class="ss">ericsson</span><span class="p">.</span><span class="ss">se</span><span class="p" data-group-id="0400198301-1">)</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">node</span><span class="p" data-group-id="0400198301-2">(</span><span class="p" data-group-id="0400198301-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6560930544-1">(</span><span class="ss">dilbert@uab</span><span class="p">.</span><span class="ss">ericsson</span><span class="p">.</span><span class="ss">se</span><span class="p" data-group-id="6560930544-1">)</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">node</span><span class="p" data-group-id="6560930544-2">(</span><span class="p" data-group-id="6560930544-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">&#39;dilbert@uab.ericsson.se&#39;</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">% erl -sname dilbert</span><span class="w">
│ │ │ -</span><span class="gp unselectable">(dilbert@uab)1&gt; </span><span class="nf">node</span><span class="p" data-group-id="0400198301-3">(</span><span class="p" data-group-id="0400198301-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">(dilbert@uab)1&gt; </span><span class="nf">node</span><span class="p" data-group-id="6560930544-3">(</span><span class="p" data-group-id="6560930544-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">dilbert@uab</span></code></pre><p>The node name can also be given at runtime by calling <a href="../../lib/kernel-11.0/doc/html/net_kernel.html#start/1"><code class="inline">net_kernel:start/1</code></a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl</span><span class="w">
│ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nf">node</span><span class="p" data-group-id="5843039616-1">(</span><span class="p" data-group-id="5843039616-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nf">node</span><span class="p" data-group-id="3783729994-1">(</span><span class="p" data-group-id="3783729994-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">nonode@nohost</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">net_kernel</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="5843039616-2">(</span><span class="p" data-group-id="5843039616-3">[</span><span class="ss">dilbert</span><span class="p">,</span><span class="ss">shortnames</span><span class="p" data-group-id="5843039616-3">]</span><span class="p" data-group-id="5843039616-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5843039616-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.102</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5843039616-4">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">(dilbert@uab)3&gt; </span><span class="nf">node</span><span class="p" data-group-id="5843039616-5">(</span><span class="p" data-group-id="5843039616-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">net_kernel</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="3783729994-2">(</span><span class="p" data-group-id="3783729994-3">[</span><span class="ss">dilbert</span><span class="p">,</span><span class="ss">shortnames</span><span class="p" data-group-id="3783729994-3">]</span><span class="p" data-group-id="3783729994-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3783729994-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.102</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="3783729994-4">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">(dilbert@uab)3&gt; </span><span class="nf">node</span><span class="p" data-group-id="3783729994-5">(</span><span class="p" data-group-id="3783729994-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">dilbert@uab</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>A node with a long node name cannot communicate with a node with a short node
│ │ │  name.</p></section><h2 id="node-connections" class="section-heading">
│ │ │    <a href="#node-connections" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Node Connections</span>
│ │ │  </h2>
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/distributed_applications.html
│ │ │ @@ -150,36 +150,36 @@
│ │ │  (within the time-out specified by <code class="inline">sync_nodes_timeout</code>).</li><li><p><code class="inline">sync_nodes_timeout = integer() | infinity</code> - Specifies how many milliseconds
│ │ │  to wait for the other nodes to start.</p></li></ul><p>When started, the node waits for all nodes specified by <code class="inline">sync_nodes_mandatory</code>
│ │ │  and <code class="inline">sync_nodes_optional</code> to come up. When all nodes are up, or when all
│ │ │  mandatory nodes are up and the time specified by <code class="inline">sync_nodes_timeout</code> has
│ │ │  elapsed, all applications start. If not all mandatory nodes are up, the node
│ │ │  terminates.</p><p><em>Example:</em></p><p>An application <code class="inline">myapp</code> is to run at the node <code class="inline">cp1@cave</code>. If this node goes down,
│ │ │  <code class="inline">myapp</code> is to be restarted at <code class="inline">cp2@cave</code> or <code class="inline">cp3@cave</code>. A system configuration
│ │ │ -file <code class="inline">cp1.config</code> for <code class="inline">cp1@cave</code> can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3635884467-1">[</span><span class="p" data-group-id="3635884467-2">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3635884467-3">[</span><span class="p" data-group-id="3635884467-4">{</span><span class="ss">distributed</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3635884467-5">[</span><span class="p" data-group-id="3635884467-6">{</span><span class="ss">myapp</span><span class="p">,</span><span class="w"> </span><span class="mi">5000</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3635884467-7">[</span><span class="ss">cp1@cave</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3635884467-8">{</span><span class="ss">cp2@cave</span><span class="p">,</span><span class="w"> </span><span class="ss">cp3@cave</span><span class="p" data-group-id="3635884467-8">}</span><span class="p" data-group-id="3635884467-7">]</span><span class="p" data-group-id="3635884467-6">}</span><span class="p" data-group-id="3635884467-5">]</span><span class="p" data-group-id="3635884467-4">}</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="3635884467-9">{</span><span class="ss">sync_nodes_mandatory</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3635884467-10">[</span><span class="ss">cp2@cave</span><span class="p">,</span><span class="w"> </span><span class="ss">cp3@cave</span><span class="p" data-group-id="3635884467-10">]</span><span class="p" data-group-id="3635884467-9">}</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="3635884467-11">{</span><span class="ss">sync_nodes_timeout</span><span class="p">,</span><span class="w"> </span><span class="mi">5000</span><span class="p" data-group-id="3635884467-11">}</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3635884467-3">]</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3635884467-2">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3635884467-1">]</span><span class="p">.</span></code></pre><p>The system configuration files for <code class="inline">cp2@cave</code> and <code class="inline">cp3@cave</code> are identical,
│ │ │ +file <code class="inline">cp1.config</code> for <code class="inline">cp1@cave</code> can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8681921227-1">[</span><span class="p" data-group-id="8681921227-2">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8681921227-3">[</span><span class="p" data-group-id="8681921227-4">{</span><span class="ss">distributed</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8681921227-5">[</span><span class="p" data-group-id="8681921227-6">{</span><span class="ss">myapp</span><span class="p">,</span><span class="w"> </span><span class="mi">5000</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8681921227-7">[</span><span class="ss">cp1@cave</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8681921227-8">{</span><span class="ss">cp2@cave</span><span class="p">,</span><span class="w"> </span><span class="ss">cp3@cave</span><span class="p" data-group-id="8681921227-8">}</span><span class="p" data-group-id="8681921227-7">]</span><span class="p" data-group-id="8681921227-6">}</span><span class="p" data-group-id="8681921227-5">]</span><span class="p" data-group-id="8681921227-4">}</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="8681921227-9">{</span><span class="ss">sync_nodes_mandatory</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8681921227-10">[</span><span class="ss">cp2@cave</span><span class="p">,</span><span class="w"> </span><span class="ss">cp3@cave</span><span class="p" data-group-id="8681921227-10">]</span><span class="p" data-group-id="8681921227-9">}</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="8681921227-11">{</span><span class="ss">sync_nodes_timeout</span><span class="p">,</span><span class="w"> </span><span class="mi">5000</span><span class="p" data-group-id="8681921227-11">}</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8681921227-3">]</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8681921227-2">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8681921227-1">]</span><span class="p">.</span></code></pre><p>The system configuration files for <code class="inline">cp2@cave</code> and <code class="inline">cp3@cave</code> are identical,
│ │ │  except for the list of mandatory nodes, which is to be <code class="inline">[cp1@cave, cp3@cave]</code>
│ │ │  for <code class="inline">cp2@cave</code> and <code class="inline">[cp1@cave, cp2@cave]</code> for <code class="inline">cp3@cave</code>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>All involved nodes must have the same value for <code class="inline">distributed</code> and
│ │ │  <code class="inline">sync_nodes_timeout</code>. Otherwise the system behavior is undefined.</p></section><h2 id="starting-and-stopping-distributed-applications" class="section-heading">
│ │ │    <a href="#starting-and-stopping-distributed-applications" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Starting and Stopping Distributed Applications</span>
│ │ │  </h2>
│ │ │  <p>When all involved (mandatory) nodes have been started, the distributed
│ │ │  application can be started by calling <code class="inline">application:start(Application)</code> at <em>all
│ │ │  of these nodes.</em></p><p>A boot script (see <a href="release_structure.html">Releases</a>) can be used that
│ │ │  automatically starts the application.</p><p>The application is started at the first operational node that is listed in the
│ │ │  list of nodes in the <code class="inline">distributed</code> configuration parameter. The application is
│ │ │  started as usual. That is, an application master is created and calls the
│ │ │ -application callback function:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="6002463695-1">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="6002463695-1">)</span></code></pre><p>Example:</p><p>Continuing the example from the previous section, the three nodes are started,
│ │ │ +application callback function:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="4199388008-1">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="4199388008-1">)</span></code></pre><p>Example:</p><p>Continuing the example from the previous section, the three nodes are started,
│ │ │  specifying the system configuration file:</p><pre><code class="text">&gt; erl -sname cp1 -config cp1
│ │ │  &gt; erl -sname cp2 -config cp2
│ │ │  &gt; erl -sname cp3 -config cp3</code></pre><p>When all nodes are operational, <code class="inline">myapp</code> can be started. This is achieved by
│ │ │  calling <code class="inline">application:start(myapp)</code> at all three nodes. It is then started at
│ │ │  <code class="inline">cp1</code>, as shown in the following figure:</p><p><a href="" id="dist1"></a></p><p><img src="assets/dist1.gif" alt="Application myapp - Situation 1" title="Application myapp - Situation 1"/></p><p>Similarly, the application must be stopped by calling
│ │ │  <code class="inline">application:stop(Application)</code> at all involved nodes.</p><h2 id="failover" class="section-heading">
│ │ │    <a href="#failover" class="hover-link">
│ │ │ @@ -187,30 +187,30 @@
│ │ │    </a>
│ │ │    <span class="text">Failover</span>
│ │ │  </h2>
│ │ │  <p>If the node where the application is running goes down, the application is
│ │ │  restarted (after the specified time-out) at the first operational node that is
│ │ │  listed in the list of nodes in the <code class="inline">distributed</code> configuration parameter. This
│ │ │  is called a <em>failover</em>.</p><p>The application is started the normal way at the new node, that is, by the
│ │ │ -application master calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="7256827493-1">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="7256827493-1">)</span></code></pre><p>An exception is if the application has the <code class="inline">start_phases</code> key defined (see
│ │ │ +application master calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="6803889039-1">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="6803889039-1">)</span></code></pre><p>An exception is if the application has the <code class="inline">start_phases</code> key defined (see
│ │ │  <a href="included_applications.html">Included Applications</a>). The application is then
│ │ │ -instead started by calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="7256938945-1">(</span><span class="p" data-group-id="7256938945-2">{</span><span class="ss">failover</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="7256938945-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="7256938945-1">)</span></code></pre><p>Here <code class="inline">Node</code> is the terminated node.</p><p><em>Example:</em></p><p>If <code class="inline">cp1</code> goes down, the system checks which one of the other nodes, <code class="inline">cp2</code> or
│ │ │ +instead started by calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="9790774126-1">(</span><span class="p" data-group-id="9790774126-2">{</span><span class="ss">failover</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="9790774126-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="9790774126-1">)</span></code></pre><p>Here <code class="inline">Node</code> is the terminated node.</p><p><em>Example:</em></p><p>If <code class="inline">cp1</code> goes down, the system checks which one of the other nodes, <code class="inline">cp2</code> or
│ │ │  <code class="inline">cp3</code>, has the least number of running applications, but waits for 5 seconds for
│ │ │  <code class="inline">cp1</code> to restart. If <code class="inline">cp1</code> does not restart and <code class="inline">cp2</code> runs fewer applications
│ │ │  than <code class="inline">cp3</code>, <code class="inline">myapp</code> is restarted on <code class="inline">cp2</code>.</p><p><a href="" id="dist2"></a></p><p><img src="assets/dist2.gif" alt="Application myapp - Situation 2" title="Application myapp - Situation 2"/></p><p>Suppose now that <code class="inline">cp2</code> goes also down and does not restart within 5 seconds.
│ │ │  <code class="inline">myapp</code> is now restarted on <code class="inline">cp3</code>.</p><p><a href="" id="dist3"></a></p><p><img src="assets/dist3.gif" alt="Application myapp - Situation 3" title="Application myapp - Situation 3"/></p><h2 id="takeover" class="section-heading">
│ │ │    <a href="#takeover" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Takeover</span>
│ │ │  </h2>
│ │ │  <p>If a node is started, which has higher priority according to <code class="inline">distributed</code> than
│ │ │  the node where a distributed application is running, the application is
│ │ │  restarted at the new node and stopped at the old node. This is called a
│ │ │ -<em>takeover</em>.</p><p>The application is started by the application master calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="3374587685-1">(</span><span class="p" data-group-id="3374587685-2">{</span><span class="ss">takeover</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="3374587685-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="3374587685-1">)</span></code></pre><p>Here <code class="inline">Node</code> is the old node.</p><p><em>Example:</em></p><p>If <code class="inline">myapp</code> is running at <code class="inline">cp3</code>, and if <code class="inline">cp2</code> now restarts, it does not restart
│ │ │ +<em>takeover</em>.</p><p>The application is started by the application master calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="7954412035-1">(</span><span class="p" data-group-id="7954412035-2">{</span><span class="ss">takeover</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="7954412035-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="7954412035-1">)</span></code></pre><p>Here <code class="inline">Node</code> is the old node.</p><p><em>Example:</em></p><p>If <code class="inline">myapp</code> is running at <code class="inline">cp3</code>, and if <code class="inline">cp2</code> now restarts, it does not restart
│ │ │  <code class="inline">myapp</code>, as the order between the <code class="inline">cp2</code> and <code class="inline">cp3</code> nodes is undefined.</p><p><a href="" id="dist4"></a></p><p><img src="assets/dist4.gif" alt="Application myapp - Situation 4" title="Application myapp - Situation 4"/></p><p>However, if <code class="inline">cp1</code> also restarts, the function <a href="../../lib/kernel-11.0/doc/html/application.html#takeover/2"><code class="inline">application:takeover/2</code></a> moves
│ │ │  <code class="inline">myapp</code> to <code class="inline">cp1</code>, as <code class="inline">cp1</code> has a higher priority than <code class="inline">cp3</code> for this
│ │ │  application. In this case, <code class="inline">Module:start({takeover, cp3@cave}, StartArgs)</code> is
│ │ │  executed at <code class="inline">cp1</code> to start the application.</p><p><a href="" id="dist5"></a></p><p><img src="assets/dist5.gif" alt="Application myapp - Situation 5" title="Application myapp - Situation 5"/></p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/documentation.html
│ │ │ @@ -112,23 +112,23 @@
│ │ │        </a>
│ │ │  
│ │ │  
│ │ │      <span>Documentation</span>
│ │ │    </h1>
│ │ │  
│ │ │  <p>Documentation in Erlang is done through the <code class="inline">-moduledoc</code> and <code class="inline">-doc</code>
│ │ │ -<a href="modules.html#module-attributes">attributes</a>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2914315257-1">(</span><span class="ss">arith</span><span class="p" data-group-id="2914315257-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<a href="modules.html#module-attributes">attributes</a>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1612074409-1">(</span><span class="ss">arith</span><span class="p" data-group-id="1612074409-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │  A module for basic arithmetic.
│ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2914315257-2">(</span><span class="p" data-group-id="2914315257-3">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2914315257-3">]</span><span class="p" data-group-id="2914315257-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1612074409-2">(</span><span class="p" data-group-id="1612074409-3">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1612074409-3">]</span><span class="p" data-group-id="1612074409-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;Adds two numbers.&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="2914315257-4">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="2914315257-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>The <code class="inline">-moduledoc</code> attribute has to be located before the first <code class="inline">-doc</code> attribute
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="1612074409-4">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="1612074409-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>The <code class="inline">-moduledoc</code> attribute has to be located before the first <code class="inline">-doc</code> attribute
│ │ │  or function declaration. It documents the overall purpose of the module.</p><p>The <code class="inline">-doc</code> attribute always precedes the <a href="ref_man_functions.html">function</a> or
│ │ │  <a href="modules.html#module-attributes">attribute</a> it documents. The
│ │ │  attributes that can be documented are
│ │ │  <a href="typespec.html#type-declarations-of-user-defined-types">user-defined types</a>
│ │ │  (<code class="inline">-type</code> and <code class="inline">-opaque</code>) and
│ │ │  <a href="modules.html#behaviour-module-attribute">behaviour module attributes</a>
│ │ │  (<code class="inline">-callback</code>).</p><p>By default, the format used for documentation attributes is
│ │ │ @@ -140,55 +140,55 @@
│ │ │  <a href="modules.html#documentation-attributes">Documentation Attributes</a>.</p><p><code class="inline">-doc</code> attributes have been available since Erlang/OTP 27.</p><h2 id="documentation-metadata" class="section-heading">
│ │ │    <a href="#documentation-metadata" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Documentation metadata</span>
│ │ │  </h2>
│ │ │  <p>It is possible to add metadata to the documentation entry. You do this by adding
│ │ │ -a <code class="inline">-moduledoc</code> or <code class="inline">-doc</code> attribute with a map as argument. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1928322631-1">(</span><span class="ss">arith</span><span class="p" data-group-id="1928322631-1">)</span><span class="p">.</span><span class="w">
│ │ │ +a <code class="inline">-moduledoc</code> or <code class="inline">-doc</code> attribute with a map as argument. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9406934823-1">(</span><span class="ss">arith</span><span class="p" data-group-id="9406934823-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │  A module for basic arithmetic.
│ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="1928322631-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="1928322631-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="9406934823-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="9406934823-2">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1928322631-3">(</span><span class="p" data-group-id="1928322631-4">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1928322631-4">]</span><span class="p" data-group-id="1928322631-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9406934823-3">(</span><span class="p" data-group-id="9406934823-4">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9406934823-4">]</span><span class="p" data-group-id="9406934823-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;Adds two numbers.&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="1928322631-5">(</span><span class="p" data-group-id="1928322631-6">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="1928322631-6">}</span><span class="p" data-group-id="1928322631-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="1928322631-7">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="1928322631-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>The metadata is used by documentation tools to provide extra information to the
│ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="9406934823-5">(</span><span class="p" data-group-id="9406934823-6">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="9406934823-6">}</span><span class="p" data-group-id="9406934823-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="9406934823-7">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="9406934823-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>The metadata is used by documentation tools to provide extra information to the
│ │ │  user. There can be multiple metadata documentation entries, in which case the
│ │ │  maps will be merged with the latest taking precedence if there are duplicate
│ │ │  keys. Example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;Adds two numbers.&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="2001351127-1">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">author</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p" data-group-id="2001351127-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="2001351127-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="2001351127-2">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="2001351127-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="2001351127-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>This will result in a metadata entry of <code class="inline">#{since =&gt; &quot;2.0&quot;, author =&gt; &quot;Joe&quot;}</code>.</p><p>The keys and values in the metadata map can be any type, but it is recommended
│ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="7093962295-1">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">author</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p" data-group-id="7093962295-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="7093962295-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="7093962295-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="7093962295-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="7093962295-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>This will result in a metadata entry of <code class="inline">#{since =&gt; &quot;2.0&quot;, author =&gt; &quot;Joe&quot;}</code>.</p><p>The keys and values in the metadata map can be any type, but it is recommended
│ │ │  that only <a href="data_types.html#atom">atoms</a> are used for keys and
│ │ │  <a href="data_types.html#string">strings</a> for the values.</p><h2 id="external-documentation-files" class="section-heading">
│ │ │    <a href="#external-documentation-files" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">External documentation files</span>
│ │ │  </h2>
│ │ │  <p>The <code class="inline">-moduledoc</code> and <code class="inline">-doc</code> attributes can also be placed in external files. To do so, use
│ │ │  <code class="inline">-doc {file, &quot;path/to/doc.md&quot;}</code> to point to the documentation. The path used is
│ │ │  relative to the file where the <code class="inline">-doc</code> attribute is located. For example:</p><pre><code class="markdown">%% doc/add.md
│ │ │  Adds two numbers.</code></pre><p>and</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% src/arith.erl</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="4530162116-1">(</span><span class="p" data-group-id="4530162116-2">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;../doc/add.md&quot;</span><span class="p" data-group-id="4530162116-2">}</span><span class="p" data-group-id="4530162116-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="4530162116-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="4530162116-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><h2 id="documenting-a-module" class="section-heading">
│ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="3225640844-1">(</span><span class="p" data-group-id="3225640844-2">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;../doc/add.md&quot;</span><span class="p" data-group-id="3225640844-2">}</span><span class="p" data-group-id="3225640844-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="3225640844-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="3225640844-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><h2 id="documenting-a-module" class="section-heading">
│ │ │    <a href="#documenting-a-module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Documenting a module</span>
│ │ │  </h2>
│ │ │  <p>The module description should include details on how to use the API and examples
│ │ │  of the different functions working together. Here is a good place to use images
│ │ │  and other diagrams to better show the usage of the module. Instead of writing a
│ │ │  long text in the <code class="inline">-moduledoc</code> attribute, it could be better to break it out into
│ │ │  an external page.</p><p>The <code class="inline">-moduledoc</code> attribute should start with a short paragraph describing the
│ │ │ -module and then go into greater detail. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7961295181-1">(</span><span class="ss">arith</span><span class="p" data-group-id="7961295181-1">)</span><span class="p">.</span><span class="w">
│ │ │ +module and then go into greater detail. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7444756399-1">(</span><span class="ss">arith</span><span class="p" data-group-id="7444756399-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="s">&quot;
│ │ │     A module for basic arithmetic.
│ │ │  
│ │ │     This module can be used to add and subtract values. For example:
│ │ │  
│ │ │     ```erlang
│ │ │     1&gt; arith:subtract(arith:add(2, 3), 1).
│ │ │ @@ -203,96 +203,96 @@
│ │ │  <p>There are three reserved metadata keys for <code class="inline">-moduledoc</code>:</p><ul><li><code class="inline">since =&gt; unicode:chardata()</code> - Shows in which version of the application the module was added.
│ │ │  If this is added, all functions, types, and callbacks within will also receive
│ │ │  the same <code class="inline">since</code> value unless specified in the metadata of the function, type
│ │ │  or callback.</li><li><code class="inline">deprecated =&gt; unicode:chardata()</code> - Shows a text in the documentation explaining that it is
│ │ │  deprecated and what to use instead.</li><li><code class="inline">format =&gt; unicode:chardata()</code> - The format to use for all documentation in this module. The
│ │ │  default is <code class="inline">text/markdown</code>. It should be written using the
│ │ │  <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types">mime type</a>
│ │ │ -of the format.</li></ul><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="0258672377-1">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;../doc/arith.asciidoc&quot;</span><span class="p" data-group-id="0258672377-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="0258672377-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;0.1&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">format</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;text/asciidoc&quot;</span><span class="p" data-group-id="0258672377-2">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="0258672377-3">#{</span><span class="ss">deprecated</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;Use the Erlang arithmetic operators instead.&quot;</span><span class="p" data-group-id="0258672377-3">}</span><span class="p">.</span></code></pre><h2 id="documenting-functions-user-defined-types-and-callbacks" class="section-heading">
│ │ │ +of the format.</li></ul><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="5835085214-1">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;../doc/arith.asciidoc&quot;</span><span class="p" data-group-id="5835085214-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="5835085214-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;0.1&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">format</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;text/asciidoc&quot;</span><span class="p" data-group-id="5835085214-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="5835085214-3">#{</span><span class="ss">deprecated</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;Use the Erlang arithmetic operators instead.&quot;</span><span class="p" data-group-id="5835085214-3">}</span><span class="p">.</span></code></pre><h2 id="documenting-functions-user-defined-types-and-callbacks" class="section-heading">
│ │ │    <a href="#documenting-functions-user-defined-types-and-callbacks" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Documenting functions, user-defined types, and callbacks</span>
│ │ │  </h2>
│ │ │  <p>Functions, types, and callbacks can be documented using the <code class="inline">-doc</code> attribute.
│ │ │  Each entry should start with a short paragraph describing the purpose of the entity,
│ │ │  and then go into greater detail if needed.</p><p>It is not recommended to include images or diagrams in this documentation as it
│ │ │  is used by IDEs and <a href="../../lib/stdlib-8.0/doc/html/c.html#h/1"><code class="inline">c:h/1</code></a> to show the documentation to the user.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │  A number that can be used by the arith module.
│ │ │  
│ │ │  We use a special number here so that we know
│ │ │  that this number comes from this module.
│ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="6695948469-1">(</span><span class="p" data-group-id="6695948469-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="6695948469-2">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">number</span><span class="p" data-group-id="6695948469-3">(</span><span class="p" data-group-id="6695948469-3">)</span><span class="p" data-group-id="6695948469-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0755937524-1">(</span><span class="p" data-group-id="0755937524-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0755937524-2">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">number</span><span class="p" data-group-id="0755937524-3">(</span><span class="p" data-group-id="0755937524-3">)</span><span class="p" data-group-id="0755937524-2">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │  Adds two numbers.
│ │ │  
│ │ │  ### Example:
│ │ │  
│ │ │  ```
│ │ │  1&gt; arith:add(arith:number(1), arith:number(2)). {arith, 3}
│ │ │  ```
│ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="6695948469-4">(</span><span class="nf">number</span><span class="p" data-group-id="6695948469-5">(</span><span class="p" data-group-id="6695948469-5">)</span><span class="p">,</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="6695948469-6">(</span><span class="p" data-group-id="6695948469-6">)</span><span class="p" data-group-id="6695948469-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="6695948469-7">(</span><span class="p" data-group-id="6695948469-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="6695948469-8">(</span><span class="p" data-group-id="6695948469-9">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="n">One</span><span class="p" data-group-id="6695948469-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6695948469-10">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="6695948469-10">}</span><span class="p" data-group-id="6695948469-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6695948469-11">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="6695948469-11">}</span><span class="p">.</span></code></pre><p>Examples in documentation can be tested using <a href="../../lib/common_test-1.31/doc/html/ct_doctest.html"><code class="inline">ct_doctest</code></a>.</p><h3 id="doc-metadata" class="section-heading">
│ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="0755937524-4">(</span><span class="nf">number</span><span class="p" data-group-id="0755937524-5">(</span><span class="p" data-group-id="0755937524-5">)</span><span class="p">,</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0755937524-6">(</span><span class="p" data-group-id="0755937524-6">)</span><span class="p" data-group-id="0755937524-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0755937524-7">(</span><span class="p" data-group-id="0755937524-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="0755937524-8">(</span><span class="p" data-group-id="0755937524-9">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="n">One</span><span class="p" data-group-id="0755937524-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0755937524-10">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="0755937524-10">}</span><span class="p" data-group-id="0755937524-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0755937524-11">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="0755937524-11">}</span><span class="p">.</span></code></pre><p>Examples in documentation can be tested using <a href="../../lib/common_test-1.31/doc/html/ct_doctest.html"><code class="inline">ct_doctest</code></a>.</p><h3 id="doc-metadata" class="section-heading">
│ │ │    <a href="#doc-metadata" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Doc metadata</span>
│ │ │  </h3>
│ │ │  <p>There are four reserved metadata keys for <code class="inline">-doc</code>:</p><ul><li><p><code class="inline">since =&gt; unicode:chardata()</code> - Shows in which version of the application the
│ │ │  function, type, or callback was added.</p></li><li><p><code class="inline">deprecated =&gt; unicode:chardata()</code> - Shows a text in the documentation
│ │ │  explaining that it is deprecated and what to use instead. The compiler will
│ │ │  automatically insert this key if there is a <code class="inline">-deprecated</code> attribute marking a
│ │ │  function as deprecated.</p></li><li><p><code class="inline">group =&gt; unicode:chardata()</code> - A group that the function, type, or callback belongs to.
│ │ │  It allows tooling, such as shell autocompletion and documentation generators, to list all
│ │ │  entries within the same group together, often using the group name as an indicator.</p></li><li><p><code class="inline">equiv =&gt; unicode:chardata() | F/A | F(...)</code> - Notes that this function is equivalent to
│ │ │  another function in this module. The equivalence can be described using either
│ │ │ -<code class="inline">Func/Arity</code>, <code class="inline">Func(Args)</code> or a <a href="../../lib/stdlib-8.0/doc/html/unicode.html#t:chardata/0">unicode string</a>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="1786124122-1">#{</span><span class="ss">equiv</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">add</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="1786124122-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="1786124122-2">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="1786124122-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="1786124122-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1786124122-4">[</span><span class="p" data-group-id="1786124122-4">]</span><span class="p" data-group-id="1786124122-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="1786124122-5">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="1786124122-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>or</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="9275342893-1">#{</span><span class="ss">equiv</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="9275342893-2">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9275342893-3">[</span><span class="p" data-group-id="9275342893-3">]</span><span class="p" data-group-id="9275342893-2">)</span><span class="p" data-group-id="9275342893-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="9275342893-4">(</span><span class="n">One</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9275342893-5">(</span><span class="p" data-group-id="9275342893-5">)</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9275342893-6">(</span><span class="p" data-group-id="9275342893-6">)</span><span class="p" data-group-id="9275342893-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9275342893-7">(</span><span class="p" data-group-id="9275342893-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="9275342893-8">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="9275342893-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="9275342893-9">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9275342893-10">[</span><span class="p" data-group-id="9275342893-10">]</span><span class="p" data-group-id="9275342893-9">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="9275342893-11">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="9275342893-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>The entry into the <a href="../../lib/kernel-11.0/doc/html/eep48_chapter.html">EEP-48</a> doc chunk metadata is
│ │ │ +<code class="inline">Func/Arity</code>, <code class="inline">Func(Args)</code> or a <a href="../../lib/stdlib-8.0/doc/html/unicode.html#t:chardata/0">unicode string</a>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="3671791854-1">#{</span><span class="ss">equiv</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">add</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="3671791854-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="3671791854-2">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="3671791854-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="3671791854-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3671791854-4">[</span><span class="p" data-group-id="3671791854-4">]</span><span class="p" data-group-id="3671791854-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="3671791854-5">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="3671791854-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>or</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="9007544473-1">#{</span><span class="ss">equiv</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="9007544473-2">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9007544473-3">[</span><span class="p" data-group-id="9007544473-3">]</span><span class="p" data-group-id="9007544473-2">)</span><span class="p" data-group-id="9007544473-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="9007544473-4">(</span><span class="n">One</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9007544473-5">(</span><span class="p" data-group-id="9007544473-5">)</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9007544473-6">(</span><span class="p" data-group-id="9007544473-6">)</span><span class="p" data-group-id="9007544473-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9007544473-7">(</span><span class="p" data-group-id="9007544473-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="9007544473-8">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="9007544473-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="9007544473-9">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9007544473-10">[</span><span class="p" data-group-id="9007544473-10">]</span><span class="p" data-group-id="9007544473-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="9007544473-11">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="9007544473-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>The entry into the <a href="../../lib/kernel-11.0/doc/html/eep48_chapter.html">EEP-48</a> doc chunk metadata is
│ │ │  the value converted to a string.</p></li><li><p><code class="inline">exported =&gt; boolean()</code> - A <a href="../../erts-17.0/doc/html/erlang.html#t:boolean/0"><code class="inline">boolean/0</code></a> signifying if the entry is <code class="inline">exported</code>
│ │ │  or not. This value is automatically set by the compiler and should not be set
│ │ │  by the user.</p></li></ul><h3 id="doc-signatures" class="section-heading">
│ │ │    <a href="#doc-signatures" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Doc signatures</span>
│ │ │  </h3>
│ │ │  <p>The doc signature is a short text shown to describe the function and its arguments.
│ │ │  By default, it is determined by looking at the names of the arguments in the
│ │ │ -<code class="inline">-spec</code> or function. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add</span><span class="p" data-group-id="2496625956-1">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="2496625956-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">-spec</code> or function. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add</span><span class="p" data-group-id="4018299613-1">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="4018299613-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">sub</span><span class="p" data-group-id="2496625956-2">(</span><span class="n">One</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="2496625956-3">(</span><span class="p" data-group-id="2496625956-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="2496625956-4">(</span><span class="p" data-group-id="2496625956-4">)</span><span class="p" data-group-id="2496625956-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="2496625956-5">(</span><span class="p" data-group-id="2496625956-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">sub</span><span class="p" data-group-id="2496625956-6">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2496625956-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">Y</span><span class="p">.</span></code></pre><p>will have a signature of <code class="inline">add(One, Two)</code> and <code class="inline">sub(One, Two)</code>.</p><p>For types or callbacks, the signature is derived from the type or callback
│ │ │ -specification. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="5008348883-1">(</span><span class="n">Value</span><span class="p" data-group-id="5008348883-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="5008348883-2">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="5008348883-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">sub</span><span class="p" data-group-id="4018299613-2">(</span><span class="n">One</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="4018299613-3">(</span><span class="p" data-group-id="4018299613-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="4018299613-4">(</span><span class="p" data-group-id="4018299613-4">)</span><span class="p" data-group-id="4018299613-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="4018299613-5">(</span><span class="p" data-group-id="4018299613-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">sub</span><span class="p" data-group-id="4018299613-6">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4018299613-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">Y</span><span class="p">.</span></code></pre><p>will have a signature of <code class="inline">add(One, Two)</code> and <code class="inline">sub(One, Two)</code>.</p><p>For types or callbacks, the signature is derived from the type or callback
│ │ │ +specification. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="5359092999-1">(</span><span class="n">Value</span><span class="p" data-group-id="5359092999-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="5359092999-2">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="5359092999-2">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% signature will be `number(Value)`</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="5008348883-3">(</span><span class="p" data-group-id="5008348883-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="5008348883-4">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="5008348883-5">(</span><span class="p" data-group-id="5008348883-5">)</span><span class="p" data-group-id="5008348883-4">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="5359092999-3">(</span><span class="p" data-group-id="5359092999-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="5359092999-4">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="5359092999-5">(</span><span class="p" data-group-id="5359092999-5">)</span><span class="p" data-group-id="5359092999-4">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% signature will be `number()`</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">increment</span><span class="p" data-group-id="5008348883-6">(</span><span class="n">In</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="5008348883-7">(</span><span class="p" data-group-id="5008348883-7">)</span><span class="p" data-group-id="5008348883-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Out</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">increment</span><span class="p" data-group-id="5359092999-6">(</span><span class="n">In</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="5359092999-7">(</span><span class="p" data-group-id="5359092999-7">)</span><span class="p" data-group-id="5359092999-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Out</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% signature will be `increment(In)`</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">increment</span><span class="p" data-group-id="5008348883-8">(</span><span class="n">In</span><span class="p" data-group-id="5008348883-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Out</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">In</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="5008348883-9">(</span><span class="p" data-group-id="5008348883-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">increment</span><span class="p" data-group-id="5359092999-8">(</span><span class="n">In</span><span class="p" data-group-id="5359092999-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Out</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">In</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="5359092999-9">(</span><span class="p" data-group-id="5359092999-9">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% signature will be `increment(In)`</span></code></pre><p>If it is not possible to &quot;easily&quot; figure out a nice signature from the code, the
│ │ │  MFA syntax is used instead. For example: <code class="inline">add/2</code>, <code class="inline">number/1</code>, <code class="inline">increment/1</code>.</p><p>It is possible to supply a custom signature by placing it as the first line of the
│ │ │  <code class="inline">-doc</code> attribute. The provided signature must be in the form of a function
│ │ │  declaration up until the <code class="inline">-&gt;</code>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │  add(One, Two)
│ │ │  
│ │ │  Adds two numbers.
│ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="7935055838-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="7935055838-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p">.</span></code></pre><p>This will create the signature <code class="inline">add(One, Two)</code>. The signature will be removed from the
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="9220783962-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="9220783962-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p">.</span></code></pre><p>This will create the signature <code class="inline">add(One, Two)</code>. The signature will be removed from the
│ │ │  documentation string, so in the example above only the text <code class="inline">&quot;Adds two numbers&quot;</code>
│ │ │  will be part of the documentation. This works for functions, types, and
│ │ │  callbacks.</p><h2 id="links-in-markdown" class="section-heading">
│ │ │    <a href="#links-in-markdown" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Links in Markdown</span>
│ │ │ @@ -330,28 +330,28 @@
│ │ │  modules. That is, modules that should be used by other applications and modules
│ │ │  that should not. By default, all modules in an application are visible, but by
│ │ │  setting <code class="inline">-moduledoc false.</code>, specific modules can be hidden from being listed as
│ │ │  part of the available API.</p><p>An Erlang <a href="modules.html">module</a> consists of public and private functions and type
│ │ │  attributes. By default, all exported functions, exported types and callbacks are
│ │ │  considered visible and part of the module's public API. In addition, any
│ │ │  non-exported type that is referred to by any other visible type attribute is
│ │ │ -also visible, but not considered to be part of the public API. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4656859063-1">(</span><span class="p" data-group-id="4656859063-2">[</span><span class="ss">example</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4656859063-2">]</span><span class="p" data-group-id="4656859063-1">)</span><span class="p">.</span><span class="w">
│ │ │ +also visible, but not considered to be part of the public API. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1672897478-1">(</span><span class="p" data-group-id="1672897478-2">[</span><span class="ss">example</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1672897478-2">]</span><span class="p" data-group-id="1672897478-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="4656859063-3">(</span><span class="p" data-group-id="4656859063-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">example</span><span class="p" data-group-id="4656859063-4">(</span><span class="p" data-group-id="4656859063-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="4656859063-5">(</span><span class="p" data-group-id="4656859063-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">example</span><span class="p" data-group-id="4656859063-6">(</span><span class="p" data-group-id="4656859063-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span></code></pre><p>In the code above, the function <code class="inline">example/0</code> is exported and references the
│ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="1672897478-3">(</span><span class="p" data-group-id="1672897478-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">example</span><span class="p" data-group-id="1672897478-4">(</span><span class="p" data-group-id="1672897478-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="1672897478-5">(</span><span class="p" data-group-id="1672897478-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">example</span><span class="p" data-group-id="1672897478-6">(</span><span class="p" data-group-id="1672897478-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span></code></pre><p>In the code above, the function <code class="inline">example/0</code> is exported and references the
│ │ │  unexported type <code class="inline">private/0</code>. Therefore both <code class="inline">example/0</code> and <code class="inline">private/0</code> will be
│ │ │  marked as visible. The <code class="inline">private/0</code> type will have the metadata field <code class="inline">exported</code>
│ │ │  set to <code class="inline">false</code> to show that it is not part of the public API.</p><p>If you want to make a visible entity hidden, you need to set the <code class="inline">-doc</code> attribute
│ │ │ -to <code class="inline">false</code>. Let us revisit our previous example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9652920999-1">(</span><span class="p" data-group-id="9652920999-2">[</span><span class="ss">example</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9652920999-2">]</span><span class="p" data-group-id="9652920999-1">)</span><span class="p">.</span><span class="w">
│ │ │ +to <code class="inline">false</code>. Let us revisit our previous example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2698721929-1">(</span><span class="p" data-group-id="2698721929-2">[</span><span class="ss">example</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2698721929-2">]</span><span class="p" data-group-id="2698721929-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="9652920999-3">(</span><span class="p" data-group-id="9652920999-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">example</span><span class="p" data-group-id="9652920999-4">(</span><span class="p" data-group-id="9652920999-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="9652920999-5">(</span><span class="p" data-group-id="9652920999-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="2698721929-3">(</span><span class="p" data-group-id="2698721929-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">example</span><span class="p" data-group-id="2698721929-4">(</span><span class="p" data-group-id="2698721929-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="2698721929-5">(</span><span class="p" data-group-id="2698721929-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="ss">false</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">example</span><span class="p" data-group-id="9652920999-6">(</span><span class="p" data-group-id="9652920999-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span></code></pre><p>The function <code class="inline">example/0</code> is exported but explicitly marked as hidden; therefore
│ │ │ +</span><span class="nf">example</span><span class="p" data-group-id="2698721929-6">(</span><span class="p" data-group-id="2698721929-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span></code></pre><p>The function <code class="inline">example/0</code> is exported but explicitly marked as hidden; therefore
│ │ │  both <code class="inline">example/0</code> and <code class="inline">private/0</code> will be hidden.</p><p>Any documentation added to an automatically hidden entity (non-exported function
│ │ │  or type) is ignored and will generate a warning. Such functions can be
│ │ │  documented using comments.</p><h2 id="compiling-and-getting-documentation" class="section-heading">
│ │ │    <a href="#compiling-and-getting-documentation" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Compiling and getting documentation</span>
│ │ │ @@ -377,21 +377,21 @@
│ │ │    <span class="text">Using ExDoc to generate HTML/ePub documentation</span>
│ │ │  </h2>
│ │ │  <p><a href="https://hexdocs.pm/ex_doc/">ExDoc</a> has built-in support to generate
│ │ │  documentation from Markdown. The simplest way is by using the
│ │ │  <a href="https://hexdocs.pm/rebar3_ex_doc">rebar3_ex_doc</a> plugin. To set up a
│ │ │  rebar3 project to use <a href="https://hexdocs.pm/ex_doc/">ExDoc</a> to generate
│ │ │  documentation, add the following to your <code class="inline">rebar3.config</code>.</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% Enable the plugin</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4461522832-1">{</span><span class="ss">plugins</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4461522832-2">[</span><span class="ss">rebar3_ex_doc</span><span class="p" data-group-id="4461522832-2">]</span><span class="p" data-group-id="4461522832-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4288278245-1">{</span><span class="ss">plugins</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4288278245-2">[</span><span class="ss">rebar3_ex_doc</span><span class="p" data-group-id="4288278245-2">]</span><span class="p" data-group-id="4288278245-1">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="p" data-group-id="4461522832-3">{</span><span class="ss">ex_doc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4461522832-4">[</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="4461522832-5">{</span><span class="ss">extras</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4461522832-6">[</span><span class="s">&quot;README.md&quot;</span><span class="p" data-group-id="4461522832-6">]</span><span class="p" data-group-id="4461522832-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="4461522832-7">{</span><span class="ss">main</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;README.md&quot;</span><span class="p" data-group-id="4461522832-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="4461522832-8">{</span><span class="ss">source_url</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;https://github.com/namespace/your_app&quot;</span><span class="p" data-group-id="4461522832-8">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4461522832-4">]</span><span class="p" data-group-id="4461522832-3">}</span><span class="p">.</span></code></pre><p>When configured, you can run <code class="inline">rebar3 ex_doc</code> to generate the
│ │ │ +</span><span class="p" data-group-id="4288278245-3">{</span><span class="ss">ex_doc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4288278245-4">[</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4288278245-5">{</span><span class="ss">extras</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4288278245-6">[</span><span class="s">&quot;README.md&quot;</span><span class="p" data-group-id="4288278245-6">]</span><span class="p" data-group-id="4288278245-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4288278245-7">{</span><span class="ss">main</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;README.md&quot;</span><span class="p" data-group-id="4288278245-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4288278245-8">{</span><span class="ss">source_url</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;https://github.com/namespace/your_app&quot;</span><span class="p" data-group-id="4288278245-8">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4288278245-4">]</span><span class="p" data-group-id="4288278245-3">}</span><span class="p">.</span></code></pre><p>When configured, you can run <code class="inline">rebar3 ex_doc</code> to generate the
│ │ │  documentation to <code class="inline">doc/index.html</code>. For more details and options, see
│ │ │  the <a href="https://hexdocs.pm/rebar3_ex_doc">rebar3_ex_doc</a> documentation.</p><p>You can also download the
│ │ │  <a href="https://github.com/elixir/ex_doc/releases/latest">release escript bundle</a> from
│ │ │  GitHub and run it from the command line. The documentation for using the escript
│ │ │  is found by running <code class="inline">ex_doc --help</code>.</p><p>If you are writing documentation that will be using
│ │ │  <a href="https://hexdocs.pm/ex_doc/">ExDoc</a> to generate HTML/ePub, it is highly
│ │ │  recommended to read its documentation.</p>
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/drivers.html
│ │ │ @@ -122,23 +122,23 @@
│ │ │    <span class="text">Drivers and Concurrency</span>
│ │ │  </h2>
│ │ │  <p>The runtime system always takes a lock before running any code in a driver.</p><p>By default, that lock is at the driver level, that is, if several ports have
│ │ │  been opened to the same driver, only code for one port can be running
│ │ │  at the same time.</p><p>A driver can be configured to have one lock for each port instead.</p><p>If a driver is used in a functional way (that is, holds no state, but only does
│ │ │  some heavy calculation and returns a result), several ports with registered
│ │ │  names can be opened beforehand, and the port to be used can be chosen based on
│ │ │ -the scheduler ID as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3986919325-1">(</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="3986919325-2">(</span><span class="p" data-group-id="3986919325-2">)</span><span class="p">,</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="3986919325-3">{</span><span class="ss">some_driver_01</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_02</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_03</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_04</span><span class="p">,</span><span class="w">
│ │ │ +the scheduler ID as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4357536325-1">(</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="4357536325-2">(</span><span class="p" data-group-id="4357536325-2">)</span><span class="p">,</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="4357536325-3">{</span><span class="ss">some_driver_01</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_02</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_03</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_04</span><span class="p">,</span><span class="w">
│ │ │  	 </span><span class="ss">some_driver_05</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_06</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_07</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_08</span><span class="p">,</span><span class="w">
│ │ │  	 </span><span class="ss">some_driver_09</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_10</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_11</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_12</span><span class="p">,</span><span class="w">
│ │ │ -	 </span><span class="ss">some_driver_13</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_14</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_15</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_16</span><span class="p" data-group-id="3986919325-3">}</span><span class="p" data-group-id="3986919325-1">)</span><span class="p">.</span><span class="w">
│ │ │ +	 </span><span class="ss">some_driver_13</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_14</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_15</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_16</span><span class="p" data-group-id="4357536325-3">}</span><span class="p" data-group-id="4357536325-1">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">client_port</span><span class="p" data-group-id="3986919325-4">(</span><span class="p" data-group-id="3986919325-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">element</span><span class="p" data-group-id="3986919325-5">(</span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="3986919325-6">(</span><span class="ss">scheduler_id</span><span class="p" data-group-id="3986919325-6">)</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="nf">tuple_size</span><span class="p" data-group-id="3986919325-7">(</span><span class="o">?</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="3986919325-8">(</span><span class="p" data-group-id="3986919325-8">)</span><span class="p" data-group-id="3986919325-7">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w">
│ │ │ -	    </span><span class="o">?</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="3986919325-9">(</span><span class="p" data-group-id="3986919325-9">)</span><span class="p" data-group-id="3986919325-5">)</span><span class="p">.</span></code></pre><p>As long as there are no more than 16 schedulers, there will never be any lock
│ │ │ +</span><span class="nf">client_port</span><span class="p" data-group-id="4357536325-4">(</span><span class="p" data-group-id="4357536325-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">element</span><span class="p" data-group-id="4357536325-5">(</span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="4357536325-6">(</span><span class="ss">scheduler_id</span><span class="p" data-group-id="4357536325-6">)</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="nf">tuple_size</span><span class="p" data-group-id="4357536325-7">(</span><span class="o">?</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="4357536325-8">(</span><span class="p" data-group-id="4357536325-8">)</span><span class="p" data-group-id="4357536325-7">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w">
│ │ │ +	    </span><span class="o">?</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="4357536325-9">(</span><span class="p" data-group-id="4357536325-9">)</span><span class="p" data-group-id="4357536325-5">)</span><span class="p">.</span></code></pre><p>As long as there are no more than 16 schedulers, there will never be any lock
│ │ │  contention on the port lock for the driver.</p><h2 id="avoiding-copying-binaries-when-calling-a-driver" class="section-heading">
│ │ │    <a href="#avoiding-copying-binaries-when-calling-a-driver" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Avoiding Copying Binaries When Calling a Driver</span>
│ │ │  </h2>
│ │ │  <p>There are basically two ways to avoid copying a binary that is sent to a driver:</p><ul><li><p>If the <code class="inline">Data</code> argument for <a href="../../erts-17.0/doc/html/erlang.html#port_control/3"><code class="inline">port_control/3</code></a> is a
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/eff_guide_functions.html
│ │ │ @@ -122,67 +122,67 @@
│ │ │    <span class="text">Pattern Matching</span>
│ │ │  </h2>
│ │ │  <p>Pattern matching in function head as well as in <code class="inline">case</code> and <code class="inline">receive</code> clauses is
│ │ │  optimized by the compiler. With a few exceptions, there is nothing to gain by
│ │ │  rearranging clauses.</p><p>One exception is pattern matching of binaries. The compiler does not rearrange
│ │ │  clauses that match binaries. Placing the clause that matches against the empty
│ │ │  binary <em>last</em> is usually slightly faster than placing it <em>first</em>.</p><p>The following is a rather unnatural example to show another exception where
│ │ │ -rearranging clauses is beneficial:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map1</span><span class="p" data-group-id="9921072168-1">(</span><span class="ss">one</span><span class="p" data-group-id="9921072168-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9921072168-2">(</span><span class="ss">two</span><span class="p" data-group-id="9921072168-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9921072168-3">(</span><span class="ss">three</span><span class="p" data-group-id="9921072168-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9921072168-4">(</span><span class="n">Int</span><span class="p" data-group-id="9921072168-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="9921072168-5">(</span><span class="n">Int</span><span class="p" data-group-id="9921072168-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9921072168-6">(</span><span class="ss">four</span><span class="p" data-group-id="9921072168-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9921072168-7">(</span><span class="ss">five</span><span class="p" data-group-id="9921072168-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9921072168-8">(</span><span class="ss">six</span><span class="p" data-group-id="9921072168-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span></code></pre><p>The problem is the clause with the variable <code class="inline">Int</code>. As a variable can match
│ │ │ +rearranging clauses is beneficial:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map1</span><span class="p" data-group-id="0391483526-1">(</span><span class="ss">one</span><span class="p" data-group-id="0391483526-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="0391483526-2">(</span><span class="ss">two</span><span class="p" data-group-id="0391483526-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="0391483526-3">(</span><span class="ss">three</span><span class="p" data-group-id="0391483526-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="0391483526-4">(</span><span class="n">Int</span><span class="p" data-group-id="0391483526-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="0391483526-5">(</span><span class="n">Int</span><span class="p" data-group-id="0391483526-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="0391483526-6">(</span><span class="ss">four</span><span class="p" data-group-id="0391483526-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="0391483526-7">(</span><span class="ss">five</span><span class="p" data-group-id="0391483526-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="0391483526-8">(</span><span class="ss">six</span><span class="p" data-group-id="0391483526-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span></code></pre><p>The problem is the clause with the variable <code class="inline">Int</code>. As a variable can match
│ │ │  anything, including the atoms <code class="inline">four</code>, <code class="inline">five</code>, and <code class="inline">six</code>, which the following
│ │ │  clauses also match, the compiler must generate suboptimal code that executes as
│ │ │  follows:</p><ul><li>First, the input value is compared to <code class="inline">one</code>, <code class="inline">two</code>, and <code class="inline">three</code> (using a
│ │ │  single instruction that does a binary search; thus, quite efficient even if
│ │ │  there are many values) to select which one of the first three clauses to
│ │ │  execute (if any).</li><li>If none of the first three clauses match, the fourth clause matches as a
│ │ │  variable always matches.</li><li>If the guard test <a href="../../erts-17.0/doc/html/erlang.html#is_integer/1"><code class="inline">is_integer(Int)</code></a> succeeds, the fourth
│ │ │  clause is executed.</li><li>If the guard test fails, the input value is compared to <code class="inline">four</code>, <code class="inline">five</code>, and
│ │ │  <code class="inline">six</code>, and the appropriate clause is selected. (There is a <code class="inline">function_clause</code>
│ │ │ -exception if none of the values matched.)</li></ul><p>Rewriting to either:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map2</span><span class="p" data-group-id="9488107863-1">(</span><span class="ss">one</span><span class="p" data-group-id="9488107863-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="9488107863-2">(</span><span class="ss">two</span><span class="p" data-group-id="9488107863-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="9488107863-3">(</span><span class="ss">three</span><span class="p" data-group-id="9488107863-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="9488107863-4">(</span><span class="ss">four</span><span class="p" data-group-id="9488107863-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="9488107863-5">(</span><span class="ss">five</span><span class="p" data-group-id="9488107863-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="9488107863-6">(</span><span class="ss">six</span><span class="p" data-group-id="9488107863-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="9488107863-7">(</span><span class="n">Int</span><span class="p" data-group-id="9488107863-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="9488107863-8">(</span><span class="n">Int</span><span class="p" data-group-id="9488107863-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>or:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map3</span><span class="p" data-group-id="5057338060-1">(</span><span class="n">Int</span><span class="p" data-group-id="5057338060-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="5057338060-2">(</span><span class="n">Int</span><span class="p" data-group-id="5057338060-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="5057338060-3">(</span><span class="ss">one</span><span class="p" data-group-id="5057338060-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="5057338060-4">(</span><span class="ss">two</span><span class="p" data-group-id="5057338060-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="5057338060-5">(</span><span class="ss">three</span><span class="p" data-group-id="5057338060-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="5057338060-6">(</span><span class="ss">four</span><span class="p" data-group-id="5057338060-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="5057338060-7">(</span><span class="ss">five</span><span class="p" data-group-id="5057338060-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="5057338060-8">(</span><span class="ss">six</span><span class="p" data-group-id="5057338060-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span></code></pre><p>gives slightly more efficient matching code.</p><p>Another example:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">map_pairs1</span><span class="p" data-group-id="9288516148-1">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9288516148-2">[</span><span class="p" data-group-id="9288516148-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="9288516148-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +exception if none of the values matched.)</li></ul><p>Rewriting to either:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map2</span><span class="p" data-group-id="9803863680-1">(</span><span class="ss">one</span><span class="p" data-group-id="9803863680-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="9803863680-2">(</span><span class="ss">two</span><span class="p" data-group-id="9803863680-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="9803863680-3">(</span><span class="ss">three</span><span class="p" data-group-id="9803863680-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="9803863680-4">(</span><span class="ss">four</span><span class="p" data-group-id="9803863680-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="9803863680-5">(</span><span class="ss">five</span><span class="p" data-group-id="9803863680-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="9803863680-6">(</span><span class="ss">six</span><span class="p" data-group-id="9803863680-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="9803863680-7">(</span><span class="n">Int</span><span class="p" data-group-id="9803863680-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="9803863680-8">(</span><span class="n">Int</span><span class="p" data-group-id="9803863680-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>or:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map3</span><span class="p" data-group-id="0609928955-1">(</span><span class="n">Int</span><span class="p" data-group-id="0609928955-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="0609928955-2">(</span><span class="n">Int</span><span class="p" data-group-id="0609928955-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="0609928955-3">(</span><span class="ss">one</span><span class="p" data-group-id="0609928955-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="0609928955-4">(</span><span class="ss">two</span><span class="p" data-group-id="0609928955-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="0609928955-5">(</span><span class="ss">three</span><span class="p" data-group-id="0609928955-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="0609928955-6">(</span><span class="ss">four</span><span class="p" data-group-id="0609928955-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="0609928955-7">(</span><span class="ss">five</span><span class="p" data-group-id="0609928955-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="0609928955-8">(</span><span class="ss">six</span><span class="p" data-group-id="0609928955-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span></code></pre><p>gives slightly more efficient matching code.</p><p>Another example:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">map_pairs1</span><span class="p" data-group-id="5940152235-1">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5940152235-2">[</span><span class="p" data-group-id="5940152235-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="5940152235-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Ys</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">map_pairs1</span><span class="p" data-group-id="9288516148-3">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9288516148-4">[</span><span class="p" data-group-id="9288516148-4">]</span><span class="p" data-group-id="9288516148-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">map_pairs1</span><span class="p" data-group-id="5940152235-3">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5940152235-4">[</span><span class="p" data-group-id="5940152235-4">]</span><span class="p" data-group-id="5940152235-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Xs</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">map_pairs1</span><span class="p" data-group-id="9288516148-5">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9288516148-6">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="9288516148-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9288516148-7">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="9288516148-7">]</span><span class="p" data-group-id="9288516148-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9288516148-8">[</span><span class="n">Map</span><span class="p" data-group-id="9288516148-9">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9288516148-9">)</span><span class="p">|</span><span class="nf">map_pairs1</span><span class="p" data-group-id="9288516148-10">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="9288516148-10">)</span><span class="p" data-group-id="9288516148-8">]</span><span class="p">.</span></code></pre><p>The first argument is <em>not</em> a problem. It is variable, but it is a variable in
│ │ │ +</span><span class="nf">map_pairs1</span><span class="p" data-group-id="5940152235-5">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5940152235-6">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="5940152235-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5940152235-7">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="5940152235-7">]</span><span class="p" data-group-id="5940152235-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5940152235-8">[</span><span class="n">Map</span><span class="p" data-group-id="5940152235-9">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5940152235-9">)</span><span class="p">|</span><span class="nf">map_pairs1</span><span class="p" data-group-id="5940152235-10">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="5940152235-10">)</span><span class="p" data-group-id="5940152235-8">]</span><span class="p">.</span></code></pre><p>The first argument is <em>not</em> a problem. It is variable, but it is a variable in
│ │ │  all clauses. The problem is the variable in the second argument, <code class="inline">Xs</code>, in the
│ │ │  middle clause. Because the variable can match anything, the compiler is not
│ │ │  allowed to rearrange the clauses, but must generate code that matches them in
│ │ │  the order written.</p><p>If the function is rewritten as follows, the compiler is free to rearrange the
│ │ │ -clauses:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">map_pairs2</span><span class="p" data-group-id="7368997273-1">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7368997273-2">[</span><span class="p" data-group-id="7368997273-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="7368997273-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +clauses:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">map_pairs2</span><span class="p" data-group-id="8010933013-1">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8010933013-2">[</span><span class="p" data-group-id="8010933013-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="8010933013-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Ys</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">map_pairs2</span><span class="p" data-group-id="7368997273-3">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7368997273-4">[</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="7368997273-4">]</span><span class="o">=</span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7368997273-5">[</span><span class="p" data-group-id="7368997273-5">]</span><span class="w"> </span><span class="p" data-group-id="7368997273-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">map_pairs2</span><span class="p" data-group-id="8010933013-3">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8010933013-4">[</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="8010933013-4">]</span><span class="o">=</span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8010933013-5">[</span><span class="p" data-group-id="8010933013-5">]</span><span class="w"> </span><span class="p" data-group-id="8010933013-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Xs</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">map_pairs2</span><span class="p" data-group-id="7368997273-6">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7368997273-7">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="7368997273-7">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7368997273-8">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="7368997273-8">]</span><span class="p" data-group-id="7368997273-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7368997273-9">[</span><span class="n">Map</span><span class="p" data-group-id="7368997273-10">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7368997273-10">)</span><span class="p">|</span><span class="nf">map_pairs2</span><span class="p" data-group-id="7368997273-11">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="7368997273-11">)</span><span class="p" data-group-id="7368997273-9">]</span><span class="p">.</span></code></pre><p>The compiler will generate code similar to this:</p><p><strong>DO NOT (already done by the compiler)</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">explicit_map_pairs</span><span class="p" data-group-id="0408340292-1">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs0</span><span class="p">,</span><span class="w"> </span><span class="n">Ys0</span><span class="p" data-group-id="0408340292-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">map_pairs2</span><span class="p" data-group-id="8010933013-6">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8010933013-7">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="8010933013-7">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8010933013-8">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="8010933013-8">]</span><span class="p" data-group-id="8010933013-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8010933013-9">[</span><span class="n">Map</span><span class="p" data-group-id="8010933013-10">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8010933013-10">)</span><span class="p">|</span><span class="nf">map_pairs2</span><span class="p" data-group-id="8010933013-11">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="8010933013-11">)</span><span class="p" data-group-id="8010933013-9">]</span><span class="p">.</span></code></pre><p>The compiler will generate code similar to this:</p><p><strong>DO NOT (already done by the compiler)</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">explicit_map_pairs</span><span class="p" data-group-id="4352871685-1">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs0</span><span class="p">,</span><span class="w"> </span><span class="n">Ys0</span><span class="p" data-group-id="4352871685-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Xs0</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="0408340292-2">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="0408340292-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="4352871685-2">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="4352871685-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  	    </span><span class="k">case</span><span class="w"> </span><span class="n">Ys0</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="0408340292-3">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="0408340292-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="p" data-group-id="0408340292-4">[</span><span class="n">Map</span><span class="p" data-group-id="0408340292-5">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0408340292-5">)</span><span class="p">|</span><span class="nf">explicit_map_pairs</span><span class="p" data-group-id="0408340292-6">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="0408340292-6">)</span><span class="p" data-group-id="0408340292-4">]</span><span class="p">;</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="0408340292-7">[</span><span class="p" data-group-id="0408340292-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="4352871685-3">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="4352871685-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="p" data-group-id="4352871685-4">[</span><span class="n">Map</span><span class="p" data-group-id="4352871685-5">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4352871685-5">)</span><span class="p">|</span><span class="nf">explicit_map_pairs</span><span class="p" data-group-id="4352871685-6">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="4352871685-6">)</span><span class="p" data-group-id="4352871685-4">]</span><span class="p">;</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="4352871685-7">[</span><span class="p" data-group-id="4352871685-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  		    </span><span class="n">Xs0</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="0408340292-8">[</span><span class="p" data-group-id="0408340292-8">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="4352871685-8">[</span><span class="p" data-group-id="4352871685-8">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  	    </span><span class="n">Ys0</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>This is slightly faster for probably the most common case that the input lists
│ │ │  are not empty or very short. (Another advantage is that Dialyzer can deduce a
│ │ │  better type for the <code class="inline">Xs</code> variable.)</p><h2 id="function-calls" class="section-heading">
│ │ │    <a href="#function-calls" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/eff_guide_processes.html
│ │ │ @@ -119,45 +119,45 @@
│ │ │    <a href="#creating-an-erlang-process" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Creating an Erlang Process</span>
│ │ │  </h2>
│ │ │  <p>An Erlang process is lightweight compared to threads and processes in operating
│ │ │  systems.</p><p>A newly spawned Erlang process uses 327 words of memory. The size can be found
│ │ │ -as follows:</p><pre><code class="makeup erlang" translate="no"><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="0202101597-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p">.</span><span class="mi">3</span><span class="p" data-group-id="0202101597-1">]</span><span class="w"> </span><span class="p" data-group-id="0202101597-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="0202101597-2">]</span><span class="w"> </span><span class="p" data-group-id="0202101597-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="0202101597-3">]</span><span class="w"> </span><span class="p" data-group-id="0202101597-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="0202101597-4">]</span><span class="w"> </span><span class="p" data-group-id="0202101597-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="0202101597-5">]</span><span class="w"> </span><span class="p" data-group-id="0202101597-6">[</span><span class="ss">jit</span><span class="p" data-group-id="0202101597-6">]</span><span class="w">
│ │ │ +as follows:</p><pre><code class="makeup erlang" translate="no"><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="2514664825-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p">.</span><span class="mi">3</span><span class="p" data-group-id="2514664825-1">]</span><span class="w"> </span><span class="p" data-group-id="2514664825-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="2514664825-2">]</span><span class="w"> </span><span class="p" data-group-id="2514664825-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="2514664825-3">]</span><span class="w"> </span><span class="p" data-group-id="2514664825-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="2514664825-4">]</span><span class="w"> </span><span class="p" data-group-id="2514664825-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="2514664825-5">]</span><span class="w"> </span><span class="p" data-group-id="2514664825-6">[</span><span class="ss">jit</span><span class="p" data-group-id="2514664825-6">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mf">2.3</span><span class="w"> </span><span class="p" data-group-id="0202101597-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="0202101597-8">(</span><span class="p" data-group-id="0202101597-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="0202101597-7">)</span><span class="w">
│ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0202101597-9">(</span><span class="p" data-group-id="0202101597-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="k">after</span><span class="w"> </span><span class="ss">infinity</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mf">2.3</span><span class="w"> </span><span class="p" data-group-id="2514664825-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="2514664825-8">(</span><span class="p" data-group-id="2514664825-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="2514664825-7">)</span><span class="w">
│ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="2514664825-9">(</span><span class="p" data-group-id="2514664825-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="k">after</span><span class="w"> </span><span class="ss">infinity</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">43.39164016</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="0202101597-10">{</span><span class="p">_</span><span class="p">,</span><span class="n">Bytes</span><span class="p" data-group-id="0202101597-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">process_info</span><span class="p" data-group-id="0202101597-11">(</span><span class="nf">spawn</span><span class="p" data-group-id="0202101597-12">(</span><span class="n">Fun</span><span class="p" data-group-id="0202101597-12">)</span><span class="p">,</span><span class="w"> </span><span class="nb">memory</span><span class="p" data-group-id="0202101597-11">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0202101597-13">{</span><span class="nb">memory</span><span class="p">,</span><span class="mi">2616</span><span class="p" data-group-id="0202101597-13">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="n">Bytes</span><span class="w"> </span><span class="ow">div</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="0202101597-14">(</span><span class="ss">wordsize</span><span class="p" data-group-id="0202101597-14">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="2514664825-10">{</span><span class="p">_</span><span class="p">,</span><span class="n">Bytes</span><span class="p" data-group-id="2514664825-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">process_info</span><span class="p" data-group-id="2514664825-11">(</span><span class="nf">spawn</span><span class="p" data-group-id="2514664825-12">(</span><span class="n">Fun</span><span class="p" data-group-id="2514664825-12">)</span><span class="p">,</span><span class="w"> </span><span class="nb">memory</span><span class="p" data-group-id="2514664825-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2514664825-13">{</span><span class="nb">memory</span><span class="p">,</span><span class="mi">2616</span><span class="p" data-group-id="2514664825-13">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="n">Bytes</span><span class="w"> </span><span class="ow">div</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="2514664825-14">(</span><span class="ss">wordsize</span><span class="p" data-group-id="2514664825-14">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">327</span></code></pre><p>The size includes 233 words for the heap area (which includes the stack). The
│ │ │  garbage collector increases the heap as needed.</p><p>The main (outer) loop for a process <em>must</em> be tail-recursive. Otherwise, the
│ │ │ -stack grows until the process terminates.</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="3155060311-1">(</span><span class="p" data-group-id="3155060311-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +stack grows until the process terminates.</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="7835560235-1">(</span><span class="p" data-group-id="7835560235-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │    </span><span class="k">receive</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="3155060311-2">{</span><span class="ss">sys</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="3155060311-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -         </span><span class="nf">handle_sys_msg</span><span class="p" data-group-id="3155060311-3">(</span><span class="n">Msg</span><span class="p" data-group-id="3155060311-3">)</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="nf">loop</span><span class="p" data-group-id="3155060311-4">(</span><span class="p" data-group-id="3155060311-4">)</span><span class="p">;</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="3155060311-5">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="3155060311-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -          </span><span class="n">Reply</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="3155060311-6">(</span><span class="n">Msg</span><span class="p" data-group-id="3155060311-6">)</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="7835560235-2">{</span><span class="ss">sys</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="7835560235-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +         </span><span class="nf">handle_sys_msg</span><span class="p" data-group-id="7835560235-3">(</span><span class="n">Msg</span><span class="p" data-group-id="7835560235-3">)</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="nf">loop</span><span class="p" data-group-id="7835560235-4">(</span><span class="p" data-group-id="7835560235-4">)</span><span class="p">;</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="7835560235-5">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="7835560235-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +          </span><span class="n">Reply</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="7835560235-6">(</span><span class="n">Msg</span><span class="p" data-group-id="7835560235-6">)</span><span class="p">,</span><span class="w">
│ │ │            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Reply</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="nf">loop</span><span class="p" data-group-id="3155060311-7">(</span><span class="p" data-group-id="3155060311-7">)</span><span class="w">
│ │ │ +          </span><span class="nf">loop</span><span class="p" data-group-id="7835560235-7">(</span><span class="p" data-group-id="7835560235-7">)</span><span class="w">
│ │ │    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3155060311-8">(</span><span class="s">&quot;Message is processed</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3155060311-9">[</span><span class="p" data-group-id="3155060311-9">]</span><span class="p" data-group-id="3155060311-8">)</span><span class="p">.</span></code></pre><p>The call to <a href="../../lib/stdlib-8.0/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> will never be executed, but a return address will
│ │ │ +  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7835560235-8">(</span><span class="s">&quot;Message is processed</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7835560235-9">[</span><span class="p" data-group-id="7835560235-9">]</span><span class="p" data-group-id="7835560235-8">)</span><span class="p">.</span></code></pre><p>The call to <a href="../../lib/stdlib-8.0/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> will never be executed, but a return address will
│ │ │  still be pushed to the stack each time <code class="inline">loop/0</code> is called recursively. The
│ │ │ -correct tail-recursive version of the function looks as follows:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="7373439322-1">(</span><span class="p" data-group-id="7373439322-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +correct tail-recursive version of the function looks as follows:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="7628614138-1">(</span><span class="p" data-group-id="7628614138-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │     </span><span class="k">receive</span><span class="w">
│ │ │ -      </span><span class="p" data-group-id="7373439322-2">{</span><span class="ss">sys</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="7373439322-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -         </span><span class="nf">handle_sys_msg</span><span class="p" data-group-id="7373439322-3">(</span><span class="n">Msg</span><span class="p" data-group-id="7373439322-3">)</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="nf">loop</span><span class="p" data-group-id="7373439322-4">(</span><span class="p" data-group-id="7373439322-4">)</span><span class="p">;</span><span class="w">
│ │ │ -      </span><span class="p" data-group-id="7373439322-5">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="7373439322-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -         </span><span class="n">Reply</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="7373439322-6">(</span><span class="n">Msg</span><span class="p" data-group-id="7373439322-6">)</span><span class="p">,</span><span class="w">
│ │ │ +      </span><span class="p" data-group-id="7628614138-2">{</span><span class="ss">sys</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="7628614138-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +         </span><span class="nf">handle_sys_msg</span><span class="p" data-group-id="7628614138-3">(</span><span class="n">Msg</span><span class="p" data-group-id="7628614138-3">)</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="nf">loop</span><span class="p" data-group-id="7628614138-4">(</span><span class="p" data-group-id="7628614138-4">)</span><span class="p">;</span><span class="w">
│ │ │ +      </span><span class="p" data-group-id="7628614138-5">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="7628614138-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +         </span><span class="n">Reply</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="7628614138-6">(</span><span class="n">Msg</span><span class="p" data-group-id="7628614138-6">)</span><span class="p">,</span><span class="w">
│ │ │           </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Reply</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="nf">loop</span><span class="p" data-group-id="7373439322-7">(</span><span class="p" data-group-id="7373439322-7">)</span><span class="w">
│ │ │ +         </span><span class="nf">loop</span><span class="p" data-group-id="7628614138-7">(</span><span class="p" data-group-id="7628614138-7">)</span><span class="w">
│ │ │   </span><span class="k">end</span><span class="p">.</span></code></pre><h3 id="initial-heap-size" class="section-heading">
│ │ │    <a href="#initial-heap-size" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Initial Heap Size</span>
│ │ │  </h3>
│ │ │  <p>The default initial heap size of 233 words is quite conservative to support
│ │ │ @@ -190,30 +190,30 @@
│ │ │    </a>
│ │ │    <span class="text">Fetching Received Messages</span>
│ │ │  </h2>
│ │ │  <p>The cost of fetching a received message from the message queue depends on how
│ │ │  complicated the <code class="inline">receive</code> expression is. A simple expression that matches any
│ │ │  message is very cheap because it retrieves the first message in the message
│ │ │  queue:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="n">Message</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="2874110029-1">(</span><span class="n">Message</span><span class="p" data-group-id="2874110029-1">)</span><span class="w">
│ │ │ +    </span><span class="n">Message</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="3013988166-1">(</span><span class="n">Message</span><span class="p" data-group-id="3013988166-1">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>However, this is not always convenient: we can receive a message that we do not
│ │ │  know how to handle at this point, so it is common to only match the messages we
│ │ │  expect:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0116669786-1">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="0116669786-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="0116669786-2">(</span><span class="n">Message</span><span class="p" data-group-id="0116669786-2">)</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4167244964-1">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="4167244964-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="4167244964-2">(</span><span class="n">Message</span><span class="p" data-group-id="4167244964-2">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>While this is convenient it means that the entire message queue must be searched
│ │ │  until it finds a matching message. This is very expensive for processes with
│ │ │  long message queues, so there is an optimization for the common case of
│ │ │ -sending a request and waiting for a response shortly after:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">MRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="0644776038-1">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">Process</span><span class="p" data-group-id="0644776038-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0644776038-2">{</span><span class="nf">self</span><span class="p" data-group-id="0644776038-3">(</span><span class="p" data-group-id="0644776038-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="0644776038-2">}</span><span class="p">,</span><span class="w">
│ │ │ +sending a request and waiting for a response shortly after:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">MRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="0587672367-1">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">Process</span><span class="p" data-group-id="0587672367-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0587672367-2">{</span><span class="nf">self</span><span class="p" data-group-id="0587672367-3">(</span><span class="p" data-group-id="0587672367-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="0587672367-2">}</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0644776038-4">{</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="p" data-group-id="0644776038-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">demonitor</span><span class="p" data-group-id="0644776038-5">(</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0644776038-6">[</span><span class="ss">flush</span><span class="p" data-group-id="0644776038-6">]</span><span class="p" data-group-id="0644776038-5">)</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="nf">handle_reply</span><span class="p" data-group-id="0644776038-7">(</span><span class="n">Reply</span><span class="p" data-group-id="0644776038-7">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0644776038-8">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="0644776038-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nf">handle_error</span><span class="p" data-group-id="0644776038-9">(</span><span class="n">Reason</span><span class="p" data-group-id="0644776038-9">)</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0587672367-4">{</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="p" data-group-id="0587672367-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">demonitor</span><span class="p" data-group-id="0587672367-5">(</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0587672367-6">[</span><span class="ss">flush</span><span class="p" data-group-id="0587672367-6">]</span><span class="p" data-group-id="0587672367-5">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="nf">handle_reply</span><span class="p" data-group-id="0587672367-7">(</span><span class="n">Reply</span><span class="p" data-group-id="0587672367-7">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0587672367-8">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="0587672367-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nf">handle_error</span><span class="p" data-group-id="0587672367-9">(</span><span class="n">Reason</span><span class="p" data-group-id="0587672367-9">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>Since the compiler knows that the reference created by
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#monitor/2"><code class="inline">monitor/2</code></a> cannot exist before the call (since it is a globally
│ │ │  unique identifier), and that the <code class="inline">receive</code> only matches messages that contain
│ │ │  said reference, it will tell the emulator to search only the messages that
│ │ │  arrived after the call to <a href="../../erts-17.0/doc/html/erlang.html#monitor/2"><code class="inline">monitor/2</code></a>.</p><p>The above is a simple example where one is guaranteed that the optimization
│ │ │  will take, but what about more complicated code?</p><p><a href="" id="recv_opt_info"></a></p><h3 id="option-recv_opt_info" class="section-heading">
│ │ │    <a href="#option-recv_opt_info" class="hover-link">
│ │ │ @@ -229,101 +229,101 @@
│ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">200</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">NOT</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">all</span><span class="w"> </span><span class="ss">clauses</span><span class="w"> </span><span class="ss">do</span><span class="w"> </span><span class="ow">not</span><span class="w"> </span><span class="ss">match</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="ss">suitable</span><span class="w"> </span><span class="ss">reference</span><span class="w">
│ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">206</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">reference</span><span class="w"> </span><span class="ss">used</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">mark</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="ss">message</span><span class="w"> </span><span class="ss">queue</span><span class="w"> </span><span class="ss">position</span><span class="w">
│ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">208</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">all</span><span class="w"> </span><span class="ss">clauses</span><span class="w"> </span><span class="ss">match</span><span class="w"> </span><span class="ss">reference</span><span class="w"> </span><span class="ss">created</span><span class="w"> </span><span class="ss">by</span><span class="w"> </span><span class="nb">monitor</span><span class="p">/</span><span class="mi">2</span><span class="w"> </span><span class="ss">at</span><span class="w"> </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">206</span><span class="w">
│ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">219</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">INFO</span><span class="p">:</span><span class="w"> </span><span class="ss">passing</span><span class="w"> </span><span class="ss">reference</span><span class="w"> </span><span class="ss">created</span><span class="w"> </span><span class="ss">by</span><span class="w"> </span><span class="ss">make_ref</span><span class="p">/</span><span class="mi">0</span><span class="w"> </span><span class="ss">at</span><span class="w"> </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">218</span><span class="w">
│ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">222</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">all</span><span class="w"> </span><span class="ss">clauses</span><span class="w"> </span><span class="ss">match</span><span class="w"> </span><span class="ss">reference</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">function</span><span class="w"> </span><span class="ss">parameter</span><span class="w"> </span><span class="mi">1</span></code></pre><p>To make it clearer exactly what code the warnings refer to, the warnings in the
│ │ │  following examples are inserted as comments after the clause they refer to, for
│ │ │  example:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="nf">simple_receive</span><span class="p" data-group-id="7893362547-1">(</span><span class="p" data-group-id="7893362547-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">simple_receive</span><span class="p" data-group-id="3290823622-1">(</span><span class="p" data-group-id="3290823622-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="c1">%% efficiency_guide.erl:194: Warning: INFO: not a selective receive, this is always fast</span><span class="w">
│ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="n">Message</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="7893362547-2">(</span><span class="n">Message</span><span class="p" data-group-id="7893362547-2">)</span><span class="w">
│ │ │ +    </span><span class="n">Message</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="3290823622-2">(</span><span class="n">Message</span><span class="p" data-group-id="3290823622-2">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO NOT, unless Tag is known to be a suitable reference: see</span><span class="w">
│ │ │  </span><span class="c1">%% cross_function_receive/0 further down.</span><span class="w">
│ │ │ -</span><span class="nf">selective_receive</span><span class="p" data-group-id="7893362547-3">(</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="7893362547-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">selective_receive</span><span class="p" data-group-id="3290823622-3">(</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3290823622-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="c1">%% efficiency_guide.erl:200: Warning: NOT OPTIMIZED: all clauses do not match a suitable reference</span><span class="w">
│ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7893362547-4">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="7893362547-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="7893362547-5">(</span><span class="n">Message</span><span class="p" data-group-id="7893362547-5">)</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3290823622-4">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3290823622-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="3290823622-5">(</span><span class="n">Message</span><span class="p" data-group-id="3290823622-5">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="nf">optimized_receive</span><span class="p" data-group-id="7893362547-6">(</span><span class="n">Process</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="7893362547-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">optimized_receive</span><span class="p" data-group-id="3290823622-6">(</span><span class="n">Process</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="3290823622-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="c1">%% efficiency_guide.erl:206: Warning: OPTIMIZED: reference used to mark a message queue position</span><span class="w">
│ │ │ -    </span><span class="n">MRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="7893362547-7">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">Process</span><span class="p" data-group-id="7893362547-7">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7893362547-8">{</span><span class="nf">self</span><span class="p" data-group-id="7893362547-9">(</span><span class="p" data-group-id="7893362547-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="7893362547-8">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">MRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="3290823622-7">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">Process</span><span class="p" data-group-id="3290823622-7">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3290823622-8">{</span><span class="nf">self</span><span class="p" data-group-id="3290823622-9">(</span><span class="p" data-group-id="3290823622-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="3290823622-8">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="c1">%% efficiency_guide.erl:208: Warning: OPTIMIZED: matches reference created by monitor/2 at efficiency_guide.erl:206</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="7893362547-10">{</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="p" data-group-id="7893362547-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">demonitor</span><span class="p" data-group-id="7893362547-11">(</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7893362547-12">[</span><span class="ss">flush</span><span class="p" data-group-id="7893362547-12">]</span><span class="p" data-group-id="7893362547-11">)</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="nf">handle_reply</span><span class="p" data-group-id="7893362547-13">(</span><span class="n">Reply</span><span class="p" data-group-id="7893362547-13">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7893362547-14">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="7893362547-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">handle_error</span><span class="p" data-group-id="7893362547-15">(</span><span class="n">Reason</span><span class="p" data-group-id="7893362547-15">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3290823622-10">{</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="p" data-group-id="3290823622-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">demonitor</span><span class="p" data-group-id="3290823622-11">(</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3290823622-12">[</span><span class="ss">flush</span><span class="p" data-group-id="3290823622-12">]</span><span class="p" data-group-id="3290823622-11">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="nf">handle_reply</span><span class="p" data-group-id="3290823622-13">(</span><span class="n">Reply</span><span class="p" data-group-id="3290823622-13">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3290823622-14">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="3290823622-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">handle_error</span><span class="p" data-group-id="3290823622-15">(</span><span class="n">Reason</span><span class="p" data-group-id="3290823622-15">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="nf">cross_function_receive</span><span class="p" data-group-id="7893362547-16">(</span><span class="p" data-group-id="7893362547-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">cross_function_receive</span><span class="p" data-group-id="3290823622-16">(</span><span class="p" data-group-id="3290823622-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% efficiency_guide.erl:218: Warning: OPTIMIZED: reference used to mark a message queue position</span><span class="w">
│ │ │ -    </span><span class="n">Ref</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="7893362547-17">(</span><span class="p" data-group-id="7893362547-17">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Ref</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="3290823622-17">(</span><span class="p" data-group-id="3290823622-17">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="c1">%% efficiency_guide.erl:219: Warning: INFO: passing reference created by make_ref/0 at efficiency_guide.erl:218</span><span class="w">
│ │ │ -    </span><span class="nf">cross_function_receive</span><span class="p" data-group-id="7893362547-18">(</span><span class="n">Ref</span><span class="p" data-group-id="7893362547-18">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">cross_function_receive</span><span class="p" data-group-id="3290823622-18">(</span><span class="n">Ref</span><span class="p" data-group-id="3290823622-18">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">cross_function_receive</span><span class="p" data-group-id="7893362547-19">(</span><span class="n">Ref</span><span class="p" data-group-id="7893362547-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">cross_function_receive</span><span class="p" data-group-id="3290823622-19">(</span><span class="n">Ref</span><span class="p" data-group-id="3290823622-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% efficiency_guide.erl:222: Warning: OPTIMIZED: all clauses match reference in function parameter 1</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="7893362547-20">{</span><span class="n">Ref</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="7893362547-20">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="7893362547-21">(</span><span class="n">Message</span><span class="p" data-group-id="7893362547-21">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3290823622-20">{</span><span class="n">Ref</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3290823622-20">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="3290823622-21">(</span><span class="n">Message</span><span class="p" data-group-id="3290823622-21">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><h2 id="literal-pool" class="section-heading">
│ │ │    <a href="#literal-pool" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Literal Pool</span>
│ │ │  </h2>
│ │ │  <p>Constant Erlang terms (hereafter called <em>literals</em>) are kept in <em>literal pools</em>;
│ │ │  each loaded module has its own pool. The following function does not build the
│ │ │  tuple every time it is called (only to have it discarded the next time the
│ │ │  garbage collector was run), but the tuple is located in the module's literal
│ │ │ -pool:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">days_in_month</span><span class="p" data-group-id="3155622295-1">(</span><span class="n">M</span><span class="p" data-group-id="3155622295-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">element</span><span class="p" data-group-id="3155622295-2">(</span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3155622295-3">{</span><span class="mi">31</span><span class="p">,</span><span class="mi">28</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p" data-group-id="3155622295-3">}</span><span class="p" data-group-id="3155622295-2">)</span><span class="p">.</span></code></pre><p>If a literal, or a term that contains a literal, is inserted into an Ets table,
│ │ │ +pool:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">days_in_month</span><span class="p" data-group-id="8957239811-1">(</span><span class="n">M</span><span class="p" data-group-id="8957239811-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">element</span><span class="p" data-group-id="8957239811-2">(</span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8957239811-3">{</span><span class="mi">31</span><span class="p">,</span><span class="mi">28</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p" data-group-id="8957239811-3">}</span><span class="p" data-group-id="8957239811-2">)</span><span class="p">.</span></code></pre><p>If a literal, or a term that contains a literal, is inserted into an Ets table,
│ │ │  it is <em>copied</em>. The reason is that the module containing the literal can be
│ │ │  unloaded in the future.</p><p>When a literal is sent to another process, it is <em>not</em> copied. When a module
│ │ │  holding a literal is unloaded, the literal will be copied to the heap of all
│ │ │  processes that hold references to that literal.</p><p>There also exists a global literal pool that is managed by the
│ │ │  <a href="../../erts-17.0/doc/html/persistent_term.html"><code class="inline">persistent_term</code></a> module.</p><p>By default, 1 GB of virtual address space is reserved for all literal pools (in
│ │ │  BEAM code and persistent terms). The amount of virtual address space reserved
│ │ │  for literals can be changed by using the
│ │ │  <a href="../../erts-17.0/doc/html/erts_alloc.html#MIscs"><code class="inline">+MIscs option</code></a> when starting the emulator.</p><p>Here is an example of how the reserved virtual address space for literals can be
│ │ │  raised to 2 GB (2048 MB):</p><pre><code class="text">erl +MIscs 2048</code></pre><h2 id="loss-of-sharing" class="section-heading">
│ │ │    <a href="#loss-of-sharing" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Loss of Sharing</span>
│ │ │  </h2>
│ │ │ -<p>An Erlang term can have shared subterms. Here is a simple example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7866899249-1">{</span><span class="n">SubTerm</span><span class="p">,</span><span class="w"> </span><span class="n">SubTerm</span><span class="p" data-group-id="7866899249-1">}</span></code></pre><p>Shared subterms are <em>not</em> preserved in the following cases:</p><ul><li>When a term is sent to another process</li><li>When a term is passed as the initial process arguments in the <code class="inline">spawn</code> call</li><li>When a term is stored in an Ets table</li></ul><p>That is an optimization. Most applications do not send messages with shared
│ │ │ -subterms.</p><p>The following example shows how a shared subterm can be created:</p><pre><code class="makeup erlang" translate="no"><span class="nf">kilo_byte</span><span class="p" data-group-id="3869883410-1">(</span><span class="p" data-group-id="3869883410-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">kilo_byte</span><span class="p" data-group-id="3869883410-2">(</span><span class="mi">10</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3869883410-3">[</span><span class="mi">42</span><span class="p" data-group-id="3869883410-3">]</span><span class="p" data-group-id="3869883410-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>An Erlang term can have shared subterms. Here is a simple example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6686214939-1">{</span><span class="n">SubTerm</span><span class="p">,</span><span class="w"> </span><span class="n">SubTerm</span><span class="p" data-group-id="6686214939-1">}</span></code></pre><p>Shared subterms are <em>not</em> preserved in the following cases:</p><ul><li>When a term is sent to another process</li><li>When a term is passed as the initial process arguments in the <code class="inline">spawn</code> call</li><li>When a term is stored in an Ets table</li></ul><p>That is an optimization. Most applications do not send messages with shared
│ │ │ +subterms.</p><p>The following example shows how a shared subterm can be created:</p><pre><code class="makeup erlang" translate="no"><span class="nf">kilo_byte</span><span class="p" data-group-id="2772585893-1">(</span><span class="p" data-group-id="2772585893-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">kilo_byte</span><span class="p" data-group-id="2772585893-2">(</span><span class="mi">10</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2772585893-3">[</span><span class="mi">42</span><span class="p" data-group-id="2772585893-3">]</span><span class="p" data-group-id="2772585893-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">kilo_byte</span><span class="p" data-group-id="3869883410-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3869883410-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">kilo_byte</span><span class="p" data-group-id="2772585893-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2772585893-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Acc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">kilo_byte</span><span class="p" data-group-id="3869883410-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3869883410-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">kilo_byte</span><span class="p" data-group-id="3869883410-6">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3869883410-7">[</span><span class="n">Acc</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="3869883410-7">]</span><span class="p" data-group-id="3869883410-6">)</span><span class="p">.</span></code></pre><p><code class="inline">kilo_byte/1</code> creates a deep list. If <a href="../../erts-17.0/doc/html/erlang.html#list_to_binary/1"><code class="inline">list_to_binary/1</code></a>
│ │ │ +</span><span class="nf">kilo_byte</span><span class="p" data-group-id="2772585893-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2772585893-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">kilo_byte</span><span class="p" data-group-id="2772585893-6">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2772585893-7">[</span><span class="n">Acc</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="2772585893-7">]</span><span class="p" data-group-id="2772585893-6">)</span><span class="p">.</span></code></pre><p><code class="inline">kilo_byte/1</code> creates a deep list. If <a href="../../erts-17.0/doc/html/erlang.html#list_to_binary/1"><code class="inline">list_to_binary/1</code></a>
│ │ │  is called, the deep list can be converted to a binary of 1024 bytes:</p><pre><code class="text">1&gt; byte_size(list_to_binary(efficiency_guide:kilo_byte())).
│ │ │  1024</code></pre><p>Using the <code class="inline">erts_debug:size/1</code> BIF, it can be seen that the deep list only
│ │ │ -requires 22 words of heap space:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">size</span><span class="p" data-group-id="5880438576-1">(</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="5880438576-2">(</span><span class="p" data-group-id="5880438576-2">)</span><span class="p" data-group-id="5880438576-1">)</span><span class="p">.</span><span class="w">
│ │ │ +requires 22 words of heap space:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">size</span><span class="p" data-group-id="0804876492-1">(</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="0804876492-2">(</span><span class="p" data-group-id="0804876492-2">)</span><span class="p" data-group-id="0804876492-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">22</span></code></pre><p>Using the <code class="inline">erts_debug:flat_size/1</code> BIF, the size of the deep list can be
│ │ │  calculated if sharing is ignored. It becomes the size of the list when it has
│ │ │ -been sent to another process or stored in an Ets table:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">flat_size</span><span class="p" data-group-id="9648574435-1">(</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="9648574435-2">(</span><span class="p" data-group-id="9648574435-2">)</span><span class="p" data-group-id="9648574435-1">)</span><span class="p">.</span><span class="w">
│ │ │ +been sent to another process or stored in an Ets table:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">flat_size</span><span class="p" data-group-id="9121868541-1">(</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="9121868541-2">(</span><span class="p" data-group-id="9121868541-2">)</span><span class="p" data-group-id="9121868541-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4094</span></code></pre><p>It can be verified that sharing will be lost if the data is inserted into an Ets
│ │ │ -table:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="n">T</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="6078020217-1">(</span><span class="ss">tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6078020217-2">[</span><span class="p" data-group-id="6078020217-2">]</span><span class="p" data-group-id="6078020217-1">)</span><span class="p">.</span><span class="w">
│ │ │ +table:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="n">T</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="6895385181-1">(</span><span class="ss">tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6895385181-2">[</span><span class="p" data-group-id="6895385181-2">]</span><span class="p" data-group-id="6895385181-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Ref</span><span class="o">&lt;</span><span class="mf">0.1662103692</span><span class="p">.</span><span class="mf">2407923716.214181</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">ets</span><span class="p">:</span><span class="nf">insert</span><span class="p" data-group-id="6078020217-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6078020217-4">{</span><span class="ss">key</span><span class="p">,</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="6078020217-5">(</span><span class="p" data-group-id="6078020217-5">)</span><span class="p" data-group-id="6078020217-4">}</span><span class="p" data-group-id="6078020217-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">ets</span><span class="p">:</span><span class="nf">insert</span><span class="p" data-group-id="6895385181-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6895385181-4">{</span><span class="ss">key</span><span class="p">,</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="6895385181-5">(</span><span class="p" data-group-id="6895385181-5">)</span><span class="p" data-group-id="6895385181-4">}</span><span class="p" data-group-id="6895385181-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">size</span><span class="p" data-group-id="6078020217-6">(</span><span class="nf">element</span><span class="p" data-group-id="6078020217-7">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="nf">hd</span><span class="p" data-group-id="6078020217-8">(</span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="6078020217-9">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="ss">key</span><span class="p" data-group-id="6078020217-9">)</span><span class="p" data-group-id="6078020217-8">)</span><span class="p" data-group-id="6078020217-7">)</span><span class="p" data-group-id="6078020217-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">size</span><span class="p" data-group-id="6895385181-6">(</span><span class="nf">element</span><span class="p" data-group-id="6895385181-7">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="nf">hd</span><span class="p" data-group-id="6895385181-8">(</span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="6895385181-9">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="ss">key</span><span class="p" data-group-id="6895385181-9">)</span><span class="p" data-group-id="6895385181-8">)</span><span class="p" data-group-id="6895385181-7">)</span><span class="p" data-group-id="6895385181-6">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4094</span><span class="w">
│ │ │ -</span><span class="gp unselectable">7&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">flat_size</span><span class="p" data-group-id="6078020217-10">(</span><span class="nf">element</span><span class="p" data-group-id="6078020217-11">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="nf">hd</span><span class="p" data-group-id="6078020217-12">(</span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="6078020217-13">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="ss">key</span><span class="p" data-group-id="6078020217-13">)</span><span class="p" data-group-id="6078020217-12">)</span><span class="p" data-group-id="6078020217-11">)</span><span class="p" data-group-id="6078020217-10">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">7&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">flat_size</span><span class="p" data-group-id="6895385181-10">(</span><span class="nf">element</span><span class="p" data-group-id="6895385181-11">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="nf">hd</span><span class="p" data-group-id="6895385181-12">(</span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="6895385181-13">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="ss">key</span><span class="p" data-group-id="6895385181-13">)</span><span class="p" data-group-id="6895385181-12">)</span><span class="p" data-group-id="6895385181-11">)</span><span class="p" data-group-id="6895385181-10">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4094</span></code></pre><p>When the data has passed through an Ets table, <code class="inline">erts_debug:size/1</code> and
│ │ │  <code class="inline">erts_debug:flat_size/1</code> return the same value. Sharing has been lost.</p><p>It is possible to build an <em>experimental</em> variant of the runtime system that
│ │ │  will preserve sharing when copying terms by giving the
│ │ │  <code class="inline">--enable-sharing-preserving</code> option to the <code class="inline">configure</code> script.</p><h2 id="smp-run-time-system" class="section-heading">
│ │ │    <a href="#smp-run-time-system" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/erl_interface.html
│ │ │ @@ -120,119 +120,119 @@
│ │ │  to read the port example in <a href="c_port.html">Ports</a> before reading this section.</p><h2 id="erlang-program" class="section-heading">
│ │ │    <a href="#erlang-program" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Erlang Program</span>
│ │ │  </h2>
│ │ │  <p>The following example shows an Erlang program communicating with a C program
│ │ │ -over a plain port with home made encoding:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1238974757-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="1238974757-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1238974757-2">(</span><span class="p" data-group-id="1238974757-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1238974757-3">]</span><span class="p" data-group-id="1238974757-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1238974757-4">(</span><span class="p" data-group-id="1238974757-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1238974757-5">]</span><span class="p" data-group-id="1238974757-4">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="1238974757-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="1238974757-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="1238974757-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1238974757-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="1238974757-8">]</span><span class="p" data-group-id="1238974757-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="1238974757-9">(</span><span class="p" data-group-id="1238974757-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +over a plain port with home made encoding:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4452618457-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="4452618457-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4452618457-2">(</span><span class="p" data-group-id="4452618457-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4452618457-3">]</span><span class="p" data-group-id="4452618457-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4452618457-4">(</span><span class="p" data-group-id="4452618457-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4452618457-5">]</span><span class="p" data-group-id="4452618457-4">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="4452618457-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="4452618457-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="4452618457-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4452618457-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="4452618457-8">]</span><span class="p" data-group-id="4452618457-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="4452618457-9">(</span><span class="p" data-group-id="4452618457-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">stop</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="1238974757-10">(</span><span class="n">X</span><span class="p" data-group-id="1238974757-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="1238974757-11">(</span><span class="p" data-group-id="1238974757-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1238974757-12">}</span><span class="p" data-group-id="1238974757-11">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="1238974757-13">(</span><span class="n">Y</span><span class="p" data-group-id="1238974757-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="1238974757-14">(</span><span class="p" data-group-id="1238974757-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1238974757-15">}</span><span class="p" data-group-id="1238974757-14">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="4452618457-10">(</span><span class="n">X</span><span class="p" data-group-id="4452618457-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="4452618457-11">(</span><span class="p" data-group-id="4452618457-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4452618457-12">}</span><span class="p" data-group-id="4452618457-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="4452618457-13">(</span><span class="n">Y</span><span class="p" data-group-id="4452618457-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="4452618457-14">(</span><span class="p" data-group-id="4452618457-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4452618457-15">}</span><span class="p" data-group-id="4452618457-14">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="1238974757-16">(</span><span class="n">Msg</span><span class="p" data-group-id="1238974757-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1238974757-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1238974757-18">(</span><span class="p" data-group-id="1238974757-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="1238974757-17">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="4452618457-16">(</span><span class="n">Msg</span><span class="p" data-group-id="4452618457-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4452618457-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4452618457-18">(</span><span class="p" data-group-id="4452618457-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4452618457-17">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="1238974757-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1238974757-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="4452618457-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4452618457-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  	    </span><span class="n">Result</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="1238974757-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="1238974757-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="1238974757-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1238974757-22">(</span><span class="p" data-group-id="1238974757-22">)</span><span class="p" data-group-id="1238974757-21">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="1238974757-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="1238974757-23">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="1238974757-24">(</span><span class="p" data-group-id="1238974757-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="1238974757-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1238974757-26">[</span><span class="p" data-group-id="1238974757-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1238974757-27">}</span><span class="p" data-group-id="1238974757-26">]</span><span class="p" data-group-id="1238974757-24">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="1238974757-28">(</span><span class="n">Port</span><span class="p" data-group-id="1238974757-28">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="4452618457-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="4452618457-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="4452618457-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4452618457-22">(</span><span class="p" data-group-id="4452618457-22">)</span><span class="p" data-group-id="4452618457-21">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="4452618457-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4452618457-23">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="4452618457-24">(</span><span class="p" data-group-id="4452618457-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="4452618457-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4452618457-26">[</span><span class="p" data-group-id="4452618457-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="4452618457-27">}</span><span class="p" data-group-id="4452618457-26">]</span><span class="p" data-group-id="4452618457-24">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="4452618457-28">(</span><span class="n">Port</span><span class="p" data-group-id="4452618457-28">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="1238974757-29">(</span><span class="n">Port</span><span class="p" data-group-id="1238974757-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="4452618457-29">(</span><span class="n">Port</span><span class="p" data-group-id="4452618457-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="1238974757-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="1238974757-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1238974757-31">{</span><span class="nf">self</span><span class="p" data-group-id="1238974757-32">(</span><span class="p" data-group-id="1238974757-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1238974757-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="1238974757-34">(</span><span class="n">Msg</span><span class="p" data-group-id="1238974757-34">)</span><span class="p" data-group-id="1238974757-33">}</span><span class="p" data-group-id="1238974757-31">}</span><span class="p">,</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="4452618457-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4452618457-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4452618457-31">{</span><span class="nf">self</span><span class="p" data-group-id="4452618457-32">(</span><span class="p" data-group-id="4452618457-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4452618457-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="4452618457-34">(</span><span class="n">Msg</span><span class="p" data-group-id="4452618457-34">)</span><span class="p" data-group-id="4452618457-33">}</span><span class="p" data-group-id="4452618457-31">}</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="1238974757-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1238974757-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1238974757-36">}</span><span class="p" data-group-id="1238974757-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1238974757-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="1238974757-38">(</span><span class="n">Data</span><span class="p" data-group-id="1238974757-38">)</span><span class="p" data-group-id="1238974757-37">}</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="4452618457-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4452618457-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4452618457-36">}</span><span class="p" data-group-id="4452618457-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4452618457-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="4452618457-38">(</span><span class="n">Data</span><span class="p" data-group-id="4452618457-38">)</span><span class="p" data-group-id="4452618457-37">}</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -	    </span><span class="nf">loop</span><span class="p" data-group-id="1238974757-39">(</span><span class="n">Port</span><span class="p" data-group-id="1238974757-39">)</span><span class="p">;</span><span class="w">
│ │ │ +	    </span><span class="nf">loop</span><span class="p" data-group-id="4452618457-39">(</span><span class="n">Port</span><span class="p" data-group-id="4452618457-39">)</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">stop</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1238974757-40">{</span><span class="nf">self</span><span class="p" data-group-id="1238974757-41">(</span><span class="p" data-group-id="1238974757-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="1238974757-40">}</span><span class="p">,</span><span class="w">
│ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4452618457-40">{</span><span class="nf">self</span><span class="p" data-group-id="4452618457-41">(</span><span class="p" data-group-id="4452618457-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="4452618457-40">}</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="1238974757-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="1238974757-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="nf">exit</span><span class="p" data-group-id="1238974757-43">(</span><span class="ss">normal</span><span class="p" data-group-id="1238974757-43">)</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="4452618457-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="4452618457-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="nf">exit</span><span class="p" data-group-id="4452618457-43">(</span><span class="ss">normal</span><span class="p" data-group-id="4452618457-43">)</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="1238974757-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="1238974757-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="nf">exit</span><span class="p" data-group-id="1238974757-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="1238974757-45">)</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="4452618457-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="4452618457-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	    </span><span class="nf">exit</span><span class="p" data-group-id="4452618457-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="4452618457-45">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="1238974757-46">(</span><span class="p" data-group-id="1238974757-47">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1238974757-47">}</span><span class="p" data-group-id="1238974757-46">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1238974757-48">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1238974757-48">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="1238974757-49">(</span><span class="p" data-group-id="1238974757-50">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1238974757-50">}</span><span class="p" data-group-id="1238974757-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1238974757-51">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1238974757-51">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="4452618457-46">(</span><span class="p" data-group-id="4452618457-47">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4452618457-47">}</span><span class="p" data-group-id="4452618457-46">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4452618457-48">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4452618457-48">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="4452618457-49">(</span><span class="p" data-group-id="4452618457-50">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4452618457-50">}</span><span class="p" data-group-id="4452618457-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4452618457-51">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4452618457-51">]</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="1238974757-52">(</span><span class="p" data-group-id="1238974757-53">[</span><span class="n">Int</span><span class="p" data-group-id="1238974757-53">]</span><span class="p" data-group-id="1238974757-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>There are two differences when using Erl_Interface on the C side compared to the
│ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="4452618457-52">(</span><span class="p" data-group-id="4452618457-53">[</span><span class="n">Int</span><span class="p" data-group-id="4452618457-53">]</span><span class="p" data-group-id="4452618457-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>There are two differences when using Erl_Interface on the C side compared to the
│ │ │  example in <a href="c_port.html">Ports</a>, using only the plain port:</p><ul><li>As Erl_Interface operates on the Erlang external term format, the port must be
│ │ │  set to use binaries.</li><li>Instead of inventing an encoding/decoding scheme, the
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#term_to_binary/1"><code class="inline">term_to_binary/1</code></a> and
│ │ │ -<a href="../../erts-17.0/doc/html/erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a> BIFs are to be used.</li></ul><p>That is:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open_port</span><span class="p" data-group-id="8910826594-1">(</span><span class="p" data-group-id="8910826594-2">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="8910826594-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8910826594-3">[</span><span class="p" data-group-id="8910826594-4">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="8910826594-4">}</span><span class="p" data-group-id="8910826594-3">]</span><span class="p" data-group-id="8910826594-1">)</span></code></pre><p>is replaced with:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open_port</span><span class="p" data-group-id="0727256955-1">(</span><span class="p" data-group-id="0727256955-2">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="0727256955-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0727256955-3">[</span><span class="p" data-group-id="0727256955-4">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0727256955-4">}</span><span class="p">,</span><span class="w"> </span><span class="ss">binary</span><span class="p" data-group-id="0727256955-3">]</span><span class="p" data-group-id="0727256955-1">)</span></code></pre><p>And:</p><pre><code class="makeup erlang" translate="no"><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2523315636-1">{</span><span class="nf">self</span><span class="p" data-group-id="2523315636-2">(</span><span class="p" data-group-id="2523315636-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2523315636-3">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="2523315636-4">(</span><span class="n">Msg</span><span class="p" data-group-id="2523315636-4">)</span><span class="p" data-group-id="2523315636-3">}</span><span class="p" data-group-id="2523315636-1">}</span><span class="p">,</span><span class="w">
│ │ │ +<a href="../../erts-17.0/doc/html/erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a> BIFs are to be used.</li></ul><p>That is:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open_port</span><span class="p" data-group-id="1823299742-1">(</span><span class="p" data-group-id="1823299742-2">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="1823299742-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1823299742-3">[</span><span class="p" data-group-id="1823299742-4">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1823299742-4">}</span><span class="p" data-group-id="1823299742-3">]</span><span class="p" data-group-id="1823299742-1">)</span></code></pre><p>is replaced with:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open_port</span><span class="p" data-group-id="4786915684-1">(</span><span class="p" data-group-id="4786915684-2">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="4786915684-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4786915684-3">[</span><span class="p" data-group-id="4786915684-4">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="4786915684-4">}</span><span class="p">,</span><span class="w"> </span><span class="ss">binary</span><span class="p" data-group-id="4786915684-3">]</span><span class="p" data-group-id="4786915684-1">)</span></code></pre><p>And:</p><pre><code class="makeup erlang" translate="no"><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0410478123-1">{</span><span class="nf">self</span><span class="p" data-group-id="0410478123-2">(</span><span class="p" data-group-id="0410478123-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0410478123-3">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="0410478123-4">(</span><span class="n">Msg</span><span class="p" data-group-id="0410478123-4">)</span><span class="p" data-group-id="0410478123-3">}</span><span class="p" data-group-id="0410478123-1">}</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="2523315636-5">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2523315636-6">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2523315636-6">}</span><span class="p" data-group-id="2523315636-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2523315636-7">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="2523315636-8">(</span><span class="n">Data</span><span class="p" data-group-id="2523315636-8">)</span><span class="p" data-group-id="2523315636-7">}</span><span class="w">
│ │ │ -</span><span class="k">end</span></code></pre><p>is replaced with:</p><pre><code class="makeup erlang" translate="no"><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3949755044-1">{</span><span class="nf">self</span><span class="p" data-group-id="3949755044-2">(</span><span class="p" data-group-id="3949755044-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3949755044-3">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="3949755044-4">(</span><span class="n">Msg</span><span class="p" data-group-id="3949755044-4">)</span><span class="p" data-group-id="3949755044-3">}</span><span class="p" data-group-id="3949755044-1">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="0410478123-5">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0410478123-6">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0410478123-6">}</span><span class="p" data-group-id="0410478123-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0410478123-7">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="0410478123-8">(</span><span class="n">Data</span><span class="p" data-group-id="0410478123-8">)</span><span class="p" data-group-id="0410478123-7">}</span><span class="w">
│ │ │ +</span><span class="k">end</span></code></pre><p>is replaced with:</p><pre><code class="makeup erlang" translate="no"><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5251274404-1">{</span><span class="nf">self</span><span class="p" data-group-id="5251274404-2">(</span><span class="p" data-group-id="5251274404-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5251274404-3">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="5251274404-4">(</span><span class="n">Msg</span><span class="p" data-group-id="5251274404-4">)</span><span class="p" data-group-id="5251274404-3">}</span><span class="p" data-group-id="5251274404-1">}</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3949755044-5">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3949755044-6">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3949755044-6">}</span><span class="p" data-group-id="3949755044-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3949755044-7">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="3949755044-8">(</span><span class="n">Data</span><span class="p" data-group-id="3949755044-8">)</span><span class="p" data-group-id="3949755044-7">}</span><span class="w">
│ │ │ -</span><span class="k">end</span></code></pre><p>The resulting Erlang program is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2787202481-1">(</span><span class="ss">complex2</span><span class="p" data-group-id="2787202481-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2787202481-2">(</span><span class="p" data-group-id="2787202481-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2787202481-3">]</span><span class="p" data-group-id="2787202481-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2787202481-4">(</span><span class="p" data-group-id="2787202481-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2787202481-5">]</span><span class="p" data-group-id="2787202481-4">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="2787202481-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="2787202481-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="2787202481-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2787202481-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="2787202481-8">]</span><span class="p" data-group-id="2787202481-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="2787202481-9">(</span><span class="p" data-group-id="2787202481-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="5251274404-5">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5251274404-6">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5251274404-6">}</span><span class="p" data-group-id="5251274404-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5251274404-7">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="5251274404-8">(</span><span class="n">Data</span><span class="p" data-group-id="5251274404-8">)</span><span class="p" data-group-id="5251274404-7">}</span><span class="w">
│ │ │ +</span><span class="k">end</span></code></pre><p>The resulting Erlang program is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1140535098-1">(</span><span class="ss">complex2</span><span class="p" data-group-id="1140535098-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1140535098-2">(</span><span class="p" data-group-id="1140535098-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1140535098-3">]</span><span class="p" data-group-id="1140535098-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1140535098-4">(</span><span class="p" data-group-id="1140535098-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1140535098-5">]</span><span class="p" data-group-id="1140535098-4">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="1140535098-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="1140535098-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="1140535098-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1140535098-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="1140535098-8">]</span><span class="p" data-group-id="1140535098-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="1140535098-9">(</span><span class="p" data-group-id="1140535098-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">stop</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="2787202481-10">(</span><span class="n">X</span><span class="p" data-group-id="2787202481-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="2787202481-11">(</span><span class="p" data-group-id="2787202481-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="2787202481-12">}</span><span class="p" data-group-id="2787202481-11">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="2787202481-13">(</span><span class="n">Y</span><span class="p" data-group-id="2787202481-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="2787202481-14">(</span><span class="p" data-group-id="2787202481-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2787202481-15">}</span><span class="p" data-group-id="2787202481-14">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="1140535098-10">(</span><span class="n">X</span><span class="p" data-group-id="1140535098-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="1140535098-11">(</span><span class="p" data-group-id="1140535098-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1140535098-12">}</span><span class="p" data-group-id="1140535098-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="1140535098-13">(</span><span class="n">Y</span><span class="p" data-group-id="1140535098-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="1140535098-14">(</span><span class="p" data-group-id="1140535098-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1140535098-15">}</span><span class="p" data-group-id="1140535098-14">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="2787202481-16">(</span><span class="n">Msg</span><span class="p" data-group-id="2787202481-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2787202481-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2787202481-18">(</span><span class="p" data-group-id="2787202481-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="2787202481-17">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="1140535098-16">(</span><span class="n">Msg</span><span class="p" data-group-id="1140535098-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1140535098-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1140535098-18">(</span><span class="p" data-group-id="1140535098-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="1140535098-17">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="2787202481-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="2787202481-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="1140535098-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1140535098-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  	    </span><span class="n">Result</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="2787202481-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="2787202481-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="2787202481-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2787202481-22">(</span><span class="p" data-group-id="2787202481-22">)</span><span class="p" data-group-id="2787202481-21">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="2787202481-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="2787202481-23">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="2787202481-24">(</span><span class="p" data-group-id="2787202481-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="2787202481-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2787202481-26">[</span><span class="p" data-group-id="2787202481-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="2787202481-27">}</span><span class="p">,</span><span class="w"> </span><span class="ss">binary</span><span class="p" data-group-id="2787202481-26">]</span><span class="p" data-group-id="2787202481-24">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="2787202481-28">(</span><span class="n">Port</span><span class="p" data-group-id="2787202481-28">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="1140535098-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="1140535098-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="1140535098-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1140535098-22">(</span><span class="p" data-group-id="1140535098-22">)</span><span class="p" data-group-id="1140535098-21">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="1140535098-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="1140535098-23">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="1140535098-24">(</span><span class="p" data-group-id="1140535098-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="1140535098-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1140535098-26">[</span><span class="p" data-group-id="1140535098-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1140535098-27">}</span><span class="p">,</span><span class="w"> </span><span class="ss">binary</span><span class="p" data-group-id="1140535098-26">]</span><span class="p" data-group-id="1140535098-24">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="1140535098-28">(</span><span class="n">Port</span><span class="p" data-group-id="1140535098-28">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="2787202481-29">(</span><span class="n">Port</span><span class="p" data-group-id="2787202481-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="1140535098-29">(</span><span class="n">Port</span><span class="p" data-group-id="1140535098-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="2787202481-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="2787202481-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2787202481-31">{</span><span class="nf">self</span><span class="p" data-group-id="2787202481-32">(</span><span class="p" data-group-id="2787202481-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2787202481-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="2787202481-34">(</span><span class="n">Msg</span><span class="p" data-group-id="2787202481-34">)</span><span class="p" data-group-id="2787202481-33">}</span><span class="p" data-group-id="2787202481-31">}</span><span class="p">,</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="1140535098-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="1140535098-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1140535098-31">{</span><span class="nf">self</span><span class="p" data-group-id="1140535098-32">(</span><span class="p" data-group-id="1140535098-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1140535098-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="1140535098-34">(</span><span class="n">Msg</span><span class="p" data-group-id="1140535098-34">)</span><span class="p" data-group-id="1140535098-33">}</span><span class="p" data-group-id="1140535098-31">}</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="2787202481-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2787202481-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2787202481-36">}</span><span class="p" data-group-id="2787202481-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2787202481-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="2787202481-38">(</span><span class="n">Data</span><span class="p" data-group-id="2787202481-38">)</span><span class="p" data-group-id="2787202481-37">}</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="1140535098-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1140535098-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1140535098-36">}</span><span class="p" data-group-id="1140535098-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1140535098-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="1140535098-38">(</span><span class="n">Data</span><span class="p" data-group-id="1140535098-38">)</span><span class="p" data-group-id="1140535098-37">}</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -	    </span><span class="nf">loop</span><span class="p" data-group-id="2787202481-39">(</span><span class="n">Port</span><span class="p" data-group-id="2787202481-39">)</span><span class="p">;</span><span class="w">
│ │ │ +	    </span><span class="nf">loop</span><span class="p" data-group-id="1140535098-39">(</span><span class="n">Port</span><span class="p" data-group-id="1140535098-39">)</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">stop</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2787202481-40">{</span><span class="nf">self</span><span class="p" data-group-id="2787202481-41">(</span><span class="p" data-group-id="2787202481-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="2787202481-40">}</span><span class="p">,</span><span class="w">
│ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1140535098-40">{</span><span class="nf">self</span><span class="p" data-group-id="1140535098-41">(</span><span class="p" data-group-id="1140535098-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="1140535098-40">}</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="2787202481-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="2787202481-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="nf">exit</span><span class="p" data-group-id="2787202481-43">(</span><span class="ss">normal</span><span class="p" data-group-id="2787202481-43">)</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="1140535098-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="1140535098-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="nf">exit</span><span class="p" data-group-id="1140535098-43">(</span><span class="ss">normal</span><span class="p" data-group-id="1140535098-43">)</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="2787202481-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="2787202481-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="nf">exit</span><span class="p" data-group-id="2787202481-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="2787202481-45">)</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="1140535098-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="1140535098-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	    </span><span class="nf">exit</span><span class="p" data-group-id="1140535098-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="1140535098-45">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Notice that calling <code class="inline">complex2:foo/1</code> and <code class="inline">complex2:bar/1</code> results in the tuple
│ │ │  <code class="inline">{foo,X}</code> or <code class="inline">{bar,Y}</code> being sent to the <code class="inline">complex</code> process, which codes them as
│ │ │  binaries and sends them to the port. This means that the C program must be able
│ │ │  to handle these two tuples.</p><h2 id="c-program" class="section-heading">
│ │ │    <a href="#c-program" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -362,27 +362,27 @@
│ │ │      -L/usr/local/otp/lib/erl_interface-3.9.2/lib \
│ │ │      complex.c erl_comm.c ei.c -lei -lpthread</code></pre><p>In Erlang/OTP R5B and later versions of OTP, the <code class="inline">include</code> and <code class="inline">lib</code> directories
│ │ │  are situated under <code class="inline">$OTPROOT/lib/erl_interface-VSN</code>, where <code class="inline">$OTPROOT</code> is the
│ │ │  root directory of the OTP installation (<code class="inline">/usr/local/otp</code> in the recent example)
│ │ │  and <code class="inline">VSN</code> is the version of the Erl_interface application (3.2.1 in the recent
│ │ │  example).</p><p>In R4B and earlier versions of OTP, <code class="inline">include</code> and <code class="inline">lib</code> are situated under
│ │ │  <code class="inline">$OTPROOT/usr</code>.</p><p><em>Step 2.</em> Start Erlang and compile the Erlang code:</p><pre><code class="makeup erlang" translate="no"><span class="sc">$ </span><span class="ss">erl</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="4042311755-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="4042311755-1">]</span><span class="w"> </span><span class="p" data-group-id="4042311755-2">[</span><span class="ss">source</span><span class="p" data-group-id="4042311755-2">]</span><span class="w"> </span><span class="p" data-group-id="4042311755-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="4042311755-3">]</span><span class="w"> </span><span class="p" data-group-id="4042311755-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="4042311755-4">]</span><span class="w"> </span><span class="p" data-group-id="4042311755-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="4042311755-5">]</span><span class="w"> </span><span class="p" data-group-id="4042311755-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4042311755-6">]</span><span class="w"> </span><span class="p" data-group-id="4042311755-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="4042311755-7">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="9340090813-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="9340090813-1">]</span><span class="w"> </span><span class="p" data-group-id="9340090813-2">[</span><span class="ss">source</span><span class="p" data-group-id="9340090813-2">]</span><span class="w"> </span><span class="p" data-group-id="9340090813-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="9340090813-3">]</span><span class="w"> </span><span class="p" data-group-id="9340090813-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="9340090813-4">]</span><span class="w"> </span><span class="p" data-group-id="9340090813-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="9340090813-5">]</span><span class="w"> </span><span class="p" data-group-id="9340090813-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="9340090813-6">]</span><span class="w"> </span><span class="p" data-group-id="9340090813-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="9340090813-7">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="4042311755-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="4042311755-9">(</span><span class="p" data-group-id="4042311755-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="4042311755-8">)</span><span class="w">
│ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="4042311755-10">(</span><span class="ss">complex2</span><span class="p" data-group-id="4042311755-10">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4042311755-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex2</span><span class="p" data-group-id="4042311755-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8689016921-1">(</span><span class="s">&quot;./extprg&quot;</span><span class="p" data-group-id="8689016921-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="9340090813-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="9340090813-9">(</span><span class="p" data-group-id="9340090813-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="9340090813-8">)</span><span class="w">
│ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="9340090813-10">(</span><span class="ss">complex2</span><span class="p" data-group-id="9340090813-10">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9340090813-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex2</span><span class="p" data-group-id="9340090813-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1385650372-1">(</span><span class="s">&quot;./extprg&quot;</span><span class="p" data-group-id="1385650372-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.34</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="8689016921-2">(</span><span class="mi">3</span><span class="p" data-group-id="8689016921-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="1385650372-2">(</span><span class="mi">3</span><span class="p" data-group-id="1385650372-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="8689016921-3">(</span><span class="mi">5</span><span class="p" data-group-id="8689016921-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="1385650372-3">(</span><span class="mi">5</span><span class="p" data-group-id="1385650372-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">10</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="8689016921-4">(</span><span class="mi">352</span><span class="p" data-group-id="8689016921-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="1385650372-4">(</span><span class="mi">352</span><span class="p" data-group-id="1385650372-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">704</span><span class="w">
│ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="8689016921-5">(</span><span class="p" data-group-id="8689016921-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="1385650372-5">(</span><span class="p" data-group-id="1385650372-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">stop</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="c_port.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/errors.html
│ │ │ @@ -151,22 +151,22 @@
│ │ │  classes, with different origins. The <a href="expressions.html#try">try</a> expression can
│ │ │  distinguish between the different classes, whereas the
│ │ │  <a href="expressions.html#catch-and-throw">catch</a> expression cannot. <code class="inline">try</code> and <code class="inline">catch</code> are described
│ │ │  in <a href="expressions.html">Expressions</a>.</p><table><thead><tr><th style="text-align: left;">Class</th><th style="text-align: left;">Origin</th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">error</code></td><td style="text-align: left;">Run-time error, for example, <code class="inline">1+a</code>, or the process called <a href="../../erts-17.0/doc/html/erlang.html#error/1"><code class="inline">error/1</code></a></td></tr><tr><td style="text-align: left;"><code class="inline">exit</code></td><td style="text-align: left;">The process called <a href="../../erts-17.0/doc/html/erlang.html#exit/1"><code class="inline">exit/1</code></a></td></tr><tr><td style="text-align: left;"><code class="inline">throw</code></td><td style="text-align: left;">The process called <a href="../../erts-17.0/doc/html/erlang.html#throw/1"><code class="inline">throw/1</code></a></td></tr></tbody></table><p><em>Table: Exception Classes.</em></p><p>All of the above exceptions can also be generated by calling <a href="../../erts-17.0/doc/html/erlang.html#raise/3"><code class="inline">erlang:raise/3</code></a>.</p><p>An exception consists of its class, an exit reason (see
│ │ │  <a href="errors.html#exit_reasons">Exit Reason</a>), and a stack trace (which aids in finding
│ │ │  the code location of the exception).</p><p>The stack trace can be bound to a variable from within a <code class="inline">try</code> expression for
│ │ │  any exception class, or as part of the exit reason when a run-time error is
│ │ │ -caught by a <code class="inline">catch</code>. Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="1017996920-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="1017996920-2">{</span><span class="ss">test</span><span class="p">,</span><span class="n">Stacktrace</span><span class="p" data-group-id="1017996920-2">}</span><span class="p" data-group-id="1017996920-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1017996920-3">(</span><span class="k">catch</span><span class="w"> </span><span class="nf">error</span><span class="p" data-group-id="1017996920-4">(</span><span class="ss">test</span><span class="p" data-group-id="1017996920-4">)</span><span class="p" data-group-id="1017996920-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Stacktrace</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1017996920-5">[</span><span class="p" data-group-id="1017996920-6">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="1017996920-7">[</span><span class="p" data-group-id="1017996920-7">]</span><span class="p" data-group-id="1017996920-6">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1017996920-8">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="1017996920-9">[</span><span class="p" data-group-id="1017996920-9">]</span><span class="p" data-group-id="1017996920-8">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1017996920-5">]</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="k">try</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="1017996920-10">(</span><span class="ss">test</span><span class="p" data-group-id="1017996920-10">)</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="n">Class</span><span class="p">:</span><span class="n">Reason</span><span class="p">:</span><span class="n">Stacktrace</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Stacktrace</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1017996920-11">[</span><span class="p" data-group-id="1017996920-12">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="1017996920-13">[</span><span class="p" data-group-id="1017996920-13">]</span><span class="p" data-group-id="1017996920-12">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1017996920-14">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="1017996920-15">[</span><span class="p" data-group-id="1017996920-15">]</span><span class="p" data-group-id="1017996920-14">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1017996920-11">]</span></code></pre><p><a href="" id="stacktrace"></a></p><h3 id="the-call-stack-backtrace-stacktrace" class="section-heading">
│ │ │ +caught by a <code class="inline">catch</code>. Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="9077433492-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="9077433492-2">{</span><span class="ss">test</span><span class="p">,</span><span class="n">Stacktrace</span><span class="p" data-group-id="9077433492-2">}</span><span class="p" data-group-id="9077433492-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9077433492-3">(</span><span class="k">catch</span><span class="w"> </span><span class="nf">error</span><span class="p" data-group-id="9077433492-4">(</span><span class="ss">test</span><span class="p" data-group-id="9077433492-4">)</span><span class="p" data-group-id="9077433492-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Stacktrace</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9077433492-5">[</span><span class="p" data-group-id="9077433492-6">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="9077433492-7">[</span><span class="p" data-group-id="9077433492-7">]</span><span class="p" data-group-id="9077433492-6">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9077433492-8">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="9077433492-9">[</span><span class="p" data-group-id="9077433492-9">]</span><span class="p" data-group-id="9077433492-8">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="9077433492-5">]</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="k">try</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="9077433492-10">(</span><span class="ss">test</span><span class="p" data-group-id="9077433492-10">)</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="n">Class</span><span class="p">:</span><span class="n">Reason</span><span class="p">:</span><span class="n">Stacktrace</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Stacktrace</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9077433492-11">[</span><span class="p" data-group-id="9077433492-12">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="9077433492-13">[</span><span class="p" data-group-id="9077433492-13">]</span><span class="p" data-group-id="9077433492-12">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9077433492-14">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="9077433492-15">[</span><span class="p" data-group-id="9077433492-15">]</span><span class="p" data-group-id="9077433492-14">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="9077433492-11">]</span></code></pre><p><a href="" id="stacktrace"></a></p><h3 id="the-call-stack-backtrace-stacktrace" class="section-heading">
│ │ │    <a href="#the-call-stack-backtrace-stacktrace" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">The call-stack backtrace (stacktrace)</span>
│ │ │  </h3>
│ │ │  <p>The stack backtrace (<a href="../../erts-17.0/doc/html/erlang.html#t:stacktrace/0"><em>stacktrace</em></a>) is a list that
│ │ │  contains <code class="inline">{Module, Function, Arity, ExtraInfo}</code> and/or <code class="inline">{Fun, Arity, ExtraInfo}</code>
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/events.html
│ │ │ @@ -135,43 +135,43 @@
│ │ │  event handler.</p><h2 id="example" class="section-heading">
│ │ │    <a href="#example" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Example</span>
│ │ │  </h2>
│ │ │  <p>The callback module for the event handler writing error messages to the terminal
│ │ │ -can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3776595113-1">(</span><span class="ss">terminal_logger</span><span class="p" data-group-id="3776595113-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="3776595113-2">(</span><span class="ss">gen_event</span><span class="p" data-group-id="3776595113-2">)</span><span class="p">.</span><span class="w">
│ │ │ +can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8300739530-1">(</span><span class="ss">terminal_logger</span><span class="p" data-group-id="8300739530-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="8300739530-2">(</span><span class="ss">gen_event</span><span class="p" data-group-id="8300739530-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3776595113-3">(</span><span class="p" data-group-id="3776595113-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3776595113-4">]</span><span class="p" data-group-id="3776595113-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8300739530-3">(</span><span class="p" data-group-id="8300739530-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8300739530-4">]</span><span class="p" data-group-id="8300739530-3">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="3776595113-5">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="3776595113-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3776595113-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3776595113-7">[</span><span class="p" data-group-id="3776595113-7">]</span><span class="p" data-group-id="3776595113-6">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="8300739530-5">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="8300739530-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8300739530-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8300739530-7">[</span><span class="p" data-group-id="8300739530-7">]</span><span class="p" data-group-id="8300739530-6">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="3776595113-8">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="3776595113-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3776595113-9">(</span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3776595113-10">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="3776595113-10">]</span><span class="p" data-group-id="3776595113-9">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3776595113-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="3776595113-11">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8300739530-8">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8300739530-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8300739530-9">(</span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8300739530-10">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="8300739530-10">]</span><span class="p" data-group-id="8300739530-9">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8300739530-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8300739530-11">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="3776595113-12">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="3776595113-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="8300739530-12">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="8300739530-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The callback module for the event handler writing error messages to a file can
│ │ │ -look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7224347939-1">(</span><span class="ss">file_logger</span><span class="p" data-group-id="7224347939-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="7224347939-2">(</span><span class="ss">gen_event</span><span class="p" data-group-id="7224347939-2">)</span><span class="p">.</span><span class="w">
│ │ │ +look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7233474942-1">(</span><span class="ss">file_logger</span><span class="p" data-group-id="7233474942-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="7233474942-2">(</span><span class="ss">gen_event</span><span class="p" data-group-id="7233474942-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7224347939-3">(</span><span class="p" data-group-id="7224347939-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7224347939-4">]</span><span class="p" data-group-id="7224347939-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7233474942-3">(</span><span class="p" data-group-id="7233474942-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7233474942-4">]</span><span class="p" data-group-id="7233474942-3">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="7224347939-5">(</span><span class="n">File</span><span class="p" data-group-id="7224347939-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7224347939-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7224347939-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="7224347939-7">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">read</span><span class="p" data-group-id="7224347939-7">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7224347939-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7224347939-8">}</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="7224347939-9">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7224347939-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7224347939-10">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7224347939-11">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="7224347939-11">]</span><span class="p" data-group-id="7224347939-10">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7224347939-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7224347939-12">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="7233474942-5">(</span><span class="n">File</span><span class="p" data-group-id="7233474942-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7233474942-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7233474942-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="7233474942-7">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">read</span><span class="p" data-group-id="7233474942-7">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7233474942-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7233474942-8">}</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="7233474942-9">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7233474942-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7233474942-10">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7233474942-11">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="7233474942-11">]</span><span class="p" data-group-id="7233474942-10">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7233474942-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7233474942-12">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="7224347939-13">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7224347939-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="7224347939-14">(</span><span class="n">Fd</span><span class="p" data-group-id="7224347939-14">)</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><p><a href="" id="mgr"></a></p><h2 id="starting-an-event-manager" class="section-heading">
│ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="7233474942-13">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7233474942-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="7233474942-14">(</span><span class="n">Fd</span><span class="p" data-group-id="7233474942-14">)</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><p><a href="" id="mgr"></a></p><h2 id="starting-an-event-manager" class="section-heading">
│ │ │    <a href="#starting-an-event-manager" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Starting an Event Manager</span>
│ │ │  </h2>
│ │ │  <p>To start an event manager for handling errors, as described in the previous
│ │ │  example, call the following function:</p><pre><code class="text">gen_event:start_link({local, error_man})</code></pre><p><a href="../../lib/stdlib-8.0/doc/html/gen_event.html#start_link/1"><code class="inline">gen_event:start_link/1</code></a> spawns and links to a new event manager process.</p><p>The argument, <code class="inline">{local, error_man}</code>, specifies the name under which the
│ │ │ @@ -184,57 +184,57 @@
│ │ │  manager that is not part of a supervision tree.</p><h2 id="adding-an-event-handler" class="section-heading">
│ │ │    <a href="#adding-an-event-handler" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Adding an Event Handler</span>
│ │ │  </h2>
│ │ │  <p>The following example shows how to start an event manager and add an event
│ │ │ -handler to it by using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="9941500202-1">(</span><span class="p" data-group-id="9941500202-2">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">error_man</span><span class="p" data-group-id="9941500202-2">}</span><span class="p" data-group-id="9941500202-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9941500202-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.31</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="9941500202-3">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">add_handler</span><span class="p" data-group-id="9941500202-4">(</span><span class="ss">error_man</span><span class="p">,</span><span class="w"> </span><span class="ss">terminal_logger</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9941500202-5">[</span><span class="p" data-group-id="9941500202-5">]</span><span class="p" data-group-id="9941500202-4">)</span><span class="p">.</span><span class="w">
│ │ │ +handler to it by using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="3245669649-1">(</span><span class="p" data-group-id="3245669649-2">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">error_man</span><span class="p" data-group-id="3245669649-2">}</span><span class="p" data-group-id="3245669649-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3245669649-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.31</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="3245669649-3">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">add_handler</span><span class="p" data-group-id="3245669649-4">(</span><span class="ss">error_man</span><span class="p">,</span><span class="w"> </span><span class="ss">terminal_logger</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3245669649-5">[</span><span class="p" data-group-id="3245669649-5">]</span><span class="p" data-group-id="3245669649-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>This function sends a message to the event manager registered as <code class="inline">error_man</code>,
│ │ │  telling it to add the event handler <code class="inline">terminal_logger</code>. The event manager calls
│ │ │  the callback function <code class="inline">terminal_logger:init([])</code>, where the argument <code class="inline">[]</code> is the
│ │ │  third argument to <code class="inline">add_handler</code>. <code class="inline">init/1</code> is expected to return <code class="inline">{ok, State}</code>,
│ │ │ -where <code class="inline">State</code> is the internal state of the event handler.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="8151151802-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="8151151802-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8151151802-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8151151802-3">[</span><span class="p" data-group-id="8151151802-3">]</span><span class="p" data-group-id="8151151802-2">}</span><span class="p">.</span></code></pre><p>Here, <code class="inline">init/1</code> does not need any input data and ignores its argument. For
│ │ │ +where <code class="inline">State</code> is the internal state of the event handler.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="7184479541-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="7184479541-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7184479541-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7184479541-3">[</span><span class="p" data-group-id="7184479541-3">]</span><span class="p" data-group-id="7184479541-2">}</span><span class="p">.</span></code></pre><p>Here, <code class="inline">init/1</code> does not need any input data and ignores its argument. For
│ │ │  <code class="inline">terminal_logger</code>, the internal state is not used. For <code class="inline">file_logger</code>, the
│ │ │ -internal state is used to save the open file descriptor.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="7331518960-1">(</span><span class="n">File</span><span class="p" data-group-id="7331518960-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7331518960-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7331518960-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="7331518960-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">read</span><span class="p" data-group-id="7331518960-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7331518960-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7331518960-4">}</span><span class="p">.</span></code></pre><h2 id="notifying-about-events" class="section-heading">
│ │ │ +internal state is used to save the open file descriptor.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="2222864882-1">(</span><span class="n">File</span><span class="p" data-group-id="2222864882-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2222864882-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="2222864882-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="2222864882-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">read</span><span class="p" data-group-id="2222864882-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2222864882-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="2222864882-4">}</span><span class="p">.</span></code></pre><h2 id="notifying-about-events" class="section-heading">
│ │ │    <a href="#notifying-about-events" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Notifying about Events</span>
│ │ │  </h2>
│ │ │  <pre><code class="text">3&gt; gen_event:notify(error_man, no_reply).
│ │ │  ***Error*** no_reply
│ │ │  ok</code></pre><p><code class="inline">error_man</code> is the name of the event manager and <code class="inline">no_reply</code> is the event.</p><p>The event is made into a message and sent to the event manager. When the event
│ │ │  is received, the event manager calls <code class="inline">handle_event(Event, State)</code> for each
│ │ │  installed event handler, in the same order as they were added. The function is
│ │ │  expected to return a tuple <code class="inline">{ok,State1}</code>, where <code class="inline">State1</code> is a new value for the
│ │ │ -state of the event handler.</p><p>In <code class="inline">terminal_logger</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_event</span><span class="p" data-group-id="4263372383-1">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4263372383-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4263372383-2">(</span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4263372383-3">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="4263372383-3">]</span><span class="p" data-group-id="4263372383-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4263372383-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4263372383-4">}</span><span class="p">.</span></code></pre><p>In <code class="inline">file_logger</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_event</span><span class="p" data-group-id="4216892655-1">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="4216892655-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4216892655-2">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4216892655-3">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="4216892655-3">]</span><span class="p" data-group-id="4216892655-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4216892655-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="4216892655-4">}</span><span class="p">.</span></code></pre><h2 id="deleting-an-event-handler" class="section-heading">
│ │ │ +state of the event handler.</p><p>In <code class="inline">terminal_logger</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_event</span><span class="p" data-group-id="1731246774-1">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="1731246774-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1731246774-2">(</span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1731246774-3">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="1731246774-3">]</span><span class="p" data-group-id="1731246774-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1731246774-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="1731246774-4">}</span><span class="p">.</span></code></pre><p>In <code class="inline">file_logger</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_event</span><span class="p" data-group-id="0139668351-1">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="0139668351-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0139668351-2">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0139668351-3">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="0139668351-3">]</span><span class="p" data-group-id="0139668351-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0139668351-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="0139668351-4">}</span><span class="p">.</span></code></pre><h2 id="deleting-an-event-handler" class="section-heading">
│ │ │    <a href="#deleting-an-event-handler" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Deleting an Event Handler</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">delete_handler</span><span class="p" data-group-id="9870479017-1">(</span><span class="ss">error_man</span><span class="p">,</span><span class="w"> </span><span class="ss">terminal_logger</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9870479017-2">[</span><span class="p" data-group-id="9870479017-2">]</span><span class="p" data-group-id="9870479017-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">delete_handler</span><span class="p" data-group-id="9379734049-1">(</span><span class="ss">error_man</span><span class="p">,</span><span class="w"> </span><span class="ss">terminal_logger</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9379734049-2">[</span><span class="p" data-group-id="9379734049-2">]</span><span class="p" data-group-id="9379734049-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>This function sends a message to the event manager registered as <code class="inline">error_man</code>,
│ │ │  telling it to delete the event handler <code class="inline">terminal_logger</code>. The event manager
│ │ │  calls the callback function <code class="inline">terminal_logger:terminate([], State)</code>, where the
│ │ │  argument <code class="inline">[]</code> is the third argument to <code class="inline">delete_handler</code>. <code class="inline">terminate/2</code> is to be
│ │ │  the opposite of <code class="inline">init/1</code> and do any necessary cleaning up. Its return value is
│ │ │ -ignored.</p><p>For <code class="inline">terminal_logger</code>, no cleaning up is necessary:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="6455003993-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="6455003993-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>For <code class="inline">file_logger</code>, the file descriptor opened in <code class="inline">init</code> must be closed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="2198553713-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="2198553713-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="2198553713-2">(</span><span class="n">Fd</span><span class="p" data-group-id="2198553713-2">)</span><span class="p">.</span></code></pre><h2 id="stopping" class="section-heading">
│ │ │ +ignored.</p><p>For <code class="inline">terminal_logger</code>, no cleaning up is necessary:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="5022329796-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="5022329796-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>For <code class="inline">file_logger</code>, the file descriptor opened in <code class="inline">init</code> must be closed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="7931702911-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7931702911-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="7931702911-2">(</span><span class="n">Fd</span><span class="p" data-group-id="7931702911-2">)</span><span class="p">.</span></code></pre><h2 id="stopping" class="section-heading">
│ │ │    <a href="#stopping" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Stopping</span>
│ │ │  </h2>
│ │ │  <p>When an event manager is stopped, it gives each of the installed event handlers
│ │ │  the chance to clean up by calling <code class="inline">terminate/2</code>, the same way as when deleting a
│ │ │ @@ -249,33 +249,33 @@
│ │ │  this is done is defined by a <a href="sup_princ.html#shutdown">shutdown strategy</a> set in
│ │ │  the supervisor.</p><h3 id="standalone-event-managers" class="section-heading">
│ │ │    <a href="#standalone-event-managers" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Standalone Event Managers</span>
│ │ │  </h3>
│ │ │ -<p>An event manager can also be stopped by calling:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="7202898135-1">(</span><span class="ss">error_man</span><span class="p" data-group-id="7202898135-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>An event manager can also be stopped by calling:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="3130197919-1">(</span><span class="ss">error_man</span><span class="p" data-group-id="3130197919-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><h2 id="handling-other-messages" class="section-heading">
│ │ │    <a href="#handling-other-messages" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Handling Other Messages</span>
│ │ │  </h2>
│ │ │  <p>If the <code class="inline">gen_event</code> process is to be able to receive other messages
│ │ │  than events, the callback function <code class="inline">handle_info(Info, State)</code> must be
│ │ │  implemented to handle them. Examples of other messages are exit
│ │ │  messages if the event manager is linked to other processes than the
│ │ │  supervisor (for example via <a href="../../lib/stdlib-8.0/doc/html/gen_event.html#add_sup_handler/3"><code class="inline">gen_event:add_sup_handler/3</code></a>) and is
│ │ │ -trapping exit signals.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_info</span><span class="p" data-group-id="3444930902-1">(</span><span class="p" data-group-id="3444930902-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="3444930902-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="3444930902-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +trapping exit signals.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_info</span><span class="p" data-group-id="5057538745-1">(</span><span class="p" data-group-id="5057538745-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="5057538745-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5057538745-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Code to handle exits here.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3444930902-3">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="3444930902-3">}</span><span class="p">.</span></code></pre><p>The final function to implement is <code class="inline">code_change/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="8811779199-1">(</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="8811779199-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5057538745-3">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="5057538745-3">}</span><span class="p">.</span></code></pre><p>The final function to implement is <code class="inline">code_change/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="2304832346-1">(</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="2304832346-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Code to convert state (and more) during code change.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8811779199-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NewState</span><span class="p" data-group-id="8811779199-2">}</span><span class="p">.</span></code></pre>
│ │ │ +    </span><span class="p" data-group-id="2304832346-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NewState</span><span class="p" data-group-id="2304832346-2">}</span><span class="p">.</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="statem.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/example.html
│ │ │ @@ -131,15 +131,15 @@
│ │ │  
│ │ │  int bar(int y) {
│ │ │    return y*2;
│ │ │  }</code></pre><p>The functions are deliberately kept as simple as possible, for readability
│ │ │  reasons.</p><p>From an Erlang perspective, it is preferable to be able to call <code class="inline">foo</code> and <code class="inline">bar</code>
│ │ │  without having to bother about that they are C functions:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% Erlang code</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="n">Res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">complex</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="0922118138-1">(</span><span class="n">X</span><span class="p" data-group-id="0922118138-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">complex</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="6461851988-1">(</span><span class="n">X</span><span class="p" data-group-id="6461851988-1">)</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Here, the communication with C is hidden in the implementation of <code class="inline">complex.erl</code>.
│ │ │  In the following sections, it is shown how this module can be implemented using
│ │ │  the different interoperability mechanisms.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/expressions.html
│ │ │ @@ -151,81 +151,81 @@
│ │ │  </span><span class="n">Phone_number</span><span class="w">
│ │ │  </span><span class="p">_</span><span class="w">
│ │ │  </span><span class="p">_</span><span class="n">Height</span><span class="w">
│ │ │  </span><span class="ss">name@node</span></code></pre><p>Variables are bound to values using <a href="patterns.html">pattern matching</a>. Erlang uses
│ │ │  <em>single assignment</em>, that is, a variable can only be bound once.</p><p>The <em>anonymous variable</em> is denoted by underscore (_) and can be used when a
│ │ │  variable is required but its value can be ignored.</p><p><em>Example:</em></p><pre><code class="text">[H|_] = [1,2,3]</code></pre><p>Variables starting with underscore (<code class="inline">_</code>), for example, <code class="inline">_Height</code>, are normal
│ │ │  variables, not anonymous. However, they are ignored by the compiler in the sense
│ │ │ -that they do not generate warnings.</p><p><em>Example:</em></p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="2435658676-1">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2435658676-2">[</span><span class="p" data-group-id="2435658676-2">]</span><span class="p" data-group-id="2435658676-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2435658676-3">[</span><span class="p" data-group-id="2435658676-3">]</span><span class="p">.</span></code></pre><p>can be rewritten to be more readable:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="6234918450-1">(</span><span class="n">Elem</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6234918450-2">[</span><span class="p" data-group-id="6234918450-2">]</span><span class="p" data-group-id="6234918450-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6234918450-3">[</span><span class="p" data-group-id="6234918450-3">]</span><span class="p">.</span></code></pre><p>This causes a warning for an unused variable, <code class="inline">Elem</code>. To avoid the warning,
│ │ │ -the code can be rewritten to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="9204780831-1">(</span><span class="p">_</span><span class="n">Elem</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9204780831-2">[</span><span class="p" data-group-id="9204780831-2">]</span><span class="p" data-group-id="9204780831-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9204780831-3">[</span><span class="p" data-group-id="9204780831-3">]</span><span class="p">.</span></code></pre><p>Notice that since variables starting with an underscore are not anonymous, the
│ │ │ -following example matches:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9138301207-1">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9138301207-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9138301207-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9138301207-2">}</span></code></pre><p>But this example fails:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2133739531-1">{</span><span class="p">_</span><span class="n">N</span><span class="p">,</span><span class="p">_</span><span class="n">N</span><span class="p" data-group-id="2133739531-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2133739531-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2133739531-2">}</span></code></pre><p>The scope for a variable is its function clause. Variables bound in a branch of
│ │ │ +that they do not generate warnings.</p><p><em>Example:</em></p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="8938184296-1">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8938184296-2">[</span><span class="p" data-group-id="8938184296-2">]</span><span class="p" data-group-id="8938184296-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8938184296-3">[</span><span class="p" data-group-id="8938184296-3">]</span><span class="p">.</span></code></pre><p>can be rewritten to be more readable:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="3812145540-1">(</span><span class="n">Elem</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3812145540-2">[</span><span class="p" data-group-id="3812145540-2">]</span><span class="p" data-group-id="3812145540-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3812145540-3">[</span><span class="p" data-group-id="3812145540-3">]</span><span class="p">.</span></code></pre><p>This causes a warning for an unused variable, <code class="inline">Elem</code>. To avoid the warning,
│ │ │ +the code can be rewritten to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="6722387436-1">(</span><span class="p">_</span><span class="n">Elem</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6722387436-2">[</span><span class="p" data-group-id="6722387436-2">]</span><span class="p" data-group-id="6722387436-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6722387436-3">[</span><span class="p" data-group-id="6722387436-3">]</span><span class="p">.</span></code></pre><p>Notice that since variables starting with an underscore are not anonymous, the
│ │ │ +following example matches:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8351322252-1">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="8351322252-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8351322252-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8351322252-2">}</span></code></pre><p>But this example fails:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2939695326-1">{</span><span class="p">_</span><span class="n">N</span><span class="p">,</span><span class="p">_</span><span class="n">N</span><span class="p" data-group-id="2939695326-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2939695326-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2939695326-2">}</span></code></pre><p>The scope for a variable is its function clause. Variables bound in a branch of
│ │ │  an <code class="inline">if</code>, <code class="inline">case</code>, or <code class="inline">receive</code> expression must be bound in all branches to have a
│ │ │  value outside the expression. Otherwise they are regarded as unsafe outside
│ │ │  the expression.</p><p>For the <code class="inline">try</code> expression, variable scoping is limited so that variables bound in
│ │ │  the expression are always unsafe outside the expression.</p><h2 id="patterns" class="section-heading">
│ │ │    <a href="#patterns" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Patterns</span>
│ │ │  </h2>
│ │ │  <p>A pattern has the same structure as a term but can contain unbound variables.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">Name1</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2585800406-1">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2585800406-1">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2585800406-2">{</span><span class="ss">error</span><span class="p">,</span><span class="n">Reason</span><span class="p" data-group-id="2585800406-2">}</span></code></pre><p>Patterns are allowed in clause heads, <a href="expressions.html#case">case expressions</a>,
│ │ │ +</span><span class="p" data-group-id="5882417391-1">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5882417391-1">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5882417391-2">{</span><span class="ss">error</span><span class="p">,</span><span class="n">Reason</span><span class="p" data-group-id="5882417391-2">}</span></code></pre><p>Patterns are allowed in clause heads, <a href="expressions.html#case">case expressions</a>,
│ │ │  <a href="expressions.html#receive">receive expressions</a>, and
│ │ │  <a href="expressions.html#the-match-operator">match expressions</a>.</p><h3 id="the-compound-pattern-operator" class="section-heading">
│ │ │    <a href="#the-compound-pattern-operator" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">The Compound Pattern Operator</span>
│ │ │  </h3>
│ │ │  <p>If <code class="inline">Pattern1</code> and <code class="inline">Pattern2</code> are valid patterns, the following is also a valid
│ │ │  pattern:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Pattern2</span></code></pre><p>When matched against a term, both <code class="inline">Pattern1</code> and <code class="inline">Pattern2</code> are matched against
│ │ │ -the term. The idea behind this feature is to avoid reconstruction of terms.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="7967113468-1">(</span><span class="p" data-group-id="7967113468-2">{</span><span class="ss">connect</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="n">Number</span><span class="p">,</span><span class="n">Options</span><span class="p" data-group-id="7967113468-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="7967113468-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Signal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7967113468-3">{</span><span class="ss">connect</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="n">Number</span><span class="p">,</span><span class="n">Options</span><span class="p" data-group-id="7967113468-3">}</span><span class="p">,</span><span class="w">
│ │ │ +the term. The idea behind this feature is to avoid reconstruction of terms.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="9993687229-1">(</span><span class="p" data-group-id="9993687229-2">{</span><span class="ss">connect</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="n">Number</span><span class="p">,</span><span class="n">Options</span><span class="p" data-group-id="9993687229-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="9993687229-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Signal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9993687229-3">{</span><span class="ss">connect</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="n">Number</span><span class="p">,</span><span class="n">Options</span><span class="p" data-group-id="9993687229-3">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="7967113468-4">(</span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="7967113468-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ignore</span><span class="p">.</span></code></pre><p>can instead be written as</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="8944731906-1">(</span><span class="p" data-group-id="8944731906-2">{</span><span class="ss">connect</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="8944731906-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="8944731906-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="9993687229-4">(</span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="9993687229-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ignore</span><span class="p">.</span></code></pre><p>can instead be written as</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="8711575096-1">(</span><span class="p" data-group-id="8711575096-2">{</span><span class="ss">connect</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="8711575096-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="8711575096-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="8944731906-3">(</span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="8944731906-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="8711575096-3">(</span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="8711575096-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">ignore</span><span class="p">.</span></code></pre><p>The compound pattern operator does not imply that its operands are matched in
│ │ │  any particular order. That means that it is not legal to bind a variable in
│ │ │  <code class="inline">Pattern1</code> and use it in <code class="inline">Pattern2</code>, or vice versa.</p><h3 id="string-prefix-in-patterns" class="section-heading">
│ │ │    <a href="#string-prefix-in-patterns" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">String Prefix in Patterns</span>
│ │ │  </h3>
│ │ │ -<p>When matching strings, the following is a valid pattern:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="9681354140-1">(</span><span class="s">&quot;prefix&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Str</span><span class="p" data-group-id="9681354140-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>This is syntactic sugar for the equivalent, but harder to read:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="2301082322-1">(</span><span class="p" data-group-id="2301082322-2">[</span><span class="sc">$p</span><span class="p">,</span><span class="sc">$r</span><span class="p">,</span><span class="sc">$e</span><span class="p">,</span><span class="sc">$f</span><span class="p">,</span><span class="sc">$i</span><span class="p">,</span><span class="sc">$x</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Str</span><span class="p" data-group-id="2301082322-2">]</span><span class="p" data-group-id="2301082322-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h3 id="expressions-in-patterns" class="section-heading">
│ │ │ +<p>When matching strings, the following is a valid pattern:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="7795286676-1">(</span><span class="s">&quot;prefix&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Str</span><span class="p" data-group-id="7795286676-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>This is syntactic sugar for the equivalent, but harder to read:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="9687321360-1">(</span><span class="p" data-group-id="9687321360-2">[</span><span class="sc">$p</span><span class="p">,</span><span class="sc">$r</span><span class="p">,</span><span class="sc">$e</span><span class="p">,</span><span class="sc">$f</span><span class="p">,</span><span class="sc">$i</span><span class="p">,</span><span class="sc">$x</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Str</span><span class="p" data-group-id="9687321360-2">]</span><span class="p" data-group-id="9687321360-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h3 id="expressions-in-patterns" class="section-heading">
│ │ │    <a href="#expressions-in-patterns" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Expressions in Patterns</span>
│ │ │  </h3>
│ │ │  <p>An arithmetic expression can be used within a pattern if it meets both of the
│ │ │ -following two conditions:</p><ul><li>It uses only numeric or bitwise operators.</li><li>Its value can be evaluated to a constant when compiled.</li></ul><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="p" data-group-id="7127271105-1">{</span><span class="n">Value</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7127271105-1">}</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7127271105-2">{</span><span class="o">?</span><span class="n">THRESHOLD</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="7127271105-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="the-match-operator" class="section-heading">
│ │ │ +following two conditions:</p><ul><li>It uses only numeric or bitwise operators.</li><li>Its value can be evaluated to a constant when compiled.</li></ul><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="p" data-group-id="6399618473-1">{</span><span class="n">Value</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="6399618473-1">}</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6399618473-2">{</span><span class="o">?</span><span class="n">THRESHOLD</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="6399618473-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="the-match-operator" class="section-heading">
│ │ │    <a href="#the-match-operator" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">The Match Operator</span>
│ │ │  </h2>
│ │ │  <p>The following matches <code class="inline">Pattern</code> against <code class="inline">Expr</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expr</span></code></pre><p>If the matching succeeds, any unbound variable in the pattern becomes bound and
│ │ │  the value of <code class="inline">Expr</code> is returned.</p><p>If multiple match operators are applied in sequence, they will be evaluated from
│ │ │ -right to left.</p><p>If the matching fails, a <code class="inline">badmatch</code> run-time error occurs.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5432580337-1">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="5432580337-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5432580337-2">{</span><span class="ss">answer</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="5432580337-2">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5432580337-3">{</span><span class="ss">answer</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="5432580337-3">}</span><span class="w">
│ │ │ +right to left.</p><p>If the matching fails, a <code class="inline">badmatch</code> run-time error occurs.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4422944249-1">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="4422944249-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4422944249-2">{</span><span class="ss">answer</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="4422944249-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4422944249-3">{</span><span class="ss">answer</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="4422944249-3">}</span><span class="w">
│ │ │  </span><span class="gp unselectable">2&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">answer</span><span class="w">
│ │ │  </span><span class="gp unselectable">3&gt; </span><span class="n">B</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">42</span><span class="w">
│ │ │  </span><span class="gp unselectable">4&gt; </span><span class="n">T</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5432580337-4">{</span><span class="ss">answer</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="5432580337-4">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="5432580337-5">{</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="5432580337-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5432580337-6">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="5432580337-6">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4422944249-4">{</span><span class="ss">answer</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="4422944249-4">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="4422944249-5">{</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="4422944249-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4422944249-6">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="4422944249-6">]</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no match of right-hand side value [1,2]</span></code></pre><p>Because multiple match operators are evaluated from right to left, it means
│ │ │  that:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Pattern2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">PatternN</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expression</span></code></pre><p>is equivalent to:</p><pre><code class="makeup erlang" translate="no"><span class="n">Temporary</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expression</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="n">PatternN</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Temporary</span><span class="p">,</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="n">Pattern2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Temporary</span><span class="p">,</span><span class="w">
│ │ │ @@ -239,30 +239,30 @@
│ │ │  can safely be skipped on a first reading.</p></section><p>The <code class="inline">=</code> character is used to denote two similar but distinct operators: the
│ │ │  match operator and the compound pattern operator. Which one is meant is
│ │ │  determined by context.</p><p>The <em>compound pattern operator</em> is used to construct a compound pattern from two
│ │ │  patterns. Compound patterns are accepted everywhere a pattern is accepted. A
│ │ │  compound pattern matches if all of its constituent patterns match. It is not
│ │ │  legal for a pattern that is part of a compound pattern to use variables (as keys
│ │ │  in map patterns or sizes in binary patterns) bound in other sub patterns of the
│ │ │ -same compound pattern.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">fun</span><span class="p" data-group-id="3524069829-1">(</span><span class="p" data-group-id="3524069829-2">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="3524069829-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3524069829-3">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="3524069829-3">}</span><span class="p" data-group-id="3524069829-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Value</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +same compound pattern.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">fun</span><span class="p" data-group-id="6780502910-1">(</span><span class="p" data-group-id="6780502910-2">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="6780502910-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6780502910-3">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="6780502910-3">}</span><span class="p" data-group-id="6780502910-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Value</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">* 1:7: variable &#39;Key&#39; is unbound</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3524069829-4">(</span><span class="p" data-group-id="3524069829-5">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="3524069829-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">E</span><span class="p" data-group-id="3524069829-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3524069829-6">{</span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="3524069829-6">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="3524069829-7">(</span><span class="p" data-group-id="3524069829-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3524069829-8">}</span><span class="p" data-group-id="3524069829-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3524069829-9">{</span><span class="p" data-group-id="3524069829-10">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3524069829-10">}</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3524069829-9">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="n">G</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3524069829-11">(</span><span class="p" data-group-id="3524069829-12">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">B</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="3524069829-12">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3524069829-13">&lt;&lt;</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="3524069829-13">&gt;&gt;</span><span class="p" data-group-id="3524069829-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3524069829-14">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="3524069829-14">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">G</span><span class="p" data-group-id="3524069829-15">(</span><span class="p" data-group-id="3524069829-16">&lt;&lt;</span><span class="mi">42</span><span class="p">,</span><span class="mi">43</span><span class="p" data-group-id="3524069829-16">&gt;&gt;</span><span class="p" data-group-id="3524069829-15">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3524069829-17">{</span><span class="mi">42</span><span class="p">,</span><span class="mi">43</span><span class="p">,</span><span class="mi">10795</span><span class="p" data-group-id="3524069829-17">}</span></code></pre><p>The <em>match operator</em> is allowed everywhere an expression is allowed. It is used
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="6780502910-4">(</span><span class="p" data-group-id="6780502910-5">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="6780502910-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">E</span><span class="p" data-group-id="6780502910-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6780502910-6">{</span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="6780502910-6">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="6780502910-7">(</span><span class="p" data-group-id="6780502910-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6780502910-8">}</span><span class="p" data-group-id="6780502910-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6780502910-9">{</span><span class="p" data-group-id="6780502910-10">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6780502910-10">}</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6780502910-9">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="n">G</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="6780502910-11">(</span><span class="p" data-group-id="6780502910-12">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">B</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="6780502910-12">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6780502910-13">&lt;&lt;</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="6780502910-13">&gt;&gt;</span><span class="p" data-group-id="6780502910-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6780502910-14">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="6780502910-14">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">G</span><span class="p" data-group-id="6780502910-15">(</span><span class="p" data-group-id="6780502910-16">&lt;&lt;</span><span class="mi">42</span><span class="p">,</span><span class="mi">43</span><span class="p" data-group-id="6780502910-16">&gt;&gt;</span><span class="p" data-group-id="6780502910-15">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6780502910-17">{</span><span class="mi">42</span><span class="p">,</span><span class="mi">43</span><span class="p">,</span><span class="mi">10795</span><span class="p" data-group-id="6780502910-17">}</span></code></pre><p>The <em>match operator</em> is allowed everywhere an expression is allowed. It is used
│ │ │  to match the value of an expression to a pattern. If multiple match operators
│ │ │ -are applied in sequence, they will be evaluated from right to left.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0606400476-1">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">key2</span><span class="p">,</span><span class="w"> </span><span class="ss">key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="0606400476-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0606400476-2">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">key2</span><span class="p">,</span><span class="ss">key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="0606400476-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">f</span><span class="p" data-group-id="0606400476-3">(</span><span class="n">Key</span><span class="p" data-group-id="0606400476-3">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0606400476-4">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="0606400476-4">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0606400476-5">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="0606400476-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ +are applied in sequence, they will be evaluated from right to left.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1702523649-1">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">key2</span><span class="p">,</span><span class="w"> </span><span class="ss">key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="1702523649-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1702523649-2">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">key2</span><span class="p">,</span><span class="ss">key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="1702523649-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">f</span><span class="p" data-group-id="1702523649-3">(</span><span class="n">Key</span><span class="p" data-group-id="1702523649-3">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1702523649-4">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="1702523649-4">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1702523649-5">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="1702523649-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">value</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">f</span><span class="p" data-group-id="0606400476-6">(</span><span class="n">Key</span><span class="p" data-group-id="0606400476-6">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0606400476-7">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="0606400476-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0606400476-8">(</span><span class="p" data-group-id="0606400476-9">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="0606400476-9">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p" data-group-id="0606400476-8">)</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">f</span><span class="p" data-group-id="1702523649-6">(</span><span class="n">Key</span><span class="p" data-group-id="1702523649-6">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1702523649-7">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="1702523649-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1702523649-8">(</span><span class="p" data-group-id="1702523649-9">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="1702523649-9">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p" data-group-id="1702523649-8">)</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">value</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nf">f</span><span class="p" data-group-id="0606400476-10">(</span><span class="n">Key</span><span class="p" data-group-id="0606400476-10">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0606400476-11">(</span><span class="p" data-group-id="0606400476-12">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="0606400476-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0606400476-13">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="0606400476-13">}</span><span class="p" data-group-id="0606400476-11">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nf">f</span><span class="p" data-group-id="1702523649-10">(</span><span class="n">Key</span><span class="p" data-group-id="1702523649-10">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1702523649-11">(</span><span class="p" data-group-id="1702523649-12">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="1702523649-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1702523649-13">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="1702523649-13">}</span><span class="p" data-group-id="1702523649-11">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">* 1:12: variable &#39;Key&#39; is unbound</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="0606400476-14">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">Y</span><span class="p" data-group-id="0606400476-14">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">begin</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0606400476-15">&lt;&lt;</span><span class="mi">42</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="0606400476-15">&gt;&gt;</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="1702523649-14">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">Y</span><span class="p" data-group-id="1702523649-14">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">begin</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1702523649-15">&lt;&lt;</span><span class="mi">42</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="1702523649-15">&gt;&gt;</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">42</span></code></pre><p>The expression at prompt <code class="inline">2&gt;</code> first matches the value of variable <code class="inline">M</code> against
│ │ │  pattern <code class="inline">#{key := Key}</code>, binding variable <code class="inline">Key</code>. It then matches the value of
│ │ │  <code class="inline">M</code> against pattern <code class="inline">#{Key := Value}</code> using variable <code class="inline">Key</code> as the key, binding
│ │ │  variable <code class="inline">Value</code>.</p><p>The expression at prompt <code class="inline">3&gt;</code> matches expression <code class="inline">(#{key := Key} = M)</code> against
│ │ │  pattern <code class="inline">#{Key := Value}</code>. The expression inside the parentheses is evaluated
│ │ │  first. That is, <code class="inline">M</code> is matched against <code class="inline">#{key := Key}</code>, and then the value of
│ │ │  <code class="inline">M</code> is matched against pattern <code class="inline">#{Key := Value}</code>. That is the same evaluation
│ │ │ @@ -276,30 +276,30 @@
│ │ │  binding variable <code class="inline">Y</code> and creating a binary. The binary is then matched against
│ │ │  pattern <code class="inline">&lt;&lt;X:Y&gt;&gt;</code> using the value of <code class="inline">Y</code> as the size of the segment.</p><h2 id="function-calls" class="section-heading">
│ │ │    <a href="#function-calls" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Function Calls</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="n">ExprM</span><span class="p">:</span><span class="n">ExprF</span><span class="p" data-group-id="3700224431-1">(</span><span class="n">Expr1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ExprN</span><span class="p" data-group-id="3700224431-1">)</span><span class="w">
│ │ │ -</span><span class="n">ExprF</span><span class="p" data-group-id="3700224431-2">(</span><span class="n">Expr1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ExprN</span><span class="p" data-group-id="3700224431-2">)</span></code></pre><p>In the first form of function calls, <code class="inline">ExprM:ExprF(Expr1,...,ExprN)</code>, each of
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="n">ExprM</span><span class="p">:</span><span class="n">ExprF</span><span class="p" data-group-id="9584956139-1">(</span><span class="n">Expr1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ExprN</span><span class="p" data-group-id="9584956139-1">)</span><span class="w">
│ │ │ +</span><span class="n">ExprF</span><span class="p" data-group-id="9584956139-2">(</span><span class="n">Expr1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ExprN</span><span class="p" data-group-id="9584956139-2">)</span></code></pre><p>In the first form of function calls, <code class="inline">ExprM:ExprF(Expr1,...,ExprN)</code>, each of
│ │ │  <code class="inline">ExprM</code> and <code class="inline">ExprF</code> must be an atom or an expression that evaluates to an atom.
│ │ │  The function is said to be called by using the <em>fully qualified function name</em>.
│ │ │ -This is often referred to as a <em>remote</em> or <em>external function call</em>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="3101845339-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="3101845339-1">)</span></code></pre><p>In the second form of function calls, <code class="inline">ExprF(Expr1,...,ExprN)</code>, <code class="inline">ExprF</code> must be
│ │ │ +This is often referred to as a <em>remote</em> or <em>external function call</em>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="0198672796-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="0198672796-1">)</span></code></pre><p>In the second form of function calls, <code class="inline">ExprF(Expr1,...,ExprN)</code>, <code class="inline">ExprF</code> must be
│ │ │  an atom or evaluate to a fun.</p><p>If <code class="inline">ExprF</code> is an atom, the function is said to be called by using the
│ │ │  <em>implicitly qualified function name</em>. If the function <code class="inline">ExprF</code> is locally
│ │ │  defined, it is called. Alternatively, if <code class="inline">ExprF</code> is explicitly imported from the
│ │ │  <code class="inline">M</code> module, <code class="inline">M:ExprF(Expr1,...,ExprN)</code> is called. If <code class="inline">ExprF</code> is neither declared
│ │ │  locally nor explicitly imported, <code class="inline">ExprF</code> must be the name of an automatically
│ │ │ -imported BIF.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle</span><span class="p" data-group-id="7368072849-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="7368072849-1">)</span><span class="w">
│ │ │ -</span><span class="nf">spawn</span><span class="p" data-group-id="7368072849-2">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7368072849-3">[</span><span class="p" data-group-id="7368072849-3">]</span><span class="p" data-group-id="7368072849-2">)</span></code></pre><p><em>Examples</em> where <code class="inline">ExprF</code> is a fun:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="6447321697-1">(</span><span class="n">X</span><span class="p" data-group-id="6447321697-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Fun1</span><span class="p" data-group-id="6447321697-2">(</span><span class="mi">3</span><span class="p" data-group-id="6447321697-2">)</span><span class="p">.</span><span class="w">
│ │ │ +imported BIF.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle</span><span class="p" data-group-id="6391362400-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="6391362400-1">)</span><span class="w">
│ │ │ +</span><span class="nf">spawn</span><span class="p" data-group-id="6391362400-2">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6391362400-3">[</span><span class="p" data-group-id="6391362400-3">]</span><span class="p" data-group-id="6391362400-2">)</span></code></pre><p><em>Examples</em> where <code class="inline">ExprF</code> is a fun:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="1332562648-1">(</span><span class="n">X</span><span class="p" data-group-id="1332562648-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Fun1</span><span class="p" data-group-id="1332562648-2">(</span><span class="mi">3</span><span class="p" data-group-id="1332562648-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="k">fun</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="ss">append</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6447321697-3">(</span><span class="p" data-group-id="6447321697-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6447321697-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6447321697-5">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6447321697-5">]</span><span class="p" data-group-id="6447321697-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6447321697-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6447321697-6">]</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="k">fun</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="ss">append</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1332562648-3">(</span><span class="p" data-group-id="1332562648-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1332562648-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1332562648-5">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="1332562648-5">]</span><span class="p" data-group-id="1332562648-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1332562648-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="1332562648-6">]</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="o">&gt;</span></code></pre><p>Notice that when calling a local function, there is a difference between using
│ │ │  the implicitly or fully qualified function name. The latter always refers to the
│ │ │  latest version of the module. See
│ │ │  <a href="code_loading.html">Compilation and Code Loading</a> and
│ │ │  <a href="ref_man_functions.html#eval">Function Evaluation</a>.</p><h3 id="local-function-names-clashing-with-auto-imported-bifs" class="section-heading">
│ │ │    <a href="#local-function-names-clashing-with-auto-imported-bifs" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -316,40 +316,40 @@
│ │ │  called instead. This is to avoid that future additions to the set of
│ │ │  auto-imported BIFs silently change the behavior of old code.</p></section><p>However, to avoid old (pre R14) code changing its behavior when compiled
│ │ │  with Erlang/OTP version R14A or later, the following restriction applies: If you
│ │ │  override the name of a BIF that was auto-imported in OTP versions prior to R14A
│ │ │  (ERTS version 5.8) and have an implicitly qualified call to that function in
│ │ │  your code, you either need to explicitly remove the auto-import using a compiler
│ │ │  directive, or replace the call with a fully qualified function call. Otherwise
│ │ │ -you get a compilation error. See the following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3350664545-1">(</span><span class="p" data-group-id="3350664545-2">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">f</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3350664545-2">]</span><span class="p" data-group-id="3350664545-1">)</span><span class="p">.</span><span class="w">
│ │ │ +you get a compilation error. See the following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9306948540-1">(</span><span class="p" data-group-id="9306948540-2">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">f</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9306948540-2">]</span><span class="p" data-group-id="9306948540-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="3350664545-3">(</span><span class="p" data-group-id="3350664545-4">{</span><span class="ss">no_auto_import</span><span class="p">,</span><span class="p" data-group-id="3350664545-5">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3350664545-5">]</span><span class="p" data-group-id="3350664545-4">}</span><span class="p" data-group-id="3350664545-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% erlang:length/1 no longer autoimported</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="9306948540-3">(</span><span class="p" data-group-id="9306948540-4">{</span><span class="ss">no_auto_import</span><span class="p">,</span><span class="p" data-group-id="9306948540-5">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9306948540-5">]</span><span class="p" data-group-id="9306948540-4">}</span><span class="p" data-group-id="9306948540-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% erlang:length/1 no longer autoimported</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">length</span><span class="p" data-group-id="3350664545-6">(</span><span class="p" data-group-id="3350664545-7">[</span><span class="p" data-group-id="3350664545-7">]</span><span class="p" data-group-id="3350664545-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">length</span><span class="p" data-group-id="9306948540-6">(</span><span class="p" data-group-id="9306948540-7">[</span><span class="p" data-group-id="9306948540-7">]</span><span class="p" data-group-id="9306948540-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="mi">0</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">length</span><span class="p" data-group-id="3350664545-8">(</span><span class="p" data-group-id="3350664545-9">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3350664545-9">]</span><span class="p" data-group-id="3350664545-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="3350664545-10">(</span><span class="n">T</span><span class="p" data-group-id="3350664545-10">)</span><span class="p">.</span><span class="w"> </span><span class="c1">%% Calls the local function length/1</span><span class="w">
│ │ │ +</span><span class="nf">length</span><span class="p" data-group-id="9306948540-8">(</span><span class="p" data-group-id="9306948540-9">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9306948540-9">]</span><span class="p" data-group-id="9306948540-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="9306948540-10">(</span><span class="n">T</span><span class="p" data-group-id="9306948540-10">)</span><span class="p">.</span><span class="w"> </span><span class="c1">%% Calls the local function length/1</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="3350664545-11">(</span><span class="n">X</span><span class="p" data-group-id="3350664545-11">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="3350664545-12">(</span><span class="n">X</span><span class="p" data-group-id="3350664545-12">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">%% Calls erlang:length/1,</span><span class="w">
│ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="9306948540-11">(</span><span class="n">X</span><span class="p" data-group-id="9306948540-11">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="9306948540-12">(</span><span class="n">X</span><span class="p" data-group-id="9306948540-12">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">%% Calls erlang:length/1,</span><span class="w">
│ │ │                                    </span><span class="c1">%% which is allowed in guards</span><span class="w">
│ │ │      </span><span class="ss">long</span><span class="p">.</span></code></pre><p>The same logic applies to explicitly imported functions from other modules, as
│ │ │  to locally defined functions. It is not allowed to both import a function from
│ │ │ -another module and have the function declared in the module at the same time:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7181219094-1">(</span><span class="p" data-group-id="7181219094-2">[</span><span class="ss">f</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7181219094-2">]</span><span class="p" data-group-id="7181219094-1">)</span><span class="p">.</span><span class="w">
│ │ │ +another module and have the function declared in the module at the same time:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1886375027-1">(</span><span class="p" data-group-id="1886375027-2">[</span><span class="ss">f</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1886375027-2">]</span><span class="p" data-group-id="1886375027-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="7181219094-3">(</span><span class="p" data-group-id="7181219094-4">{</span><span class="ss">no_auto_import</span><span class="p">,</span><span class="p" data-group-id="7181219094-5">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7181219094-5">]</span><span class="p" data-group-id="7181219094-4">}</span><span class="p" data-group-id="7181219094-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% erlang:length/1 no longer autoimported</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="1886375027-3">(</span><span class="p" data-group-id="1886375027-4">{</span><span class="ss">no_auto_import</span><span class="p">,</span><span class="p" data-group-id="1886375027-5">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1886375027-5">]</span><span class="p" data-group-id="1886375027-4">}</span><span class="p" data-group-id="1886375027-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% erlang:length/1 no longer autoimported</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">import</span><span class="p" data-group-id="7181219094-6">(</span><span class="ss">mod</span><span class="p">,</span><span class="p" data-group-id="7181219094-7">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7181219094-7">]</span><span class="p" data-group-id="7181219094-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">import</span><span class="p" data-group-id="1886375027-6">(</span><span class="ss">mod</span><span class="p">,</span><span class="p" data-group-id="1886375027-7">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1886375027-7">]</span><span class="p" data-group-id="1886375027-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="7181219094-8">(</span><span class="n">X</span><span class="p" data-group-id="7181219094-8">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="7181219094-9">(</span><span class="n">X</span><span class="p" data-group-id="7181219094-9">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">33</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">%% Calls erlang:length/1,</span><span class="w">
│ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="1886375027-8">(</span><span class="n">X</span><span class="p" data-group-id="1886375027-8">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="1886375027-9">(</span><span class="n">X</span><span class="p" data-group-id="1886375027-9">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">33</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">%% Calls erlang:length/1,</span><span class="w">
│ │ │                                     </span><span class="c1">%% which is allowed in guards</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="7181219094-10">(</span><span class="n">X</span><span class="p" data-group-id="7181219094-10">)</span><span class="p">;</span><span class="w">              </span><span class="c1">%% Explicit call to erlang:length in body</span><span class="w">
│ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="1886375027-10">(</span><span class="n">X</span><span class="p" data-group-id="1886375027-10">)</span><span class="p">;</span><span class="w">              </span><span class="c1">%% Explicit call to erlang:length in body</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="7181219094-11">(</span><span class="n">X</span><span class="p" data-group-id="7181219094-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">length</span><span class="p" data-group-id="7181219094-12">(</span><span class="n">X</span><span class="p" data-group-id="7181219094-12">)</span><span class="p">.</span><span class="w">                     </span><span class="c1">%% mod:length/1 is called</span></code></pre><p>For auto-imported BIFs added in Erlang/OTP R14A and thereafter, overriding the
│ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="1886375027-11">(</span><span class="n">X</span><span class="p" data-group-id="1886375027-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">length</span><span class="p" data-group-id="1886375027-12">(</span><span class="n">X</span><span class="p" data-group-id="1886375027-12">)</span><span class="p">.</span><span class="w">                     </span><span class="c1">%% mod:length/1 is called</span></code></pre><p>For auto-imported BIFs added in Erlang/OTP R14A and thereafter, overriding the
│ │ │  name with a local function or explicit import is always allowed. However, if the
│ │ │  <code class="inline">-compile({no_auto_import,[F/A]})</code> directive is not used, the compiler issues a
│ │ │  warning whenever the function is called in the module using the implicitly
│ │ │  qualified function name.</p><h2 id="if" class="section-heading">
│ │ │    <a href="#if" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -361,40 +361,40 @@
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">GuardSeqN</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>The branches of an <code class="inline">if</code>-expression are scanned sequentially until a guard
│ │ │  sequence <code class="inline">GuardSeq</code> that evaluates to true is found. Then the corresponding
│ │ │  <code class="inline">Body</code> (a sequence of expressions separated by <code class="inline">,</code>) is evaluated.</p><p>The return value of <code class="inline">Body</code> is the return value of the <code class="inline">if</code> expression.</p><p>If no guard sequence is evaluated as true, an <code class="inline">if_clause</code> run-time error occurs.
│ │ │  If necessary, the guard expression <code class="inline">true</code> can be used in the last branch, as
│ │ │ -that guard sequence is always true.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_greater_than</span><span class="p" data-group-id="5738173853-1">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5738173853-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +that guard sequence is always true.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_greater_than</span><span class="p" data-group-id="6923178916-1">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6923178916-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% works as an &#39;else&#39; branch</span><span class="w">
│ │ │              </span><span class="ss">false</span><span class="w">
│ │ │      </span><span class="k">end</span></code></pre><h2 id="case" class="section-heading">
│ │ │    <a href="#case" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Case</span>
│ │ │  </h2>
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="n">Expr</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="6548335148-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="6548335148-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="4196199966-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="4196199966-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="6548335148-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="6548335148-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="4196199966-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="4196199966-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>The expression <code class="inline">Expr</code> is evaluated and the patterns <code class="inline">Pattern</code> are sequentially
│ │ │  matched against the result. If a match succeeds and the optional guard sequence
│ │ │  <code class="inline">GuardSeq</code> is true, the corresponding <code class="inline">Body</code> is evaluated.</p><p>The return value of <code class="inline">Body</code> is the return value of the <code class="inline">case</code> expression.</p><p>If there is no matching pattern with a true guard sequence, a <code class="inline">case_clause</code>
│ │ │ -run-time error occurs.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_valid_signal</span><span class="p" data-group-id="1099294387-1">(</span><span class="n">Signal</span><span class="p" data-group-id="1099294387-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +run-time error occurs.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_valid_signal</span><span class="p" data-group-id="9233703090-1">(</span><span class="n">Signal</span><span class="p" data-group-id="9233703090-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Signal</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="1099294387-2">{</span><span class="ss">signal</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">To</span><span class="p" data-group-id="1099294387-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9233703090-2">{</span><span class="ss">signal</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">To</span><span class="p" data-group-id="9233703090-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="1099294387-3">{</span><span class="ss">signal</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">To</span><span class="p" data-group-id="1099294387-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9233703090-3">{</span><span class="ss">signal</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">To</span><span class="p" data-group-id="9233703090-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="p">_</span><span class="n">Else</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">false</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><h2 id="maybe" class="section-heading">
│ │ │    <a href="#maybe" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -412,57 +412,57 @@
│ │ │  the top-level of a <code class="inline">maybe</code> block. It matches the pattern <code class="inline">Expr1</code> against
│ │ │  <code class="inline">Expr2</code>. If the matching succeeds, any unbound variable in the pattern becomes
│ │ │  bound. If the expression is the last expression in the <code class="inline">maybe</code> block, it also
│ │ │  returns the value of <code class="inline">Expr2</code>. If the matching is unsuccessful, the rest of the
│ │ │  expressions in the <code class="inline">maybe</code> block are skipped and the return value of the <code class="inline">maybe</code>
│ │ │  block is <code class="inline">Expr2</code>.</p><p>None of the variables bound in a <code class="inline">maybe</code> block must be used in the code that
│ │ │  follows the block.</p><p>Here is an example:</p><pre><code class="makeup erlang" translate="no"><span class="k">maybe</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5257511489-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="5257511489-1">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="5257511489-2">(</span><span class="p" data-group-id="5257511489-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4519889875-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="4519889875-1">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="4519889875-2">(</span><span class="p" data-group-id="4519889875-2">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5257511489-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="5257511489-3">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="5257511489-4">(</span><span class="p" data-group-id="5257511489-4">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4519889875-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="4519889875-3">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="4519889875-4">(</span><span class="p" data-group-id="4519889875-4">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>Let us first assume that <code class="inline">a()</code> returns <code class="inline">{ok,42}</code> and <code class="inline">b()</code> returns <code class="inline">{ok,58}</code>.
│ │ │  With those return values, all of the match operators will succeed, and the
│ │ │  return value of the <code class="inline">maybe</code> block is <code class="inline">A + B</code>, which is equal to <code class="inline">42 + 58 = 100</code>.</p><p>Now let us assume that <code class="inline">a()</code> returns <code class="inline">error</code>. The conditional match operator in
│ │ │  <code class="inline">{ok, A} ?= a()</code> fails to match, and the return value of the <code class="inline">maybe</code> block is
│ │ │  the value of the expression that failed to match, namely <code class="inline">error</code>. Similarly, if
│ │ │  <code class="inline">b()</code> returns <code class="inline">wrong</code>, the return value of the <code class="inline">maybe</code> block is <code class="inline">wrong</code>.</p><p>Finally, let us assume that <code class="inline">a()</code> returns <code class="inline">{ok,-1}</code>. Because <code class="inline">true = A &gt;= 0</code> uses
│ │ │  the match operator <code class="inline">=</code>, a <code class="inline">{badmatch,false}</code> run-time error occurs when the
│ │ │ -expression fails to match the pattern.</p><p>The example can be written in a less succinct way using nested case expressions:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="3820436579-1">(</span><span class="p" data-group-id="3820436579-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3820436579-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="3820436579-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +expression fails to match the pattern.</p><p>The example can be written in a less succinct way using nested case expressions:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="2420973687-1">(</span><span class="p" data-group-id="2420973687-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2420973687-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="2420973687-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="k">case</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="3820436579-3">(</span><span class="p" data-group-id="3820436579-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="3820436579-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="3820436579-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="k">case</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="2420973687-3">(</span><span class="p" data-group-id="2420973687-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="2420973687-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="2420973687-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                  </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="n">Other1</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                  </span><span class="n">Other1</span><span class="w">
│ │ │          </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Other2</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">Other2</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>The <code class="inline">maybe</code> block can be augmented with <code class="inline">else</code> clauses:</p><pre><code class="makeup erlang" translate="no"><span class="k">maybe</span><span class="w">
│ │ │      </span><span class="n">Expr1</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="n">ExprN</span><span class="w">
│ │ │  </span><span class="k">else</span><span class="w">
│ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="2751777027-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="2751777027-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="1363860774-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="1363860774-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="2751777027-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="2751777027-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="1363860774-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="1363860774-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>If a conditional match operator fails, the failed expression is matched against
│ │ │  the patterns in all clauses between the <code class="inline">else</code> and <code class="inline">end</code> keywords. If a match
│ │ │  succeeds and the optional guard sequence <code class="inline">GuardSeq</code> is true, the corresponding
│ │ │  <code class="inline">Body</code> is evaluated. The value returned from the body is the return value of the
│ │ │  <code class="inline">maybe</code> block.</p><p>If there is no matching pattern with a true guard sequence, an <code class="inline">else_clause</code>
│ │ │  run-time error occurs.</p><p>None of the variables bound in a <code class="inline">maybe</code> block must be used in the <code class="inline">else</code>
│ │ │  clauses. None of the variables bound in the <code class="inline">else</code> clauses must be used in the
│ │ │  code that follows the <code class="inline">maybe</code> block.</p><p>Here is the previous example augmented with <code class="inline">else</code> clauses:</p><pre><code class="makeup erlang" translate="no"><span class="k">maybe</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5327988585-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="5327988585-1">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="5327988585-2">(</span><span class="p" data-group-id="5327988585-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5484653803-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="5484653803-1">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="5484653803-2">(</span><span class="p" data-group-id="5484653803-2">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5327988585-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="5327988585-3">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="5327988585-4">(</span><span class="p" data-group-id="5327988585-4">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5484653803-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="5484653803-3">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="5484653803-4">(</span><span class="p" data-group-id="5484653803-4">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="w">
│ │ │  </span><span class="k">else</span><span class="w">
│ │ │      </span><span class="ss">error</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">error</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">wrong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">error</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>The <code class="inline">else</code> clauses translate the failing value from the conditional match
│ │ │  operators to the value <code class="inline">error</code>. If the failing value is not one of the
│ │ │  recognized values, an <code class="inline">else_clause</code> run-time error occurs.</p><h2 id="send" class="section-heading">
│ │ │ @@ -481,18 +481,18 @@
│ │ │  <code class="inline">{Name,Node}</code> (or a pid located at another node), also never fails.</li></ul><h2 id="receive" class="section-heading">
│ │ │    <a href="#receive" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Receive</span>
│ │ │  </h2>
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="4861067476-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="4861067476-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="4565935167-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="4565935167-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="4861067476-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="4861067476-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="4565935167-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="4565935167-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>The <code class="inline">receive</code> expression searches for a message in the message queue that matches
│ │ │  one of the patterns in the clauses of the <code class="inline">receive</code> expression. The patterns in
│ │ │  the clauses are matched against a message from top to bottom. The first message
│ │ │  from the start of the message queue that matches will be selected. Messages are
│ │ │  normally
│ │ │  <a href="ref_man_processes.html#message-queue-order">enqueued in the message queue</a> in
│ │ │ @@ -509,27 +509,27 @@
│ │ │  specific messages and the message queue is huge, executing such a <code class="inline">receive</code>
│ │ │  expression might become very expensive.</p><p>One type of <code class="inline">receive</code> expressions matching on only specific patterns can,
│ │ │  however, be optimized by the compiler and runtime system, namely when
│ │ │  you create a <a href="../../doc/system/data_types.html#reference"><em>reference</em></a> and
│ │ │  match on it in all clauses of a <code class="inline">receive</code> expression <em>close</em> to where the
│ │ │  reference was created. In this case, only the messages received after
│ │ │  the reference was created need to be inspected. For more information see the
│ │ │ -<a href="../../doc/system/eff_guide_processes.html#fetching-received-messages"><em>Fetching Received Messages</em> section of the <em>Efficiency Guide</em></a>.</p></section><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">wait_for_onhook</span><span class="p" data-group-id="5588387531-1">(</span><span class="p" data-group-id="5588387531-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +<a href="../../doc/system/eff_guide_processes.html#fetching-received-messages"><em>Fetching Received Messages</em> section of the <em>Efficiency Guide</em></a>.</p></section><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">wait_for_onhook</span><span class="p" data-group-id="1541259906-1">(</span><span class="p" data-group-id="1541259906-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">onhook</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">disconnect</span><span class="p" data-group-id="5588387531-2">(</span><span class="p" data-group-id="5588387531-2">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">idle</span><span class="p" data-group-id="5588387531-3">(</span><span class="p" data-group-id="5588387531-3">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5588387531-4">{</span><span class="ss">connect</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="5588387531-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">B</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5588387531-5">{</span><span class="ss">busy</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5588387531-6">(</span><span class="p" data-group-id="5588387531-6">)</span><span class="p" data-group-id="5588387531-5">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">wait_for_onhook</span><span class="p" data-group-id="5588387531-7">(</span><span class="p" data-group-id="5588387531-7">)</span><span class="w">
│ │ │ +            </span><span class="nf">disconnect</span><span class="p" data-group-id="1541259906-2">(</span><span class="p" data-group-id="1541259906-2">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">idle</span><span class="p" data-group-id="1541259906-3">(</span><span class="p" data-group-id="1541259906-3">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="1541259906-4">{</span><span class="ss">connect</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="1541259906-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">B</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1541259906-5">{</span><span class="ss">busy</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1541259906-6">(</span><span class="p" data-group-id="1541259906-6">)</span><span class="p" data-group-id="1541259906-5">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">wait_for_onhook</span><span class="p" data-group-id="1541259906-7">(</span><span class="p" data-group-id="1541259906-7">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">receive</code> expression can be augmented with a timeout:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="9610412928-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="9610412928-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="5234925250-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="5234925250-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="9610412928-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="9610412928-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="5234925250-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="5234925250-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │  </span><span class="k">after</span><span class="w">
│ │ │      </span><span class="n">ExprT</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyT</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p><code class="inline">receive...after</code> works exactly as <code class="inline">receive</code>, except that if no matching message
│ │ │  has arrived within <code class="inline">ExprT</code> milliseconds, then <code class="inline">BodyT</code> is evaluated instead. The
│ │ │  return value of <code class="inline">BodyT</code> then becomes the return value of the <code class="inline">receive...after</code>
│ │ │ @@ -540,35 +540,35 @@
│ │ │  another short timeout) might be cheap since the timeout is short. This is
│ │ │  <em>not</em> necessarily the case. If the patterns in the clauses of the <code class="inline">receive</code>
│ │ │  expression only match specific messages and no such messages exist in the
│ │ │  message queue, the whole message queue needs to be inspected before the
│ │ │  timeout can occur. That is, the same caveat as in
│ │ │  <a href="#selective-receive-warning">the warning above</a> applies.</p></section><p>The atom <code class="inline">infinity</code> will make the process wait indefinitely for a matching
│ │ │  message. This is the same as not using a timeout. It can be useful for timeout
│ │ │ -values that are calculated at runtime.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">wait_for_onhook</span><span class="p" data-group-id="0304225125-1">(</span><span class="p" data-group-id="0304225125-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +values that are calculated at runtime.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">wait_for_onhook</span><span class="p" data-group-id="3492139581-1">(</span><span class="p" data-group-id="3492139581-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">onhook</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">disconnect</span><span class="p" data-group-id="0304225125-2">(</span><span class="p" data-group-id="0304225125-2">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">idle</span><span class="p" data-group-id="0304225125-3">(</span><span class="p" data-group-id="0304225125-3">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0304225125-4">{</span><span class="ss">connect</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0304225125-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">B</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0304225125-5">{</span><span class="ss">busy</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0304225125-6">(</span><span class="p" data-group-id="0304225125-6">)</span><span class="p" data-group-id="0304225125-5">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">wait_for_onhook</span><span class="p" data-group-id="0304225125-7">(</span><span class="p" data-group-id="0304225125-7">)</span><span class="w">
│ │ │ +            </span><span class="nf">disconnect</span><span class="p" data-group-id="3492139581-2">(</span><span class="p" data-group-id="3492139581-2">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">idle</span><span class="p" data-group-id="3492139581-3">(</span><span class="p" data-group-id="3492139581-3">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3492139581-4">{</span><span class="ss">connect</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="3492139581-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">B</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3492139581-5">{</span><span class="ss">busy</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3492139581-6">(</span><span class="p" data-group-id="3492139581-6">)</span><span class="p" data-group-id="3492139581-5">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">wait_for_onhook</span><span class="p" data-group-id="3492139581-7">(</span><span class="p" data-group-id="3492139581-7">)</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w">
│ │ │          </span><span class="mi">60000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">disconnect</span><span class="p" data-group-id="0304225125-8">(</span><span class="p" data-group-id="0304225125-8">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">error</span><span class="p" data-group-id="0304225125-9">(</span><span class="p" data-group-id="0304225125-9">)</span><span class="w">
│ │ │ +            </span><span class="nf">disconnect</span><span class="p" data-group-id="3492139581-8">(</span><span class="p" data-group-id="3492139581-8">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">error</span><span class="p" data-group-id="3492139581-9">(</span><span class="p" data-group-id="3492139581-9">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>It is legal to use a <code class="inline">receive...after</code> expression with no branches:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │  </span><span class="k">after</span><span class="w">
│ │ │      </span><span class="n">ExprT</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyT</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>This construction does not consume any messages, only suspends execution in the
│ │ │ -process for <code class="inline">ExprT</code> milliseconds. This can be used to implement simple timers.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">timer</span><span class="p" data-group-id="3417389559-1">(</span><span class="p" data-group-id="3417389559-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="3417389559-2">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">timer</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3417389559-3">[</span><span class="nf">self</span><span class="p" data-group-id="3417389559-4">(</span><span class="p" data-group-id="3417389559-4">)</span><span class="p" data-group-id="3417389559-3">]</span><span class="p" data-group-id="3417389559-2">)</span><span class="p">.</span><span class="w">
│ │ │ +process for <code class="inline">ExprT</code> milliseconds. This can be used to implement simple timers.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">timer</span><span class="p" data-group-id="7239790968-1">(</span><span class="p" data-group-id="7239790968-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="7239790968-2">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">timer</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7239790968-3">[</span><span class="nf">self</span><span class="p" data-group-id="7239790968-4">(</span><span class="p" data-group-id="7239790968-4">)</span><span class="p" data-group-id="7239790968-3">]</span><span class="p" data-group-id="7239790968-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">timer</span><span class="p" data-group-id="3417389559-5">(</span><span class="n">Pid</span><span class="p" data-group-id="3417389559-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">timer</span><span class="p" data-group-id="7239790968-5">(</span><span class="n">Pid</span><span class="p" data-group-id="7239790968-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w">
│ │ │          </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">timeout</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>For more information on timers in Erlang in general, see the
│ │ │  <a href="../../erts-17.0/doc/html/time_correction.html#timers"><em>Timers</em></a> section of the
│ │ │  <a href="../../erts-17.0/doc/html/time_correction.html"><em>Time and Time Correction in Erlang</em></a>
│ │ │ @@ -610,21 +610,21 @@
│ │ │  </span><span class="ss">false</span><span class="w">
│ │ │  </span><span class="gp unselectable">4&gt; </span><span class="mf">0.0</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="o">-</span><span class="mf">0.0</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span><span class="w">
│ │ │  </span><span class="gp unselectable">5&gt; </span><span class="mf">0.0</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="o">+</span><span class="mf">0.0</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │  </span><span class="gp unselectable">6&gt; </span><span class="mi">1</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span><span class="w">
│ │ │ -</span><span class="gp unselectable">7&gt; </span><span class="p" data-group-id="1582803926-1">#{</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="1582803926-1">}</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="1582803926-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1582803926-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">7&gt; </span><span class="p" data-group-id="1753602601-1">#{</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="1753602601-1">}</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="1753602601-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1753602601-2">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span><span class="w">
│ │ │ -</span><span class="gp unselectable">8&gt; </span><span class="p" data-group-id="1582803926-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1582803926-3">}</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="p" data-group-id="1582803926-4">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">2.0</span><span class="p" data-group-id="1582803926-4">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">8&gt; </span><span class="p" data-group-id="1753602601-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1753602601-3">}</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="p" data-group-id="1753602601-4">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">2.0</span><span class="p" data-group-id="1753602601-4">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="gp unselectable">9&gt; </span><span class="p" data-group-id="1582803926-5">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">2</span><span class="p" data-group-id="1582803926-5">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p" data-group-id="1582803926-6">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="1582803926-6">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">9&gt; </span><span class="p" data-group-id="1753602601-5">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">2</span><span class="p" data-group-id="1753602601-5">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p" data-group-id="1753602601-6">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="1753602601-6">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="gp unselectable">10&gt; </span><span class="p" data-group-id="1582803926-7">&lt;&lt;</span><span class="mi">3</span><span class="p">:</span><span class="mi">2</span><span class="p" data-group-id="1582803926-7">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p" data-group-id="1582803926-8">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="1582803926-8">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">10&gt; </span><span class="p" data-group-id="1753602601-7">&lt;&lt;</span><span class="mi">3</span><span class="p">:</span><span class="mi">2</span><span class="p" data-group-id="1753602601-7">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p" data-group-id="1753602601-8">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="1753602601-8">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Prior to OTP 27, the term equivalence operators considered <code class="inline">0.0</code>
│ │ │  and <code class="inline">-0.0</code> to be the same term.</p><p>This was changed in OTP 27 but legacy code may have expected them to be
│ │ │  considered the same. To help users catch errors that may arise from an
│ │ │  upgrade, the compiler raises a warning when <code class="inline">0.0</code> is pattern-matched or used
│ │ │  in a term equivalence test.</p><p>If you need to match <code class="inline">0.0</code> specifically, the warning can be silenced by
│ │ │  writing <code class="inline">+0.0</code> instead, which produces the same term but makes the compiler
│ │ │  interpret the match as being done on purpose.</p></section><h2 id="arithmetic-expressions" class="section-heading">
│ │ │ @@ -650,15 +650,15 @@
│ │ │  </span><span class="mi">0</span><span class="w">
│ │ │  </span><span class="gp unselectable">8&gt; </span><span class="mi">2#10</span><span class="w"> </span><span class="ow">bor</span><span class="w"> </span><span class="mi">2#01</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="w">
│ │ │  </span><span class="gp unselectable">9&gt; </span><span class="ss">a</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">10</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: an error occurred when evaluating an arithmetic expression
│ │ │       in operator  +/2
│ │ │          called as a + 10</span><span class="w">
│ │ │ -</span><span class="gp unselectable">10&gt; </span><span class="mi">1</span><span class="w"> </span><span class="nf">bsl</span><span class="w"> </span><span class="p" data-group-id="4398227788-1">(</span><span class="mi">1</span><span class="w"> </span><span class="ow">bsl</span><span class="w"> </span><span class="mi">64</span><span class="p" data-group-id="4398227788-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">10&gt; </span><span class="mi">1</span><span class="w"> </span><span class="nf">bsl</span><span class="w"> </span><span class="p" data-group-id="7928061108-1">(</span><span class="mi">1</span><span class="w"> </span><span class="ow">bsl</span><span class="w"> </span><span class="mi">64</span><span class="p" data-group-id="7928061108-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: a system limit has been reached
│ │ │       in operator  bsl/2
│ │ │          called as 1 bsl 18446744073709551616</span></code></pre><h2 id="boolean-expressions" class="section-heading">
│ │ │    <a href="#boolean-expressions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Boolean Expressions</span>
│ │ │ @@ -677,136 +677,136 @@
│ │ │    <a href="#short-circuit-expressions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Short-Circuit Expressions</span>
│ │ │  </h2>
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="n">Expr1</span><span class="w"> </span><span class="ow">orelse</span><span class="w"> </span><span class="n">Expr2</span><span class="w">
│ │ │  </span><span class="n">Expr1</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">Expr2</span></code></pre><p><code class="inline">Expr2</code> is evaluated only if necessary. That is, <code class="inline">Expr2</code> is evaluated only if:</p><ul><li><code class="inline">Expr1</code> evaluates to <code class="inline">false</code> in an <code class="inline">orelse</code> expression.</li></ul><p>or</p><ul><li><code class="inline">Expr1</code> evaluates to <code class="inline">true</code> in an <code class="inline">andalso</code> expression.</li></ul><p>Returns either the value of <code class="inline">Expr1</code> (that is, <code class="inline">true</code> or <code class="inline">false</code>) or the value of
│ │ │ -<code class="inline">Expr2</code> (if <code class="inline">Expr2</code> is evaluated).</p><p><em>Example 1:</em></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="o">-</span><span class="mf">1.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nc">math</span><span class="p">:</span><span class="nf">sqrt</span><span class="p" data-group-id="5037950862-1">(</span><span class="n">A</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="5037950862-1">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="k">of</span></code></pre><p>This works even if <code class="inline">A</code> is less than <code class="inline">-1.0</code>, since in that case, <a href="../../lib/stdlib-8.0/doc/html/math.html#sqrt/1"><code class="inline">math:sqrt/1</code></a> is
│ │ │ -never evaluated.</p><p><em>Example 2:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">OnlyOne</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">is_atom</span><span class="p" data-group-id="5617091806-1">(</span><span class="n">L</span><span class="p" data-group-id="5617091806-1">)</span><span class="w"> </span><span class="nf">orelse</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="5617091806-2">(</span><span class="nf">is_list</span><span class="p" data-group-id="5617091806-3">(</span><span class="n">L</span><span class="p" data-group-id="5617091806-3">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="5617091806-4">(</span><span class="n">L</span><span class="p" data-group-id="5617091806-4">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="5617091806-2">)</span><span class="p">,</span></code></pre><p><code class="inline">Expr2</code> is not required to evaluate to a Boolean value. Because of that,
│ │ │ -<code class="inline">andalso</code> and <code class="inline">orelse</code> are tail-recursive.</p><p><em>Example 3 (tail-recursive function):</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">all</span><span class="p" data-group-id="1260440716-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1260440716-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="1260440716-2">]</span><span class="p" data-group-id="1260440716-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Pred</span><span class="p" data-group-id="1260440716-3">(</span><span class="n">Hd</span><span class="p" data-group-id="1260440716-3">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">all</span><span class="p" data-group-id="1260440716-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="1260440716-4">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">all</span><span class="p" data-group-id="1260440716-5">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1260440716-6">[</span><span class="p" data-group-id="1260440716-6">]</span><span class="p" data-group-id="1260440716-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +<code class="inline">Expr2</code> (if <code class="inline">Expr2</code> is evaluated).</p><p><em>Example 1:</em></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="o">-</span><span class="mf">1.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nc">math</span><span class="p">:</span><span class="nf">sqrt</span><span class="p" data-group-id="1182170329-1">(</span><span class="n">A</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="1182170329-1">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="k">of</span></code></pre><p>This works even if <code class="inline">A</code> is less than <code class="inline">-1.0</code>, since in that case, <a href="../../lib/stdlib-8.0/doc/html/math.html#sqrt/1"><code class="inline">math:sqrt/1</code></a> is
│ │ │ +never evaluated.</p><p><em>Example 2:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">OnlyOne</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">is_atom</span><span class="p" data-group-id="1038073403-1">(</span><span class="n">L</span><span class="p" data-group-id="1038073403-1">)</span><span class="w"> </span><span class="nf">orelse</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="1038073403-2">(</span><span class="nf">is_list</span><span class="p" data-group-id="1038073403-3">(</span><span class="n">L</span><span class="p" data-group-id="1038073403-3">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="1038073403-4">(</span><span class="n">L</span><span class="p" data-group-id="1038073403-4">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="1038073403-2">)</span><span class="p">,</span></code></pre><p><code class="inline">Expr2</code> is not required to evaluate to a Boolean value. Because of that,
│ │ │ +<code class="inline">andalso</code> and <code class="inline">orelse</code> are tail-recursive.</p><p><em>Example 3 (tail-recursive function):</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">all</span><span class="p" data-group-id="6958027801-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6958027801-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="6958027801-2">]</span><span class="p" data-group-id="6958027801-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pred</span><span class="p" data-group-id="6958027801-3">(</span><span class="n">Hd</span><span class="p" data-group-id="6958027801-3">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">all</span><span class="p" data-group-id="6958027801-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="6958027801-4">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">all</span><span class="p" data-group-id="6958027801-5">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6958027801-6">[</span><span class="p" data-group-id="6958027801-6">]</span><span class="p" data-group-id="6958027801-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">true</span><span class="p">.</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP R13A, <code class="inline">Expr2</code> was required to evaluate to a Boolean value,
│ │ │  and as a consequence, <code class="inline">andalso</code> and <code class="inline">orelse</code> were <strong>not</strong> tail-recursive.</p></section><h2 id="list-operations" class="section-heading">
│ │ │    <a href="#list-operations" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">List Operations</span>
│ │ │  </h2>
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="n">Expr1</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Expr2</span><span class="w">
│ │ │  </span><span class="n">Expr1</span><span class="w"> </span><span class="o">--</span><span class="w"> </span><span class="n">Expr2</span></code></pre><p>The list concatenation operator <code class="inline">++</code> appends its second argument to its first
│ │ │  and returns the resulting list.</p><p>The list subtraction operator <code class="inline">--</code> produces a list that is a copy of the first
│ │ │  argument. The procedure is as follows: for each element in the second argument,
│ │ │ -the first occurrence of this element (if any) is removed.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="1605214981-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1605214981-1">]</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="1605214981-2">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="1605214981-2">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1605214981-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="1605214981-3">]</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="1605214981-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1605214981-4">]</span><span class="w"> </span><span class="o">--</span><span class="w"> </span><span class="p" data-group-id="1605214981-5">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1605214981-5">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1605214981-6">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1605214981-6">]</span></code></pre><h2 id="map-expressions" class="section-heading">
│ │ │ +the first occurrence of this element (if any) is removed.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9649047979-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9649047979-1">]</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="9649047979-2">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="9649047979-2">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9649047979-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="9649047979-3">]</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="9649047979-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9649047979-4">]</span><span class="w"> </span><span class="o">--</span><span class="w"> </span><span class="p" data-group-id="9649047979-5">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9649047979-5">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9649047979-6">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9649047979-6">]</span></code></pre><h2 id="map-expressions" class="section-heading">
│ │ │    <a href="#map-expressions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Map Expressions</span>
│ │ │  </h2>
│ │ │  <h3 id="creating-maps" class="section-heading">
│ │ │    <a href="#creating-maps" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Creating Maps</span>
│ │ │  </h3>
│ │ │  <p>Constructing a new map is done by letting an expression <code class="inline">K</code> be associated with
│ │ │ -another expression <code class="inline">V</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9764951722-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="9764951722-1">}</span></code></pre><p>New maps can include multiple associations at construction by listing every
│ │ │ -association:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1914487694-1">#{</span><span class="n">K1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Kn</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Vn</span><span class="p" data-group-id="1914487694-1">}</span></code></pre><p>An empty map is constructed by not associating any terms with each other:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5443441926-1">#{</span><span class="p" data-group-id="5443441926-1">}</span></code></pre><p>All keys and values in the map are terms. Any expression is first evaluated and
│ │ │ +another expression <code class="inline">V</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4378401677-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="4378401677-1">}</span></code></pre><p>New maps can include multiple associations at construction by listing every
│ │ │ +association:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5626036091-1">#{</span><span class="n">K1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Kn</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Vn</span><span class="p" data-group-id="5626036091-1">}</span></code></pre><p>An empty map is constructed by not associating any terms with each other:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2083018914-1">#{</span><span class="p" data-group-id="2083018914-1">}</span></code></pre><p>All keys and values in the map are terms. Any expression is first evaluated and
│ │ │  then the resulting terms are used as <em>key</em> and <em>value</em> respectively.</p><p>Keys and values are separated by the <code class="inline">=&gt;</code> arrow and associations are separated
│ │ │ -by a comma (<code class="inline">,</code>).</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">M0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2180072092-1">#{</span><span class="p" data-group-id="2180072092-1">}</span><span class="p">,</span><span class="w">                 </span><span class="c1">% empty map</span><span class="w">
│ │ │ -</span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2180072092-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2180072092-3">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="2180072092-3">&gt;&gt;</span><span class="p" data-group-id="2180072092-2">}</span><span class="p">,</span><span class="w"> </span><span class="c1">% single association with literals</span><span class="w">
│ │ │ -</span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2180072092-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="2180072092-4">}</span><span class="p">,</span><span class="w">   </span><span class="c1">% multiple associations with literals</span><span class="w">
│ │ │ -</span><span class="n">M3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2180072092-5">#{</span><span class="ss">k</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2180072092-6">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p" data-group-id="2180072092-6">}</span><span class="p" data-group-id="2180072092-5">}</span><span class="p">,</span><span class="w">       </span><span class="c1">% single association with variables</span><span class="w">
│ │ │ -</span><span class="n">M4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2180072092-7">#{</span><span class="p" data-group-id="2180072092-8">{</span><span class="s">&quot;w&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2180072092-8">}</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="2180072092-9">(</span><span class="p" data-group-id="2180072092-9">)</span><span class="p" data-group-id="2180072092-7">}</span><span class="p">.</span><span class="w">  </span><span class="c1">% compound key associated with an evaluated expression</span></code></pre><p>Here, <code class="inline">A</code> and <code class="inline">B</code> are any expressions and <code class="inline">M0</code> through <code class="inline">M4</code> are the resulting
│ │ │ -map terms.</p><p>If two matching keys are declared, the latter key takes precedence.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7373893944-1">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="7373893944-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7373893944-2">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p" data-group-id="7373893944-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="7373893944-3">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="7373893944-3">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7373893944-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="7373893944-4">}</span></code></pre><p>The order in which the expressions constructing the keys (and their associated
│ │ │ +by a comma (<code class="inline">,</code>).</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">M0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8926130527-1">#{</span><span class="p" data-group-id="8926130527-1">}</span><span class="p">,</span><span class="w">                 </span><span class="c1">% empty map</span><span class="w">
│ │ │ +</span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8926130527-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8926130527-3">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="8926130527-3">&gt;&gt;</span><span class="p" data-group-id="8926130527-2">}</span><span class="p">,</span><span class="w"> </span><span class="c1">% single association with literals</span><span class="w">
│ │ │ +</span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8926130527-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="8926130527-4">}</span><span class="p">,</span><span class="w">   </span><span class="c1">% multiple associations with literals</span><span class="w">
│ │ │ +</span><span class="n">M3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8926130527-5">#{</span><span class="ss">k</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8926130527-6">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p" data-group-id="8926130527-6">}</span><span class="p" data-group-id="8926130527-5">}</span><span class="p">,</span><span class="w">       </span><span class="c1">% single association with variables</span><span class="w">
│ │ │ +</span><span class="n">M4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8926130527-7">#{</span><span class="p" data-group-id="8926130527-8">{</span><span class="s">&quot;w&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="8926130527-8">}</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="8926130527-9">(</span><span class="p" data-group-id="8926130527-9">)</span><span class="p" data-group-id="8926130527-7">}</span><span class="p">.</span><span class="w">  </span><span class="c1">% compound key associated with an evaluated expression</span></code></pre><p>Here, <code class="inline">A</code> and <code class="inline">B</code> are any expressions and <code class="inline">M0</code> through <code class="inline">M4</code> are the resulting
│ │ │ +map terms.</p><p>If two matching keys are declared, the latter key takes precedence.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4449153646-1">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="4449153646-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4449153646-2">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p" data-group-id="4449153646-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="4449153646-3">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="4449153646-3">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4449153646-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="4449153646-4">}</span></code></pre><p>The order in which the expressions constructing the keys (and their associated
│ │ │  values) are evaluated is not defined. The syntactic order of the key-value pairs
│ │ │  in the construction is of no relevance, except in the recently mentioned case of
│ │ │  two matching keys.</p><h3 id="updating-maps" class="section-heading">
│ │ │    <a href="#updating-maps" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Updating Maps</span>
│ │ │  </h3>
│ │ │  <p>Updating a map has a syntax similar to constructing it.</p><p>An expression defining the map to be updated is put in front of the expression
│ │ │ -defining the keys to be updated and their respective values:</p><pre><code class="makeup erlang" translate="no"><span class="n">M</span><span class="p" data-group-id="3240003532-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="3240003532-1">}</span></code></pre><p>Here <code class="inline">M</code> is a term of type map, and <code class="inline">K</code> and <code class="inline">V</code> can be any expression.</p><p>If key <code class="inline">K</code> does not match any existing key in the map, a new association is
│ │ │ +defining the keys to be updated and their respective values:</p><pre><code class="makeup erlang" translate="no"><span class="n">M</span><span class="p" data-group-id="6992830675-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="6992830675-1">}</span></code></pre><p>Here <code class="inline">M</code> is a term of type map, and <code class="inline">K</code> and <code class="inline">V</code> can be any expression.</p><p>If key <code class="inline">K</code> does not match any existing key in the map, a new association is
│ │ │  created from key <code class="inline">K</code> to value <code class="inline">V</code>.</p><p>If key <code class="inline">K</code> matches an existing key in map <code class="inline">M</code>, its associated value is replaced
│ │ │  by the new value <code class="inline">V</code>. In both cases, the evaluated map expression returns a new
│ │ │ -map.</p><p>If <code class="inline">M</code> is not of type map, an exception of type <code class="inline">badmap</code> is raised.</p><p>To only update an existing value, the following syntax is used:</p><pre><code class="makeup erlang" translate="no"><span class="n">M</span><span class="p" data-group-id="9124129741-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="9124129741-1">}</span></code></pre><p>Here <code class="inline">M</code> is a term of type map, <code class="inline">V</code> is an expression, and <code class="inline">K</code> is an expression
│ │ │ +map.</p><p>If <code class="inline">M</code> is not of type map, an exception of type <code class="inline">badmap</code> is raised.</p><p>To only update an existing value, the following syntax is used:</p><pre><code class="makeup erlang" translate="no"><span class="n">M</span><span class="p" data-group-id="0187225298-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="0187225298-1">}</span></code></pre><p>Here <code class="inline">M</code> is a term of type map, <code class="inline">V</code> is an expression, and <code class="inline">K</code> is an expression
│ │ │  that evaluates to an existing key in <code class="inline">M</code>.</p><p>If key <code class="inline">K</code> does not match any existing keys in map <code class="inline">M</code>, an exception of type
│ │ │  <code class="inline">badkey</code> is raised at runtime. If a matching key <code class="inline">K</code> is present in map <code class="inline">M</code>,
│ │ │  its associated value is replaced by the new value <code class="inline">V</code>, and the evaluated map
│ │ │ -expression returns a new map.</p><p>If <code class="inline">M</code> is not of type map, an exception of type <code class="inline">badmap</code> is raised.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">M0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8609252977-1">#{</span><span class="p" data-group-id="8609252977-1">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M0</span><span class="p" data-group-id="8609252977-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="8609252977-2">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="8609252977-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="8609252977-3">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">M3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M2</span><span class="p" data-group-id="8609252977-4">#{</span><span class="s">&quot;function&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="8609252977-5">(</span><span class="p" data-group-id="8609252977-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="8609252977-6">(</span><span class="p" data-group-id="8609252977-6">)</span><span class="w"> </span><span class="k">end</span><span class="p" data-group-id="8609252977-4">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">M4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M3</span><span class="p" data-group-id="8609252977-7">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="8609252977-7">}</span><span class="p">.</span><span class="w">  </span><span class="c1">% &#39;a&#39; and &#39;b&#39; were added in `M1` and `M2`.</span></code></pre><p>Here <code class="inline">M0</code> is any map. It follows that <code class="inline">M1</code> through <code class="inline">M4</code> are maps as well.</p><p><em>More examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4565198886-1">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="4565198886-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4565198886-2">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="p" data-group-id="4565198886-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">M</span><span class="p" data-group-id="4565198886-3">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="4565198886-3">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4565198886-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="4565198886-4">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="n">M</span><span class="p" data-group-id="4565198886-5">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="4565198886-5">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4565198886-6">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="4565198886-6">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="n">M</span><span class="p" data-group-id="4565198886-7">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="4565198886-7">}</span><span class="p">.</span><span class="w">
│ │ │ +expression returns a new map.</p><p>If <code class="inline">M</code> is not of type map, an exception of type <code class="inline">badmap</code> is raised.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">M0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8588242137-1">#{</span><span class="p" data-group-id="8588242137-1">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M0</span><span class="p" data-group-id="8588242137-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="8588242137-2">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="8588242137-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="8588242137-3">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">M3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M2</span><span class="p" data-group-id="8588242137-4">#{</span><span class="s">&quot;function&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="8588242137-5">(</span><span class="p" data-group-id="8588242137-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="8588242137-6">(</span><span class="p" data-group-id="8588242137-6">)</span><span class="w"> </span><span class="k">end</span><span class="p" data-group-id="8588242137-4">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">M4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M3</span><span class="p" data-group-id="8588242137-7">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="8588242137-7">}</span><span class="p">.</span><span class="w">  </span><span class="c1">% &#39;a&#39; and &#39;b&#39; were added in `M1` and `M2`.</span></code></pre><p>Here <code class="inline">M0</code> is any map. It follows that <code class="inline">M1</code> through <code class="inline">M4</code> are maps as well.</p><p><em>More examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1545391048-1">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="1545391048-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1545391048-2">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="p" data-group-id="1545391048-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">M</span><span class="p" data-group-id="1545391048-3">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1545391048-3">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1545391048-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1545391048-4">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="n">M</span><span class="p" data-group-id="1545391048-5">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1545391048-5">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1545391048-6">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1545391048-6">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="n">M</span><span class="p" data-group-id="1545391048-7">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1545391048-7">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: bad argument</span></code></pre><p>As in construction, the order in which the key and value expressions are
│ │ │  evaluated is not defined. The syntactic order of the key-value pairs in the
│ │ │  update is of no relevance, except in the case where two keys match. In that
│ │ │  case, the latter value is used.</p><h3 id="maps-in-patterns" class="section-heading">
│ │ │    <a href="#maps-in-patterns" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Maps in Patterns</span>
│ │ │  </h3>
│ │ │ -<p>Matching of key-value associations from maps is done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9610604847-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="9610604847-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>Here <code class="inline">M</code> is any map. The key <code class="inline">K</code> must be a
│ │ │ +<p>Matching of key-value associations from maps is done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9789223983-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="9789223983-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>Here <code class="inline">M</code> is any map. The key <code class="inline">K</code> must be a
│ │ │  <a href="expressions.html#guard-expressions">guard expression</a>, with all variables already
│ │ │  bound. <code class="inline">V</code> can be any pattern with either bound or unbound variables.</p><p>If the variable <code class="inline">V</code> is unbound, it becomes bound to the value associated with
│ │ │  the key <code class="inline">K</code>, which must exist in the map <code class="inline">M</code>. If the variable <code class="inline">V</code> is bound, it
│ │ │  must match the value associated with <code class="inline">K</code> in <code class="inline">M</code>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 23, the expression defining the key <code class="inline">K</code> was restricted to be
│ │ │ -either a single variable or a literal.</p></section><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7093008485-1">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7093008485-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7093008485-2">}</span><span class="p" data-group-id="7093008485-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7093008485-3">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7093008485-4">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7093008485-4">}</span><span class="p" data-group-id="7093008485-3">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="7093008485-5">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="7093008485-6">{</span><span class="mi">1</span><span class="p">,</span><span class="n">B</span><span class="p" data-group-id="7093008485-6">}</span><span class="p" data-group-id="7093008485-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7093008485-7">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7093008485-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7093008485-8">}</span><span class="p" data-group-id="7093008485-7">}</span><span class="w">
│ │ │ +either a single variable or a literal.</p></section><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9651789471-1">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9651789471-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9651789471-2">}</span><span class="p" data-group-id="9651789471-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9651789471-3">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9651789471-4">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9651789471-4">}</span><span class="p" data-group-id="9651789471-3">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="9651789471-5">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="9651789471-6">{</span><span class="mi">1</span><span class="p">,</span><span class="n">B</span><span class="p" data-group-id="9651789471-6">}</span><span class="p" data-group-id="9651789471-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9651789471-7">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9651789471-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9651789471-8">}</span><span class="p" data-group-id="9651789471-7">}</span><span class="w">
│ │ │  </span><span class="gp unselectable">3&gt; </span><span class="n">B</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">2</span><span class="p">.</span></code></pre><p>This binds variable <code class="inline">B</code> to integer <code class="inline">2</code>.</p><p>Similarly, multiple values from the map can be matched:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7063822647-1">#{</span><span class="n">K1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Kn</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Vn</span><span class="p" data-group-id="7063822647-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>Here keys <code class="inline">K1</code> through <code class="inline">Kn</code> are any expressions with literals or bound
│ │ │ +</span><span class="mi">2</span><span class="p">.</span></code></pre><p>This binds variable <code class="inline">B</code> to integer <code class="inline">2</code>.</p><p>Similarly, multiple values from the map can be matched:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6548608452-1">#{</span><span class="n">K1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Kn</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Vn</span><span class="p" data-group-id="6548608452-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>Here keys <code class="inline">K1</code> through <code class="inline">Kn</code> are any expressions with literals or bound
│ │ │  variables. If all key expressions evaluate successfully and all keys
│ │ │  exist in map <code class="inline">M</code>, all variables in <code class="inline">V1 .. Vn</code> are matched to the
│ │ │  associated values of their respective keys.</p><p>If the matching conditions are not met, the match fails.</p><p>Note that when matching a map, only the <code class="inline">:=</code> operator (not the <code class="inline">=&gt;</code>) is allowed
│ │ │  as a delimiter for the associations.</p><p>The order in which keys are declared in matching has no relevance.</p><p>Duplicate keys are allowed in matching and match each pattern associated with the
│ │ │ -keys:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5917366668-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V2</span><span class="p" data-group-id="5917366668-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>The empty map literal (<code class="inline">#{}</code>) matches any map when used as a pattern:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0951029501-1">#{</span><span class="p" data-group-id="0951029501-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expr</span></code></pre><p>This expression matches if the expression <code class="inline">Expr</code> is of type map; otherwise, it
│ │ │ -fails with an exception <code class="inline">badmatch</code>.</p><p>Here the key to be retrieved is constructed from an expression:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9747216374-1">#{</span><span class="p" data-group-id="9747216374-2">{</span><span class="ss">tag</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="9747216374-3">(</span><span class="n">List</span><span class="p" data-group-id="9747216374-3">)</span><span class="p" data-group-id="9747216374-2">}</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="9747216374-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map</span></code></pre><p><code class="inline">List</code> must be an already bound variable.</p><h4>Matching Syntax</h4><p>Matching of literals as keys is allowed in function heads:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% only start if not_started</span><span class="w">
│ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="9068484708-1">(</span><span class="ss">start</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9068484708-2">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">not_started</span><span class="p" data-group-id="9068484708-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="9068484708-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +keys:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8222083589-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V2</span><span class="p" data-group-id="8222083589-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>The empty map literal (<code class="inline">#{}</code>) matches any map when used as a pattern:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3389032406-1">#{</span><span class="p" data-group-id="3389032406-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expr</span></code></pre><p>This expression matches if the expression <code class="inline">Expr</code> is of type map; otherwise, it
│ │ │ +fails with an exception <code class="inline">badmatch</code>.</p><p>Here the key to be retrieved is constructed from an expression:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4829001768-1">#{</span><span class="p" data-group-id="4829001768-2">{</span><span class="ss">tag</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="4829001768-3">(</span><span class="n">List</span><span class="p" data-group-id="4829001768-3">)</span><span class="p" data-group-id="4829001768-2">}</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="4829001768-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map</span></code></pre><p><code class="inline">List</code> must be an already bound variable.</p><h4>Matching Syntax</h4><p>Matching of literals as keys is allowed in function heads:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% only start if not_started</span><span class="w">
│ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="3593252605-1">(</span><span class="ss">start</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3593252605-2">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">not_started</span><span class="p" data-group-id="3593252605-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="3593252605-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9068484708-3">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="9068484708-4">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">start</span><span class="p" data-group-id="9068484708-4">}</span><span class="p" data-group-id="9068484708-3">}</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3593252605-3">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="3593252605-4">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">start</span><span class="p" data-group-id="3593252605-4">}</span><span class="p" data-group-id="3593252605-3">}</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% only change if started</span><span class="w">
│ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="9068484708-5">(</span><span class="ss">change</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9068484708-6">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">start</span><span class="p" data-group-id="9068484708-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="9068484708-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="3593252605-5">(</span><span class="ss">change</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3593252605-6">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">start</span><span class="p" data-group-id="3593252605-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="3593252605-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9068484708-7">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="9068484708-8">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">changed</span><span class="p" data-group-id="9068484708-8">}</span><span class="p" data-group-id="9068484708-7">}</span><span class="p">;</span></code></pre><h3 id="maps-in-guards" class="section-heading">
│ │ │ +    </span><span class="p" data-group-id="3593252605-7">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="3593252605-8">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">changed</span><span class="p" data-group-id="3593252605-8">}</span><span class="p" data-group-id="3593252605-7">}</span><span class="p">;</span></code></pre><h3 id="maps-in-guards" class="section-heading">
│ │ │    <a href="#maps-in-guards" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Maps in Guards</span>
│ │ │  </h3>
│ │ │  <p>Maps are allowed in guards as long as all subexpressions are valid guard
│ │ │  expressions.</p><p>The following guard BIFs handle maps:</p><ul><li><a href="../../erts-17.0/doc/html/erlang.html#is_map/1">is_map/1</a> in the <code class="inline">erlang</code> module</li><li><a href="../../erts-17.0/doc/html/erlang.html#is_map_key/2">is_map_key/2</a> in the <code class="inline">erlang</code> module</li><li><a href="../../erts-17.0/doc/html/erlang.html#map_get/2">map_get/2</a> in the <code class="inline">erlang</code> module</li><li><a href="../../erts-17.0/doc/html/erlang.html#map_size/1">map_size/1</a> in the <code class="inline">erlang</code> module</li></ul><h2 id="bit-syntax-expressions" class="section-heading">
│ │ │    <a href="#bit-syntax-expressions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Bit Syntax Expressions</span>
│ │ │  </h2>
│ │ │  <p>The bit syntax operates on <em>bit strings</em>. A bit string is a sequence of bits
│ │ │ -ordered from the most significant bit to the least significant bit.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6878049955-1">&lt;&lt;</span><span class="p" data-group-id="6878049955-1">&gt;&gt;</span><span class="w">  </span><span class="c1">% The empty bit string, zero length</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6878049955-2">&lt;&lt;</span><span class="n">E1</span><span class="p" data-group-id="6878049955-2">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6878049955-3">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">En</span><span class="p" data-group-id="6878049955-3">&gt;&gt;</span></code></pre><p>Each element <code class="inline">Ei</code> specifies a <em>segment</em> of the bit string. The segments are
│ │ │ +ordered from the most significant bit to the least significant bit.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2683398020-1">&lt;&lt;</span><span class="p" data-group-id="2683398020-1">&gt;&gt;</span><span class="w">  </span><span class="c1">% The empty bit string, zero length</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2683398020-2">&lt;&lt;</span><span class="n">E1</span><span class="p" data-group-id="2683398020-2">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2683398020-3">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">En</span><span class="p" data-group-id="2683398020-3">&gt;&gt;</span></code></pre><p>Each element <code class="inline">Ei</code> specifies a <em>segment</em> of the bit string. The segments are
│ │ │  ordered left to right from the most significant bit to the least significant bit
│ │ │  of the bit string.</p><p>Each segment specification <code class="inline">Ei</code> is a value, whose default type is <code class="inline">integer</code>,
│ │ │  followed by an optional <em>size expression</em> and an optional <em>type specifier list</em>.</p><pre><code class="makeup erlang" translate="no"><span class="n">Ei</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Value</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │       </span><span class="n">Value</span><span class="p">:</span><span class="n">Size</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │       </span><span class="n">Value</span><span class="o">/</span><span class="n">TypeSpecifierList</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │       </span><span class="n">Value</span><span class="p">:</span><span class="n">Size</span><span class="o">/</span><span class="n">TypeSpecifierList</span></code></pre><p>When used in a bit string construction, <code class="inline">Value</code> is an expression that is to
│ │ │  evaluate to an integer, float, or bit string. If the expression is not a single
│ │ │ @@ -817,34 +817,34 @@
│ │ │  <a href="expressions.html#guard-expressions">guard expression</a> that evaluates to an
│ │ │  integer. All variables in the guard expression must be already bound.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 23, <code class="inline">Size</code> was restricted to be an integer or a variable
│ │ │  bound to an integer.</p></section><p>The value of <code class="inline">Size</code> specifies the size of the segment in units (see below). The
│ │ │  default value depends on the type (see below):</p><ul><li>For <code class="inline">integer</code> it is 8.</li><li>For <code class="inline">float</code> it is 64.</li><li>For <code class="inline">binary</code> and <code class="inline">bitstring</code> it is the whole binary or bit string.</li></ul><p>In matching, the default value for a binary or bit string segment is only valid
│ │ │  for the last element. All other bit string or binary elements in the matching
│ │ │  must have a size specification.</p><p><a href="" id="binaries"></a></p><p><strong>Binaries</strong></p><p>A bit string with a length that is a multiple of 8 bits is known as a <em>binary</em>,
│ │ │  which is the most common and useful type of bit string.</p><p>A binary has a canonical representation in memory. Here follows a sequence of
│ │ │ -bytes where each byte's value is its sequence number:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4865925226-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="mi">10</span><span class="p" data-group-id="4865925226-1">&gt;&gt;</span></code></pre><p>Bit strings are a later generalization of binaries, so many texts and much
│ │ │ -information about binaries apply just as well to bit strings.</p><p><strong>Example:</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3735092496-1">&lt;&lt;</span><span class="n">A</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3735092496-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3735092496-2">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="3735092496-2">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +bytes where each byte's value is its sequence number:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2035368689-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="mi">10</span><span class="p" data-group-id="2035368689-1">&gt;&gt;</span></code></pre><p>Bit strings are a later generalization of binaries, so many texts and much
│ │ │ +information about binaries apply just as well to bit strings.</p><p><strong>Example:</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5836361878-1">&lt;&lt;</span><span class="n">A</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5836361878-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5836361878-2">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="5836361878-2">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">* 1:3: a binary field without size is only allowed at the end of a binary pattern</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="3735092496-3">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">3</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3735092496-3">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3735092496-4">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="3735092496-4">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3735092496-5">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="3735092496-5">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="5836361878-3">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">3</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5836361878-3">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5836361878-4">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="5836361878-4">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5836361878-5">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="5836361878-5">&gt;&gt;</span><span class="w">
│ │ │  </span><span class="gp unselectable">3&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3735092496-6">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="3735092496-6">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5836361878-6">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="5836361878-6">&gt;&gt;</span><span class="w">
│ │ │  </span><span class="gp unselectable">4&gt; </span><span class="n">B</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3735092496-7">&lt;&lt;</span><span class="s">&quot;de&quot;</span><span class="p" data-group-id="3735092496-7">&gt;&gt;</span></code></pre><p>For the <code class="inline">utf8</code>, <code class="inline">utf16</code>, and <code class="inline">utf32</code> types, <code class="inline">Size</code> must not be given. The size
│ │ │ +</span><span class="p" data-group-id="5836361878-7">&lt;&lt;</span><span class="s">&quot;de&quot;</span><span class="p" data-group-id="5836361878-7">&gt;&gt;</span></code></pre><p>For the <code class="inline">utf8</code>, <code class="inline">utf16</code>, and <code class="inline">utf32</code> types, <code class="inline">Size</code> must not be given. The size
│ │ │  of the segment is implicitly determined by the type and value itself.</p><p><code class="inline">TypeSpecifierList</code> is a list of type specifiers, in any order, separated by
│ │ │  hyphens (-). Default values are used for any omitted type specifiers.</p><ul><li><p><strong><code class="inline">Type</code>= <code class="inline">integer</code> | <code class="inline">float</code> | <code class="inline">binary</code> | <code class="inline">bytes</code> | <code class="inline">bitstring</code> | <code class="inline">bits</code> |
│ │ │  <code class="inline">utf8</code> | <code class="inline">utf16</code> | <code class="inline">utf32</code></strong> - The default is <code class="inline">integer</code>. <code class="inline">bytes</code> is a
│ │ │  shorthand for <code class="inline">binary</code> and <code class="inline">bits</code> is a shorthand for <code class="inline">bitstring</code>. See below
│ │ │  for more information about the <code class="inline">utf</code> types.</p></li><li><p><strong><code class="inline">Signedness</code>= <code class="inline">signed</code> | <code class="inline">unsigned</code></strong> - Only matters for matching and when
│ │ │  the type is <code class="inline">integer</code>. The default is <code class="inline">unsigned</code>.</p></li><li><p><strong><code class="inline">Endianness</code>= <code class="inline">big</code> | <code class="inline">little</code> | <code class="inline">native</code></strong> - Specifies byte level (octet
│ │ │  level) endianness (byte order). Native-endian means that the endianness is
│ │ │  resolved at load time to be either big-endian or little-endian, depending on
│ │ │  what is native for the CPU that the Erlang machine is run on. Endianness only
│ │ │  matters when the <strong>Type</strong> is either <code class="inline">integer</code>, <code class="inline">utf16</code>, <code class="inline">utf32</code>, or <code class="inline">float</code>. The
│ │ │ -default is <code class="inline">big</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8208489021-1">&lt;&lt;</span><span class="mi">16#1234</span><span class="p">:</span><span class="mi">16</span><span class="o">/</span><span class="ss">little</span><span class="p" data-group-id="8208489021-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8208489021-2">&lt;&lt;</span><span class="mi">16#3412</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="8208489021-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8208489021-3">&lt;&lt;</span><span class="mi">16#34</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">16#12</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="8208489021-3">&gt;&gt;</span></code></pre></li><li><p><strong><code class="inline">Unit</code>= <code class="inline">unit:IntegerLiteral</code></strong> - The allowed range is 1 through 256.
│ │ │ +default is <code class="inline">big</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5922391272-1">&lt;&lt;</span><span class="mi">16#1234</span><span class="p">:</span><span class="mi">16</span><span class="o">/</span><span class="ss">little</span><span class="p" data-group-id="5922391272-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5922391272-2">&lt;&lt;</span><span class="mi">16#3412</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="5922391272-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5922391272-3">&lt;&lt;</span><span class="mi">16#34</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">16#12</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="5922391272-3">&gt;&gt;</span></code></pre></li><li><p><strong><code class="inline">Unit</code>= <code class="inline">unit:IntegerLiteral</code></strong> - The allowed range is 1 through 256.
│ │ │  Defaults to 1 for <code class="inline">integer</code>, <code class="inline">float</code>, and <code class="inline">bitstring</code>, and to 8 for <code class="inline">binary</code>.
│ │ │  For types <code class="inline">bitstring</code>, <code class="inline">bits</code>, and <code class="inline">bytes</code>, it is not allowed to specify a
│ │ │  unit value different from the default value. No unit specifier must be given
│ │ │  for the types <code class="inline">utf8</code>, <code class="inline">utf16</code>, and <code class="inline">utf32</code>.</p></li></ul><h3 id="integer-segments" class="section-heading">
│ │ │    <a href="#integer-segments" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -869,41 +869,41 @@
│ │ │    </a>
│ │ │    <span class="text">Binary segments</span>
│ │ │  </h3>
│ │ │  <p>In this section, the phrase &quot;binary segment&quot; refers to any one of the segment
│ │ │  types <code class="inline">binary</code>, <code class="inline">bitstring</code>, <code class="inline">bytes</code>, and <code class="inline">bits</code>.</p><p>See also the paragraphs about <a href="expressions.html#binaries">Binaries</a>.</p><p>When constructing binaries and no size is specified for a binary segment, the
│ │ │  entire binary value is interpolated into the binary being constructed. However,
│ │ │  the size in bits of the binary being interpolated must be evenly divisible by
│ │ │ -the unit value for the segment; otherwise an exception is raised.</p><p>For example, the following examples all succeed:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7099009204-1">&lt;&lt;</span><span class="p" data-group-id="7099009204-2">(</span><span class="p" data-group-id="7099009204-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="7099009204-3">&gt;&gt;</span><span class="p" data-group-id="7099009204-2">)</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="7099009204-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7099009204-4">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="7099009204-4">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="7099009204-5">&lt;&lt;</span><span class="p" data-group-id="7099009204-6">(</span><span class="p" data-group-id="7099009204-7">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="7099009204-7">&gt;&gt;</span><span class="p" data-group-id="7099009204-6">)</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="7099009204-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7099009204-8">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="7099009204-8">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="7099009204-9">&lt;&lt;</span><span class="p" data-group-id="7099009204-10">(</span><span class="p" data-group-id="7099009204-11">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="7099009204-11">&gt;&gt;</span><span class="p" data-group-id="7099009204-10">)</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7099009204-9">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7099009204-12">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="7099009204-12">&gt;&gt;</span></code></pre><p>The first two examples have a unit value of 1 for the segment, while the third
│ │ │ +the unit value for the segment; otherwise an exception is raised.</p><p>For example, the following examples all succeed:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="1267313529-1">&lt;&lt;</span><span class="p" data-group-id="1267313529-2">(</span><span class="p" data-group-id="1267313529-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1267313529-3">&gt;&gt;</span><span class="p" data-group-id="1267313529-2">)</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="1267313529-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1267313529-4">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1267313529-4">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="1267313529-5">&lt;&lt;</span><span class="p" data-group-id="1267313529-6">(</span><span class="p" data-group-id="1267313529-7">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1267313529-7">&gt;&gt;</span><span class="p" data-group-id="1267313529-6">)</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1267313529-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1267313529-8">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1267313529-8">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="1267313529-9">&lt;&lt;</span><span class="p" data-group-id="1267313529-10">(</span><span class="p" data-group-id="1267313529-11">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1267313529-11">&gt;&gt;</span><span class="p" data-group-id="1267313529-10">)</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1267313529-9">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1267313529-12">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1267313529-12">&gt;&gt;</span></code></pre><p>The first two examples have a unit value of 1 for the segment, while the third
│ │ │  segment has a unit value of 8.</p><p>Attempting to interpolate a bit string of size 1 into a binary segment with unit
│ │ │ -8 (the default unit for <code class="inline">binary</code>) fails as shown in this example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="1713587475-1">&lt;&lt;</span><span class="p" data-group-id="1713587475-2">(</span><span class="p" data-group-id="1713587475-3">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1713587475-3">&gt;&gt;</span><span class="p" data-group-id="1713587475-2">)</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1713587475-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gt">** exception error: bad argument</span></code></pre><p>For the construction to succeed, the unit value of the segment must be 1:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="5712149509-1">&lt;&lt;</span><span class="p" data-group-id="5712149509-2">(</span><span class="p" data-group-id="5712149509-3">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="5712149509-3">&gt;&gt;</span><span class="p" data-group-id="5712149509-2">)</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="5712149509-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5712149509-4">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="5712149509-4">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="5712149509-5">&lt;&lt;</span><span class="p" data-group-id="5712149509-6">(</span><span class="p" data-group-id="5712149509-7">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="5712149509-7">&gt;&gt;</span><span class="p" data-group-id="5712149509-6">)</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="5712149509-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5712149509-8">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="5712149509-8">&gt;&gt;</span></code></pre><p>Similarly, when matching a binary segment with no size specified, the match
│ │ │ +8 (the default unit for <code class="inline">binary</code>) fails as shown in this example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8579642226-1">&lt;&lt;</span><span class="p" data-group-id="8579642226-2">(</span><span class="p" data-group-id="8579642226-3">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="8579642226-3">&gt;&gt;</span><span class="p" data-group-id="8579642226-2">)</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8579642226-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gt">** exception error: bad argument</span></code></pre><p>For the construction to succeed, the unit value of the segment must be 1:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="1388598672-1">&lt;&lt;</span><span class="p" data-group-id="1388598672-2">(</span><span class="p" data-group-id="1388598672-3">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1388598672-3">&gt;&gt;</span><span class="p" data-group-id="1388598672-2">)</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="1388598672-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1388598672-4">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1388598672-4">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="1388598672-5">&lt;&lt;</span><span class="p" data-group-id="1388598672-6">(</span><span class="p" data-group-id="1388598672-7">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1388598672-7">&gt;&gt;</span><span class="p" data-group-id="1388598672-6">)</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1388598672-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1388598672-8">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1388598672-8">&gt;&gt;</span></code></pre><p>Similarly, when matching a binary segment with no size specified, the match
│ │ │  succeeds if and only if the size in bits of the rest of the binary is evenly
│ │ │ -divisible by the unit value:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9525081674-1">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9525081674-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9525081674-2">&lt;&lt;</span><span class="s">&quot;&quot;</span><span class="p" data-group-id="9525081674-2">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9525081674-3">&lt;&lt;</span><span class="p" data-group-id="9525081674-3">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="9525081674-4">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9525081674-4">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9525081674-5">&lt;&lt;</span><span class="s">&quot;a&quot;</span><span class="p" data-group-id="9525081674-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +divisible by the unit value:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3768599514-1">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="3768599514-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3768599514-2">&lt;&lt;</span><span class="s">&quot;&quot;</span><span class="p" data-group-id="3768599514-2">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3768599514-3">&lt;&lt;</span><span class="p" data-group-id="3768599514-3">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="3768599514-4">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="3768599514-4">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3768599514-5">&lt;&lt;</span><span class="s">&quot;a&quot;</span><span class="p" data-group-id="3768599514-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no match of right hand side value &lt;&lt;&quot;a&quot;&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="9525081674-6">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9525081674-6">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9525081674-7">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="9525081674-7">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9525081674-8">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="9525081674-8">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="p" data-group-id="9525081674-9">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9525081674-9">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9525081674-10">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="9525081674-10">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="3768599514-6">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="3768599514-6">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3768599514-7">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="3768599514-7">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3768599514-8">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="3768599514-8">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="p" data-group-id="3768599514-9">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="3768599514-9">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3768599514-10">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="3768599514-10">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no match of right hand side value &lt;&lt;&quot;abc&quot;&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="9525081674-11">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9525081674-11">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9525081674-12">&lt;&lt;</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="9525081674-12">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9525081674-13">&lt;&lt;</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="9525081674-13">&gt;&gt;</span></code></pre><p>When a size is explicitly specified for a binary segment, the segment size in
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="3768599514-11">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="3768599514-11">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3768599514-12">&lt;&lt;</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="3768599514-12">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3768599514-13">&lt;&lt;</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="3768599514-13">&gt;&gt;</span></code></pre><p>When a size is explicitly specified for a binary segment, the segment size in
│ │ │  bits is the value of <code class="inline">Size</code> multiplied by the default or explicit unit value.</p><p>When constructing binaries, the size of the binary being interpolated into the
│ │ │ -constructed binary must be at least as large as the size of the binary segment.</p><p><strong>Examples:</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3028052754-1">&lt;&lt;</span><span class="p" data-group-id="3028052754-2">(</span><span class="p" data-group-id="3028052754-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="3028052754-3">&gt;&gt;</span><span class="p" data-group-id="3028052754-2">)</span><span class="p">:</span><span class="mi">2</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3028052754-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3028052754-4">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="3028052754-4">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="3028052754-5">&lt;&lt;</span><span class="p" data-group-id="3028052754-6">(</span><span class="p" data-group-id="3028052754-7">&lt;&lt;</span><span class="s">&quot;a&quot;</span><span class="p" data-group-id="3028052754-7">&gt;&gt;</span><span class="p" data-group-id="3028052754-6">)</span><span class="p">:</span><span class="mi">2</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3028052754-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +constructed binary must be at least as large as the size of the binary segment.</p><p><strong>Examples:</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4300486525-1">&lt;&lt;</span><span class="p" data-group-id="4300486525-2">(</span><span class="p" data-group-id="4300486525-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="4300486525-3">&gt;&gt;</span><span class="p" data-group-id="4300486525-2">)</span><span class="p">:</span><span class="mi">2</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4300486525-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4300486525-4">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="4300486525-4">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="4300486525-5">&lt;&lt;</span><span class="p" data-group-id="4300486525-6">(</span><span class="p" data-group-id="4300486525-7">&lt;&lt;</span><span class="s">&quot;a&quot;</span><span class="p" data-group-id="4300486525-7">&gt;&gt;</span><span class="p" data-group-id="4300486525-6">)</span><span class="p">:</span><span class="mi">2</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4300486525-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: construction of binary failed
│ │ │          *** segment 1 of type &#39;binary&#39;: the value &lt;&lt;&quot;a&quot;&gt;&gt; is shorter than the size of the segment</span></code></pre><h3 id="unicode-segments" class="section-heading">
│ │ │    <a href="#unicode-segments" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Unicode segments</span>
│ │ │  </h3>
│ │ │ @@ -919,78 +919,78 @@
│ │ │  range <code class="inline">0</code> through <code class="inline">16#D7FF</code> or <code class="inline">16#E000</code> through <code class="inline">16#10FFFF</code>. The match fails if the
│ │ │  returned value falls outside those ranges.</p><p>A segment of type <code class="inline">utf8</code> matches 1-4 bytes in the bit string, if the bit string
│ │ │  at the match position contains a valid UTF-8 sequence. (See RFC-3629 or the
│ │ │  Unicode standard.)</p><p>A segment of type <code class="inline">utf16</code> can match 2 or 4 bytes in the bit string. The match
│ │ │  fails if the bit string at the match position does not contain a legal UTF-16
│ │ │  encoding of a Unicode code point. (See RFC-2781 or the Unicode standard.)</p><p>A segment of type <code class="inline">utf32</code> can match 4 bytes in the bit string in the same way as
│ │ │  an <code class="inline">integer</code> segment matches 32 bits. The match fails if the resulting integer
│ │ │ -is outside the legal ranges previously mentioned.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9824874400-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="9824874400-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9824874400-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="9824874400-2">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9824874400-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="9824874400-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9824874400-4">&lt;&lt;</span><span class="mi">97</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="9824874400-4">&gt;&gt;</span><span class="w">
│ │ │ +is outside the legal ranges previously mentioned.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4082989515-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="4082989515-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4082989515-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="4082989515-2">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4082989515-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="4082989515-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4082989515-4">&lt;&lt;</span><span class="mi">97</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="4082989515-4">&gt;&gt;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9824874400-5">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9824874400-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9824874400-6">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="9824874400-6">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="p" data-group-id="9824874400-7">&lt;&lt;</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9824874400-7">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9824874400-8">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9824874400-8">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9824874400-9">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="9824874400-9">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4082989515-5">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="4082989515-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4082989515-6">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="4082989515-6">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="p" data-group-id="4082989515-7">&lt;&lt;</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="4082989515-7">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4082989515-8">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="4082989515-8">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4082989515-9">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="4082989515-9">&gt;&gt;</span><span class="w">
│ │ │  </span><span class="gp unselectable">5&gt; </span><span class="n">C</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">42</span><span class="w">
│ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="p" data-group-id="9824874400-10">&lt;&lt;</span><span class="n">D</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="n">E</span><span class="p">,</span><span class="n">F</span><span class="p" data-group-id="9824874400-10">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9824874400-11">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9824874400-11">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9824874400-12">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="9824874400-12">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="p" data-group-id="4082989515-10">&lt;&lt;</span><span class="n">D</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="n">E</span><span class="p">,</span><span class="n">F</span><span class="p" data-group-id="4082989515-10">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4082989515-11">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="4082989515-11">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4082989515-12">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="4082989515-12">&gt;&gt;</span><span class="w">
│ │ │  </span><span class="gp unselectable">7&gt; </span><span class="n">D</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">273</span><span class="w">
│ │ │  </span><span class="gp unselectable">8&gt; </span><span class="n">F</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">42</span><span class="w">
│ │ │ -</span><span class="gp unselectable">9&gt; </span><span class="p" data-group-id="9824874400-13">&lt;&lt;</span><span class="n">G</span><span class="p">,</span><span class="n">H</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="9824874400-13">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9824874400-14">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9824874400-14">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9824874400-15">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="9824874400-15">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">9&gt; </span><span class="p" data-group-id="4082989515-13">&lt;&lt;</span><span class="n">G</span><span class="p">,</span><span class="n">H</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4082989515-13">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4082989515-14">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="4082989515-14">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4082989515-15">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="4082989515-15">&gt;&gt;</span><span class="w">
│ │ │  </span><span class="gp unselectable">10&gt; </span><span class="n">H</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9824874400-16">&lt;&lt;</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="9824874400-16">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">11&gt; </span><span class="p" data-group-id="9824874400-17">&lt;&lt;</span><span class="n">G</span><span class="p">,</span><span class="n">J</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="9824874400-17">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9824874400-18">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">12</span><span class="p" data-group-id="9824874400-18">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9824874400-19">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">10</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="9824874400-19">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4082989515-16">&lt;&lt;</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="4082989515-16">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">11&gt; </span><span class="p" data-group-id="4082989515-17">&lt;&lt;</span><span class="n">G</span><span class="p">,</span><span class="n">J</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="4082989515-17">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4082989515-18">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">12</span><span class="p" data-group-id="4082989515-18">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4082989515-19">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">10</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="4082989515-19">&gt;&gt;</span><span class="w">
│ │ │  </span><span class="gp unselectable">12&gt; </span><span class="n">J</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9824874400-20">&lt;&lt;</span><span class="mi">17</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">10</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="9824874400-20">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4082989515-20">&lt;&lt;</span><span class="mi">17</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">10</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="4082989515-20">&gt;&gt;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="mi">13</span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="9824874400-21">&lt;&lt;</span><span class="mi">1024</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="9824874400-21">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9824874400-22">&lt;&lt;</span><span class="mi">208</span><span class="p">,</span><span class="mi">128</span><span class="p" data-group-id="9824874400-22">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="mi">13</span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="4082989515-21">&lt;&lt;</span><span class="mi">1024</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="4082989515-21">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4082989515-22">&lt;&lt;</span><span class="mi">208</span><span class="p">,</span><span class="mi">128</span><span class="p" data-group-id="4082989515-22">&gt;&gt;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="mi">14</span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="9824874400-23">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">:</span><span class="mi">7</span><span class="p" data-group-id="9824874400-23">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9824874400-24">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="9824874400-24">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">15&gt; </span><span class="p" data-group-id="9824874400-25">&lt;&lt;</span><span class="mi">16#123</span><span class="p">:</span><span class="mi">12</span><span class="o">/</span><span class="ss">little</span><span class="p" data-group-id="9824874400-25">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9824874400-26">&lt;&lt;</span><span class="mi">16#231</span><span class="p">:</span><span class="mi">12</span><span class="p" data-group-id="9824874400-26">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9824874400-27">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="9824874400-27">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9824874400-28">&lt;&lt;</span><span class="mi">35</span><span class="p">,</span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="9824874400-28">&gt;&gt;</span></code></pre><p>Notice that bit string patterns cannot be nested.</p><p>Notice also that &quot;<code class="inline">B=&lt;&lt;1&gt;&gt;</code>&quot; is interpreted as &quot;<code class="inline">B =&lt; &lt;1&gt;&gt;</code>&quot; which is a syntax
│ │ │ +</span><span class="mi">14</span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="4082989515-23">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">:</span><span class="mi">7</span><span class="p" data-group-id="4082989515-23">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4082989515-24">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="4082989515-24">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">15&gt; </span><span class="p" data-group-id="4082989515-25">&lt;&lt;</span><span class="mi">16#123</span><span class="p">:</span><span class="mi">12</span><span class="o">/</span><span class="ss">little</span><span class="p" data-group-id="4082989515-25">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4082989515-26">&lt;&lt;</span><span class="mi">16#231</span><span class="p">:</span><span class="mi">12</span><span class="p" data-group-id="4082989515-26">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4082989515-27">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="4082989515-27">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4082989515-28">&lt;&lt;</span><span class="mi">35</span><span class="p">,</span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="4082989515-28">&gt;&gt;</span></code></pre><p>Notice that bit string patterns cannot be nested.</p><p>Notice also that &quot;<code class="inline">B=&lt;&lt;1&gt;&gt;</code>&quot; is interpreted as &quot;<code class="inline">B =&lt; &lt;1&gt;&gt;</code>&quot; which is a syntax
│ │ │  error. The correct way is to write a space after <code class="inline">=</code>: <code class="inline">B = &lt;&lt;1&gt;&gt;</code>.</p><p>More examples are provided in <a href="../../doc/system/bit_syntax.html">Programming Examples</a>.</p><h2 id="fun-expressions" class="section-heading">
│ │ │    <a href="#fun-expressions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Fun Expressions</span>
│ │ │  </h2>
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">fun</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5815211593-1">[</span><span class="n">Name</span><span class="p" data-group-id="5815211593-1">]</span><span class="p" data-group-id="5815211593-2">(</span><span class="n">Pattern11</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">Pattern1N</span><span class="p" data-group-id="5815211593-2">)</span><span class="w"> </span><span class="p" data-group-id="5815211593-3">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="5815211593-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4305692782-1">[</span><span class="n">Name</span><span class="p" data-group-id="4305692782-1">]</span><span class="p" data-group-id="4305692782-2">(</span><span class="n">Pattern11</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">Pattern1N</span><span class="p" data-group-id="4305692782-2">)</span><span class="w"> </span><span class="p" data-group-id="4305692782-3">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="4305692782-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5815211593-4">[</span><span class="n">Name</span><span class="p" data-group-id="5815211593-4">]</span><span class="p" data-group-id="5815211593-5">(</span><span class="n">PatternK1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">PatternKN</span><span class="p" data-group-id="5815211593-5">)</span><span class="w"> </span><span class="p" data-group-id="5815211593-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqK</span><span class="p" data-group-id="5815211593-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4305692782-4">[</span><span class="n">Name</span><span class="p" data-group-id="4305692782-4">]</span><span class="p" data-group-id="4305692782-5">(</span><span class="n">PatternK1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">PatternKN</span><span class="p" data-group-id="4305692782-5">)</span><span class="w"> </span><span class="p" data-group-id="4305692782-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqK</span><span class="p" data-group-id="4305692782-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                </span><span class="n">BodyK</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>A fun expression begins with the keyword <code class="inline">fun</code> and ends with the keyword <code class="inline">end</code>.
│ │ │  Between them is to be a function declaration, similar to a
│ │ │  <a href="ref_man_functions.html#function-declaration-syntax">regular function declaration</a>,
│ │ │  except that the function name is optional and is to be a variable, if any.</p><p>Variables in a fun head shadow the function name and both shadow variables in
│ │ │  the function clause surrounding the fun expression. Variables bound in a fun
│ │ │ -body are local to the fun body.</p><p>The return value of the expression is the resulting fun.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="1187847219-1">(</span><span class="n">X</span><span class="p" data-group-id="1187847219-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +body are local to the fun body.</p><p>The return value of the expression is the resulting fun.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="1549217771-1">(</span><span class="n">X</span><span class="p" data-group-id="1549217771-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.39074546</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">Fun1</span><span class="p" data-group-id="1187847219-2">(</span><span class="mi">2</span><span class="p" data-group-id="1187847219-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">Fun1</span><span class="p" data-group-id="1549217771-2">(</span><span class="mi">2</span><span class="p" data-group-id="1549217771-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="n">Fun2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="1187847219-3">(</span><span class="n">X</span><span class="p" data-group-id="1187847219-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="o">&gt;=</span><span class="mi">5</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">gt</span><span class="p">;</span><span class="w"> </span><span class="p" data-group-id="1187847219-4">(</span><span class="n">X</span><span class="p" data-group-id="1187847219-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">lt</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="n">Fun2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="1549217771-3">(</span><span class="n">X</span><span class="p" data-group-id="1549217771-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="o">&gt;=</span><span class="mi">5</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">gt</span><span class="p">;</span><span class="w"> </span><span class="p" data-group-id="1549217771-4">(</span><span class="n">X</span><span class="p" data-group-id="1549217771-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">lt</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.39074546</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="n">Fun2</span><span class="p" data-group-id="1187847219-5">(</span><span class="mi">7</span><span class="p" data-group-id="1187847219-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="n">Fun2</span><span class="p" data-group-id="1549217771-5">(</span><span class="mi">7</span><span class="p" data-group-id="1549217771-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">gt</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="n">Fun3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="1187847219-6">(</span><span class="mi">1</span><span class="p" data-group-id="1187847219-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="1187847219-7">(</span><span class="n">X</span><span class="p" data-group-id="1187847219-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="1187847219-8">(</span><span class="n">X</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="1187847219-8">)</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="n">Fun3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="1549217771-6">(</span><span class="mi">1</span><span class="p" data-group-id="1549217771-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="1549217771-7">(</span><span class="n">X</span><span class="p" data-group-id="1549217771-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="1549217771-8">(</span><span class="n">X</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="1549217771-8">)</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.39074546</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="n">Fun3</span><span class="p" data-group-id="1187847219-9">(</span><span class="mi">4</span><span class="p" data-group-id="1187847219-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="n">Fun3</span><span class="p" data-group-id="1549217771-9">(</span><span class="mi">4</span><span class="p" data-group-id="1549217771-9">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">24</span></code></pre><p>The following fun expressions are also allowed:</p><pre><code class="makeup erlang" translate="no"><span class="k">fun</span><span class="w"> </span><span class="n">Name</span><span class="o">/</span><span class="n">Arity</span><span class="w">
│ │ │  </span><span class="k">fun</span><span class="w"> </span><span class="n">Module</span><span class="p">:</span><span class="n">Name</span><span class="o">/</span><span class="n">Arity</span></code></pre><p>In <code class="inline">Name/Arity</code>, <code class="inline">Name</code> is an atom and <code class="inline">Arity</code> is an integer. <code class="inline">Name/Arity</code> must
│ │ │ -specify an existing local function. The expression is syntactic sugar for:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="7346667763-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="7346667763-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="7346667763-2">(</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="7346667763-2">)</span><span class="w"> </span><span class="k">end</span></code></pre><p>In <code class="inline">Module:Name/Arity</code>, <code class="inline">Module</code> and <code class="inline">Name</code> are atoms and <code class="inline">Arity</code> is an
│ │ │ +specify an existing local function. The expression is syntactic sugar for:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="0040601339-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="0040601339-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="0040601339-2">(</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="0040601339-2">)</span><span class="w"> </span><span class="k">end</span></code></pre><p>In <code class="inline">Module:Name/Arity</code>, <code class="inline">Module</code> and <code class="inline">Name</code> are atoms and <code class="inline">Arity</code> is an
│ │ │  integer. <code class="inline">Module</code>, <code class="inline">Name</code>, and <code class="inline">Arity</code> can also be variables. A fun defined in
│ │ │  this way refers to the function <code class="inline">Name</code> with arity <code class="inline">Arity</code> in the <em>latest</em>
│ │ │  version of module <code class="inline">Module</code>. A fun defined in this way is not dependent on the
│ │ │  code for the module in which it is defined.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP R15, <code class="inline">Module</code>, <code class="inline">Name</code>, and <code class="inline">Arity</code> were not allowed to be
│ │ │  variables.</p></section><p>More examples are provided in <a href="../../doc/system/funs.html">Programming Examples</a>.</p><h2 id="catch-and-throw" class="section-heading">
│ │ │    <a href="#catch-and-throw" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -1000,35 +1000,35 @@
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">catch</span><span class="w"> </span><span class="n">Expr</span></code></pre><p>Returns the value of <code class="inline">Expr</code> unless an exception is raised during the evaluation. In
│ │ │  that case, the exception is caught. The return value depends on the class of the
│ │ │  exception:</p><ul><li><p><strong><code class="inline">error</code></strong> (a run-time error or the code called <a href="../../erts-17.0/doc/html/erlang.html#error/1"><code class="inline">error(Term)</code></a>) -
│ │ │  <code class="inline">{'EXIT',{Reason,Stack}}</code> is returned.</p></li><li><p><strong><code class="inline">exit</code></strong> (the code called <a href="../../erts-17.0/doc/html/erlang.html#exit/1"><code class="inline">exit(Term)</code></a>) - <code class="inline">{'EXIT',Term}</code> is returned.</p></li><li><p><strong><code class="inline">throw</code></strong> (the code called <a href="../../erts-17.0/doc/html/erlang.html#throw/1"><code class="inline">throw(Term)</code></a>) - <code class="inline">Term</code> is returned.</p></li></ul><p><code class="inline">Reason</code> depends on the type of error that occurred, and <code class="inline">Stack</code> is the stack of
│ │ │  recent function calls, see <a href="errors.html#exit_reasons">Exit Reasons</a>.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="k">catch</span><span class="w"> </span><span class="mi">1</span><span class="o">+</span><span class="mi">2</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="w">
│ │ │  </span><span class="gp unselectable">2&gt; </span><span class="k">catch</span><span class="w"> </span><span class="mi">1</span><span class="o">+</span><span class="ss">a</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7226872167-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="7226872167-2">{</span><span class="ss">badarith</span><span class="p">,</span><span class="p" data-group-id="7226872167-3">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7226872167-3">]</span><span class="p" data-group-id="7226872167-2">}</span><span class="p" data-group-id="7226872167-1">}</span></code></pre><p>The BIF <a href="../../erts-17.0/doc/html/erlang.html#throw/1"><code class="inline">throw(Any)</code></a> can be used for non-local return from a
│ │ │ -function. It must be evaluated within a <code class="inline">catch</code>, which returns the value <code class="inline">Any</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="9566625714-1">(</span><span class="ss">hello</span><span class="p" data-group-id="9566625714-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6049265222-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="6049265222-2">{</span><span class="ss">badarith</span><span class="p">,</span><span class="p" data-group-id="6049265222-3">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6049265222-3">]</span><span class="p" data-group-id="6049265222-2">}</span><span class="p" data-group-id="6049265222-1">}</span></code></pre><p>The BIF <a href="../../erts-17.0/doc/html/erlang.html#throw/1"><code class="inline">throw(Any)</code></a> can be used for non-local return from a
│ │ │ +function. It must be evaluated within a <code class="inline">catch</code>, which returns the value <code class="inline">Any</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="3521148660-1">(</span><span class="ss">hello</span><span class="p" data-group-id="3521148660-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">hello</span></code></pre><p>If <a href="../../erts-17.0/doc/html/erlang.html#throw/1"><code class="inline">throw/1</code></a> is not evaluated within a catch, a <code class="inline">nocatch</code> run-time
│ │ │  error occurs.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 24, the <code class="inline">catch</code> operator had the lowest precedence, making
│ │ │ -it necessary to add parentheses when combining it with the <code class="inline">match</code> operator:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2364915689-1">(</span><span class="k">catch</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="2364915689-1">)</span><span class="p">.</span><span class="w">
│ │ │ +it necessary to add parentheses when combining it with the <code class="inline">match</code> operator:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7408505129-1">(</span><span class="k">catch</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="7408505129-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">42</span><span class="w">
│ │ │  </span><span class="gp unselectable">2&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">42</span></code></pre><p>Starting from Erlang/OTP 24, the parentheses can be omitted:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="mi">42</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">42</span><span class="w">
│ │ │  </span><span class="gp unselectable">2&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">42</span></code></pre></section><h2 id="try" class="section-heading">
│ │ │    <a href="#try" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Try</span>
│ │ │  </h2>
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w">
│ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ -    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="2258774281-1">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="2258774281-1">]</span><span class="w"> </span><span class="p" data-group-id="2258774281-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="2258774281-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="1249955172-1">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="1249955172-1">]</span><span class="w"> </span><span class="p" data-group-id="1249955172-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="1249955172-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">ExceptionBody1</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="2258774281-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="2258774281-3">]</span><span class="w"> </span><span class="p" data-group-id="2258774281-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="2258774281-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="1249955172-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="1249955172-3">]</span><span class="w"> </span><span class="p" data-group-id="1249955172-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="1249955172-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">ExceptionBodyN</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>This is an enhancement of <a href="expressions.html#catch-and-throw">catch</a>. It gives the
│ │ │  possibility to:</p><ul><li>Distinguish between different exception classes.</li><li>Choose to handle only the desired ones.</li><li>Pass the others on to an enclosing <code class="inline">try</code> or <code class="inline">catch</code>, or to default error
│ │ │  handling.</li></ul><p>Notice that although the keyword <code class="inline">catch</code> is used in the <code class="inline">try</code> expression, there
│ │ │  is not a <code class="inline">catch</code> expression within the <code class="inline">try</code> expression.</p><p>It returns the value of <code class="inline">Exprs</code> (a sequence of expressions <code class="inline">Expr1, ..., ExprN</code>)
│ │ │  unless an exception occurs during the evaluation. In that case the exception is
│ │ │  caught and the patterns <code class="inline">ExceptionPattern</code> with the right exception class
│ │ │ @@ -1038,47 +1038,47 @@
│ │ │  stack trace is bound to the variable when the corresponding <code class="inline">ExceptionPattern</code>
│ │ │  matches.</p><p>If an exception occurs during evaluation of <code class="inline">Exprs</code> but there is no matching
│ │ │  <code class="inline">ExceptionPattern</code> of the right <code class="inline">Class</code> with a true guard sequence, the
│ │ │  exception is passed on as if <code class="inline">Exprs</code> had not been enclosed in a <code class="inline">try</code>
│ │ │  expression.</p><p>If an exception occurs during evaluation of <code class="inline">ExceptionBody</code>, it is not caught.</p><p>It is allowed to omit <code class="inline">Class</code> and <code class="inline">Stacktrace</code>. An omitted <code class="inline">Class</code> is shorthand
│ │ │  for <code class="inline">throw</code>:</p><pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w">
│ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ -    </span><span class="n">ExceptionPattern1</span><span class="w"> </span><span class="p" data-group-id="5050041835-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="5050041835-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">ExceptionPattern1</span><span class="w"> </span><span class="p" data-group-id="2123646618-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="2123646618-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">ExceptionBody1</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">ExceptionPatternN</span><span class="w"> </span><span class="p" data-group-id="5050041835-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="5050041835-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">ExceptionPatternN</span><span class="w"> </span><span class="p" data-group-id="2123646618-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="2123646618-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">ExceptionBodyN</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>The <code class="inline">try</code> expression can have an <code class="inline">of</code> section:</p><pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="4110984550-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="4110984550-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="9411925833-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="9411925833-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="4110984550-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="4110984550-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="9411925833-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="9411925833-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ -    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="4110984550-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="4110984550-3">]</span><span class="w"> </span><span class="p" data-group-id="4110984550-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="4110984550-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="9411925833-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="9411925833-3">]</span><span class="w"> </span><span class="p" data-group-id="9411925833-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="9411925833-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">ExceptionBody1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="4110984550-5">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="4110984550-5">]</span><span class="w"> </span><span class="p" data-group-id="4110984550-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="4110984550-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="9411925833-5">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="9411925833-5">]</span><span class="w"> </span><span class="p" data-group-id="9411925833-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="9411925833-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">ExceptionBodyN</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>If the evaluation of <code class="inline">Exprs</code> succeeds without an exception, the patterns
│ │ │  <code class="inline">Pattern</code> are sequentially matched against the result in the same way as for a
│ │ │  <a href="expressions.html#case">case</a> expression, except that if the matching fails, a
│ │ │  <code class="inline">try_clause</code> run-time error occurs instead of a <code class="inline">case_clause</code>.</p><p>Only exceptions occurring during the evaluation of <code class="inline">Exprs</code> can be caught by the
│ │ │  <code class="inline">catch</code> section. Exceptions occurring in a <code class="inline">Body</code> or due to a failed match are
│ │ │  not caught.</p><p>The <code class="inline">try</code> expression can also be augmented with an <code class="inline">after</code> section, intended to
│ │ │  be used for cleanup with side effects:</p><pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="9749010652-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="9749010652-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="7874775923-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="7874775923-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="9749010652-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="9749010652-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="7874775923-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="7874775923-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ -    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="9749010652-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="9749010652-3">]</span><span class="w"> </span><span class="p" data-group-id="9749010652-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="9749010652-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="7874775923-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="7874775923-3">]</span><span class="w"> </span><span class="p" data-group-id="7874775923-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="7874775923-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">ExceptionBody1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="9749010652-5">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="9749010652-5">]</span><span class="w"> </span><span class="p" data-group-id="9749010652-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="9749010652-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="7874775923-5">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="7874775923-5">]</span><span class="w"> </span><span class="p" data-group-id="7874775923-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="7874775923-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">ExceptionBodyN</span><span class="w">
│ │ │  </span><span class="k">after</span><span class="w">
│ │ │      </span><span class="n">AfterBody</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p><code class="inline">AfterBody</code> is evaluated after either <code class="inline">Body</code> or <code class="inline">ExceptionBody</code>, no matter which
│ │ │  one. The evaluated value of <code class="inline">AfterBody</code> is lost; the return value of the <code class="inline">try</code>
│ │ │  expression is the same with an <code class="inline">after</code> section as without.</p><p>Even if an exception occurs during evaluation of <code class="inline">Body</code> or <code class="inline">ExceptionBody</code>,
│ │ │  <code class="inline">AfterBody</code> is evaluated. In this case the exception is passed on after
│ │ │ @@ -1101,40 +1101,40 @@
│ │ │          </span><span class="n">ExceptionBody</span><span class="w">
│ │ │  </span><span class="k">after</span><span class="w">
│ │ │      </span><span class="n">AfterBody</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="w">
│ │ │  
│ │ │  </span><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w"> </span><span class="k">after</span><span class="w"> </span><span class="n">AfterBody</span><span class="w"> </span><span class="k">end</span></code></pre><p>Next is an example of using <code class="inline">after</code>. This closes the file, even in the event of
│ │ │  exceptions in <a href="../../lib/kernel-11.0/doc/html/file.html#read/2"><code class="inline">file:read/2</code></a> or in <a href="../../erts-17.0/doc/html/erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a>. The
│ │ │ -exceptions are the same as without the <code class="inline">try</code>...<code class="inline">after</code>...<code class="inline">end</code> expression:</p><pre><code class="makeup erlang" translate="no"><span class="nf">termize_file</span><span class="p" data-group-id="3702117946-1">(</span><span class="n">Name</span><span class="p" data-group-id="3702117946-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3702117946-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="n">F</span><span class="p" data-group-id="3702117946-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="3702117946-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3702117946-4">[</span><span class="ss">read</span><span class="p">,</span><span class="ss">binary</span><span class="p" data-group-id="3702117946-4">]</span><span class="p" data-group-id="3702117946-3">)</span><span class="p">,</span><span class="w">
│ │ │ +exceptions are the same as without the <code class="inline">try</code>...<code class="inline">after</code>...<code class="inline">end</code> expression:</p><pre><code class="makeup erlang" translate="no"><span class="nf">termize_file</span><span class="p" data-group-id="3289200328-1">(</span><span class="n">Name</span><span class="p" data-group-id="3289200328-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3289200328-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="n">F</span><span class="p" data-group-id="3289200328-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="3289200328-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3289200328-4">[</span><span class="ss">read</span><span class="p">,</span><span class="ss">binary</span><span class="p" data-group-id="3289200328-4">]</span><span class="p" data-group-id="3289200328-3">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">try</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3702117946-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="n">Bin</span><span class="p" data-group-id="3702117946-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="3702117946-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">1024</span><span class="o">*</span><span class="mi">1024</span><span class="p" data-group-id="3702117946-6">)</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="nf">binary_to_term</span><span class="p" data-group-id="3702117946-7">(</span><span class="n">Bin</span><span class="p" data-group-id="3702117946-7">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3289200328-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="n">Bin</span><span class="p" data-group-id="3289200328-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="3289200328-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">1024</span><span class="o">*</span><span class="mi">1024</span><span class="p" data-group-id="3289200328-6">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="nf">binary_to_term</span><span class="p" data-group-id="3289200328-7">(</span><span class="n">Bin</span><span class="p" data-group-id="3289200328-7">)</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w">
│ │ │ -        </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="3702117946-8">(</span><span class="n">F</span><span class="p" data-group-id="3702117946-8">)</span><span class="w">
│ │ │ +        </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="3289200328-8">(</span><span class="n">F</span><span class="p" data-group-id="3289200328-8">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Next is an example of using <code class="inline">try</code> to emulate <code class="inline">catch Expr</code>:</p><pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Expr</span><span class="w">
│ │ │  </span><span class="k">catch</span><span class="w">
│ │ │      </span><span class="nc">throw</span><span class="p">:</span><span class="n">Term</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Term</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="nc">exit</span><span class="p">:</span><span class="n">Reason</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1581438048-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="n">Reason</span><span class="p" data-group-id="1581438048-1">}</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="nc">error</span><span class="p">:</span><span class="n">Reason</span><span class="p">:</span><span class="n">Stk</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1581438048-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="1581438048-3">{</span><span class="n">Reason</span><span class="p">,</span><span class="n">Stk</span><span class="p" data-group-id="1581438048-3">}</span><span class="p" data-group-id="1581438048-2">}</span><span class="w">
│ │ │ +    </span><span class="nc">exit</span><span class="p">:</span><span class="n">Reason</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6258092193-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="n">Reason</span><span class="p" data-group-id="6258092193-1">}</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nc">error</span><span class="p">:</span><span class="n">Reason</span><span class="p">:</span><span class="n">Stk</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6258092193-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="6258092193-3">{</span><span class="n">Reason</span><span class="p">,</span><span class="n">Stk</span><span class="p" data-group-id="6258092193-3">}</span><span class="p" data-group-id="6258092193-2">}</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>Variables bound in the various parts of these expressions have different scopes.
│ │ │  Variables bound just after the <code class="inline">try</code> keyword are:</p><ul><li>bound in the <code class="inline">of</code> section</li><li>unsafe in both the <code class="inline">catch</code> and <code class="inline">after</code> sections, as well as after the whole
│ │ │  construct</li></ul><p>Variables bound in the <code class="inline">of</code> section are:</p><ul><li>unbound in the <code class="inline">catch</code> section</li><li>unsafe in the <code class="inline">after</code> section, as well as after the whole construct</li></ul><p>Variables bound in the <code class="inline">catch</code> section are unsafe in the <code class="inline">after</code> section, as
│ │ │  well as after the whole construct.</p><p>Variables bound in the <code class="inline">after</code> section are unsafe after the whole construct.</p><h2 id="parenthesized-expressions" class="section-heading">
│ │ │    <a href="#parenthesized-expressions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Parenthesized Expressions</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2039542218-1">(</span><span class="n">Expr</span><span class="p" data-group-id="2039542218-1">)</span></code></pre><p>Parenthesized expressions are useful to override
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9110428769-1">(</span><span class="n">Expr</span><span class="p" data-group-id="9110428769-1">)</span></code></pre><p>Parenthesized expressions are useful to override
│ │ │  <a href="expressions.html#prec">operator precedences</a>, for example, in arithmetic
│ │ │  expressions:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">7</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="7086272901-1">(</span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="7086272901-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="2332094183-1">(</span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="2332094183-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">9</span></code></pre><h2 id="block-expressions" class="section-heading">
│ │ │    <a href="#block-expressions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Block Expressions</span>
│ │ │  </h2>
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">begin</span><span class="w">
│ │ │ @@ -1146,82 +1146,82 @@
│ │ │    <a href="#comprehensions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Comprehensions</span>
│ │ │  </h2>
│ │ │  <p>Comprehensions provide a succinct notation for iterating over one or more terms
│ │ │  and constructing a new term. Comprehensions come in three different flavors,
│ │ │ -depending on the type of term they build.</p><p>List comprehensions construct lists. They have the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8387688818-1">[</span><span class="n">Expr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="p" data-group-id="8387688818-1">]</span></code></pre><p>Here, <code class="inline">Expr</code> is an arbitrary expression, and each <code class="inline">Qualifier</code> is either a
│ │ │ +depending on the type of term they build.</p><p>List comprehensions construct lists. They have the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0670135464-1">[</span><span class="n">Expr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="p" data-group-id="0670135464-1">]</span></code></pre><p>Here, <code class="inline">Expr</code> is an arbitrary expression, and each <code class="inline">Qualifier</code> is either a
│ │ │  <strong>generator</strong> or a <strong>filter</strong>.</p><p>Bit string comprehensions construct bit strings or binaries. They have the
│ │ │ -following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3053427388-1">&lt;&lt;</span><span class="w"> </span><span class="n">BitStringExpr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="w"> </span><span class="p" data-group-id="3053427388-1">&gt;&gt;</span></code></pre><p><code class="inline">BitStringExpr</code> is an expression that evaluates to a bit string. If
│ │ │ +following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8174359276-1">&lt;&lt;</span><span class="w"> </span><span class="n">BitStringExpr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="w"> </span><span class="p" data-group-id="8174359276-1">&gt;&gt;</span></code></pre><p><code class="inline">BitStringExpr</code> is an expression that evaluates to a bit string. If
│ │ │  <code class="inline">BitStringExpr</code> is a function call, it must be enclosed in parentheses. Each
│ │ │ -<code class="inline">Qualifier</code> is either a <strong>generator</strong> or a <strong>filter</strong>.</p><p>Map comprehensions construct maps. They have the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6438072423-1">#{</span><span class="n">KeyExpr</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">ValueExpr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="p" data-group-id="6438072423-1">}</span></code></pre><p>Here, <code class="inline">KeyExpr</code> and <code class="inline">ValueExpr</code> are arbitrary expressions, and each <code class="inline">Qualifier</code>
│ │ │ +<code class="inline">Qualifier</code> is either a <strong>generator</strong> or a <strong>filter</strong>.</p><p>Map comprehensions construct maps. They have the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4791391572-1">#{</span><span class="n">KeyExpr</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">ValueExpr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="p" data-group-id="4791391572-1">}</span></code></pre><p>Here, <code class="inline">KeyExpr</code> and <code class="inline">ValueExpr</code> are arbitrary expressions, and each <code class="inline">Qualifier</code>
│ │ │  is either a <strong>generator</strong> or a <strong>filter</strong>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Map comprehensions and map generators were introduced in Erlang/OTP 26.</p></section><p>There are four kinds of generators. Three of them have a relaxed and a strict
│ │ │  variant. The fourth kind of generator, zip generator, is composed of two or
│ │ │  more non-zip generators.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Strict generators and zip generators were introduced in Erlang/OTP 28.
│ │ │  Using strict generators is a better practice when either strict or relaxed
│ │ │  generators work. More details are in
│ │ │  <a href="../../doc/system/list_comprehensions.html">Programming Examples</a>.</p></section><p>A <em>list generator</em> has the following syntax for relaxed:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">ListExpr</span></code></pre><p>and strict variant:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">ListExpr</span></code></pre><p>where <code class="inline">ListExpr</code> is an expression that evaluates to a list of terms.</p><p>A <em>bit string generator</em> has the following syntax for relaxed:</p><pre><code class="makeup erlang" translate="no"><span class="n">BitstringPattern</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">BitStringExpr</span></code></pre><p>and strict variant:</p><pre><code class="makeup erlang" translate="no"><span class="n">BitstringPattern</span><span class="w"> </span><span class="o">&lt;:=</span><span class="w"> </span><span class="n">BitStringExpr</span></code></pre><p>where <code class="inline">BitStringExpr</code> is an expression that evaluates to a bit string.</p><p>A <em>map generator</em> has the following syntax for relaxed:</p><pre><code class="makeup erlang" translate="no"><span class="n">KeyPattern</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">ValuePattern</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">MapExpression</span></code></pre><p>and strict variant:</p><pre><code class="makeup erlang" translate="no"><span class="n">KeyPattern</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">ValuePattern</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">MapExpression</span></code></pre><p>where <code class="inline">MapExpression</code> is an expression that evaluates to a map or a map iterator
│ │ │  obtained by calling <a href="../../lib/stdlib-8.0/doc/html/maps.html#iterator/1"><code class="inline">maps:iterator/1</code></a> or <a href="../../lib/stdlib-8.0/doc/html/maps.html#iterator/2"><code class="inline">maps:iterator/2</code></a>.</p><p>A <em>zip generator</em> has the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">Generator_1</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Generator_n</span></code></pre><p>where every <code class="inline">Generator_i</code> is a non-zip generator. Generators within a zip
│ │ │  generator are treated as one generator and evaluated in parallel.</p><p>A <em>filter</em> is an expression that evaluates to <code class="inline">true</code> or <code class="inline">false</code>.</p><p>The variables in the generator patterns shadow previously bound variables,
│ │ │  including variables bound in a previous generator pattern.</p><p>Variables bound in a generator expression are not visible outside the
│ │ │ -expression:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="0863512453-1">[</span><span class="p" data-group-id="0863512453-2">{</span><span class="n">E</span><span class="p">,</span><span class="n">L</span><span class="p" data-group-id="0863512453-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="o">=</span><span class="p" data-group-id="0863512453-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0863512453-3">]</span><span class="p" data-group-id="0863512453-1">]</span><span class="p">.</span><span class="w">
│ │ │ +expression:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8766291761-1">[</span><span class="p" data-group-id="8766291761-2">{</span><span class="n">E</span><span class="p">,</span><span class="n">L</span><span class="p" data-group-id="8766291761-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="o">=</span><span class="p" data-group-id="8766291761-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8766291761-3">]</span><span class="p" data-group-id="8766291761-1">]</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">* 1:5: variable &#39;L&#39; is unbound</span></code></pre><p>A <strong>list comprehension</strong> returns a list, where the list elements are the result
│ │ │  of evaluating <code class="inline">Expr</code> for each combination of generator elements for which all
│ │ │  filters are true.</p><p>A <strong>bit string comprehension</strong> returns a bit string, which is created by
│ │ │  concatenating the results of evaluating <code class="inline">BitStringExpr</code> for each combination of
│ │ │  bit string generator elements for which all filters are true.</p><p>A <strong>map comprehension</strong> returns a map, where the map elements are the result of
│ │ │  evaluating <code class="inline">KeyExpr</code> and <code class="inline">ValueExpr</code> for each combination of generator elements
│ │ │  for which all filters are true. If the key expressions are not unique, the last
│ │ │ -occurrence is stored in the map.</p><p><strong>Examples:</strong></p><p>Multiplying each element in a list by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5303847250-1">[</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="5303847250-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5303847250-2">]</span><span class="p" data-group-id="5303847250-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5303847250-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="5303847250-3">]</span></code></pre><p>Multiplying each byte in a binary by two, returning a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5542675727-1">[</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="5542675727-2">&lt;&lt;</span><span class="n">X</span><span class="p" data-group-id="5542675727-2">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;:=</span><span class="w"> </span><span class="p" data-group-id="5542675727-3">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5542675727-3">&gt;&gt;</span><span class="p" data-group-id="5542675727-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5542675727-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="5542675727-4">]</span></code></pre><p>Multiplying each byte in a binary by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="2220901928-1">&lt;&lt;</span><span class="w"> </span><span class="p" data-group-id="2220901928-2">&lt;&lt;</span><span class="p" data-group-id="2220901928-3">(</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="p" data-group-id="2220901928-3">)</span><span class="p" data-group-id="2220901928-2">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="2220901928-4">&lt;&lt;</span><span class="n">X</span><span class="p" data-group-id="2220901928-4">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;:=</span><span class="w"> </span><span class="p" data-group-id="2220901928-5">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2220901928-5">&gt;&gt;</span><span class="w"> </span><span class="p" data-group-id="2220901928-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2220901928-6">&lt;&lt;</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2220901928-6">&gt;&gt;</span></code></pre><p>Multiplying each element in a list by two, returning a binary:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="2004959359-1">&lt;&lt;</span><span class="w"> </span><span class="p" data-group-id="2004959359-2">&lt;&lt;</span><span class="p" data-group-id="2004959359-3">(</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="p" data-group-id="2004959359-3">)</span><span class="p" data-group-id="2004959359-2">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="2004959359-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2004959359-4">]</span><span class="w"> </span><span class="p" data-group-id="2004959359-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2004959359-5">&lt;&lt;</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2004959359-5">&gt;&gt;</span></code></pre><p>Creating a mapping from an integer to its square:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8436573392-1">#{</span><span class="n">X</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">*</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="8436573392-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8436573392-2">]</span><span class="p" data-group-id="8436573392-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8436573392-3">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="8436573392-3">}</span></code></pre><p>Multiplying the value of each element in a map by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3539939433-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="o">*</span><span class="n">V</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="3539939433-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3539939433-2">}</span><span class="p" data-group-id="3539939433-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3539939433-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p" data-group-id="3539939433-3">}</span></code></pre><p>Filtering a list, keeping odd numbers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="0316943366-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="0316943366-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0316943366-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="0316943366-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0316943366-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0316943366-3">]</span></code></pre><p>Filtering a list, keeping only elements that match:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9177522622-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="9177522622-2">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9177522622-2">}</span><span class="o">=</span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="9177522622-3">[</span><span class="p" data-group-id="9177522622-4">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9177522622-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9177522622-5">[</span><span class="ss">a</span><span class="p" data-group-id="9177522622-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9177522622-6">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="9177522622-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9177522622-7">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9177522622-7">}</span><span class="p" data-group-id="9177522622-3">]</span><span class="p" data-group-id="9177522622-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9177522622-8">[</span><span class="p" data-group-id="9177522622-9">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9177522622-9">}</span><span class="p">,</span><span class="p" data-group-id="9177522622-10">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9177522622-10">}</span><span class="p" data-group-id="9177522622-8">]</span></code></pre><p>Filtering a list, crashing when the element is not a 2-tuple:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="0408513444-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="0408513444-2">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0408513444-2">}</span><span class="o">=</span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="0408513444-3">[</span><span class="p" data-group-id="0408513444-4">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="0408513444-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0408513444-5">[</span><span class="ss">a</span><span class="p" data-group-id="0408513444-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0408513444-6">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="0408513444-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0408513444-7">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0408513444-7">}</span><span class="p" data-group-id="0408513444-3">]</span><span class="p" data-group-id="0408513444-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gt">** exception error: no match of right hand side value [a]</span></code></pre><p>Combining elements from two list generators:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4801627913-1">[</span><span class="p" data-group-id="4801627913-2">{</span><span class="n">P</span><span class="p">,</span><span class="n">Q</span><span class="p" data-group-id="4801627913-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="4801627913-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4801627913-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="4801627913-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4801627913-4">]</span><span class="p" data-group-id="4801627913-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4801627913-5">[</span><span class="p" data-group-id="4801627913-6">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4801627913-6">}</span><span class="p">,</span><span class="p" data-group-id="4801627913-7">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4801627913-7">}</span><span class="p">,</span><span class="p" data-group-id="4801627913-8">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4801627913-8">}</span><span class="p">,</span><span class="p" data-group-id="4801627913-9">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4801627913-9">}</span><span class="p">,</span><span class="p" data-group-id="4801627913-10">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4801627913-10">}</span><span class="p">,</span><span class="p" data-group-id="4801627913-11">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4801627913-11">}</span><span class="p" data-group-id="4801627913-5">]</span></code></pre><p>Combining elements from two list generators, using a zip generator:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="2783752762-1">[</span><span class="p" data-group-id="2783752762-2">{</span><span class="n">P</span><span class="p">,</span><span class="n">Q</span><span class="p" data-group-id="2783752762-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="2783752762-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="2783752762-3">]</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="2783752762-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2783752762-4">]</span><span class="p" data-group-id="2783752762-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2783752762-5">[</span><span class="p" data-group-id="2783752762-6">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2783752762-6">}</span><span class="p">,</span><span class="p" data-group-id="2783752762-7">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2783752762-7">}</span><span class="p">,</span><span class="p" data-group-id="2783752762-8">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2783752762-8">}</span><span class="p" data-group-id="2783752762-5">]</span></code></pre><p>Combining elements from two list generators using a zip generator, filtering
│ │ │ -out odd numbers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="6806586784-1">[</span><span class="p" data-group-id="6806586784-2">{</span><span class="n">P</span><span class="p">,</span><span class="n">Q</span><span class="p" data-group-id="6806586784-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="6806586784-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6806586784-3">]</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="6806586784-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6806586784-4">]</span><span class="p">,</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="6806586784-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6806586784-5">[</span><span class="p" data-group-id="6806586784-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6806586784-6">}</span><span class="p" data-group-id="6806586784-5">]</span></code></pre><p>Filtering out non-matching elements from two lists.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4683145216-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="4683145216-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="4683145216-2">]</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="4683145216-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="4683145216-3">]</span><span class="p" data-group-id="4683145216-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4683145216-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4683145216-4">]</span></code></pre><p>More examples are provided in
│ │ │ +occurrence is stored in the map.</p><p><strong>Examples:</strong></p><p>Multiplying each element in a list by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3532977931-1">[</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="3532977931-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3532977931-2">]</span><span class="p" data-group-id="3532977931-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3532977931-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3532977931-3">]</span></code></pre><p>Multiplying each byte in a binary by two, returning a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7441464270-1">[</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="7441464270-2">&lt;&lt;</span><span class="n">X</span><span class="p" data-group-id="7441464270-2">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;:=</span><span class="w"> </span><span class="p" data-group-id="7441464270-3">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7441464270-3">&gt;&gt;</span><span class="p" data-group-id="7441464270-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7441464270-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7441464270-4">]</span></code></pre><p>Multiplying each byte in a binary by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5622195183-1">&lt;&lt;</span><span class="w"> </span><span class="p" data-group-id="5622195183-2">&lt;&lt;</span><span class="p" data-group-id="5622195183-3">(</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="p" data-group-id="5622195183-3">)</span><span class="p" data-group-id="5622195183-2">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="5622195183-4">&lt;&lt;</span><span class="n">X</span><span class="p" data-group-id="5622195183-4">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;:=</span><span class="w"> </span><span class="p" data-group-id="5622195183-5">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5622195183-5">&gt;&gt;</span><span class="w"> </span><span class="p" data-group-id="5622195183-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5622195183-6">&lt;&lt;</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="5622195183-6">&gt;&gt;</span></code></pre><p>Multiplying each element in a list by two, returning a binary:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="0806704491-1">&lt;&lt;</span><span class="w"> </span><span class="p" data-group-id="0806704491-2">&lt;&lt;</span><span class="p" data-group-id="0806704491-3">(</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="p" data-group-id="0806704491-3">)</span><span class="p" data-group-id="0806704491-2">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="0806704491-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0806704491-4">]</span><span class="w"> </span><span class="p" data-group-id="0806704491-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0806704491-5">&lt;&lt;</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="0806704491-5">&gt;&gt;</span></code></pre><p>Creating a mapping from an integer to its square:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3840926055-1">#{</span><span class="n">X</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">*</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="3840926055-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3840926055-2">]</span><span class="p" data-group-id="3840926055-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3840926055-3">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="3840926055-3">}</span></code></pre><p>Multiplying the value of each element in a map by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5323912943-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="o">*</span><span class="n">V</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="5323912943-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="5323912943-2">}</span><span class="p" data-group-id="5323912943-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5323912943-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p" data-group-id="5323912943-3">}</span></code></pre><p>Filtering a list, keeping odd numbers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="2620191039-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="2620191039-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="2620191039-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2620191039-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2620191039-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="2620191039-3">]</span></code></pre><p>Filtering a list, keeping only elements that match:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="1277895243-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="1277895243-2">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1277895243-2">}</span><span class="o">=</span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="1277895243-3">[</span><span class="p" data-group-id="1277895243-4">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1277895243-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1277895243-5">[</span><span class="ss">a</span><span class="p" data-group-id="1277895243-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1277895243-6">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="1277895243-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1277895243-7">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1277895243-7">}</span><span class="p" data-group-id="1277895243-3">]</span><span class="p" data-group-id="1277895243-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1277895243-8">[</span><span class="p" data-group-id="1277895243-9">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1277895243-9">}</span><span class="p">,</span><span class="p" data-group-id="1277895243-10">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1277895243-10">}</span><span class="p" data-group-id="1277895243-8">]</span></code></pre><p>Filtering a list, crashing when the element is not a 2-tuple:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4255492337-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="4255492337-2">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4255492337-2">}</span><span class="o">=</span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="4255492337-3">[</span><span class="p" data-group-id="4255492337-4">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="4255492337-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4255492337-5">[</span><span class="ss">a</span><span class="p" data-group-id="4255492337-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4255492337-6">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="4255492337-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4255492337-7">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4255492337-7">}</span><span class="p" data-group-id="4255492337-3">]</span><span class="p" data-group-id="4255492337-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gt">** exception error: no match of right hand side value [a]</span></code></pre><p>Combining elements from two list generators:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4539158999-1">[</span><span class="p" data-group-id="4539158999-2">{</span><span class="n">P</span><span class="p">,</span><span class="n">Q</span><span class="p" data-group-id="4539158999-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="4539158999-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4539158999-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="4539158999-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4539158999-4">]</span><span class="p" data-group-id="4539158999-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4539158999-5">[</span><span class="p" data-group-id="4539158999-6">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4539158999-6">}</span><span class="p">,</span><span class="p" data-group-id="4539158999-7">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4539158999-7">}</span><span class="p">,</span><span class="p" data-group-id="4539158999-8">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4539158999-8">}</span><span class="p">,</span><span class="p" data-group-id="4539158999-9">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4539158999-9">}</span><span class="p">,</span><span class="p" data-group-id="4539158999-10">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4539158999-10">}</span><span class="p">,</span><span class="p" data-group-id="4539158999-11">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4539158999-11">}</span><span class="p" data-group-id="4539158999-5">]</span></code></pre><p>Combining elements from two list generators, using a zip generator:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="2659291638-1">[</span><span class="p" data-group-id="2659291638-2">{</span><span class="n">P</span><span class="p">,</span><span class="n">Q</span><span class="p" data-group-id="2659291638-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="2659291638-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="2659291638-3">]</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="2659291638-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2659291638-4">]</span><span class="p" data-group-id="2659291638-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2659291638-5">[</span><span class="p" data-group-id="2659291638-6">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2659291638-6">}</span><span class="p">,</span><span class="p" data-group-id="2659291638-7">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2659291638-7">}</span><span class="p">,</span><span class="p" data-group-id="2659291638-8">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2659291638-8">}</span><span class="p" data-group-id="2659291638-5">]</span></code></pre><p>Combining elements from two list generators using a zip generator, filtering
│ │ │ +out odd numbers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="2642625365-1">[</span><span class="p" data-group-id="2642625365-2">{</span><span class="n">P</span><span class="p">,</span><span class="n">Q</span><span class="p" data-group-id="2642625365-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="2642625365-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="2642625365-3">]</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="2642625365-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2642625365-4">]</span><span class="p">,</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="2642625365-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2642625365-5">[</span><span class="p" data-group-id="2642625365-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2642625365-6">}</span><span class="p" data-group-id="2642625365-5">]</span></code></pre><p>Filtering out non-matching elements from two lists.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="0406496951-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="0406496951-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0406496951-2">]</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="0406496951-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="0406496951-3">]</span><span class="p" data-group-id="0406496951-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0406496951-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0406496951-4">]</span></code></pre><p>More examples are provided in
│ │ │  <a href="../../doc/system/list_comprehensions.html">Programming Examples</a>.</p><p>When there are no generators, a comprehension returns either a term constructed
│ │ │  from a single element (the result of evaluating <code class="inline">Expr</code>) if all filters are true,
│ │ │  or a term constructed from no elements (that is, <code class="inline">[]</code> for list comprehension,
│ │ │ -<code class="inline">&lt;&lt;&gt;&gt;</code> for a bit string comprehension, and <code class="inline">#{}</code> for a map comprehension).</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4836182084-1">[</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="4836182084-2">(</span><span class="mi">2</span><span class="p" data-group-id="4836182084-2">)</span><span class="p" data-group-id="4836182084-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4836182084-3">[</span><span class="mi">2</span><span class="p" data-group-id="4836182084-3">]</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="4836182084-4">[</span><span class="ss">x</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="4836182084-5">(</span><span class="ss">x</span><span class="p" data-group-id="4836182084-5">)</span><span class="p" data-group-id="4836182084-4">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4836182084-6">[</span><span class="p" data-group-id="4836182084-6">]</span></code></pre><p>What happens when the filter expression does not evaluate to a boolean value
│ │ │ +<code class="inline">&lt;&lt;&gt;&gt;</code> for a bit string comprehension, and <code class="inline">#{}</code> for a map comprehension).</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7405945999-1">[</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="7405945999-2">(</span><span class="mi">2</span><span class="p" data-group-id="7405945999-2">)</span><span class="p" data-group-id="7405945999-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7405945999-3">[</span><span class="mi">2</span><span class="p" data-group-id="7405945999-3">]</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="7405945999-4">[</span><span class="ss">x</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="7405945999-5">(</span><span class="ss">x</span><span class="p" data-group-id="7405945999-5">)</span><span class="p" data-group-id="7405945999-4">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7405945999-6">[</span><span class="p" data-group-id="7405945999-6">]</span></code></pre><p>What happens when the filter expression does not evaluate to a boolean value
│ │ │  depends on the expression:</p><ul><li>If the expression is a <a href="expressions.html#guard-expressions">guard expression</a>,
│ │ │  failure to evaluate or evaluating to a non-boolean value is equivalent to
│ │ │  evaluating to <code class="inline">false</code>.</li><li>If the expression is not a guard expression and evaluates to a non-Boolean
│ │ │  value <code class="inline">Val</code>, an exception <code class="inline">{bad_filter, Val}</code> is triggered at runtime. If the
│ │ │  evaluation of the expression raises an exception, it is not caught by the
│ │ │ -comprehension.</li></ul><p><strong>Examples</strong> (using a guard expression as filter):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9827266096-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9827266096-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9827266096-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9827266096-2">]</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="9827266096-3">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="9827266096-3">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9827266096-4">[</span><span class="p" data-group-id="9827266096-4">]</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="9827266096-5">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="9827266096-5">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9827266096-6">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9827266096-6">]</span></code></pre><p><strong>Examples</strong> (using a non-guard expression as filter):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0789658521-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0789658521-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0789658521-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0789658521-2">]</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">FaultyIsEven</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0789658521-3">(</span><span class="n">E</span><span class="p" data-group-id="0789658521-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +comprehension.</li></ul><p><strong>Examples</strong> (using a guard expression as filter):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3339026420-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3339026420-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3339026420-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3339026420-2">]</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="3339026420-3">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="3339026420-3">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3339026420-4">[</span><span class="p" data-group-id="3339026420-4">]</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="3339026420-5">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="3339026420-5">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3339026420-6">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3339026420-6">]</span></code></pre><p><strong>Examples</strong> (using a non-guard expression as filter):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5191658230-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5191658230-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5191658230-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5191658230-2">]</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">FaultyIsEven</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="5191658230-3">(</span><span class="n">E</span><span class="p" data-group-id="5191658230-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">42.17316486</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="0789658521-4">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">FaultyIsEven</span><span class="p" data-group-id="0789658521-5">(</span><span class="n">E</span><span class="p" data-group-id="0789658521-5">)</span><span class="p" data-group-id="0789658521-4">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="p" data-group-id="5191658230-4">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">FaultyIsEven</span><span class="p" data-group-id="5191658230-5">(</span><span class="n">E</span><span class="p" data-group-id="5191658230-5">)</span><span class="p" data-group-id="5191658230-4">]</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: bad filter 1</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="n">IsEven</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0789658521-6">(</span><span class="n">E</span><span class="p" data-group-id="0789658521-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="n">IsEven</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="5191658230-6">(</span><span class="n">E</span><span class="p" data-group-id="5191658230-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">42.17316486</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="0789658521-7">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">IsEven</span><span class="p" data-group-id="0789658521-8">(</span><span class="n">E</span><span class="p" data-group-id="0789658521-8">)</span><span class="p" data-group-id="0789658521-7">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="5191658230-7">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">IsEven</span><span class="p" data-group-id="5191658230-8">(</span><span class="n">E</span><span class="p" data-group-id="5191658230-8">)</span><span class="p" data-group-id="5191658230-7">]</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: an error occurred when evaluating an arithmetic expression
│ │ │       in operator  rem/2
│ │ │          called as a rem 2</span><span class="w">
│ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="p" data-group-id="0789658521-9">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="0789658521-10">(</span><span class="n">E</span><span class="p" data-group-id="0789658521-10">)</span><span class="p">,</span><span class="w"> </span><span class="n">IsEven</span><span class="p" data-group-id="0789658521-11">(</span><span class="n">E</span><span class="p" data-group-id="0789658521-11">)</span><span class="p" data-group-id="0789658521-9">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0789658521-12">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0789658521-12">]</span></code></pre><p><a href="" id="guards"></a></p><h2 id="guard-sequences" class="section-heading">
│ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="p" data-group-id="5191658230-9">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="5191658230-10">(</span><span class="n">E</span><span class="p" data-group-id="5191658230-10">)</span><span class="p">,</span><span class="w"> </span><span class="n">IsEven</span><span class="p" data-group-id="5191658230-11">(</span><span class="n">E</span><span class="p" data-group-id="5191658230-11">)</span><span class="p" data-group-id="5191658230-9">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5191658230-12">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5191658230-12">]</span></code></pre><p><a href="" id="guards"></a></p><h2 id="guard-sequences" class="section-heading">
│ │ │    <a href="#guard-sequences" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Guard Sequences</span>
│ │ │  </h2>
│ │ │  <p>A <em>guard sequence</em> is a sequence of guards, separated by semicolon (<code class="inline">;</code>). The
│ │ │  guard sequence is true if at least one of the guards is true. (The remaining
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/funs.html
│ │ │ @@ -117,402 +117,402 @@
│ │ │  
│ │ │  <h2 id="map" class="section-heading">
│ │ │    <a href="#map" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">map</span>
│ │ │  </h2>
│ │ │ -<p>The following function, <code class="inline">double</code>, doubles every element in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">double</span><span class="p" data-group-id="0255450271-1">(</span><span class="p" data-group-id="0255450271-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0255450271-2">]</span><span class="p" data-group-id="0255450271-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0255450271-3">[</span><span class="mi">2</span><span class="o">*</span><span class="n">H</span><span class="p">|</span><span class="nf">double</span><span class="p" data-group-id="0255450271-4">(</span><span class="n">T</span><span class="p" data-group-id="0255450271-4">)</span><span class="p" data-group-id="0255450271-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">double</span><span class="p" data-group-id="0255450271-5">(</span><span class="p" data-group-id="0255450271-6">[</span><span class="p" data-group-id="0255450271-6">]</span><span class="p" data-group-id="0255450271-5">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0255450271-7">[</span><span class="p" data-group-id="0255450271-7">]</span><span class="p">.</span></code></pre><p>Hence, the argument entered as input is doubled as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">double</span><span class="p" data-group-id="4761111445-1">(</span><span class="p" data-group-id="4761111445-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4761111445-2">]</span><span class="p" data-group-id="4761111445-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4761111445-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p" data-group-id="4761111445-3">]</span></code></pre><p>The following function, <code class="inline">add_one</code>, adds one to every element in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_one</span><span class="p" data-group-id="5072240514-1">(</span><span class="p" data-group-id="5072240514-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5072240514-2">]</span><span class="p" data-group-id="5072240514-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5072240514-3">[</span><span class="n">H</span><span class="o">+</span><span class="mi">1</span><span class="p">|</span><span class="nf">add_one</span><span class="p" data-group-id="5072240514-4">(</span><span class="n">T</span><span class="p" data-group-id="5072240514-4">)</span><span class="p" data-group-id="5072240514-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">add_one</span><span class="p" data-group-id="5072240514-5">(</span><span class="p" data-group-id="5072240514-6">[</span><span class="p" data-group-id="5072240514-6">]</span><span class="p" data-group-id="5072240514-5">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5072240514-7">[</span><span class="p" data-group-id="5072240514-7">]</span><span class="p">.</span></code></pre><p>The functions <code class="inline">double</code> and <code class="inline">add_one</code> have a similar structure. This can be used
│ │ │ -by writing a function <code class="inline">map</code> that expresses this similarity:</p><pre><code class="makeup erlang" translate="no"><span class="nf">map</span><span class="p" data-group-id="1195467920-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1195467920-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1195467920-2">]</span><span class="p" data-group-id="1195467920-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1195467920-3">[</span><span class="n">F</span><span class="p" data-group-id="1195467920-4">(</span><span class="n">H</span><span class="p" data-group-id="1195467920-4">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="1195467920-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="1195467920-5">)</span><span class="p" data-group-id="1195467920-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="1195467920-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1195467920-7">[</span><span class="p" data-group-id="1195467920-7">]</span><span class="p" data-group-id="1195467920-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1195467920-8">[</span><span class="p" data-group-id="1195467920-8">]</span><span class="p">.</span></code></pre><p>The functions <code class="inline">double</code> and <code class="inline">add_one</code> can now be expressed in terms of <code class="inline">map</code> as
│ │ │ -follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">double</span><span class="p" data-group-id="0410721951-1">(</span><span class="n">L</span><span class="p" data-group-id="0410721951-1">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="0410721951-2">(</span><span class="nf">fun</span><span class="p" data-group-id="0410721951-3">(</span><span class="n">X</span><span class="p" data-group-id="0410721951-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="o">*</span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0410721951-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add_one</span><span class="p" data-group-id="0410721951-4">(</span><span class="n">L</span><span class="p" data-group-id="0410721951-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="0410721951-5">(</span><span class="nf">fun</span><span class="p" data-group-id="0410721951-6">(</span><span class="n">X</span><span class="p" data-group-id="0410721951-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0410721951-5">)</span><span class="p">.</span></code></pre><p><code class="inline">map(F, List)</code> is a function that takes a function <code class="inline">F</code> and a list <code class="inline">L</code> as
│ │ │ +<p>The following function, <code class="inline">double</code>, doubles every element in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">double</span><span class="p" data-group-id="4380395323-1">(</span><span class="p" data-group-id="4380395323-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4380395323-2">]</span><span class="p" data-group-id="4380395323-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4380395323-3">[</span><span class="mi">2</span><span class="o">*</span><span class="n">H</span><span class="p">|</span><span class="nf">double</span><span class="p" data-group-id="4380395323-4">(</span><span class="n">T</span><span class="p" data-group-id="4380395323-4">)</span><span class="p" data-group-id="4380395323-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">double</span><span class="p" data-group-id="4380395323-5">(</span><span class="p" data-group-id="4380395323-6">[</span><span class="p" data-group-id="4380395323-6">]</span><span class="p" data-group-id="4380395323-5">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4380395323-7">[</span><span class="p" data-group-id="4380395323-7">]</span><span class="p">.</span></code></pre><p>Hence, the argument entered as input is doubled as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">double</span><span class="p" data-group-id="8915092055-1">(</span><span class="p" data-group-id="8915092055-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="8915092055-2">]</span><span class="p" data-group-id="8915092055-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8915092055-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p" data-group-id="8915092055-3">]</span></code></pre><p>The following function, <code class="inline">add_one</code>, adds one to every element in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_one</span><span class="p" data-group-id="5068189458-1">(</span><span class="p" data-group-id="5068189458-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5068189458-2">]</span><span class="p" data-group-id="5068189458-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5068189458-3">[</span><span class="n">H</span><span class="o">+</span><span class="mi">1</span><span class="p">|</span><span class="nf">add_one</span><span class="p" data-group-id="5068189458-4">(</span><span class="n">T</span><span class="p" data-group-id="5068189458-4">)</span><span class="p" data-group-id="5068189458-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">add_one</span><span class="p" data-group-id="5068189458-5">(</span><span class="p" data-group-id="5068189458-6">[</span><span class="p" data-group-id="5068189458-6">]</span><span class="p" data-group-id="5068189458-5">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5068189458-7">[</span><span class="p" data-group-id="5068189458-7">]</span><span class="p">.</span></code></pre><p>The functions <code class="inline">double</code> and <code class="inline">add_one</code> have a similar structure. This can be used
│ │ │ +by writing a function <code class="inline">map</code> that expresses this similarity:</p><pre><code class="makeup erlang" translate="no"><span class="nf">map</span><span class="p" data-group-id="0132888989-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0132888989-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0132888989-2">]</span><span class="p" data-group-id="0132888989-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0132888989-3">[</span><span class="n">F</span><span class="p" data-group-id="0132888989-4">(</span><span class="n">H</span><span class="p" data-group-id="0132888989-4">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="0132888989-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="0132888989-5">)</span><span class="p" data-group-id="0132888989-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="0132888989-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0132888989-7">[</span><span class="p" data-group-id="0132888989-7">]</span><span class="p" data-group-id="0132888989-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0132888989-8">[</span><span class="p" data-group-id="0132888989-8">]</span><span class="p">.</span></code></pre><p>The functions <code class="inline">double</code> and <code class="inline">add_one</code> can now be expressed in terms of <code class="inline">map</code> as
│ │ │ +follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">double</span><span class="p" data-group-id="7910658510-1">(</span><span class="n">L</span><span class="p" data-group-id="7910658510-1">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="7910658510-2">(</span><span class="nf">fun</span><span class="p" data-group-id="7910658510-3">(</span><span class="n">X</span><span class="p" data-group-id="7910658510-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="o">*</span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="7910658510-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add_one</span><span class="p" data-group-id="7910658510-4">(</span><span class="n">L</span><span class="p" data-group-id="7910658510-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="7910658510-5">(</span><span class="nf">fun</span><span class="p" data-group-id="7910658510-6">(</span><span class="n">X</span><span class="p" data-group-id="7910658510-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="7910658510-5">)</span><span class="p">.</span></code></pre><p><code class="inline">map(F, List)</code> is a function that takes a function <code class="inline">F</code> and a list <code class="inline">L</code> as
│ │ │  arguments and returns a new list, obtained by applying <code class="inline">F</code> to each of the
│ │ │  elements in <code class="inline">L</code>.</p><p>The process of abstracting out the common features of a number of different
│ │ │  programs is called <em>procedural abstraction</em>. Procedural abstraction can be used
│ │ │  to write several different functions that have a similar structure, but differ
│ │ │  in some minor detail. This is done as follows:</p><ol><li><em>Step 1.</em> Write one function that represents the common features of these
│ │ │  functions.</li><li><em>Step 2.</em> Parameterize the difference in terms of functions that are passed
│ │ │  as arguments to the common function.</li></ol><h2 id="foreach" class="section-heading">
│ │ │    <a href="#foreach" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">foreach</span>
│ │ │  </h2>
│ │ │  <p>This section illustrates procedural abstraction. Initially, the following two
│ │ │ -examples are written as conventional functions.</p><p>This function prints all elements of a list onto a stream:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="5809051442-1">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5809051442-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5809051442-2">]</span><span class="p" data-group-id="5809051442-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5809051442-3">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5809051442-4">[</span><span class="n">H</span><span class="p" data-group-id="5809051442-4">]</span><span class="p" data-group-id="5809051442-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">print_list</span><span class="p" data-group-id="5809051442-5">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="5809051442-5">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">print_list</span><span class="p" data-group-id="5809051442-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5809051442-7">[</span><span class="p" data-group-id="5809051442-7">]</span><span class="p" data-group-id="5809051442-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">true</span><span class="p">.</span></code></pre><p>This function broadcasts a message to a list of processes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">broadcast</span><span class="p" data-group-id="0608502923-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0608502923-2">[</span><span class="n">Pid</span><span class="p">|</span><span class="n">Pids</span><span class="p" data-group-id="0608502923-2">]</span><span class="p" data-group-id="0608502923-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +examples are written as conventional functions.</p><p>This function prints all elements of a list onto a stream:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="2728224191-1">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2728224191-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2728224191-2">]</span><span class="p" data-group-id="2728224191-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2728224191-3">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2728224191-4">[</span><span class="n">H</span><span class="p" data-group-id="2728224191-4">]</span><span class="p" data-group-id="2728224191-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">print_list</span><span class="p" data-group-id="2728224191-5">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="2728224191-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">print_list</span><span class="p" data-group-id="2728224191-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2728224191-7">[</span><span class="p" data-group-id="2728224191-7">]</span><span class="p" data-group-id="2728224191-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">true</span><span class="p">.</span></code></pre><p>This function broadcasts a message to a list of processes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">broadcast</span><span class="p" data-group-id="4612536711-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4612536711-2">[</span><span class="n">Pid</span><span class="p">|</span><span class="n">Pids</span><span class="p" data-group-id="4612536711-2">]</span><span class="p" data-group-id="4612536711-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Msg</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">broadcast</span><span class="p" data-group-id="0608502923-3">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">Pids</span><span class="p" data-group-id="0608502923-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">broadcast</span><span class="p" data-group-id="0608502923-4">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0608502923-5">[</span><span class="p" data-group-id="0608502923-5">]</span><span class="p" data-group-id="0608502923-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">broadcast</span><span class="p" data-group-id="4612536711-3">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">Pids</span><span class="p" data-group-id="4612536711-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">broadcast</span><span class="p" data-group-id="4612536711-4">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4612536711-5">[</span><span class="p" data-group-id="4612536711-5">]</span><span class="p" data-group-id="4612536711-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">true</span><span class="p">.</span></code></pre><p>These two functions have a similar structure. They both iterate over a list and
│ │ │  do something to each element in the list. The &quot;something&quot; is passed on as an
│ │ │ -extra argument to the function that does this.</p><p>The function <code class="inline">foreach</code> expresses this similarity:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="7547233774-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7547233774-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7547233774-2">]</span><span class="p" data-group-id="7547233774-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">F</span><span class="p" data-group-id="7547233774-3">(</span><span class="n">H</span><span class="p" data-group-id="7547233774-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="7547233774-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7547233774-4">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">foreach</span><span class="p" data-group-id="7547233774-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7547233774-6">[</span><span class="p" data-group-id="7547233774-6">]</span><span class="p" data-group-id="7547233774-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>Using the function <code class="inline">foreach</code>, the function <code class="inline">print_list</code> becomes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="9482621574-1">(</span><span class="nf">fun</span><span class="p" data-group-id="9482621574-2">(</span><span class="n">H</span><span class="p" data-group-id="9482621574-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9482621574-3">(</span><span class="n">S</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="9482621574-4">[</span><span class="n">H</span><span class="p" data-group-id="9482621574-4">]</span><span class="p" data-group-id="9482621574-3">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="9482621574-1">)</span></code></pre><p>Using the function <code class="inline">foreach</code>, the function <code class="inline">broadcast</code> becomes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="5871565699-1">(</span><span class="nf">fun</span><span class="p" data-group-id="5871565699-2">(</span><span class="n">Pid</span><span class="p" data-group-id="5871565699-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="5871565699-1">)</span></code></pre><p><code class="inline">foreach</code> is evaluated for its side-effect and not its value. <code class="inline">foreach(Fun, L)</code>
│ │ │ +extra argument to the function that does this.</p><p>The function <code class="inline">foreach</code> expresses this similarity:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="4761822558-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4761822558-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4761822558-2">]</span><span class="p" data-group-id="4761822558-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">F</span><span class="p" data-group-id="4761822558-3">(</span><span class="n">H</span><span class="p" data-group-id="4761822558-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="4761822558-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="4761822558-4">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">foreach</span><span class="p" data-group-id="4761822558-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4761822558-6">[</span><span class="p" data-group-id="4761822558-6">]</span><span class="p" data-group-id="4761822558-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>Using the function <code class="inline">foreach</code>, the function <code class="inline">print_list</code> becomes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="1794601493-1">(</span><span class="nf">fun</span><span class="p" data-group-id="1794601493-2">(</span><span class="n">H</span><span class="p" data-group-id="1794601493-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1794601493-3">(</span><span class="n">S</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="1794601493-4">[</span><span class="n">H</span><span class="p" data-group-id="1794601493-4">]</span><span class="p" data-group-id="1794601493-3">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="1794601493-1">)</span></code></pre><p>Using the function <code class="inline">foreach</code>, the function <code class="inline">broadcast</code> becomes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="6619690668-1">(</span><span class="nf">fun</span><span class="p" data-group-id="6619690668-2">(</span><span class="n">Pid</span><span class="p" data-group-id="6619690668-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="6619690668-1">)</span></code></pre><p><code class="inline">foreach</code> is evaluated for its side-effect and not its value. <code class="inline">foreach(Fun, L)</code>
│ │ │  calls <code class="inline">Fun(X)</code> for each element <code class="inline">X</code> in <code class="inline">L</code> and the processing occurs in the
│ │ │  order that the elements were defined in <code class="inline">L</code>. <code class="inline">map</code> does not define the order in
│ │ │  which its elements are processed.</p><h2 id="syntax-of-funs" class="section-heading">
│ │ │    <a href="#syntax-of-funs" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Syntax of Funs</span>
│ │ │  </h2>
│ │ │  <p>Funs are written with the following syntax (see
│ │ │ -<a href="../../doc/system/expressions.html#fun-expressions">Fun Expressions</a> for full description):</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="9015091801-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="w"> </span><span class="n">Arg2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">ArgN</span><span class="p" data-group-id="9015091801-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +<a href="../../doc/system/expressions.html#fun-expressions">Fun Expressions</a> for full description):</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="0673319931-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="w"> </span><span class="n">Arg2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">ArgN</span><span class="p" data-group-id="0673319931-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │      </span><span class="k">end</span></code></pre><p>This creates an anonymous function of <code class="inline">N</code> arguments and binds it to the variable
│ │ │  <code class="inline">F</code>.</p><p>Another function, <code class="inline">FunctionName</code>, written in the same module, can be passed as
│ │ │  an argument, using the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">FunctionName</span><span class="o">/</span><span class="n">Arity</span></code></pre><p>With this form of function reference, the function that is referred to does not
│ │ │  need to be exported from the module.</p><p>It is also possible to refer to a function defined in a different module, with
│ │ │ -the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">Module</span><span class="p">:</span><span class="n">FunctionName</span><span class="o">/</span><span class="n">Arity</span></code></pre><p>In this case, the function must be exported from the module in question.</p><p>The following program illustrates the different ways of creating funs:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5881137134-1">(</span><span class="ss">fun_test</span><span class="p" data-group-id="5881137134-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5881137134-2">(</span><span class="p" data-group-id="5881137134-3">[</span><span class="ss">t1</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">t2</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5881137134-3">]</span><span class="p" data-group-id="5881137134-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">import</span><span class="p" data-group-id="5881137134-4">(</span><span class="ss">lists</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5881137134-5">[</span><span class="ss">map</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5881137134-5">]</span><span class="p" data-group-id="5881137134-4">)</span><span class="p">.</span><span class="w">
│ │ │ +the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">Module</span><span class="p">:</span><span class="n">FunctionName</span><span class="o">/</span><span class="n">Arity</span></code></pre><p>In this case, the function must be exported from the module in question.</p><p>The following program illustrates the different ways of creating funs:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6746437550-1">(</span><span class="ss">fun_test</span><span class="p" data-group-id="6746437550-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6746437550-2">(</span><span class="p" data-group-id="6746437550-3">[</span><span class="ss">t1</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">t2</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6746437550-3">]</span><span class="p" data-group-id="6746437550-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">import</span><span class="p" data-group-id="6746437550-4">(</span><span class="ss">lists</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6746437550-5">[</span><span class="ss">map</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6746437550-5">]</span><span class="p" data-group-id="6746437550-4">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">t1</span><span class="p" data-group-id="5881137134-6">(</span><span class="p" data-group-id="5881137134-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="5881137134-7">(</span><span class="nf">fun</span><span class="p" data-group-id="5881137134-8">(</span><span class="n">X</span><span class="p" data-group-id="5881137134-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5881137134-9">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5881137134-9">]</span><span class="p" data-group-id="5881137134-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">t1</span><span class="p" data-group-id="6746437550-6">(</span><span class="p" data-group-id="6746437550-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="6746437550-7">(</span><span class="nf">fun</span><span class="p" data-group-id="6746437550-8">(</span><span class="n">X</span><span class="p" data-group-id="6746437550-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6746437550-9">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="6746437550-9">]</span><span class="p" data-group-id="6746437550-7">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">t2</span><span class="p" data-group-id="5881137134-10">(</span><span class="p" data-group-id="5881137134-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="5881137134-11">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5881137134-12">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5881137134-12">]</span><span class="p" data-group-id="5881137134-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">t2</span><span class="p" data-group-id="6746437550-10">(</span><span class="p" data-group-id="6746437550-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="6746437550-11">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6746437550-12">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="6746437550-12">]</span><span class="p" data-group-id="6746437550-11">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">double</span><span class="p" data-group-id="5881137134-13">(</span><span class="n">X</span><span class="p" data-group-id="5881137134-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">2</span><span class="p">.</span></code></pre><p>The fun <code class="inline">F</code> can be evaluated with the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="p" data-group-id="6110505356-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="w"> </span><span class="n">Arg2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Argn</span><span class="p" data-group-id="6110505356-1">)</span></code></pre><p>To check whether a term is a fun, use the test
│ │ │ -<a href="../../erts-17.0/doc/html/erlang.html#is_function/1"><code class="inline">is_function/1</code></a> in a guard.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="8876189387-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="8876189387-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_function</span><span class="p" data-group-id="8876189387-2">(</span><span class="n">F</span><span class="p" data-group-id="8876189387-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="nf">apply</span><span class="p" data-group-id="8876189387-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="8876189387-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="8876189387-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="8876189387-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="8876189387-5">(</span><span class="n">N</span><span class="p" data-group-id="8876189387-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">double</span><span class="p" data-group-id="6746437550-13">(</span><span class="n">X</span><span class="p" data-group-id="6746437550-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">2</span><span class="p">.</span></code></pre><p>The fun <code class="inline">F</code> can be evaluated with the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="p" data-group-id="9203065288-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="w"> </span><span class="n">Arg2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Argn</span><span class="p" data-group-id="9203065288-1">)</span></code></pre><p>To check whether a term is a fun, use the test
│ │ │ +<a href="../../erts-17.0/doc/html/erlang.html#is_function/1"><code class="inline">is_function/1</code></a> in a guard.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="5281329097-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="5281329097-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_function</span><span class="p" data-group-id="5281329097-2">(</span><span class="n">F</span><span class="p" data-group-id="5281329097-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="nf">apply</span><span class="p" data-group-id="5281329097-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="5281329097-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="5281329097-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="5281329097-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="5281329097-5">(</span><span class="n">N</span><span class="p" data-group-id="5281329097-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │     </span><span class="n">N</span><span class="p">.</span></code></pre><p>Funs are a distinct type. The BIFs <code class="inline">erlang:fun_info/1,2</code> can be used to retrieve
│ │ │  information about a fun, and the BIF <a href="../../erts-17.0/doc/html/erlang.html#fun_to_list/1"><code class="inline">erlang:fun_to_list/1</code></a> returns a textual
│ │ │  representation of a fun. The <a href="../../erts-17.0/doc/html/erlang.html#check_process_code/2"><code class="inline">check_process_code/2</code></a>
│ │ │  BIF returns <code class="inline">true</code> if the process contains funs that depend on the old version
│ │ │  of a module.</p><h2 id="variable-bindings-within-a-fun" class="section-heading">
│ │ │    <a href="#variable-bindings-within-a-fun" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Variable Bindings Within a Fun</span>
│ │ │  </h2>
│ │ │  <p>The scope rules for variables that occur in funs are as follows:</p><ul><li>All variables that occur in the head of a fun are assumed to be &quot;fresh&quot;
│ │ │  variables.</li><li>Variables that are defined before the fun, and that occur in function calls or
│ │ │ -guard tests within the fun, have the values they had outside the fun.</li><li>Variables cannot be exported from a fun.</li></ul><p>The following examples illustrate these rules:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="9456672656-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9456672656-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9456672656-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Stream</span><span class="p" data-group-id="9456672656-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="9456672656-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">write</span><span class="p" data-group-id="9456672656-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="9456672656-4">(</span><span class="nf">fun</span><span class="p" data-group-id="9456672656-5">(</span><span class="n">X</span><span class="p" data-group-id="9456672656-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9456672656-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="9456672656-7">[</span><span class="n">X</span><span class="p" data-group-id="9456672656-7">]</span><span class="p" data-group-id="9456672656-6">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9456672656-4">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="9456672656-8">(</span><span class="n">Stream</span><span class="p" data-group-id="9456672656-8">)</span><span class="p">.</span></code></pre><p>Here, the variable <code class="inline">X</code>, defined in the head of the fun, is a new variable. The
│ │ │ +guard tests within the fun, have the values they had outside the fun.</li><li>Variables cannot be exported from a fun.</li></ul><p>The following examples illustrate these rules:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="1248469459-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="1248469459-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1248469459-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Stream</span><span class="p" data-group-id="1248469459-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="1248469459-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">write</span><span class="p" data-group-id="1248469459-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="1248469459-4">(</span><span class="nf">fun</span><span class="p" data-group-id="1248469459-5">(</span><span class="n">X</span><span class="p" data-group-id="1248469459-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1248469459-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="1248469459-7">[</span><span class="n">X</span><span class="p" data-group-id="1248469459-7">]</span><span class="p" data-group-id="1248469459-6">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="1248469459-4">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="1248469459-8">(</span><span class="n">Stream</span><span class="p" data-group-id="1248469459-8">)</span><span class="p">.</span></code></pre><p>Here, the variable <code class="inline">X</code>, defined in the head of the fun, is a new variable. The
│ │ │  variable <code class="inline">Stream</code>, which is used within the fun, gets its value from the
│ │ │  <code class="inline">file:open</code> line.</p><p>As any variable that occurs in the head of a fun is considered a new variable,
│ │ │ -it is equally valid to write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="6073874711-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="6073874711-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6073874711-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Stream</span><span class="p" data-group-id="6073874711-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="6073874711-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">write</span><span class="p" data-group-id="6073874711-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="6073874711-4">(</span><span class="nf">fun</span><span class="p" data-group-id="6073874711-5">(</span><span class="n">File</span><span class="p" data-group-id="6073874711-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6073874711-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="6073874711-7">[</span><span class="n">File</span><span class="p" data-group-id="6073874711-7">]</span><span class="p" data-group-id="6073874711-6">)</span><span class="w">
│ │ │ -            </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="6073874711-4">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="6073874711-8">(</span><span class="n">Stream</span><span class="p" data-group-id="6073874711-8">)</span><span class="p">.</span></code></pre><p>Here, <code class="inline">File</code> is used as the new variable instead of <code class="inline">X</code>. This is not so wise
│ │ │ +it is equally valid to write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="9324996343-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9324996343-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9324996343-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Stream</span><span class="p" data-group-id="9324996343-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="9324996343-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">write</span><span class="p" data-group-id="9324996343-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="9324996343-4">(</span><span class="nf">fun</span><span class="p" data-group-id="9324996343-5">(</span><span class="n">File</span><span class="p" data-group-id="9324996343-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9324996343-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="9324996343-7">[</span><span class="n">File</span><span class="p" data-group-id="9324996343-7">]</span><span class="p" data-group-id="9324996343-6">)</span><span class="w">
│ │ │ +            </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9324996343-4">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="9324996343-8">(</span><span class="n">Stream</span><span class="p" data-group-id="9324996343-8">)</span><span class="p">.</span></code></pre><p>Here, <code class="inline">File</code> is used as the new variable instead of <code class="inline">X</code>. This is not so wise
│ │ │  because code in the fun body cannot refer to the variable <code class="inline">File</code>, which is
│ │ │  defined outside of the fun. Compiling this example gives the following
│ │ │  diagnostic:</p><pre><code class="text">./FileName.erl:Line: Warning: variable 'File'
│ │ │        shadowed in 'fun'</code></pre><p>This indicates that the variable <code class="inline">File</code>, which is defined inside the fun,
│ │ │  collides with the variable <code class="inline">File</code>, which is defined outside the fun.</p><p>The rules for importing variables into a fun have the consequence that certain
│ │ │  pattern matching operations must be moved into guard expressions and cannot be
│ │ │  written in the head of the fun. For example, you might write the following code
│ │ │  if you intend the first clause of <code class="inline">F</code> to be evaluated when the value of its
│ │ │ -argument is <code class="inline">Y</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="3656951049-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3656951049-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +argument is <code class="inline">Y</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="4037780741-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4037780741-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="nf">map</span><span class="p" data-group-id="3656951049-2">(</span><span class="nf">fun</span><span class="p" data-group-id="3656951049-3">(</span><span class="n">X</span><span class="p" data-group-id="3656951049-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">map</span><span class="p" data-group-id="4037780741-2">(</span><span class="nf">fun</span><span class="p" data-group-id="4037780741-3">(</span><span class="n">X</span><span class="p" data-group-id="4037780741-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │               </span><span class="p">;</span><span class="w">
│ │ │ -           </span><span class="p" data-group-id="3656951049-4">(</span><span class="p">_</span><span class="p" data-group-id="3656951049-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +           </span><span class="p" data-group-id="4037780741-4">(</span><span class="p">_</span><span class="p" data-group-id="4037780741-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │               </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -        </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3656951049-2">)</span><span class="w">
│ │ │ -    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>instead of writing the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="2961395013-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2961395013-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4037780741-2">)</span><span class="w">
│ │ │ +    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>instead of writing the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="8756166613-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8756166613-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="nf">map</span><span class="p" data-group-id="2961395013-2">(</span><span class="nf">fun</span><span class="p" data-group-id="2961395013-3">(</span><span class="n">Y</span><span class="p" data-group-id="2961395013-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">map</span><span class="p" data-group-id="8756166613-2">(</span><span class="nf">fun</span><span class="p" data-group-id="8756166613-3">(</span><span class="n">Y</span><span class="p" data-group-id="8756166613-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │               </span><span class="p">;</span><span class="w">
│ │ │ -           </span><span class="p" data-group-id="2961395013-4">(</span><span class="p">_</span><span class="p" data-group-id="2961395013-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +           </span><span class="p" data-group-id="8756166613-4">(</span><span class="p">_</span><span class="p" data-group-id="8756166613-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │               </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -        </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2961395013-2">)</span><span class="w">
│ │ │ +        </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8756166613-2">)</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="funs-and-module-lists" class="section-heading">
│ │ │    <a href="#funs-and-module-lists" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Funs and Module Lists</span>
│ │ │  </h2>
│ │ │  <p>The following examples show a dialogue with the Erlang shell. All the higher
│ │ │  order functions discussed are exported from the module <a href="../../lib/stdlib-8.0/doc/html/lists.html"><code class="inline">lists</code></a>.</p><h3 id="map-1" class="section-heading">
│ │ │    <a href="#map-1" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">map</span>
│ │ │  </h3>
│ │ │ -<p><a href="../../lib/stdlib-8.0/doc/html/lists.html#map/2"><code class="inline">lists:map/2</code></a> takes a function of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">map</span><span class="p" data-group-id="6553974385-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6553974385-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6553974385-2">]</span><span class="p" data-group-id="6553974385-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6553974385-3">[</span><span class="n">F</span><span class="p" data-group-id="6553974385-4">(</span><span class="n">H</span><span class="p" data-group-id="6553974385-4">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="6553974385-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="6553974385-5">)</span><span class="p" data-group-id="6553974385-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="6553974385-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6553974385-7">[</span><span class="p" data-group-id="6553974385-7">]</span><span class="p" data-group-id="6553974385-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6553974385-8">[</span><span class="p" data-group-id="6553974385-8">]</span><span class="p">.</span></code></pre><p>It returns the list obtained by applying the function to every argument in the
│ │ │ +<p><a href="../../lib/stdlib-8.0/doc/html/lists.html#map/2"><code class="inline">lists:map/2</code></a> takes a function of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">map</span><span class="p" data-group-id="5743997005-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5743997005-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5743997005-2">]</span><span class="p" data-group-id="5743997005-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5743997005-3">[</span><span class="n">F</span><span class="p" data-group-id="5743997005-4">(</span><span class="n">H</span><span class="p" data-group-id="5743997005-4">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="5743997005-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="5743997005-5">)</span><span class="p" data-group-id="5743997005-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="5743997005-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5743997005-7">[</span><span class="p" data-group-id="5743997005-7">]</span><span class="p" data-group-id="5743997005-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5743997005-8">[</span><span class="p" data-group-id="5743997005-8">]</span><span class="p">.</span></code></pre><p>It returns the list obtained by applying the function to every argument in the
│ │ │  list.</p><p>When a new fun is defined in the shell, the value of the fun is printed as
│ │ │ -<code class="inline">Fun#&lt;erl_eval&gt;</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Double</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3476521919-1">(</span><span class="n">X</span><span class="p" data-group-id="3476521919-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">Fun#&lt;erl_eval&gt;</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Double</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="2111516808-1">(</span><span class="n">X</span><span class="p" data-group-id="2111516808-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="3476521919-2">(</span><span class="n">Double</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3476521919-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="3476521919-3">]</span><span class="p" data-group-id="3476521919-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3476521919-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="3476521919-4">]</span></code></pre><h3 id="any" class="section-heading">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="2111516808-2">(</span><span class="n">Double</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2111516808-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="2111516808-3">]</span><span class="p" data-group-id="2111516808-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2111516808-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="2111516808-4">]</span></code></pre><h3 id="any" class="section-heading">
│ │ │    <a href="#any" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">any</span>
│ │ │  </h3>
│ │ │ -<p><a href="../../lib/stdlib-8.0/doc/html/lists.html#any/2"><code class="inline">lists:any/2</code></a> takes a predicate <code class="inline">P</code> of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">any</span><span class="p" data-group-id="0106707847-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0106707847-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0106707847-2">]</span><span class="p" data-group-id="0106707847-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="0106707847-3">(</span><span class="n">H</span><span class="p" data-group-id="0106707847-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +<p><a href="../../lib/stdlib-8.0/doc/html/lists.html#any/2"><code class="inline">lists:any/2</code></a> takes a predicate <code class="inline">P</code> of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">any</span><span class="p" data-group-id="6604918857-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6604918857-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6604918857-2">]</span><span class="p" data-group-id="6604918857-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="6604918857-3">(</span><span class="n">H</span><span class="p" data-group-id="6604918857-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">  </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="nf">any</span><span class="p" data-group-id="0106707847-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="0106707847-4">)</span><span class="w">
│ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="nf">any</span><span class="p" data-group-id="6604918857-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="6604918857-4">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">any</span><span class="p" data-group-id="0106707847-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0106707847-6">[</span><span class="p" data-group-id="0106707847-6">]</span><span class="p" data-group-id="0106707847-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">any</span><span class="p" data-group-id="6604918857-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6604918857-6">[</span><span class="p" data-group-id="6604918857-6">]</span><span class="p" data-group-id="6604918857-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">false</span><span class="p">.</span></code></pre><p>A predicate is a function that returns <code class="inline">true</code> or <code class="inline">false</code>. <code class="inline">any</code> is <code class="inline">true</code> if
│ │ │  there is a term <code class="inline">X</code> in the list such that <code class="inline">P(X)</code> is <code class="inline">true</code>.</p><p>A predicate <code class="inline">Big(X)</code> is defined, which is <code class="inline">true</code> if its argument is greater than
│ │ │ -10:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Big</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="nf">fun</span><span class="p" data-group-id="6153437218-1">(</span><span class="n">X</span><span class="p" data-group-id="6153437218-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">10</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">true</span><span class="p">;</span><span class="w"> </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">false</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +10:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Big</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="nf">fun</span><span class="p" data-group-id="4212040703-1">(</span><span class="n">X</span><span class="p" data-group-id="4212040703-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">10</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">true</span><span class="p">;</span><span class="w"> </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">false</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">any</span><span class="p" data-group-id="6153437218-2">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6153437218-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6153437218-3">]</span><span class="p" data-group-id="6153437218-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">any</span><span class="p" data-group-id="4212040703-2">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4212040703-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4212040703-3">]</span><span class="p" data-group-id="4212040703-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">any</span><span class="p" data-group-id="6153437218-4">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6153437218-5">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="6153437218-5">]</span><span class="p" data-group-id="6153437218-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">any</span><span class="p" data-group-id="4212040703-4">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4212040703-5">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="4212040703-5">]</span><span class="p" data-group-id="4212040703-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span></code></pre><h3 id="all" class="section-heading">
│ │ │    <a href="#all" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">all</span>
│ │ │  </h3>
│ │ │ -<p><a href="../../lib/stdlib-8.0/doc/html/lists.html#all/2"><code class="inline">lists:all/2</code></a> has the same arguments as <code class="inline">any</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">all</span><span class="p" data-group-id="3213911890-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3213911890-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3213911890-2">]</span><span class="p" data-group-id="3213911890-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="3213911890-3">(</span><span class="n">H</span><span class="p" data-group-id="3213911890-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">  </span><span class="nf">all</span><span class="p" data-group-id="3213911890-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="3213911890-4">)</span><span class="p">;</span><span class="w">
│ │ │ +<p><a href="../../lib/stdlib-8.0/doc/html/lists.html#all/2"><code class="inline">lists:all/2</code></a> has the same arguments as <code class="inline">any</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">all</span><span class="p" data-group-id="3556434211-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3556434211-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3556434211-2">]</span><span class="p" data-group-id="3556434211-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="3556434211-3">(</span><span class="n">H</span><span class="p" data-group-id="3556434211-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">  </span><span class="nf">all</span><span class="p" data-group-id="3556434211-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="3556434211-4">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="ss">false</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">all</span><span class="p" data-group-id="3213911890-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3213911890-6">[</span><span class="p" data-group-id="3213911890-6">]</span><span class="p" data-group-id="3213911890-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">true</span><span class="p">.</span></code></pre><p>It is <code class="inline">true</code> if the predicate applied to all elements in the list is <code class="inline">true</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">all</span><span class="p" data-group-id="1056843215-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1056843215-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="1056843215-2">]</span><span class="p" data-group-id="1056843215-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">all</span><span class="p" data-group-id="3556434211-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3556434211-6">[</span><span class="p" data-group-id="3556434211-6">]</span><span class="p" data-group-id="3556434211-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">true</span><span class="p">.</span></code></pre><p>It is <code class="inline">true</code> if the predicate applied to all elements in the list is <code class="inline">true</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">all</span><span class="p" data-group-id="2770511889-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2770511889-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2770511889-2">]</span><span class="p" data-group-id="2770511889-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">all</span><span class="p" data-group-id="1056843215-3">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1056843215-4">[</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p">,</span><span class="mi">14</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="1056843215-4">]</span><span class="p" data-group-id="1056843215-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">all</span><span class="p" data-group-id="2770511889-3">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2770511889-4">[</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p">,</span><span class="mi">14</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="2770511889-4">]</span><span class="p" data-group-id="2770511889-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span></code></pre><h3 id="foreach-1" class="section-heading">
│ │ │    <a href="#foreach-1" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">foreach</span>
│ │ │  </h3>
│ │ │ -<p><a href="../../lib/stdlib-8.0/doc/html/lists.html#foreach/2"><code class="inline">lists:foreach/2</code></a> takes a function of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="2125654281-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2125654281-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2125654281-2">]</span><span class="p" data-group-id="2125654281-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">F</span><span class="p" data-group-id="2125654281-3">(</span><span class="n">H</span><span class="p" data-group-id="2125654281-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="2125654281-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="2125654281-4">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">foreach</span><span class="p" data-group-id="2125654281-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2125654281-6">[</span><span class="p" data-group-id="2125654281-6">]</span><span class="p" data-group-id="2125654281-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +<p><a href="../../lib/stdlib-8.0/doc/html/lists.html#foreach/2"><code class="inline">lists:foreach/2</code></a> takes a function of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="1432473916-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1432473916-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1432473916-2">]</span><span class="p" data-group-id="1432473916-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">F</span><span class="p" data-group-id="1432473916-3">(</span><span class="n">H</span><span class="p" data-group-id="1432473916-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="1432473916-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="1432473916-4">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">foreach</span><span class="p" data-group-id="1432473916-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1432473916-6">[</span><span class="p" data-group-id="1432473916-6">]</span><span class="p" data-group-id="1432473916-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The function is applied to each argument in the list. <code class="inline">foreach</code> returns <code class="inline">ok</code>. It
│ │ │ -is only used for its side-effect:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="6875248253-1">(</span><span class="nf">fun</span><span class="p" data-group-id="6875248253-2">(</span><span class="n">X</span><span class="p" data-group-id="6875248253-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6875248253-3">(</span><span class="s">&quot;</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="6875248253-4">[</span><span class="n">X</span><span class="p" data-group-id="6875248253-4">]</span><span class="p" data-group-id="6875248253-3">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6875248253-5">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6875248253-5">]</span><span class="p" data-group-id="6875248253-1">)</span><span class="p">.</span><span class="w">
│ │ │ +is only used for its side-effect:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="2513275475-1">(</span><span class="nf">fun</span><span class="p" data-group-id="2513275475-2">(</span><span class="n">X</span><span class="p" data-group-id="2513275475-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2513275475-3">(</span><span class="s">&quot;</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="2513275475-4">[</span><span class="n">X</span><span class="p" data-group-id="2513275475-4">]</span><span class="p" data-group-id="2513275475-3">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2513275475-5">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="2513275475-5">]</span><span class="p" data-group-id="2513275475-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">1</span><span class="w">
│ │ │  </span><span class="mi">2</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="w">
│ │ │  </span><span class="mi">4</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><h3 id="foldl" class="section-heading">
│ │ │    <a href="#foldl" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">foldl</span>
│ │ │  </h3>
│ │ │ -<p><a href="../../lib/stdlib-8.0/doc/html/lists.html#foldl/3"><code class="inline">lists:foldl/3</code></a> takes a function of two arguments, an accumulator and a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foldl</span><span class="p" data-group-id="0410630291-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0410630291-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="0410630291-2">]</span><span class="p" data-group-id="0410630291-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">foldl</span><span class="p" data-group-id="0410630291-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="0410630291-4">(</span><span class="n">Hd</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p" data-group-id="0410630291-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="0410630291-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">foldl</span><span class="p" data-group-id="0410630291-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0410630291-6">[</span><span class="p" data-group-id="0410630291-6">]</span><span class="p" data-group-id="0410630291-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Accu</span><span class="p">.</span></code></pre><p>The function is called with two arguments. The first argument is the successive
│ │ │ +<p><a href="../../lib/stdlib-8.0/doc/html/lists.html#foldl/3"><code class="inline">lists:foldl/3</code></a> takes a function of two arguments, an accumulator and a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foldl</span><span class="p" data-group-id="2375241254-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2375241254-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="2375241254-2">]</span><span class="p" data-group-id="2375241254-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">foldl</span><span class="p" data-group-id="2375241254-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="2375241254-4">(</span><span class="n">Hd</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p" data-group-id="2375241254-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="2375241254-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">foldl</span><span class="p" data-group-id="2375241254-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2375241254-6">[</span><span class="p" data-group-id="2375241254-6">]</span><span class="p" data-group-id="2375241254-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Accu</span><span class="p">.</span></code></pre><p>The function is called with two arguments. The first argument is the successive
│ │ │  elements in the list. The second argument is the accumulator. The function must
│ │ │  return a new accumulator, which is used the next time the function is called.</p><p>If you have a list of lists <code class="inline">L = [&quot;I&quot;,&quot;like&quot;,&quot;Erlang&quot;]</code>, then you can sum the
│ │ │ -lengths of all the strings in <code class="inline">L</code> as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0754879057-1">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="0754879057-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0754879057-2">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="0754879057-2">]</span><span class="w">
│ │ │ -</span><span class="gp unselectable">10&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="0754879057-3">(</span><span class="nf">fun</span><span class="p" data-group-id="0754879057-4">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="0754879057-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="0754879057-5">(</span><span class="n">X</span><span class="p" data-group-id="0754879057-5">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0754879057-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">11</span></code></pre><p><a href="../../lib/stdlib-8.0/doc/html/lists.html#foldl/3"><code class="inline">lists:foldl/3</code></a> works like a <code class="inline">while</code> loop in an imperative language:</p><pre><code class="makeup erlang" translate="no"><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="p" data-group-id="4049253558-1">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="4049253558-1">]</span><span class="p">,</span><span class="w">
│ │ │ +lengths of all the strings in <code class="inline">L</code> as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6207860087-1">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="6207860087-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6207860087-2">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="6207860087-2">]</span><span class="w">
│ │ │ +</span><span class="gp unselectable">10&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="6207860087-3">(</span><span class="nf">fun</span><span class="p" data-group-id="6207860087-4">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="6207860087-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="6207860087-5">(</span><span class="n">X</span><span class="p" data-group-id="6207860087-5">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="6207860087-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">11</span></code></pre><p><a href="../../lib/stdlib-8.0/doc/html/lists.html#foldl/3"><code class="inline">lists:foldl/3</code></a> works like a <code class="inline">while</code> loop in an imperative language:</p><pre><code class="makeup erlang" translate="no"><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="p" data-group-id="3136157778-1">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="3136157778-1">]</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="n">Sum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">while</span><span class="p" data-group-id="4049253558-2">(</span><span class="w"> </span><span class="n">L</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4049253558-3">[</span><span class="p" data-group-id="4049253558-3">]</span><span class="p" data-group-id="4049253558-2">)</span><span class="p" data-group-id="4049253558-4">{</span><span class="w">
│ │ │ -    </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="4049253558-5">(</span><span class="nf">head</span><span class="p" data-group-id="4049253558-6">(</span><span class="n">L</span><span class="p" data-group-id="4049253558-6">)</span><span class="p" data-group-id="4049253558-5">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">tail</span><span class="p" data-group-id="4049253558-7">(</span><span class="n">L</span><span class="p" data-group-id="4049253558-7">)</span><span class="w">
│ │ │ +</span><span class="nf">while</span><span class="p" data-group-id="3136157778-2">(</span><span class="w"> </span><span class="n">L</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3136157778-3">[</span><span class="p" data-group-id="3136157778-3">]</span><span class="p" data-group-id="3136157778-2">)</span><span class="p" data-group-id="3136157778-4">{</span><span class="w">
│ │ │ +    </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="3136157778-5">(</span><span class="nf">head</span><span class="p" data-group-id="3136157778-6">(</span><span class="n">L</span><span class="p" data-group-id="3136157778-6">)</span><span class="p" data-group-id="3136157778-5">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">tail</span><span class="p" data-group-id="3136157778-7">(</span><span class="n">L</span><span class="p" data-group-id="3136157778-7">)</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><h3 id="mapfoldl" class="section-heading">
│ │ │    <a href="#mapfoldl" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">mapfoldl</span>
│ │ │  </h3>
│ │ │ -<p><a href="../../lib/stdlib-8.0/doc/html/lists.html#mapfoldl/3"><code class="inline">lists:mapfoldl/3</code></a> simultaneously maps and folds over a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">mapfoldl</span><span class="p" data-group-id="1984544689-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu0</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1984544689-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="1984544689-2">]</span><span class="p" data-group-id="1984544689-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1984544689-3">{</span><span class="n">R</span><span class="p">,</span><span class="n">Accu1</span><span class="p" data-group-id="1984544689-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="1984544689-4">(</span><span class="n">Hd</span><span class="p">,</span><span class="w"> </span><span class="n">Accu0</span><span class="p" data-group-id="1984544689-4">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1984544689-5">{</span><span class="n">Rs</span><span class="p">,</span><span class="n">Accu2</span><span class="p" data-group-id="1984544689-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">mapfoldl</span><span class="p" data-group-id="1984544689-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu1</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="1984544689-6">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1984544689-7">{</span><span class="p" data-group-id="1984544689-8">[</span><span class="n">R</span><span class="p">|</span><span class="n">Rs</span><span class="p" data-group-id="1984544689-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Accu2</span><span class="p" data-group-id="1984544689-7">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">mapfoldl</span><span class="p" data-group-id="1984544689-9">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1984544689-10">[</span><span class="p" data-group-id="1984544689-10">]</span><span class="p" data-group-id="1984544689-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1984544689-11">{</span><span class="p" data-group-id="1984544689-12">[</span><span class="p" data-group-id="1984544689-12">]</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p" data-group-id="1984544689-11">}</span><span class="p">.</span></code></pre><p>The following example shows how to change all letters in <code class="inline">L</code> to upper case and
│ │ │ -then count them.</p><p>First the change to upper case:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Upcase</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="nf">fun</span><span class="p" data-group-id="0531109763-1">(</span><span class="n">X</span><span class="p" data-group-id="0531109763-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$a</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w">  </span><span class="n">X</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">$A</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="sc">$a</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0531109763-2">(</span><span class="n">X</span><span class="p" data-group-id="0531109763-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w">
│ │ │ +<p><a href="../../lib/stdlib-8.0/doc/html/lists.html#mapfoldl/3"><code class="inline">lists:mapfoldl/3</code></a> simultaneously maps and folds over a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">mapfoldl</span><span class="p" data-group-id="3495490155-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu0</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3495490155-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="3495490155-2">]</span><span class="p" data-group-id="3495490155-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3495490155-3">{</span><span class="n">R</span><span class="p">,</span><span class="n">Accu1</span><span class="p" data-group-id="3495490155-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="3495490155-4">(</span><span class="n">Hd</span><span class="p">,</span><span class="w"> </span><span class="n">Accu0</span><span class="p" data-group-id="3495490155-4">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3495490155-5">{</span><span class="n">Rs</span><span class="p">,</span><span class="n">Accu2</span><span class="p" data-group-id="3495490155-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">mapfoldl</span><span class="p" data-group-id="3495490155-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu1</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="3495490155-6">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3495490155-7">{</span><span class="p" data-group-id="3495490155-8">[</span><span class="n">R</span><span class="p">|</span><span class="n">Rs</span><span class="p" data-group-id="3495490155-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Accu2</span><span class="p" data-group-id="3495490155-7">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">mapfoldl</span><span class="p" data-group-id="3495490155-9">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3495490155-10">[</span><span class="p" data-group-id="3495490155-10">]</span><span class="p" data-group-id="3495490155-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3495490155-11">{</span><span class="p" data-group-id="3495490155-12">[</span><span class="p" data-group-id="3495490155-12">]</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p" data-group-id="3495490155-11">}</span><span class="p">.</span></code></pre><p>The following example shows how to change all letters in <code class="inline">L</code> to upper case and
│ │ │ +then count them.</p><p>First the change to upper case:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Upcase</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="nf">fun</span><span class="p" data-group-id="4151630861-1">(</span><span class="n">X</span><span class="p" data-group-id="4151630861-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$a</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w">  </span><span class="n">X</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">$A</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="sc">$a</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4151630861-2">(</span><span class="n">X</span><span class="p" data-group-id="4151630861-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="gp unselectable">&gt; </span><span class="n">Upcase_word</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ -</span><span class="nf">fun</span><span class="p" data-group-id="0531109763-3">(</span><span class="n">X</span><span class="p" data-group-id="0531109763-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="0531109763-4">(</span><span class="n">Upcase</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0531109763-4">)</span><span class="w">
│ │ │ +</span><span class="nf">fun</span><span class="p" data-group-id="4151630861-3">(</span><span class="n">X</span><span class="p" data-group-id="4151630861-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="4151630861-4">(</span><span class="n">Upcase</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4151630861-4">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">Upcase_word</span><span class="p" data-group-id="0531109763-5">(</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="0531109763-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">Upcase_word</span><span class="p" data-group-id="4151630861-5">(</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="4151630861-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;ERLANG&quot;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="0531109763-6">(</span><span class="n">Upcase_word</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0531109763-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0531109763-7">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;LIKE&quot;</span><span class="p">,</span><span class="s">&quot;ERLANG&quot;</span><span class="p" data-group-id="0531109763-7">]</span></code></pre><p>Now, the fold and the map can be done at the same time:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">mapfoldl</span><span class="p" data-group-id="1439237255-1">(</span><span class="nf">fun</span><span class="p" data-group-id="1439237255-2">(</span><span class="n">Word</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="1439237255-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1439237255-3">{</span><span class="n">Upcase_word</span><span class="p" data-group-id="1439237255-4">(</span><span class="n">Word</span><span class="p" data-group-id="1439237255-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="1439237255-5">(</span><span class="n">Word</span><span class="p" data-group-id="1439237255-5">)</span><span class="p" data-group-id="1439237255-3">}</span><span class="w">
│ │ │ -</span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="1439237255-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1439237255-6">{</span><span class="p" data-group-id="1439237255-7">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;LIKE&quot;</span><span class="p">,</span><span class="s">&quot;ERLANG&quot;</span><span class="p" data-group-id="1439237255-7">]</span><span class="p">,</span><span class="mi">11</span><span class="p" data-group-id="1439237255-6">}</span></code></pre><h3 id="filter" class="section-heading">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="4151630861-6">(</span><span class="n">Upcase_word</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4151630861-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4151630861-7">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;LIKE&quot;</span><span class="p">,</span><span class="s">&quot;ERLANG&quot;</span><span class="p" data-group-id="4151630861-7">]</span></code></pre><p>Now, the fold and the map can be done at the same time:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">mapfoldl</span><span class="p" data-group-id="3608510350-1">(</span><span class="nf">fun</span><span class="p" data-group-id="3608510350-2">(</span><span class="n">Word</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="3608510350-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3608510350-3">{</span><span class="n">Upcase_word</span><span class="p" data-group-id="3608510350-4">(</span><span class="n">Word</span><span class="p" data-group-id="3608510350-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="3608510350-5">(</span><span class="n">Word</span><span class="p" data-group-id="3608510350-5">)</span><span class="p" data-group-id="3608510350-3">}</span><span class="w">
│ │ │ +</span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="3608510350-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3608510350-6">{</span><span class="p" data-group-id="3608510350-7">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;LIKE&quot;</span><span class="p">,</span><span class="s">&quot;ERLANG&quot;</span><span class="p" data-group-id="3608510350-7">]</span><span class="p">,</span><span class="mi">11</span><span class="p" data-group-id="3608510350-6">}</span></code></pre><h3 id="filter" class="section-heading">
│ │ │    <a href="#filter" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">filter</span>
│ │ │  </h3>
│ │ │  <p><a href="../../lib/stdlib-8.0/doc/html/lists.html#filter/2"><code class="inline">lists:filter/2</code></a> takes a predicate of one argument and a list and returns all elements
│ │ │ -in the list that satisfy the predicate:</p><pre><code class="makeup erlang" translate="no"><span class="nf">filter</span><span class="p" data-group-id="7507650103-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7507650103-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7507650103-2">]</span><span class="p" data-group-id="7507650103-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="7507650103-3">(</span><span class="n">H</span><span class="p" data-group-id="7507650103-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7507650103-4">[</span><span class="n">H</span><span class="p">|</span><span class="nf">filter</span><span class="p" data-group-id="7507650103-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7507650103-5">)</span><span class="p" data-group-id="7507650103-4">]</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">filter</span><span class="p" data-group-id="7507650103-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7507650103-6">)</span><span class="w">
│ │ │ +in the list that satisfy the predicate:</p><pre><code class="makeup erlang" translate="no"><span class="nf">filter</span><span class="p" data-group-id="3311323291-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3311323291-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3311323291-2">]</span><span class="p" data-group-id="3311323291-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="3311323291-3">(</span><span class="n">H</span><span class="p" data-group-id="3311323291-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3311323291-4">[</span><span class="n">H</span><span class="p">|</span><span class="nf">filter</span><span class="p" data-group-id="3311323291-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="3311323291-5">)</span><span class="p" data-group-id="3311323291-4">]</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">filter</span><span class="p" data-group-id="3311323291-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="3311323291-6">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">filter</span><span class="p" data-group-id="7507650103-7">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7507650103-8">[</span><span class="p" data-group-id="7507650103-8">]</span><span class="p" data-group-id="7507650103-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7507650103-9">[</span><span class="p" data-group-id="7507650103-9">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="0222101426-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0222101426-2">[</span><span class="mi">500</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="0222101426-2">]</span><span class="p" data-group-id="0222101426-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0222101426-3">[</span><span class="mi">500</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="0222101426-3">]</span></code></pre><p>Combining maps and filters enables writing of very succinct code. For example,
│ │ │ +</span><span class="nf">filter</span><span class="p" data-group-id="3311323291-7">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3311323291-8">[</span><span class="p" data-group-id="3311323291-8">]</span><span class="p" data-group-id="3311323291-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3311323291-9">[</span><span class="p" data-group-id="3311323291-9">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="9558367298-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9558367298-2">[</span><span class="mi">500</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="9558367298-2">]</span><span class="p" data-group-id="9558367298-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9558367298-3">[</span><span class="mi">500</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="9558367298-3">]</span></code></pre><p>Combining maps and filters enables writing of very succinct code. For example,
│ │ │  to define a set difference function <code class="inline">diff(L1, L2)</code> to be the difference between
│ │ │ -the lists <code class="inline">L1</code> and <code class="inline">L2</code>, the code can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">diff</span><span class="p" data-group-id="2571732138-1">(</span><span class="n">L1</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="2571732138-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">filter</span><span class="p" data-group-id="2571732138-2">(</span><span class="nf">fun</span><span class="p" data-group-id="2571732138-3">(</span><span class="n">X</span><span class="p" data-group-id="2571732138-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ow">not</span><span class="w"> </span><span class="nf">member</span><span class="p" data-group-id="2571732138-4">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="2571732138-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L1</span><span class="p" data-group-id="2571732138-2">)</span><span class="p">.</span></code></pre><p>This gives the list of all elements in L1 that are not contained in L2.</p><p>The AND intersection of the lists <code class="inline">L1</code> and <code class="inline">L2</code> is also easily defined:</p><pre><code class="makeup erlang" translate="no"><span class="nf">intersection</span><span class="p" data-group-id="6754946618-1">(</span><span class="n">L1</span><span class="p">,</span><span class="n">L2</span><span class="p" data-group-id="6754946618-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">filter</span><span class="p" data-group-id="6754946618-2">(</span><span class="nf">fun</span><span class="p" data-group-id="6754946618-3">(</span><span class="n">X</span><span class="p" data-group-id="6754946618-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">member</span><span class="p" data-group-id="6754946618-4">(</span><span class="n">X</span><span class="p">,</span><span class="n">L1</span><span class="p" data-group-id="6754946618-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="6754946618-2">)</span><span class="p">.</span></code></pre><h3 id="takewhile" class="section-heading">
│ │ │ +the lists <code class="inline">L1</code> and <code class="inline">L2</code>, the code can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">diff</span><span class="p" data-group-id="7408370318-1">(</span><span class="n">L1</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="7408370318-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">filter</span><span class="p" data-group-id="7408370318-2">(</span><span class="nf">fun</span><span class="p" data-group-id="7408370318-3">(</span><span class="n">X</span><span class="p" data-group-id="7408370318-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ow">not</span><span class="w"> </span><span class="nf">member</span><span class="p" data-group-id="7408370318-4">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="7408370318-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L1</span><span class="p" data-group-id="7408370318-2">)</span><span class="p">.</span></code></pre><p>This gives the list of all elements in L1 that are not contained in L2.</p><p>The AND intersection of the lists <code class="inline">L1</code> and <code class="inline">L2</code> is also easily defined:</p><pre><code class="makeup erlang" translate="no"><span class="nf">intersection</span><span class="p" data-group-id="9970273703-1">(</span><span class="n">L1</span><span class="p">,</span><span class="n">L2</span><span class="p" data-group-id="9970273703-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">filter</span><span class="p" data-group-id="9970273703-2">(</span><span class="nf">fun</span><span class="p" data-group-id="9970273703-3">(</span><span class="n">X</span><span class="p" data-group-id="9970273703-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">member</span><span class="p" data-group-id="9970273703-4">(</span><span class="n">X</span><span class="p">,</span><span class="n">L1</span><span class="p" data-group-id="9970273703-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="9970273703-2">)</span><span class="p">.</span></code></pre><h3 id="takewhile" class="section-heading">
│ │ │    <a href="#takewhile" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">takewhile</span>
│ │ │  </h3>
│ │ │  <p><a href="../../lib/stdlib-8.0/doc/html/lists.html#takewhile/2"><code class="inline">lists:takewhile/2</code></a> takes elements <code class="inline">X</code> from a list <code class="inline">L</code> as long as the predicate
│ │ │ -<code class="inline">P(X)</code> is true:</p><pre><code class="makeup erlang" translate="no"><span class="nf">takewhile</span><span class="p" data-group-id="5296161128-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5296161128-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5296161128-2">]</span><span class="p" data-group-id="5296161128-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="5296161128-3">(</span><span class="n">H</span><span class="p" data-group-id="5296161128-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5296161128-4">[</span><span class="n">H</span><span class="p">|</span><span class="nf">takewhile</span><span class="p" data-group-id="5296161128-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="5296161128-5">)</span><span class="p" data-group-id="5296161128-4">]</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5296161128-6">[</span><span class="p" data-group-id="5296161128-6">]</span><span class="w">
│ │ │ +<code class="inline">P(X)</code> is true:</p><pre><code class="makeup erlang" translate="no"><span class="nf">takewhile</span><span class="p" data-group-id="2792292853-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2792292853-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2792292853-2">]</span><span class="p" data-group-id="2792292853-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="2792292853-3">(</span><span class="n">H</span><span class="p" data-group-id="2792292853-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2792292853-4">[</span><span class="n">H</span><span class="p">|</span><span class="nf">takewhile</span><span class="p" data-group-id="2792292853-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="2792292853-5">)</span><span class="p" data-group-id="2792292853-4">]</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2792292853-6">[</span><span class="p" data-group-id="2792292853-6">]</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">takewhile</span><span class="p" data-group-id="5296161128-7">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5296161128-8">[</span><span class="p" data-group-id="5296161128-8">]</span><span class="p" data-group-id="5296161128-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5296161128-9">[</span><span class="p" data-group-id="5296161128-9">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">takewhile</span><span class="p" data-group-id="4001796001-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4001796001-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="4001796001-2">]</span><span class="p" data-group-id="4001796001-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4001796001-3">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="4001796001-3">]</span></code></pre><h3 id="dropwhile" class="section-heading">
│ │ │ +</span><span class="nf">takewhile</span><span class="p" data-group-id="2792292853-7">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2792292853-8">[</span><span class="p" data-group-id="2792292853-8">]</span><span class="p" data-group-id="2792292853-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2792292853-9">[</span><span class="p" data-group-id="2792292853-9">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">takewhile</span><span class="p" data-group-id="5256657377-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5256657377-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="5256657377-2">]</span><span class="p" data-group-id="5256657377-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5256657377-3">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="5256657377-3">]</span></code></pre><h3 id="dropwhile" class="section-heading">
│ │ │    <a href="#dropwhile" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">dropwhile</span>
│ │ │  </h3>
│ │ │ -<p><a href="../../lib/stdlib-8.0/doc/html/lists.html#dropwhile/2"><code class="inline">lists:dropwhile/2</code></a> is the complement of <code class="inline">takewhile</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">dropwhile</span><span class="p" data-group-id="3002027759-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3002027759-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3002027759-2">]</span><span class="p" data-group-id="3002027759-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="3002027759-3">(</span><span class="n">H</span><span class="p" data-group-id="3002027759-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">dropwhile</span><span class="p" data-group-id="3002027759-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="3002027759-4">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3002027759-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3002027759-5">]</span><span class="w">
│ │ │ +<p><a href="../../lib/stdlib-8.0/doc/html/lists.html#dropwhile/2"><code class="inline">lists:dropwhile/2</code></a> is the complement of <code class="inline">takewhile</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">dropwhile</span><span class="p" data-group-id="4084275578-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4084275578-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4084275578-2">]</span><span class="p" data-group-id="4084275578-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="4084275578-3">(</span><span class="n">H</span><span class="p" data-group-id="4084275578-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">dropwhile</span><span class="p" data-group-id="4084275578-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="4084275578-4">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4084275578-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4084275578-5">]</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">dropwhile</span><span class="p" data-group-id="3002027759-6">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3002027759-7">[</span><span class="p" data-group-id="3002027759-7">]</span><span class="p" data-group-id="3002027759-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3002027759-8">[</span><span class="p" data-group-id="3002027759-8">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">dropwhile</span><span class="p" data-group-id="8369804011-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8369804011-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8369804011-2">]</span><span class="p" data-group-id="8369804011-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8369804011-3">[</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8369804011-3">]</span></code></pre><h3 id="splitwith" class="section-heading">
│ │ │ +</span><span class="nf">dropwhile</span><span class="p" data-group-id="4084275578-6">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4084275578-7">[</span><span class="p" data-group-id="4084275578-7">]</span><span class="p" data-group-id="4084275578-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4084275578-8">[</span><span class="p" data-group-id="4084275578-8">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">dropwhile</span><span class="p" data-group-id="6281272383-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6281272383-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="6281272383-2">]</span><span class="p" data-group-id="6281272383-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6281272383-3">[</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="6281272383-3">]</span></code></pre><h3 id="splitwith" class="section-heading">
│ │ │    <a href="#splitwith" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">splitwith</span>
│ │ │  </h3>
│ │ │  <p><a href="../../lib/stdlib-8.0/doc/html/lists.html#splitwith/2"><code class="inline">lists:splitwith/2</code></a> splits the list <code class="inline">L</code> into the two sublists <code class="inline">{L1, L2}</code>, where
│ │ │ -<code class="inline">L1 = takewhile(P, L)</code> and <code class="inline">L2 = dropwhile(P, L)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">splitwith</span><span class="p" data-group-id="3544035035-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="3544035035-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">splitwith</span><span class="p" data-group-id="3544035035-2">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3544035035-3">[</span><span class="p" data-group-id="3544035035-3">]</span><span class="p" data-group-id="3544035035-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">L1 = takewhile(P, L)</code> and <code class="inline">L2 = dropwhile(P, L)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">splitwith</span><span class="p" data-group-id="2961805688-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="2961805688-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">splitwith</span><span class="p" data-group-id="2961805688-2">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2961805688-3">[</span><span class="p" data-group-id="2961805688-3">]</span><span class="p" data-group-id="2961805688-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">splitwith</span><span class="p" data-group-id="3544035035-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3544035035-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3544035035-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="3544035035-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="3544035035-6">(</span><span class="n">H</span><span class="p" data-group-id="3544035035-6">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">splitwith</span><span class="p" data-group-id="3544035035-7">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3544035035-8">[</span><span class="n">H</span><span class="p">|</span><span class="n">L</span><span class="p" data-group-id="3544035035-8">]</span><span class="p" data-group-id="3544035035-7">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3544035035-9">{</span><span class="nf">reverse</span><span class="p" data-group-id="3544035035-10">(</span><span class="n">L</span><span class="p" data-group-id="3544035035-10">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3544035035-11">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3544035035-11">]</span><span class="p" data-group-id="3544035035-9">}</span><span class="w">
│ │ │ +</span><span class="nf">splitwith</span><span class="p" data-group-id="2961805688-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2961805688-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2961805688-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="2961805688-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="2961805688-6">(</span><span class="n">H</span><span class="p" data-group-id="2961805688-6">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">splitwith</span><span class="p" data-group-id="2961805688-7">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2961805688-8">[</span><span class="n">H</span><span class="p">|</span><span class="n">L</span><span class="p" data-group-id="2961805688-8">]</span><span class="p" data-group-id="2961805688-7">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2961805688-9">{</span><span class="nf">reverse</span><span class="p" data-group-id="2961805688-10">(</span><span class="n">L</span><span class="p" data-group-id="2961805688-10">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2961805688-11">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2961805688-11">]</span><span class="p" data-group-id="2961805688-9">}</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">splitwith</span><span class="p" data-group-id="3544035035-12">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3544035035-13">[</span><span class="p" data-group-id="3544035035-13">]</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="3544035035-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3544035035-14">{</span><span class="nf">reverse</span><span class="p" data-group-id="3544035035-15">(</span><span class="n">L</span><span class="p" data-group-id="3544035035-15">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3544035035-16">[</span><span class="p" data-group-id="3544035035-16">]</span><span class="p" data-group-id="3544035035-14">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">splitwith</span><span class="p" data-group-id="0325785669-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0325785669-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="0325785669-2">]</span><span class="p" data-group-id="0325785669-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0325785669-3">{</span><span class="p" data-group-id="0325785669-4">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="0325785669-4">]</span><span class="p">,</span><span class="p" data-group-id="0325785669-5">[</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="0325785669-5">]</span><span class="p" data-group-id="0325785669-3">}</span></code></pre><h2 id="funs-returning-funs" class="section-heading">
│ │ │ +</span><span class="nf">splitwith</span><span class="p" data-group-id="2961805688-12">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2961805688-13">[</span><span class="p" data-group-id="2961805688-13">]</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="2961805688-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2961805688-14">{</span><span class="nf">reverse</span><span class="p" data-group-id="2961805688-15">(</span><span class="n">L</span><span class="p" data-group-id="2961805688-15">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2961805688-16">[</span><span class="p" data-group-id="2961805688-16">]</span><span class="p" data-group-id="2961805688-14">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">splitwith</span><span class="p" data-group-id="2825569372-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2825569372-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2825569372-2">]</span><span class="p" data-group-id="2825569372-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2825569372-3">{</span><span class="p" data-group-id="2825569372-4">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="2825569372-4">]</span><span class="p">,</span><span class="p" data-group-id="2825569372-5">[</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2825569372-5">]</span><span class="p" data-group-id="2825569372-3">}</span></code></pre><h2 id="funs-returning-funs" class="section-heading">
│ │ │    <a href="#funs-returning-funs" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Funs Returning Funs</span>
│ │ │  </h2>
│ │ │  <p>So far, only functions that take funs as arguments have been described. More
│ │ │  powerful functions, that themselves return funs, can also be written. The
│ │ │  following examples illustrate these types of functions.</p><h3 id="simple-higher-order-functions" class="section-heading">
│ │ │    <a href="#simple-higher-order-functions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Simple Higher Order Functions</span>
│ │ │  </h3>
│ │ │  <p><code class="inline">Adder(X)</code> is a function that given <code class="inline">X</code>, returns a new function <code class="inline">G</code> such that
│ │ │ -<code class="inline">G(K)</code> returns <code class="inline">K + X</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Adder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0694409118-1">(</span><span class="n">X</span><span class="p" data-group-id="0694409118-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0694409118-2">(</span><span class="n">Y</span><span class="p" data-group-id="0694409118-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">G(K)</code> returns <code class="inline">K + X</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Adder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="5749983997-1">(</span><span class="n">X</span><span class="p" data-group-id="5749983997-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="5749983997-2">(</span><span class="n">Y</span><span class="p" data-group-id="5749983997-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">Add6</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Adder</span><span class="p" data-group-id="0694409118-3">(</span><span class="mi">6</span><span class="p" data-group-id="0694409118-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">Add6</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Adder</span><span class="p" data-group-id="5749983997-3">(</span><span class="mi">6</span><span class="p" data-group-id="5749983997-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">Add6</span><span class="p" data-group-id="0694409118-4">(</span><span class="mi">10</span><span class="p" data-group-id="0694409118-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">Add6</span><span class="p" data-group-id="5749983997-4">(</span><span class="mi">10</span><span class="p" data-group-id="5749983997-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">16</span></code></pre><h3 id="infinite-lists" class="section-heading">
│ │ │    <a href="#infinite-lists" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Infinite Lists</span>
│ │ │  </h3>
│ │ │ -<p>The idea is to write something like:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4232767107-1">(</span><span class="ss">lazy</span><span class="p" data-group-id="4232767107-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4232767107-2">(</span><span class="p" data-group-id="4232767107-3">[</span><span class="ss">ints_from</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4232767107-3">]</span><span class="p" data-group-id="4232767107-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">ints_from</span><span class="p" data-group-id="4232767107-4">(</span><span class="n">N</span><span class="p" data-group-id="4232767107-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">fun</span><span class="p" data-group-id="4232767107-5">(</span><span class="p" data-group-id="4232767107-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="4232767107-6">[</span><span class="n">N</span><span class="p">|</span><span class="nf">ints_from</span><span class="p" data-group-id="4232767107-7">(</span><span class="n">N</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="4232767107-7">)</span><span class="p" data-group-id="4232767107-6">]</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Then proceed as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">XX</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lazy</span><span class="p">:</span><span class="nf">ints_from</span><span class="p" data-group-id="0718511131-1">(</span><span class="mi">1</span><span class="p" data-group-id="0718511131-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>The idea is to write something like:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6049701465-1">(</span><span class="ss">lazy</span><span class="p" data-group-id="6049701465-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6049701465-2">(</span><span class="p" data-group-id="6049701465-3">[</span><span class="ss">ints_from</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6049701465-3">]</span><span class="p" data-group-id="6049701465-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">ints_from</span><span class="p" data-group-id="6049701465-4">(</span><span class="n">N</span><span class="p" data-group-id="6049701465-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">fun</span><span class="p" data-group-id="6049701465-5">(</span><span class="p" data-group-id="6049701465-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="6049701465-6">[</span><span class="n">N</span><span class="p">|</span><span class="nf">ints_from</span><span class="p" data-group-id="6049701465-7">(</span><span class="n">N</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="6049701465-7">)</span><span class="p" data-group-id="6049701465-6">]</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Then proceed as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">XX</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lazy</span><span class="p">:</span><span class="nf">ints_from</span><span class="p" data-group-id="6325166562-1">(</span><span class="mi">1</span><span class="p" data-group-id="6325166562-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">lazy</span><span class="p">.</span><span class="mf">0.29874839</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">XX</span><span class="p" data-group-id="0718511131-2">(</span><span class="p" data-group-id="0718511131-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0718511131-3">[</span><span class="mi">1</span><span class="p">|</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">lazy</span><span class="p">.</span><span class="mf">0.29874839</span><span class="o">&gt;</span><span class="p" data-group-id="0718511131-3">]</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nf">hd</span><span class="p" data-group-id="0718511131-4">(</span><span class="n">XX</span><span class="p" data-group-id="0718511131-5">(</span><span class="p" data-group-id="0718511131-5">)</span><span class="p" data-group-id="0718511131-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">XX</span><span class="p" data-group-id="6325166562-2">(</span><span class="p" data-group-id="6325166562-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6325166562-3">[</span><span class="mi">1</span><span class="p">|</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">lazy</span><span class="p">.</span><span class="mf">0.29874839</span><span class="o">&gt;</span><span class="p" data-group-id="6325166562-3">]</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nf">hd</span><span class="p" data-group-id="6325166562-4">(</span><span class="n">XX</span><span class="p" data-group-id="6325166562-5">(</span><span class="p" data-group-id="6325166562-5">)</span><span class="p" data-group-id="6325166562-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">1</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">tl</span><span class="p" data-group-id="0718511131-6">(</span><span class="n">XX</span><span class="p" data-group-id="0718511131-7">(</span><span class="p" data-group-id="0718511131-7">)</span><span class="p" data-group-id="0718511131-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">tl</span><span class="p" data-group-id="6325166562-6">(</span><span class="n">XX</span><span class="p" data-group-id="6325166562-7">(</span><span class="p" data-group-id="6325166562-7">)</span><span class="p" data-group-id="6325166562-6">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">lazy</span><span class="p">.</span><span class="mf">0.29874839</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nf">hd</span><span class="p" data-group-id="0718511131-8">(</span><span class="n">Y</span><span class="p" data-group-id="0718511131-9">(</span><span class="p" data-group-id="0718511131-9">)</span><span class="p" data-group-id="0718511131-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nf">hd</span><span class="p" data-group-id="6325166562-8">(</span><span class="n">Y</span><span class="p" data-group-id="6325166562-9">(</span><span class="p" data-group-id="6325166562-9">)</span><span class="p" data-group-id="6325166562-8">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">2</span></code></pre><p>And so on. This is an example of &quot;lazy embedding&quot;.</p><h3 id="parsing" class="section-heading">
│ │ │    <a href="#parsing" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Parsing</span>
│ │ │  </h3>
│ │ │ -<p>The following examples show parsers of the following type:</p><pre><code class="makeup erlang" translate="no"><span class="n">Parser</span><span class="p" data-group-id="0947598157-1">(</span><span class="n">Toks</span><span class="p" data-group-id="0947598157-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0947598157-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Tree</span><span class="p">,</span><span class="w"> </span><span class="n">Toks1</span><span class="p" data-group-id="0947598157-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">fail</span></code></pre><p><code class="inline">Toks</code> is the list of tokens to be parsed. A successful parse returns
│ │ │ +<p>The following examples show parsers of the following type:</p><pre><code class="makeup erlang" translate="no"><span class="n">Parser</span><span class="p" data-group-id="9585712394-1">(</span><span class="n">Toks</span><span class="p" data-group-id="9585712394-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9585712394-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Tree</span><span class="p">,</span><span class="w"> </span><span class="n">Toks1</span><span class="p" data-group-id="9585712394-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">fail</span></code></pre><p><code class="inline">Toks</code> is the list of tokens to be parsed. A successful parse returns
│ │ │  <code class="inline">{ok, Tree, Toks1}</code>.</p><ul><li><code class="inline">Tree</code> is a parse tree.</li><li><code class="inline">Toks1</code> is a tail of <code class="inline">Toks</code> that contains symbols encountered after the
│ │ │  structure that was correctly parsed.</li></ul><p>An unsuccessful parse returns <code class="inline">fail</code>.</p><p>The following example illustrates a simple, functional parser that parses the
│ │ │  grammar:</p><pre><code class="text">(a | b) &amp; (c | d)</code></pre><p>The following code defines a function <code class="inline">pconst(X)</code> in the module <code class="inline">funparse</code>,
│ │ │ -which returns a fun that parses a list of tokens:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pconst</span><span class="p" data-group-id="1502778713-1">(</span><span class="n">X</span><span class="p" data-group-id="1502778713-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="1502778713-2">(</span><span class="n">T</span><span class="p" data-group-id="1502778713-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +which returns a fun that parses a list of tokens:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pconst</span><span class="p" data-group-id="7504075164-1">(</span><span class="n">X</span><span class="p" data-group-id="7504075164-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="7504075164-2">(</span><span class="n">T</span><span class="p" data-group-id="7504075164-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │         </span><span class="k">case</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -           </span><span class="p" data-group-id="1502778713-3">[</span><span class="n">X</span><span class="p">|</span><span class="n">T1</span><span class="p" data-group-id="1502778713-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1502778713-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1502778713-5">{</span><span class="ss">const</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1502778713-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="1502778713-4">}</span><span class="p">;</span><span class="w">
│ │ │ +           </span><span class="p" data-group-id="7504075164-3">[</span><span class="n">X</span><span class="p">|</span><span class="n">T1</span><span class="p" data-group-id="7504075164-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7504075164-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7504075164-5">{</span><span class="ss">const</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="7504075164-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="7504075164-4">}</span><span class="p">;</span><span class="w">
│ │ │             </span><span class="p">_</span><span class="w">      </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">fail</span><span class="w">
│ │ │         </span><span class="k">end</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>This function can be used as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">pconst</span><span class="p" data-group-id="0532374739-1">(</span><span class="ss">a</span><span class="p" data-group-id="0532374739-1">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>This function can be used as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">pconst</span><span class="p" data-group-id="7600522140-1">(</span><span class="ss">a</span><span class="p" data-group-id="7600522140-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">funparse</span><span class="p">.</span><span class="mf">0.22674075</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="p" data-group-id="0532374739-2">(</span><span class="p" data-group-id="0532374739-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="0532374739-3">]</span><span class="p" data-group-id="0532374739-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0532374739-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="0532374739-5">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="0532374739-5">}</span><span class="p">,</span><span class="p" data-group-id="0532374739-6">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="0532374739-6">]</span><span class="p" data-group-id="0532374739-4">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="p" data-group-id="0532374739-7">(</span><span class="p" data-group-id="0532374739-8">[</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="0532374739-8">]</span><span class="p" data-group-id="0532374739-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="p" data-group-id="7600522140-2">(</span><span class="p" data-group-id="7600522140-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="7600522140-3">]</span><span class="p" data-group-id="7600522140-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7600522140-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="7600522140-5">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="7600522140-5">}</span><span class="p">,</span><span class="p" data-group-id="7600522140-6">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="7600522140-6">]</span><span class="p" data-group-id="7600522140-4">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="p" data-group-id="7600522140-7">(</span><span class="p" data-group-id="7600522140-8">[</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="7600522140-8">]</span><span class="p" data-group-id="7600522140-7">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">fail</span></code></pre><p>Next, the two higher order functions <code class="inline">pand</code> and <code class="inline">por</code> are defined. They combine
│ │ │ -primitive parsers to produce more complex parsers.</p><p>First <code class="inline">pand</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pand</span><span class="p" data-group-id="9144700730-1">(</span><span class="n">P1</span><span class="p">,</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="9144700730-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="9144700730-2">(</span><span class="n">T</span><span class="p" data-group-id="9144700730-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="k">case</span><span class="w"> </span><span class="n">P1</span><span class="p" data-group-id="9144700730-3">(</span><span class="n">T</span><span class="p" data-group-id="9144700730-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="9144700730-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="9144700730-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="k">case</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="9144700730-5">(</span><span class="n">T1</span><span class="p" data-group-id="9144700730-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="9144700730-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p" data-group-id="9144700730-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                        </span><span class="p" data-group-id="9144700730-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9144700730-8">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p" data-group-id="9144700730-8">}</span><span class="p" data-group-id="9144700730-7">}</span><span class="p">;</span><span class="w">
│ │ │ +primitive parsers to produce more complex parsers.</p><p>First <code class="inline">pand</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pand</span><span class="p" data-group-id="4498643951-1">(</span><span class="n">P1</span><span class="p">,</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="4498643951-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="4498643951-2">(</span><span class="n">T</span><span class="p" data-group-id="4498643951-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="k">case</span><span class="w"> </span><span class="n">P1</span><span class="p" data-group-id="4498643951-3">(</span><span class="n">T</span><span class="p" data-group-id="4498643951-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="4498643951-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="4498643951-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                </span><span class="k">case</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="4498643951-5">(</span><span class="n">T1</span><span class="p" data-group-id="4498643951-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="4498643951-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p" data-group-id="4498643951-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                        </span><span class="p" data-group-id="4498643951-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4498643951-8">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p" data-group-id="4498643951-8">}</span><span class="p" data-group-id="4498643951-7">}</span><span class="p">;</span><span class="w">
│ │ │                      </span><span class="ss">fail</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                          </span><span class="ss">fail</span><span class="w">
│ │ │                  </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">fail</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                  </span><span class="ss">fail</span><span class="w">
│ │ │          </span><span class="k">end</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Given a parser <code class="inline">P1</code> for grammar <code class="inline">G1</code>, and a parser <code class="inline">P2</code> for grammar <code class="inline">G2</code>,
│ │ │  <code class="inline">pand(P1, P2)</code> returns a parser for the grammar, which consists of sequences of
│ │ │  tokens that satisfy <code class="inline">G1</code>, followed by sequences of tokens that satisfy <code class="inline">G2</code>.</p><p><code class="inline">por(P1, P2)</code> returns a parser for the language described by the grammar <code class="inline">G1</code> or
│ │ │ -<code class="inline">G2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">por</span><span class="p" data-group-id="7359747832-1">(</span><span class="n">P1</span><span class="p">,</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="7359747832-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="7359747832-2">(</span><span class="n">T</span><span class="p" data-group-id="7359747832-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="k">case</span><span class="w"> </span><span class="n">P1</span><span class="p" data-group-id="7359747832-3">(</span><span class="n">T</span><span class="p" data-group-id="7359747832-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="7359747832-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="7359747832-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="p" data-group-id="7359747832-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7359747832-6">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="n">R</span><span class="p" data-group-id="7359747832-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="7359747832-5">}</span><span class="p">;</span><span class="w">
│ │ │ +<code class="inline">G2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">por</span><span class="p" data-group-id="3861149220-1">(</span><span class="n">P1</span><span class="p">,</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="3861149220-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="3861149220-2">(</span><span class="n">T</span><span class="p" data-group-id="3861149220-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="k">case</span><span class="w"> </span><span class="n">P1</span><span class="p" data-group-id="3861149220-3">(</span><span class="n">T</span><span class="p" data-group-id="3861149220-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="3861149220-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="3861149220-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                </span><span class="p" data-group-id="3861149220-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3861149220-6">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="n">R</span><span class="p" data-group-id="3861149220-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="3861149220-5">}</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">fail</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="k">case</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="7359747832-7">(</span><span class="n">T</span><span class="p" data-group-id="7359747832-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="7359747832-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="7359747832-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                        </span><span class="p" data-group-id="7359747832-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7359747832-10">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="n">R1</span><span class="p" data-group-id="7359747832-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="7359747832-9">}</span><span class="p">;</span><span class="w">
│ │ │ +                </span><span class="k">case</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="3861149220-7">(</span><span class="n">T</span><span class="p" data-group-id="3861149220-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="3861149220-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="3861149220-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                        </span><span class="p" data-group-id="3861149220-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3861149220-10">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="n">R1</span><span class="p" data-group-id="3861149220-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="3861149220-9">}</span><span class="p">;</span><span class="w">
│ │ │                      </span><span class="ss">fail</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                          </span><span class="ss">fail</span><span class="w">
│ │ │                  </span><span class="k">end</span><span class="w">
│ │ │          </span><span class="k">end</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The original problem was to parse the grammar <code class="inline">(a | b) &amp; (c | d)</code>. The following
│ │ │ -code addresses this problem:</p><pre><code class="makeup erlang" translate="no"><span class="nf">grammar</span><span class="p" data-group-id="1220457544-1">(</span><span class="p" data-group-id="1220457544-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">pand</span><span class="p" data-group-id="1220457544-2">(</span><span class="w">
│ │ │ -         </span><span class="nf">por</span><span class="p" data-group-id="1220457544-3">(</span><span class="nf">pconst</span><span class="p" data-group-id="1220457544-4">(</span><span class="ss">a</span><span class="p" data-group-id="1220457544-4">)</span><span class="p">,</span><span class="w"> </span><span class="nf">pconst</span><span class="p" data-group-id="1220457544-5">(</span><span class="ss">b</span><span class="p" data-group-id="1220457544-5">)</span><span class="p" data-group-id="1220457544-3">)</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="nf">por</span><span class="p" data-group-id="1220457544-6">(</span><span class="nf">pconst</span><span class="p" data-group-id="1220457544-7">(</span><span class="ss">c</span><span class="p" data-group-id="1220457544-7">)</span><span class="p">,</span><span class="w"> </span><span class="nf">pconst</span><span class="p" data-group-id="1220457544-8">(</span><span class="ss">d</span><span class="p" data-group-id="1220457544-8">)</span><span class="p" data-group-id="1220457544-6">)</span><span class="p" data-group-id="1220457544-2">)</span><span class="p">.</span></code></pre><p>The following code adds a parser interface to the grammar:</p><pre><code class="makeup erlang" translate="no"><span class="nf">parse</span><span class="p" data-group-id="9205289354-1">(</span><span class="n">List</span><span class="p" data-group-id="9205289354-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9205289354-2">(</span><span class="nf">grammar</span><span class="p" data-group-id="9205289354-3">(</span><span class="p" data-group-id="9205289354-3">)</span><span class="p" data-group-id="9205289354-2">)</span><span class="p" data-group-id="9205289354-4">(</span><span class="n">List</span><span class="p" data-group-id="9205289354-4">)</span><span class="p">.</span></code></pre><p>The parser can be tested as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="4337828241-1">(</span><span class="p" data-group-id="4337828241-2">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4337828241-2">]</span><span class="p" data-group-id="4337828241-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4337828241-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="4337828241-4">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="4337828241-5">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="4337828241-6">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="4337828241-6">}</span><span class="p" data-group-id="4337828241-5">}</span><span class="p">,</span><span class="p" data-group-id="4337828241-7">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="4337828241-8">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4337828241-8">}</span><span class="p" data-group-id="4337828241-7">}</span><span class="p" data-group-id="4337828241-4">}</span><span class="p" data-group-id="4337828241-3">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="4337828241-9">(</span><span class="p" data-group-id="4337828241-10">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="4337828241-10">]</span><span class="p" data-group-id="4337828241-9">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4337828241-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="4337828241-12">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="4337828241-13">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="4337828241-14">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="4337828241-14">}</span><span class="p" data-group-id="4337828241-13">}</span><span class="p">,</span><span class="p" data-group-id="4337828241-15">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="4337828241-16">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="4337828241-16">}</span><span class="p" data-group-id="4337828241-15">}</span><span class="p" data-group-id="4337828241-12">}</span><span class="p" data-group-id="4337828241-11">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="4337828241-17">(</span><span class="p" data-group-id="4337828241-18">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4337828241-18">]</span><span class="p" data-group-id="4337828241-17">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4337828241-19">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="4337828241-20">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="4337828241-21">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="4337828241-22">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="4337828241-22">}</span><span class="p" data-group-id="4337828241-21">}</span><span class="p">,</span><span class="p" data-group-id="4337828241-23">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="4337828241-24">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4337828241-24">}</span><span class="p" data-group-id="4337828241-23">}</span><span class="p" data-group-id="4337828241-20">}</span><span class="p" data-group-id="4337828241-19">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="4337828241-25">(</span><span class="p" data-group-id="4337828241-26">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="4337828241-26">]</span><span class="p" data-group-id="4337828241-25">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4337828241-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="4337828241-28">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="4337828241-29">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="4337828241-30">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="4337828241-30">}</span><span class="p" data-group-id="4337828241-29">}</span><span class="p">,</span><span class="p" data-group-id="4337828241-31">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="4337828241-32">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="4337828241-32">}</span><span class="p" data-group-id="4337828241-31">}</span><span class="p" data-group-id="4337828241-28">}</span><span class="p" data-group-id="4337828241-27">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="4337828241-33">(</span><span class="p" data-group-id="4337828241-34">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="4337828241-34">]</span><span class="p" data-group-id="4337828241-33">)</span><span class="p">.</span><span class="w">
│ │ │ +code addresses this problem:</p><pre><code class="makeup erlang" translate="no"><span class="nf">grammar</span><span class="p" data-group-id="0613707353-1">(</span><span class="p" data-group-id="0613707353-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">pand</span><span class="p" data-group-id="0613707353-2">(</span><span class="w">
│ │ │ +         </span><span class="nf">por</span><span class="p" data-group-id="0613707353-3">(</span><span class="nf">pconst</span><span class="p" data-group-id="0613707353-4">(</span><span class="ss">a</span><span class="p" data-group-id="0613707353-4">)</span><span class="p">,</span><span class="w"> </span><span class="nf">pconst</span><span class="p" data-group-id="0613707353-5">(</span><span class="ss">b</span><span class="p" data-group-id="0613707353-5">)</span><span class="p" data-group-id="0613707353-3">)</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="nf">por</span><span class="p" data-group-id="0613707353-6">(</span><span class="nf">pconst</span><span class="p" data-group-id="0613707353-7">(</span><span class="ss">c</span><span class="p" data-group-id="0613707353-7">)</span><span class="p">,</span><span class="w"> </span><span class="nf">pconst</span><span class="p" data-group-id="0613707353-8">(</span><span class="ss">d</span><span class="p" data-group-id="0613707353-8">)</span><span class="p" data-group-id="0613707353-6">)</span><span class="p" data-group-id="0613707353-2">)</span><span class="p">.</span></code></pre><p>The following code adds a parser interface to the grammar:</p><pre><code class="makeup erlang" translate="no"><span class="nf">parse</span><span class="p" data-group-id="8890841961-1">(</span><span class="n">List</span><span class="p" data-group-id="8890841961-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8890841961-2">(</span><span class="nf">grammar</span><span class="p" data-group-id="8890841961-3">(</span><span class="p" data-group-id="8890841961-3">)</span><span class="p" data-group-id="8890841961-2">)</span><span class="p" data-group-id="8890841961-4">(</span><span class="n">List</span><span class="p" data-group-id="8890841961-4">)</span><span class="p">.</span></code></pre><p>The parser can be tested as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="8796494826-1">(</span><span class="p" data-group-id="8796494826-2">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="8796494826-2">]</span><span class="p" data-group-id="8796494826-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8796494826-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="8796494826-4">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="8796494826-5">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="8796494826-6">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="8796494826-6">}</span><span class="p" data-group-id="8796494826-5">}</span><span class="p">,</span><span class="p" data-group-id="8796494826-7">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="8796494826-8">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="8796494826-8">}</span><span class="p" data-group-id="8796494826-7">}</span><span class="p" data-group-id="8796494826-4">}</span><span class="p" data-group-id="8796494826-3">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="8796494826-9">(</span><span class="p" data-group-id="8796494826-10">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="8796494826-10">]</span><span class="p" data-group-id="8796494826-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8796494826-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="8796494826-12">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="8796494826-13">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="8796494826-14">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="8796494826-14">}</span><span class="p" data-group-id="8796494826-13">}</span><span class="p">,</span><span class="p" data-group-id="8796494826-15">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="8796494826-16">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="8796494826-16">}</span><span class="p" data-group-id="8796494826-15">}</span><span class="p" data-group-id="8796494826-12">}</span><span class="p" data-group-id="8796494826-11">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="8796494826-17">(</span><span class="p" data-group-id="8796494826-18">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="8796494826-18">]</span><span class="p" data-group-id="8796494826-17">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8796494826-19">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="8796494826-20">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="8796494826-21">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="8796494826-22">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="8796494826-22">}</span><span class="p" data-group-id="8796494826-21">}</span><span class="p">,</span><span class="p" data-group-id="8796494826-23">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="8796494826-24">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="8796494826-24">}</span><span class="p" data-group-id="8796494826-23">}</span><span class="p" data-group-id="8796494826-20">}</span><span class="p" data-group-id="8796494826-19">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="8796494826-25">(</span><span class="p" data-group-id="8796494826-26">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="8796494826-26">]</span><span class="p" data-group-id="8796494826-25">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8796494826-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="8796494826-28">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="8796494826-29">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="8796494826-30">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="8796494826-30">}</span><span class="p" data-group-id="8796494826-29">}</span><span class="p">,</span><span class="p" data-group-id="8796494826-31">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="8796494826-32">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="8796494826-32">}</span><span class="p" data-group-id="8796494826-31">}</span><span class="p" data-group-id="8796494826-28">}</span><span class="p" data-group-id="8796494826-27">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="8796494826-33">(</span><span class="p" data-group-id="8796494826-34">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="8796494826-34">]</span><span class="p" data-group-id="8796494826-33">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">fail</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="prog_ex_records.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/gen_server_concepts.html
│ │ │ @@ -157,63 +157,63 @@
│ │ │    <a href="#example" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Example</span>
│ │ │  </h2>
│ │ │  <p>An example of a simple server written in plain Erlang is provided in
│ │ │  <a href="design_principles.html#ch1">Overview</a>. The server can be reimplemented using
│ │ │ -<code class="inline">gen_server</code>, resulting in this callback module:</p><p><a href="" id="ex"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6718575104-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="6718575104-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="6718575104-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="6718575104-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">gen_server</code>, resulting in this callback module:</p><p><a href="" id="ex"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9353569052-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="9353569052-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="9353569052-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="9353569052-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6718575104-3">(</span><span class="p" data-group-id="6718575104-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6718575104-4">]</span><span class="p" data-group-id="6718575104-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6718575104-5">(</span><span class="p" data-group-id="6718575104-6">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6718575104-6">]</span><span class="p" data-group-id="6718575104-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6718575104-7">(</span><span class="p" data-group-id="6718575104-8">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6718575104-8">]</span><span class="p" data-group-id="6718575104-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9353569052-3">(</span><span class="p" data-group-id="9353569052-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9353569052-4">]</span><span class="p" data-group-id="9353569052-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9353569052-5">(</span><span class="p" data-group-id="9353569052-6">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9353569052-6">]</span><span class="p" data-group-id="9353569052-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9353569052-7">(</span><span class="p" data-group-id="9353569052-8">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9353569052-8">]</span><span class="p" data-group-id="9353569052-7">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="6718575104-9">(</span><span class="p" data-group-id="6718575104-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="6718575104-10">(</span><span class="p" data-group-id="6718575104-11">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="6718575104-11">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6718575104-12">[</span><span class="p" data-group-id="6718575104-12">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6718575104-13">[</span><span class="p" data-group-id="6718575104-13">]</span><span class="p" data-group-id="6718575104-10">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="9353569052-9">(</span><span class="p" data-group-id="9353569052-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="9353569052-10">(</span><span class="p" data-group-id="9353569052-11">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="9353569052-11">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9353569052-12">[</span><span class="p" data-group-id="9353569052-12">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9353569052-13">[</span><span class="p" data-group-id="9353569052-13">]</span><span class="p" data-group-id="9353569052-10">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="6718575104-14">(</span><span class="p" data-group-id="6718575104-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="6718575104-15">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="6718575104-15">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="9353569052-14">(</span><span class="p" data-group-id="9353569052-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="9353569052-15">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="9353569052-15">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="6718575104-16">(</span><span class="n">Ch</span><span class="p" data-group-id="6718575104-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="6718575104-17">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6718575104-18">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="6718575104-18">}</span><span class="p" data-group-id="6718575104-17">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="9353569052-16">(</span><span class="n">Ch</span><span class="p" data-group-id="9353569052-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="9353569052-17">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9353569052-18">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9353569052-18">}</span><span class="p" data-group-id="9353569052-17">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="6718575104-19">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="6718575104-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6718575104-20">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="6718575104-21">(</span><span class="p" data-group-id="6718575104-21">)</span><span class="p" data-group-id="6718575104-20">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="9353569052-19">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="9353569052-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9353569052-20">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="9353569052-21">(</span><span class="p" data-group-id="9353569052-21">)</span><span class="p" data-group-id="9353569052-20">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="6718575104-22">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6718575104-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6718575104-23">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="6718575104-23">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="6718575104-24">(</span><span class="n">Chs</span><span class="p" data-group-id="6718575104-24">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6718575104-25">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="6718575104-25">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="9353569052-22">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9353569052-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9353569052-23">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9353569052-23">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="9353569052-24">(</span><span class="n">Chs</span><span class="p" data-group-id="9353569052-24">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9353569052-25">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9353569052-25">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="6718575104-26">(</span><span class="p" data-group-id="6718575104-27">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="6718575104-27">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6718575104-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="6718575104-28">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6718575104-28">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6718575104-29">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="6718575104-29">}</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><h2 id="starting-a-gen_server" class="section-heading">
│ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="9353569052-26">(</span><span class="p" data-group-id="9353569052-27">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9353569052-27">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9353569052-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="9353569052-28">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9353569052-28">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9353569052-29">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9353569052-29">}</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><h2 id="starting-a-gen_server" class="section-heading">
│ │ │    <a href="#starting-a-gen_server" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Starting a Gen_Server</span>
│ │ │  </h2>
│ │ │  <p>In the example in the previous section, <code class="inline">gen_server</code> is started by calling
│ │ │ -<code class="inline">ch3:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="7540655398-1">(</span><span class="p" data-group-id="7540655398-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="7540655398-2">(</span><span class="p" data-group-id="7540655398-3">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="7540655398-3">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7540655398-4">[</span><span class="p" data-group-id="7540655398-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7540655398-5">[</span><span class="p" data-group-id="7540655398-5">]</span><span class="p" data-group-id="7540655398-2">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7540655398-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="7540655398-6">}</span></code></pre><p><code class="inline">start_link/0</code> calls function <a href="../../lib/stdlib-8.0/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a>.  This function
│ │ │ +<code class="inline">ch3:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="2129558770-1">(</span><span class="p" data-group-id="2129558770-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="2129558770-2">(</span><span class="p" data-group-id="2129558770-3">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="2129558770-3">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2129558770-4">[</span><span class="p" data-group-id="2129558770-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2129558770-5">[</span><span class="p" data-group-id="2129558770-5">]</span><span class="p" data-group-id="2129558770-2">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2129558770-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="2129558770-6">}</span></code></pre><p><code class="inline">start_link/0</code> calls function <a href="../../lib/stdlib-8.0/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a>.  This function
│ │ │  spawns and links to a new process, a <code class="inline">gen_server</code>.</p><ul><li><p>The first argument, <code class="inline">{local, ch3}</code>, specifies the name.
│ │ │  The gen_server is then locally registered as <code class="inline">ch3</code>.</p><p>If the name is omitted, the <code class="inline">gen_server</code> is not registered. Instead its pid
│ │ │  must be used. The name can also be given as <code class="inline">{global, Name}</code>, in which case
│ │ │  the <code class="inline">gen_server</code> is registered using <a href="../../lib/kernel-11.0/doc/html/global.html#register_name/2"><code class="inline">global:register_name/2</code></a>.</p></li><li><p>The second argument, <code class="inline">ch3</code>, is the name of the callback module, which is
│ │ │  the module where the callback functions are located.</p><p>The interface functions (<code class="inline">start_link/0</code>, <code class="inline">alloc/0</code>, and <code class="inline">free/1</code>) are located
│ │ │  in the same module as the callback functions (<code class="inline">init/1</code>, <code class="inline">handle_call/3</code>, and
│ │ │  <code class="inline">handle_cast/2</code>). It is usually good programming practice to have the code
│ │ │  corresponding to one process contained in a single module.</p></li><li><p>The third argument, <code class="inline">[]</code>, is a term that is passed as is to the callback
│ │ │  function <code class="inline">init</code>. Here, <code class="inline">init</code> does not need any indata and ignores the
│ │ │  argument.</p></li><li><p>The fourth argument, <code class="inline">[]</code>, is a list of options. See <a href="../../lib/stdlib-8.0/doc/html/gen_server.html"><code class="inline">gen_server</code></a>
│ │ │  for the available options.</p></li></ul><p>If name registration succeeds, the new <code class="inline">gen_server</code> process calls the callback
│ │ │  function <code class="inline">ch3:init([])</code>. <code class="inline">init</code> is expected to return <code class="inline">{ok, State}</code>, where
│ │ │  <code class="inline">State</code> is the internal state of the <code class="inline">gen_server</code>. In this case, the state is
│ │ │ -the available channels.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="1234696298-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="1234696298-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1234696298-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="1234696298-3">(</span><span class="p" data-group-id="1234696298-3">)</span><span class="p" data-group-id="1234696298-2">}</span><span class="p">.</span></code></pre><p><a href="../../lib/stdlib-8.0/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a> is synchronous. It does not return until the
│ │ │ +the available channels.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="1480694637-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="1480694637-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1480694637-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="1480694637-3">(</span><span class="p" data-group-id="1480694637-3">)</span><span class="p" data-group-id="1480694637-2">}</span><span class="p">.</span></code></pre><p><a href="../../lib/stdlib-8.0/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a> is synchronous. It does not return until the
│ │ │  <code class="inline">gen_server</code> has been initialized and is ready to receive requests.</p><p><a href="../../lib/stdlib-8.0/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a> must be used if the <code class="inline">gen_server</code> is part of
│ │ │  a supervision tree, meaning that it was started by a supervisor. There
│ │ │  is another function, <a href="../../lib/stdlib-8.0/doc/html/gen_server.html#start/4"><code class="inline">gen_server:start/4</code></a>, to start a standalone
│ │ │  <code class="inline">gen_server</code> that is not part of a supervision tree.</p><h2 id="synchronous-requests-call" class="section-heading">
│ │ │    <a href="#synchronous-requests-call" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -221,32 +221,32 @@
│ │ │  </h2>
│ │ │  <p>The synchronous request <code class="inline">alloc()</code> is implemented using <a href="../../lib/stdlib-8.0/doc/html/gen_server.html#call/2"><code class="inline">gen_server:call/2</code></a>:</p><pre><code class="text">alloc() -&gt;
│ │ │      gen_server:call(ch3, alloc).</code></pre><p><code class="inline">ch3</code> is the name of the <code class="inline">gen_server</code> and must agree with the name
│ │ │  used to start it. <code class="inline">alloc</code> is the actual request.</p><p>The request is made into a message and sent to the <code class="inline">gen_server</code>.
│ │ │  When the request is received, the <code class="inline">gen_server</code> calls
│ │ │  <code class="inline">handle_call(Request, From, State)</code>, which is expected to return
│ │ │  a tuple <code class="inline">{reply,Reply,State1}</code>. <code class="inline">Reply</code> is the reply that is to be sent back
│ │ │ -to the client, and <code class="inline">State1</code> is a new value for the state of the <code class="inline">gen_server</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_call</span><span class="p" data-group-id="3166158933-1">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3166158933-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3166158933-2">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="3166158933-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="3166158933-3">(</span><span class="n">Chs</span><span class="p" data-group-id="3166158933-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3166158933-4">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="3166158933-4">}</span><span class="p">.</span></code></pre><p>In this case, the reply is the allocated channel <code class="inline">Ch</code> and the new state is the
│ │ │ +to the client, and <code class="inline">State1</code> is a new value for the state of the <code class="inline">gen_server</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_call</span><span class="p" data-group-id="7500627931-1">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="7500627931-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7500627931-2">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="7500627931-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="7500627931-3">(</span><span class="n">Chs</span><span class="p" data-group-id="7500627931-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7500627931-4">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="7500627931-4">}</span><span class="p">.</span></code></pre><p>In this case, the reply is the allocated channel <code class="inline">Ch</code> and the new state is the
│ │ │  set of remaining available channels <code class="inline">Chs2</code>.</p><p>Thus, the call <code class="inline">ch3:alloc()</code> returns the allocated channel <code class="inline">Ch</code> and the
│ │ │  <code class="inline">gen_server</code> then waits for new requests, now with an updated list of
│ │ │  available channels.</p><h2 id="asynchronous-requests-cast" class="section-heading">
│ │ │    <a href="#asynchronous-requests-cast" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Asynchronous Requests - Cast</span>
│ │ │  </h2>
│ │ │ -<p>The asynchronous request <code class="inline">free(Ch)</code> is implemented using <a href="../../lib/stdlib-8.0/doc/html/gen_server.html#cast/2"><code class="inline">gen_server:cast/2</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">free</span><span class="p" data-group-id="7991407398-1">(</span><span class="n">Ch</span><span class="p" data-group-id="7991407398-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="7991407398-2">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7991407398-3">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="7991407398-3">}</span><span class="p" data-group-id="7991407398-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch3</code> is the name of the <code class="inline">gen_server</code>. <code class="inline">{free, Ch}</code> is the actual request.</p><p>The request is made into a message and sent to the <code class="inline">gen_server</code>.
│ │ │ +<p>The asynchronous request <code class="inline">free(Ch)</code> is implemented using <a href="../../lib/stdlib-8.0/doc/html/gen_server.html#cast/2"><code class="inline">gen_server:cast/2</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">free</span><span class="p" data-group-id="7398854011-1">(</span><span class="n">Ch</span><span class="p" data-group-id="7398854011-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="7398854011-2">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7398854011-3">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="7398854011-3">}</span><span class="p" data-group-id="7398854011-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch3</code> is the name of the <code class="inline">gen_server</code>. <code class="inline">{free, Ch}</code> is the actual request.</p><p>The request is made into a message and sent to the <code class="inline">gen_server</code>.
│ │ │  <code class="inline">cast</code>, and thus <code class="inline">free</code>, then returns <code class="inline">ok</code>.</p><p>When the request is received, the <code class="inline">gen_server</code> calls
│ │ │  <code class="inline">handle_cast(Request, State)</code>, which is expected to return a tuple
│ │ │ -<code class="inline">{noreply,State1}</code>. <code class="inline">State1</code> is a new value for the state of the <code class="inline">gen_server</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_cast</span><span class="p" data-group-id="0779815909-1">(</span><span class="p" data-group-id="0779815909-2">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="0779815909-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="0779815909-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="0779815909-3">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="0779815909-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0779815909-4">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="0779815909-4">}</span><span class="p">.</span></code></pre><p>In this case, the new state is the updated list of available channels <code class="inline">Chs2</code>.
│ │ │ +<code class="inline">{noreply,State1}</code>. <code class="inline">State1</code> is a new value for the state of the <code class="inline">gen_server</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_cast</span><span class="p" data-group-id="4318882621-1">(</span><span class="p" data-group-id="4318882621-2">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4318882621-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4318882621-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="4318882621-3">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4318882621-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4318882621-4">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="4318882621-4">}</span><span class="p">.</span></code></pre><p>In this case, the new state is the updated list of available channels <code class="inline">Chs2</code>.
│ │ │  The <code class="inline">gen_server</code> is now ready for new requests.</p><h2 id="stopping" class="section-heading">
│ │ │    <a href="#stopping" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Stopping</span>
│ │ │  </h2>
│ │ │  <h3 id="in-a-supervision-tree" class="section-heading">
│ │ │ @@ -257,69 +257,69 @@
│ │ │  </h3>
│ │ │  <p>If the <code class="inline">gen_server</code> is part of a supervision tree, no stop function is needed.
│ │ │  The <code class="inline">gen_server</code> is automatically terminated by its supervisor.  Exactly how
│ │ │  this is done is defined by a <a href="sup_princ.html#shutdown">shutdown strategy</a>
│ │ │  set in the supervisor.</p><p>If it is necessary to clean up before termination, the shutdown strategy
│ │ │  must be a time-out value and the <code class="inline">gen_server</code> must be set to trap exit signals
│ │ │  in function <code class="inline">init</code>. When ordered to shut down, the <code class="inline">gen_server</code> then calls
│ │ │ -the callback function <code class="inline">terminate(shutdown, State)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="2580931651-1">(</span><span class="n">Args</span><span class="p" data-group-id="2580931651-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +the callback function <code class="inline">terminate(shutdown, State)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="2445774446-1">(</span><span class="n">Args</span><span class="p" data-group-id="2445774446-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="2580931651-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="2580931651-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="2445774446-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="2445774446-2">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2580931651-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2580931651-3">}</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2445774446-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2445774446-3">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="2580931651-4">(</span><span class="ss">shutdown</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2580931651-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="2445774446-4">(</span><span class="ss">shutdown</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2445774446-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Code for cleaning up here</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><h3 id="standalone-gen_servers" class="section-heading">
│ │ │    <a href="#standalone-gen_servers" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Standalone Gen_Servers</span>
│ │ │  </h3>
│ │ │  <p>If the <code class="inline">gen_server</code> is not part of a supervision tree, a stop function
│ │ │  can be useful, for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2031253360-1">(</span><span class="p" data-group-id="2031253360-2">[</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2031253360-2">]</span><span class="p" data-group-id="2031253360-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5094501718-1">(</span><span class="p" data-group-id="5094501718-2">[</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5094501718-2">]</span><span class="p" data-group-id="5094501718-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="2031253360-3">(</span><span class="p" data-group-id="2031253360-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="2031253360-4">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p" data-group-id="2031253360-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="5094501718-3">(</span><span class="p" data-group-id="5094501718-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="5094501718-4">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p" data-group-id="5094501718-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="2031253360-5">(</span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2031253360-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2031253360-6">{</span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2031253360-6">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="2031253360-7">(</span><span class="p" data-group-id="2031253360-8">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2031253360-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2031253360-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="5094501718-5">(</span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5094501718-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5094501718-6">{</span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5094501718-6">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="5094501718-7">(</span><span class="p" data-group-id="5094501718-8">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="5094501718-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5094501718-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="2031253360-9">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2031253360-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="5094501718-9">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5094501718-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The callback function handling the <code class="inline">stop</code> request returns a tuple
│ │ │  <code class="inline">{stop,normal,State1}</code>, where <code class="inline">normal</code> specifies that it is
│ │ │  a normal termination and <code class="inline">State1</code> is a new value for the state
│ │ │  of the <code class="inline">gen_server</code>.  This causes the <code class="inline">gen_server</code> to call
│ │ │  <code class="inline">terminate(normal, State1)</code> and then it terminates gracefully.</p><h2 id="handling-other-messages" class="section-heading">
│ │ │    <a href="#handling-other-messages" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Handling Other Messages</span>
│ │ │  </h2>
│ │ │  <p>If the <code class="inline">gen_server</code> is to be able to receive other messages than requests,
│ │ │  the callback function <code class="inline">handle_info(Info, State)</code> must be implemented
│ │ │  to handle them.  Examples of other messages are exit messages,
│ │ │  if the <code class="inline">gen_server</code> is linked to other processes than the supervisor
│ │ │ -and it is trapping exit signals.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_info</span><span class="p" data-group-id="4094311853-1">(</span><span class="p" data-group-id="4094311853-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="4094311853-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4094311853-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +and it is trapping exit signals.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_info</span><span class="p" data-group-id="5380488573-1">(</span><span class="p" data-group-id="5380488573-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="5380488573-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5380488573-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Code to handle exits here.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4094311853-3">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="4094311853-3">}</span><span class="p">.</span></code></pre><p>The final function to implement is <code class="inline">code_change/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="2499779694-1">(</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="2499779694-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5380488573-3">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="5380488573-3">}</span><span class="p">.</span></code></pre><p>The final function to implement is <code class="inline">code_change/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="8681887926-1">(</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="8681887926-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Code to convert state (and more) during code change.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2499779694-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NewState</span><span class="p" data-group-id="2499779694-2">}</span><span class="p">.</span></code></pre>
│ │ │ +    </span><span class="p" data-group-id="8681887926-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NewState</span><span class="p" data-group-id="8681887926-2">}</span><span class="p">.</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="design_principles.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/included_applications.html
│ │ │ @@ -173,75 +173,75 @@
│ │ │  belonging to the primary application.</p><h2 id="specifying-included-applications" class="section-heading">
│ │ │    <a href="#specifying-included-applications" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Specifying Included Applications</span>
│ │ │  </h2>
│ │ │  <p>Which applications to include is defined by the <code class="inline">included_applications</code> key in
│ │ │ -the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3382266654-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3382266654-2">[</span><span class="p" data-group-id="3382266654-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Tree application&quot;</span><span class="p" data-group-id="3382266654-3">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3382266654-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="3382266654-4">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3382266654-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3382266654-6">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_server</span><span class="p" data-group-id="3382266654-6">]</span><span class="p" data-group-id="3382266654-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3382266654-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3382266654-8">[</span><span class="ss">prim_app_server</span><span class="p" data-group-id="3382266654-8">]</span><span class="p" data-group-id="3382266654-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3382266654-9">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3382266654-10">[</span><span class="ss">incl_app</span><span class="p" data-group-id="3382266654-10">]</span><span class="p" data-group-id="3382266654-9">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3382266654-11">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3382266654-12">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="3382266654-12">]</span><span class="p" data-group-id="3382266654-11">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3382266654-13">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3382266654-14">{</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="p" data-group-id="3382266654-15">[</span><span class="p" data-group-id="3382266654-15">]</span><span class="p" data-group-id="3382266654-14">}</span><span class="p" data-group-id="3382266654-13">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3382266654-16">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3382266654-17">[</span><span class="p" data-group-id="3382266654-18">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="3382266654-18">}</span><span class="p" data-group-id="3382266654-17">]</span><span class="p" data-group-id="3382266654-16">}</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3382266654-2">]</span><span class="p" data-group-id="3382266654-1">}</span><span class="p">.</span></code></pre><h2 id="synchronizing-processes-during-startup" class="section-heading">
│ │ │ +the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9692619020-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9692619020-2">[</span><span class="p" data-group-id="9692619020-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Tree application&quot;</span><span class="p" data-group-id="9692619020-3">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="9692619020-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="9692619020-4">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="9692619020-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9692619020-6">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_server</span><span class="p" data-group-id="9692619020-6">]</span><span class="p" data-group-id="9692619020-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="9692619020-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9692619020-8">[</span><span class="ss">prim_app_server</span><span class="p" data-group-id="9692619020-8">]</span><span class="p" data-group-id="9692619020-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="9692619020-9">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9692619020-10">[</span><span class="ss">incl_app</span><span class="p" data-group-id="9692619020-10">]</span><span class="p" data-group-id="9692619020-9">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="9692619020-11">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9692619020-12">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="9692619020-12">]</span><span class="p" data-group-id="9692619020-11">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="9692619020-13">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9692619020-14">{</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="p" data-group-id="9692619020-15">[</span><span class="p" data-group-id="9692619020-15">]</span><span class="p" data-group-id="9692619020-14">}</span><span class="p" data-group-id="9692619020-13">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="9692619020-16">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9692619020-17">[</span><span class="p" data-group-id="9692619020-18">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="9692619020-18">}</span><span class="p" data-group-id="9692619020-17">]</span><span class="p" data-group-id="9692619020-16">}</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9692619020-2">]</span><span class="p" data-group-id="9692619020-1">}</span><span class="p">.</span></code></pre><h2 id="synchronizing-processes-during-startup" class="section-heading">
│ │ │    <a href="#synchronizing-processes-during-startup" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Synchronizing Processes during Startup</span>
│ │ │  </h2>
│ │ │  <p>The supervisor tree of an included application is started as part of the
│ │ │  supervisor tree of the including application. If there is a need for
│ │ │  synchronization between processes in the including and included applications,
│ │ │  this can be achieved by using <em>start phases</em>.</p><p>Start phases are defined by the <code class="inline">start_phases</code> key in the <code class="inline">.app</code> file as a list
│ │ │  of tuples <code class="inline">{Phase,PhaseArgs}</code>, where <code class="inline">Phase</code> is an atom and <code class="inline">PhaseArgs</code> is a
│ │ │  term.</p><p>The value of the <code class="inline">mod</code> key of the including application must be set to
│ │ │  <code class="inline">{application_starter,[Module,StartArgs]}</code>, where <code class="inline">Module</code> as usual is the
│ │ │  application callback module. <code class="inline">StartArgs</code> is a term provided as argument to the
│ │ │ -callback function <code class="inline">Module:start/2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1089764112-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1089764112-2">[</span><span class="p" data-group-id="1089764112-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Tree application&quot;</span><span class="p" data-group-id="1089764112-3">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1089764112-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="1089764112-4">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1089764112-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1089764112-6">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_server</span><span class="p" data-group-id="1089764112-6">]</span><span class="p" data-group-id="1089764112-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1089764112-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1089764112-8">[</span><span class="ss">prim_app_server</span><span class="p" data-group-id="1089764112-8">]</span><span class="p" data-group-id="1089764112-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1089764112-9">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1089764112-10">[</span><span class="ss">incl_app</span><span class="p" data-group-id="1089764112-10">]</span><span class="p" data-group-id="1089764112-9">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1089764112-11">{</span><span class="ss">start_phases</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1089764112-12">[</span><span class="p" data-group-id="1089764112-13">{</span><span class="ss">init</span><span class="p">,</span><span class="p" data-group-id="1089764112-14">[</span><span class="p" data-group-id="1089764112-14">]</span><span class="p" data-group-id="1089764112-13">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1089764112-15">{</span><span class="ss">go</span><span class="p">,</span><span class="p" data-group-id="1089764112-16">[</span><span class="p" data-group-id="1089764112-16">]</span><span class="p" data-group-id="1089764112-15">}</span><span class="p" data-group-id="1089764112-12">]</span><span class="p" data-group-id="1089764112-11">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1089764112-17">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1089764112-18">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="1089764112-18">]</span><span class="p" data-group-id="1089764112-17">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1089764112-19">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1089764112-20">{</span><span class="ss">application_starter</span><span class="p">,</span><span class="p" data-group-id="1089764112-21">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="p" data-group-id="1089764112-22">[</span><span class="p" data-group-id="1089764112-22">]</span><span class="p" data-group-id="1089764112-21">]</span><span class="p" data-group-id="1089764112-20">}</span><span class="p" data-group-id="1089764112-19">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1089764112-23">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1089764112-24">[</span><span class="p" data-group-id="1089764112-25">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="1089764112-25">}</span><span class="p" data-group-id="1089764112-24">]</span><span class="p" data-group-id="1089764112-23">}</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1089764112-2">]</span><span class="p" data-group-id="1089764112-1">}</span><span class="p">.</span><span class="w">
│ │ │ +callback function <code class="inline">Module:start/2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1522600576-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="1522600576-2">[</span><span class="p" data-group-id="1522600576-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Tree application&quot;</span><span class="p" data-group-id="1522600576-3">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1522600576-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="1522600576-4">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1522600576-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1522600576-6">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_server</span><span class="p" data-group-id="1522600576-6">]</span><span class="p" data-group-id="1522600576-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1522600576-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1522600576-8">[</span><span class="ss">prim_app_server</span><span class="p" data-group-id="1522600576-8">]</span><span class="p" data-group-id="1522600576-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1522600576-9">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1522600576-10">[</span><span class="ss">incl_app</span><span class="p" data-group-id="1522600576-10">]</span><span class="p" data-group-id="1522600576-9">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1522600576-11">{</span><span class="ss">start_phases</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1522600576-12">[</span><span class="p" data-group-id="1522600576-13">{</span><span class="ss">init</span><span class="p">,</span><span class="p" data-group-id="1522600576-14">[</span><span class="p" data-group-id="1522600576-14">]</span><span class="p" data-group-id="1522600576-13">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1522600576-15">{</span><span class="ss">go</span><span class="p">,</span><span class="p" data-group-id="1522600576-16">[</span><span class="p" data-group-id="1522600576-16">]</span><span class="p" data-group-id="1522600576-15">}</span><span class="p" data-group-id="1522600576-12">]</span><span class="p" data-group-id="1522600576-11">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1522600576-17">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1522600576-18">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="1522600576-18">]</span><span class="p" data-group-id="1522600576-17">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1522600576-19">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1522600576-20">{</span><span class="ss">application_starter</span><span class="p">,</span><span class="p" data-group-id="1522600576-21">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="p" data-group-id="1522600576-22">[</span><span class="p" data-group-id="1522600576-22">]</span><span class="p" data-group-id="1522600576-21">]</span><span class="p" data-group-id="1522600576-20">}</span><span class="p" data-group-id="1522600576-19">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1522600576-23">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1522600576-24">[</span><span class="p" data-group-id="1522600576-25">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="1522600576-25">}</span><span class="p" data-group-id="1522600576-24">]</span><span class="p" data-group-id="1522600576-23">}</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="1522600576-2">]</span><span class="p" data-group-id="1522600576-1">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="p" data-group-id="1089764112-26">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1089764112-27">[</span><span class="p" data-group-id="1089764112-28">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Included application&quot;</span><span class="p" data-group-id="1089764112-28">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1089764112-29">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="1089764112-29">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1089764112-30">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1089764112-31">[</span><span class="ss">incl_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app_server</span><span class="p" data-group-id="1089764112-31">]</span><span class="p" data-group-id="1089764112-30">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1089764112-32">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1089764112-33">[</span><span class="p" data-group-id="1089764112-33">]</span><span class="p" data-group-id="1089764112-32">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1089764112-34">{</span><span class="ss">start_phases</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1089764112-35">[</span><span class="p" data-group-id="1089764112-36">{</span><span class="ss">go</span><span class="p">,</span><span class="p" data-group-id="1089764112-37">[</span><span class="p" data-group-id="1089764112-37">]</span><span class="p" data-group-id="1089764112-36">}</span><span class="p" data-group-id="1089764112-35">]</span><span class="p" data-group-id="1089764112-34">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1089764112-38">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1089764112-39">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="1089764112-39">]</span><span class="p" data-group-id="1089764112-38">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1089764112-40">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1089764112-41">{</span><span class="ss">incl_app_cb</span><span class="p">,</span><span class="p" data-group-id="1089764112-42">[</span><span class="p" data-group-id="1089764112-42">]</span><span class="p" data-group-id="1089764112-41">}</span><span class="p" data-group-id="1089764112-40">}</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1089764112-27">]</span><span class="p" data-group-id="1089764112-26">}</span><span class="p">.</span></code></pre><p>When starting a primary application with included applications, the primary
│ │ │ +</span><span class="p" data-group-id="1522600576-26">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="1522600576-27">[</span><span class="p" data-group-id="1522600576-28">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Included application&quot;</span><span class="p" data-group-id="1522600576-28">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1522600576-29">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="1522600576-29">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1522600576-30">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1522600576-31">[</span><span class="ss">incl_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app_server</span><span class="p" data-group-id="1522600576-31">]</span><span class="p" data-group-id="1522600576-30">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1522600576-32">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1522600576-33">[</span><span class="p" data-group-id="1522600576-33">]</span><span class="p" data-group-id="1522600576-32">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1522600576-34">{</span><span class="ss">start_phases</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1522600576-35">[</span><span class="p" data-group-id="1522600576-36">{</span><span class="ss">go</span><span class="p">,</span><span class="p" data-group-id="1522600576-37">[</span><span class="p" data-group-id="1522600576-37">]</span><span class="p" data-group-id="1522600576-36">}</span><span class="p" data-group-id="1522600576-35">]</span><span class="p" data-group-id="1522600576-34">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1522600576-38">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1522600576-39">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="1522600576-39">]</span><span class="p" data-group-id="1522600576-38">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1522600576-40">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1522600576-41">{</span><span class="ss">incl_app_cb</span><span class="p">,</span><span class="p" data-group-id="1522600576-42">[</span><span class="p" data-group-id="1522600576-42">]</span><span class="p" data-group-id="1522600576-41">}</span><span class="p" data-group-id="1522600576-40">}</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="1522600576-27">]</span><span class="p" data-group-id="1522600576-26">}</span><span class="p">.</span></code></pre><p>When starting a primary application with included applications, the primary
│ │ │  application is started the normal way, that is:</p><ul><li>The application controller creates an application master for the application</li><li>The application master calls <code class="inline">Module:start(normal, StartArgs)</code> to start the
│ │ │  top supervisor.</li></ul><p>Then, for the primary application and each included application in top-down,
│ │ │  left-to-right order, the application master calls
│ │ │  <code class="inline">Module:start_phase(Phase, Type, PhaseArgs)</code> for each phase defined for the
│ │ │  primary application, in that order. If a phase is not defined for an included
│ │ │  application, the function is not called for this phase and application.</p><p>The following requirements apply to the <code class="inline">.app</code> file for an included application:</p><ul><li>The <code class="inline">{mod, {Module,StartArgs}}</code> option must be included. This option is used
│ │ │  to find the callback module <code class="inline">Module</code> of the application. <code class="inline">StartArgs</code> is
│ │ │  ignored, as <code class="inline">Module:start/2</code> is called only for the primary application.</li><li>If the included application itself contains included applications, instead the
│ │ │  <code class="inline">{mod, {application_starter, [Module,StartArgs]}}</code> option must be included.</li><li>The <code class="inline">{start_phases, [{Phase,PhaseArgs}]}</code> option must be included, and the set
│ │ │  of specified phases must be a subset of the set of phases specified for the
│ │ │  primary application.</li></ul><p>When starting <code class="inline">prim_app</code> as defined above, the application controller calls the
│ │ │  following callback functions before <code class="inline">application:start(prim_app)</code> returns a
│ │ │ -value:</p><pre><code class="makeup erlang" translate="no"><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8604660960-1">(</span><span class="ss">prim_app</span><span class="p" data-group-id="8604660960-1">)</span><span class="w">
│ │ │ - </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8604660960-2">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8604660960-3">[</span><span class="p" data-group-id="8604660960-3">]</span><span class="p" data-group-id="8604660960-2">)</span><span class="w">
│ │ │ - </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="8604660960-4">(</span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8604660960-5">[</span><span class="p" data-group-id="8604660960-5">]</span><span class="p" data-group-id="8604660960-4">)</span><span class="w">
│ │ │ - </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="8604660960-6">(</span><span class="ss">go</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8604660960-7">[</span><span class="p" data-group-id="8604660960-7">]</span><span class="p" data-group-id="8604660960-6">)</span><span class="w">
│ │ │ - </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">incl_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="8604660960-8">(</span><span class="ss">go</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8604660960-9">[</span><span class="p" data-group-id="8604660960-9">]</span><span class="p" data-group-id="8604660960-8">)</span><span class="w">
│ │ │ +value:</p><pre><code class="makeup erlang" translate="no"><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2272076622-1">(</span><span class="ss">prim_app</span><span class="p" data-group-id="2272076622-1">)</span><span class="w">
│ │ │ + </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2272076622-2">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2272076622-3">[</span><span class="p" data-group-id="2272076622-3">]</span><span class="p" data-group-id="2272076622-2">)</span><span class="w">
│ │ │ + </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="2272076622-4">(</span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2272076622-5">[</span><span class="p" data-group-id="2272076622-5">]</span><span class="p" data-group-id="2272076622-4">)</span><span class="w">
│ │ │ + </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="2272076622-6">(</span><span class="ss">go</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2272076622-7">[</span><span class="p" data-group-id="2272076622-7">]</span><span class="p" data-group-id="2272076622-6">)</span><span class="w">
│ │ │ + </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">incl_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="2272076622-8">(</span><span class="ss">go</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2272076622-9">[</span><span class="p" data-group-id="2272076622-9">]</span><span class="p" data-group-id="2272076622-8">)</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="applications.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/install-win32.html
│ │ │ @@ -295,15 +295,15 @@
│ │ │  </span><span class="gp unselectable">$ </span><span class="">cd erts/emulator
│ │ │  </span><span class="gp unselectable">$ </span><span class="">make debug
│ │ │  </span><span class="gp unselectable">$ </span><span class="">cd ../etc
│ │ │  </span><span class="gp unselectable">$ </span><span class="">make debug
│ │ │  </span></code></pre><p>and sometimes</p><pre><code class="makeup shell" translate="no"><span class="gp unselectable">$ </span><span class="">cd $ERL_TOP
│ │ │  </span><span class="gp unselectable">$ </span><span class="">make local_setup
│ │ │  </span></code></pre><p>So now when you run <code class="inline">$ERL_TOP/erl.exe</code>, you should have a debug compiled
│ │ │ -emulator, which you will see if you do a:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="4650489168-1">(</span><span class="ss">system_version</span><span class="p" data-group-id="4650489168-1">)</span><span class="p">.</span></code></pre><p>in the erlang shell. If the returned string contains <code class="inline">[debug]</code>, you
│ │ │ +emulator, which you will see if you do a:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="7062596048-1">(</span><span class="ss">system_version</span><span class="p" data-group-id="7062596048-1">)</span><span class="p">.</span></code></pre><p>in the erlang shell. If the returned string contains <code class="inline">[debug]</code>, you
│ │ │  got a debug compiled emulator.</p><p>To hack the erlang libraries, you simply do a <code class="inline">make opt</code> in the
│ │ │  specific &quot;applications&quot; directory, like:</p><pre><code class="makeup shell" translate="no"><span class="gp unselectable">$ </span><span class="">cd $ERL_TOP/lib/stdlib
│ │ │  </span><span class="gp unselectable">$ </span><span class="">make opt
│ │ │  </span></code></pre><p>or even in the source directory...</p><pre><code class="makeup shell" translate="no"><span class="gp unselectable">$ </span><span class="">cd $ERL_TOP/lib/stdlib/src
│ │ │  </span><span class="gp unselectable">$ </span><span class="">make opt
│ │ │  </span></code></pre><p>Note that you're expected to have a fresh Erlang in your path when
│ │ │  doing this, preferably the plain 29 you have built in the previous
│ │ │ @@ -318,19 +318,19 @@
│ │ │  </span><span class="">:$ERL_TOP/erts/etc/win32/wsl_tools:$ERL_TOP/bootstrap/bin:$PATH
│ │ │  </span></code></pre><p>That should make it possible to rebuild any library without hassle...</p><p>If you want to copy a library (an application) newly built, to a
│ │ │  release area, you do like with the emulator:</p><pre><code class="makeup shell" translate="no"><span class="gp unselectable">$ </span><span class="">cd $ERL_TOP/lib/stdlib
│ │ │  </span><span class="gp unselectable">$ </span><span class="">make TESTROOT=/tmp/erlang_release release
│ │ │  </span></code></pre><p>Remember that:</p><ul><li><p>  Windows specific C-code goes in the <code class="inline">$ERL_TOP/erts/emulator/sys/win32</code>,
│ │ │  <code class="inline">$ERL_TOP/erts/emulator/drivers/win32</code> or <code class="inline">$ERL_TOP/erts/etc/win32</code>.</p></li><li><p>  Windows specific erlang code should be used conditionally and the
│ │ │  host OS tested in <em>runtime</em>, the exactly same beam files should be
│ │ │ -distributed for every platform! So write code like:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">os</span><span class="p">:</span><span class="nf">type</span><span class="p" data-group-id="2738301042-1">(</span><span class="p" data-group-id="2738301042-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2738301042-2">{</span><span class="ss">win32</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="2738301042-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nf">do_windows_specific</span><span class="p" data-group-id="2738301042-3">(</span><span class="p" data-group-id="2738301042-3">)</span><span class="p">;</span><span class="w">
│ │ │ +distributed for every platform! So write code like:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">os</span><span class="p">:</span><span class="nf">type</span><span class="p" data-group-id="4022913633-1">(</span><span class="p" data-group-id="4022913633-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4022913633-2">{</span><span class="ss">win32</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4022913633-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nf">do_windows_specific</span><span class="p" data-group-id="4022913633-3">(</span><span class="p" data-group-id="4022913633-3">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Other</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nf">do_fallback_or_exit</span><span class="p" data-group-id="2738301042-4">(</span><span class="p" data-group-id="2738301042-4">)</span><span class="w">
│ │ │ +        </span><span class="nf">do_fallback_or_exit</span><span class="p" data-group-id="4022913633-4">(</span><span class="p" data-group-id="4022913633-4">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">,</span></code></pre></li></ul><p>That's basically all you need to get going.</p><h2 id="frequently-asked-questions" class="section-heading">
│ │ │    <a href="#frequently-asked-questions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Frequently Asked Questions</span>
│ │ │  </h2>
│ │ │  <ul><li><p>  Q: So, now I can build Erlang using GCC on Windows?</p><p>A: No, unfortunately not. You'll need Microsoft's Visual C++
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/list_comprehensions.html
│ │ │ @@ -117,37 +117,37 @@
│ │ │  
│ │ │  <h2 id="simple-examples" class="section-heading">
│ │ │    <a href="#simple-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Simple Examples</span>
│ │ │  </h2>
│ │ │ -<p>This section starts with a simple example, showing a generator and a filter:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="8871438977-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="8871438977-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8871438977-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="8871438977-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8871438977-3">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8871438977-3">]</span></code></pre><p>This is read as follows: The list of X such that X is taken from the list
│ │ │ +<p>This section starts with a simple example, showing a generator and a filter:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="7089012744-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="7089012744-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7089012744-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="7089012744-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7089012744-3">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7089012744-3">]</span></code></pre><p>This is read as follows: The list of X such that X is taken from the list
│ │ │  <code class="inline">[1,2,a,...]</code> and X is greater than 3.</p><p>The notation <code class="inline">X &lt;:- [1,2,a,...]</code> is a generator and the expression <code class="inline">X &gt; 3</code> is a
│ │ │  filter.</p><p>An additional filter, <a href="../../erts-17.0/doc/html/erlang.html#is_integer/1"><code class="inline">is_integer(X)</code></a>, can be added to
│ │ │ -restrict the result to integers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="3556445436-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="3556445436-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3556445436-2">]</span><span class="p">,</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="3556445436-3">(</span><span class="n">X</span><span class="p" data-group-id="3556445436-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3556445436-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3556445436-4">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3556445436-4">]</span></code></pre><p>Generators can be combined in two ways. For example, the Cartesian product of
│ │ │ -two lists can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="4721188420-1">[</span><span class="p" data-group-id="4721188420-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4721188420-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="4721188420-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4721188420-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="4721188420-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="4721188420-4">]</span><span class="p" data-group-id="4721188420-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4721188420-5">[</span><span class="p" data-group-id="4721188420-6">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="4721188420-6">}</span><span class="p">,</span><span class="p" data-group-id="4721188420-7">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="4721188420-7">}</span><span class="p">,</span><span class="p" data-group-id="4721188420-8">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="4721188420-8">}</span><span class="p">,</span><span class="p" data-group-id="4721188420-9">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="4721188420-9">}</span><span class="p">,</span><span class="p" data-group-id="4721188420-10">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="4721188420-10">}</span><span class="p">,</span><span class="p" data-group-id="4721188420-11">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="4721188420-11">}</span><span class="p" data-group-id="4721188420-5">]</span></code></pre><p>Alternatively, two lists can be zipped together using a zip generator as
│ │ │ -follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="1209272558-1">[</span><span class="p" data-group-id="1209272558-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1209272558-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="1209272558-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1209272558-3">]</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="1209272558-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1209272558-4">]</span><span class="p" data-group-id="1209272558-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1209272558-5">[</span><span class="p" data-group-id="1209272558-6">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1209272558-6">}</span><span class="p">,</span><span class="p" data-group-id="1209272558-7">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1209272558-7">}</span><span class="p">,</span><span class="p" data-group-id="1209272558-8">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1209272558-8">}</span><span class="p" data-group-id="1209272558-5">]</span></code></pre><p>Finally, multiple elements can be emitted by the list comprehension in each iteration:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="8474672146-1">[</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">100</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="8474672146-2">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="8474672146-2">]</span><span class="p" data-group-id="8474672146-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8474672146-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">102</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">103</span><span class="p" data-group-id="8474672146-3">]</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Strict generators are used by default in the examples. More details and
│ │ │ +restrict the result to integers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="1480350132-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="1480350132-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="1480350132-2">]</span><span class="p">,</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="1480350132-3">(</span><span class="n">X</span><span class="p" data-group-id="1480350132-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="1480350132-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1480350132-4">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="1480350132-4">]</span></code></pre><p>Generators can be combined in two ways. For example, the Cartesian product of
│ │ │ +two lists can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="0267472910-1">[</span><span class="p" data-group-id="0267472910-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0267472910-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="0267472910-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0267472910-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="0267472910-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="0267472910-4">]</span><span class="p" data-group-id="0267472910-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0267472910-5">[</span><span class="p" data-group-id="0267472910-6">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="0267472910-6">}</span><span class="p">,</span><span class="p" data-group-id="0267472910-7">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="0267472910-7">}</span><span class="p">,</span><span class="p" data-group-id="0267472910-8">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="0267472910-8">}</span><span class="p">,</span><span class="p" data-group-id="0267472910-9">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="0267472910-9">}</span><span class="p">,</span><span class="p" data-group-id="0267472910-10">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="0267472910-10">}</span><span class="p">,</span><span class="p" data-group-id="0267472910-11">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="0267472910-11">}</span><span class="p" data-group-id="0267472910-5">]</span></code></pre><p>Alternatively, two lists can be zipped together using a zip generator as
│ │ │ +follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="4928533594-1">[</span><span class="p" data-group-id="4928533594-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4928533594-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="4928533594-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4928533594-3">]</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="4928533594-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4928533594-4">]</span><span class="p" data-group-id="4928533594-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4928533594-5">[</span><span class="p" data-group-id="4928533594-6">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="4928533594-6">}</span><span class="p">,</span><span class="p" data-group-id="4928533594-7">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="4928533594-7">}</span><span class="p">,</span><span class="p" data-group-id="4928533594-8">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4928533594-8">}</span><span class="p" data-group-id="4928533594-5">]</span></code></pre><p>Finally, multiple elements can be emitted by the list comprehension in each iteration:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="3539088002-1">[</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">100</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="3539088002-2">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3539088002-2">]</span><span class="p" data-group-id="3539088002-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3539088002-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">102</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">103</span><span class="p" data-group-id="3539088002-3">]</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Strict generators are used by default in the examples. More details and
│ │ │  comparisons can be found in <a href="#strict-and-relaxed-generators">Strict and Relaxed Generators</a>.</p></section><h2 id="quick-sort" class="section-heading">
│ │ │    <a href="#quick-sort" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Quick Sort</span>
│ │ │  </h2>
│ │ │ -<p>The well-known quick sort routine can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">sort</span><span class="p" data-group-id="8988656579-1">(</span><span class="p" data-group-id="8988656579-2">[</span><span class="p" data-group-id="8988656579-2">]</span><span class="p" data-group-id="8988656579-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8988656579-3">[</span><span class="p" data-group-id="8988656579-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">sort</span><span class="p" data-group-id="8988656579-4">(</span><span class="p" data-group-id="8988656579-5">[</span><span class="p">_</span><span class="p" data-group-id="8988656579-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="8988656579-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">L</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">sort</span><span class="p" data-group-id="8988656579-6">(</span><span class="p" data-group-id="8988656579-7">[</span><span class="n">Pivot</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8988656579-7">]</span><span class="p" data-group-id="8988656579-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">sort</span><span class="p" data-group-id="8988656579-8">(</span><span class="p" data-group-id="8988656579-9">[</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Pivot</span><span class="p" data-group-id="8988656579-9">]</span><span class="p" data-group-id="8988656579-8">)</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8988656579-10">[</span><span class="n">Pivot</span><span class="p" data-group-id="8988656579-10">]</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ -    </span><span class="nf">sort</span><span class="p" data-group-id="8988656579-11">(</span><span class="p" data-group-id="8988656579-12">[</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">Pivot</span><span class="p" data-group-id="8988656579-12">]</span><span class="p" data-group-id="8988656579-11">)</span><span class="p">.</span></code></pre><p>The expression <code class="inline">[X || X &lt;:- T, X &lt; Pivot]</code> is the list of all elements in <code class="inline">T</code>
│ │ │ +<p>The well-known quick sort routine can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">sort</span><span class="p" data-group-id="4075161283-1">(</span><span class="p" data-group-id="4075161283-2">[</span><span class="p" data-group-id="4075161283-2">]</span><span class="p" data-group-id="4075161283-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4075161283-3">[</span><span class="p" data-group-id="4075161283-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">sort</span><span class="p" data-group-id="4075161283-4">(</span><span class="p" data-group-id="4075161283-5">[</span><span class="p">_</span><span class="p" data-group-id="4075161283-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4075161283-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">L</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">sort</span><span class="p" data-group-id="4075161283-6">(</span><span class="p" data-group-id="4075161283-7">[</span><span class="n">Pivot</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4075161283-7">]</span><span class="p" data-group-id="4075161283-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">sort</span><span class="p" data-group-id="4075161283-8">(</span><span class="p" data-group-id="4075161283-9">[</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Pivot</span><span class="p" data-group-id="4075161283-9">]</span><span class="p" data-group-id="4075161283-8">)</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4075161283-10">[</span><span class="n">Pivot</span><span class="p" data-group-id="4075161283-10">]</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ +    </span><span class="nf">sort</span><span class="p" data-group-id="4075161283-11">(</span><span class="p" data-group-id="4075161283-12">[</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">Pivot</span><span class="p" data-group-id="4075161283-12">]</span><span class="p" data-group-id="4075161283-11">)</span><span class="p">.</span></code></pre><p>The expression <code class="inline">[X || X &lt;:- T, X &lt; Pivot]</code> is the list of all elements in <code class="inline">T</code>
│ │ │  that are less than <code class="inline">Pivot</code>.</p><p><code class="inline">[X || X &lt;:- T, X &gt;= Pivot]</code> is the list of all elements in <code class="inline">T</code> that are greater
│ │ │  than or equal to <code class="inline">Pivot</code>.</p><p>With the algorithm above, a list is sorted as follows:</p><ul><li>A list with zero or one element is trivially sorted.</li><li>For lists with more than one element:<ol><li>The first element in the list is isolated as the pivot element.</li><li>The remaining list is partitioned into two sublists, such that:</li></ol><ul><li>The first sublist contains all elements that are smaller than the pivot
│ │ │  element.</li><li>The second sublist contains all elements that are greater than or equal to
│ │ │  the pivot element.</li></ul><ol><li>The sublists are recursively sorted by the same algorithm and the results
│ │ │  are combined, resulting in a list consisting of:</li></ol><ul><li>All elements from the first sublist, that is all elements smaller than the
│ │ │  pivot element, in sorted order.</li><li>The pivot element.</li><li>All elements from the second sublist, that is all elements greater than or
│ │ │  equal to the pivot element, in sorted order.</li></ul></li></ul><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>While the sorting algorithm as shown above serves as a nice example to
│ │ │ @@ -155,127 +155,127 @@
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/lists.html"><code class="inline">lists</code></a> module contains sorting functions that are implemented in a more
│ │ │  efficient way.</p></section><h2 id="permutations" class="section-heading">
│ │ │    <a href="#permutations" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Permutations</span>
│ │ │  </h2>
│ │ │ -<p>The following example generates all permutations of the elements in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">perms</span><span class="p" data-group-id="4524845415-1">(</span><span class="p" data-group-id="4524845415-2">[</span><span class="p" data-group-id="4524845415-2">]</span><span class="p" data-group-id="4524845415-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4524845415-3">[</span><span class="p" data-group-id="4524845415-4">[</span><span class="p" data-group-id="4524845415-4">]</span><span class="p" data-group-id="4524845415-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">perms</span><span class="p" data-group-id="4524845415-5">(</span><span class="n">L</span><span class="p" data-group-id="4524845415-5">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4524845415-6">[</span><span class="p" data-group-id="4524845415-7">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4524845415-7">]</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">H</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nf">perms</span><span class="p" data-group-id="4524845415-8">(</span><span class="n">L</span><span class="o">--</span><span class="p" data-group-id="4524845415-9">[</span><span class="n">H</span><span class="p" data-group-id="4524845415-9">]</span><span class="p" data-group-id="4524845415-8">)</span><span class="p" data-group-id="4524845415-6">]</span><span class="p">.</span></code></pre><p>This takes <code class="inline">H</code> from <code class="inline">L</code> in all possible ways. The result is the set of all lists
│ │ │ +<p>The following example generates all permutations of the elements in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">perms</span><span class="p" data-group-id="9411191377-1">(</span><span class="p" data-group-id="9411191377-2">[</span><span class="p" data-group-id="9411191377-2">]</span><span class="p" data-group-id="9411191377-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9411191377-3">[</span><span class="p" data-group-id="9411191377-4">[</span><span class="p" data-group-id="9411191377-4">]</span><span class="p" data-group-id="9411191377-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">perms</span><span class="p" data-group-id="9411191377-5">(</span><span class="n">L</span><span class="p" data-group-id="9411191377-5">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9411191377-6">[</span><span class="p" data-group-id="9411191377-7">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9411191377-7">]</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">H</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nf">perms</span><span class="p" data-group-id="9411191377-8">(</span><span class="n">L</span><span class="o">--</span><span class="p" data-group-id="9411191377-9">[</span><span class="n">H</span><span class="p" data-group-id="9411191377-9">]</span><span class="p" data-group-id="9411191377-8">)</span><span class="p" data-group-id="9411191377-6">]</span><span class="p">.</span></code></pre><p>This takes <code class="inline">H</code> from <code class="inline">L</code> in all possible ways. The result is the set of all lists
│ │ │  <code class="inline">[H|T]</code>, where <code class="inline">T</code> is the set of all possible permutations of <code class="inline">L</code>, with <code class="inline">H</code>
│ │ │ -removed:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">perms</span><span class="p" data-group-id="3146831564-1">(</span><span class="p" data-group-id="3146831564-2">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="3146831564-2">]</span><span class="p" data-group-id="3146831564-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3146831564-3">[</span><span class="p" data-group-id="3146831564-4">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="3146831564-4">]</span><span class="p">,</span><span class="p" data-group-id="3146831564-5">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">g</span><span class="p">,</span><span class="ss">u</span><span class="p" data-group-id="3146831564-5">]</span><span class="p">,</span><span class="p" data-group-id="3146831564-6">[</span><span class="ss">u</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="3146831564-6">]</span><span class="p">,</span><span class="p" data-group-id="3146831564-7">[</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3146831564-7">]</span><span class="p">,</span><span class="p" data-group-id="3146831564-8">[</span><span class="ss">g</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p" data-group-id="3146831564-8">]</span><span class="p">,</span><span class="p" data-group-id="3146831564-9">[</span><span class="ss">g</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3146831564-9">]</span><span class="p" data-group-id="3146831564-3">]</span></code></pre><h2 id="pythagorean-triplets" class="section-heading">
│ │ │ +removed:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">perms</span><span class="p" data-group-id="3621110008-1">(</span><span class="p" data-group-id="3621110008-2">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="3621110008-2">]</span><span class="p" data-group-id="3621110008-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3621110008-3">[</span><span class="p" data-group-id="3621110008-4">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="3621110008-4">]</span><span class="p">,</span><span class="p" data-group-id="3621110008-5">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">g</span><span class="p">,</span><span class="ss">u</span><span class="p" data-group-id="3621110008-5">]</span><span class="p">,</span><span class="p" data-group-id="3621110008-6">[</span><span class="ss">u</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="3621110008-6">]</span><span class="p">,</span><span class="p" data-group-id="3621110008-7">[</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3621110008-7">]</span><span class="p">,</span><span class="p" data-group-id="3621110008-8">[</span><span class="ss">g</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p" data-group-id="3621110008-8">]</span><span class="p">,</span><span class="p" data-group-id="3621110008-9">[</span><span class="ss">g</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3621110008-9">]</span><span class="p" data-group-id="3621110008-3">]</span></code></pre><h2 id="pythagorean-triplets" class="section-heading">
│ │ │    <a href="#pythagorean-triplets" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Pythagorean Triplets</span>
│ │ │  </h2>
│ │ │  <p>Pythagorean triplets are sets of integers <code class="inline">{A,B,C}</code> such that
│ │ │  <code class="inline">A**2 + B**2 = C**2</code>.</p><p>The function <code class="inline">pyth(N)</code> generates a list of all tuples <code class="inline">{A,B,C}</code> such that
│ │ │  <code class="inline">A**2 + B**2 = C**2</code> and where the sum of the sides is equal to, or less than,
│ │ │ -<code class="inline">N</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pyth</span><span class="p" data-group-id="9291324877-1">(</span><span class="n">N</span><span class="p" data-group-id="9291324877-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9291324877-2">[</span><span class="w"> </span><span class="p" data-group-id="9291324877-3">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p" data-group-id="9291324877-3">}</span><span class="w"> </span><span class="p">||</span><span class="w">
│ │ │ -        </span><span class="n">A</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="9291324877-4">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="9291324877-4">)</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="n">B</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="9291324877-5">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="9291324877-5">)</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="n">C</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="9291324877-6">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="9291324877-6">)</span><span class="p">,</span><span class="w">
│ │ │ +<code class="inline">N</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pyth</span><span class="p" data-group-id="8059964779-1">(</span><span class="n">N</span><span class="p" data-group-id="8059964779-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8059964779-2">[</span><span class="w"> </span><span class="p" data-group-id="8059964779-3">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p" data-group-id="8059964779-3">}</span><span class="w"> </span><span class="p">||</span><span class="w">
│ │ │ +        </span><span class="n">A</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="8059964779-4">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="8059964779-4">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="n">B</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="8059964779-5">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="8059964779-5">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="n">C</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="8059964779-6">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="8059964779-6">)</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">+</span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="n">A</span><span class="o">*</span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">*</span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">C</span><span class="o">*</span><span class="n">C</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9291324877-2">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="5131736945-1">(</span><span class="mi">3</span><span class="p" data-group-id="5131736945-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5131736945-2">[</span><span class="p" data-group-id="5131736945-2">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="5131736945-3">(</span><span class="mi">11</span><span class="p" data-group-id="5131736945-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5131736945-4">[</span><span class="p" data-group-id="5131736945-4">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="5131736945-5">(</span><span class="mi">12</span><span class="p" data-group-id="5131736945-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5131736945-6">[</span><span class="p" data-group-id="5131736945-7">{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5131736945-7">}</span><span class="p">,</span><span class="p" data-group-id="5131736945-8">{</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5131736945-8">}</span><span class="p" data-group-id="5131736945-6">]</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="5131736945-9">(</span><span class="mi">50</span><span class="p" data-group-id="5131736945-9">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5131736945-10">[</span><span class="p" data-group-id="5131736945-11">{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5131736945-11">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5131736945-12">{</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5131736945-12">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5131736945-13">{</span><span class="mi">5</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="5131736945-13">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5131736945-14">{</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="5131736945-14">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5131736945-15">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="5131736945-15">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5131736945-16">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">15</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="5131736945-16">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5131736945-17">{</span><span class="mi">9</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="5131736945-17">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5131736945-18">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="5131736945-18">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5131736945-19">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="5131736945-19">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5131736945-20">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">16</span><span class="p">,</span><span class="mi">20</span><span class="p" data-group-id="5131736945-20">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5131736945-21">{</span><span class="mi">15</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="5131736945-21">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5131736945-22">{</span><span class="mi">16</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">20</span><span class="p" data-group-id="5131736945-22">}</span><span class="p" data-group-id="5131736945-10">]</span></code></pre><p>The following code reduces the search space and is more efficient:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pyth1</span><span class="p" data-group-id="6321595151-1">(</span><span class="n">N</span><span class="p" data-group-id="6321595151-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="6321595151-2">[</span><span class="p" data-group-id="6321595151-3">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p" data-group-id="6321595151-3">}</span><span class="w"> </span><span class="p">||</span><span class="w">
│ │ │ -       </span><span class="n">A</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="6321595151-4">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="6321595151-4">)</span><span class="p">,</span><span class="w">
│ │ │ -       </span><span class="n">B</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="6321595151-5">(</span><span class="n">A</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="6321595151-5">)</span><span class="p">,</span><span class="w">
│ │ │ -       </span><span class="n">C</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="6321595151-6">(</span><span class="n">B</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="6321595151-6">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8059964779-2">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="8673689778-1">(</span><span class="mi">3</span><span class="p" data-group-id="8673689778-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8673689778-2">[</span><span class="p" data-group-id="8673689778-2">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="8673689778-3">(</span><span class="mi">11</span><span class="p" data-group-id="8673689778-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8673689778-4">[</span><span class="p" data-group-id="8673689778-4">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="8673689778-5">(</span><span class="mi">12</span><span class="p" data-group-id="8673689778-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8673689778-6">[</span><span class="p" data-group-id="8673689778-7">{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8673689778-7">}</span><span class="p">,</span><span class="p" data-group-id="8673689778-8">{</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8673689778-8">}</span><span class="p" data-group-id="8673689778-6">]</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="8673689778-9">(</span><span class="mi">50</span><span class="p" data-group-id="8673689778-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8673689778-10">[</span><span class="p" data-group-id="8673689778-11">{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8673689778-11">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8673689778-12">{</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8673689778-12">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8673689778-13">{</span><span class="mi">5</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="8673689778-13">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8673689778-14">{</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="8673689778-14">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8673689778-15">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="8673689778-15">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8673689778-16">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">15</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="8673689778-16">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8673689778-17">{</span><span class="mi">9</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="8673689778-17">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8673689778-18">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="8673689778-18">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8673689778-19">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="8673689778-19">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8673689778-20">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">16</span><span class="p">,</span><span class="mi">20</span><span class="p" data-group-id="8673689778-20">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8673689778-21">{</span><span class="mi">15</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="8673689778-21">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8673689778-22">{</span><span class="mi">16</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">20</span><span class="p" data-group-id="8673689778-22">}</span><span class="p" data-group-id="8673689778-10">]</span></code></pre><p>The following code reduces the search space and is more efficient:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pyth1</span><span class="p" data-group-id="6370283712-1">(</span><span class="n">N</span><span class="p" data-group-id="6370283712-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="6370283712-2">[</span><span class="p" data-group-id="6370283712-3">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p" data-group-id="6370283712-3">}</span><span class="w"> </span><span class="p">||</span><span class="w">
│ │ │ +       </span><span class="n">A</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="6370283712-4">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="6370283712-4">)</span><span class="p">,</span><span class="w">
│ │ │ +       </span><span class="n">B</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="6370283712-5">(</span><span class="n">A</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="6370283712-5">)</span><span class="p">,</span><span class="w">
│ │ │ +       </span><span class="n">C</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="6370283712-6">(</span><span class="n">B</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="6370283712-6">)</span><span class="p">,</span><span class="w">
│ │ │         </span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">+</span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w">
│ │ │ -       </span><span class="n">A</span><span class="o">*</span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">*</span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">C</span><span class="o">*</span><span class="n">C</span><span class="w"> </span><span class="p" data-group-id="6321595151-2">]</span><span class="p">.</span></code></pre><h2 id="simplifications-with-list-comprehensions" class="section-heading">
│ │ │ +       </span><span class="n">A</span><span class="o">*</span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">*</span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">C</span><span class="o">*</span><span class="n">C</span><span class="w"> </span><span class="p" data-group-id="6370283712-2">]</span><span class="p">.</span></code></pre><h2 id="simplifications-with-list-comprehensions" class="section-heading">
│ │ │    <a href="#simplifications-with-list-comprehensions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Simplifications With List Comprehensions</span>
│ │ │  </h2>
│ │ │  <p>As an example, list comprehensions can be used to simplify some of the functions
│ │ │ -in <code class="inline">lists.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">append</span><span class="p" data-group-id="6894111284-1">(</span><span class="n">L</span><span class="p" data-group-id="6894111284-1">)</span><span class="w">   </span><span class="p">-&gt;</span><span class="w">  </span><span class="p" data-group-id="6894111284-2">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">L1</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L1</span><span class="p" data-group-id="6894111284-2">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="6894111284-3">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="6894111284-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6894111284-4">[</span><span class="n">Fun</span><span class="p" data-group-id="6894111284-5">(</span><span class="n">X</span><span class="p" data-group-id="6894111284-5">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="6894111284-4">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">filter</span><span class="p" data-group-id="6894111284-6">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="6894111284-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6894111284-7">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="6894111284-8">(</span><span class="n">X</span><span class="p" data-group-id="6894111284-8">)</span><span class="p" data-group-id="6894111284-7">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">zip</span><span class="p" data-group-id="6894111284-9">(</span><span class="n">L1</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="6894111284-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6894111284-10">[</span><span class="p" data-group-id="6894111284-11">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p" data-group-id="6894111284-11">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L1</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="6894111284-10">]</span><span class="p">.</span></code></pre><h2 id="variable-bindings-in-list-comprehensions" class="section-heading">
│ │ │ +in <code class="inline">lists.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">append</span><span class="p" data-group-id="8145851928-1">(</span><span class="n">L</span><span class="p" data-group-id="8145851928-1">)</span><span class="w">   </span><span class="p">-&gt;</span><span class="w">  </span><span class="p" data-group-id="8145851928-2">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">L1</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L1</span><span class="p" data-group-id="8145851928-2">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="8145851928-3">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="8145851928-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8145851928-4">[</span><span class="n">Fun</span><span class="p" data-group-id="8145851928-5">(</span><span class="n">X</span><span class="p" data-group-id="8145851928-5">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="8145851928-4">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">filter</span><span class="p" data-group-id="8145851928-6">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="8145851928-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8145851928-7">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="8145851928-8">(</span><span class="n">X</span><span class="p" data-group-id="8145851928-8">)</span><span class="p" data-group-id="8145851928-7">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">zip</span><span class="p" data-group-id="8145851928-9">(</span><span class="n">L1</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="8145851928-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8145851928-10">[</span><span class="p" data-group-id="8145851928-11">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p" data-group-id="8145851928-11">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L1</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="8145851928-10">]</span><span class="p">.</span></code></pre><h2 id="variable-bindings-in-list-comprehensions" class="section-heading">
│ │ │    <a href="#variable-bindings-in-list-comprehensions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Variable Bindings in List Comprehensions</span>
│ │ │  </h2>
│ │ │  <p>The scope rules for variables that occur in list comprehensions are as follows:</p><ul><li>All variables that occur in a generator pattern are assumed to be &quot;fresh&quot;
│ │ │  variables.</li><li>Any variables that are defined before the list comprehension, and that are
│ │ │  used in filters, have the values they had before the list comprehension.</li><li>Variables cannot be exported from a list comprehension.</li><li>Within a zip generator, binding of all variables happens at the same time.</li></ul><p>As an example of these rules, suppose you want to write the function <code class="inline">select</code>,
│ │ │  which selects certain elements from a list of tuples. Suppose you write
│ │ │  <code class="inline">select(X, L) -&gt; [Y || {X, Y} &lt;- L].</code> with the intention of extracting all
│ │ │  tuples from <code class="inline">L</code>, where the first item is <code class="inline">X</code>.</p><p>Compiling this gives the following diagnostic:</p><pre><code class="text">./FileName.erl:Line: Warning: variable 'X' shadowed in generate</code></pre><p>This diagnostic warns that the variable <code class="inline">X</code> in the pattern is not the same as
│ │ │ -the variable <code class="inline">X</code> that occurs in the function head.</p><p>Evaluating <code class="inline">select</code> gives the following result:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">select</span><span class="p" data-group-id="5921934983-1">(</span><span class="ss">b</span><span class="p">,</span><span class="p" data-group-id="5921934983-2">[</span><span class="p" data-group-id="5921934983-3">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5921934983-3">}</span><span class="p">,</span><span class="p" data-group-id="5921934983-4">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5921934983-4">}</span><span class="p">,</span><span class="p" data-group-id="5921934983-5">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5921934983-5">}</span><span class="p">,</span><span class="p" data-group-id="5921934983-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="5921934983-6">}</span><span class="p" data-group-id="5921934983-2">]</span><span class="p" data-group-id="5921934983-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5921934983-7">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="5921934983-7">]</span></code></pre><p>This is not the wanted result. To achieve the desired effect, <code class="inline">select</code> must be
│ │ │ -written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">select</span><span class="p" data-group-id="1965685471-1">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="1965685471-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="p" data-group-id="1965685471-2">[</span><span class="n">Y</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="1965685471-3">{</span><span class="n">X1</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1965685471-3">}</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">X1</span><span class="p" data-group-id="1965685471-2">]</span><span class="p">.</span></code></pre><p>The generator now contains unbound variables and the test has been moved into
│ │ │ -the filter.</p><p>This now works as expected:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">select</span><span class="p" data-group-id="4419444283-1">(</span><span class="ss">b</span><span class="p">,</span><span class="p" data-group-id="4419444283-2">[</span><span class="p" data-group-id="4419444283-3">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4419444283-3">}</span><span class="p">,</span><span class="p" data-group-id="4419444283-4">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4419444283-4">}</span><span class="p">,</span><span class="p" data-group-id="4419444283-5">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4419444283-5">}</span><span class="p">,</span><span class="p" data-group-id="4419444283-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="4419444283-6">}</span><span class="p" data-group-id="4419444283-2">]</span><span class="p" data-group-id="4419444283-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4419444283-7">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="4419444283-7">]</span></code></pre><p>Also note that a variable in a generator pattern will shadow a variable with the
│ │ │ -same name bound in a previous generator pattern. For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="5353501290-1">[</span><span class="p" data-group-id="5353501290-2">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p" data-group-id="5353501290-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="5353501290-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5353501290-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="o">=</span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="5353501290-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5353501290-4">]</span><span class="p" data-group-id="5353501290-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5353501290-5">[</span><span class="p" data-group-id="5353501290-6">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="5353501290-6">}</span><span class="p">,</span><span class="p" data-group-id="5353501290-7">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="5353501290-7">}</span><span class="p">,</span><span class="p" data-group-id="5353501290-8">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5353501290-8">}</span><span class="p">,</span><span class="p" data-group-id="5353501290-9">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="5353501290-9">}</span><span class="p">,</span><span class="p" data-group-id="5353501290-10">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="5353501290-10">}</span><span class="p">,</span><span class="p" data-group-id="5353501290-11">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5353501290-11">}</span><span class="p">,</span><span class="p" data-group-id="5353501290-12">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="5353501290-12">}</span><span class="p">,</span><span class="p" data-group-id="5353501290-13">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="5353501290-13">}</span><span class="p">,</span><span class="p" data-group-id="5353501290-14">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5353501290-14">}</span><span class="p" data-group-id="5353501290-5">]</span></code></pre><p>A consequence of the rules for importing variables into a list comprehension is
│ │ │ +the variable <code class="inline">X</code> that occurs in the function head.</p><p>Evaluating <code class="inline">select</code> gives the following result:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">select</span><span class="p" data-group-id="5459085291-1">(</span><span class="ss">b</span><span class="p">,</span><span class="p" data-group-id="5459085291-2">[</span><span class="p" data-group-id="5459085291-3">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5459085291-3">}</span><span class="p">,</span><span class="p" data-group-id="5459085291-4">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5459085291-4">}</span><span class="p">,</span><span class="p" data-group-id="5459085291-5">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5459085291-5">}</span><span class="p">,</span><span class="p" data-group-id="5459085291-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="5459085291-6">}</span><span class="p" data-group-id="5459085291-2">]</span><span class="p" data-group-id="5459085291-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5459085291-7">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="5459085291-7">]</span></code></pre><p>This is not the wanted result. To achieve the desired effect, <code class="inline">select</code> must be
│ │ │ +written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">select</span><span class="p" data-group-id="9308754883-1">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="9308754883-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="p" data-group-id="9308754883-2">[</span><span class="n">Y</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="9308754883-3">{</span><span class="n">X1</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9308754883-3">}</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">X1</span><span class="p" data-group-id="9308754883-2">]</span><span class="p">.</span></code></pre><p>The generator now contains unbound variables and the test has been moved into
│ │ │ +the filter.</p><p>This now works as expected:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">select</span><span class="p" data-group-id="9747939929-1">(</span><span class="ss">b</span><span class="p">,</span><span class="p" data-group-id="9747939929-2">[</span><span class="p" data-group-id="9747939929-3">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9747939929-3">}</span><span class="p">,</span><span class="p" data-group-id="9747939929-4">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9747939929-4">}</span><span class="p">,</span><span class="p" data-group-id="9747939929-5">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9747939929-5">}</span><span class="p">,</span><span class="p" data-group-id="9747939929-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="9747939929-6">}</span><span class="p" data-group-id="9747939929-2">]</span><span class="p" data-group-id="9747939929-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9747939929-7">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="9747939929-7">]</span></code></pre><p>Also note that a variable in a generator pattern will shadow a variable with the
│ │ │ +same name bound in a previous generator pattern. For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="5355556244-1">[</span><span class="p" data-group-id="5355556244-2">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p" data-group-id="5355556244-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="5355556244-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5355556244-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="o">=</span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="5355556244-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5355556244-4">]</span><span class="p" data-group-id="5355556244-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5355556244-5">[</span><span class="p" data-group-id="5355556244-6">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="5355556244-6">}</span><span class="p">,</span><span class="p" data-group-id="5355556244-7">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="5355556244-7">}</span><span class="p">,</span><span class="p" data-group-id="5355556244-8">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5355556244-8">}</span><span class="p">,</span><span class="p" data-group-id="5355556244-9">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="5355556244-9">}</span><span class="p">,</span><span class="p" data-group-id="5355556244-10">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="5355556244-10">}</span><span class="p">,</span><span class="p" data-group-id="5355556244-11">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5355556244-11">}</span><span class="p">,</span><span class="p" data-group-id="5355556244-12">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="5355556244-12">}</span><span class="p">,</span><span class="p" data-group-id="5355556244-13">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="5355556244-13">}</span><span class="p">,</span><span class="p" data-group-id="5355556244-14">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5355556244-14">}</span><span class="p" data-group-id="5355556244-5">]</span></code></pre><p>A consequence of the rules for importing variables into a list comprehension is
│ │ │  that certain pattern matching operations must be moved into the filters and
│ │ │ -cannot be written directly in the generators.</p><p>To illustrate this, do <em>not</em> write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="0595212042-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0595212042-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +cannot be written directly in the generators.</p><p>To illustrate this, do <em>not</em> write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="6717759419-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6717759419-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0595212042-2">[</span><span class="w"> </span><span class="n">Expression</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">PatternInvolving</span><span class="w"> </span><span class="n">Y</span><span class="w">  </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Expr</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0595212042-2">]</span><span class="w">
│ │ │ -    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Instead, write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="2761584498-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2761584498-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6717759419-2">[</span><span class="w"> </span><span class="n">Expression</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">PatternInvolving</span><span class="w"> </span><span class="n">Y</span><span class="w">  </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Expr</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6717759419-2">]</span><span class="w">
│ │ │ +    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Instead, write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="2277758898-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2277758898-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2761584498-2">[</span><span class="w"> </span><span class="n">Expression</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">PatternInvolving</span><span class="w"> </span><span class="n">Y1</span><span class="w">  </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Expr</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Y1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2761584498-2">]</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2277758898-2">[</span><span class="w"> </span><span class="n">Expression</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">PatternInvolving</span><span class="w"> </span><span class="n">Y1</span><span class="w">  </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Expr</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Y1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2277758898-2">]</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="strict-and-relaxed-generators" class="section-heading">
│ │ │    <a href="#strict-and-relaxed-generators" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Strict and Relaxed Generators</span>
│ │ │  </h2>
│ │ │  <p>Strict and relaxed generators have different behaviors when the right-hand
│ │ │  side expression does not match the left-hand side pattern. A relaxed generator
│ │ │  ignores that term and continues on. A strict generator fails with an exception.</p><p>Their difference can be shown in the following example. The generator
│ │ │  expects a two-tuple pattern. If a relaxed generator is used, <code class="inline">b</code> will be
│ │ │  silently skipped. If a strict generator is used, an exception will be raised
│ │ │ -when the pattern matching fails with <code class="inline">b</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9830385892-1">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9830385892-1">}</span><span class="w"> </span><span class="o">&lt;-</span><span class="w">  </span><span class="p" data-group-id="9830385892-2">[</span><span class="p" data-group-id="9830385892-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="9830385892-3">}</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="9830385892-2">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9830385892-4">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9830385892-4">}</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="9830385892-5">[</span><span class="p" data-group-id="9830385892-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="9830385892-6">}</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="9830385892-5">]</span></code></pre><p>Semantically, strict or relaxed generators convey different intentions from
│ │ │ +when the pattern matching fails with <code class="inline">b</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5291089691-1">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5291089691-1">}</span><span class="w"> </span><span class="o">&lt;-</span><span class="w">  </span><span class="p" data-group-id="5291089691-2">[</span><span class="p" data-group-id="5291089691-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="5291089691-3">}</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="5291089691-2">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5291089691-4">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5291089691-4">}</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="p" data-group-id="5291089691-5">[</span><span class="p" data-group-id="5291089691-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="5291089691-6">}</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="5291089691-5">]</span></code></pre><p>Semantically, strict or relaxed generators convey different intentions from
│ │ │  the programmer. Strict generators are used when unexpected elements in the
│ │ │  input data should not be tolerated. Any element not conforming to specific
│ │ │  patterns should immediately crash the comprehension, because the program may
│ │ │  not be prepared to handle it.</p><p>For example, the following comprehension is rewritten from one in the Erlang
│ │ │  linter. It extracts arities from all defined functions. All elements in the
│ │ │  list <code class="inline">DefinedFuns</code> are two-tuples, containing name and arity for functions.
│ │ │  If any of them differs from this pattern, it means that something has added
│ │ │  an invalid item into the list of defined functions. It is better for the linter
│ │ │  to crash in the comprehension than to skip the invalid item and continue
│ │ │  running. Using a strict generator here is correct, because the linter should
│ │ │ -not hide the presence of an internal inconsistency.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0130517201-1">[</span><span class="n">Arity</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="0130517201-2">{</span><span class="p">_</span><span class="n">FunName</span><span class="p">,</span><span class="w"> </span><span class="n">Arity</span><span class="p" data-group-id="0130517201-2">}</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">DefinedFuns</span><span class="p" data-group-id="0130517201-1">]</span></code></pre><p>In contrast, relaxed generators are used when unexpected elements in the input
│ │ │ +not hide the presence of an internal inconsistency.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2603455591-1">[</span><span class="n">Arity</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="2603455591-2">{</span><span class="p">_</span><span class="n">FunName</span><span class="p">,</span><span class="w"> </span><span class="n">Arity</span><span class="p" data-group-id="2603455591-2">}</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">DefinedFuns</span><span class="p" data-group-id="2603455591-1">]</span></code></pre><p>In contrast, relaxed generators are used when unexpected elements in the input
│ │ │  data should be <em>filtered out</em>. The programmer is aware that some elements
│ │ │  may not conform to specific patterns. Those elements can be safely excluded
│ │ │  from the comprehension result.</p><p>For example, the following comprehension is from a compiler module that
│ │ │  transforms normal Erlang code to Core Erlang. It finds all defined functions
│ │ │  from an abstract form, and outputs them in two-tuples, each containing name and
│ │ │  arity of a function. Not all forms are function declarations. All the forms
│ │ │  that are not function declarations should be ignored by this comprehension.
│ │ │  Using a relaxed generator here is correct, because the programmer intends to
│ │ │ -exclude all elements with other patterns.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2822015996-1">[</span><span class="p" data-group-id="2822015996-2">{</span><span class="n">Name</span><span class="p">,</span><span class="n">Arity</span><span class="p" data-group-id="2822015996-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="2822015996-3">{</span><span class="ss">function</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="n">Name</span><span class="p">,</span><span class="n">Arity</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="2822015996-3">}</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Forms</span><span class="p" data-group-id="2822015996-1">]</span></code></pre><p>Strict and relaxed generators don't always have distinct use cases. When the
│ │ │ +exclude all elements with other patterns.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7382563283-1">[</span><span class="p" data-group-id="7382563283-2">{</span><span class="n">Name</span><span class="p">,</span><span class="n">Arity</span><span class="p" data-group-id="7382563283-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="7382563283-3">{</span><span class="ss">function</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="n">Name</span><span class="p">,</span><span class="n">Arity</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="7382563283-3">}</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Forms</span><span class="p" data-group-id="7382563283-1">]</span></code></pre><p>Strict and relaxed generators don't always have distinct use cases. When the
│ │ │  left-hand side pattern of a generator is a fresh variable, pattern matching
│ │ │  cannot fail. Using either strict or relaxed generators leads to the same
│ │ │  behavior. While the preference and use cases might be individual, it is
│ │ │  recommended to use strict generators when either can be used. Using strict
│ │ │  generators by default aligns with Erlang's &quot;Let it crash&quot; philosophy.</p>
│ │ │  </div>
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/listhandling.html
│ │ │ @@ -120,105 +120,105 @@
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Creating a List</span>
│ │ │  </h2>
│ │ │  <p>Lists can only be built starting from the end and attaching list elements at the
│ │ │  beginning. If you use the <code class="inline">++</code> operator as follows, a new list is created that
│ │ │  is a copy of the elements in <code class="inline">List1</code>, followed by <code class="inline">List2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">List1</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">List2</span></code></pre><p>Looking at how <a href="../../lib/stdlib-8.0/doc/html/lists.html#append/2"><code class="inline">lists:append/2</code></a> or <code class="inline">++</code> would be implemented in plain Erlang,
│ │ │ -clearly the first list is copied:</p><pre><code class="makeup erlang" translate="no"><span class="nf">append</span><span class="p" data-group-id="7011203814-1">(</span><span class="p" data-group-id="7011203814-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7011203814-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="7011203814-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7011203814-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">append</span><span class="p" data-group-id="7011203814-4">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="7011203814-4">)</span><span class="p" data-group-id="7011203814-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">append</span><span class="p" data-group-id="7011203814-5">(</span><span class="p" data-group-id="7011203814-6">[</span><span class="p" data-group-id="7011203814-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="7011203814-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +clearly the first list is copied:</p><pre><code class="makeup erlang" translate="no"><span class="nf">append</span><span class="p" data-group-id="2084230841-1">(</span><span class="p" data-group-id="2084230841-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2084230841-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="2084230841-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2084230841-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">append</span><span class="p" data-group-id="2084230841-4">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="2084230841-4">)</span><span class="p" data-group-id="2084230841-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">append</span><span class="p" data-group-id="2084230841-5">(</span><span class="p" data-group-id="2084230841-6">[</span><span class="p" data-group-id="2084230841-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="2084230841-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Tail</span><span class="p">.</span></code></pre><p>When recursing and building a list, it is important to ensure that you attach
│ │ │  the new elements to the beginning of the list. In this way, you will build <em>one</em>
│ │ │ -list, not hundreds or thousands of copies of the growing result list.</p><p>Let us first see how it is not to be done:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">bad_fib</span><span class="p" data-group-id="2785092114-1">(</span><span class="n">N</span><span class="p" data-group-id="2785092114-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">bad_fib</span><span class="p" data-group-id="2785092114-2">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2785092114-3">[</span><span class="p" data-group-id="2785092114-3">]</span><span class="p" data-group-id="2785092114-2">)</span><span class="p">.</span><span class="w">
│ │ │ +list, not hundreds or thousands of copies of the growing result list.</p><p>Let us first see how it is not to be done:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">bad_fib</span><span class="p" data-group-id="8893835871-1">(</span><span class="n">N</span><span class="p" data-group-id="8893835871-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">bad_fib</span><span class="p" data-group-id="8893835871-2">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8893835871-3">[</span><span class="p" data-group-id="8893835871-3">]</span><span class="p" data-group-id="8893835871-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">bad_fib</span><span class="p" data-group-id="2785092114-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="2785092114-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">bad_fib</span><span class="p" data-group-id="8893835871-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="8893835871-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Fibs</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">bad_fib</span><span class="p" data-group-id="2785092114-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="2785092114-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">bad_fib</span><span class="p" data-group-id="2785092114-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="2785092114-7">[</span><span class="n">Current</span><span class="p" data-group-id="2785092114-7">]</span><span class="p" data-group-id="2785092114-6">)</span><span class="p">.</span></code></pre><p>Here more than one list is built. In each iteration step a new list is created
│ │ │ +</span><span class="nf">bad_fib</span><span class="p" data-group-id="8893835871-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="8893835871-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">bad_fib</span><span class="p" data-group-id="8893835871-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="8893835871-7">[</span><span class="n">Current</span><span class="p" data-group-id="8893835871-7">]</span><span class="p" data-group-id="8893835871-6">)</span><span class="p">.</span></code></pre><p>Here more than one list is built. In each iteration step a new list is created
│ │ │  that is one element longer than the new previous list.</p><p>To avoid copying the result in each iteration, build the list in reverse order
│ │ │ -and reverse the list when you are done:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="7664247509-1">(</span><span class="n">N</span><span class="p" data-group-id="7664247509-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="7664247509-2">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7664247509-3">[</span><span class="p" data-group-id="7664247509-3">]</span><span class="p" data-group-id="7664247509-2">)</span><span class="p">.</span><span class="w">
│ │ │ +and reverse the list when you are done:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="6073452412-1">(</span><span class="n">N</span><span class="p" data-group-id="6073452412-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="6073452412-2">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6073452412-3">[</span><span class="p" data-group-id="6073452412-3">]</span><span class="p" data-group-id="6073452412-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="7664247509-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="7664247509-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="7664247509-5">(</span><span class="n">Fibs</span><span class="p" data-group-id="7664247509-5">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="7664247509-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="7664247509-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="7664247509-7">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7664247509-8">[</span><span class="n">Current</span><span class="p">|</span><span class="n">Fibs</span><span class="p" data-group-id="7664247509-8">]</span><span class="p" data-group-id="7664247509-7">)</span><span class="p">.</span></code></pre><h2 id="list-comprehensions" class="section-heading">
│ │ │ +</span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="6073452412-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="6073452412-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="6073452412-5">(</span><span class="n">Fibs</span><span class="p" data-group-id="6073452412-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="6073452412-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="6073452412-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="6073452412-7">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6073452412-8">[</span><span class="n">Current</span><span class="p">|</span><span class="n">Fibs</span><span class="p" data-group-id="6073452412-8">]</span><span class="p" data-group-id="6073452412-7">)</span><span class="p">.</span></code></pre><h2 id="list-comprehensions" class="section-heading">
│ │ │    <a href="#list-comprehensions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">List Comprehensions</span>
│ │ │  </h2>
│ │ │ -<p>A list comprehension:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3347208730-1">[</span><span class="n">Expr</span><span class="p" data-group-id="3347208730-2">(</span><span class="n">E</span><span class="p" data-group-id="3347208730-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="3347208730-1">]</span></code></pre><p>is basically translated to a local function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="4104701619-1">(</span><span class="p" data-group-id="4104701619-2">[</span><span class="n">E</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="4104701619-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="4104701619-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4104701619-3">[</span><span class="n">Expr</span><span class="p" data-group-id="4104701619-4">(</span><span class="n">E</span><span class="p" data-group-id="4104701619-4">)</span><span class="p">|</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="4104701619-5">(</span><span class="n">Tail</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="4104701619-5">)</span><span class="p" data-group-id="4104701619-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="4104701619-6">(</span><span class="p" data-group-id="4104701619-7">[</span><span class="p" data-group-id="4104701619-7">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Expr</span><span class="p" data-group-id="4104701619-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4104701619-8">[</span><span class="p" data-group-id="4104701619-8">]</span><span class="p">.</span></code></pre><p>If the result of the list comprehension will <em>obviously</em> not be used, a list
│ │ │ -will not be constructed. For example, in this code:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7022999711-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="7022999711-2">(</span><span class="n">E</span><span class="p" data-group-id="7022999711-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7022999711-1">]</span><span class="p">,</span><span class="w">
│ │ │ +<p>A list comprehension:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8829001195-1">[</span><span class="n">Expr</span><span class="p" data-group-id="8829001195-2">(</span><span class="n">E</span><span class="p" data-group-id="8829001195-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="8829001195-1">]</span></code></pre><p>is basically translated to a local function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="1663747901-1">(</span><span class="p" data-group-id="1663747901-2">[</span><span class="n">E</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="1663747901-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="1663747901-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1663747901-3">[</span><span class="n">Expr</span><span class="p" data-group-id="1663747901-4">(</span><span class="n">E</span><span class="p" data-group-id="1663747901-4">)</span><span class="p">|</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="1663747901-5">(</span><span class="n">Tail</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="1663747901-5">)</span><span class="p" data-group-id="1663747901-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="1663747901-6">(</span><span class="p" data-group-id="1663747901-7">[</span><span class="p" data-group-id="1663747901-7">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Expr</span><span class="p" data-group-id="1663747901-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1663747901-8">[</span><span class="p" data-group-id="1663747901-8">]</span><span class="p">.</span></code></pre><p>If the result of the list comprehension will <em>obviously</em> not be used, a list
│ │ │ +will not be constructed. For example, in this code:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4809409717-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="4809409717-2">(</span><span class="n">E</span><span class="p" data-group-id="4809409717-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="4809409717-1">]</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>or in this code:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="n">Var</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3718249883-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="3718249883-2">(</span><span class="n">E</span><span class="p" data-group-id="3718249883-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="3718249883-1">]</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="6539155602-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="6539155602-2">(</span><span class="n">E</span><span class="p" data-group-id="6539155602-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="6539155602-1">]</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">some_function</span><span class="p" data-group-id="3718249883-3">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3718249883-3">)</span><span class="p">,</span></code></pre><p>the value is not assigned to a variable, not passed to another function, and not
│ │ │ +</span><span class="nf">some_function</span><span class="p" data-group-id="6539155602-3">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6539155602-3">)</span><span class="p">,</span></code></pre><p>the value is not assigned to a variable, not passed to another function, and not
│ │ │  returned. This means that there is no need to construct a list and the compiler
│ │ │ -will simplify the code for the list comprehension to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="7029701620-1">(</span><span class="p" data-group-id="7029701620-2">[</span><span class="n">E</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="7029701620-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="7029701620-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Expr</span><span class="p" data-group-id="7029701620-3">(</span><span class="n">E</span><span class="p" data-group-id="7029701620-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="7029701620-4">(</span><span class="n">Tail</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="7029701620-4">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="7029701620-5">(</span><span class="p" data-group-id="7029701620-6">[</span><span class="p" data-group-id="7029701620-6">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Expr</span><span class="p" data-group-id="7029701620-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7029701620-7">[</span><span class="p" data-group-id="7029701620-7">]</span><span class="p">.</span></code></pre><p>The compiler also understands that assigning to <code class="inline">_</code> means that the value will
│ │ │ -not be used. Therefore, the code in the following example will also be optimized:</p><pre><code class="makeup erlang" translate="no"><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1015173667-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="1015173667-2">(</span><span class="n">E</span><span class="p" data-group-id="1015173667-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="1015173667-1">]</span><span class="p">,</span><span class="w">
│ │ │ +will simplify the code for the list comprehension to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="4688465478-1">(</span><span class="p" data-group-id="4688465478-2">[</span><span class="n">E</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="4688465478-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="4688465478-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Expr</span><span class="p" data-group-id="4688465478-3">(</span><span class="n">E</span><span class="p" data-group-id="4688465478-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="4688465478-4">(</span><span class="n">Tail</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="4688465478-4">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="4688465478-5">(</span><span class="p" data-group-id="4688465478-6">[</span><span class="p" data-group-id="4688465478-6">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Expr</span><span class="p" data-group-id="4688465478-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4688465478-7">[</span><span class="p" data-group-id="4688465478-7">]</span><span class="p">.</span></code></pre><p>The compiler also understands that assigning to <code class="inline">_</code> means that the value will
│ │ │ +not be used. Therefore, the code in the following example will also be optimized:</p><pre><code class="makeup erlang" translate="no"><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4910003475-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="4910003475-2">(</span><span class="n">E</span><span class="p" data-group-id="4910003475-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="4910003475-1">]</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="p">.</span></code></pre><h2 id="deep-and-flat-lists" class="section-heading">
│ │ │    <a href="#deep-and-flat-lists" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Deep and Flat Lists</span>
│ │ │  </h2>
│ │ │  <p><a href="../../lib/stdlib-8.0/doc/html/lists.html#flatten/1"><code class="inline">lists:flatten/1</code></a> builds an entirely new list. It is therefore expensive, and
│ │ │  even <em>more</em> expensive than the <code class="inline">++</code> operator (which copies its left argument,
│ │ │  but not its right argument).</p><p>In the following situations it is unnecessary to call <a href="../../lib/stdlib-8.0/doc/html/lists.html#flatten/1"><code class="inline">lists:flatten/1</code></a>:</p><ul><li>When sending data to a port. Ports understand deep lists so there is no reason
│ │ │  to flatten the list before sending it to the port.</li><li>When calling BIFs that accept deep lists, such as
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#list_to_binary/1"><code class="inline">list_to_binary/1</code></a> or
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#iolist_to_binary/1"><code class="inline">iolist_to_binary/1</code></a>.</li><li>When you know that your list is only one level deep. Use <a href="../../lib/stdlib-8.0/doc/html/lists.html#append/1"><code class="inline">lists:append/1</code></a>
│ │ │ -instead.</li></ul><p><em>Examples:</em></p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">port_command</span><span class="p" data-group-id="4314752764-1">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">DeepList</span><span class="p" data-group-id="4314752764-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">port_command</span><span class="p" data-group-id="9340312995-1">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">flatten</span><span class="p" data-group-id="9340312995-2">(</span><span class="n">DeepList</span><span class="p" data-group-id="9340312995-2">)</span><span class="p" data-group-id="9340312995-1">)</span></code></pre><p>A common way to send a zero-terminated string to a port is the following:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TerminatedStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="6705796952-1">[</span><span class="mi">0</span><span class="p" data-group-id="6705796952-1">]</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">port_command</span><span class="p" data-group-id="6705796952-2">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">TerminatedStr</span><span class="p" data-group-id="6705796952-2">)</span></code></pre><p>Instead:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TerminatedStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1700709592-1">[</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="1700709592-1">]</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">port_command</span><span class="p" data-group-id="1700709592-2">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">TerminatedStr</span><span class="p" data-group-id="1700709592-2">)</span></code></pre><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">append</span><span class="p" data-group-id="3753374938-1">(</span><span class="p" data-group-id="3753374938-2">[</span><span class="p" data-group-id="3753374938-3">[</span><span class="mi">1</span><span class="p" data-group-id="3753374938-3">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3753374938-4">[</span><span class="mi">2</span><span class="p" data-group-id="3753374938-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3753374938-5">[</span><span class="mi">3</span><span class="p" data-group-id="3753374938-5">]</span><span class="p" data-group-id="3753374938-2">]</span><span class="p" data-group-id="3753374938-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3753374938-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3753374938-6">]</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">flatten</span><span class="p" data-group-id="6188522684-1">(</span><span class="p" data-group-id="6188522684-2">[</span><span class="p" data-group-id="6188522684-3">[</span><span class="mi">1</span><span class="p" data-group-id="6188522684-3">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6188522684-4">[</span><span class="mi">2</span><span class="p" data-group-id="6188522684-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6188522684-5">[</span><span class="mi">3</span><span class="p" data-group-id="6188522684-5">]</span><span class="p" data-group-id="6188522684-2">]</span><span class="p" data-group-id="6188522684-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6188522684-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6188522684-6">]</span></code></pre><h2 id="recursive-list-functions" class="section-heading">
│ │ │ +instead.</li></ul><p><em>Examples:</em></p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">port_command</span><span class="p" data-group-id="6002647593-1">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">DeepList</span><span class="p" data-group-id="6002647593-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">port_command</span><span class="p" data-group-id="7462166350-1">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">flatten</span><span class="p" data-group-id="7462166350-2">(</span><span class="n">DeepList</span><span class="p" data-group-id="7462166350-2">)</span><span class="p" data-group-id="7462166350-1">)</span></code></pre><p>A common way to send a zero-terminated string to a port is the following:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TerminatedStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="7394406402-1">[</span><span class="mi">0</span><span class="p" data-group-id="7394406402-1">]</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">port_command</span><span class="p" data-group-id="7394406402-2">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">TerminatedStr</span><span class="p" data-group-id="7394406402-2">)</span></code></pre><p>Instead:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TerminatedStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7326832184-1">[</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="7326832184-1">]</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">port_command</span><span class="p" data-group-id="7326832184-2">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">TerminatedStr</span><span class="p" data-group-id="7326832184-2">)</span></code></pre><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">append</span><span class="p" data-group-id="5112559656-1">(</span><span class="p" data-group-id="5112559656-2">[</span><span class="p" data-group-id="5112559656-3">[</span><span class="mi">1</span><span class="p" data-group-id="5112559656-3">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5112559656-4">[</span><span class="mi">2</span><span class="p" data-group-id="5112559656-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5112559656-5">[</span><span class="mi">3</span><span class="p" data-group-id="5112559656-5">]</span><span class="p" data-group-id="5112559656-2">]</span><span class="p" data-group-id="5112559656-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5112559656-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5112559656-6">]</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">flatten</span><span class="p" data-group-id="0642531108-1">(</span><span class="p" data-group-id="0642531108-2">[</span><span class="p" data-group-id="0642531108-3">[</span><span class="mi">1</span><span class="p" data-group-id="0642531108-3">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0642531108-4">[</span><span class="mi">2</span><span class="p" data-group-id="0642531108-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0642531108-5">[</span><span class="mi">3</span><span class="p" data-group-id="0642531108-5">]</span><span class="p" data-group-id="0642531108-2">]</span><span class="p" data-group-id="0642531108-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0642531108-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0642531108-6">]</span></code></pre><h2 id="recursive-list-functions" class="section-heading">
│ │ │    <a href="#recursive-list-functions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Recursive List Functions</span>
│ │ │  </h2>
│ │ │  <p>There are two basic ways to write a function that traverses a list and
│ │ │  produces a new list.</p><p>The first way is writing a <em>body-recursive</em> function:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% Add 42 to each integer in the list.</span><span class="w">
│ │ │ -</span><span class="nf">add_42_body</span><span class="p" data-group-id="8941869924-1">(</span><span class="p" data-group-id="8941869924-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8941869924-2">]</span><span class="p" data-group-id="8941869924-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8941869924-3">[</span><span class="n">H</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">add_42_body</span><span class="p" data-group-id="8941869924-4">(</span><span class="n">T</span><span class="p" data-group-id="8941869924-4">)</span><span class="p" data-group-id="8941869924-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">add_42_body</span><span class="p" data-group-id="8941869924-5">(</span><span class="p" data-group-id="8941869924-6">[</span><span class="p" data-group-id="8941869924-6">]</span><span class="p" data-group-id="8941869924-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8941869924-7">[</span><span class="p" data-group-id="8941869924-7">]</span><span class="p">.</span></code></pre><p>The second way is writing a <em>tail-recursive</em> function:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% Add 42 to each integer in the list.</span><span class="w">
│ │ │ -</span><span class="nf">add_42_tail</span><span class="p" data-group-id="1839646970-1">(</span><span class="n">List</span><span class="p" data-group-id="1839646970-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">add_42_tail</span><span class="p" data-group-id="1839646970-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1839646970-3">[</span><span class="p" data-group-id="1839646970-3">]</span><span class="p" data-group-id="1839646970-2">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">add_42_tail</span><span class="p" data-group-id="1839646970-4">(</span><span class="p" data-group-id="1839646970-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1839646970-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="1839646970-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">add_42_tail</span><span class="p" data-group-id="1839646970-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1839646970-7">[</span><span class="n">H</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="1839646970-7">]</span><span class="p" data-group-id="1839646970-6">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">add_42_tail</span><span class="p" data-group-id="1839646970-8">(</span><span class="p" data-group-id="1839646970-9">[</span><span class="p" data-group-id="1839646970-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="1839646970-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="1839646970-10">(</span><span class="n">Acc</span><span class="p" data-group-id="1839646970-10">)</span><span class="p">.</span></code></pre><p>In early versions of Erlang the tail-recursive function would typically
│ │ │ +</span><span class="nf">add_42_body</span><span class="p" data-group-id="9442859127-1">(</span><span class="p" data-group-id="9442859127-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9442859127-2">]</span><span class="p" data-group-id="9442859127-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9442859127-3">[</span><span class="n">H</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">add_42_body</span><span class="p" data-group-id="9442859127-4">(</span><span class="n">T</span><span class="p" data-group-id="9442859127-4">)</span><span class="p" data-group-id="9442859127-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">add_42_body</span><span class="p" data-group-id="9442859127-5">(</span><span class="p" data-group-id="9442859127-6">[</span><span class="p" data-group-id="9442859127-6">]</span><span class="p" data-group-id="9442859127-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9442859127-7">[</span><span class="p" data-group-id="9442859127-7">]</span><span class="p">.</span></code></pre><p>The second way is writing a <em>tail-recursive</em> function:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% Add 42 to each integer in the list.</span><span class="w">
│ │ │ +</span><span class="nf">add_42_tail</span><span class="p" data-group-id="4684484741-1">(</span><span class="n">List</span><span class="p" data-group-id="4684484741-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">add_42_tail</span><span class="p" data-group-id="4684484741-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4684484741-3">[</span><span class="p" data-group-id="4684484741-3">]</span><span class="p" data-group-id="4684484741-2">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">add_42_tail</span><span class="p" data-group-id="4684484741-4">(</span><span class="p" data-group-id="4684484741-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4684484741-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="4684484741-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">add_42_tail</span><span class="p" data-group-id="4684484741-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4684484741-7">[</span><span class="n">H</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="4684484741-7">]</span><span class="p" data-group-id="4684484741-6">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">add_42_tail</span><span class="p" data-group-id="4684484741-8">(</span><span class="p" data-group-id="4684484741-9">[</span><span class="p" data-group-id="4684484741-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="4684484741-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="4684484741-10">(</span><span class="n">Acc</span><span class="p" data-group-id="4684484741-10">)</span><span class="p">.</span></code></pre><p>In early versions of Erlang the tail-recursive function would typically
│ │ │  be more efficient. In modern versions of Erlang, there is usually not
│ │ │  much difference in performance between a body-recursive list function and
│ │ │  tail-recursive function that reverses the list at the end. Therefore,
│ │ │  concentrate on writing beautiful code and forget about the performance
│ │ │  of your list functions. In the time-critical parts of your code,
│ │ │  <em>measure</em> before rewriting your code.</p><p>For a thorough discussion about tail and body recursion, see
│ │ │  <a href="http://ferd.ca/erlang-s-tail-recursion-is-not-a-silver-bullet.html">Erlang's Tail Recursion is Not a Silver Bullet</a>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>This section is about list functions that <em>construct</em> lists. A tail-recursive
│ │ │  function that does not construct a list runs in constant space, while the
│ │ │  corresponding body-recursive function uses stack space proportional to the
│ │ │  length of the list.</p></section><p>For example, a function that sums a list of integers, is <em>not</em> to be written as
│ │ │ -follows:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">recursive_sum</span><span class="p" data-group-id="9241865243-1">(</span><span class="p" data-group-id="9241865243-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9241865243-2">]</span><span class="p" data-group-id="9241865243-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">H</span><span class="o">+</span><span class="nf">recursive_sum</span><span class="p" data-group-id="9241865243-3">(</span><span class="n">T</span><span class="p" data-group-id="9241865243-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">recursive_sum</span><span class="p" data-group-id="9241865243-4">(</span><span class="p" data-group-id="9241865243-5">[</span><span class="p" data-group-id="9241865243-5">]</span><span class="p" data-group-id="9241865243-4">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p">.</span></code></pre><p>Instead:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">sum</span><span class="p" data-group-id="5520358443-1">(</span><span class="n">L</span><span class="p" data-group-id="5520358443-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">sum</span><span class="p" data-group-id="5520358443-2">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="5520358443-2">)</span><span class="p">.</span><span class="w">
│ │ │ +follows:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">recursive_sum</span><span class="p" data-group-id="6971190708-1">(</span><span class="p" data-group-id="6971190708-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6971190708-2">]</span><span class="p" data-group-id="6971190708-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">H</span><span class="o">+</span><span class="nf">recursive_sum</span><span class="p" data-group-id="6971190708-3">(</span><span class="n">T</span><span class="p" data-group-id="6971190708-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">recursive_sum</span><span class="p" data-group-id="6971190708-4">(</span><span class="p" data-group-id="6971190708-5">[</span><span class="p" data-group-id="6971190708-5">]</span><span class="p" data-group-id="6971190708-4">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p">.</span></code></pre><p>Instead:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">sum</span><span class="p" data-group-id="6829975409-1">(</span><span class="n">L</span><span class="p" data-group-id="6829975409-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">sum</span><span class="p" data-group-id="6829975409-2">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="6829975409-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">sum</span><span class="p" data-group-id="5520358443-3">(</span><span class="p" data-group-id="5520358443-4">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5520358443-4">]</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="5520358443-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">sum</span><span class="p" data-group-id="5520358443-5">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">H</span><span class="p" data-group-id="5520358443-5">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">sum</span><span class="p" data-group-id="5520358443-6">(</span><span class="p" data-group-id="5520358443-7">[</span><span class="p" data-group-id="5520358443-7">]</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="5520358443-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Sum</span><span class="p">.</span></code></pre>
│ │ │ +</span><span class="nf">sum</span><span class="p" data-group-id="6829975409-3">(</span><span class="p" data-group-id="6829975409-4">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6829975409-4">]</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="6829975409-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">sum</span><span class="p" data-group-id="6829975409-5">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">H</span><span class="p" data-group-id="6829975409-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">sum</span><span class="p" data-group-id="6829975409-6">(</span><span class="p" data-group-id="6829975409-7">[</span><span class="p" data-group-id="6829975409-7">]</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="6829975409-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Sum</span><span class="p">.</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="maps.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/macros.html
│ │ │ @@ -117,56 +117,56 @@
│ │ │  
│ │ │  <h2 id="file-inclusion" class="section-heading">
│ │ │    <a href="#file-inclusion" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">File Inclusion</span>
│ │ │  </h2>
│ │ │ -<p>A file can be included as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="9714163379-1">(</span><span class="n">File</span><span class="p" data-group-id="9714163379-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="9714163379-2">(</span><span class="n">File</span><span class="p" data-group-id="9714163379-2">)</span><span class="p">.</span></code></pre><p><code class="inline">File</code>, a string, is to point out a file. The contents of this file are included
│ │ │ +<p>A file can be included as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="3583819895-1">(</span><span class="n">File</span><span class="p" data-group-id="3583819895-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="3583819895-2">(</span><span class="n">File</span><span class="p" data-group-id="3583819895-2">)</span><span class="p">.</span></code></pre><p><code class="inline">File</code>, a string, is to point out a file. The contents of this file are included
│ │ │  as is, at the position of the directive.</p><p>Include files are typically used for record and macro definitions that are
│ │ │  shared by several modules. It is recommended to use the file name extension
│ │ │  <code class="inline">.hrl</code> for include files.</p><p><code class="inline">File</code> can start with a path component <code class="inline">$VAR</code>, for some string <code class="inline">VAR</code>. If that is
│ │ │  the case, the value of the environment variable <code class="inline">VAR</code> as returned by
│ │ │  <code class="inline">os:getenv(VAR)</code> is substituted for <code class="inline">$VAR</code>. If <code class="inline">os:getenv(VAR)</code> returns <code class="inline">false</code>,
│ │ │  <code class="inline">$VAR</code> is left as is.</p><p>If the filename <code class="inline">File</code> is absolute (possibly after variable substitution), the
│ │ │  include file with that name is included. Otherwise, the specified file is
│ │ │  searched for in the following directories, and in this order:</p><ol><li>The current working directory</li><li>The directory where the module is being compiled</li><li>The directories given by the <code class="inline">include</code> option</li></ol><p>For details, see <a href="../../erts-17.0/doc/html/erlc_cmd.html">erlc</a> in ERTS and
│ │ │ -<a href="../../lib/compiler-10.0/doc/html/compile.html"><code class="inline">compile</code></a> in Compiler.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="6830195681-1">(</span><span class="s">&quot;my_records.hrl&quot;</span><span class="p" data-group-id="6830195681-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="6830195681-2">(</span><span class="s">&quot;incdir/my_records.hrl&quot;</span><span class="p" data-group-id="6830195681-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="6830195681-3">(</span><span class="s">&quot;/home/user/proj/my_records.hrl&quot;</span><span class="p" data-group-id="6830195681-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="6830195681-4">(</span><span class="s">&quot;$PROJ_ROOT/my_records.hrl&quot;</span><span class="p" data-group-id="6830195681-4">)</span><span class="p">.</span></code></pre><p><code class="inline">include_lib</code> is similar to <code class="inline">include</code>, but is not to point out an absolute file.
│ │ │ +<a href="../../lib/compiler-10.0/doc/html/compile.html"><code class="inline">compile</code></a> in Compiler.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="2017056727-1">(</span><span class="s">&quot;my_records.hrl&quot;</span><span class="p" data-group-id="2017056727-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="2017056727-2">(</span><span class="s">&quot;incdir/my_records.hrl&quot;</span><span class="p" data-group-id="2017056727-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="2017056727-3">(</span><span class="s">&quot;/home/user/proj/my_records.hrl&quot;</span><span class="p" data-group-id="2017056727-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="2017056727-4">(</span><span class="s">&quot;$PROJ_ROOT/my_records.hrl&quot;</span><span class="p" data-group-id="2017056727-4">)</span><span class="p">.</span></code></pre><p><code class="inline">include_lib</code> is similar to <code class="inline">include</code>, but is not to point out an absolute file.
│ │ │  Instead, the first path component (possibly after variable substitution) is
│ │ │ -assumed to be the name of an application.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="6128413310-1">(</span><span class="s">&quot;kernel/include/file.hrl&quot;</span><span class="p" data-group-id="6128413310-1">)</span><span class="p">.</span></code></pre><p>The code server uses <code class="inline">code:lib_dir(kernel)</code> to find the directory of the current
│ │ │ +assumed to be the name of an application.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="3067597583-1">(</span><span class="s">&quot;kernel/include/file.hrl&quot;</span><span class="p" data-group-id="3067597583-1">)</span><span class="p">.</span></code></pre><p>The code server uses <code class="inline">code:lib_dir(kernel)</code> to find the directory of the current
│ │ │  (latest) version of Kernel, and then the subdirectory <code class="inline">include</code> is searched for
│ │ │  the file <code class="inline">file.hrl</code>.</p><h2 id="defining-and-using-macros" class="section-heading">
│ │ │    <a href="#defining-and-using-macros" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Defining and Using Macros</span>
│ │ │  </h2>
│ │ │ -<p>A macro is defined as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7523163634-1">(</span><span class="n">Const</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="7523163634-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7523163634-2">(</span><span class="n">Func</span><span class="p" data-group-id="7523163634-3">(</span><span class="n">Var1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">VarN</span><span class="p" data-group-id="7523163634-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="7523163634-2">)</span><span class="p">.</span></code></pre><p>A macro definition can be placed anywhere among the attributes and function
│ │ │ +<p>A macro is defined as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3990685156-1">(</span><span class="n">Const</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="3990685156-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3990685156-2">(</span><span class="n">Func</span><span class="p" data-group-id="3990685156-3">(</span><span class="n">Var1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">VarN</span><span class="p" data-group-id="3990685156-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="3990685156-2">)</span><span class="p">.</span></code></pre><p>A macro definition can be placed anywhere among the attributes and function
│ │ │  declarations of a module, but the definition must come before any usage of the
│ │ │  macro.</p><p>If a macro is used in several modules, it is recommended that the macro
│ │ │  definition is placed in an include file.</p><p>A macro is used as follows:</p><pre><code class="text">?Const
│ │ │  ?Func(Arg1,...,ArgN)</code></pre><p>Macros are expanded during compilation. A simple macro <code class="inline">?Const</code> is replaced with
│ │ │ -<code class="inline">Replacement</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2755769274-1">(</span><span class="n">TIMEOUT</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p" data-group-id="2755769274-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">Replacement</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="1230578048-1">(</span><span class="n">TIMEOUT</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p" data-group-id="1230578048-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">call</span><span class="p" data-group-id="2755769274-2">(</span><span class="n">Request</span><span class="p" data-group-id="2755769274-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="2755769274-3">(</span><span class="ss">refserver</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">TIMEOUT</span><span class="p" data-group-id="2755769274-3">)</span><span class="p">.</span></code></pre><p>This is expanded to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">call</span><span class="p" data-group-id="1457618736-1">(</span><span class="n">Request</span><span class="p" data-group-id="1457618736-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="1457618736-2">(</span><span class="ss">refserver</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p" data-group-id="1457618736-2">)</span><span class="p">.</span></code></pre><p>A macro <code class="inline">?Func(Arg1,...,ArgN)</code> is replaced with <code class="inline">Replacement</code>, where all
│ │ │ +</span><span class="nf">call</span><span class="p" data-group-id="1230578048-2">(</span><span class="n">Request</span><span class="p" data-group-id="1230578048-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="1230578048-3">(</span><span class="ss">refserver</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">TIMEOUT</span><span class="p" data-group-id="1230578048-3">)</span><span class="p">.</span></code></pre><p>This is expanded to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">call</span><span class="p" data-group-id="3309158374-1">(</span><span class="n">Request</span><span class="p" data-group-id="3309158374-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="3309158374-2">(</span><span class="ss">refserver</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p" data-group-id="3309158374-2">)</span><span class="p">.</span></code></pre><p>A macro <code class="inline">?Func(Arg1,...,ArgN)</code> is replaced with <code class="inline">Replacement</code>, where all
│ │ │  occurrences of a variable <code class="inline">Var</code> from the macro definition are replaced with the
│ │ │ -corresponding argument <code class="inline">Arg</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6116097759-1">(</span><span class="n">MACRO1</span><span class="p" data-group-id="6116097759-2">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6116097759-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6116097759-3">{</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6116097759-3">}</span><span class="p" data-group-id="6116097759-1">)</span><span class="p">.</span><span class="w">
│ │ │ +corresponding argument <code class="inline">Arg</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6413728321-1">(</span><span class="n">MACRO1</span><span class="p" data-group-id="6413728321-2">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6413728321-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6413728321-3">{</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6413728321-3">}</span><span class="p" data-group-id="6413728321-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="6116097759-4">(</span><span class="n">X</span><span class="p" data-group-id="6116097759-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="o">?</span><span class="n">MACRO1</span><span class="p" data-group-id="6116097759-5">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="6116097759-5">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="o">?</span><span class="n">MACRO1</span><span class="p" data-group-id="6116097759-6">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="mi">123</span><span class="p" data-group-id="6116097759-6">)</span></code></pre><p>This is expanded to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="9621410301-1">(</span><span class="n">X</span><span class="p" data-group-id="9621410301-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9621410301-2">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9621410301-2">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9621410301-3">{</span><span class="ss">a</span><span class="p">,</span><span class="n">X</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">123</span><span class="p" data-group-id="9621410301-3">}</span><span class="p">.</span></code></pre><p>It is good programming practice, but not mandatory, to ensure that a macro
│ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="6413728321-4">(</span><span class="n">X</span><span class="p" data-group-id="6413728321-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="o">?</span><span class="n">MACRO1</span><span class="p" data-group-id="6413728321-5">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="6413728321-5">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="o">?</span><span class="n">MACRO1</span><span class="p" data-group-id="6413728321-6">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="mi">123</span><span class="p" data-group-id="6413728321-6">)</span></code></pre><p>This is expanded to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="9763378592-1">(</span><span class="n">X</span><span class="p" data-group-id="9763378592-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9763378592-2">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9763378592-2">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9763378592-3">{</span><span class="ss">a</span><span class="p">,</span><span class="n">X</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">123</span><span class="p" data-group-id="9763378592-3">}</span><span class="p">.</span></code></pre><p>It is good programming practice, but not mandatory, to ensure that a macro
│ │ │  definition is a valid Erlang syntactic form.</p><p>To view the result of macro expansion, a module can be compiled with the <code class="inline">'P'</code>
│ │ │  option. <code class="inline">compile:file(File, ['P'])</code>. This produces a listing of the parsed code
│ │ │  after preprocessing and parse transforms, in the file <code class="inline">File.P</code>.</p><h2 id="predefined-macros" class="section-heading">
│ │ │    <a href="#predefined-macros" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Predefined Macros</span>
│ │ │ @@ -185,29 +185,29 @@
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Macro Overloading</span>
│ │ │  </h2>
│ │ │  <p>It is possible to overload macros, except for predefined macros. An overloaded
│ │ │  macro has more than one definition, each with a different number of arguments.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Support for overloading of macros was added in Erlang 5.7.5/OTP R13B04.</p></section><p>A macro <code class="inline">?Func(Arg1,...,ArgN)</code> with a (possibly empty) list of arguments results
│ │ │  in an error message if there is at least one definition of <code class="inline">Func</code> with
│ │ │ -arguments, but none with N arguments.</p><p>Assuming these definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5625195419-1">(</span><span class="n">F0</span><span class="p" data-group-id="5625195419-2">(</span><span class="p" data-group-id="5625195419-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="5625195419-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5625195419-3">(</span><span class="n">F1</span><span class="p" data-group-id="5625195419-4">(</span><span class="n">A</span><span class="p" data-group-id="5625195419-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="5625195419-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5625195419-5">(</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="nc">m</span><span class="p">:</span><span class="ss">f</span><span class="p" data-group-id="5625195419-5">)</span><span class="p">.</span></code></pre><p>the following does not work:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f0</span><span class="p" data-group-id="3860117093-1">(</span><span class="p" data-group-id="3860117093-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +arguments, but none with N arguments.</p><p>Assuming these definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5182514384-1">(</span><span class="n">F0</span><span class="p" data-group-id="5182514384-2">(</span><span class="p" data-group-id="5182514384-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="5182514384-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5182514384-3">(</span><span class="n">F1</span><span class="p" data-group-id="5182514384-4">(</span><span class="n">A</span><span class="p" data-group-id="5182514384-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="5182514384-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5182514384-5">(</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="nc">m</span><span class="p">:</span><span class="ss">f</span><span class="p" data-group-id="5182514384-5">)</span><span class="p">.</span></code></pre><p>the following does not work:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f0</span><span class="p" data-group-id="8460003082-1">(</span><span class="p" data-group-id="8460003082-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="o">?</span><span class="n">F0</span><span class="p">.</span><span class="w"> </span><span class="c1">% No, an empty list of arguments expected.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">f1</span><span class="p" data-group-id="3860117093-2">(</span><span class="n">A</span><span class="p" data-group-id="3860117093-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="o">?</span><span class="n">F1</span><span class="p" data-group-id="3860117093-3">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="3860117093-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% No, exactly one argument expected.</span></code></pre><p>On the other hand,</p><pre><code class="text">f() -&gt;
│ │ │ -    ?C().</code></pre><p>is expanded to</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="7005949606-1">(</span><span class="p" data-group-id="7005949606-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">m</span><span class="p">:</span><span class="nf">f</span><span class="p" data-group-id="7005949606-2">(</span><span class="p" data-group-id="7005949606-2">)</span><span class="p">.</span></code></pre><h2 id="removing-a-macro-definition" class="section-heading">
│ │ │ +</span><span class="nf">f1</span><span class="p" data-group-id="8460003082-2">(</span><span class="n">A</span><span class="p" data-group-id="8460003082-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="o">?</span><span class="n">F1</span><span class="p" data-group-id="8460003082-3">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="8460003082-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% No, exactly one argument expected.</span></code></pre><p>On the other hand,</p><pre><code class="text">f() -&gt;
│ │ │ +    ?C().</code></pre><p>is expanded to</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="7633725853-1">(</span><span class="p" data-group-id="7633725853-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">m</span><span class="p">:</span><span class="nf">f</span><span class="p" data-group-id="7633725853-2">(</span><span class="p" data-group-id="7633725853-2">)</span><span class="p">.</span></code></pre><h2 id="removing-a-macro-definition" class="section-heading">
│ │ │    <a href="#removing-a-macro-definition" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Removing a macro definition</span>
│ │ │  </h2>
│ │ │ -<p>A definition of a macro can be removed as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">undef</span><span class="p" data-group-id="0957393952-1">(</span><span class="n">Macro</span><span class="p" data-group-id="0957393952-1">)</span><span class="p">.</span></code></pre><h2 id="conditional-compilation" class="section-heading">
│ │ │ +<p>A definition of a macro can be removed as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">undef</span><span class="p" data-group-id="2039789082-1">(</span><span class="n">Macro</span><span class="p" data-group-id="2039789082-1">)</span><span class="p">.</span></code></pre><h2 id="conditional-compilation" class="section-heading">
│ │ │    <a href="#conditional-compilation" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Conditional Compilation</span>
│ │ │  </h2>
│ │ │  <p>The following macro directives support conditional compilation:</p><ul><li><p><strong><code class="inline">-ifdef(Macro).</code></strong> - Evaluate the following lines only if <code class="inline">Macro</code> is
│ │ │  defined.</p></li><li><p><strong><code class="inline">-ifndef(Macro).</code></strong> - Evaluate the following lines only if <code class="inline">Macro</code> is not
│ │ │ @@ -219,43 +219,43 @@
│ │ │  true, and the <code class="inline">Condition</code> evaluates to true, the lines following the <code class="inline">elif</code>
│ │ │  are evaluated instead.</p></li><li><p><strong><code class="inline">-endif.</code></strong> - Specifies the end of a series of control flow directives.</p></li></ul><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Macro directives cannot be used inside functions.</p></section><p>Syntactically, the <code class="inline">Condition</code> in <code class="inline">if</code> and <code class="inline">elif</code> must be a
│ │ │  <a href="expressions.html#guard-expressions">guard expression</a>. Other constructs (such as
│ │ │  a <code class="inline">case</code> expression) result in a compilation error.</p><p>As opposed to the standard guard expressions, an expression in an <code class="inline">if</code> and
│ │ │  <code class="inline">elif</code> also supports calling the pseudo-function <code class="inline">defined(Name)</code>, which tests
│ │ │  whether the <code class="inline">Name</code> argument is the name of a previously defined macro.
│ │ │  <code class="inline">defined(Name)</code> evaluates to <code class="inline">true</code> if the macro is defined and <code class="inline">false</code>
│ │ │ -otherwise. An attempt to call other functions results in a compilation error.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2809672954-1">(</span><span class="ss">m</span><span class="p" data-group-id="2809672954-1">)</span><span class="p">.</span><span class="w">
│ │ │ +otherwise. An attempt to call other functions results in a compilation error.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8077497684-1">(</span><span class="ss">m</span><span class="p" data-group-id="8077497684-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">ifdef</span><span class="p" data-group-id="2809672954-2">(</span><span class="ss">debug</span><span class="p" data-group-id="2809672954-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2809672954-3">(</span><span class="n">LOG</span><span class="p" data-group-id="2809672954-4">(</span><span class="n">X</span><span class="p" data-group-id="2809672954-4">)</span><span class="p">,</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2809672954-5">(</span><span class="s">&quot;{</span><span class="si">~p</span><span class="s">,</span><span class="si">~p</span><span class="s">}: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2809672954-6">[</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="o">?</span><span class="n">LINE</span><span class="p">,</span><span class="n">X</span><span class="p" data-group-id="2809672954-6">]</span><span class="p" data-group-id="2809672954-5">)</span><span class="p" data-group-id="2809672954-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">ifdef</span><span class="p" data-group-id="8077497684-2">(</span><span class="ss">debug</span><span class="p" data-group-id="8077497684-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8077497684-3">(</span><span class="n">LOG</span><span class="p" data-group-id="8077497684-4">(</span><span class="n">X</span><span class="p" data-group-id="8077497684-4">)</span><span class="p">,</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8077497684-5">(</span><span class="s">&quot;{</span><span class="si">~p</span><span class="s">,</span><span class="si">~p</span><span class="s">}: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8077497684-6">[</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="o">?</span><span class="n">LINE</span><span class="p">,</span><span class="n">X</span><span class="p" data-group-id="8077497684-6">]</span><span class="p" data-group-id="8077497684-5">)</span><span class="p" data-group-id="8077497684-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">else</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2809672954-7">(</span><span class="n">LOG</span><span class="p" data-group-id="2809672954-8">(</span><span class="n">X</span><span class="p" data-group-id="2809672954-8">)</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="2809672954-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8077497684-7">(</span><span class="n">LOG</span><span class="p" data-group-id="8077497684-8">(</span><span class="n">X</span><span class="p" data-group-id="8077497684-8">)</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="8077497684-7">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>When trace output is desired, <code class="inline">debug</code> is to be defined when the module <code class="inline">m</code> is
│ │ │  compiled:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erlc -Ddebug m.erl</span><span class="w">
│ │ │  
│ │ │  </span><span class="ow">or</span><span class="w">
│ │ │  
│ │ │ -</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">c</span><span class="p" data-group-id="3775132551-1">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3775132551-2">{</span><span class="ss">d</span><span class="p">,</span><span class="w"> </span><span class="ss">debug</span><span class="p" data-group-id="3775132551-2">}</span><span class="p" data-group-id="3775132551-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3775132551-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">m</span><span class="p" data-group-id="3775132551-3">}</span></code></pre><p><code class="inline">?LOG(Arg)</code> is then expanded to a call to <a href="../../lib/stdlib-8.0/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> and provides the user
│ │ │ -with some simple trace output.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6899834278-1">(</span><span class="ss">m</span><span class="p" data-group-id="6899834278-1">)</span><span class="w">
│ │ │ +</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">c</span><span class="p" data-group-id="6989593508-1">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6989593508-2">{</span><span class="ss">d</span><span class="p">,</span><span class="w"> </span><span class="ss">debug</span><span class="p" data-group-id="6989593508-2">}</span><span class="p" data-group-id="6989593508-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6989593508-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">m</span><span class="p" data-group-id="6989593508-3">}</span></code></pre><p><code class="inline">?LOG(Arg)</code> is then expanded to a call to <a href="../../lib/stdlib-8.0/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> and provides the user
│ │ │ +with some simple trace output.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8995851663-1">(</span><span class="ss">m</span><span class="p" data-group-id="8995851663-1">)</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">if</span><span class="p" data-group-id="6899834278-2">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">26</span><span class="p" data-group-id="6899834278-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">if</span><span class="p" data-group-id="8995851663-2">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">26</span><span class="p" data-group-id="8995851663-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% Code that will work in OTP 26 or higher</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">elif</span><span class="p" data-group-id="6899834278-3">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">25</span><span class="p" data-group-id="6899834278-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">elif</span><span class="p" data-group-id="8995851663-3">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">25</span><span class="p" data-group-id="8995851663-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% Code that will work in OTP 25 or higher</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">else</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% Code that will work in OTP 24 or lower.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>This code uses the <code class="inline">OTP_RELEASE</code> macro to conditionally select code depending on
│ │ │ -release.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8411080138-1">(</span><span class="ss">m</span><span class="p" data-group-id="8411080138-1">)</span><span class="w">
│ │ │ +release.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7447289919-1">(</span><span class="ss">m</span><span class="p" data-group-id="7447289919-1">)</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">if</span><span class="p" data-group-id="8411080138-2">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">defined</span><span class="p" data-group-id="8411080138-3">(</span><span class="ss">debug</span><span class="p" data-group-id="8411080138-3">)</span><span class="p" data-group-id="8411080138-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">if</span><span class="p" data-group-id="7447289919-2">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">defined</span><span class="p" data-group-id="7447289919-3">(</span><span class="ss">debug</span><span class="p" data-group-id="7447289919-3">)</span><span class="p" data-group-id="7447289919-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% Debugging code that requires OTP 26 or later.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">else</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% Non-debug code that works in any release.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>This code uses the <code class="inline">OTP_RELEASE</code> macro and <code class="inline">defined(debug)</code> to compile debug
│ │ │  code only for OTP 26 or later.</p><h2 id="the-feature-directive" class="section-heading">
│ │ │    <a href="#the-feature-directive" class="hover-link">
│ │ │ @@ -270,44 +270,44 @@
│ │ │  used. In practice this means it should appear before any <code class="inline">-export(..)</code> or record
│ │ │  definitions.</p><h2 id="error-and-warning-directives" class="section-heading">
│ │ │    <a href="#error-and-warning-directives" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">-error() and -warning() directives</span>
│ │ │  </h2>
│ │ │ -<p>The directive <code class="inline">-error(Term)</code> causes a compilation error.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7367553004-1">(</span><span class="ss">t</span><span class="p" data-group-id="7367553004-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7367553004-2">(</span><span class="p" data-group-id="7367553004-3">[</span><span class="ss">version</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7367553004-3">]</span><span class="p" data-group-id="7367553004-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>The directive <code class="inline">-error(Term)</code> causes a compilation error.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7380997339-1">(</span><span class="ss">t</span><span class="p" data-group-id="7380997339-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7380997339-2">(</span><span class="p" data-group-id="7380997339-3">[</span><span class="ss">version</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7380997339-3">]</span><span class="p" data-group-id="7380997339-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">ifdef</span><span class="p" data-group-id="7367553004-4">(</span><span class="n">VERSION</span><span class="p" data-group-id="7367553004-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">version</span><span class="p" data-group-id="7367553004-5">(</span><span class="p" data-group-id="7367553004-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VERSION</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">ifdef</span><span class="p" data-group-id="7380997339-4">(</span><span class="n">VERSION</span><span class="p" data-group-id="7380997339-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">version</span><span class="p" data-group-id="7380997339-5">(</span><span class="p" data-group-id="7380997339-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VERSION</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">else</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">error</span><span class="p" data-group-id="7367553004-6">(</span><span class="s">&quot;Macro VERSION must be defined.&quot;</span><span class="p" data-group-id="7367553004-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">version</span><span class="p" data-group-id="7367553004-7">(</span><span class="p" data-group-id="7367553004-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">error</span><span class="p" data-group-id="7380997339-6">(</span><span class="s">&quot;Macro VERSION must be defined.&quot;</span><span class="p" data-group-id="7380997339-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">version</span><span class="p" data-group-id="7380997339-7">(</span><span class="p" data-group-id="7380997339-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span></code></pre><p>The error message will look like this:</p><pre><code class="text">% erlc t.erl
│ │ │ -t.erl:7: -error(&quot;Macro VERSION must be defined.&quot;).</code></pre><p>The directive <code class="inline">-warning(Term)</code> causes a compilation warning.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1205982404-1">(</span><span class="ss">t</span><span class="p" data-group-id="1205982404-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1205982404-2">(</span><span class="p" data-group-id="1205982404-3">[</span><span class="ss">version</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1205982404-3">]</span><span class="p" data-group-id="1205982404-2">)</span><span class="p">.</span><span class="w">
│ │ │ +t.erl:7: -error(&quot;Macro VERSION must be defined.&quot;).</code></pre><p>The directive <code class="inline">-warning(Term)</code> causes a compilation warning.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1045072016-1">(</span><span class="ss">t</span><span class="p" data-group-id="1045072016-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1045072016-2">(</span><span class="p" data-group-id="1045072016-3">[</span><span class="ss">version</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1045072016-3">]</span><span class="p" data-group-id="1045072016-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">ifndef</span><span class="p" data-group-id="1205982404-4">(</span><span class="n">VERSION</span><span class="p" data-group-id="1205982404-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">warning</span><span class="p" data-group-id="1205982404-5">(</span><span class="s">&quot;Macro VERSION not defined -- using default version.&quot;</span><span class="p" data-group-id="1205982404-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="1205982404-6">(</span><span class="n">VERSION</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;0&quot;</span><span class="p" data-group-id="1205982404-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">ifndef</span><span class="p" data-group-id="1045072016-4">(</span><span class="n">VERSION</span><span class="p" data-group-id="1045072016-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">warning</span><span class="p" data-group-id="1045072016-5">(</span><span class="s">&quot;Macro VERSION not defined -- using default version.&quot;</span><span class="p" data-group-id="1045072016-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="1045072016-6">(</span><span class="n">VERSION</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;0&quot;</span><span class="p" data-group-id="1045072016-6">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">version</span><span class="p" data-group-id="1205982404-7">(</span><span class="p" data-group-id="1205982404-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VERSION</span><span class="p">.</span></code></pre><p>The warning message will look like this:</p><pre><code class="text">% erlc t.erl
│ │ │ +</span><span class="nf">version</span><span class="p" data-group-id="1045072016-7">(</span><span class="p" data-group-id="1045072016-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VERSION</span><span class="p">.</span></code></pre><p>The warning message will look like this:</p><pre><code class="text">% erlc t.erl
│ │ │  t.erl:5: Warning: -warning(&quot;Macro VERSION not defined -- using default version.&quot;).</code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>The <code class="inline">-error()</code> and <code class="inline">-warning()</code> directives were added in Erlang/OTP 19.</p></section><h2 id="stringifying-macro-arguments" class="section-heading">
│ │ │    <a href="#stringifying-macro-arguments" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Stringifying Macro Arguments</span>
│ │ │  </h2>
│ │ │  <p>The construction <code class="inline">??Arg</code>, where <code class="inline">Arg</code> is a macro argument, is expanded to a
│ │ │  string containing the tokens of the argument. This is similar to the <code class="inline">#arg</code>
│ │ │ -stringifying construction in C.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6891485757-1">(</span><span class="n">TESTCALL</span><span class="p" data-group-id="6891485757-2">(</span><span class="n">Call</span><span class="p" data-group-id="6891485757-2">)</span><span class="p">,</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6891485757-3">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6891485757-4">[</span><span class="o">?</span><span class="o">?</span><span class="n">Call</span><span class="p">,</span><span class="w"> </span><span class="n">Call</span><span class="p" data-group-id="6891485757-4">]</span><span class="p" data-group-id="6891485757-3">)</span><span class="p" data-group-id="6891485757-1">)</span><span class="p">.</span><span class="w">
│ │ │ +stringifying construction in C.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3272348924-1">(</span><span class="n">TESTCALL</span><span class="p" data-group-id="3272348924-2">(</span><span class="n">Call</span><span class="p" data-group-id="3272348924-2">)</span><span class="p">,</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3272348924-3">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3272348924-4">[</span><span class="o">?</span><span class="o">?</span><span class="n">Call</span><span class="p">,</span><span class="w"> </span><span class="n">Call</span><span class="p" data-group-id="3272348924-4">]</span><span class="p" data-group-id="3272348924-3">)</span><span class="p" data-group-id="3272348924-1">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="o">?</span><span class="n">TESTCALL</span><span class="p" data-group-id="6891485757-5">(</span><span class="nf">myfunction</span><span class="p" data-group-id="6891485757-6">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6891485757-6">)</span><span class="p" data-group-id="6891485757-5">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="o">?</span><span class="n">TESTCALL</span><span class="p" data-group-id="6891485757-7">(</span><span class="nc">you</span><span class="p">:</span><span class="nf">function</span><span class="p" data-group-id="6891485757-8">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6891485757-8">)</span><span class="p" data-group-id="6891485757-7">)</span><span class="p">.</span></code></pre><p>results in</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6641005635-1">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="6641005635-2">[</span><span class="s">&quot;myfunction ( 1 , 2 )&quot;</span><span class="p">,</span><span class="nf">myfunction</span><span class="p" data-group-id="6641005635-3">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6641005635-3">)</span><span class="p" data-group-id="6641005635-2">]</span><span class="p" data-group-id="6641005635-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6641005635-4">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="6641005635-5">[</span><span class="s">&quot;you : function ( 2 , 1 )&quot;</span><span class="p">,</span><span class="nc">you</span><span class="p">:</span><span class="nf">function</span><span class="p" data-group-id="6641005635-6">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6641005635-6">)</span><span class="p" data-group-id="6641005635-5">]</span><span class="p" data-group-id="6641005635-4">)</span><span class="p">.</span></code></pre><p>That is, a trace output, with both the function called and the resulting value.</p>
│ │ │ +</span><span class="o">?</span><span class="n">TESTCALL</span><span class="p" data-group-id="3272348924-5">(</span><span class="nf">myfunction</span><span class="p" data-group-id="3272348924-6">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3272348924-6">)</span><span class="p" data-group-id="3272348924-5">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="o">?</span><span class="n">TESTCALL</span><span class="p" data-group-id="3272348924-7">(</span><span class="nc">you</span><span class="p">:</span><span class="nf">function</span><span class="p" data-group-id="3272348924-8">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3272348924-8">)</span><span class="p" data-group-id="3272348924-7">)</span><span class="p">.</span></code></pre><p>results in</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2593580919-1">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="2593580919-2">[</span><span class="s">&quot;myfunction ( 1 , 2 )&quot;</span><span class="p">,</span><span class="nf">myfunction</span><span class="p" data-group-id="2593580919-3">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2593580919-3">)</span><span class="p" data-group-id="2593580919-2">]</span><span class="p" data-group-id="2593580919-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2593580919-4">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="2593580919-5">[</span><span class="s">&quot;you : function ( 2 , 1 )&quot;</span><span class="p">,</span><span class="nc">you</span><span class="p">:</span><span class="nf">function</span><span class="p" data-group-id="2593580919-6">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2593580919-6">)</span><span class="p" data-group-id="2593580919-5">]</span><span class="p" data-group-id="2593580919-4">)</span><span class="p">.</span></code></pre><p>That is, a trace output, with both the function called and the resulting value.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="expressions.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/maps.html
│ │ │ @@ -148,16 +148,16 @@
│ │ │  single function that constructs the map using the map syntax and always use
│ │ │  it.</p></li><li><p>Always update the map using the <code class="inline">:=</code> operator (that is, requiring that an
│ │ │  element with that key already exists). The <code class="inline">:=</code> operator is slightly more
│ │ │  efficient, and it helps catch misspellings of keys.</p></li><li><p>Whenever possible, match multiple map elements at once.</p></li><li><p>Whenever possible, update multiple map elements at once.</p></li><li><p>Avoid default values and the <a href="../../lib/stdlib-8.0/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a> function. If there are default
│ │ │  values, sharing of keys between different instances of the map will be less
│ │ │  effective, and it is not possible to match multiple elements having default
│ │ │  values in one go.</p></li><li><p>To avoid having to deal with a map that may lack some keys, <a href="../../lib/stdlib-8.0/doc/html/maps.html#merge/2"><code class="inline">maps:merge/2</code></a> can
│ │ │ -efficiently add multiple default values. For example:</p><pre><code class="makeup erlang" translate="no"><span class="n">DefaultMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5443263540-1">#{</span><span class="ss">shoe_size</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w"> </span><span class="ss">editor</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">emacs</span><span class="p" data-group-id="5443263540-1">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">MapWithDefaultsApplied</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">merge</span><span class="p" data-group-id="5443263540-2">(</span><span class="n">DefaultMap</span><span class="p">,</span><span class="w"> </span><span class="n">OtherMap</span><span class="p" data-group-id="5443263540-2">)</span></code></pre></li></ul><h2 id="using-maps-as-dictionaries" class="section-heading">
│ │ │ +efficiently add multiple default values. For example:</p><pre><code class="makeup erlang" translate="no"><span class="n">DefaultMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4117928015-1">#{</span><span class="ss">shoe_size</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w"> </span><span class="ss">editor</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">emacs</span><span class="p" data-group-id="4117928015-1">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">MapWithDefaultsApplied</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">merge</span><span class="p" data-group-id="4117928015-2">(</span><span class="n">DefaultMap</span><span class="p">,</span><span class="w"> </span><span class="n">OtherMap</span><span class="p" data-group-id="4117928015-2">)</span></code></pre></li></ul><h2 id="using-maps-as-dictionaries" class="section-heading">
│ │ │    <a href="#using-maps-as-dictionaries" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Using Maps as Dictionaries</span>
│ │ │  </h2>
│ │ │  <p>Using a map as a dictionary implies the following usage pattern:</p><ul><li>Keys are usually variables not known at compile-time.</li><li>There can be any number of elements in the map.</li><li>Usually, no more than one element is looked up or updated at once.</li></ul><p>Given that usage pattern, the difference in performance between using the map
│ │ │  syntax and the maps module is usually small. Therefore, which one to use is
│ │ │ @@ -167,18 +167,18 @@
│ │ │  choice.</li></ul><h2 id="using-maps-as-sets" class="section-heading">
│ │ │    <a href="#using-maps-as-sets" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Using Maps as Sets</span>
│ │ │  </h2>
│ │ │  <p>Starting in OTP 24, the <a href="../../lib/stdlib-8.0/doc/html/sets.html"><code class="inline">sets</code></a> module has an option to represent sets as maps.
│ │ │ -Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">sets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="5247707496-1">(</span><span class="p" data-group-id="5247707496-2">[</span><span class="p" data-group-id="5247707496-3">{</span><span class="ss">version</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5247707496-3">}</span><span class="p" data-group-id="5247707496-2">]</span><span class="p" data-group-id="5247707496-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5247707496-4">#{</span><span class="p" data-group-id="5247707496-4">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">sets</span><span class="p">:</span><span class="nf">from_list</span><span class="p" data-group-id="5247707496-5">(</span><span class="p" data-group-id="5247707496-6">[</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="5247707496-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5247707496-7">[</span><span class="p" data-group-id="5247707496-8">{</span><span class="ss">version</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5247707496-8">}</span><span class="p" data-group-id="5247707496-7">]</span><span class="p" data-group-id="5247707496-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5247707496-9">#{</span><span class="ss">x</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5247707496-10">[</span><span class="p" data-group-id="5247707496-10">]</span><span class="p">,</span><span class="ss">y</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5247707496-11">[</span><span class="p" data-group-id="5247707496-11">]</span><span class="p">,</span><span class="ss">z</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5247707496-12">[</span><span class="p" data-group-id="5247707496-12">]</span><span class="p" data-group-id="5247707496-9">}</span></code></pre><p><code class="inline">sets</code> backed by maps is generally the most efficient set representation, with a
│ │ │ +Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">sets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="8194616100-1">(</span><span class="p" data-group-id="8194616100-2">[</span><span class="p" data-group-id="8194616100-3">{</span><span class="ss">version</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8194616100-3">}</span><span class="p" data-group-id="8194616100-2">]</span><span class="p" data-group-id="8194616100-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8194616100-4">#{</span><span class="p" data-group-id="8194616100-4">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">sets</span><span class="p">:</span><span class="nf">from_list</span><span class="p" data-group-id="8194616100-5">(</span><span class="p" data-group-id="8194616100-6">[</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="8194616100-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8194616100-7">[</span><span class="p" data-group-id="8194616100-8">{</span><span class="ss">version</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8194616100-8">}</span><span class="p" data-group-id="8194616100-7">]</span><span class="p" data-group-id="8194616100-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8194616100-9">#{</span><span class="ss">x</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8194616100-10">[</span><span class="p" data-group-id="8194616100-10">]</span><span class="p">,</span><span class="ss">y</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8194616100-11">[</span><span class="p" data-group-id="8194616100-11">]</span><span class="p">,</span><span class="ss">z</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8194616100-12">[</span><span class="p" data-group-id="8194616100-12">]</span><span class="p" data-group-id="8194616100-9">}</span></code></pre><p><code class="inline">sets</code> backed by maps is generally the most efficient set representation, with a
│ │ │  few possible exceptions:</p><ul><li><a href="../../lib/stdlib-8.0/doc/html/ordsets.html#intersection/2"><code class="inline">ordsets:intersection/2</code></a> can be more efficient than <a href="../../lib/stdlib-8.0/doc/html/sets.html#intersection/2"><code class="inline">sets:intersection/2</code></a>. If
│ │ │  the intersection operation is frequently used and operations that operate on a
│ │ │  single element in a set (such as <code class="inline">is_element/2</code>) are avoided, <a href="../../lib/stdlib-8.0/doc/html/ordsets.html"><code class="inline">ordsets</code></a> can
│ │ │  be a better choice than <a href="../../lib/stdlib-8.0/doc/html/sets.html"><code class="inline">sets</code></a>.</li><li>If the intersection operation is frequently used and operations that operate
│ │ │  on a single element in a set (such as <code class="inline">is_element/2</code>) must also be efficient,
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/gb_sets.html"><code class="inline">gb_sets</code></a> can potentially be a better choice than <a href="../../lib/stdlib-8.0/doc/html/sets.html"><code class="inline">sets</code></a>.</li><li>If the elements of the set are integers in a fairly compact range, the set can
│ │ │  be represented as an integer where each bit represents an element in the set.
│ │ │ @@ -203,18 +203,18 @@
│ │ │  for the runtime system).</p></li><li><p><strong>N</strong> - The number of elements in the map.</p></li><li><p><strong>Keys</strong> - A tuple with keys of the map: <code class="inline">{Key1,...,KeyN}</code>. The keys are
│ │ │  sorted.</p></li><li><p><strong>Value1</strong> - The value corresponding to the first key in the key tuple.</p></li><li><p><strong>ValueN</strong> - The value corresponding to the last key in the key tuple.</p></li></ul><p>As an example, let us look at how the map <code class="inline">#{a =&gt; foo, z =&gt; bar}</code> is
│ │ │  represented:</p><table><thead><tr><th style="text-align: center;">0</th><th style="text-align: left;">1</th><th style="text-align: center;">2</th><th style="text-align: center;">3</th><th style="text-align: left;">4</th></tr></thead><tbody><tr><td style="text-align: center;"><strong>FLATMAP</strong></td><td style="text-align: left;">2</td><td style="text-align: center;"><code class="inline">{a,z}</code></td><td style="text-align: center;"><code class="inline">foo</code></td><td style="text-align: left;"><code class="inline">bar</code></td></tr></tbody></table><p><em>Table: #{a =&gt; foo, z =&gt; bar}</em></p><p>Let us update the map: <code class="inline">M#{q =&gt; baz}</code>. The map now looks like this:</p><table><thead><tr><th style="text-align: center;">0</th><th style="text-align: left;">1</th><th style="text-align: center;">2</th><th style="text-align: center;">3</th><th style="text-align: center;">4</th><th style="text-align: center;">5</th></tr></thead><tbody><tr><td style="text-align: center;"><strong>FLATMAP</strong></td><td style="text-align: left;">3</td><td style="text-align: center;"><code class="inline">{a,q,z}</code></td><td style="text-align: center;"><code class="inline">foo</code></td><td style="text-align: center;"><code class="inline">baz</code></td><td style="text-align: center;"><code class="inline">bar</code></td></tr></tbody></table><p><em>Table: #{a =&gt; foo, q =&gt; baz, z =&gt; bar}</em></p><p>Finally, change the value of one element: <code class="inline">M#{z := bird}</code>. The map now looks
│ │ │  like this:</p><table><thead><tr><th style="text-align: center;">0</th><th style="text-align: left;">1</th><th style="text-align: center;">2</th><th style="text-align: center;">3</th><th style="text-align: center;">4</th><th style="text-align: center;">5</th></tr></thead><tbody><tr><td style="text-align: center;"><strong>FLATMAP</strong></td><td style="text-align: left;">3</td><td style="text-align: center;"><code class="inline">{a,q,z}</code></td><td style="text-align: center;"><code class="inline">foo</code></td><td style="text-align: center;"><code class="inline">baz</code></td><td style="text-align: center;"><code class="inline">bird</code></td></tr></tbody></table><p><em>Table: #{a =&gt; foo, q =&gt; baz, z =&gt; bird}</em></p><p>When the value for an existing key is updated, the key tuple is not updated,
│ │ │  allowing the key tuple to be shared with other instances of the map that have
│ │ │  the same keys. In fact, the key tuple can be shared between all maps with the
│ │ │  same keys with some care. To arrange that, define a function that returns a map.
│ │ │ -For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">new</span><span class="p" data-group-id="9137437937-1">(</span><span class="p" data-group-id="9137437937-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9137437937-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p" data-group-id="9137437937-2">}</span><span class="p">.</span></code></pre><p>Defined like this, the key tuple <code class="inline">{a,b,c}</code> will be a global literal. To ensure
│ │ │ +For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">new</span><span class="p" data-group-id="9822015756-1">(</span><span class="p" data-group-id="9822015756-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9822015756-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p" data-group-id="9822015756-2">}</span><span class="p">.</span></code></pre><p>Defined like this, the key tuple <code class="inline">{a,b,c}</code> will be a global literal. To ensure
│ │ │  that the key tuple is shared when creating an instance of the map, always call
│ │ │ -<code class="inline">new()</code> and modify the returned map:</p><pre><code class="makeup erlang" translate="no"><span class="w">    </span><span class="p" data-group-id="1594123152-1">(</span><span class="n">SOME_MODULE</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="1594123152-2">(</span><span class="p" data-group-id="1594123152-2">)</span><span class="p" data-group-id="1594123152-1">)</span><span class="p" data-group-id="1594123152-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="1594123152-3">}</span><span class="p">.</span></code></pre><p>Using the map syntax with small maps is particularly efficient. As long as the
│ │ │ +<code class="inline">new()</code> and modify the returned map:</p><pre><code class="makeup erlang" translate="no"><span class="w">    </span><span class="p" data-group-id="0861506051-1">(</span><span class="n">SOME_MODULE</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="0861506051-2">(</span><span class="p" data-group-id="0861506051-2">)</span><span class="p" data-group-id="0861506051-1">)</span><span class="p" data-group-id="0861506051-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="0861506051-3">}</span><span class="p">.</span></code></pre><p>Using the map syntax with small maps is particularly efficient. As long as the
│ │ │  keys are known at compile-time, the map is updated in one go, making the time to
│ │ │  update a map essentially constant regardless of the number of keys updated. The
│ │ │  same goes for matching. (When the keys are variables, one or more of the keys
│ │ │  could be identical, so the operations need to be performed sequentially from
│ │ │  left to right.)</p><p>The memory size for a small map is the size of all keys and values plus 5 words.
│ │ │  See <a href="memory.html">Memory</a> for more information about memory sizes.</p><h3 id="how-large-maps-are-implemented" class="section-heading">
│ │ │    <a href="#how-large-maps-are-implemented" class="hover-link">
│ │ │ @@ -241,21 +241,21 @@
│ │ │    <a href="#using-the-map-syntax" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Using the Map Syntax</span>
│ │ │  </h2>
│ │ │  <p>Using the map syntax is usually slightly more efficient than using the
│ │ │  corresponding function in the <a href="../../lib/stdlib-8.0/doc/html/maps.html"><code class="inline">maps</code></a> module.</p><p>The gain in efficiency for the map syntax is more noticeable for the following
│ │ │ -operations that can only be achieved using the map syntax:</p><ul><li>Matching multiple literal keys</li><li>Updating multiple literal keys</li><li>Adding multiple literal keys to a map</li></ul><p>For example:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="5017080608-1">#{</span><span class="ss">x</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="ss">z</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="5017080608-1">}</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="2635300534-1">(</span><span class="ss">x</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="2635300534-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Map3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="2635300534-2">(</span><span class="ss">y</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="2635300534-2">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="2635300534-3">(</span><span class="ss">z</span><span class="p">,</span><span class="w"> </span><span class="n">Z</span><span class="p">,</span><span class="w"> </span><span class="n">Map3</span><span class="p" data-group-id="2635300534-3">)</span></code></pre><p>If the map is a small map, the first example runs roughly three times as fast.</p><p>Note that for variable keys, the elements are updated sequentially from left to
│ │ │ -right. For example, given the following update with variable keys:</p><pre><code class="makeup erlang" translate="no"><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="3107982669-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Key3</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="3107982669-1">}</span></code></pre><p>the compiler rewrites it like this to ensure that the updates are applied from
│ │ │ -left to right:</p><pre><code class="makeup erlang" translate="no"><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="4742629382-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4742629382-1">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Map3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="4742629382-2">#{</span><span class="n">Key2</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4742629382-2">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map3</span><span class="p" data-group-id="4742629382-3">#{</span><span class="n">Key3</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="4742629382-3">}</span></code></pre><p>If a key is known to exist in a map, using the <code class="inline">:=</code> operator is slightly more
│ │ │ +operations that can only be achieved using the map syntax:</p><ul><li>Matching multiple literal keys</li><li>Updating multiple literal keys</li><li>Adding multiple literal keys to a map</li></ul><p>For example:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="9942618302-1">#{</span><span class="ss">x</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="ss">z</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="9942618302-1">}</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="5607998760-1">(</span><span class="ss">x</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="5607998760-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Map3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="5607998760-2">(</span><span class="ss">y</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="5607998760-2">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="5607998760-3">(</span><span class="ss">z</span><span class="p">,</span><span class="w"> </span><span class="n">Z</span><span class="p">,</span><span class="w"> </span><span class="n">Map3</span><span class="p" data-group-id="5607998760-3">)</span></code></pre><p>If the map is a small map, the first example runs roughly three times as fast.</p><p>Note that for variable keys, the elements are updated sequentially from left to
│ │ │ +right. For example, given the following update with variable keys:</p><pre><code class="makeup erlang" translate="no"><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="3030256992-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Key3</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="3030256992-1">}</span></code></pre><p>the compiler rewrites it like this to ensure that the updates are applied from
│ │ │ +left to right:</p><pre><code class="makeup erlang" translate="no"><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="8220309304-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="8220309304-1">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Map3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="8220309304-2">#{</span><span class="n">Key2</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8220309304-2">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map3</span><span class="p" data-group-id="8220309304-3">#{</span><span class="n">Key3</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="8220309304-3">}</span></code></pre><p>If a key is known to exist in a map, using the <code class="inline">:=</code> operator is slightly more
│ │ │  efficient than using the <code class="inline">=&gt;</code> operator for a small map.</p><h2 id="using-the-functions-in-the-maps-module" class="section-heading">
│ │ │    <a href="#using-the-functions-in-the-maps-module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Using the Functions in the maps Module</span>
│ │ │  </h2>
│ │ │  <p>Here follows some notes about most of the functions in the <code class="inline">maps</code> module. For
│ │ │ @@ -306,23 +306,23 @@
│ │ │    <a href="#maps-get-3" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">maps:get/3</span>
│ │ │  </h3>
│ │ │  <p>As an optimization, the compiler will rewrite a call to <a href="../../lib/stdlib-8.0/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a> to Erlang
│ │ │  code similar to the following:</p><pre><code class="makeup erlang" translate="no"><span class="n">Result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">Map</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="8810677674-1">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="8810677674-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Value</span><span class="p">;</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="8810677674-2">#{</span><span class="p" data-group-id="8810677674-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Default</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="7604673162-1">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="7604673162-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Value</span><span class="p">;</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="7604673162-2">#{</span><span class="p" data-group-id="7604673162-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Default</span><span class="w">
│ │ │           </span><span class="k">end</span></code></pre><p>This is reasonably efficient, but if a small map is used as an alternative to
│ │ │  using a record it is often better not to rely on default values as it prevents
│ │ │  sharing of keys, which may in the end use more memory than what you save from
│ │ │  not storing default values in the map.</p><p>If default values are nevertheless required, instead of calling <a href="../../lib/stdlib-8.0/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a>
│ │ │  multiple times, consider putting the default values in a map and merging that
│ │ │ -map with the other map:</p><pre><code class="makeup erlang" translate="no"><span class="n">DefaultMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8987893279-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Value2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Value2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">KeyN</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">ValueN</span><span class="p" data-group-id="8987893279-1">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">MapWithDefaultsApplied</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">merge</span><span class="p" data-group-id="8987893279-2">(</span><span class="n">DefaultMap</span><span class="p">,</span><span class="w"> </span><span class="n">OtherMap</span><span class="p" data-group-id="8987893279-2">)</span></code></pre><p>This helps share keys between the default map and the one you applied defaults
│ │ │ +map with the other map:</p><pre><code class="makeup erlang" translate="no"><span class="n">DefaultMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3494634031-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Value2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Value2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">KeyN</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">ValueN</span><span class="p" data-group-id="3494634031-1">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">MapWithDefaultsApplied</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">merge</span><span class="p" data-group-id="3494634031-2">(</span><span class="n">DefaultMap</span><span class="p">,</span><span class="w"> </span><span class="n">OtherMap</span><span class="p" data-group-id="3494634031-2">)</span></code></pre><p>This helps share keys between the default map and the one you applied defaults
│ │ │  to, as long as the default map contains <em>all</em> the keys that will ever be used
│ │ │  and not just the ones with default values. Whether this is faster than calling
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a> multiple times depends on the size of the map and the number of
│ │ │  default values.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before OTP 26.0 <a href="../../lib/stdlib-8.0/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a> was implemented by calling the function instead
│ │ │  of rewriting it as an Erlang expression. It is now slightly faster but can no
│ │ │  longer be traced.</p></section><h3 id="maps-intersect-2-maps-intersect_with-3" class="section-heading">
│ │ │    <a href="#maps-intersect-2-maps-intersect_with-3" class="hover-link">
│ │ │ @@ -410,29 +410,29 @@
│ │ │    <a href="#maps-put-3" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">maps:put/3</span>
│ │ │  </h3>
│ │ │  <p><a href="../../lib/stdlib-8.0/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a> is implemented in C.</p><p>If the key is known to already exist in the map, <a href="../../lib/stdlib-8.0/doc/html/maps.html#update/3"><code class="inline">maps:update/3</code></a> is slightly
│ │ │  more efficient than <a href="../../lib/stdlib-8.0/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a>.</p><p>If the compiler can determine that the third argument is always a map, it
│ │ │ -will rewrite the call to <a href="../../lib/stdlib-8.0/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a> to use the map syntax for updating the map.</p><p>For example, consider the following function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_to_known_map</span><span class="p" data-group-id="7221193788-1">(</span><span class="n">Map0</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="7221193788-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_map</span><span class="p" data-group-id="7221193788-2">(</span><span class="n">Map0</span><span class="p" data-group-id="7221193788-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Map1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="7221193788-3">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">Map0</span><span class="p" data-group-id="7221193788-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="7221193788-4">(</span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="7221193788-4">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="7221193788-5">(</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="7221193788-5">)</span><span class="p">.</span></code></pre><p>The compiler first rewrites each call to <a href="../../lib/stdlib-8.0/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a> to use the map
│ │ │ +will rewrite the call to <a href="../../lib/stdlib-8.0/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a> to use the map syntax for updating the map.</p><p>For example, consider the following function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_to_known_map</span><span class="p" data-group-id="8048187698-1">(</span><span class="n">Map0</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="8048187698-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_map</span><span class="p" data-group-id="8048187698-2">(</span><span class="n">Map0</span><span class="p" data-group-id="8048187698-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Map1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="8048187698-3">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">Map0</span><span class="p" data-group-id="8048187698-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="8048187698-4">(</span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="8048187698-4">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="8048187698-5">(</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="8048187698-5">)</span><span class="p">.</span></code></pre><p>The compiler first rewrites each call to <a href="../../lib/stdlib-8.0/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a> to use the map
│ │ │  syntax, and subsequently combines the three update operations to a
│ │ │ -single update operation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_to_known_map</span><span class="p" data-group-id="7388102258-1">(</span><span class="n">Map0</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="7388102258-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_map</span><span class="p" data-group-id="7388102258-2">(</span><span class="n">Map0</span><span class="p" data-group-id="7388102258-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Map0</span><span class="p" data-group-id="7388102258-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="7388102258-3">}</span><span class="p">.</span></code></pre><p>If the compiler cannot determine that the third argument is always a
│ │ │ +single update operation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_to_known_map</span><span class="p" data-group-id="7026798780-1">(</span><span class="n">Map0</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="7026798780-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_map</span><span class="p" data-group-id="7026798780-2">(</span><span class="n">Map0</span><span class="p" data-group-id="7026798780-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Map0</span><span class="p" data-group-id="7026798780-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="7026798780-3">}</span><span class="p">.</span></code></pre><p>If the compiler cannot determine that the third argument is always a
│ │ │  map, it retains the <a href="../../lib/stdlib-8.0/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a> call. For example, given this
│ │ │ -function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_to_map</span><span class="p" data-group-id="5531766371-1">(</span><span class="n">Map0</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="5531766371-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Map1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="5531766371-2">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">Map0</span><span class="p" data-group-id="5531766371-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="5531766371-3">(</span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="5531766371-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="5531766371-4">(</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="5531766371-4">)</span><span class="p">.</span></code></pre><p>the compiler keeps the first call to <a href="../../lib/stdlib-8.0/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a>, but rewrites
│ │ │ -and combines the other two calls:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_to_map</span><span class="p" data-group-id="5343674449-1">(</span><span class="n">Map0</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="5343674449-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Map1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="5343674449-2">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">Map0</span><span class="p" data-group-id="5343674449-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Map1</span><span class="p" data-group-id="5343674449-3">#{</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="5343674449-3">}</span><span class="p">.</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>The rewriting of <a href="../../lib/stdlib-8.0/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a> to the map syntax was introduced in
│ │ │ +function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_to_map</span><span class="p" data-group-id="8311164644-1">(</span><span class="n">Map0</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="8311164644-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Map1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="8311164644-2">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">Map0</span><span class="p" data-group-id="8311164644-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="8311164644-3">(</span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="8311164644-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="8311164644-4">(</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="8311164644-4">)</span><span class="p">.</span></code></pre><p>the compiler keeps the first call to <a href="../../lib/stdlib-8.0/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a>, but rewrites
│ │ │ +and combines the other two calls:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_to_map</span><span class="p" data-group-id="7571077987-1">(</span><span class="n">Map0</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="7571077987-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Map1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">put</span><span class="p" data-group-id="7571077987-2">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">Map0</span><span class="p" data-group-id="7571077987-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Map1</span><span class="p" data-group-id="7571077987-3">#{</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="7571077987-3">}</span><span class="p">.</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>The rewriting of <a href="../../lib/stdlib-8.0/doc/html/maps.html#put/3"><code class="inline">maps:put/3</code></a> to the map syntax was introduced in
│ │ │  Erlang/OTP 28.</p></section><h3 id="maps-remove-2" class="section-heading">
│ │ │    <a href="#maps-remove-2" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">maps:remove/2</span>
│ │ │  </h3>
│ │ │  <p><a href="../../lib/stdlib-8.0/doc/html/maps.html#remove/2"><code class="inline">maps:remove/2</code></a> is implemented in C.</p><h3 id="maps-size-1" class="section-heading">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/modules.html
│ │ │ @@ -118,20 +118,20 @@
│ │ │  <h2 id="module-syntax" class="section-heading">
│ │ │    <a href="#module-syntax" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Module Syntax</span>
│ │ │  </h2>
│ │ │  <p>Erlang code is divided into <em>modules</em>. A module consists of a sequence of
│ │ │ -attributes and function declarations, each terminated by a period (<code class="inline">.</code>).</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7236964678-1">(</span><span class="ss">m</span><span class="p" data-group-id="7236964678-1">)</span><span class="p">.</span><span class="w">          </span><span class="c1">% module attribute</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7236964678-2">(</span><span class="p" data-group-id="7236964678-3">[</span><span class="ss">fact</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7236964678-3">]</span><span class="p" data-group-id="7236964678-2">)</span><span class="p">.</span><span class="w">   </span><span class="c1">% module attribute</span><span class="w">
│ │ │ +attributes and function declarations, each terminated by a period (<code class="inline">.</code>).</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6922445895-1">(</span><span class="ss">m</span><span class="p" data-group-id="6922445895-1">)</span><span class="p">.</span><span class="w">          </span><span class="c1">% module attribute</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6922445895-2">(</span><span class="p" data-group-id="6922445895-3">[</span><span class="ss">fact</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6922445895-3">]</span><span class="p" data-group-id="6922445895-2">)</span><span class="p">.</span><span class="w">   </span><span class="c1">% module attribute</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="7236964678-4">(</span><span class="n">N</span><span class="p" data-group-id="7236964678-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="o">&gt;</span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% beginning of function declaration</span><span class="w">
│ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="7236964678-5">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="7236964678-5">)</span><span class="p">;</span><span class="w">   </span><span class="c1">%  |</span><span class="w">
│ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="7236964678-6">(</span><span class="mi">0</span><span class="p" data-group-id="7236964678-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">           </span><span class="c1">%  |</span><span class="w">
│ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="6922445895-4">(</span><span class="n">N</span><span class="p" data-group-id="6922445895-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="o">&gt;</span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% beginning of function declaration</span><span class="w">
│ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="6922445895-5">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="6922445895-5">)</span><span class="p">;</span><span class="w">   </span><span class="c1">%  |</span><span class="w">
│ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="6922445895-6">(</span><span class="mi">0</span><span class="p" data-group-id="6922445895-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">           </span><span class="c1">%  |</span><span class="w">
│ │ │      </span><span class="mi">1</span><span class="p">.</span><span class="w">               </span><span class="c1">% end of function declaration</span></code></pre><p>For a description of function declarations, see
│ │ │  <a href="ref_man_functions.html">Function Declaration Syntax</a>.</p><h2 id="module-attributes" class="section-heading">
│ │ │    <a href="#module-attributes" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Module Attributes</span>
│ │ │  </h2>
│ │ │ @@ -176,71 +176,71 @@
│ │ │  meaning.</p></section></li></ul><h3 id="behaviour-module-attribute" class="section-heading">
│ │ │    <a href="#behaviour-module-attribute" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Behaviour Module Attribute</span>
│ │ │  </h3>
│ │ │  <p>It is possible to specify that the module is the callback module for a
│ │ │ -<em>behaviour</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="7582275965-1">(</span><span class="n">Behaviour</span><span class="p" data-group-id="7582275965-1">)</span><span class="p">.</span></code></pre><p>The atom <code class="inline">Behaviour</code> gives the name of the behaviour, which can be a
│ │ │ +<em>behaviour</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="8543464702-1">(</span><span class="n">Behaviour</span><span class="p" data-group-id="8543464702-1">)</span><span class="p">.</span></code></pre><p>The atom <code class="inline">Behaviour</code> gives the name of the behaviour, which can be a
│ │ │  user-defined behaviour or one of the following OTP standard behaviours:</p><ul><li><code class="inline">gen_server</code></li><li><code class="inline">gen_statem</code></li><li><code class="inline">gen_event</code></li><li><code class="inline">supervisor</code></li></ul><p>The spelling <code class="inline">behavior</code> is also accepted.</p><p>The callback functions of the module can be specified either directly by the
│ │ │ -exported function <code class="inline">behaviour_info/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">behaviour_info</span><span class="p" data-group-id="7149044147-1">(</span><span class="ss">callbacks</span><span class="p" data-group-id="7149044147-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Callbacks</span><span class="p">.</span></code></pre><p>or by a <code class="inline">-callback</code> attribute for each callback function:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="2994952808-1">(</span><span class="n">Arguments</span><span class="p" data-group-id="2994952808-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Result</span><span class="p">.</span></code></pre><p>Here, <code class="inline">Arguments</code> is a list of zero or more arguments. The <code class="inline">-callback</code> attribute
│ │ │ +exported function <code class="inline">behaviour_info/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">behaviour_info</span><span class="p" data-group-id="9290181560-1">(</span><span class="ss">callbacks</span><span class="p" data-group-id="9290181560-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Callbacks</span><span class="p">.</span></code></pre><p>or by a <code class="inline">-callback</code> attribute for each callback function:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="0931578042-1">(</span><span class="n">Arguments</span><span class="p" data-group-id="0931578042-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Result</span><span class="p">.</span></code></pre><p>Here, <code class="inline">Arguments</code> is a list of zero or more arguments. The <code class="inline">-callback</code> attribute
│ │ │  is to be preferred since the extra type information can be used by tools to
│ │ │  produce documentation or find discrepancies.</p><p>Read more about behaviours and callback modules in
│ │ │  <a href="../../doc/system/design_principles.html#behaviours">OTP Design Principles</a>.</p><h3 id="record-definitions" class="section-heading">
│ │ │    <a href="#record-definitions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Record Definitions</span>
│ │ │  </h3>
│ │ │ -<p>The same syntax as for module attributes is used for record definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1431246410-1">(</span><span class="n">Record</span><span class="p">,</span><span class="w"> </span><span class="n">Fields</span><span class="p" data-group-id="1431246410-1">)</span><span class="p">.</span></code></pre><p>Record definitions are allowed anywhere in a module, also among the function
│ │ │ +<p>The same syntax as for module attributes is used for record definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9107757577-1">(</span><span class="n">Record</span><span class="p">,</span><span class="w"> </span><span class="n">Fields</span><span class="p" data-group-id="9107757577-1">)</span><span class="p">.</span></code></pre><p>Record definitions are allowed anywhere in a module, also among the function
│ │ │  declarations. Read more in <a href="ref_man_records.html">Records</a>.</p><h3 id="preprocessor" class="section-heading">
│ │ │    <a href="#preprocessor" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Preprocessor</span>
│ │ │  </h3>
│ │ │  <p>The same syntax as for module attributes is used by the preprocessor, which
│ │ │ -supports file inclusion, macros, and conditional compilation:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="4078320801-1">(</span><span class="s">&quot;SomeFile.hrl&quot;</span><span class="p" data-group-id="4078320801-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4078320801-2">(</span><span class="n">Macro</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="4078320801-2">)</span><span class="p">.</span></code></pre><p>Read more in <a href="macros.html">Preprocessor</a>.</p><h3 id="setting-file-and-line" class="section-heading">
│ │ │ +supports file inclusion, macros, and conditional compilation:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="7900017867-1">(</span><span class="s">&quot;SomeFile.hrl&quot;</span><span class="p" data-group-id="7900017867-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7900017867-2">(</span><span class="n">Macro</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="7900017867-2">)</span><span class="p">.</span></code></pre><p>Read more in <a href="macros.html">Preprocessor</a>.</p><h3 id="setting-file-and-line" class="section-heading">
│ │ │    <a href="#setting-file-and-line" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Setting File and Line</span>
│ │ │  </h3>
│ │ │  <p>The same syntax as for module attributes is used for changing the pre-defined
│ │ │ -macros <code class="inline">?FILE</code> and <code class="inline">?LINE</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">file</span><span class="p" data-group-id="7732730540-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">Line</span><span class="p" data-group-id="7732730540-1">)</span><span class="p">.</span></code></pre><p>This attribute is used by tools, such as Yecc, to inform the compiler that the
│ │ │ +macros <code class="inline">?FILE</code> and <code class="inline">?LINE</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">file</span><span class="p" data-group-id="1329750145-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">Line</span><span class="p" data-group-id="1329750145-1">)</span><span class="p">.</span></code></pre><p>This attribute is used by tools, such as Yecc, to inform the compiler that the
│ │ │  source program is generated by another tool. It also indicates the
│ │ │  correspondence of source files to lines of the original user-written file, from
│ │ │  which the source program is produced.</p><h3 id="types-and-function-specifications" class="section-heading">
│ │ │    <a href="#types-and-function-specifications" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Types and function specifications</span>
│ │ │  </h3>
│ │ │  <p>A syntax similar to that for module attributes is used for specifying types and
│ │ │ -function specifications:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">my_type</span><span class="p" data-group-id="4101597309-1">(</span><span class="p" data-group-id="4101597309-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="4101597309-2">(</span><span class="p" data-group-id="4101597309-2">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="4101597309-3">(</span><span class="p" data-group-id="4101597309-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">my_function</span><span class="p" data-group-id="4101597309-4">(</span><span class="nf">integer</span><span class="p" data-group-id="4101597309-5">(</span><span class="p" data-group-id="4101597309-5">)</span><span class="p" data-group-id="4101597309-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="4101597309-6">(</span><span class="p" data-group-id="4101597309-6">)</span><span class="p">.</span></code></pre><p>Read more in <a href="typespec.html">Types and Function specifications</a>.</p><p>The description is based on
│ │ │ +function specifications:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">my_type</span><span class="p" data-group-id="4194162120-1">(</span><span class="p" data-group-id="4194162120-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="4194162120-2">(</span><span class="p" data-group-id="4194162120-2">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="4194162120-3">(</span><span class="p" data-group-id="4194162120-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">my_function</span><span class="p" data-group-id="4194162120-4">(</span><span class="nf">integer</span><span class="p" data-group-id="4194162120-5">(</span><span class="p" data-group-id="4194162120-5">)</span><span class="p" data-group-id="4194162120-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="4194162120-6">(</span><span class="p" data-group-id="4194162120-6">)</span><span class="p">.</span></code></pre><p>Read more in <a href="typespec.html">Types and Function specifications</a>.</p><p>The description is based on
│ │ │  <a href="http://www.erlang.org/eeps/eep-0008.html">EEP8 - Types and function specifications</a>,
│ │ │  which is not to be further updated.</p><h3 id="documentation-attributes" class="section-heading">
│ │ │    <a href="#documentation-attributes" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Documentation attributes</span>
│ │ │  </h3>
│ │ │  <p>The module attribute <code class="inline">-doc(Documentation)</code> is used to provide user documentation
│ │ │ -for a function/type/callback:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="9485261402-1">(</span><span class="s">&quot;Example documentation&quot;</span><span class="p" data-group-id="9485261402-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">example</span><span class="p" data-group-id="9485261402-2">(</span><span class="p" data-group-id="9485261402-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The attribute should be placed just before the entity it documents. The
│ │ │ +for a function/type/callback:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="6365052925-1">(</span><span class="s">&quot;Example documentation&quot;</span><span class="p" data-group-id="6365052925-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">example</span><span class="p" data-group-id="6365052925-2">(</span><span class="p" data-group-id="6365052925-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The attribute should be placed just before the entity it documents. The
│ │ │  parentheses are optional around <code class="inline">Documentation</code>. The allowed values for
│ │ │  <code class="inline">Documentation</code> are:</p><ul><li><p><strong><a href="data_types.html#string">literal string</a> or
│ │ │  <a href="expressions.html#unicode-segments">utf-8 encoded binary string</a></strong> - The string
│ │ │  documenting the entity. Any literal string is allowed, so both
│ │ │  <a href="data_types.html#tqstring">triple quoted strings</a> and
│ │ │  <a href="data_types.html#sigil">sigils</a> that translate to literal strings can be used.
│ │ │ -The following examples are equivalent:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="4049127239-1">(</span><span class="s">&quot;Example \&quot;docs\&quot;&quot;</span><span class="p" data-group-id="4049127239-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="4049127239-2">(</span><span class="p" data-group-id="4049127239-3">&lt;&lt;</span><span class="s">&quot;Example \&quot;docs\&quot;&quot;</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="4049127239-3">&gt;&gt;</span><span class="p" data-group-id="4049127239-2">)</span><span class="p">.</span><span class="w">
│ │ │ +The following examples are equivalent:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="4995751420-1">(</span><span class="s">&quot;Example \&quot;docs\&quot;&quot;</span><span class="p" data-group-id="4995751420-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="4995751420-2">(</span><span class="p" data-group-id="4995751420-3">&lt;&lt;</span><span class="s">&quot;Example \&quot;docs\&quot;&quot;</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="4995751420-3">&gt;&gt;</span><span class="p" data-group-id="4995751420-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">~S/Example &quot;docs&quot;/</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="s">&quot;
│ │ │     Example &quot;</span><span class="ss">docs</span><span class="s">&quot;
│ │ │     &quot;</span><span class="s">&quot;&quot;</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">~B|Example &quot;docs&quot;|</span><span class="p">.</span></code></pre><p>For clarity it is recommended to use either normal <code class="inline">&quot;strings&quot;</code> or triple
│ │ │  quoted strings for documentation attributes.</p></li><li><p><strong><code class="inline">{file,</code> <a href="../../lib/kernel-11.0/doc/html/file.html#t:name/0"><code class="inline">file:name/0</code></a> <code class="inline">}</code></strong> - Read the contents of filename and use
│ │ │  that as the documentation string.</p></li><li><p><strong><code class="inline">false</code></strong> - Set the current entity as hidden, that is, it should not be
│ │ │ @@ -253,15 +253,15 @@
│ │ │    <a href="#the-feature-directive" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">The feature directive</span>
│ │ │  </h2>
│ │ │  <p>While not a module attribute, but rather a directive (since it might affect
│ │ │  syntax), there is the <code class="inline">-feature(..)</code> directive used for enabling and disabling
│ │ │ -<a href="../../doc/system/features.html#features">features</a>.</p><p>The syntax is similar to that of an attribute, but has two arguments:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">feature</span><span class="p" data-group-id="3283132305-1">(</span><span class="n">FeatureName</span><span class="p">,</span><span class="w"> </span><span class="ss">enable</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">disable</span><span class="p" data-group-id="3283132305-1">)</span><span class="p">.</span></code></pre><p>Note that the <a href="macros.html#feature-directive">feature directive</a> can only appear
│ │ │ +<a href="../../doc/system/features.html#features">features</a>.</p><p>The syntax is similar to that of an attribute, but has two arguments:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">feature</span><span class="p" data-group-id="9479983288-1">(</span><span class="n">FeatureName</span><span class="p">,</span><span class="w"> </span><span class="ss">enable</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">disable</span><span class="p" data-group-id="9479983288-1">)</span><span class="p">.</span></code></pre><p>Note that the <a href="macros.html#feature-directive">feature directive</a> can only appear
│ │ │  in a prefix of the module.</p><h2 id="comments" class="section-heading">
│ │ │    <a href="#comments" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Comments</span>
│ │ │  </h2>
│ │ │  <p>Comments can be placed anywhere in a module except within strings and
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/nif.html
│ │ │ @@ -133,26 +133,26 @@
│ │ │    <span class="text">Erlang Program</span>
│ │ │  </h2>
│ │ │  <p>Even if all functions of a module are NIFs, an Erlang module is still needed for
│ │ │  two reasons:</p><ul><li>The NIF library must be explicitly loaded by Erlang code in the same module.</li><li>All NIFs of a module must have an Erlang implementation as well.</li></ul><p>Normally these are minimal stub implementations that throw an exception. But
│ │ │  they can also be used as fallback implementations for functions that do not have
│ │ │  native implementations on some architectures.</p><p>NIF libraries are loaded by calling <a href="../../erts-17.0/doc/html/erlang.html#load_nif/2"><code class="inline">erlang:load_nif/2</code></a>, with the name of the
│ │ │  shared library as argument. The second argument can be any term that will be
│ │ │ -passed on to the library and used for initialization:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1762127610-1">(</span><span class="ss">complex6</span><span class="p" data-group-id="1762127610-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1762127610-2">(</span><span class="p" data-group-id="1762127610-3">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1762127610-3">]</span><span class="p" data-group-id="1762127610-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">nifs</span><span class="p" data-group-id="1762127610-4">(</span><span class="p" data-group-id="1762127610-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1762127610-5">]</span><span class="p" data-group-id="1762127610-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="1762127610-6">(</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1762127610-6">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="1762127610-7">(</span><span class="p" data-group-id="1762127610-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="1762127610-8">(</span><span class="s">&quot;./complex6_nif&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="1762127610-8">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="1762127610-9">(</span><span class="p">_</span><span class="n">X</span><span class="p" data-group-id="1762127610-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="1762127610-10">(</span><span class="ss">nif_library_not_loaded</span><span class="p" data-group-id="1762127610-10">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="1762127610-11">(</span><span class="p">_</span><span class="n">Y</span><span class="p" data-group-id="1762127610-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="1762127610-12">(</span><span class="ss">nif_library_not_loaded</span><span class="p" data-group-id="1762127610-12">)</span><span class="p">.</span></code></pre><p>Here, the directive <code class="inline">on_load</code> is used to get function <code class="inline">init</code> to be automatically
│ │ │ +passed on to the library and used for initialization:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3565252305-1">(</span><span class="ss">complex6</span><span class="p" data-group-id="3565252305-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3565252305-2">(</span><span class="p" data-group-id="3565252305-3">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3565252305-3">]</span><span class="p" data-group-id="3565252305-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">nifs</span><span class="p" data-group-id="3565252305-4">(</span><span class="p" data-group-id="3565252305-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3565252305-5">]</span><span class="p" data-group-id="3565252305-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="3565252305-6">(</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3565252305-6">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="3565252305-7">(</span><span class="p" data-group-id="3565252305-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="3565252305-8">(</span><span class="s">&quot;./complex6_nif&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="3565252305-8">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="3565252305-9">(</span><span class="p">_</span><span class="n">X</span><span class="p" data-group-id="3565252305-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="3565252305-10">(</span><span class="ss">nif_library_not_loaded</span><span class="p" data-group-id="3565252305-10">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="3565252305-11">(</span><span class="p">_</span><span class="n">Y</span><span class="p" data-group-id="3565252305-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="3565252305-12">(</span><span class="ss">nif_library_not_loaded</span><span class="p" data-group-id="3565252305-12">)</span><span class="p">.</span></code></pre><p>Here, the directive <code class="inline">on_load</code> is used to get function <code class="inline">init</code> to be automatically
│ │ │  called when the module is loaded. If <code class="inline">init</code> returns anything other than <code class="inline">ok</code>,
│ │ │  such when the loading of the NIF library fails in this example, the module is
│ │ │  unloaded and calls to functions within it, fail.</p><p>Loading the NIF library overrides the stub implementations and cause calls to
│ │ │  <code class="inline">foo</code> and <code class="inline">bar</code> to be dispatched to the NIF implementations instead.</p><h2 id="nif-library-code" class="section-heading">
│ │ │    <a href="#nif-library-code" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -209,23 +209,23 @@
│ │ │    <a href="#running-the-example" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Running the Example</span>
│ │ │  </h2>
│ │ │  <p><em>Step 1.</em> Compile the C code:</p><pre><code class="text">unix&gt; gcc -o complex6_nif.so -fpic -shared complex.c complex6_nif.c
│ │ │  windows&gt; cl -LD -MD -Fe complex6_nif.dll complex.c complex6_nif.c</code></pre><p><em>Step 2:</em> Start Erlang and compile the Erlang code:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="ss">erl</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="w"> </span><span class="n">R13B04</span><span class="w"> </span><span class="p" data-group-id="3309508360-1">(</span><span class="ss">erts</span><span class="o">-</span><span class="mf">5.7</span><span class="p">.</span><span class="mi">5</span><span class="p" data-group-id="3309508360-1">)</span><span class="w"> </span><span class="p" data-group-id="3309508360-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="3309508360-2">]</span><span class="w"> </span><span class="p" data-group-id="3309508360-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="3309508360-3">]</span><span class="w"> </span><span class="p" data-group-id="3309508360-4">[</span><span class="nc">rq</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="3309508360-4">]</span><span class="w"> </span><span class="p" data-group-id="3309508360-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="3309508360-5">]</span><span class="w"> </span><span class="p" data-group-id="3309508360-6">[</span><span class="ss">kernel</span><span class="o">-</span><span class="nc">poll</span><span class="p">:</span><span class="ss">false</span><span class="p" data-group-id="3309508360-6">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="w"> </span><span class="n">R13B04</span><span class="w"> </span><span class="p" data-group-id="3887321261-1">(</span><span class="ss">erts</span><span class="o">-</span><span class="mf">5.7</span><span class="p">.</span><span class="mi">5</span><span class="p" data-group-id="3887321261-1">)</span><span class="w"> </span><span class="p" data-group-id="3887321261-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="3887321261-2">]</span><span class="w"> </span><span class="p" data-group-id="3887321261-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="3887321261-3">]</span><span class="w"> </span><span class="p" data-group-id="3887321261-4">[</span><span class="nc">rq</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="3887321261-4">]</span><span class="w"> </span><span class="p" data-group-id="3887321261-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="3887321261-5">]</span><span class="w"> </span><span class="p" data-group-id="3887321261-6">[</span><span class="ss">kernel</span><span class="o">-</span><span class="nc">poll</span><span class="p">:</span><span class="ss">false</span><span class="p" data-group-id="3887321261-6">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">7.5</span><span class="w">  </span><span class="p" data-group-id="3309508360-7">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="3309508360-7">)</span><span class="w">
│ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="3309508360-8">(</span><span class="ss">complex6</span><span class="p" data-group-id="3309508360-8">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3309508360-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex6</span><span class="p" data-group-id="3309508360-9">}</span></code></pre><p><em>Step 3:</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="8544405729-1">(</span><span class="mi">3</span><span class="p" data-group-id="8544405729-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">7.5</span><span class="w">  </span><span class="p" data-group-id="3887321261-7">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="3887321261-7">)</span><span class="w">
│ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="3887321261-8">(</span><span class="ss">complex6</span><span class="p" data-group-id="3887321261-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3887321261-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex6</span><span class="p" data-group-id="3887321261-9">}</span></code></pre><p><em>Step 3:</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="5201955260-1">(</span><span class="mi">3</span><span class="p" data-group-id="5201955260-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="8544405729-2">(</span><span class="mi">5</span><span class="p" data-group-id="8544405729-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="5201955260-2">(</span><span class="mi">5</span><span class="p" data-group-id="5201955260-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">10</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="8544405729-3">(</span><span class="s">&quot;not an integer&quot;</span><span class="p" data-group-id="8544405729-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="5201955260-3">(</span><span class="s">&quot;not an integer&quot;</span><span class="p" data-group-id="5201955260-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: bad argument
│ │ │       in function  complex6:foo/1
│ │ │          called as comlpex6:foo(&quot;not an integer&quot;)</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/nominals.html
│ │ │ @@ -123,55 +123,55 @@
│ │ │  </h2>
│ │ │  <p>For <a href="typespec.html#type-declarations-of-user-defined-types">user-defined types</a>
│ │ │  defined with <code class="inline">-type</code>, the Erlang compiler will ignore their type names. This
│ │ │  means the Erlang compiler uses a structural type system. Two types are seen as
│ │ │  equivalent if their structures are the same. Type comparison is based on the
│ │ │  structures of the types, not on how the user explicitly defines them. In the
│ │ │  following example, <code class="inline">meter()</code> and <code class="inline">foot()</code> are equivalent, and neither differs
│ │ │ -from the basic type <code class="inline">integer()</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">meter</span><span class="p" data-group-id="0283935937-1">(</span><span class="p" data-group-id="0283935937-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="0283935937-2">(</span><span class="p" data-group-id="0283935937-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">foot</span><span class="p" data-group-id="0283935937-3">(</span><span class="p" data-group-id="0283935937-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="0283935937-4">(</span><span class="p" data-group-id="0283935937-4">)</span><span class="p">.</span></code></pre><p>Nominal typing is an alternative type system. Two nominal types are equivalent
│ │ │ +from the basic type <code class="inline">integer()</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">meter</span><span class="p" data-group-id="7192093934-1">(</span><span class="p" data-group-id="7192093934-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="7192093934-2">(</span><span class="p" data-group-id="7192093934-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">foot</span><span class="p" data-group-id="7192093934-3">(</span><span class="p" data-group-id="7192093934-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="7192093934-4">(</span><span class="p" data-group-id="7192093934-4">)</span><span class="p">.</span></code></pre><p>Nominal typing is an alternative type system. Two nominal types are equivalent
│ │ │  if and only if they are declared with the same type name. The syntax for
│ │ │  declaring nominal types is <code class="inline">-nominal</code>.</p><p>If <code class="inline">meter()</code> and <code class="inline">foot()</code> are defined as nominal types, they will no longer be
│ │ │  compatible. When a function expects type <code class="inline">meter()</code>, passing in type <code class="inline">foot()</code>
│ │ │ -will result in a warning raised by the type checker.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">meter</span><span class="p" data-group-id="5217489008-1">(</span><span class="p" data-group-id="5217489008-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="5217489008-2">(</span><span class="p" data-group-id="5217489008-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">foot</span><span class="p" data-group-id="5217489008-3">(</span><span class="p" data-group-id="5217489008-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="5217489008-4">(</span><span class="p" data-group-id="5217489008-4">)</span><span class="p">.</span></code></pre><p>The main use case of nominal types is to prevent accidental misuse of types with
│ │ │ +will result in a warning raised by the type checker.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">meter</span><span class="p" data-group-id="3418849077-1">(</span><span class="p" data-group-id="3418849077-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3418849077-2">(</span><span class="p" data-group-id="3418849077-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">foot</span><span class="p" data-group-id="3418849077-3">(</span><span class="p" data-group-id="3418849077-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3418849077-4">(</span><span class="p" data-group-id="3418849077-4">)</span><span class="p">.</span></code></pre><p>The main use case of nominal types is to prevent accidental misuse of types with
│ │ │  the same structure. Within OTP, nominal type-checking is done in Dialyzer. The
│ │ │  Erlang compiler does not perform nominal type-checking.</p><h2 id="nominal-type-checking-rules" class="section-heading">
│ │ │    <a href="#nominal-type-checking-rules" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Nominal Type-Checking Rules</span>
│ │ │  </h2>
│ │ │  <p>In general, if two nominal types have different names, and one is not derived
│ │ │  from the other, they are not compatible. Dialyzer's nominal type-checking
│ │ │ -aligns with the examples' expected results in this section.</p><p>If we continue from the example above:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">int_to_meter</span><span class="p" data-group-id="7881629619-1">(</span><span class="nf">integer</span><span class="p" data-group-id="7881629619-2">(</span><span class="p" data-group-id="7881629619-2">)</span><span class="p" data-group-id="7881629619-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">meter</span><span class="p" data-group-id="7881629619-3">(</span><span class="p" data-group-id="7881629619-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">int_to_meter</span><span class="p" data-group-id="7881629619-4">(</span><span class="n">X</span><span class="p" data-group-id="7881629619-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │ +aligns with the examples' expected results in this section.</p><p>If we continue from the example above:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">int_to_meter</span><span class="p" data-group-id="4831831885-1">(</span><span class="nf">integer</span><span class="p" data-group-id="4831831885-2">(</span><span class="p" data-group-id="4831831885-2">)</span><span class="p" data-group-id="4831831885-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">meter</span><span class="p" data-group-id="4831831885-3">(</span><span class="p" data-group-id="4831831885-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">int_to_meter</span><span class="p" data-group-id="4831831885-4">(</span><span class="n">X</span><span class="p" data-group-id="4831831885-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="7881629619-5">(</span><span class="p" data-group-id="7881629619-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">foot</span><span class="p" data-group-id="7881629619-6">(</span><span class="p" data-group-id="7881629619-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="7881629619-7">(</span><span class="p" data-group-id="7881629619-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">int_to_meter</span><span class="p" data-group-id="7881629619-8">(</span><span class="mi">24</span><span class="p" data-group-id="7881629619-8">)</span><span class="p">.</span></code></pre><p>A type checker that performs nominal type-checking should raise a warning.
│ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="4831831885-5">(</span><span class="p" data-group-id="4831831885-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">foot</span><span class="p" data-group-id="4831831885-6">(</span><span class="p" data-group-id="4831831885-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="4831831885-7">(</span><span class="p" data-group-id="4831831885-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">int_to_meter</span><span class="p" data-group-id="4831831885-8">(</span><span class="mi">24</span><span class="p" data-group-id="4831831885-8">)</span><span class="p">.</span></code></pre><p>A type checker that performs nominal type-checking should raise a warning.
│ │ │  According to the specification, <code class="inline">foo/0</code> should return a <code class="inline">foot()</code> type. However,
│ │ │  the function <code class="inline">int_to_meter/1</code> returns a <code class="inline">meter()</code> type, so <code class="inline">foo/0</code> will also
│ │ │  return a <code class="inline">meter()</code> type. Because <code class="inline">meter()</code> and <code class="inline">foot()</code> are incompatible
│ │ │  nominal types, Dialyzer raises the following warning for <code class="inline">foo/0</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">Invalid</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="ss">specification</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">function</span><span class="w"> </span><span class="ss">foo</span><span class="p">/</span><span class="mi">0</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="n">The</span><span class="w"> </span><span class="ss">success</span><span class="w"> </span><span class="ss">typing</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="7856722540-1">(</span><span class="p" data-group-id="7856722540-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7856722540-2">(</span><span class="nf">meter</span><span class="p" data-group-id="7856722540-3">(</span><span class="p" data-group-id="7856722540-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="7856722540-4">(</span><span class="p" data-group-id="7856722540-4">)</span><span class="p" data-group-id="7856722540-2">)</span><span class="w">
│ │ │ -</span><span class="n">But</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">spec</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="7856722540-5">(</span><span class="p" data-group-id="7856722540-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">foot</span><span class="p" data-group-id="7856722540-6">(</span><span class="p" data-group-id="7856722540-6">)</span><span class="w">
│ │ │ +</span><span class="n">The</span><span class="w"> </span><span class="ss">success</span><span class="w"> </span><span class="ss">typing</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="8913848847-1">(</span><span class="p" data-group-id="8913848847-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8913848847-2">(</span><span class="nf">meter</span><span class="p" data-group-id="8913848847-3">(</span><span class="p" data-group-id="8913848847-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="8913848847-4">(</span><span class="p" data-group-id="8913848847-4">)</span><span class="p" data-group-id="8913848847-2">)</span><span class="w">
│ │ │ +</span><span class="n">But</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">spec</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="8913848847-5">(</span><span class="p" data-group-id="8913848847-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">foot</span><span class="p" data-group-id="8913848847-6">(</span><span class="p" data-group-id="8913848847-6">)</span><span class="w">
│ │ │  </span><span class="n">The</span><span class="w"> </span><span class="ss">return</span><span class="w"> </span><span class="ss">types</span><span class="w"> </span><span class="ss">do</span><span class="w"> </span><span class="ow">not</span><span class="w"> </span><span class="ss">overlap</span></code></pre><p>On the other hand, a nominal type is compatible with a non-opaque, non-nominal
│ │ │  type with the same structure. This compatibility goes both ways, meaning that
│ │ │  passing a structural type when a nominal type is expected is allowed, and
│ │ │ -vice versa.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">qaz</span><span class="p" data-group-id="7643096410-1">(</span><span class="p" data-group-id="7643096410-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="7643096410-2">(</span><span class="p" data-group-id="7643096410-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">qaz</span><span class="p" data-group-id="7643096410-3">(</span><span class="p" data-group-id="7643096410-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">int_to_meter</span><span class="p" data-group-id="7643096410-4">(</span><span class="mi">24</span><span class="p" data-group-id="7643096410-4">)</span><span class="p">.</span></code></pre><p>A type checker that performs nominal type-checking should not raise a warning
│ │ │ +vice versa.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">qaz</span><span class="p" data-group-id="0303472013-1">(</span><span class="p" data-group-id="0303472013-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="0303472013-2">(</span><span class="p" data-group-id="0303472013-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">qaz</span><span class="p" data-group-id="0303472013-3">(</span><span class="p" data-group-id="0303472013-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">int_to_meter</span><span class="p" data-group-id="0303472013-4">(</span><span class="mi">24</span><span class="p" data-group-id="0303472013-4">)</span><span class="p">.</span></code></pre><p>A type checker that performs nominal type-checking should not raise a warning
│ │ │  in this case. The specification says that <code class="inline">qaz/0</code> should return an <code class="inline">integer()</code>
│ │ │  type. However, the function <code class="inline">int_to_meter/1</code> returns a <code class="inline">meter()</code> type, so
│ │ │  <code class="inline">qaz/0</code> will also return a <code class="inline">meter()</code> type. <code class="inline">integer()</code> is not a nominal type.
│ │ │  The structure of <code class="inline">meter()</code> is compatible with <code class="inline">integer()</code>. Dialyzer can
│ │ │  analyze the function above without raising a warning.</p><p>There is one exception where two nominal types with different names can be
│ │ │  compatible: when one is derived from the other. For nominal types <code class="inline">s()</code> and
│ │ │ -<code class="inline">t()</code>, <code class="inline">s()</code> can be derived from <code class="inline">t()</code> in the two following ways:</p><ol><li>If <code class="inline">s()</code> is directly derived from <code class="inline">t()</code>.</li></ol><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">s</span><span class="p" data-group-id="5291612187-1">(</span><span class="p" data-group-id="5291612187-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">t</span><span class="p" data-group-id="5291612187-2">(</span><span class="p" data-group-id="5291612187-2">)</span><span class="p">.</span></code></pre><ol start="2"><li>If <code class="inline">s()</code> is derived from other nominal types, which are derived from <code class="inline">t()</code>.</li></ol><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">s</span><span class="p" data-group-id="2490776042-1">(</span><span class="p" data-group-id="2490776042-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">nominal_1</span><span class="p" data-group-id="2490776042-2">(</span><span class="p" data-group-id="2490776042-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">nominal_1</span><span class="p" data-group-id="2490776042-3">(</span><span class="p" data-group-id="2490776042-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">nominal_2</span><span class="p" data-group-id="2490776042-4">(</span><span class="p" data-group-id="2490776042-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">nominal_2</span><span class="p" data-group-id="2490776042-5">(</span><span class="p" data-group-id="2490776042-5">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">t</span><span class="p" data-group-id="2490776042-6">(</span><span class="p" data-group-id="2490776042-6">)</span><span class="p">.</span></code></pre><p>In both cases, <code class="inline">s()</code> and <code class="inline">t()</code> are compatible nominal types even though they
│ │ │ +<code class="inline">t()</code>, <code class="inline">s()</code> can be derived from <code class="inline">t()</code> in the two following ways:</p><ol><li>If <code class="inline">s()</code> is directly derived from <code class="inline">t()</code>.</li></ol><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">s</span><span class="p" data-group-id="8131890516-1">(</span><span class="p" data-group-id="8131890516-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">t</span><span class="p" data-group-id="8131890516-2">(</span><span class="p" data-group-id="8131890516-2">)</span><span class="p">.</span></code></pre><ol start="2"><li>If <code class="inline">s()</code> is derived from other nominal types, which are derived from <code class="inline">t()</code>.</li></ol><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">s</span><span class="p" data-group-id="8496644517-1">(</span><span class="p" data-group-id="8496644517-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">nominal_1</span><span class="p" data-group-id="8496644517-2">(</span><span class="p" data-group-id="8496644517-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">nominal_1</span><span class="p" data-group-id="8496644517-3">(</span><span class="p" data-group-id="8496644517-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">nominal_2</span><span class="p" data-group-id="8496644517-4">(</span><span class="p" data-group-id="8496644517-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">nominal_2</span><span class="p" data-group-id="8496644517-5">(</span><span class="p" data-group-id="8496644517-5">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">t</span><span class="p" data-group-id="8496644517-6">(</span><span class="p" data-group-id="8496644517-6">)</span><span class="p">.</span></code></pre><p>In both cases, <code class="inline">s()</code> and <code class="inline">t()</code> are compatible nominal types even though they
│ │ │  have different names. Defining them in different modules does not affect
│ │ │  compatibility.</p><p>In summary, nominal type-checking rules are as follows:</p><p>A function that has a <code class="inline">-spec</code> that states an argument or a return type to be
│ │ │  nominal type <code class="inline">a/0</code> (or any other arity), accepts or may return:</p><ul><li>Nominal type <code class="inline">a/0</code></li><li>A compatible nominal type <code class="inline">b/0</code></li><li>A compatible structural type</li></ul><p>A function that has a <code class="inline">-spec</code> that states an argument or a return type to be a
│ │ │  structural type <code class="inline">b/0</code> (or any other arity), accepts or may return:</p><ul><li>A compatible structural type</li><li>A compatible nominal type</li></ul><p><strong>When deciding if a type should be nominal, here are some suggestions:</strong></p><ul><li>If there are other types in the same module with the same structure, and they
│ │ │  should never be mixed, all of them can benefit from being nominal types.</li><li>If a type represents a unit like meter, second, byte, and so on, defining it
│ │ │  as a nominal type is always more useful than <code class="inline">-type</code>. You get the nice
│ │ │  guarantee that you cannot mix them up with other units defined as nominal
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/opaques.html
│ │ │ @@ -124,24 +124,24 @@
│ │ │  <p>The main use case for opacity in Erlang is to hide the implementation of a data
│ │ │  type, enabling evolving the API while minimizing the risk of breaking consumers.
│ │ │  The runtime does not check opacity. Dialyzer provides some opacity-checking, but
│ │ │  the rest is up to convention.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Since Erlang/OTP 28, Dialyzer checks opaques in their defining module in the
│ │ │  same way as nominals. Outside of the defining module, Dialyzer checks
│ │ │  opaques for opacity violations.</p></section><p>This document explains what Erlang opacity is (and the trade-offs involved) via
│ │ │  the example of the <a href="../../lib/stdlib-8.0/doc/html/sets.html#t:set/0"><code class="inline">sets:set()</code></a> data type. This type <em>was</em>
│ │ │ -defined in the <code class="inline">sets</code> module like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">set</span><span class="p" data-group-id="3509222682-1">(</span><span class="n">Element</span><span class="p" data-group-id="3509222682-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">set</span><span class="p" data-group-id="3509222682-2">{</span><span class="ss">segs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">segs</span><span class="p" data-group-id="3509222682-3">(</span><span class="n">Element</span><span class="p" data-group-id="3509222682-3">)</span><span class="p" data-group-id="3509222682-2">}</span><span class="p">.</span></code></pre><p>OTP 24 changed the definition to the following in
│ │ │ -<a href="https://github.com/erlang/otp/commit/e66941e8d7c47b973dff94c0308ea85a6be1958e">this commit</a>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">set</span><span class="p" data-group-id="7262364148-1">(</span><span class="n">Element</span><span class="p" data-group-id="7262364148-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">set</span><span class="p" data-group-id="7262364148-2">{</span><span class="ss">segs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">segs</span><span class="p" data-group-id="7262364148-3">(</span><span class="n">Element</span><span class="p" data-group-id="7262364148-3">)</span><span class="p" data-group-id="7262364148-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="7262364148-4">#{</span><span class="n">Element</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VALUE</span><span class="p" data-group-id="7262364148-4">}</span><span class="p">.</span></code></pre><p>And this change was safer and more backwards-compatible than if the type had
│ │ │ +defined in the <code class="inline">sets</code> module like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">set</span><span class="p" data-group-id="5944078919-1">(</span><span class="n">Element</span><span class="p" data-group-id="5944078919-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">set</span><span class="p" data-group-id="5944078919-2">{</span><span class="ss">segs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">segs</span><span class="p" data-group-id="5944078919-3">(</span><span class="n">Element</span><span class="p" data-group-id="5944078919-3">)</span><span class="p" data-group-id="5944078919-2">}</span><span class="p">.</span></code></pre><p>OTP 24 changed the definition to the following in
│ │ │ +<a href="https://github.com/erlang/otp/commit/e66941e8d7c47b973dff94c0308ea85a6be1958e">this commit</a>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">set</span><span class="p" data-group-id="9989057954-1">(</span><span class="n">Element</span><span class="p" data-group-id="9989057954-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">set</span><span class="p" data-group-id="9989057954-2">{</span><span class="ss">segs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">segs</span><span class="p" data-group-id="9989057954-3">(</span><span class="n">Element</span><span class="p" data-group-id="9989057954-3">)</span><span class="p" data-group-id="9989057954-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="9989057954-4">#{</span><span class="n">Element</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VALUE</span><span class="p" data-group-id="9989057954-4">}</span><span class="p">.</span></code></pre><p>And this change was safer and more backwards-compatible than if the type had
│ │ │  been defined with <code class="inline">-type</code> instead of <code class="inline">-opaque</code>. Here is why: when a module
│ │ │  defines an <code class="inline">-opaque</code>, the contract is that only the defining module should rely
│ │ │  on the definition of the type: no other modules should rely on the definition.</p><p>This means that code that pattern-matched on <code class="inline">set</code> as a record/tuple technically
│ │ │  broke the contract, and opted in to being potentially broken when the definition
│ │ │  of <code class="inline">set()</code> changed. Before OTP 24, this code printed <code class="inline">ok</code>. In OTP 24 it may
│ │ │ -error:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">sets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="4532657862-1">(</span><span class="p" data-group-id="4532657862-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="n">Set</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_tuple</span><span class="p" data-group-id="4532657862-2">(</span><span class="n">Set</span><span class="p" data-group-id="4532657862-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4532657862-3">(</span><span class="s">&quot;ok&quot;</span><span class="p" data-group-id="4532657862-3">)</span><span class="w">
│ │ │ +error:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">sets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="9280755682-1">(</span><span class="p" data-group-id="9280755682-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="n">Set</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_tuple</span><span class="p" data-group-id="9280755682-2">(</span><span class="n">Set</span><span class="p" data-group-id="9280755682-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9280755682-3">(</span><span class="s">&quot;ok&quot;</span><span class="p" data-group-id="9280755682-3">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p><strong>When working with an opaque defined in another module, here are some
│ │ │  recommendations:</strong></p><ul><li>Don't examine the underlying type using pattern-matching, guards, or functions
│ │ │  that reveal the type, such as <a href="../../erts-17.0/doc/html/erlang.html#tuple_size/1"><code class="inline">tuple_size/1</code></a>. One exception
│ │ │  is that <code class="inline">=:=</code> and <code class="inline">=/=</code> can be used between two opaques with the same name, or
│ │ │  between an opaque and <code class="inline">any()</code>, as those comparisons do not reveal underlying
│ │ │  types.</li><li>Use functions provided by the module for working with the type. For
│ │ │  example, the <code class="inline">sets</code> module provides <a href="../../lib/stdlib-8.0/doc/html/sets.html#new/0"><code class="inline">sets:new/0</code></a>, <a href="../../lib/stdlib-8.0/doc/html/sets.html#add_element/2"><code class="inline">sets:add_element/2</code></a>,
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/otp-patch-apply.html
│ │ │ @@ -201,15 +201,15 @@
│ │ │    </a>
│ │ │    <span class="text">Sanity check</span>
│ │ │  </h2>
│ │ │  <p>The application dependencies can be checked using the Erlang shell.
│ │ │  Application dependencies are verified among installed applications by
│ │ │  <code class="inline">otp_patch_apply</code>, but these are not necessarily those actually loaded.
│ │ │  By calling <code class="inline">system_information:sanity_check()</code> one can validate
│ │ │ -dependencies among applications actually loaded.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">system_information</span><span class="p">:</span><span class="nf">sanity_check</span><span class="p" data-group-id="1474909586-1">(</span><span class="p" data-group-id="1474909586-1">)</span><span class="p">.</span><span class="w">
│ │ │ +dependencies among applications actually loaded.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">system_information</span><span class="p">:</span><span class="nf">sanity_check</span><span class="p" data-group-id="7487681303-1">(</span><span class="p" data-group-id="7487681303-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>Please take a look at the reference of <a href="../../lib/runtime_tools-2.4/doc/html/system_information.html#sanity_check/0" title="">sanity_check()</a> for more
│ │ │  information.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/patterns.html
│ │ │ @@ -128,18 +128,18 @@
│ │ │  succeeds, any unbound variables in the pattern become bound. If the matching
│ │ │  fails, an exception is raised.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** 1:1: variable &#39;X&#39; is unbound **</span><span class="w">
│ │ │  </span><span class="gp unselectable">2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">2</span><span class="w">
│ │ │  </span><span class="gp unselectable">3&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="p" data-group-id="6647049129-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6647049129-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6647049129-2">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="6647049129-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="p" data-group-id="6523941916-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6523941916-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6523941916-2">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="6523941916-2">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no match of right hand side value {1,2}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="6647049129-3">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6647049129-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6647049129-4">{</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="6647049129-4">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6647049129-5">{</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6647049129-5">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="p" data-group-id="6523941916-3">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6523941916-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6523941916-4">{</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="6523941916-4">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6523941916-5">{</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6523941916-5">}</span><span class="w">
│ │ │  </span><span class="gp unselectable">6&gt; </span><span class="n">Y</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/prog_ex_records.html
│ │ │ @@ -122,105 +122,105 @@
│ │ │    <span class="text">Records and Tuples</span>
│ │ │  </h2>
│ │ │  <p>The main advantage of using records rather than tuples is that fields in a
│ │ │  record are accessed by name, whereas fields in a tuple are accessed by position.
│ │ │  To illustrate these differences, suppose that you want to represent a person
│ │ │  with the tuple <code class="inline">{Name, Address, Phone}</code>.</p><p>To write functions that manipulate this data, remember the following:</p><ul><li>The <code class="inline">Name</code> field is the first element of the tuple.</li><li>The <code class="inline">Address</code> field is the second element.</li><li>The <code class="inline">Phone</code> field is the third element.</li></ul><p>For example, to extract data from a variable <code class="inline">P</code> that contains such a tuple, you
│ │ │  can write the following code and then use pattern matching to extract the
│ │ │ -relevant fields:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">element</span><span class="p" data-group-id="8885450940-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">P</span><span class="p" data-group-id="8885450940-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">element</span><span class="p" data-group-id="8885450940-2">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">P</span><span class="p" data-group-id="8885450940-2">)</span><span class="p">,</span><span class="w">
│ │ │ +relevant fields:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">element</span><span class="p" data-group-id="4602390465-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">P</span><span class="p" data-group-id="4602390465-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">element</span><span class="p" data-group-id="4602390465-2">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">P</span><span class="p" data-group-id="4602390465-2">)</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Such code is difficult to read and understand, and errors occur if the numbering
│ │ │  of the elements in the tuple is wrong. If the data representation of the fields
│ │ │  is changed, by re-ordering, adding, or removing fields, all references to the
│ │ │  person tuple must be checked and possibly modified.</p><p>Records allow references to the fields by name, instead of by position. In the
│ │ │ -following example, a record instead of a tuple is used to store the data:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0046256378-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0046256378-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="0046256378-2">}</span><span class="p" data-group-id="0046256378-1">)</span><span class="p">.</span></code></pre><p>This enables references to the fields of the record by name. For example, if <code class="inline">P</code>
│ │ │ +following example, a record instead of a tuple is used to store the data:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="3570650260-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3570650260-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="3570650260-2">}</span><span class="p" data-group-id="3570650260-1">)</span><span class="p">.</span></code></pre><p>This enables references to the fields of the record by name. For example, if <code class="inline">P</code>
│ │ │  is a variable whose value is a <code class="inline">person</code> record, the following code accesses the
│ │ │  name and address fields of the record:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="n">Address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">address</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Internally, records are represented using tagged tuples:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6709444625-1">{</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="n">Address</span><span class="p" data-group-id="6709444625-1">}</span></code></pre><h2 id="defining-a-record" class="section-heading">
│ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Internally, records are represented using tagged tuples:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0865975274-1">{</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="n">Address</span><span class="p" data-group-id="0865975274-1">}</span></code></pre><h2 id="defining-a-record" class="section-heading">
│ │ │    <a href="#defining-a-record" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Defining a Record</span>
│ │ │  </h2>
│ │ │  <p>The following definition of a <code class="inline">person</code> is used in several examples in this
│ │ │  section. Three fields are included, <code class="inline">name</code>, <code class="inline">phone</code>, and <code class="inline">address</code>. The default
│ │ │  values for <code class="inline">name</code> and <code class="inline">phone</code> are &quot;&quot; and [], respectively. The default value for
│ │ │  <code class="inline">address</code> is the atom <code class="inline">undefined</code>, since no default value is supplied for this
│ │ │ -field:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6945685414-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6945685414-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6945685414-3">[</span><span class="p" data-group-id="6945685414-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="6945685414-2">}</span><span class="p" data-group-id="6945685414-1">)</span><span class="p">.</span></code></pre><p>The record must be defined in the shell to enable use of the record syntax in
│ │ │ -the examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">rd</span><span class="p" data-group-id="5941814236-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5941814236-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5941814236-3">[</span><span class="p" data-group-id="5941814236-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="5941814236-2">}</span><span class="p" data-group-id="5941814236-1">)</span><span class="p">.</span><span class="w">
│ │ │ +field:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5810658005-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5810658005-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5810658005-3">[</span><span class="p" data-group-id="5810658005-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="5810658005-2">}</span><span class="p" data-group-id="5810658005-1">)</span><span class="p">.</span></code></pre><p>The record must be defined in the shell to enable use of the record syntax in
│ │ │ +the examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">rd</span><span class="p" data-group-id="2148185122-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2148185122-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2148185122-3">[</span><span class="p" data-group-id="2148185122-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="2148185122-2">}</span><span class="p" data-group-id="2148185122-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">person</span></code></pre><p>This is because record definitions are only available at compile time, not at
│ │ │  runtime. For details on records in the shell, see the <a href="../../lib/stdlib-8.0/doc/html/shell.html"><code class="inline">shell</code></a> manual page in
│ │ │  STDLIB.</p><h2 id="creating-a-record" class="section-heading">
│ │ │    <a href="#creating-a-record" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Creating a Record</span>
│ │ │  </h2>
│ │ │ -<p>A new <code class="inline">person</code> record is created as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5224918893-1">{</span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="5224918893-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5224918893-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p" data-group-id="5224918893-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5224918893-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5224918893-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5224918893-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">undefined</span><span class="p" data-group-id="5224918893-3">}</span></code></pre><p>As the <code class="inline">address</code> field was omitted, its default value is used.</p><p>From Erlang 5.1/OTP R8B, a value to all fields in a record can be set with the
│ │ │ -special field <code class="inline">_</code>. <code class="inline">_</code> means &quot;all fields not explicitly specified&quot;.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5767063340-1">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Jakob&quot;</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="5767063340-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5767063340-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Jakob&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="5767063340-2">}</span></code></pre><p>It is primarily intended to be used in <a href="../../lib/stdlib-8.0/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a> and
│ │ │ +<p>A new <code class="inline">person</code> record is created as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3829076025-1">{</span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="3829076025-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3829076025-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p" data-group-id="3829076025-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3829076025-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3829076025-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3829076025-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">undefined</span><span class="p" data-group-id="3829076025-3">}</span></code></pre><p>As the <code class="inline">address</code> field was omitted, its default value is used.</p><p>From Erlang 5.1/OTP R8B, a value to all fields in a record can be set with the
│ │ │ +special field <code class="inline">_</code>. <code class="inline">_</code> means &quot;all fields not explicitly specified&quot;.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9441858309-1">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Jakob&quot;</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="9441858309-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9441858309-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Jakob&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="9441858309-2">}</span></code></pre><p>It is primarily intended to be used in <a href="../../lib/stdlib-8.0/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a> and
│ │ │  <a href="../../lib/mnesia-4.26/doc/html/mnesia.html#match_object/3"><code class="inline">mnesia:match_object/3</code></a>, to set record fields to the atom <code class="inline">'_'</code>. (This is a
│ │ │  wildcard in <a href="../../lib/stdlib-8.0/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a>.)</p><h2 id="accessing-a-record-field" class="section-heading">
│ │ │    <a href="#accessing-a-record-field" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Accessing a Record Field</span>
│ │ │  </h2>
│ │ │ -<p>The following example shows how to access a record field:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6830903482-1">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6830903482-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6830903482-2">]</span><span class="p" data-group-id="6830903482-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6830903482-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6830903482-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6830903482-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">undefined</span><span class="p" data-group-id="6830903482-3">}</span><span class="w">
│ │ │ +<p>The following example shows how to access a record field:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="4474752348-1">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4474752348-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4474752348-2">]</span><span class="p" data-group-id="4474752348-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="4474752348-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4474752348-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4474752348-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">undefined</span><span class="p" data-group-id="4474752348-3">}</span><span class="w">
│ │ │  </span><span class="gp unselectable">&gt; </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;Joe&quot;</span></code></pre><h2 id="updating-a-record" class="section-heading">
│ │ │    <a href="#updating-a-record" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Updating a Record</span>
│ │ │  </h2>
│ │ │ -<p>The following example shows how to update a record:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8733786842-1">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="8733786842-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8733786842-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="o">=</span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="8733786842-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8733786842-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8733786842-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8733786842-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="8733786842-3">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">P2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P1</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8733786842-5">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p" data-group-id="8733786842-5">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8733786842-6">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8733786842-7">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8733786842-7">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="8733786842-6">}</span></code></pre><h2 id="type-testing" class="section-heading">
│ │ │ +<p>The following example shows how to update a record:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5286265344-1">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="5286265344-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5286265344-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="o">=</span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="5286265344-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5286265344-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5286265344-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5286265344-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="5286265344-3">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">P2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P1</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5286265344-5">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p" data-group-id="5286265344-5">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5286265344-6">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5286265344-7">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5286265344-7">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="5286265344-6">}</span></code></pre><h2 id="type-testing" class="section-heading">
│ │ │    <a href="#type-testing" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Type Testing</span>
│ │ │  </h2>
│ │ │  <p>The following example shows that the guard succeeds if <code class="inline">P</code> is a record of type
│ │ │ -<code class="inline">person</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="9997187682-1">(</span><span class="n">P</span><span class="p" data-group-id="9997187682-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="9997187682-2">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="9997187682-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">a_person</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="9997187682-3">(</span><span class="p">_</span><span class="p" data-group-id="9997187682-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">not_a_person</span><span class="p">.</span></code></pre><h2 id="pattern-matching" class="section-heading">
│ │ │ +<code class="inline">person</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="5464389391-1">(</span><span class="n">P</span><span class="p" data-group-id="5464389391-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="5464389391-2">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="5464389391-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">a_person</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="5464389391-3">(</span><span class="p">_</span><span class="p" data-group-id="5464389391-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">not_a_person</span><span class="p">.</span></code></pre><h2 id="pattern-matching" class="section-heading">
│ │ │    <a href="#pattern-matching" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Pattern Matching</span>
│ │ │  </h2>
│ │ │  <p>Matching can be used in combination with records, as shown in the following
│ │ │ -example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5347084087-1">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="5347084087-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="5347084087-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="o">=</span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="5347084087-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5347084087-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5347084087-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="5347084087-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="5347084087-3">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5347084087-5">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5347084087-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P3</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">.</span><span class="w">
│ │ │ +example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7218000421-1">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="7218000421-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="7218000421-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="o">=</span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="7218000421-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7218000421-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7218000421-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="7218000421-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="7218000421-3">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7218000421-5">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="7218000421-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P3</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;Joe&quot;</span></code></pre><p>The following function takes a list of <code class="inline">person</code> records and searches for the
│ │ │ -phone number of a person with a particular name:</p><pre><code class="makeup erlang" translate="no"><span class="nf">find_phone</span><span class="p" data-group-id="4987248575-1">(</span><span class="p" data-group-id="4987248575-2">[</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="4987248575-3">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="n">Phone</span><span class="p" data-group-id="4987248575-3">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="4987248575-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="4987248575-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4987248575-4">{</span><span class="ss">found</span><span class="p">,</span><span class="w">  </span><span class="n">Phone</span><span class="p" data-group-id="4987248575-4">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">find_phone</span><span class="p" data-group-id="4987248575-5">(</span><span class="p" data-group-id="4987248575-6">[</span><span class="p">_</span><span class="p">|</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="4987248575-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="4987248575-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">find_phone</span><span class="p" data-group-id="4987248575-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="4987248575-7">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">find_phone</span><span class="p" data-group-id="4987248575-8">(</span><span class="p" data-group-id="4987248575-9">[</span><span class="p" data-group-id="4987248575-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="4987248575-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +phone number of a person with a particular name:</p><pre><code class="makeup erlang" translate="no"><span class="nf">find_phone</span><span class="p" data-group-id="9800942189-1">(</span><span class="p" data-group-id="9800942189-2">[</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9800942189-3">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="n">Phone</span><span class="p" data-group-id="9800942189-3">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9800942189-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9800942189-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9800942189-4">{</span><span class="ss">found</span><span class="p">,</span><span class="w">  </span><span class="n">Phone</span><span class="p" data-group-id="9800942189-4">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">find_phone</span><span class="p" data-group-id="9800942189-5">(</span><span class="p" data-group-id="9800942189-6">[</span><span class="p">_</span><span class="p">|</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="9800942189-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9800942189-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">find_phone</span><span class="p" data-group-id="9800942189-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9800942189-7">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">find_phone</span><span class="p" data-group-id="9800942189-8">(</span><span class="p" data-group-id="9800942189-9">[</span><span class="p" data-group-id="9800942189-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9800942189-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">not_found</span><span class="p">.</span></code></pre><p>The fields referred to in the pattern can be given in any order.</p><h2 id="nested-records" class="section-heading">
│ │ │    <a href="#nested-records" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Nested Records</span>
│ │ │  </h2>
│ │ │  <p>The value of a field in a record can be an instance of a record. Retrieval of
│ │ │  nested data can be done stepwise, or in a single step, as shown in the following
│ │ │ -example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5455513414-1">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5455513414-2">{</span><span class="ss">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">last</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Ericsson&quot;</span><span class="p" data-group-id="5455513414-2">}</span><span class="p" data-group-id="5455513414-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5455513414-3">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5455513414-4">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">name</span><span class="p" data-group-id="5455513414-5">{</span><span class="p" data-group-id="5455513414-5">}</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p" data-group-id="5455513414-4">}</span><span class="p" data-group-id="5455513414-3">)</span><span class="p">.</span><span class="w">
│ │ │ +example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0555057717-1">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0555057717-2">{</span><span class="ss">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">last</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Ericsson&quot;</span><span class="p" data-group-id="0555057717-2">}</span><span class="p" data-group-id="0555057717-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0555057717-3">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0555057717-4">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">name</span><span class="p" data-group-id="0555057717-5">{</span><span class="p" data-group-id="0555057717-5">}</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p" data-group-id="0555057717-4">}</span><span class="p" data-group-id="0555057717-3">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">demo</span><span class="p" data-group-id="5455513414-6">(</span><span class="p" data-group-id="5455513414-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5455513414-7">{</span><span class="ss">name</span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">name</span><span class="p" data-group-id="5455513414-8">{</span><span class="ss">first</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">last</span><span class="o">=</span><span class="s">&quot;Virding&quot;</span><span class="p" data-group-id="5455513414-8">}</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="mi">123</span><span class="p" data-group-id="5455513414-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="n">First</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5455513414-9">(</span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="5455513414-9">)</span><span class="o">#</span><span class="ss">name</span><span class="p">.</span><span class="ss">first</span><span class="p">.</span></code></pre><p>Here, <code class="inline">demo()</code> evaluates to <code class="inline">&quot;Robert&quot;</code>.</p><h2 id="a-longer-example" class="section-heading">
│ │ │ +</span><span class="nf">demo</span><span class="p" data-group-id="0555057717-6">(</span><span class="p" data-group-id="0555057717-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="0555057717-7">{</span><span class="ss">name</span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">name</span><span class="p" data-group-id="0555057717-8">{</span><span class="ss">first</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">last</span><span class="o">=</span><span class="s">&quot;Virding&quot;</span><span class="p" data-group-id="0555057717-8">}</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="mi">123</span><span class="p" data-group-id="0555057717-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="n">First</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0555057717-9">(</span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="0555057717-9">)</span><span class="o">#</span><span class="ss">name</span><span class="p">.</span><span class="ss">first</span><span class="p">.</span></code></pre><p>Here, <code class="inline">demo()</code> evaluates to <code class="inline">&quot;Robert&quot;</code>.</p><h2 id="a-longer-example" class="section-heading">
│ │ │    <a href="#a-longer-example" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">A Longer Example</span>
│ │ │  </h2>
│ │ │  <p>Comments are embedded in the following example:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% File: person.hrl</span><span class="w">
│ │ │  
│ │ │ @@ -230,48 +230,48 @@
│ │ │  </span><span class="c1">%%    name:  A string (default is undefined).</span><span class="w">
│ │ │  </span><span class="c1">%%    age:   An integer (default is undefined).</span><span class="w">
│ │ │  </span><span class="c1">%%    phone: A list of integers (default is []).</span><span class="w">
│ │ │  </span><span class="c1">%%    dict:  A dictionary containing various information</span><span class="w">
│ │ │  </span><span class="c1">%%           about the person.</span><span class="w">
│ │ │  </span><span class="c1">%%           A {Key, Value} list (default is the empty list).</span><span class="w">
│ │ │  </span><span class="c1">%%------------------------------------------------------------</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="3412531021-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3412531021-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3412531021-3">[</span><span class="p" data-group-id="3412531021-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3412531021-4">[</span><span class="p" data-group-id="3412531021-4">]</span><span class="p" data-group-id="3412531021-2">}</span><span class="p" data-group-id="3412531021-1">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6877058141-1">(</span><span class="ss">person</span><span class="p" data-group-id="6877058141-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="6877058141-2">(</span><span class="s">&quot;person.hrl&quot;</span><span class="p" data-group-id="6877058141-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="6877058141-3">(</span><span class="ss">export_all</span><span class="p" data-group-id="6877058141-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% For test purposes only.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9376280951-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9376280951-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9376280951-3">[</span><span class="p" data-group-id="9376280951-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9376280951-4">[</span><span class="p" data-group-id="9376280951-4">]</span><span class="p" data-group-id="9376280951-2">}</span><span class="p" data-group-id="9376280951-1">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7440026253-1">(</span><span class="ss">person</span><span class="p" data-group-id="7440026253-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="7440026253-2">(</span><span class="s">&quot;person.hrl&quot;</span><span class="p" data-group-id="7440026253-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="7440026253-3">(</span><span class="ss">export_all</span><span class="p" data-group-id="7440026253-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% For test purposes only.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% This creates an instance of a person.</span><span class="w">
│ │ │  </span><span class="c1">%%   Note: The phone number is not supplied so the</span><span class="w">
│ │ │  </span><span class="c1">%%         default value [] will be used.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">make_hacker_without_phone</span><span class="p" data-group-id="6877058141-4">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="6877058141-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6877058141-5">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w">
│ │ │ -           </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6877058141-6">[</span><span class="p" data-group-id="6877058141-7">{</span><span class="ss">computer_knowledge</span><span class="p">,</span><span class="w"> </span><span class="ss">excellent</span><span class="p" data-group-id="6877058141-7">}</span><span class="p">,</span><span class="w">
│ │ │ -                   </span><span class="p" data-group-id="6877058141-8">{</span><span class="ss">drinks</span><span class="p">,</span><span class="w"> </span><span class="ss">coke</span><span class="p" data-group-id="6877058141-8">}</span><span class="p" data-group-id="6877058141-6">]</span><span class="p" data-group-id="6877058141-5">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">make_hacker_without_phone</span><span class="p" data-group-id="7440026253-4">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="7440026253-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7440026253-5">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w">
│ │ │ +           </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7440026253-6">[</span><span class="p" data-group-id="7440026253-7">{</span><span class="ss">computer_knowledge</span><span class="p">,</span><span class="w"> </span><span class="ss">excellent</span><span class="p" data-group-id="7440026253-7">}</span><span class="p">,</span><span class="w">
│ │ │ +                   </span><span class="p" data-group-id="7440026253-8">{</span><span class="ss">drinks</span><span class="p">,</span><span class="w"> </span><span class="ss">coke</span><span class="p" data-group-id="7440026253-8">}</span><span class="p" data-group-id="7440026253-6">]</span><span class="p" data-group-id="7440026253-5">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% This demonstrates matching in arguments</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">print</span><span class="p" data-group-id="6877058141-9">(</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6877058141-10">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dict</span><span class="p" data-group-id="6877058141-10">}</span><span class="p" data-group-id="6877058141-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6877058141-11">(</span><span class="s">&quot;Name: </span><span class="si">~s</span><span class="s">, Age: </span><span class="si">~w</span><span class="s">, Phone: </span><span class="si">~w</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="w">
│ │ │ -            </span><span class="s">&quot;Dictionary: </span><span class="si">~w</span><span class="s">.</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6877058141-12">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="n">Dict</span><span class="p" data-group-id="6877058141-12">]</span><span class="p" data-group-id="6877058141-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">print</span><span class="p" data-group-id="7440026253-9">(</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7440026253-10">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dict</span><span class="p" data-group-id="7440026253-10">}</span><span class="p" data-group-id="7440026253-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7440026253-11">(</span><span class="s">&quot;Name: </span><span class="si">~s</span><span class="s">, Age: </span><span class="si">~w</span><span class="s">, Phone: </span><span class="si">~w</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="w">
│ │ │ +            </span><span class="s">&quot;Dictionary: </span><span class="si">~w</span><span class="s">.</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7440026253-12">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="n">Dict</span><span class="p" data-group-id="7440026253-12">]</span><span class="p" data-group-id="7440026253-11">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% Demonstrates type testing, selector, updating.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">birthday</span><span class="p" data-group-id="6877058141-13">(</span><span class="n">P</span><span class="p" data-group-id="6877058141-13">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="6877058141-14">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="6877058141-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6877058141-15">{</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="6877058141-15">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">birthday</span><span class="p" data-group-id="7440026253-13">(</span><span class="n">P</span><span class="p" data-group-id="7440026253-13">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="7440026253-14">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="7440026253-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7440026253-15">{</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="7440026253-15">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">register_two_hackers</span><span class="p" data-group-id="6877058141-16">(</span><span class="p" data-group-id="6877058141-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="n">Hacker1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_hacker_without_phone</span><span class="p" data-group-id="6877058141-17">(</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">29</span><span class="p" data-group-id="6877058141-17">)</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="n">OldHacker</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">birthday</span><span class="p" data-group-id="6877058141-18">(</span><span class="n">Hacker1</span><span class="p" data-group-id="6877058141-18">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">register_two_hackers</span><span class="p" data-group-id="7440026253-16">(</span><span class="p" data-group-id="7440026253-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="n">Hacker1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_hacker_without_phone</span><span class="p" data-group-id="7440026253-17">(</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">29</span><span class="p" data-group-id="7440026253-17">)</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="n">OldHacker</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">birthday</span><span class="p" data-group-id="7440026253-18">(</span><span class="n">Hacker1</span><span class="p" data-group-id="7440026253-18">)</span><span class="p">,</span><span class="w">
│ │ │     </span><span class="c1">% The central_register_server should have</span><span class="w">
│ │ │     </span><span class="c1">% an interface function for this.</span><span class="w">
│ │ │ -   </span><span class="ss">central_register_server</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6877058141-19">{</span><span class="ss">register_person</span><span class="p">,</span><span class="w"> </span><span class="n">Hacker1</span><span class="p" data-group-id="6877058141-19">}</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="ss">central_register_server</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6877058141-20">{</span><span class="ss">register_person</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="n">OldHacker</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6877058141-21">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="w">
│ │ │ -                              </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6877058141-22">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6877058141-22">]</span><span class="p" data-group-id="6877058141-21">}</span><span class="p" data-group-id="6877058141-20">}</span><span class="p">.</span></code></pre>
│ │ │ +   </span><span class="ss">central_register_server</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7440026253-19">{</span><span class="ss">register_person</span><span class="p">,</span><span class="w"> </span><span class="n">Hacker1</span><span class="p" data-group-id="7440026253-19">}</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="ss">central_register_server</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7440026253-20">{</span><span class="ss">register_person</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="n">OldHacker</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7440026253-21">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="w">
│ │ │ +                              </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7440026253-22">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="7440026253-22">]</span><span class="p" data-group-id="7440026253-21">}</span><span class="p" data-group-id="7440026253-20">}</span><span class="p">.</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="programming_examples.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/records_macros.html
│ │ │ @@ -124,40 +124,40 @@
│ │ │  </h2>
│ │ │  <p>To illustrate this, the messenger example from the previous section is divided
│ │ │  into the following five files:</p><ul><li><p><code class="inline">mess_config.hrl</code></p><p>Header file for configuration data</p></li><li><p><code class="inline">mess_interface.hrl</code></p><p>Interface definitions between the client and the messenger</p></li><li><p><code class="inline">user_interface.erl</code></p><p>Functions for the user interface</p></li><li><p><code class="inline">mess_client.erl</code></p><p>Functions for the client side of the messenger</p></li><li><p><code class="inline">mess_server.erl</code></p><p>Functions for the server side of the messenger</p></li></ul><p>While doing this, the message passing interface between the shell, the client,
│ │ │  and the server is cleaned up and is defined using <em>records</em>. Also, <em>macros</em> are
│ │ │  introduced:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE mess_config.hrl----</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Configure the location of the server node,</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9684929770-1">(</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="9684929770-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7298245182-1">(</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="7298245182-1">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%%----END FILE-----</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE mess_interface.hrl----</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Message interface between client and server and client shell for</span><span class="w">
│ │ │  </span><span class="c1">%%% messenger program</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%%Messages from Client to server received in server/1 function.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1293342488-1">(</span><span class="ss">logon</span><span class="p">,</span><span class="p" data-group-id="1293342488-2">{</span><span class="ss">client_pid</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="p" data-group-id="1293342488-2">}</span><span class="p" data-group-id="1293342488-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1293342488-3">(</span><span class="ss">message</span><span class="p">,</span><span class="p" data-group-id="1293342488-4">{</span><span class="ss">client_pid</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="1293342488-4">}</span><span class="p" data-group-id="1293342488-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7242380194-1">(</span><span class="ss">logon</span><span class="p">,</span><span class="p" data-group-id="7242380194-2">{</span><span class="ss">client_pid</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="p" data-group-id="7242380194-2">}</span><span class="p" data-group-id="7242380194-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7242380194-3">(</span><span class="ss">message</span><span class="p">,</span><span class="p" data-group-id="7242380194-4">{</span><span class="ss">client_pid</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="7242380194-4">}</span><span class="p" data-group-id="7242380194-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%% {&#39;EXIT&#39;, ClientPid, Reason}  (client terminated or unreachable.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Messages from Server to Client, received in await_result/0 function</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1293342488-5">(</span><span class="ss">abort_client</span><span class="p">,</span><span class="p" data-group-id="1293342488-6">{</span><span class="ss">message</span><span class="p" data-group-id="1293342488-6">}</span><span class="p" data-group-id="1293342488-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7242380194-5">(</span><span class="ss">abort_client</span><span class="p">,</span><span class="p" data-group-id="7242380194-6">{</span><span class="ss">message</span><span class="p" data-group-id="7242380194-6">}</span><span class="p" data-group-id="7242380194-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%% Messages are: user_exists_at_other_node,</span><span class="w">
│ │ │  </span><span class="c1">%%%               you_are_not_logged_on</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1293342488-7">(</span><span class="ss">server_reply</span><span class="p">,</span><span class="p" data-group-id="1293342488-8">{</span><span class="ss">message</span><span class="p" data-group-id="1293342488-8">}</span><span class="p" data-group-id="1293342488-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7242380194-7">(</span><span class="ss">server_reply</span><span class="p">,</span><span class="p" data-group-id="7242380194-8">{</span><span class="ss">message</span><span class="p" data-group-id="7242380194-8">}</span><span class="p" data-group-id="7242380194-7">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%% Messages are: logged_on</span><span class="w">
│ │ │  </span><span class="c1">%%%               receiver_not_found</span><span class="w">
│ │ │  </span><span class="c1">%%%               sent  (Message has been sent (no guarantee)</span><span class="w">
│ │ │  </span><span class="c1">%%% Messages from Server to Client received in client/1 function</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1293342488-9">(</span><span class="ss">message_from</span><span class="p">,</span><span class="p" data-group-id="1293342488-10">{</span><span class="ss">from_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="1293342488-10">}</span><span class="p" data-group-id="1293342488-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7242380194-9">(</span><span class="ss">message_from</span><span class="p">,</span><span class="p" data-group-id="7242380194-10">{</span><span class="ss">from_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="7242380194-10">}</span><span class="p" data-group-id="7242380194-9">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Messages from shell to Client received in client/1 function</span><span class="w">
│ │ │  </span><span class="c1">%%% spawn(mess_client, client, [server_node(), Name])</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1293342488-11">(</span><span class="ss">message_to</span><span class="p">,</span><span class="p" data-group-id="1293342488-12">{</span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="1293342488-12">}</span><span class="p" data-group-id="1293342488-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7242380194-11">(</span><span class="ss">message_to</span><span class="p">,</span><span class="p" data-group-id="7242380194-12">{</span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="7242380194-12">}</span><span class="p" data-group-id="7242380194-11">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%% logoff</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%%----END FILE-----</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE user_interface.erl----</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% User interface to the messenger program</span><span class="w">
│ │ │  </span><span class="c1">%%% login(Name)</span><span class="w">
│ │ │  </span><span class="c1">%%%     One user at a time can log in from each Erlang node in the</span><span class="w">
│ │ │ @@ -170,177 +170,177 @@
│ │ │  </span><span class="c1">%%%     Logs off anybody at that node</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% message(ToName, Message)</span><span class="w">
│ │ │  </span><span class="c1">%%%     sends Message to ToName. Error messages if the user of this</span><span class="w">
│ │ │  </span><span class="c1">%%%     function is not logged on or if ToName is not logged on at</span><span class="w">
│ │ │  </span><span class="c1">%%%     any node.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0533652541-1">(</span><span class="ss">user_interface</span><span class="p" data-group-id="0533652541-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0533652541-2">(</span><span class="p" data-group-id="0533652541-3">[</span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0533652541-3">]</span><span class="p" data-group-id="0533652541-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0533652541-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="0533652541-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0533652541-5">(</span><span class="s">&quot;mess_config.hrl&quot;</span><span class="p" data-group-id="0533652541-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2315906703-1">(</span><span class="ss">user_interface</span><span class="p" data-group-id="2315906703-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2315906703-2">(</span><span class="p" data-group-id="2315906703-3">[</span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2315906703-3">]</span><span class="p" data-group-id="2315906703-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="2315906703-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="2315906703-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="2315906703-5">(</span><span class="s">&quot;mess_config.hrl&quot;</span><span class="p" data-group-id="2315906703-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">logon</span><span class="p" data-group-id="0533652541-6">(</span><span class="n">Name</span><span class="p" data-group-id="0533652541-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="0533652541-7">(</span><span class="ss">mess_client</span><span class="p" data-group-id="0533652541-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">logon</span><span class="p" data-group-id="2315906703-6">(</span><span class="n">Name</span><span class="p" data-group-id="2315906703-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="2315906703-7">(</span><span class="ss">mess_client</span><span class="p" data-group-id="2315906703-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">register</span><span class="p" data-group-id="0533652541-8">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ -                     </span><span class="nf">spawn</span><span class="p" data-group-id="0533652541-9">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0533652541-10">[</span><span class="o">?</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="0533652541-10">]</span><span class="p" data-group-id="0533652541-9">)</span><span class="p" data-group-id="0533652541-8">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="nf">register</span><span class="p" data-group-id="2315906703-8">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ +                     </span><span class="nf">spawn</span><span class="p" data-group-id="2315906703-9">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2315906703-10">[</span><span class="o">?</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="2315906703-10">]</span><span class="p" data-group-id="2315906703-9">)</span><span class="p" data-group-id="2315906703-8">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">already_logged_on</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">logoff</span><span class="p" data-group-id="0533652541-11">(</span><span class="p" data-group-id="0533652541-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">logoff</span><span class="p" data-group-id="2315906703-11">(</span><span class="p" data-group-id="2315906703-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">logoff</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">message</span><span class="p" data-group-id="0533652541-12">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="0533652541-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="0533652541-13">(</span><span class="ss">mess_client</span><span class="p" data-group-id="0533652541-13">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ +</span><span class="nf">message</span><span class="p" data-group-id="2315906703-12">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="2315906703-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="2315906703-13">(</span><span class="ss">mess_client</span><span class="p" data-group-id="2315906703-13">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">not_logged_on</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="0533652541-14">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="0533652541-14">}</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="2315906703-14">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="2315906703-14">}</span><span class="p">,</span><span class="w">
│ │ │               </span><span class="ss">ok</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%%----END FILE-----</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE mess_client.erl----</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% The client process which runs on each user node</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5802107805-1">(</span><span class="ss">mess_client</span><span class="p" data-group-id="5802107805-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5802107805-2">(</span><span class="p" data-group-id="5802107805-3">[</span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5802107805-3">]</span><span class="p" data-group-id="5802107805-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="5802107805-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="5802107805-4">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="5802107805-5">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5802107805-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5802107805-6">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="5802107805-6">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">logon</span><span class="p" data-group-id="5802107805-7">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="nf">self</span><span class="p" data-group-id="5802107805-8">(</span><span class="p" data-group-id="5802107805-8">)</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="o">=</span><span class="n">Name</span><span class="p" data-group-id="5802107805-7">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">await_result</span><span class="p" data-group-id="5802107805-9">(</span><span class="p" data-group-id="5802107805-9">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="5802107805-10">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5802107805-10">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6602740827-1">(</span><span class="ss">mess_client</span><span class="p" data-group-id="6602740827-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6602740827-2">(</span><span class="p" data-group-id="6602740827-3">[</span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6602740827-3">]</span><span class="p" data-group-id="6602740827-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="6602740827-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="6602740827-4">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="6602740827-5">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6602740827-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6602740827-6">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="6602740827-6">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">logon</span><span class="p" data-group-id="6602740827-7">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="nf">self</span><span class="p" data-group-id="6602740827-8">(</span><span class="p" data-group-id="6602740827-8">)</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="o">=</span><span class="n">Name</span><span class="p" data-group-id="6602740827-7">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">await_result</span><span class="p" data-group-id="6602740827-9">(</span><span class="p" data-group-id="6602740827-9">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="6602740827-10">(</span><span class="n">Server_Node</span><span class="p" data-group-id="6602740827-10">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="5802107805-11">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5802107805-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="6602740827-11">(</span><span class="n">Server_Node</span><span class="p" data-group-id="6602740827-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">logoff</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="5802107805-12">(</span><span class="ss">normal</span><span class="p" data-group-id="5802107805-12">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="5802107805-13">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="5802107805-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="5802107805-14">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="5802107805-14">}</span><span class="w"> </span><span class="o">!</span><span class="w">
│ │ │ -                </span><span class="o">#</span><span class="ss">message</span><span class="p" data-group-id="5802107805-15">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="nf">self</span><span class="p" data-group-id="5802107805-16">(</span><span class="p" data-group-id="5802107805-16">)</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="5802107805-15">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">await_result</span><span class="p" data-group-id="5802107805-17">(</span><span class="p" data-group-id="5802107805-17">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5802107805-18">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5802107805-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5802107805-19">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5802107805-20">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5802107805-20">]</span><span class="p" data-group-id="5802107805-19">)</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="6602740827-12">(</span><span class="ss">normal</span><span class="p" data-group-id="6602740827-12">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="6602740827-13">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="6602740827-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="6602740827-14">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="6602740827-14">}</span><span class="w"> </span><span class="o">!</span><span class="w">
│ │ │ +                </span><span class="o">#</span><span class="ss">message</span><span class="p" data-group-id="6602740827-15">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="nf">self</span><span class="p" data-group-id="6602740827-16">(</span><span class="p" data-group-id="6602740827-16">)</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="6602740827-15">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">await_result</span><span class="p" data-group-id="6602740827-17">(</span><span class="p" data-group-id="6602740827-17">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="6602740827-18">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6602740827-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6602740827-19">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6602740827-20">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6602740827-20">]</span><span class="p" data-group-id="6602740827-19">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="5802107805-21">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5802107805-21">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="6602740827-21">(</span><span class="n">Server_Node</span><span class="p" data-group-id="6602740827-21">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% wait for a response from the server</span><span class="w">
│ │ │ -</span><span class="nf">await_result</span><span class="p" data-group-id="5802107805-22">(</span><span class="p" data-group-id="5802107805-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">await_result</span><span class="p" data-group-id="6602740827-22">(</span><span class="p" data-group-id="6602740827-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="5802107805-23">{</span><span class="ss">message</span><span class="o">=</span><span class="n">Why</span><span class="p" data-group-id="5802107805-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5802107805-24">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5802107805-25">[</span><span class="n">Why</span><span class="p" data-group-id="5802107805-25">]</span><span class="p" data-group-id="5802107805-24">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="5802107805-26">(</span><span class="ss">normal</span><span class="p" data-group-id="5802107805-26">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="5802107805-27">{</span><span class="ss">message</span><span class="o">=</span><span class="n">What</span><span class="p" data-group-id="5802107805-27">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5802107805-28">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5802107805-29">[</span><span class="n">What</span><span class="p" data-group-id="5802107805-29">]</span><span class="p" data-group-id="5802107805-28">)</span><span class="w">
│ │ │ +        </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="6602740827-23">{</span><span class="ss">message</span><span class="o">=</span><span class="n">Why</span><span class="p" data-group-id="6602740827-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6602740827-24">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6602740827-25">[</span><span class="n">Why</span><span class="p" data-group-id="6602740827-25">]</span><span class="p" data-group-id="6602740827-24">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="6602740827-26">(</span><span class="ss">normal</span><span class="p" data-group-id="6602740827-26">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="6602740827-27">{</span><span class="ss">message</span><span class="o">=</span><span class="n">What</span><span class="p" data-group-id="6602740827-27">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6602740827-28">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6602740827-29">[</span><span class="n">What</span><span class="p" data-group-id="6602740827-29">]</span><span class="p" data-group-id="6602740827-28">)</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5802107805-30">(</span><span class="s">&quot;No response from server</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5802107805-31">[</span><span class="p" data-group-id="5802107805-31">]</span><span class="p" data-group-id="5802107805-30">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="5802107805-32">(</span><span class="ss">timeout</span><span class="p" data-group-id="5802107805-32">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6602740827-30">(</span><span class="s">&quot;No response from server</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6602740827-31">[</span><span class="p" data-group-id="6602740827-31">]</span><span class="p" data-group-id="6602740827-30">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="6602740827-32">(</span><span class="ss">timeout</span><span class="p" data-group-id="6602740827-32">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%%----END FILE----</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE mess_server.erl----</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% This is the server process of the messenger service</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1907226537-1">(</span><span class="ss">mess_server</span><span class="p" data-group-id="1907226537-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1907226537-2">(</span><span class="p" data-group-id="1907226537-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1907226537-3">]</span><span class="p" data-group-id="1907226537-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="1907226537-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="1907226537-4">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="1907226537-5">(</span><span class="p" data-group-id="1907226537-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="1907226537-6">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="1907226537-6">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">server</span><span class="p" data-group-id="1907226537-7">(</span><span class="p" data-group-id="1907226537-8">[</span><span class="p" data-group-id="1907226537-8">]</span><span class="p" data-group-id="1907226537-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4119789193-1">(</span><span class="ss">mess_server</span><span class="p" data-group-id="4119789193-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4119789193-2">(</span><span class="p" data-group-id="4119789193-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4119789193-3">]</span><span class="p" data-group-id="4119789193-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="4119789193-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="4119789193-4">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="4119789193-5">(</span><span class="p" data-group-id="4119789193-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="4119789193-6">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4119789193-6">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">server</span><span class="p" data-group-id="4119789193-7">(</span><span class="p" data-group-id="4119789193-8">[</span><span class="p" data-group-id="4119789193-8">]</span><span class="p" data-group-id="4119789193-7">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% the user list has the format [{ClientPid1, Name1},{ClientPid2, Name2},...]</span><span class="w">
│ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="1907226537-9">(</span><span class="n">User_List</span><span class="p" data-group-id="1907226537-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1907226537-10">(</span><span class="s">&quot;User list = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1907226537-11">[</span><span class="n">User_List</span><span class="p" data-group-id="1907226537-11">]</span><span class="p" data-group-id="1907226537-10">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="4119789193-9">(</span><span class="n">User_List</span><span class="p" data-group-id="4119789193-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4119789193-10">(</span><span class="s">&quot;User list = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4119789193-11">[</span><span class="n">User_List</span><span class="p" data-group-id="4119789193-11">]</span><span class="p" data-group-id="4119789193-10">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="o">#</span><span class="ss">logon</span><span class="p" data-group-id="1907226537-12">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="o">=</span><span class="n">Name</span><span class="p" data-group-id="1907226537-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="1907226537-13">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1907226537-13">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="1907226537-14">(</span><span class="n">New_User_List</span><span class="p" data-group-id="1907226537-14">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="1907226537-15">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="1907226537-15">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="1907226537-16">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1907226537-16">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="1907226537-17">(</span><span class="n">New_User_List</span><span class="p" data-group-id="1907226537-17">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="o">#</span><span class="ss">message</span><span class="p" data-group-id="1907226537-18">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="1907226537-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="1907226537-19">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1907226537-19">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="1907226537-20">(</span><span class="n">User_List</span><span class="p" data-group-id="1907226537-20">)</span><span class="w">
│ │ │ +        </span><span class="o">#</span><span class="ss">logon</span><span class="p" data-group-id="4119789193-12">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="o">=</span><span class="n">Name</span><span class="p" data-group-id="4119789193-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="4119789193-13">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="4119789193-13">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="4119789193-14">(</span><span class="n">New_User_List</span><span class="p" data-group-id="4119789193-14">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="4119789193-15">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="4119789193-15">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="4119789193-16">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="4119789193-16">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="4119789193-17">(</span><span class="n">New_User_List</span><span class="p" data-group-id="4119789193-17">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="o">#</span><span class="ss">message</span><span class="p" data-group-id="4119789193-18">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="4119789193-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="4119789193-19">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="4119789193-19">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="4119789193-20">(</span><span class="n">User_List</span><span class="p" data-group-id="4119789193-20">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Start the server</span><span class="w">
│ │ │ -</span><span class="nf">start_server</span><span class="p" data-group-id="1907226537-21">(</span><span class="p" data-group-id="1907226537-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="1907226537-22">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="1907226537-23">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1907226537-24">[</span><span class="p" data-group-id="1907226537-24">]</span><span class="p" data-group-id="1907226537-23">)</span><span class="p" data-group-id="1907226537-22">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_server</span><span class="p" data-group-id="4119789193-21">(</span><span class="p" data-group-id="4119789193-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="4119789193-22">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="4119789193-23">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4119789193-24">[</span><span class="p" data-group-id="4119789193-24">]</span><span class="p" data-group-id="4119789193-23">)</span><span class="p" data-group-id="4119789193-22">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Server adds a new user to the user list</span><span class="w">
│ │ │ -</span><span class="nf">server_logon</span><span class="p" data-group-id="1907226537-25">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1907226537-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_logon</span><span class="p" data-group-id="4119789193-25">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="4119789193-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% check if logged on anywhere else</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="1907226537-26">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1907226537-26">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="4119789193-26">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="4119789193-26">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="1907226537-27">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="1907226537-27">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="4119789193-27">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="4119789193-27">}</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">User_List</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="1907226537-28">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">logged_on</span><span class="p" data-group-id="1907226537-28">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">link</span><span class="p" data-group-id="1907226537-29">(</span><span class="n">From</span><span class="p" data-group-id="1907226537-29">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="1907226537-30">[</span><span class="p" data-group-id="1907226537-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1907226537-31">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1907226537-30">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="4119789193-28">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">logged_on</span><span class="p" data-group-id="4119789193-28">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">link</span><span class="p" data-group-id="4119789193-29">(</span><span class="n">From</span><span class="p" data-group-id="4119789193-29">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="4119789193-30">[</span><span class="p" data-group-id="4119789193-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="4119789193-31">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="4119789193-30">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Server deletes a user from the user list</span><span class="w">
│ │ │ -</span><span class="nf">server_logoff</span><span class="p" data-group-id="1907226537-32">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1907226537-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="1907226537-33">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1907226537-33">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">server_logoff</span><span class="p" data-group-id="4119789193-32">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="4119789193-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="4119789193-33">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="4119789193-33">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Server transfers a message between users</span><span class="w">
│ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="1907226537-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1907226537-34">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="4119789193-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="4119789193-34">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% check that the user is logged on and who he is</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="1907226537-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1907226537-35">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="4119789193-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="4119789193-35">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="1907226537-36">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="1907226537-36">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="1907226537-37">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1907226537-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="1907226537-38">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1907226537-38">)</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="4119789193-36">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="4119789193-36">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="4119789193-37">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="4119789193-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="4119789193-38">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="4119789193-38">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%% If the user exists, send the message</span><span class="w">
│ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="1907226537-39">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1907226537-39">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="4119789193-39">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="4119789193-39">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Find the receiver and send the message</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="1907226537-40">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1907226537-40">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="4119789193-40">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="4119789193-40">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="1907226537-41">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">receiver_not_found</span><span class="p" data-group-id="1907226537-41">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="1907226537-42">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="1907226537-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">message_from</span><span class="p" data-group-id="1907226537-43">{</span><span class="ss">from_name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="1907226537-43">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w">  </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="1907226537-44">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">sent</span><span class="p" data-group-id="1907226537-44">}</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="4119789193-41">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">receiver_not_found</span><span class="p" data-group-id="4119789193-41">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="4119789193-42">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="4119789193-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">message_from</span><span class="p" data-group-id="4119789193-43">{</span><span class="ss">from_name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="4119789193-43">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w">  </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="4119789193-44">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">sent</span><span class="p" data-group-id="4119789193-44">}</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%%----END FILE----</span></code></pre><h2 id="header-files" class="section-heading">
│ │ │    <a href="#header-files" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Header Files</span>
│ │ │  </h2>
│ │ │  <p>As shown above, some files have extension <code class="inline">.hrl</code>. These are header files that
│ │ │ -are included in the <code class="inline">.erl</code> files by:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="1598241012-1">(</span><span class="s">&quot;File_Name&quot;</span><span class="p" data-group-id="1598241012-1">)</span><span class="p">.</span></code></pre><p>for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="6833303854-1">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="6833303854-1">)</span><span class="p">.</span></code></pre><p>In the case above the file is fetched from the same directory as all the other
│ │ │ +are included in the <code class="inline">.erl</code> files by:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="9047340446-1">(</span><span class="s">&quot;File_Name&quot;</span><span class="p" data-group-id="9047340446-1">)</span><span class="p">.</span></code></pre><p>for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="2395282044-1">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="2395282044-1">)</span><span class="p">.</span></code></pre><p>In the case above the file is fetched from the same directory as all the other
│ │ │  files in the messenger example. (<em>manual</em>)</p><p>.hrl files can contain any valid Erlang code but are most often used for record
│ │ │  and macro definitions.</p><h2 id="records" class="section-heading">
│ │ │    <a href="#records" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Records</span>
│ │ │  </h2>
│ │ │ -<p>A record is defined as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7800766495-1">(</span><span class="ss">name_of_record</span><span class="p">,</span><span class="p" data-group-id="7800766495-2">{</span><span class="ss">field_name1</span><span class="p">,</span><span class="w"> </span><span class="ss">field_name2</span><span class="p">,</span><span class="w"> </span><span class="ss">field_name3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7800766495-2">}</span><span class="p" data-group-id="7800766495-1">)</span><span class="p">.</span></code></pre><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8402651728-1">(</span><span class="ss">message_to</span><span class="p">,</span><span class="p" data-group-id="8402651728-2">{</span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="8402651728-2">}</span><span class="p" data-group-id="8402651728-1">)</span><span class="p">.</span></code></pre><p>This is equivalent to:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6623038594-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To_Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6623038594-1">}</span></code></pre><p>Creating a record is best illustrated by an example:</p><pre><code class="makeup erlang" translate="no"><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="2849396222-1">{</span><span class="ss">message</span><span class="o">=</span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="ss">fred</span><span class="p" data-group-id="2849396222-1">}</span></code></pre><p>This creates:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4029198522-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="4029198522-1">}</span></code></pre><p>Notice that you do not have to worry about the order in which you assign values to the
│ │ │ +<p>A record is defined as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0229533429-1">(</span><span class="ss">name_of_record</span><span class="p">,</span><span class="p" data-group-id="0229533429-2">{</span><span class="ss">field_name1</span><span class="p">,</span><span class="w"> </span><span class="ss">field_name2</span><span class="p">,</span><span class="w"> </span><span class="ss">field_name3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0229533429-2">}</span><span class="p" data-group-id="0229533429-1">)</span><span class="p">.</span></code></pre><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0316451543-1">(</span><span class="ss">message_to</span><span class="p">,</span><span class="p" data-group-id="0316451543-2">{</span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="0316451543-2">}</span><span class="p" data-group-id="0316451543-1">)</span><span class="p">.</span></code></pre><p>This is equivalent to:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7746857566-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To_Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="7746857566-1">}</span></code></pre><p>Creating a record is best illustrated by an example:</p><pre><code class="makeup erlang" translate="no"><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="1607276703-1">{</span><span class="ss">message</span><span class="o">=</span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="ss">fred</span><span class="p" data-group-id="1607276703-1">}</span></code></pre><p>This creates:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9968415500-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="9968415500-1">}</span></code></pre><p>Notice that you do not have to worry about the order in which you assign values to the
│ │ │  various parts of a record when you create it. The advantage of using records
│ │ │  is that by placing their definitions in header files you can conveniently define
│ │ │  interfaces that are easy to change. For example, if you want to add a new field
│ │ │  to the record, you only have to change the code where the new field is used and
│ │ │  not at every place the record is referred to. If you leave out a field when
│ │ │  creating a record, it gets the value of the atom <code class="inline">undefined</code>. (<em>manual</em>)</p><p>Pattern matching with records is very similar to creating records. For example,
│ │ │ -inside a <code class="inline">case</code> or <code class="inline">receive</code>:</p><pre><code class="makeup erlang" translate="no"><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="2662199482-1">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="2662199482-1">}</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>This is the same as:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3507229041-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3507229041-1">}</span></code></pre><h2 id="macros" class="section-heading">
│ │ │ +inside a <code class="inline">case</code> or <code class="inline">receive</code>:</p><pre><code class="makeup erlang" translate="no"><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="2258639776-1">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="2258639776-1">}</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>This is the same as:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8776030245-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="8776030245-1">}</span></code></pre><h2 id="macros" class="section-heading">
│ │ │    <a href="#macros" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Macros</span>
│ │ │  </h2>
│ │ │  <p>Another thing that has been added to the messenger is a macro. The file
│ │ │  <code class="inline">mess_config.hrl</code> contains the definition:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%%% Configure the location of the server node,</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="1128602636-1">(</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="1128602636-1">)</span><span class="p">.</span></code></pre><p>This file is included in <code class="inline">mess_server.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0581972563-1">(</span><span class="s">&quot;mess_config.hrl&quot;</span><span class="p" data-group-id="0581972563-1">)</span><span class="p">.</span></code></pre><p>Every occurrence of <code class="inline">?server_node</code> in <code class="inline">mess_server.erl</code> is now replaced by
│ │ │ -<code class="inline">messenger@super</code>.</p><p>A macro is also used when spawning the server process:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="7019448960-1">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7019448960-2">[</span><span class="p" data-group-id="7019448960-2">]</span><span class="p" data-group-id="7019448960-1">)</span></code></pre><p>This is a standard macro (that is, defined by the system, not by the user).
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2934131668-1">(</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="2934131668-1">)</span><span class="p">.</span></code></pre><p>This file is included in <code class="inline">mess_server.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="9591617424-1">(</span><span class="s">&quot;mess_config.hrl&quot;</span><span class="p" data-group-id="9591617424-1">)</span><span class="p">.</span></code></pre><p>Every occurrence of <code class="inline">?server_node</code> in <code class="inline">mess_server.erl</code> is now replaced by
│ │ │ +<code class="inline">messenger@super</code>.</p><p>A macro is also used when spawning the server process:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="5357146106-1">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5357146106-2">[</span><span class="p" data-group-id="5357146106-2">]</span><span class="p" data-group-id="5357146106-1">)</span></code></pre><p>This is a standard macro (that is, defined by the system, not by the user).
│ │ │  <code class="inline">?MODULE</code> is always replaced by the name of the current module (that is, the
│ │ │  <code class="inline">-module</code> definition near the start of the file). There are more advanced ways
│ │ │  of using macros with, for example, <a href="macros.html#defining-and-using-macros">parameters</a>.</p><p>The three Erlang (<code class="inline">.erl</code>) files in the messenger example are individually
│ │ │  compiled into object code files (<code class="inline">.beam</code>). The Erlang system loads and links
│ │ │  these files into the system when they are referred to during execution of the
│ │ │  code. In this case, they are simply put in our current working directory (that
│ │ │  is, the place you have done &quot;cd&quot; to). There are ways of putting the <code class="inline">.beam</code>
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/ref_man_functions.html
│ │ │ @@ -120,51 +120,51 @@
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Function Declaration Syntax</span>
│ │ │  </h2>
│ │ │  <p>A <em>function declaration</em> is a sequence of function clauses separated by
│ │ │  semicolons, and terminated by a period (<code class="inline">.</code>).</p><p>A <em>function clause</em> consists of a <em>clause head</em> and a <em>clause body</em>, separated by
│ │ │  <code class="inline">-&gt;</code>.</p><p>A clause <em>head</em> consists of the function name, an argument list, and an optional
│ │ │ -guard sequence beginning with the keyword <code class="inline">when</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="p" data-group-id="0187520873-1">(</span><span class="n">Pattern11</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">Pattern1N</span><span class="p" data-group-id="0187520873-1">)</span><span class="w"> </span><span class="p" data-group-id="0187520873-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="0187520873-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +guard sequence beginning with the keyword <code class="inline">when</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="p" data-group-id="0492094079-1">(</span><span class="n">Pattern11</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">Pattern1N</span><span class="p" data-group-id="0492094079-1">)</span><span class="w"> </span><span class="p" data-group-id="0492094079-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="0492094079-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="n">Name</span><span class="p" data-group-id="0187520873-3">(</span><span class="n">PatternK1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">PatternKN</span><span class="p" data-group-id="0187520873-3">)</span><span class="w"> </span><span class="p" data-group-id="0187520873-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqK</span><span class="p" data-group-id="0187520873-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="n">Name</span><span class="p" data-group-id="0492094079-3">(</span><span class="n">PatternK1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">PatternKN</span><span class="p" data-group-id="0492094079-3">)</span><span class="w"> </span><span class="p" data-group-id="0492094079-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqK</span><span class="p" data-group-id="0492094079-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">BodyK</span><span class="p">.</span></code></pre><p>The function name is an atom. Each argument is a pattern.</p><p>The number of arguments <code class="inline">N</code> is the <em>arity</em> of the function. A function is
│ │ │  uniquely defined by the module name, function name, and arity. That is, two
│ │ │  functions with the same name and in the same module, but with different arities
│ │ │  are two different functions.</p><p>A function named <code class="inline">f</code> in module <code class="inline">mod</code> and with arity <code class="inline">N</code> is often denoted as
│ │ │  <code class="inline">mod:f/N</code>.</p><p>A clause <em>body</em> consists of a sequence of expressions separated by comma (<code class="inline">,</code>):</p><pre><code class="text">Expr1,
│ │ │  ...,
│ │ │  ExprN</code></pre><p>Valid Erlang expressions and guard sequences are described in
│ │ │ -<a href="expressions.html">Expressions</a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">fact</span><span class="p" data-group-id="0865067699-1">(</span><span class="n">N</span><span class="p" data-group-id="0865067699-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% first clause head</span><span class="w">
│ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="0865067699-2">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="0865067699-2">)</span><span class="p">;</span><span class="w">     </span><span class="c1">% first clause body</span><span class="w">
│ │ │ +<a href="expressions.html">Expressions</a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">fact</span><span class="p" data-group-id="9033593789-1">(</span><span class="n">N</span><span class="p" data-group-id="9033593789-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% first clause head</span><span class="w">
│ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="9033593789-2">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="9033593789-2">)</span><span class="p">;</span><span class="w">     </span><span class="c1">% first clause body</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="0865067699-3">(</span><span class="mi">0</span><span class="p" data-group-id="0865067699-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">             </span><span class="c1">% second clause head</span><span class="w">
│ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="9033593789-3">(</span><span class="mi">0</span><span class="p" data-group-id="9033593789-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">             </span><span class="c1">% second clause head</span><span class="w">
│ │ │      </span><span class="mi">1</span><span class="p">.</span><span class="w">                 </span><span class="c1">% second clause body</span></code></pre><p><a href="" id="eval"></a></p><h2 id="function-evaluation" class="section-heading">
│ │ │    <a href="#function-evaluation" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Function Evaluation</span>
│ │ │  </h2>
│ │ │  <p>When a function <code class="inline">M:F/N</code> is called, first the code for the function is located.
│ │ │  If the function cannot be found, an <code class="inline">undef</code> runtime error occurs. Notice that
│ │ │  the function must be exported to be visible outside the module it is defined in.</p><p>If the function is found, the function clauses are scanned sequentially until a
│ │ │  clause is found that fulfills both of the following two conditions:</p><ol><li>The patterns in the clause head can be successfully matched against the given
│ │ │  arguments.</li><li>The guard sequence, if any, is true.</li></ol><p>If such a clause cannot be found, a <code class="inline">function_clause</code> runtime error occurs.</p><p>If such a clause is found, the corresponding clause body is evaluated. That is,
│ │ │  the expressions in the body are evaluated sequentially and the value of the last
│ │ │ -expression is returned.</p><p>Consider the function <code class="inline">fact</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2701611458-1">(</span><span class="ss">mod</span><span class="p" data-group-id="2701611458-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2701611458-2">(</span><span class="p" data-group-id="2701611458-3">[</span><span class="ss">fact</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2701611458-3">]</span><span class="p" data-group-id="2701611458-2">)</span><span class="p">.</span><span class="w">
│ │ │ +expression is returned.</p><p>Consider the function <code class="inline">fact</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5052150461-1">(</span><span class="ss">mod</span><span class="p" data-group-id="5052150461-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5052150461-2">(</span><span class="p" data-group-id="5052150461-3">[</span><span class="ss">fact</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5052150461-3">]</span><span class="p" data-group-id="5052150461-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="2701611458-4">(</span><span class="n">N</span><span class="p" data-group-id="2701611458-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="2701611458-5">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2701611458-5">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="2701611458-6">(</span><span class="mi">0</span><span class="p" data-group-id="2701611458-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="5052150461-4">(</span><span class="n">N</span><span class="p" data-group-id="5052150461-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="5052150461-5">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="5052150461-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="5052150461-6">(</span><span class="mi">0</span><span class="p" data-group-id="5052150461-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="mi">1</span><span class="p">.</span></code></pre><p>Assume that you want to calculate the factorial for 1:</p><pre><code class="text">1&gt; mod:fact(1).</code></pre><p>Evaluation starts at the first clause. The pattern <code class="inline">N</code> is matched against
│ │ │  argument 1. The matching succeeds and the guard (<code class="inline">N &gt; 0</code>) is true, thus <code class="inline">N</code> is
│ │ │ -bound to 1, and the corresponding body is evaluated:</p><pre><code class="makeup erlang" translate="no"><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="3815093146-1">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="3815093146-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3815093146-2">(</span><span class="n">N</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">bound</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="3815093146-2">)</span><span class="w">
│ │ │ -</span><span class="mi">1</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="3815093146-3">(</span><span class="mi">0</span><span class="p" data-group-id="3815093146-3">)</span></code></pre><p>Now, <code class="inline">fact(0)</code> is called, and the function clauses are scanned
│ │ │ +bound to 1, and the corresponding body is evaluated:</p><pre><code class="makeup erlang" translate="no"><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="5523210306-1">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="5523210306-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5523210306-2">(</span><span class="n">N</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">bound</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="5523210306-2">)</span><span class="w">
│ │ │ +</span><span class="mi">1</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="5523210306-3">(</span><span class="mi">0</span><span class="p" data-group-id="5523210306-3">)</span></code></pre><p>Now, <code class="inline">fact(0)</code> is called, and the function clauses are scanned
│ │ │  sequentially again. First, the pattern <code class="inline">N</code> is matched against 0. The
│ │ │  matching succeeds, but the guard (<code class="inline">N &gt; 0</code>) is false. Second, the
│ │ │  pattern <code class="inline">0</code> is matched against the argument <code class="inline">0</code>. The matching succeeds
│ │ │  and the body is evaluated:</p><pre><code class="text">1 * fact(0) =&gt;
│ │ │  1 * 1 =&gt;
│ │ │  1</code></pre><p>Evaluation has succeeded and <code class="inline">mod:fact(1)</code> returns 1.</p><p>If <code class="inline">mod:fact/1</code> is called with a negative number as argument, no clause head
│ │ │  matches. A <code class="inline">function_clause</code> runtime error occurs.</p><h2 id="tail-recursion" class="section-heading">
│ │ │ @@ -173,17 +173,17 @@
│ │ │    </a>
│ │ │    <span class="text">Tail recursion</span>
│ │ │  </h2>
│ │ │  <p>If the last expression of a function body is a function call, a
│ │ │  <em>tail-recursive call</em> is done. This is to ensure that no system
│ │ │  resources, for example, call stack, are consumed. This means that an
│ │ │  infinite loop using tail-recursive calls will not exhaust the call
│ │ │ -stack and can (in principle) run forever.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="3599951357-1">(</span><span class="n">N</span><span class="p" data-group-id="3599951357-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3599951357-2">(</span><span class="s">&quot;</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3599951357-3">[</span><span class="n">N</span><span class="p" data-group-id="3599951357-3">]</span><span class="p" data-group-id="3599951357-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="3599951357-4">(</span><span class="n">N</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="3599951357-4">)</span><span class="p">.</span></code></pre><p>The earlier factorial example is a counter-example. It is not
│ │ │ +stack and can (in principle) run forever.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="9299584141-1">(</span><span class="n">N</span><span class="p" data-group-id="9299584141-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9299584141-2">(</span><span class="s">&quot;</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9299584141-3">[</span><span class="n">N</span><span class="p" data-group-id="9299584141-3">]</span><span class="p" data-group-id="9299584141-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="9299584141-4">(</span><span class="n">N</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="9299584141-4">)</span><span class="p">.</span></code></pre><p>The earlier factorial example is a counter-example. It is not
│ │ │  tail-recursive, since a multiplication is done on the result of the recursive
│ │ │  call to <code class="inline">fact(N-1)</code>.</p><h2 id="built-in-functions-bifs" class="section-heading">
│ │ │    <a href="#built-in-functions-bifs" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Built-In Functions (BIFs)</span>
│ │ │  </h2>
│ │ │ @@ -191,17 +191,17 @@
│ │ │  system. BIFs do things that are difficult or impossible to implement
│ │ │  in Erlang. Most of the BIFs belong to module <a href="../../erts-17.0/doc/html/erlang.html"><code class="inline">erlang</code></a>, but there
│ │ │  are also BIFs belonging to a few other modules, for example <a href="../../lib/stdlib-8.0/doc/html/lists.html"><code class="inline">lists</code></a>
│ │ │  and <a href="../../lib/stdlib-8.0/doc/html/ets.html"><code class="inline">ets</code></a>.</p><p>The most commonly used BIFs belonging to <a href="../../erts-17.0/doc/html/erlang.html"><code class="inline">erlang</code></a> are <em>auto-imported</em>. They do
│ │ │  not need to be prefixed with the module name. Which BIFs are auto-imported
│ │ │  is specified in the <a href="../../erts-17.0/doc/html/erlang.html"><code class="inline">erlang</code></a> module in ERTS. For example, standard-type
│ │ │  conversion BIFs like <code class="inline">atom_to_list</code> and BIFs allowed in guards can be called
│ │ │ -without specifying the module name.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="8089516400-1">(</span><span class="p" data-group-id="8089516400-2">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="8089516400-2">}</span><span class="p" data-group-id="8089516400-1">)</span><span class="p">.</span><span class="w">
│ │ │ +without specifying the module name.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="9955631679-1">(</span><span class="p" data-group-id="9955631679-2">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="9955631679-2">}</span><span class="p" data-group-id="9955631679-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="8089516400-3">(</span><span class="ss">&#39;Erlang&#39;</span><span class="p" data-group-id="8089516400-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="9955631679-3">(</span><span class="ss">&#39;Erlang&#39;</span><span class="p" data-group-id="9955631679-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;Erlang&quot;</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="documentation.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/ref_man_processes.html
│ │ │ @@ -125,18 +125,18 @@
│ │ │  (grow and shrink dynamically) with a small memory footprint, fast to create and
│ │ │  terminate, and the scheduling overhead is low.</p><h2 id="process-creation" class="section-heading">
│ │ │    <a href="#process-creation" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Process Creation</span>
│ │ │  </h2>
│ │ │ -<p>A process is created by calling <a href="../../erts-17.0/doc/html/erlang.html#spawn/3"><code class="inline">spawn()</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="3375164988-1">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="3375164988-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pid</span><span class="p" data-group-id="3375164988-2">(</span><span class="p" data-group-id="3375164988-2">)</span><span class="w">
│ │ │ -  </span><span class="n">Module</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="3375164988-3">(</span><span class="p" data-group-id="3375164988-3">)</span><span class="w">
│ │ │ -  </span><span class="n">Args</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3375164988-4">[</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="3375164988-4">]</span><span class="w">
│ │ │ -    </span><span class="n">ArgI</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="3375164988-5">(</span><span class="p" data-group-id="3375164988-5">)</span></code></pre><p><code class="inline">spawn()</code> creates a new process and returns the pid.</p><p>The new process starts executing in <code class="inline">Module:Name(Arg1,...,ArgN)</code> where the
│ │ │ +<p>A process is created by calling <a href="../../erts-17.0/doc/html/erlang.html#spawn/3"><code class="inline">spawn()</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="4459058492-1">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="4459058492-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pid</span><span class="p" data-group-id="4459058492-2">(</span><span class="p" data-group-id="4459058492-2">)</span><span class="w">
│ │ │ +  </span><span class="n">Module</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="4459058492-3">(</span><span class="p" data-group-id="4459058492-3">)</span><span class="w">
│ │ │ +  </span><span class="n">Args</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4459058492-4">[</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="4459058492-4">]</span><span class="w">
│ │ │ +    </span><span class="n">ArgI</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="4459058492-5">(</span><span class="p" data-group-id="4459058492-5">)</span></code></pre><p><code class="inline">spawn()</code> creates a new process and returns the pid.</p><p>The new process starts executing in <code class="inline">Module:Name(Arg1,...,ArgN)</code> where the
│ │ │  arguments are the elements of the (possibly empty) <code class="inline">Args</code> argument list.</p><p>There exist a number of different <code class="inline">spawn</code> BIFs:</p><ul><li><a href="../../erts-17.0/doc/html/erlang.html#spawn/4"><code class="inline">spawn/1,2,3,4</code></a></li><li><a href="../../erts-17.0/doc/html/erlang.html#spawn_link/4"><code class="inline">spawn_link/1,2,3,4</code></a></li><li><a href="../../erts-17.0/doc/html/erlang.html#spawn_monitor/4"><code class="inline">spawn_monitor/1,2,3,4</code></a></li><li><a href="../../erts-17.0/doc/html/erlang.html#spawn_opt/5"><code class="inline">spawn_opt/2,3,4,5</code></a></li><li><a href="../../erts-17.0/doc/html/erlang.html#spawn_request/5"><code class="inline">spawn_request/1,2,3,4,5</code></a></li></ul><h2 id="registered-processes" class="section-heading">
│ │ │    <a href="#registered-processes" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Registered Processes</span>
│ │ │  </h2>
│ │ │  <p>Besides addressing a process by using its pid, there are also BIFs for
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/ref_man_records.html
│ │ │ @@ -123,17 +123,17 @@
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Defining Records</span>
│ │ │  </h2>
│ │ │  <p>A record definition consists of the name of the record, followed by the field
│ │ │  names of the record. Record and field names must be atoms. Each field can be
│ │ │  given an optional default value. If no default value is supplied, <code class="inline">undefined</code> is
│ │ │ -used.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4991670831-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4991670831-2">{</span><span class="n">Field1</span><span class="w"> </span><span class="p" data-group-id="4991670831-3">[</span><span class="o">=</span><span class="w"> </span><span class="n">Expr1</span><span class="p" data-group-id="4991670831-3">]</span><span class="p">,</span><span class="w">
│ │ │ +used.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8145492919-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8145492919-2">{</span><span class="n">Field1</span><span class="w"> </span><span class="p" data-group-id="8145492919-3">[</span><span class="o">=</span><span class="w"> </span><span class="n">Expr1</span><span class="p" data-group-id="8145492919-3">]</span><span class="p">,</span><span class="w">
│ │ │                 </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -               </span><span class="n">FieldN</span><span class="w"> </span><span class="p" data-group-id="4991670831-4">[</span><span class="o">=</span><span class="w"> </span><span class="n">ExprN</span><span class="p" data-group-id="4991670831-4">]</span><span class="p" data-group-id="4991670831-2">}</span><span class="p" data-group-id="4991670831-1">)</span><span class="p">.</span></code></pre><p>The default value for a field is an arbitrary expression, except that it must
│ │ │ +               </span><span class="n">FieldN</span><span class="w"> </span><span class="p" data-group-id="8145492919-4">[</span><span class="o">=</span><span class="w"> </span><span class="n">ExprN</span><span class="p" data-group-id="8145492919-4">]</span><span class="p" data-group-id="8145492919-2">}</span><span class="p" data-group-id="8145492919-1">)</span><span class="p">.</span></code></pre><p>The default value for a field is an arbitrary expression, except that it must
│ │ │  not use any variables.</p><p>A record definition can be placed anywhere among the attributes and function
│ │ │  declarations of a module, but the definition must come before any usage of the
│ │ │  record.</p><p>If a record is used in several modules, it is recommended that the record
│ │ │  definition is placed in an include file.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Starting from Erlang/OTP 26, records can be defined in the Erlang shell
│ │ │  using the syntax described in this section. In earlier releases, it was
│ │ │  necessary to use the <a href="../../lib/stdlib-8.0/doc/html/shell.html"><code class="inline">shell</code></a> built-in function <code class="inline">rd/2</code>.</p></section><h2 id="creating-records" class="section-heading">
│ │ │    <a href="#creating-records" class="hover-link">
│ │ │ @@ -143,32 +143,32 @@
│ │ │  </h2>
│ │ │  <p>The following expression creates a new <code class="inline">Name</code> record where the value of each
│ │ │  field <code class="inline">FieldI</code> is the value of evaluating the corresponding expression <code class="inline">ExprI</code>:</p><pre><code class="text">#Name{Field1=Expr1, ..., FieldK=ExprK}</code></pre><p>The fields can be in any order, not necessarily the same order as in the record
│ │ │  definition, and fields can be omitted. Omitted fields get their respective
│ │ │  default value instead.</p><p>If several fields are to be assigned the same value, the following construction
│ │ │  can be used:</p><pre><code class="text">#Name{Field1=Expr1, ..., FieldK=ExprK, _=ExprL}</code></pre><p>Omitted fields then get the value of evaluating <code class="inline">ExprL</code> instead of their default
│ │ │  values. This feature is primarily intended to be used to create patterns for ETS
│ │ │ -and Mnesia match functions.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2454578451-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2454578451-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="2454578451-2">}</span><span class="p" data-group-id="2454578451-1">)</span><span class="p">.</span><span class="w">
│ │ │ +and Mnesia match functions.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0301930038-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0301930038-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="0301930038-2">}</span><span class="p" data-group-id="0301930038-1">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">lookup</span><span class="p" data-group-id="2454578451-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Tab</span><span class="p" data-group-id="2454578451-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match_object</span><span class="p" data-group-id="2454578451-4">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2454578451-5">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="2454578451-5">}</span><span class="p" data-group-id="2454578451-4">)</span><span class="p">.</span></code></pre><h2 id="accessing-record-fields" class="section-heading">
│ │ │ +</span><span class="nf">lookup</span><span class="p" data-group-id="0301930038-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Tab</span><span class="p" data-group-id="0301930038-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match_object</span><span class="p" data-group-id="0301930038-4">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="0301930038-5">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="0301930038-5">}</span><span class="p" data-group-id="0301930038-4">)</span><span class="p">.</span></code></pre><h2 id="accessing-record-fields" class="section-heading">
│ │ │    <a href="#accessing-record-fields" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Accessing Record Fields</span>
│ │ │  </h2>
│ │ │  <pre><code class="text">Expr#Name.Field</code></pre><p>Returns the value of the specified field. <code class="inline">Expr</code> is to evaluate to a <code class="inline">Name</code>
│ │ │ -record.</p><p><em>Example</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2590661407-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2590661407-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="2590661407-2">}</span><span class="p" data-group-id="2590661407-1">)</span><span class="p">.</span><span class="w">
│ │ │ +record.</p><p><em>Example</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1010336670-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1010336670-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="1010336670-2">}</span><span class="p" data-group-id="1010336670-1">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">get_person_name</span><span class="p" data-group-id="2590661407-3">(</span><span class="n">Person</span><span class="p" data-group-id="2590661407-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">get_person_name</span><span class="p" data-group-id="1010336670-3">(</span><span class="n">Person</span><span class="p" data-group-id="1010336670-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">.</span></code></pre><p>The following expression returns the position of the specified field in the
│ │ │ -tuple representation of the record:</p><pre><code class="text">#Name.Field</code></pre><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7266020184-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7266020184-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="7266020184-2">}</span><span class="p" data-group-id="7266020184-1">)</span><span class="p">.</span><span class="w">
│ │ │ +tuple representation of the record:</p><pre><code class="text">#Name.Field</code></pre><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7477037635-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7477037635-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="7477037635-2">}</span><span class="p" data-group-id="7477037635-1">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">lookup</span><span class="p" data-group-id="7266020184-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7266020184-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="7266020184-4">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7266020184-4">)</span><span class="p">.</span></code></pre><h2 id="updating-records" class="section-heading">
│ │ │ +</span><span class="nf">lookup</span><span class="p" data-group-id="7477037635-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7477037635-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="7477037635-4">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7477037635-4">)</span><span class="p">.</span></code></pre><h2 id="updating-records" class="section-heading">
│ │ │    <a href="#updating-records" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Updating Records</span>
│ │ │  </h2>
│ │ │  <pre><code class="text">Expr#Name{Field1=Expr1, ..., FieldK=ExprK}</code></pre><p><code class="inline">Expr</code> is to evaluate to a <code class="inline">Name</code> record. A copy of this record is returned,
│ │ │  with the value of each specified field <code class="inline">FieldI</code> changed to the value of
│ │ │ @@ -178,51 +178,51 @@
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Records in Guards</span>
│ │ │  </h2>
│ │ │  <p>Since record expressions are expanded to tuple expressions, creating
│ │ │  records and accessing record fields are allowed in guards. However,
│ │ │  all subexpressions (for initializing fields) must be valid guard
│ │ │ -expressions as well.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle</span><span class="p" data-group-id="5580446870-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5580446870-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Msg</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="o">#</span><span class="ss">msg</span><span class="p" data-group-id="5580446870-2">{</span><span class="ss">to</span><span class="o">=</span><span class="ss">void</span><span class="p">,</span><span class="w"> </span><span class="ss">no</span><span class="o">=</span><span class="mi">3</span><span class="p" data-group-id="5580446870-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +expressions as well.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle</span><span class="p" data-group-id="8633291064-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8633291064-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Msg</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="o">#</span><span class="ss">msg</span><span class="p" data-group-id="8633291064-2">{</span><span class="ss">to</span><span class="o">=</span><span class="ss">void</span><span class="p">,</span><span class="w"> </span><span class="ss">no</span><span class="o">=</span><span class="mi">3</span><span class="p" data-group-id="8633291064-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle</span><span class="p" data-group-id="5580446870-3">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5580446870-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">running</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>There is also a type test BIF <a href="../../erts-17.0/doc/html/erlang.html#is_record/2"><code class="inline">is_record(Term, RecordTag)</code></a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_person</span><span class="p" data-group-id="8083277526-1">(</span><span class="n">P</span><span class="p" data-group-id="8083277526-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="8083277526-2">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="8083277526-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle</span><span class="p" data-group-id="8633291064-3">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8633291064-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">running</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>There is also a type test BIF <a href="../../erts-17.0/doc/html/erlang.html#is_record/2"><code class="inline">is_record(Term, RecordTag)</code></a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_person</span><span class="p" data-group-id="8809320150-1">(</span><span class="n">P</span><span class="p" data-group-id="8809320150-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="8809320150-2">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="8809320150-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">is_person</span><span class="p" data-group-id="8083277526-3">(</span><span class="p">_</span><span class="n">P</span><span class="p" data-group-id="8083277526-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">is_person</span><span class="p" data-group-id="8809320150-3">(</span><span class="p">_</span><span class="n">P</span><span class="p" data-group-id="8809320150-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">false</span><span class="p">.</span></code></pre><h2 id="records-in-patterns" class="section-heading">
│ │ │    <a href="#records-in-patterns" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Records in Patterns</span>
│ │ │  </h2>
│ │ │  <p>A pattern that matches a certain record is created in the same way as a record
│ │ │  is created:</p><pre><code class="text">#Name{Field1=Expr1, ..., FieldK=ExprK}</code></pre><p>In this case, one or more of <code class="inline">Expr1</code> ... <code class="inline">ExprK</code> can be unbound variables.</p><h2 id="nested-records" class="section-heading">
│ │ │    <a href="#nested-records" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Nested Records</span>
│ │ │  </h2>
│ │ │ -<p>Assume the following record definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2150345390-1">(</span><span class="ss">nrec0</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2150345390-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested0&quot;</span><span class="p" data-group-id="2150345390-2">}</span><span class="p" data-group-id="2150345390-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2150345390-3">(</span><span class="ss">nrec1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2150345390-4">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested1&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">nrec0</span><span class="o">=</span><span class="o">#</span><span class="ss">nrec0</span><span class="p" data-group-id="2150345390-5">{</span><span class="p" data-group-id="2150345390-5">}</span><span class="p" data-group-id="2150345390-4">}</span><span class="p" data-group-id="2150345390-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2150345390-6">(</span><span class="ss">nrec2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2150345390-7">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested2&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">nrec1</span><span class="o">=</span><span class="o">#</span><span class="ss">nrec1</span><span class="p" data-group-id="2150345390-8">{</span><span class="p" data-group-id="2150345390-8">}</span><span class="p" data-group-id="2150345390-7">}</span><span class="p" data-group-id="2150345390-6">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Assume the following record definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5993821380-1">(</span><span class="ss">nrec0</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5993821380-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested0&quot;</span><span class="p" data-group-id="5993821380-2">}</span><span class="p" data-group-id="5993821380-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5993821380-3">(</span><span class="ss">nrec1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5993821380-4">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested1&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">nrec0</span><span class="o">=</span><span class="o">#</span><span class="ss">nrec0</span><span class="p" data-group-id="5993821380-5">{</span><span class="p" data-group-id="5993821380-5">}</span><span class="p" data-group-id="5993821380-4">}</span><span class="p" data-group-id="5993821380-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5993821380-6">(</span><span class="ss">nrec2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5993821380-7">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested2&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">nrec1</span><span class="o">=</span><span class="o">#</span><span class="ss">nrec1</span><span class="p" data-group-id="5993821380-8">{</span><span class="p" data-group-id="5993821380-8">}</span><span class="p" data-group-id="5993821380-7">}</span><span class="p" data-group-id="5993821380-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">N2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">nrec2</span><span class="p" data-group-id="2150345390-9">{</span><span class="p" data-group-id="2150345390-9">}</span><span class="p">,</span></code></pre><p>Accessing or updating nested records can be written without parentheses:</p><pre><code class="text">&quot;nested0&quot; = N2#nrec2.nrec1#nrec1.nrec0#nrec0.name,
│ │ │ +</span><span class="n">N2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">nrec2</span><span class="p" data-group-id="5993821380-9">{</span><span class="p" data-group-id="5993821380-9">}</span><span class="p">,</span></code></pre><p>Accessing or updating nested records can be written without parentheses:</p><pre><code class="text">&quot;nested0&quot; = N2#nrec2.nrec1#nrec1.nrec0#nrec0.name,
│ │ │      N0n = N2#nrec2.nrec1#nrec1.nrec0#nrec0{name = &quot;nested0a&quot;},</code></pre><p>which is equivalent to:</p><pre><code class="text">&quot;nested0&quot; = ((N2#nrec2.nrec1)#nrec1.nrec0)#nrec0.name,
│ │ │  N0n = ((N2#nrec2.nrec1)#nrec1.nrec0)#nrec0{name = &quot;nested0a&quot;},</code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP R14, parentheses were necessary when accessing or updating
│ │ │  nested records.</p></section><h2 id="internal-representation-of-records" class="section-heading">
│ │ │    <a href="#internal-representation-of-records" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Internal Representation of Records</span>
│ │ │  </h2>
│ │ │  <p>Record expressions are translated to tuple expressions during compilation. A
│ │ │ -record defined as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8547407562-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8547407562-2">{</span><span class="n">Field1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">FieldN</span><span class="p" data-group-id="8547407562-2">}</span><span class="p" data-group-id="8547407562-1">)</span><span class="p">.</span></code></pre><p>is internally represented by the tuple:</p><pre><code class="text">{Name, Value1, ..., ValueN}</code></pre><p>Here each <code class="inline">ValueI</code> is the default value for <code class="inline">FieldI</code>.</p><p>To each module using records, a pseudo function is added during compilation to
│ │ │ -obtain information about records:</p><pre><code class="makeup erlang" translate="no"><span class="nf">record_info</span><span class="p" data-group-id="5076168943-1">(</span><span class="ss">fields</span><span class="p">,</span><span class="w"> </span><span class="n">Record</span><span class="p" data-group-id="5076168943-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5076168943-2">[</span><span class="n">Field</span><span class="p" data-group-id="5076168943-2">]</span><span class="w">
│ │ │ -</span><span class="nf">record_info</span><span class="p" data-group-id="5076168943-3">(</span><span class="nb">size</span><span class="p">,</span><span class="w"> </span><span class="n">Record</span><span class="p" data-group-id="5076168943-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Size</span></code></pre><p><code class="inline">Size</code> is the size of the tuple representation, that is, one more than the
│ │ │ +record defined as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="3448916996-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3448916996-2">{</span><span class="n">Field1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">FieldN</span><span class="p" data-group-id="3448916996-2">}</span><span class="p" data-group-id="3448916996-1">)</span><span class="p">.</span></code></pre><p>is internally represented by the tuple:</p><pre><code class="text">{Name, Value1, ..., ValueN}</code></pre><p>Here each <code class="inline">ValueI</code> is the default value for <code class="inline">FieldI</code>.</p><p>To each module using records, a pseudo function is added during compilation to
│ │ │ +obtain information about records:</p><pre><code class="makeup erlang" translate="no"><span class="nf">record_info</span><span class="p" data-group-id="5978617454-1">(</span><span class="ss">fields</span><span class="p">,</span><span class="w"> </span><span class="n">Record</span><span class="p" data-group-id="5978617454-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5978617454-2">[</span><span class="n">Field</span><span class="p" data-group-id="5978617454-2">]</span><span class="w">
│ │ │ +</span><span class="nf">record_info</span><span class="p" data-group-id="5978617454-3">(</span><span class="nb">size</span><span class="p">,</span><span class="w"> </span><span class="n">Record</span><span class="p" data-group-id="5978617454-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Size</span></code></pre><p><code class="inline">Size</code> is the size of the tuple representation, that is, one more than the
│ │ │  number of fields.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="macros.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/release_handling.html
│ │ │ @@ -223,38 +223,38 @@
│ │ │    <span class="text">update</span>
│ │ │  </h3>
│ │ │  <p>If a more complex change has been made, for example, a change to the format of
│ │ │  the internal state of a <a href="../../lib/stdlib-8.0/doc/html/gen_server.html"><code class="inline">gen_server</code></a>, simple code replacement is not sufficient.
│ │ │  Instead, it is necessary to:</p><ul><li>Suspend the processes using the module (to avoid that they try to handle any
│ │ │  requests before the code replacement is completed).</li><li>Ask them to transform the internal state format and switch to the new version
│ │ │  of the module.</li><li>Remove the old version.</li><li>Resume the processes.</li></ul><p>This is called <em>synchronized code replacement</em> and for this the following
│ │ │ -instructions are used:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5082476094-1">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5082476094-2">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="5082476094-2">}</span><span class="p" data-group-id="5082476094-1">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5082476094-3">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="5082476094-3">}</span></code></pre><p><code class="inline">update</code> with argument <code class="inline">{advanced,Extra}</code> is used when changing the internal
│ │ │ +instructions are used:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5701462890-1">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5701462890-2">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="5701462890-2">}</span><span class="p" data-group-id="5701462890-1">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5701462890-3">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="5701462890-3">}</span></code></pre><p><code class="inline">update</code> with argument <code class="inline">{advanced,Extra}</code> is used when changing the internal
│ │ │  state of a behaviour as described above. It causes behaviour processes to call
│ │ │  the callback function <code class="inline">code_change/3</code>, passing the term <code class="inline">Extra</code> and some other
│ │ │  information as arguments. See the manual pages for the respective behaviours and
│ │ │  <a href="appup_cookbook.html#int_state">Appup Cookbook</a>.</p><p><code class="inline">update</code> with argument <code class="inline">supervisor</code> is used when changing the start
│ │ │  specification of a supervisor. See <a href="appup_cookbook.html#sup">Appup Cookbook</a>.</p><p>When a module is to be updated, the release handler finds which processes that
│ │ │  are <em>using</em> the module by traversing the supervision tree of each running
│ │ │ -application and checking all the child specifications:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7817119223-1">{</span><span class="n">Id</span><span class="p">,</span><span class="w"> </span><span class="n">StartFunc</span><span class="p">,</span><span class="w"> </span><span class="n">Restart</span><span class="p">,</span><span class="w"> </span><span class="n">Shutdown</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">Modules</span><span class="p" data-group-id="7817119223-1">}</span></code></pre><p>A process uses a module if the name is listed in <code class="inline">Modules</code> in the child
│ │ │ +application and checking all the child specifications:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8699461443-1">{</span><span class="n">Id</span><span class="p">,</span><span class="w"> </span><span class="n">StartFunc</span><span class="p">,</span><span class="w"> </span><span class="n">Restart</span><span class="p">,</span><span class="w"> </span><span class="n">Shutdown</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">Modules</span><span class="p" data-group-id="8699461443-1">}</span></code></pre><p>A process uses a module if the name is listed in <code class="inline">Modules</code> in the child
│ │ │  specification for the process.</p><p>If <code class="inline">Modules=dynamic</code>, which is the case for event managers, the event manager
│ │ │  process informs the release handler about the list of currently installed event
│ │ │  handlers (<code class="inline">gen_event</code>), and it is checked if the module name is in this list
│ │ │  instead.</p><p>The release handler suspends, asks for code change, and resumes processes by
│ │ │  calling the functions <code class="inline">sys:suspend/1,2</code>, <code class="inline">sys:change_code/4,5</code>, and
│ │ │  <code class="inline">sys:resume/1,2</code>, respectively.</p><h3 id="add_module-and-delete_module" class="section-heading">
│ │ │    <a href="#add_module-and-delete_module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">add_module and delete_module</span>
│ │ │  </h3>
│ │ │ -<p>If a new module is introduced, the following instruction is used:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2806156239-1">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="2806156239-1">}</span></code></pre><p>This instruction loads module <code class="inline">Module</code>. When running Erlang in
│ │ │ +<p>If a new module is introduced, the following instruction is used:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3263010682-1">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="3263010682-1">}</span></code></pre><p>This instruction loads module <code class="inline">Module</code>. When running Erlang in
│ │ │  embedded mode it is necessary to use this instruction. It is not
│ │ │  strictly required when running Erlang in interactive mode, since the
│ │ │ -code server automatically searches for and loads unloaded modules.</p><p>The opposite of <code class="inline">add_module</code> is <code class="inline">delete_module</code>, which unloads a module:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7337327996-1">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="7337327996-1">}</span></code></pre><p>Any process, in any application, with <code class="inline">Module</code> as residence module, is
│ │ │ +code server automatically searches for and loads unloaded modules.</p><p>The opposite of <code class="inline">add_module</code> is <code class="inline">delete_module</code>, which unloads a module:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2196181938-1">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="2196181938-1">}</span></code></pre><p>Any process, in any application, with <code class="inline">Module</code> as residence module, is
│ │ │  killed when the instruction is evaluated. Therefore, the user must
│ │ │  ensure that all such processes are terminated before deleting module
│ │ │  <code class="inline">Module</code> to avoid a situation with failing supervisor restarts.</p><h3 id="application-instructions" class="section-heading">
│ │ │    <a href="#application-instructions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Application Instructions</span>
│ │ │ @@ -341,60 +341,60 @@
│ │ │  <code class="inline">.app</code> file.</li><li>Each <code class="inline">UpFromVsn</code> is a previous version of the application to upgrade from.</li><li>Each <code class="inline">DownToVsn</code> is a previous version of the application to downgrade to.</li><li>Each <code class="inline">Instructions</code> is a list of release handling instructions.</li></ul><p><code class="inline">UpFromVsn</code> and <code class="inline">DownToVsn</code> can also be specified as regular expressions. For
│ │ │  more information about the syntax and contents of the <code class="inline">.appup</code> file, see
│ │ │  <a href="../../lib/sasl-4.4/doc/html/appup.html"><code class="inline">appup</code></a> in SASL.</p><p><a href="appup_cookbook.html">Appup Cookbook</a> includes examples of <code class="inline">.appup</code> files for
│ │ │  typical upgrade/downgrade cases.</p><p><em>Example:</em> Consider the release <code class="inline">ch_rel-1</code> from
│ │ │  <a href="release_structure.html#ch_rel">Releases</a>. Assume you want to add a function
│ │ │  <code class="inline">available/0</code> to server <code class="inline">ch3</code>, which returns the number of available channels
│ │ │  (when trying out the example, make the change in a copy of the original
│ │ │ -directory, to ensure that the first version is still available):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8637745585-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="8637745585-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="8637745585-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="8637745585-2">)</span><span class="p">.</span><span class="w">
│ │ │ +directory, to ensure that the first version is still available):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1430035099-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="1430035099-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="1430035099-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="1430035099-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8637745585-3">(</span><span class="p" data-group-id="8637745585-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8637745585-4">]</span><span class="p" data-group-id="8637745585-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8637745585-5">(</span><span class="p" data-group-id="8637745585-6">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8637745585-6">]</span><span class="p" data-group-id="8637745585-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8637745585-7">(</span><span class="p" data-group-id="8637745585-8">[</span><span class="ss">available</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8637745585-8">]</span><span class="p" data-group-id="8637745585-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8637745585-9">(</span><span class="p" data-group-id="8637745585-10">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8637745585-10">]</span><span class="p" data-group-id="8637745585-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1430035099-3">(</span><span class="p" data-group-id="1430035099-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1430035099-4">]</span><span class="p" data-group-id="1430035099-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1430035099-5">(</span><span class="p" data-group-id="1430035099-6">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1430035099-6">]</span><span class="p" data-group-id="1430035099-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1430035099-7">(</span><span class="p" data-group-id="1430035099-8">[</span><span class="ss">available</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1430035099-8">]</span><span class="p" data-group-id="1430035099-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1430035099-9">(</span><span class="p" data-group-id="1430035099-10">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1430035099-10">]</span><span class="p" data-group-id="1430035099-9">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="8637745585-11">(</span><span class="p" data-group-id="8637745585-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="8637745585-12">(</span><span class="p" data-group-id="8637745585-13">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="8637745585-13">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8637745585-14">[</span><span class="p" data-group-id="8637745585-14">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8637745585-15">[</span><span class="p" data-group-id="8637745585-15">]</span><span class="p" data-group-id="8637745585-12">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="1430035099-11">(</span><span class="p" data-group-id="1430035099-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="1430035099-12">(</span><span class="p" data-group-id="1430035099-13">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="1430035099-13">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1430035099-14">[</span><span class="p" data-group-id="1430035099-14">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1430035099-15">[</span><span class="p" data-group-id="1430035099-15">]</span><span class="p" data-group-id="1430035099-12">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="8637745585-16">(</span><span class="p" data-group-id="8637745585-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="8637745585-17">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="8637745585-17">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="1430035099-16">(</span><span class="p" data-group-id="1430035099-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="1430035099-17">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="1430035099-17">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="8637745585-18">(</span><span class="n">Ch</span><span class="p" data-group-id="8637745585-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="8637745585-19">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8637745585-20">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="8637745585-20">}</span><span class="p" data-group-id="8637745585-19">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="1430035099-18">(</span><span class="n">Ch</span><span class="p" data-group-id="1430035099-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="1430035099-19">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1430035099-20">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1430035099-20">}</span><span class="p" data-group-id="1430035099-19">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">available</span><span class="p" data-group-id="8637745585-21">(</span><span class="p" data-group-id="8637745585-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="8637745585-22">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">available</span><span class="p" data-group-id="8637745585-22">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">available</span><span class="p" data-group-id="1430035099-21">(</span><span class="p" data-group-id="1430035099-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="1430035099-22">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">available</span><span class="p" data-group-id="1430035099-22">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="8637745585-23">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="8637745585-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8637745585-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="8637745585-25">(</span><span class="p" data-group-id="8637745585-25">)</span><span class="p" data-group-id="8637745585-24">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="1430035099-23">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="1430035099-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1430035099-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="1430035099-25">(</span><span class="p" data-group-id="1430035099-25">)</span><span class="p" data-group-id="1430035099-24">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="8637745585-26">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="8637745585-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8637745585-27">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="8637745585-27">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="8637745585-28">(</span><span class="n">Chs</span><span class="p" data-group-id="8637745585-28">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8637745585-29">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="8637745585-29">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="8637745585-30">(</span><span class="ss">available</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="8637745585-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">available</span><span class="p" data-group-id="8637745585-31">(</span><span class="n">Chs</span><span class="p" data-group-id="8637745585-31">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8637745585-32">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="8637745585-32">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="1430035099-26">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1430035099-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1430035099-27">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="1430035099-27">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="1430035099-28">(</span><span class="n">Chs</span><span class="p" data-group-id="1430035099-28">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1430035099-29">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="1430035099-29">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="1430035099-30">(</span><span class="ss">available</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1430035099-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">available</span><span class="p" data-group-id="1430035099-31">(</span><span class="n">Chs</span><span class="p" data-group-id="1430035099-31">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1430035099-32">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1430035099-32">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="8637745585-33">(</span><span class="p" data-group-id="8637745585-34">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="8637745585-34">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="8637745585-33">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="8637745585-35">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="8637745585-35">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8637745585-36">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="8637745585-36">}</span><span class="p">.</span></code></pre><p>A new version of the <code class="inline">ch_app.app</code> file must now be created, where the version is
│ │ │ -updated:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0241285678-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0241285678-2">[</span><span class="p" data-group-id="0241285678-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="0241285678-3">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="0241285678-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="0241285678-4">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="0241285678-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0241285678-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="0241285678-6">]</span><span class="p" data-group-id="0241285678-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="0241285678-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0241285678-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="0241285678-8">]</span><span class="p" data-group-id="0241285678-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="0241285678-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0241285678-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="0241285678-10">]</span><span class="p" data-group-id="0241285678-9">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="0241285678-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0241285678-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="0241285678-13">[</span><span class="p" data-group-id="0241285678-13">]</span><span class="p" data-group-id="0241285678-12">}</span><span class="p" data-group-id="0241285678-11">}</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0241285678-2">]</span><span class="p" data-group-id="0241285678-1">}</span><span class="p">.</span></code></pre><p>To upgrade <code class="inline">ch_app</code> from <code class="inline">&quot;1&quot;</code> to <code class="inline">&quot;2&quot;</code> (and to downgrade from <code class="inline">&quot;2&quot;</code> to <code class="inline">&quot;1&quot;</code>),
│ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="1430035099-33">(</span><span class="p" data-group-id="1430035099-34">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1430035099-34">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1430035099-33">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="1430035099-35">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1430035099-35">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1430035099-36">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="1430035099-36">}</span><span class="p">.</span></code></pre><p>A new version of the <code class="inline">ch_app.app</code> file must now be created, where the version is
│ │ │ +updated:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9870589377-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9870589377-2">[</span><span class="p" data-group-id="9870589377-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="9870589377-3">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="9870589377-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="9870589377-4">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="9870589377-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9870589377-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="9870589377-6">]</span><span class="p" data-group-id="9870589377-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="9870589377-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9870589377-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="9870589377-8">]</span><span class="p" data-group-id="9870589377-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="9870589377-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9870589377-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="9870589377-10">]</span><span class="p" data-group-id="9870589377-9">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="9870589377-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9870589377-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="9870589377-13">[</span><span class="p" data-group-id="9870589377-13">]</span><span class="p" data-group-id="9870589377-12">}</span><span class="p" data-group-id="9870589377-11">}</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9870589377-2">]</span><span class="p" data-group-id="9870589377-1">}</span><span class="p">.</span></code></pre><p>To upgrade <code class="inline">ch_app</code> from <code class="inline">&quot;1&quot;</code> to <code class="inline">&quot;2&quot;</code> (and to downgrade from <code class="inline">&quot;2&quot;</code> to <code class="inline">&quot;1&quot;</code>),
│ │ │  you only need to load the new (old) version of the <code class="inline">ch3</code> callback module. Create
│ │ │ -the application upgrade file <code class="inline">ch_app.appup</code> in the <code class="inline">ebin</code> directory:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1203284601-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1203284601-2">[</span><span class="p" data-group-id="1203284601-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1203284601-4">[</span><span class="p" data-group-id="1203284601-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="1203284601-5">}</span><span class="p" data-group-id="1203284601-4">]</span><span class="p" data-group-id="1203284601-3">}</span><span class="p" data-group-id="1203284601-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1203284601-6">[</span><span class="p" data-group-id="1203284601-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1203284601-8">[</span><span class="p" data-group-id="1203284601-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="1203284601-9">}</span><span class="p" data-group-id="1203284601-8">]</span><span class="p" data-group-id="1203284601-7">}</span><span class="p" data-group-id="1203284601-6">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1203284601-1">}</span><span class="p">.</span></code></pre><p><a href="" id="relup"></a></p><h2 id="release-upgrade-file" class="section-heading">
│ │ │ +the application upgrade file <code class="inline">ch_app.appup</code> in the <code class="inline">ebin</code> directory:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5416559075-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5416559075-2">[</span><span class="p" data-group-id="5416559075-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5416559075-4">[</span><span class="p" data-group-id="5416559075-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="5416559075-5">}</span><span class="p" data-group-id="5416559075-4">]</span><span class="p" data-group-id="5416559075-3">}</span><span class="p" data-group-id="5416559075-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5416559075-6">[</span><span class="p" data-group-id="5416559075-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5416559075-8">[</span><span class="p" data-group-id="5416559075-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="5416559075-9">}</span><span class="p" data-group-id="5416559075-8">]</span><span class="p" data-group-id="5416559075-7">}</span><span class="p" data-group-id="5416559075-6">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5416559075-1">}</span><span class="p">.</span></code></pre><p><a href="" id="relup"></a></p><h2 id="release-upgrade-file" class="section-heading">
│ │ │    <a href="#release-upgrade-file" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Release Upgrade File</span>
│ │ │  </h2>
│ │ │  <p>To define how to upgrade/downgrade between the new version and previous versions
│ │ │  of a release, a <em>release upgrade file</em>, or in short <code class="inline">.relup</code> file, is to be
│ │ │ @@ -405,22 +405,22 @@
│ │ │  are to be added and deleted, and which applications that must be upgraded and/or
│ │ │  downgraded. The instructions for this are fetched from the <code class="inline">.appup</code> files and
│ │ │  transformed into a single list of low-level instructions in the right order.</p><p>If the <code class="inline">relup</code> file is relatively simple, it can be created manually. It is only
│ │ │  to contain low-level instructions.</p><p>For details about the syntax and contents of the release upgrade file, see
│ │ │  <a href="../../lib/sasl-4.4/doc/html/relup.html"><code class="inline">relup</code></a> in SASL.</p><p><em>Example, continued from the previous section:</em> You have a new version &quot;2&quot; of
│ │ │  <code class="inline">ch_app</code> and an <code class="inline">.appup</code> file. A new version of the <code class="inline">.rel</code> file is also needed.
│ │ │  This time the file is called <code class="inline">ch_rel-2.rel</code> and the release version string is
│ │ │ -changed from &quot;A&quot; to &quot;B&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9077903937-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9077903937-2">{</span><span class="s">&quot;ch_rel&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="9077903937-2">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9077903937-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;14.2.5&quot;</span><span class="p" data-group-id="9077903937-3">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9077903937-4">[</span><span class="p" data-group-id="9077903937-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;9.2.4&quot;</span><span class="p" data-group-id="9077903937-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9077903937-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.2.3&quot;</span><span class="p" data-group-id="9077903937-6">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9077903937-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;4.2.1&quot;</span><span class="p" data-group-id="9077903937-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9077903937-8">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="9077903937-8">}</span><span class="p" data-group-id="9077903937-4">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9077903937-1">}</span><span class="p">.</span></code></pre><p>Now the <code class="inline">relup</code> file can be generated:</p><pre><code class="text">1&gt; systools:make_relup(&quot;ch_rel-2&quot;, [&quot;ch_rel-1&quot;], [&quot;ch_rel-1&quot;]).
│ │ │ +changed from &quot;A&quot; to &quot;B&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8872706182-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8872706182-2">{</span><span class="s">&quot;ch_rel&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="8872706182-2">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8872706182-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;14.2.5&quot;</span><span class="p" data-group-id="8872706182-3">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8872706182-4">[</span><span class="p" data-group-id="8872706182-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;9.2.4&quot;</span><span class="p" data-group-id="8872706182-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8872706182-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.2.3&quot;</span><span class="p" data-group-id="8872706182-6">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8872706182-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;4.2.1&quot;</span><span class="p" data-group-id="8872706182-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8872706182-8">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="8872706182-8">}</span><span class="p" data-group-id="8872706182-4">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8872706182-1">}</span><span class="p">.</span></code></pre><p>Now the <code class="inline">relup</code> file can be generated:</p><pre><code class="text">1&gt; systools:make_relup(&quot;ch_rel-2&quot;, [&quot;ch_rel-1&quot;], [&quot;ch_rel-1&quot;]).
│ │ │  ok</code></pre><p>This generates a <code class="inline">relup</code> file with instructions for how to upgrade from version
│ │ │  &quot;A&quot; (&quot;ch_rel-1&quot;) to version &quot;B&quot; (&quot;ch_rel-2&quot;) and how to downgrade from version
│ │ │  &quot;B&quot; to version &quot;A&quot;.</p><p>Both the old and new versions of the <code class="inline">.app</code> and <code class="inline">.rel</code> files must be in the code
│ │ │  path, as well as the <code class="inline">.appup</code> and (new) <code class="inline">.beam</code> files. The code path can be
│ │ │  extended by using the option <code class="inline">path</code>:</p><pre><code class="text">1&gt; systools:make_relup(&quot;ch_rel-2&quot;, [&quot;ch_rel-1&quot;], [&quot;ch_rel-1&quot;],
│ │ │  [{path,[&quot;../ch_rel-1&quot;,
│ │ │  &quot;../ch_rel-1/lib/ch_app-1/ebin&quot;]}]).
│ │ │ @@ -433,25 +433,25 @@
│ │ │  <p>When you have made a new version of a release, a release package can be created
│ │ │  with this new version and transferred to the target environment.</p><p>To install the new version of the release in runtime, the <em>release
│ │ │  handler</em> is used. This is a process belonging to the SASL application,
│ │ │  which handles unpacking, installation, and removal of release
│ │ │  packages. The <a href="../../lib/sasl-4.4/doc/html/release_handler.html"><code class="inline">release_handler</code></a> module communicates with this process.</p><p>Assuming there is an operational target system with installation root directory
│ │ │  <code class="inline">$ROOT</code>, the release package with the new version of the release is to be copied
│ │ │  to <code class="inline">$ROOT/releases</code>.</p><p>First, <em>unpack</em> the release package. The files are then extracted from the
│ │ │ -package:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">unpack_release</span><span class="p" data-group-id="7130602917-1">(</span><span class="n">ReleaseName</span><span class="p" data-group-id="7130602917-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7130602917-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Vsn</span><span class="p" data-group-id="7130602917-2">}</span></code></pre><ul><li><code class="inline">ReleaseName</code> is the name of the release package except the <code class="inline">.tar.gz</code>
│ │ │ +package:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">unpack_release</span><span class="p" data-group-id="5176887214-1">(</span><span class="n">ReleaseName</span><span class="p" data-group-id="5176887214-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5176887214-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Vsn</span><span class="p" data-group-id="5176887214-2">}</span></code></pre><ul><li><code class="inline">ReleaseName</code> is the name of the release package except the <code class="inline">.tar.gz</code>
│ │ │  extension.</li><li><code class="inline">Vsn</code> is the version of the unpacked release, as defined in its <code class="inline">.rel</code> file.</li></ul><p>A directory <code class="inline">$ROOT/lib/releases/Vsn</code> is created, where the <code class="inline">.rel</code> file, the boot
│ │ │  script <code class="inline">start.boot</code>, the system configuration file <code class="inline">sys.config</code>, and <code class="inline">relup</code> are
│ │ │  placed. For applications with new version numbers, the application directories
│ │ │  are placed under <code class="inline">$ROOT/lib</code>. Unchanged applications are not affected.</p><p>An unpacked release can be <em>installed</em>. The release handler then evaluates the
│ │ │ -instructions in <code class="inline">relup</code>, step by step:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="5320921936-1">(</span><span class="n">Vsn</span><span class="p" data-group-id="5320921936-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5320921936-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FromVsn</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5320921936-3">[</span><span class="p" data-group-id="5320921936-3">]</span><span class="p" data-group-id="5320921936-2">}</span></code></pre><p>If an error occurs during the installation, the system is rebooted using the old
│ │ │ +instructions in <code class="inline">relup</code>, step by step:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="6490502121-1">(</span><span class="n">Vsn</span><span class="p" data-group-id="6490502121-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6490502121-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FromVsn</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6490502121-3">[</span><span class="p" data-group-id="6490502121-3">]</span><span class="p" data-group-id="6490502121-2">}</span></code></pre><p>If an error occurs during the installation, the system is rebooted using the old
│ │ │  version of the release. If installation succeeds, the system is afterwards using
│ │ │  the new version of the release, but if anything happens and the system is
│ │ │  rebooted, it starts using the previous version again.</p><p>To be made the default version, the newly installed release must be made
│ │ │  <em>permanent</em>, which means the previous version becomes <em>old</em>:</p><pre><code class="text">release_handler:make_permanent(Vsn) =&gt; ok</code></pre><p>The system keeps information about which versions are old and permanent in the
│ │ │ -files <code class="inline">$ROOT/releases/RELEASES</code> and <code class="inline">$ROOT/releases/start_erl.data</code>.</p><p>To downgrade from <code class="inline">Vsn</code> to <code class="inline">FromVsn</code>, <code class="inline">install_release</code> must be called again:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="3667341631-1">(</span><span class="n">FromVsn</span><span class="p" data-group-id="3667341631-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3667341631-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Vsn</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3667341631-3">[</span><span class="p" data-group-id="3667341631-3">]</span><span class="p" data-group-id="3667341631-2">}</span></code></pre><p>An installed, but not permanent, release can be <em>removed</em>. Information about the
│ │ │ +files <code class="inline">$ROOT/releases/RELEASES</code> and <code class="inline">$ROOT/releases/start_erl.data</code>.</p><p>To downgrade from <code class="inline">Vsn</code> to <code class="inline">FromVsn</code>, <code class="inline">install_release</code> must be called again:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="6602557505-1">(</span><span class="n">FromVsn</span><span class="p" data-group-id="6602557505-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6602557505-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Vsn</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6602557505-3">[</span><span class="p" data-group-id="6602557505-3">]</span><span class="p" data-group-id="6602557505-2">}</span></code></pre><p>An installed, but not permanent, release can be <em>removed</em>. Information about the
│ │ │  release is then deleted from <code class="inline">$ROOT/releases/RELEASES</code> and the release-specific
│ │ │  code, that is, the new application directories and the <code class="inline">$ROOT/releases/Vsn</code>
│ │ │  directory, are removed.</p><pre><code class="text">release_handler:remove_release(Vsn) =&gt; ok</code></pre><h3 id="example-continued-from-the-previous-sections" class="section-heading">
│ │ │    <a href="#example-continued-from-the-previous-sections" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Example (continued from the previous sections)</span>
│ │ │ @@ -462,17 +462,17 @@
│ │ │  is needed, the file is to contain the empty list:</p><pre><code class="text">[].</code></pre><p><em>Step 2)</em> Start the system as a simple target system. In reality, it is to be
│ │ │  started as an embedded system. However, using <code class="inline">erl</code> with the correct boot script
│ │ │  and config file is enough for illustration purposes:</p><pre><code class="text">% cd $ROOT
│ │ │  % bin/erl -boot $ROOT/releases/A/start -config $ROOT/releases/A/sys
│ │ │  ...</code></pre><p><code class="inline">$ROOT</code> is the installation directory of the target system.</p><p><em>Step 3)</em> In another Erlang shell, generate start scripts and create a release
│ │ │  package for the new version <code class="inline">&quot;B&quot;</code>. Remember to include (a possible updated)
│ │ │  <code class="inline">sys.config</code> and the <code class="inline">relup</code> file. For more information, see
│ │ │ -<a href="release_handling.html#relup">Release Upgrade File</a>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="7375092781-1">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="7375092781-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<a href="release_handling.html#relup">Release Upgrade File</a>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="7496723053-1">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="7496723053-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="7375092781-2">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="7375092781-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="7496723053-2">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="7496723053-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>The new release package now also contains version &quot;2&quot; of <code class="inline">ch_app</code> and the
│ │ │  <code class="inline">relup</code> file:</p><pre><code class="text">% tar tf ch_rel-2.tar
│ │ │  lib/kernel-9.2.4/ebin/kernel.app
│ │ │  lib/kernel-9.2.4/ebin/application.beam
│ │ │  ...
│ │ │  lib/stdlib-5.2.3/ebin/stdlib.app
│ │ │  lib/stdlib-5.2.3/ebin/argparse.beam
│ │ │ @@ -485,31 +485,31 @@
│ │ │  lib/ch_app-2/ebin/ch_sup.beam
│ │ │  lib/ch_app-2/ebin/ch3.beam
│ │ │  releases/B/start.boot
│ │ │  releases/B/relup
│ │ │  releases/B/sys.config
│ │ │  releases/B/ch_rel-2.rel
│ │ │  releases/ch_rel-2.rel</code></pre><p><em>Step 4)</em> Copy the release package <code class="inline">ch_rel-2.tar.gz</code> to the <code class="inline">$ROOT/releases</code>
│ │ │ -directory.</p><p><em>Step 5)</em> In the running target system, unpack the release package:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">unpack_release</span><span class="p" data-group-id="2068829756-1">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="2068829756-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2068829756-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="2068829756-2">}</span></code></pre><p>The new application version <code class="inline">ch_app-2</code> is installed under <code class="inline">$ROOT/lib</code> next to
│ │ │ +directory.</p><p><em>Step 5)</em> In the running target system, unpack the release package:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">unpack_release</span><span class="p" data-group-id="6476374406-1">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="6476374406-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6476374406-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="6476374406-2">}</span></code></pre><p>The new application version <code class="inline">ch_app-2</code> is installed under <code class="inline">$ROOT/lib</code> next to
│ │ │  <code class="inline">ch_app-1</code>. The <code class="inline">kernel</code>, <code class="inline">stdlib</code>, and <code class="inline">sasl</code> directories are not affected, as
│ │ │  they have not changed.</p><p>Under <code class="inline">$ROOT/releases</code>, a new directory <code class="inline">B</code> is created, containing
│ │ │ -<code class="inline">ch_rel-2.rel</code>, <code class="inline">start.boot</code>, <code class="inline">sys.config</code>, and <code class="inline">relup</code>.</p><p><em>Step 6)</em> Check if the function <code class="inline">ch3:available/0</code> is available:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">ch3</span><span class="p">:</span><span class="nf">available</span><span class="p" data-group-id="5392442303-1">(</span><span class="p" data-group-id="5392442303-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">ch_rel-2.rel</code>, <code class="inline">start.boot</code>, <code class="inline">sys.config</code>, and <code class="inline">relup</code>.</p><p><em>Step 6)</em> Check if the function <code class="inline">ch3:available/0</code> is available:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">ch3</span><span class="p">:</span><span class="nf">available</span><span class="p" data-group-id="8365890483-1">(</span><span class="p" data-group-id="8365890483-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: undefined function ch3:available/0</span></code></pre><p><em>Step 7)</em> Install the new release. The instructions in <code class="inline">$ROOT/releases/B/relup</code>
│ │ │  are executed one by one, resulting in the new version of <code class="inline">ch3</code> being loaded. The
│ │ │ -function <code class="inline">ch3:available/0</code> is now available:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="5740965796-1">(</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="5740965796-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5740965796-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="p" data-group-id="5740965796-3">[</span><span class="p" data-group-id="5740965796-3">]</span><span class="p" data-group-id="5740965796-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">ch3</span><span class="p">:</span><span class="nf">available</span><span class="p" data-group-id="5740965796-4">(</span><span class="p" data-group-id="5740965796-4">)</span><span class="p">.</span><span class="w">
│ │ │ +function <code class="inline">ch3:available/0</code> is now available:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="8155443655-1">(</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="8155443655-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8155443655-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="p" data-group-id="8155443655-3">[</span><span class="p" data-group-id="8155443655-3">]</span><span class="p" data-group-id="8155443655-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">ch3</span><span class="p">:</span><span class="nf">available</span><span class="p" data-group-id="8155443655-4">(</span><span class="p" data-group-id="8155443655-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">code</span><span class="p">:</span><span class="nf">which</span><span class="p" data-group-id="5740965796-5">(</span><span class="ss">ch3</span><span class="p" data-group-id="5740965796-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">code</span><span class="p">:</span><span class="nf">which</span><span class="p" data-group-id="8155443655-5">(</span><span class="ss">ch3</span><span class="p" data-group-id="8155443655-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;.../lib/ch_app-2/ebin/ch3.beam&quot;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nc">code</span><span class="p">:</span><span class="nf">which</span><span class="p" data-group-id="5740965796-6">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="5740965796-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nc">code</span><span class="p">:</span><span class="nf">which</span><span class="p" data-group-id="8155443655-6">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="8155443655-6">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;.../lib/ch_app-1/ebin/ch_sup.beam&quot;</span></code></pre><p>Processes in <code class="inline">ch_app</code> for which code has not been updated, for example, the
│ │ │  supervisor, are still evaluating code from <code class="inline">ch_app-1</code>.</p><p><em>Step 8)</em> If the target system is now rebooted, it uses version &quot;A&quot; again. The
│ │ │ -&quot;B&quot; version must be made permanent, to be used when the system is rebooted.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">7&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">make_permanent</span><span class="p" data-group-id="1182231215-1">(</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="1182231215-1">)</span><span class="p">.</span><span class="w">
│ │ │ +&quot;B&quot; version must be made permanent, to be used when the system is rebooted.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">7&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">make_permanent</span><span class="p" data-group-id="7355754231-1">(</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="7355754231-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p><a href="" id="sys"></a></p><h2 id="updating-application-specifications" class="section-heading">
│ │ │    <a href="#updating-application-specifications" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Updating Application Specifications</span>
│ │ │  </h2>
│ │ │  <p>When a new version of a release is installed, the application specifications are
│ │ │ @@ -518,15 +518,15 @@
│ │ │  boot script is generated from the same <code class="inline">.rel</code> file as is used to build the
│ │ │  release package itself.</p></section><p>Specifically, the application configuration parameters are automatically updated
│ │ │  according to (in increasing priority order):</p><ul><li>The data in the boot script, fetched from the new application resource file
│ │ │  <code class="inline">App.app</code></li><li>The new <code class="inline">sys.config</code></li><li>Command-line arguments <code class="inline">-App Par Val</code></li></ul><p>This means that parameter values set in the other system configuration files and
│ │ │  values set using <a href="../../lib/kernel-11.0/doc/html/application.html#set_env/3"><code class="inline">application:set_env/3</code></a> are disregarded.</p><p>When an installed release is made permanent, the system process <code class="inline">init</code> is set to
│ │ │  point out the new <code class="inline">sys.config</code>.</p><p>After the installation, the application controller compares the old and new
│ │ │  configuration parameters for all running applications and calls the callback
│ │ │ -function:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">config_change</span><span class="p" data-group-id="6570618002-1">(</span><span class="n">Changed</span><span class="p">,</span><span class="w"> </span><span class="n">New</span><span class="p">,</span><span class="w"> </span><span class="n">Removed</span><span class="p" data-group-id="6570618002-1">)</span></code></pre><ul><li><code class="inline">Module</code> is the application callback module as defined by the <code class="inline">mod</code> key in the
│ │ │ +function:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">config_change</span><span class="p" data-group-id="3335365432-1">(</span><span class="n">Changed</span><span class="p">,</span><span class="w"> </span><span class="n">New</span><span class="p">,</span><span class="w"> </span><span class="n">Removed</span><span class="p" data-group-id="3335365432-1">)</span></code></pre><ul><li><code class="inline">Module</code> is the application callback module as defined by the <code class="inline">mod</code> key in the
│ │ │  <code class="inline">.app</code> file.</li><li><code class="inline">Changed</code> and <code class="inline">New</code> are lists of <code class="inline">{Par,Val}</code> for all changed and added
│ │ │  configuration parameters, respectively.</li><li><code class="inline">Removed</code> is a list of all parameters <code class="inline">Par</code> that have been removed.</li></ul><p>The function is optional and can be omitted when implementing an application
│ │ │  callback module.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/release_structure.html
│ │ │ @@ -136,37 +136,37 @@
│ │ │    <a href="#release-resource-file" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Release Resource File</span>
│ │ │  </h2>
│ │ │  <p>To define a release, create a <em>release resource file</em>, or in short a <code class="inline">.rel</code>
│ │ │  file. In the file, specify the name and version of the release, which ERTS
│ │ │ -version it is based on, and which applications it consists of:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0323288498-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0323288498-2">{</span><span class="n">Name</span><span class="p">,</span><span class="n">Vsn</span><span class="p" data-group-id="0323288498-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0323288498-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">EVsn</span><span class="p" data-group-id="0323288498-3">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0323288498-4">[</span><span class="p" data-group-id="0323288498-5">{</span><span class="n">Application1</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsn1</span><span class="p" data-group-id="0323288498-5">}</span><span class="p">,</span><span class="w">
│ │ │ +version it is based on, and which applications it consists of:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1551446695-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1551446695-2">{</span><span class="n">Name</span><span class="p">,</span><span class="n">Vsn</span><span class="p" data-group-id="1551446695-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1551446695-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">EVsn</span><span class="p" data-group-id="1551446695-3">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="1551446695-4">[</span><span class="p" data-group-id="1551446695-5">{</span><span class="n">Application1</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsn1</span><span class="p" data-group-id="1551446695-5">}</span><span class="p">,</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="0323288498-6">{</span><span class="n">ApplicationN</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsnN</span><span class="p" data-group-id="0323288498-6">}</span><span class="p" data-group-id="0323288498-4">]</span><span class="p" data-group-id="0323288498-1">}</span><span class="p">.</span></code></pre><p><code class="inline">Name</code>, <code class="inline">Vsn</code>, <code class="inline">EVsn</code>, and <code class="inline">AppVsn</code> are strings.</p><p>The file must be named <code class="inline">Rel.rel</code>, where <code class="inline">Rel</code> is a unique name.</p><p>Each <code class="inline">Application</code> (atom) and <code class="inline">AppVsn</code> is the name and version of an application
│ │ │ +  </span><span class="p" data-group-id="1551446695-6">{</span><span class="n">ApplicationN</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsnN</span><span class="p" data-group-id="1551446695-6">}</span><span class="p" data-group-id="1551446695-4">]</span><span class="p" data-group-id="1551446695-1">}</span><span class="p">.</span></code></pre><p><code class="inline">Name</code>, <code class="inline">Vsn</code>, <code class="inline">EVsn</code>, and <code class="inline">AppVsn</code> are strings.</p><p>The file must be named <code class="inline">Rel.rel</code>, where <code class="inline">Rel</code> is a unique name.</p><p>Each <code class="inline">Application</code> (atom) and <code class="inline">AppVsn</code> is the name and version of an application
│ │ │  included in the release. The minimal release based on Erlang/OTP consists of the
│ │ │  Kernel and STDLIB applications, so these applications must be included in the
│ │ │  list.</p><p>If the release is to be upgraded, it must also include the SASL application.</p><p><a href="" id="ch_rel"></a></p><p>Here is an example showing the <code class="inline">.app</code> file for a release of <code class="inline">ch_app</code> from
│ │ │ -the <a href="applications.html#ch_app">Applications</a> section:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5855145843-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5855145843-2">[</span><span class="p" data-group-id="5855145843-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="5855145843-3">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5855145843-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="5855145843-4">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5855145843-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5855145843-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="5855145843-6">]</span><span class="p" data-group-id="5855145843-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5855145843-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5855145843-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="5855145843-8">]</span><span class="p" data-group-id="5855145843-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5855145843-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5855145843-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="5855145843-10">]</span><span class="p" data-group-id="5855145843-9">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5855145843-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5855145843-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="5855145843-13">[</span><span class="p" data-group-id="5855145843-13">]</span><span class="p" data-group-id="5855145843-12">}</span><span class="p" data-group-id="5855145843-11">}</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5855145843-2">]</span><span class="p" data-group-id="5855145843-1">}</span><span class="p">.</span></code></pre><p>The <code class="inline">.rel</code> file must also contain <code class="inline">kernel</code>, <code class="inline">stdlib</code>, and <code class="inline">sasl</code>, as these
│ │ │ -applications are required by <code class="inline">ch_app</code>. The file is called <code class="inline">ch_rel-1.rel</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8819359918-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8819359918-2">{</span><span class="s">&quot;ch_rel&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;A&quot;</span><span class="p" data-group-id="8819359918-2">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8819359918-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;14.2.5&quot;</span><span class="p" data-group-id="8819359918-3">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8819359918-4">[</span><span class="p" data-group-id="8819359918-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;9.2.4&quot;</span><span class="p" data-group-id="8819359918-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="8819359918-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.2.3&quot;</span><span class="p" data-group-id="8819359918-6">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="8819359918-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;4.2.1&quot;</span><span class="p" data-group-id="8819359918-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="8819359918-8">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="8819359918-8">}</span><span class="p" data-group-id="8819359918-4">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8819359918-1">}</span><span class="p">.</span></code></pre><p><a href="" id="boot"></a></p><h2 id="generating-boot-scripts" class="section-heading">
│ │ │ +the <a href="applications.html#ch_app">Applications</a> section:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4499624957-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4499624957-2">[</span><span class="p" data-group-id="4499624957-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="4499624957-3">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4499624957-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="4499624957-4">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4499624957-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4499624957-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="4499624957-6">]</span><span class="p" data-group-id="4499624957-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4499624957-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4499624957-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="4499624957-8">]</span><span class="p" data-group-id="4499624957-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4499624957-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4499624957-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="4499624957-10">]</span><span class="p" data-group-id="4499624957-9">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4499624957-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4499624957-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="4499624957-13">[</span><span class="p" data-group-id="4499624957-13">]</span><span class="p" data-group-id="4499624957-12">}</span><span class="p" data-group-id="4499624957-11">}</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4499624957-2">]</span><span class="p" data-group-id="4499624957-1">}</span><span class="p">.</span></code></pre><p>The <code class="inline">.rel</code> file must also contain <code class="inline">kernel</code>, <code class="inline">stdlib</code>, and <code class="inline">sasl</code>, as these
│ │ │ +applications are required by <code class="inline">ch_app</code>. The file is called <code class="inline">ch_rel-1.rel</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4672484340-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4672484340-2">{</span><span class="s">&quot;ch_rel&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;A&quot;</span><span class="p" data-group-id="4672484340-2">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4672484340-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;14.2.5&quot;</span><span class="p" data-group-id="4672484340-3">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4672484340-4">[</span><span class="p" data-group-id="4672484340-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;9.2.4&quot;</span><span class="p" data-group-id="4672484340-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4672484340-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.2.3&quot;</span><span class="p" data-group-id="4672484340-6">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4672484340-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;4.2.1&quot;</span><span class="p" data-group-id="4672484340-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4672484340-8">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="4672484340-8">}</span><span class="p" data-group-id="4672484340-4">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4672484340-1">}</span><span class="p">.</span></code></pre><p><a href="" id="boot"></a></p><h2 id="generating-boot-scripts" class="section-heading">
│ │ │    <a href="#generating-boot-scripts" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Generating Boot Scripts</span>
│ │ │  </h2>
│ │ │  <p><a href="../../lib/sasl-4.4/doc/html/systools.html"><code class="inline">systools</code></a> in the SASL application includes tools to build and check
│ │ │  releases. The functions read the <code class="inline">.rel</code> and <code class="inline">.app</code> files and perform
│ │ │ @@ -190,17 +190,17 @@
│ │ │    <a href="#creating-a-release-package" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Creating a Release Package</span>
│ │ │  </h2>
│ │ │  <p>The <a href="../../lib/sasl-4.4/doc/html/systools.html#make_tar/2"><code class="inline">systools:make_tar/1,2</code></a> function takes a
│ │ │  <code class="inline">.rel</code> file as input and creates a zipped tar file with the code for
│ │ │ -the specified applications, a <em>release package</em>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="6288464365-1">(</span><span class="s">&quot;ch_rel-1&quot;</span><span class="p" data-group-id="6288464365-1">)</span><span class="p">.</span><span class="w">
│ │ │ +the specified applications, a <em>release package</em>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="1249929917-1">(</span><span class="s">&quot;ch_rel-1&quot;</span><span class="p" data-group-id="1249929917-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="6288464365-2">(</span><span class="s">&quot;ch_rel-1&quot;</span><span class="p" data-group-id="6288464365-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="1249929917-2">(</span><span class="s">&quot;ch_rel-1&quot;</span><span class="p" data-group-id="1249929917-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>The release package by default contains:</p><ul><li>The <code class="inline">.app</code> files</li><li>The <code class="inline">.rel</code> file</li><li>The object code for all applications, structured according to the
│ │ │  <a href="applications.html#app_dir">application directory structure</a></li><li>The binary boot script renamed to <code class="inline">start.boot</code></li></ul><pre><code class="text">% tar tf ch_rel-1.tar
│ │ │  lib/kernel-9.2.4/ebin/kernel.app
│ │ │  lib/kernel-9.2.4/ebin/application.beam
│ │ │  ...
│ │ │  lib/stdlib-5.2.3/ebin/stdlib.app
│ │ │  lib/stdlib-5.2.3/ebin/argparse.beam
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/robustness.html
│ │ │ @@ -128,68 +128,68 @@
│ │ │  </h2>
│ │ │  <p>Before improving the messenger program, let us look at some general principles,
│ │ │  using the ping pong program as an example. Recall that when &quot;ping&quot; finishes, it
│ │ │  tells &quot;pong&quot; that it has done so by sending the atom <code class="inline">finished</code> as a message to
│ │ │  &quot;pong&quot; so that &quot;pong&quot; can also finish. Another way to let &quot;pong&quot; finish is to
│ │ │  make &quot;pong&quot; exit if it does not receive a message from ping within a certain
│ │ │  time. This can be done by adding a <em>time-out</em> to <code class="inline">pong</code> as shown in the
│ │ │ -following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5458205902-1">(</span><span class="ss">tut19</span><span class="p" data-group-id="5458205902-1">)</span><span class="p">.</span><span class="w">
│ │ │ +following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1943290882-1">(</span><span class="ss">tut19</span><span class="p" data-group-id="1943290882-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5458205902-2">(</span><span class="p" data-group-id="5458205902-3">[</span><span class="ss">start_ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">start_pong</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5458205902-3">]</span><span class="p" data-group-id="5458205902-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1943290882-2">(</span><span class="p" data-group-id="1943290882-3">[</span><span class="ss">start_ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">start_pong</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1943290882-3">]</span><span class="p" data-group-id="1943290882-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="5458205902-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="5458205902-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5458205902-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5458205902-6">[</span><span class="p" data-group-id="5458205902-6">]</span><span class="p" data-group-id="5458205902-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="1943290882-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="1943290882-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1943290882-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1943290882-6">[</span><span class="p" data-group-id="1943290882-6">]</span><span class="p" data-group-id="1943290882-5">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="5458205902-7">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="5458205902-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5458205902-8">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="5458205902-8">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5458205902-9">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5458205902-10">(</span><span class="p" data-group-id="5458205902-10">)</span><span class="p" data-group-id="5458205902-9">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="1943290882-7">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="1943290882-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1943290882-8">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="1943290882-8">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1943290882-9">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1943290882-10">(</span><span class="p" data-group-id="1943290882-10">)</span><span class="p" data-group-id="1943290882-9">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5458205902-11">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5458205902-12">[</span><span class="p" data-group-id="5458205902-12">]</span><span class="p" data-group-id="5458205902-11">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1943290882-11">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1943290882-12">[</span><span class="p" data-group-id="1943290882-12">]</span><span class="p" data-group-id="1943290882-11">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="5458205902-13">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="5458205902-13">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="1943290882-13">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="1943290882-13">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="5458205902-14">(</span><span class="p" data-group-id="5458205902-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="1943290882-14">(</span><span class="p" data-group-id="1943290882-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5458205902-15">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="5458205902-15">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5458205902-16">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5458205902-17">[</span><span class="p" data-group-id="5458205902-17">]</span><span class="p" data-group-id="5458205902-16">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="1943290882-15">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="1943290882-15">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1943290882-16">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1943290882-17">[</span><span class="p" data-group-id="1943290882-17">]</span><span class="p" data-group-id="1943290882-16">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="5458205902-18">(</span><span class="p" data-group-id="5458205902-18">)</span><span class="w">
│ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="1943290882-18">(</span><span class="p" data-group-id="1943290882-18">)</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5458205902-19">(</span><span class="s">&quot;Pong timed out</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5458205902-20">[</span><span class="p" data-group-id="5458205902-20">]</span><span class="p" data-group-id="5458205902-19">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1943290882-19">(</span><span class="s">&quot;Pong timed out</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1943290882-20">[</span><span class="p" data-group-id="1943290882-20">]</span><span class="p" data-group-id="1943290882-19">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_pong</span><span class="p" data-group-id="5458205902-21">(</span><span class="p" data-group-id="5458205902-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="5458205902-22">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="5458205902-23">(</span><span class="ss">tut19</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5458205902-24">[</span><span class="p" data-group-id="5458205902-24">]</span><span class="p" data-group-id="5458205902-23">)</span><span class="p" data-group-id="5458205902-22">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_pong</span><span class="p" data-group-id="1943290882-21">(</span><span class="p" data-group-id="1943290882-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="1943290882-22">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="1943290882-23">(</span><span class="ss">tut19</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1943290882-24">[</span><span class="p" data-group-id="1943290882-24">]</span><span class="p" data-group-id="1943290882-23">)</span><span class="p" data-group-id="1943290882-22">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_ping</span><span class="p" data-group-id="5458205902-25">(</span><span class="n">Pong_Node</span><span class="p" data-group-id="5458205902-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="5458205902-26">(</span><span class="ss">tut19</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5458205902-27">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="5458205902-27">]</span><span class="p" data-group-id="5458205902-26">)</span><span class="p">.</span></code></pre><p>After this is compiled and the file <code class="inline">tut19.beam</code> is copied to the necessary
│ │ │ +</span><span class="nf">start_ping</span><span class="p" data-group-id="1943290882-25">(</span><span class="n">Pong_Node</span><span class="p" data-group-id="1943290882-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="1943290882-26">(</span><span class="ss">tut19</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1943290882-27">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="1943290882-27">]</span><span class="p" data-group-id="1943290882-26">)</span><span class="p">.</span></code></pre><p>After this is compiled and the file <code class="inline">tut19.beam</code> is copied to the necessary
│ │ │  directories, the following is seen on (pong@kosken):</p><pre><code class="text">(pong@kosken)1&gt; tut19:start_pong().
│ │ │  true
│ │ │  Pong received ping
│ │ │  Pong received ping
│ │ │  Pong received ping
│ │ │  Pong timed out</code></pre><p>And the following is seen on (ping@gollum):</p><pre><code class="text">(ping@gollum)1&gt; tut19:start_ping(pong@kosken).
│ │ │  &lt;0.36.0&gt;
│ │ │  Ping received pong
│ │ │  Ping received pong
│ │ │  Ping received pong
│ │ │ -ping finished</code></pre><p>The time-out is set in:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pong</span><span class="p" data-group-id="8924535418-1">(</span><span class="p" data-group-id="8924535418-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +ping finished</code></pre><p>The time-out is set in:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pong</span><span class="p" data-group-id="6570998672-1">(</span><span class="p" data-group-id="6570998672-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="8924535418-2">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="8924535418-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8924535418-3">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8924535418-4">[</span><span class="p" data-group-id="8924535418-4">]</span><span class="p" data-group-id="8924535418-3">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="6570998672-2">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="6570998672-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6570998672-3">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6570998672-4">[</span><span class="p" data-group-id="6570998672-4">]</span><span class="p" data-group-id="6570998672-3">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="8924535418-5">(</span><span class="p" data-group-id="8924535418-5">)</span><span class="w">
│ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="6570998672-5">(</span><span class="p" data-group-id="6570998672-5">)</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8924535418-6">(</span><span class="s">&quot;Pong timed out</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8924535418-7">[</span><span class="p" data-group-id="8924535418-7">]</span><span class="p" data-group-id="8924535418-6">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6570998672-6">(</span><span class="s">&quot;Pong timed out</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6570998672-7">[</span><span class="p" data-group-id="6570998672-7">]</span><span class="p" data-group-id="6570998672-6">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The time-out (<code class="inline">after 5000</code>) is started when <code class="inline">receive</code> is entered. The time-out
│ │ │  is canceled if <code class="inline">{ping,Ping_PID}</code> is received. If <code class="inline">{ping,Ping_PID}</code> is not
│ │ │  received, the actions following the time-out are done after 5000 milliseconds.
│ │ │  <code class="inline">after</code> must be last in the <code class="inline">receive</code>, that is, preceded by all other message
│ │ │  reception specifications in the <code class="inline">receive</code>. It is also possible to call a
│ │ │ -function that returns an integer for the time-out:</p><pre><code class="makeup erlang" translate="no"><span class="k">after</span><span class="w"> </span><span class="nf">pong_timeout</span><span class="p" data-group-id="7055488834-1">(</span><span class="p" data-group-id="7055488834-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>In general, there are better ways than using time-outs to supervise parts of a
│ │ │ +function that returns an integer for the time-out:</p><pre><code class="makeup erlang" translate="no"><span class="k">after</span><span class="w"> </span><span class="nf">pong_timeout</span><span class="p" data-group-id="6481607416-1">(</span><span class="p" data-group-id="6481607416-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>In general, there are better ways than using time-outs to supervise parts of a
│ │ │  distributed Erlang system. Time-outs are usually appropriate to supervise
│ │ │  external events, for example, if you have expected a message from some external
│ │ │  system within a specified time. For example, a time-out can be used to log a
│ │ │  user out of the messenger system if they have not accessed it for, say, ten
│ │ │  minutes.</p><h2 id="error-handling" class="section-heading">
│ │ │    <a href="#error-handling" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -209,96 +209,96 @@
│ │ │  something called a <em>signal</em> to all the processes it has links to.</p><p>The signal carries information about the pid it was sent from and the exit
│ │ │  reason.</p><p>The default behaviour of a process that receives a normal exit is to ignore the
│ │ │  signal.</p><p>The default behaviour in the two other cases (that is, abnormal exit) above is
│ │ │  to:</p><ul><li>Bypass all messages to the receiving process.</li><li>Kill the receiving process.</li><li>Propagate the same error signal to the links of the killed process.</li></ul><p>In this way you can connect all processes in a transaction together using links.
│ │ │  If one of the processes exits abnormally, all the processes in the transaction
│ │ │  are killed. As it is often wanted to create a process and link to it at the same
│ │ │  time, there is a special BIF, <a href="../../erts-17.0/doc/html/erlang.html#spawn_link/1">spawn_link</a> that does the
│ │ │ -same as <code class="inline">spawn</code>, but also creates a link to the spawned process.</p><p>Now an example of the ping pong example using links to terminate &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6172726557-1">(</span><span class="ss">tut20</span><span class="p" data-group-id="6172726557-1">)</span><span class="p">.</span><span class="w">
│ │ │ +same as <code class="inline">spawn</code>, but also creates a link to the spawned process.</p><p>Now an example of the ping pong example using links to terminate &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1595364805-1">(</span><span class="ss">tut20</span><span class="p" data-group-id="1595364805-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6172726557-2">(</span><span class="p" data-group-id="6172726557-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6172726557-3">]</span><span class="p" data-group-id="6172726557-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1595364805-2">(</span><span class="p" data-group-id="1595364805-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1595364805-3">]</span><span class="p" data-group-id="1595364805-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="6172726557-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="6172726557-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">link</span><span class="p" data-group-id="6172726557-5">(</span><span class="n">Pong_Pid</span><span class="p" data-group-id="6172726557-5">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping1</span><span class="p" data-group-id="6172726557-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="6172726557-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="1595364805-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1595364805-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">link</span><span class="p" data-group-id="1595364805-5">(</span><span class="n">Pong_Pid</span><span class="p" data-group-id="1595364805-5">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">ping1</span><span class="p" data-group-id="1595364805-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1595364805-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping1</span><span class="p" data-group-id="6172726557-7">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="6172726557-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">exit</span><span class="p" data-group-id="6172726557-8">(</span><span class="ss">ping</span><span class="p" data-group-id="6172726557-8">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">ping1</span><span class="p" data-group-id="1595364805-7">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="1595364805-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">exit</span><span class="p" data-group-id="1595364805-8">(</span><span class="ss">ping</span><span class="p" data-group-id="1595364805-8">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping1</span><span class="p" data-group-id="6172726557-9">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="6172726557-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Pong_Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6172726557-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6172726557-11">(</span><span class="p" data-group-id="6172726557-11">)</span><span class="p" data-group-id="6172726557-10">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">ping1</span><span class="p" data-group-id="1595364805-9">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1595364805-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pong_Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1595364805-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1595364805-11">(</span><span class="p" data-group-id="1595364805-11">)</span><span class="p" data-group-id="1595364805-10">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6172726557-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6172726557-13">[</span><span class="p" data-group-id="6172726557-13">]</span><span class="p" data-group-id="6172726557-12">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1595364805-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1595364805-13">[</span><span class="p" data-group-id="1595364805-13">]</span><span class="p" data-group-id="1595364805-12">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping1</span><span class="p" data-group-id="6172726557-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="6172726557-14">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">ping1</span><span class="p" data-group-id="1595364805-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1595364805-14">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="6172726557-15">(</span><span class="p" data-group-id="6172726557-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="1595364805-15">(</span><span class="p" data-group-id="1595364805-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="6172726557-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="6172726557-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6172726557-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6172726557-18">[</span><span class="p" data-group-id="6172726557-18">]</span><span class="p" data-group-id="6172726557-17">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="1595364805-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="1595364805-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1595364805-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1595364805-18">[</span><span class="p" data-group-id="1595364805-18">]</span><span class="p" data-group-id="1595364805-17">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="6172726557-19">(</span><span class="p" data-group-id="6172726557-19">)</span><span class="w">
│ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="1595364805-19">(</span><span class="p" data-group-id="1595364805-19">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="6172726557-20">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="6172726557-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">PongPID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="6172726557-21">(</span><span class="ss">tut20</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6172726557-22">[</span><span class="p" data-group-id="6172726557-22">]</span><span class="p" data-group-id="6172726557-21">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="6172726557-23">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut20</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6172726557-24">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">PongPID</span><span class="p" data-group-id="6172726557-24">]</span><span class="p" data-group-id="6172726557-23">)</span><span class="p">.</span></code></pre><pre><code class="text">(s1@bill)3&gt; tut20:start(s2@kosken).
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="1595364805-20">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="1595364805-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">PongPID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="1595364805-21">(</span><span class="ss">tut20</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1595364805-22">[</span><span class="p" data-group-id="1595364805-22">]</span><span class="p" data-group-id="1595364805-21">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="1595364805-23">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut20</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1595364805-24">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">PongPID</span><span class="p" data-group-id="1595364805-24">]</span><span class="p" data-group-id="1595364805-23">)</span><span class="p">.</span></code></pre><pre><code class="text">(s1@bill)3&gt; tut20:start(s2@kosken).
│ │ │  Pong received ping
│ │ │  &lt;3820.41.0&gt;
│ │ │  Ping received pong
│ │ │  Pong received ping
│ │ │  Ping received pong
│ │ │  Pong received ping
│ │ │  Ping received pong</code></pre><p>This is a slight modification of the ping pong program where both processes are
│ │ │  spawned from the same <code class="inline">start/1</code> function, and the &quot;ping&quot; process can be spawned
│ │ │  on a separate node. Notice the use of the <code class="inline">link</code> BIF. &quot;Ping&quot; calls
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#exit/1"><code class="inline">exit(ping)</code></a> when it finishes and this causes an exit signal to be
│ │ │  sent to &quot;pong&quot;, which also terminates.</p><p>It is possible to modify the default behaviour of a process so that it does not
│ │ │  get killed when it receives abnormal exit signals. Instead, all signals are
│ │ │  turned into normal messages of the format <code class="inline">{'EXIT',FromPID,Reason}</code> and added to
│ │ │ -the end of the receiving process' message queue. This behaviour is set by:</p><pre><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="4280161325-1">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4280161325-1">)</span></code></pre><p>There are several other process flags, see <a href="../../erts-17.0/doc/html/erlang.html#process_flag/2">erlang(3)</a>.
│ │ │ +the end of the receiving process' message queue. This behaviour is set by:</p><pre><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="0814341238-1">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0814341238-1">)</span></code></pre><p>There are several other process flags, see <a href="../../erts-17.0/doc/html/erlang.html#process_flag/2">erlang(3)</a>.
│ │ │  Changing the default behaviour of a process in this way is usually not done in
│ │ │  standard user programs, but is left to the supervisory programs in OTP. However,
│ │ │ -the ping pong program is modified to illustrate exit trapping.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0620773727-1">(</span><span class="ss">tut21</span><span class="p" data-group-id="0620773727-1">)</span><span class="p">.</span><span class="w">
│ │ │ +the ping pong program is modified to illustrate exit trapping.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1856569137-1">(</span><span class="ss">tut21</span><span class="p" data-group-id="1856569137-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0620773727-2">(</span><span class="p" data-group-id="0620773727-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0620773727-3">]</span><span class="p" data-group-id="0620773727-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1856569137-2">(</span><span class="p" data-group-id="1856569137-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1856569137-3">]</span><span class="p" data-group-id="1856569137-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="0620773727-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="0620773727-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">link</span><span class="p" data-group-id="0620773727-5">(</span><span class="n">Pong_Pid</span><span class="p" data-group-id="0620773727-5">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping1</span><span class="p" data-group-id="0620773727-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="0620773727-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="1856569137-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1856569137-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">link</span><span class="p" data-group-id="1856569137-5">(</span><span class="n">Pong_Pid</span><span class="p" data-group-id="1856569137-5">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">ping1</span><span class="p" data-group-id="1856569137-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1856569137-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping1</span><span class="p" data-group-id="0620773727-7">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="0620773727-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">exit</span><span class="p" data-group-id="0620773727-8">(</span><span class="ss">ping</span><span class="p" data-group-id="0620773727-8">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">ping1</span><span class="p" data-group-id="1856569137-7">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="1856569137-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">exit</span><span class="p" data-group-id="1856569137-8">(</span><span class="ss">ping</span><span class="p" data-group-id="1856569137-8">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping1</span><span class="p" data-group-id="0620773727-9">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="0620773727-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Pong_Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0620773727-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0620773727-11">(</span><span class="p" data-group-id="0620773727-11">)</span><span class="p" data-group-id="0620773727-10">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">ping1</span><span class="p" data-group-id="1856569137-9">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1856569137-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pong_Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1856569137-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1856569137-11">(</span><span class="p" data-group-id="1856569137-11">)</span><span class="p" data-group-id="1856569137-10">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0620773727-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0620773727-13">[</span><span class="p" data-group-id="0620773727-13">]</span><span class="p" data-group-id="0620773727-12">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1856569137-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1856569137-13">[</span><span class="p" data-group-id="1856569137-13">]</span><span class="p" data-group-id="1856569137-12">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping1</span><span class="p" data-group-id="0620773727-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="0620773727-14">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">ping1</span><span class="p" data-group-id="1856569137-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1856569137-14">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="0620773727-15">(</span><span class="p" data-group-id="0620773727-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="0620773727-16">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0620773727-16">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">pong1</span><span class="p" data-group-id="0620773727-17">(</span><span class="p" data-group-id="0620773727-17">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="1856569137-15">(</span><span class="p" data-group-id="1856569137-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="1856569137-16">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="1856569137-16">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">pong1</span><span class="p" data-group-id="1856569137-17">(</span><span class="p" data-group-id="1856569137-17">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">pong1</span><span class="p" data-group-id="0620773727-18">(</span><span class="p" data-group-id="0620773727-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">pong1</span><span class="p" data-group-id="1856569137-18">(</span><span class="p" data-group-id="1856569137-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0620773727-19">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="0620773727-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0620773727-20">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0620773727-21">[</span><span class="p" data-group-id="0620773727-21">]</span><span class="p" data-group-id="0620773727-20">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="1856569137-19">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="1856569137-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1856569137-20">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1856569137-21">[</span><span class="p" data-group-id="1856569137-21">]</span><span class="p" data-group-id="1856569137-20">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">pong1</span><span class="p" data-group-id="0620773727-22">(</span><span class="p" data-group-id="0620773727-22">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0620773727-23">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="0620773727-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0620773727-24">(</span><span class="s">&quot;pong exiting, got </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0620773727-25">[</span><span class="p" data-group-id="0620773727-26">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="0620773727-26">}</span><span class="p" data-group-id="0620773727-25">]</span><span class="p" data-group-id="0620773727-24">)</span><span class="w">
│ │ │ +            </span><span class="nf">pong1</span><span class="p" data-group-id="1856569137-22">(</span><span class="p" data-group-id="1856569137-22">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="1856569137-23">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="1856569137-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1856569137-24">(</span><span class="s">&quot;pong exiting, got </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1856569137-25">[</span><span class="p" data-group-id="1856569137-26">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="1856569137-26">}</span><span class="p" data-group-id="1856569137-25">]</span><span class="p" data-group-id="1856569137-24">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="0620773727-27">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="0620773727-27">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">PongPID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="0620773727-28">(</span><span class="ss">tut21</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0620773727-29">[</span><span class="p" data-group-id="0620773727-29">]</span><span class="p" data-group-id="0620773727-28">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="0620773727-30">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut21</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0620773727-31">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">PongPID</span><span class="p" data-group-id="0620773727-31">]</span><span class="p" data-group-id="0620773727-30">)</span><span class="p">.</span></code></pre><pre><code class="text">(s1@bill)1&gt; tut21:start(s2@gollum).
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="1856569137-27">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="1856569137-27">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">PongPID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="1856569137-28">(</span><span class="ss">tut21</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1856569137-29">[</span><span class="p" data-group-id="1856569137-29">]</span><span class="p" data-group-id="1856569137-28">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="1856569137-30">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut21</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1856569137-31">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">PongPID</span><span class="p" data-group-id="1856569137-31">]</span><span class="p" data-group-id="1856569137-30">)</span><span class="p">.</span></code></pre><pre><code class="text">(s1@bill)1&gt; tut21:start(s2@gollum).
│ │ │  &lt;3820.39.0&gt;
│ │ │  Pong received ping
│ │ │  Ping received pong
│ │ │  Pong received ping
│ │ │  Ping received pong
│ │ │  Pong received ping
│ │ │  Ping received pong
│ │ │ @@ -351,135 +351,135 @@
│ │ │  </span><span class="c1">%%% Started: messenger:client(Server_Node, Name)</span><span class="w">
│ │ │  </span><span class="c1">%%% To client: logoff</span><span class="w">
│ │ │  </span><span class="c1">%%% To client: {message_to, ToName, Message}</span><span class="w">
│ │ │  </span><span class="c1">%%%</span><span class="w">
│ │ │  </span><span class="c1">%%% Configuration: change the server_node() function to return the</span><span class="w">
│ │ │  </span><span class="c1">%%% name of the node where the messenger server runs</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5252788722-1">(</span><span class="ss">messenger</span><span class="p" data-group-id="5252788722-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5252788722-2">(</span><span class="p" data-group-id="5252788722-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5252788722-3">]</span><span class="p" data-group-id="5252788722-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3448786401-1">(</span><span class="ss">messenger</span><span class="p" data-group-id="3448786401-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3448786401-2">(</span><span class="p" data-group-id="3448786401-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3448786401-3">]</span><span class="p" data-group-id="3448786401-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Change the function below to return the name of the node where the</span><span class="w">
│ │ │  </span><span class="c1">%%% messenger server runs</span><span class="w">
│ │ │ -</span><span class="nf">server_node</span><span class="p" data-group-id="5252788722-4">(</span><span class="p" data-group-id="5252788722-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_node</span><span class="p" data-group-id="3448786401-4">(</span><span class="p" data-group-id="3448786401-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">messenger@super</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% This is the server process for the &quot;messenger&quot;</span><span class="w">
│ │ │  </span><span class="c1">%%% the user list has the format [{ClientPid1, Name1},{ClientPid2, Name2},...]</span><span class="w">
│ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="5252788722-5">(</span><span class="p" data-group-id="5252788722-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="5252788722-6">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="5252788722-6">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">server</span><span class="p" data-group-id="5252788722-7">(</span><span class="p" data-group-id="5252788722-8">[</span><span class="p" data-group-id="5252788722-8">]</span><span class="p" data-group-id="5252788722-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="3448786401-5">(</span><span class="p" data-group-id="3448786401-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="3448786401-6">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3448786401-6">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">server</span><span class="p" data-group-id="3448786401-7">(</span><span class="p" data-group-id="3448786401-8">[</span><span class="p" data-group-id="3448786401-8">]</span><span class="p" data-group-id="3448786401-7">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="5252788722-9">(</span><span class="n">User_List</span><span class="p" data-group-id="5252788722-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="3448786401-9">(</span><span class="n">User_List</span><span class="p" data-group-id="3448786401-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5252788722-10">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5252788722-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="5252788722-11">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5252788722-11">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="5252788722-12">(</span><span class="n">New_User_List</span><span class="p" data-group-id="5252788722-12">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5252788722-13">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="5252788722-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="5252788722-14">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5252788722-14">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="5252788722-15">(</span><span class="n">New_User_List</span><span class="p" data-group-id="5252788722-15">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5252788722-16">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5252788722-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="5252788722-17">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5252788722-17">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5252788722-18">(</span><span class="s">&quot;list is now: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5252788722-19">[</span><span class="n">User_List</span><span class="p" data-group-id="5252788722-19">]</span><span class="p" data-group-id="5252788722-18">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="5252788722-20">(</span><span class="n">User_List</span><span class="p" data-group-id="5252788722-20">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3448786401-10">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3448786401-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="3448786401-11">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3448786401-11">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="3448786401-12">(</span><span class="n">New_User_List</span><span class="p" data-group-id="3448786401-12">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3448786401-13">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="3448786401-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="3448786401-14">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3448786401-14">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="3448786401-15">(</span><span class="n">New_User_List</span><span class="p" data-group-id="3448786401-15">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3448786401-16">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3448786401-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="3448786401-17">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3448786401-17">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3448786401-18">(</span><span class="s">&quot;list is now: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3448786401-19">[</span><span class="n">User_List</span><span class="p" data-group-id="3448786401-19">]</span><span class="p" data-group-id="3448786401-18">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="3448786401-20">(</span><span class="n">User_List</span><span class="p" data-group-id="3448786401-20">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Start the server</span><span class="w">
│ │ │ -</span><span class="nf">start_server</span><span class="p" data-group-id="5252788722-21">(</span><span class="p" data-group-id="5252788722-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="5252788722-22">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="5252788722-23">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5252788722-24">[</span><span class="p" data-group-id="5252788722-24">]</span><span class="p" data-group-id="5252788722-23">)</span><span class="p" data-group-id="5252788722-22">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_server</span><span class="p" data-group-id="3448786401-21">(</span><span class="p" data-group-id="3448786401-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="3448786401-22">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="3448786401-23">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3448786401-24">[</span><span class="p" data-group-id="3448786401-24">]</span><span class="p" data-group-id="3448786401-23">)</span><span class="p" data-group-id="3448786401-22">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Server adds a new user to the user list</span><span class="w">
│ │ │ -</span><span class="nf">server_logon</span><span class="p" data-group-id="5252788722-25">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5252788722-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_logon</span><span class="p" data-group-id="3448786401-25">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3448786401-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% check if logged on anywhere else</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="5252788722-26">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5252788722-26">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="3448786401-26">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3448786401-26">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5252788722-27">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="5252788722-27">}</span><span class="p">,</span><span class="w">  </span><span class="c1">%reject logon</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3448786401-27">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="3448786401-27">}</span><span class="p">,</span><span class="w">  </span><span class="c1">%reject logon</span><span class="w">
│ │ │              </span><span class="n">User_List</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5252788722-28">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">logged_on</span><span class="p" data-group-id="5252788722-28">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">link</span><span class="p" data-group-id="5252788722-29">(</span><span class="n">From</span><span class="p" data-group-id="5252788722-29">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="5252788722-30">[</span><span class="p" data-group-id="5252788722-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5252788722-31">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5252788722-30">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3448786401-28">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">logged_on</span><span class="p" data-group-id="3448786401-28">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">link</span><span class="p" data-group-id="3448786401-29">(</span><span class="n">From</span><span class="p" data-group-id="3448786401-29">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="3448786401-30">[</span><span class="p" data-group-id="3448786401-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3448786401-31">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3448786401-30">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Server deletes a user from the user list</span><span class="w">
│ │ │ -</span><span class="nf">server_logoff</span><span class="p" data-group-id="5252788722-32">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5252788722-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="5252788722-33">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5252788722-33">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">server_logoff</span><span class="p" data-group-id="3448786401-32">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3448786401-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="3448786401-33">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3448786401-33">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  
│ │ │  </span><span class="c1">%%% Server transfers a message between users</span><span class="w">
│ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="5252788722-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5252788722-34">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="3448786401-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3448786401-34">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% check that the user is logged on and who he is</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="5252788722-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5252788722-35">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="3448786401-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3448786401-35">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5252788722-36">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="5252788722-36">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5252788722-37">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5252788722-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="5252788722-38">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5252788722-38">)</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3448786401-36">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="3448786401-36">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3448786401-37">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3448786401-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="3448786401-38">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3448786401-38">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% If the user exists, send the message</span><span class="w">
│ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="5252788722-39">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5252788722-39">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="3448786401-39">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3448786401-39">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Find the receiver and send the message</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="5252788722-40">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5252788722-40">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="3448786401-40">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3448786401-40">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5252788722-41">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="5252788722-41">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5252788722-42">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="5252788722-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5252788722-43">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5252788722-43">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5252788722-44">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="5252788722-44">}</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3448786401-41">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="3448786401-41">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3448786401-42">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="3448786401-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3448786401-43">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3448786401-43">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3448786401-44">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="3448786401-44">}</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% User Commands</span><span class="w">
│ │ │ -</span><span class="nf">logon</span><span class="p" data-group-id="5252788722-45">(</span><span class="n">Name</span><span class="p" data-group-id="5252788722-45">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="5252788722-46">(</span><span class="ss">mess_client</span><span class="p" data-group-id="5252788722-46">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">logon</span><span class="p" data-group-id="3448786401-45">(</span><span class="n">Name</span><span class="p" data-group-id="3448786401-45">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="3448786401-46">(</span><span class="ss">mess_client</span><span class="p" data-group-id="3448786401-46">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">register</span><span class="p" data-group-id="5252788722-47">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ -                     </span><span class="nf">spawn</span><span class="p" data-group-id="5252788722-48">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5252788722-49">[</span><span class="nf">server_node</span><span class="p" data-group-id="5252788722-50">(</span><span class="p" data-group-id="5252788722-50">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5252788722-49">]</span><span class="p" data-group-id="5252788722-48">)</span><span class="p" data-group-id="5252788722-47">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="nf">register</span><span class="p" data-group-id="3448786401-47">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ +                     </span><span class="nf">spawn</span><span class="p" data-group-id="3448786401-48">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3448786401-49">[</span><span class="nf">server_node</span><span class="p" data-group-id="3448786401-50">(</span><span class="p" data-group-id="3448786401-50">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3448786401-49">]</span><span class="p" data-group-id="3448786401-48">)</span><span class="p" data-group-id="3448786401-47">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">already_logged_on</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">logoff</span><span class="p" data-group-id="5252788722-51">(</span><span class="p" data-group-id="5252788722-51">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">logoff</span><span class="p" data-group-id="3448786401-51">(</span><span class="p" data-group-id="3448786401-51">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">logoff</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">message</span><span class="p" data-group-id="5252788722-52">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5252788722-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="5252788722-53">(</span><span class="ss">mess_client</span><span class="p" data-group-id="5252788722-53">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ +</span><span class="nf">message</span><span class="p" data-group-id="3448786401-52">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3448786401-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="3448786401-53">(</span><span class="ss">mess_client</span><span class="p" data-group-id="3448786401-53">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">not_logged_on</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5252788722-54">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5252788722-54">}</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3448786401-54">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3448786401-54">}</span><span class="p">,</span><span class="w">
│ │ │               </span><span class="ss">ok</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% The client process which runs on each user node</span><span class="w">
│ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="5252788722-55">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5252788722-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5252788722-56">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="5252788722-56">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5252788722-57">{</span><span class="nf">self</span><span class="p" data-group-id="5252788722-58">(</span><span class="p" data-group-id="5252788722-58">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5252788722-57">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">await_result</span><span class="p" data-group-id="5252788722-59">(</span><span class="p" data-group-id="5252788722-59">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="5252788722-60">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5252788722-60">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="3448786401-55">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3448786401-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3448786401-56">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="3448786401-56">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3448786401-57">{</span><span class="nf">self</span><span class="p" data-group-id="3448786401-58">(</span><span class="p" data-group-id="3448786401-58">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3448786401-57">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">await_result</span><span class="p" data-group-id="3448786401-59">(</span><span class="p" data-group-id="3448786401-59">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="3448786401-60">(</span><span class="n">Server_Node</span><span class="p" data-group-id="3448786401-60">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="5252788722-61">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5252788722-61">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="3448786401-61">(</span><span class="n">Server_Node</span><span class="p" data-group-id="3448786401-61">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">logoff</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="5252788722-62">(</span><span class="ss">normal</span><span class="p" data-group-id="5252788722-62">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5252788722-63">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5252788722-63">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="5252788722-64">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="5252788722-64">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5252788722-65">{</span><span class="nf">self</span><span class="p" data-group-id="5252788722-66">(</span><span class="p" data-group-id="5252788722-66">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5252788722-65">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">await_result</span><span class="p" data-group-id="5252788722-67">(</span><span class="p" data-group-id="5252788722-67">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5252788722-68">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5252788722-68">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5252788722-69">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5252788722-70">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5252788722-70">]</span><span class="p" data-group-id="5252788722-69">)</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="3448786401-62">(</span><span class="ss">normal</span><span class="p" data-group-id="3448786401-62">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3448786401-63">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3448786401-63">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="3448786401-64">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="3448786401-64">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3448786401-65">{</span><span class="nf">self</span><span class="p" data-group-id="3448786401-66">(</span><span class="p" data-group-id="3448786401-66">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3448786401-65">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">await_result</span><span class="p" data-group-id="3448786401-67">(</span><span class="p" data-group-id="3448786401-67">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3448786401-68">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3448786401-68">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3448786401-69">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3448786401-70">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3448786401-70">]</span><span class="p" data-group-id="3448786401-69">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="5252788722-71">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5252788722-71">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="3448786401-71">(</span><span class="n">Server_Node</span><span class="p" data-group-id="3448786401-71">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% wait for a response from the server</span><span class="w">
│ │ │ -</span><span class="nf">await_result</span><span class="p" data-group-id="5252788722-72">(</span><span class="p" data-group-id="5252788722-72">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">await_result</span><span class="p" data-group-id="3448786401-72">(</span><span class="p" data-group-id="3448786401-72">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5252788722-73">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">Why</span><span class="p" data-group-id="5252788722-73">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Stop the client</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5252788722-74">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5252788722-75">[</span><span class="n">Why</span><span class="p" data-group-id="5252788722-75">]</span><span class="p" data-group-id="5252788722-74">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="5252788722-76">(</span><span class="ss">normal</span><span class="p" data-group-id="5252788722-76">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5252788722-77">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">What</span><span class="p" data-group-id="5252788722-77">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Normal response</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5252788722-78">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5252788722-79">[</span><span class="n">What</span><span class="p" data-group-id="5252788722-79">]</span><span class="p" data-group-id="5252788722-78">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3448786401-73">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">Why</span><span class="p" data-group-id="3448786401-73">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Stop the client</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3448786401-74">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3448786401-75">[</span><span class="n">Why</span><span class="p" data-group-id="3448786401-75">]</span><span class="p" data-group-id="3448786401-74">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="3448786401-76">(</span><span class="ss">normal</span><span class="p" data-group-id="3448786401-76">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3448786401-77">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">What</span><span class="p" data-group-id="3448786401-77">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Normal response</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3448786401-78">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3448786401-79">[</span><span class="n">What</span><span class="p" data-group-id="3448786401-79">]</span><span class="p" data-group-id="3448786401-78">)</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5252788722-80">(</span><span class="s">&quot;No response from server</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5252788722-81">[</span><span class="p" data-group-id="5252788722-81">]</span><span class="p" data-group-id="5252788722-80">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="5252788722-82">(</span><span class="ss">timeout</span><span class="p" data-group-id="5252788722-82">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3448786401-80">(</span><span class="s">&quot;No response from server</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3448786401-81">[</span><span class="p" data-group-id="3448786401-81">]</span><span class="p" data-group-id="3448786401-80">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="3448786401-82">(</span><span class="ss">timeout</span><span class="p" data-group-id="3448786401-82">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The following changes are added:</p><p>The messenger server traps exits. If it receives an exit signal,
│ │ │  <code class="inline">{'EXIT',From,Reason}</code>, this means that a client process has terminated or is
│ │ │  unreachable for one of the following reasons:</p><ul><li>The user has logged off (the &quot;logoff&quot; message is removed).</li><li>The network connection to the client is broken.</li><li>The node on which the client process resides has gone down.</li><li>The client process has done some illegal operation.</li></ul><p>If an exit signal is received as above, the tuple <code class="inline">{From,Name}</code> is deleted from
│ │ │  the server's <code class="inline">User_List</code> using the <code class="inline">server_logoff</code> function. If the node on which
│ │ │  the server runs goes down, an exit signal (automatically generated by the
│ │ │  system) is sent to all of the client processes:
│ │ │  <code class="inline">{'EXIT',MessengerPID,noconnection}</code> causing all the client processes to
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/secure_coding.html
│ │ │ @@ -374,108 +374,108 @@
│ │ │  left to the supervision structure, and all unexpected <em>conditions</em> should be
│ │ │  considered errors. In brief, this is because encountering something unexpected
│ │ │  means that we have left the <em>known and tested</em> path, and continuing greatly
│ │ │  increases the risk for bugs and security issues.</p><p>Erlang code should be written as restrictively as possible, to provoke errors
│ │ │  whenever anything unexpected happens. The idea is to make the third error
│ │ │  category, program bugs, visible as a crash instead of silently continuing.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">High</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/252.html" title="">CWE-252</a>, <a href="https://cwe.mitre.org/data/definitions/253.html" title="">CWE-253</a>, <a href="https://cwe.mitre.org/data/definitions/391.html" title="">CWE-391</a>, <a href="https://cwe.mitre.org/data/definitions/392.html" title="">CWE-392</a>,
│ │ │  <a href="https://cwe.mitre.org/data/definitions/394.html" title="">CWE-394</a>, <a href="https://cwe.mitre.org/data/definitions/396.html" title="">CWE-396</a>, <a href="#owasp-a10-2025" title=""><code class="inline">A10:2025</code></a></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="k">case</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="0648747644-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0648747644-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="k">case</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="5662297548-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="5662297548-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │      </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">C</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">D</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ -</span><span class="k">case</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="0648747644-2">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0648747644-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="k">case</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="5662297548-2">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="5662297548-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │      </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">C</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="c1">%% What if operation/2 is extended to also return &#39;maybe&#39;, or someone</span><span class="w">
│ │ │      </span><span class="c1">%% misspells &#39;true&#39; as &#39;tru&#39;?</span><span class="w">
│ │ │      </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">D</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">write</span><span class="p" data-group-id="0648747644-3">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0648747644-3">)</span><span class="w">
│ │ │ +</span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">write</span><span class="p" data-group-id="5662297548-3">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5662297548-3">)</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ -</span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">write</span><span class="p" data-group-id="0648747644-4">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0648747644-4">)</span><span class="w">
│ │ │ +</span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">write</span><span class="p" data-group-id="5662297548-4">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5662297548-4">)</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="0648747644-5">(</span><span class="p" data-group-id="0648747644-6">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0648747644-6">]</span><span class="p" data-group-id="0648747644-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0648747644-7">[</span><span class="nf">bar</span><span class="p" data-group-id="0648747644-8">(</span><span class="n">First</span><span class="p" data-group-id="0648747644-8">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="0648747644-9">(</span><span class="n">Rest</span><span class="p" data-group-id="0648747644-9">)</span><span class="p" data-group-id="0648747644-7">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="0648747644-10">(</span><span class="p" data-group-id="0648747644-11">[</span><span class="p" data-group-id="0648747644-11">]</span><span class="p" data-group-id="0648747644-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0648747644-12">[</span><span class="p" data-group-id="0648747644-12">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="5662297548-5">(</span><span class="p" data-group-id="5662297548-6">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5662297548-6">]</span><span class="p" data-group-id="5662297548-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5662297548-7">[</span><span class="nf">bar</span><span class="p" data-group-id="5662297548-8">(</span><span class="n">First</span><span class="p" data-group-id="5662297548-8">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="5662297548-9">(</span><span class="n">Rest</span><span class="p" data-group-id="5662297548-9">)</span><span class="p" data-group-id="5662297548-7">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="5662297548-10">(</span><span class="p" data-group-id="5662297548-11">[</span><span class="p" data-group-id="5662297548-11">]</span><span class="p" data-group-id="5662297548-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5662297548-12">[</span><span class="p" data-group-id="5662297548-12">]</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="0648747644-13">(</span><span class="p" data-group-id="0648747644-14">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0648747644-14">]</span><span class="p" data-group-id="0648747644-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0648747644-15">[</span><span class="nf">bar</span><span class="p" data-group-id="0648747644-16">(</span><span class="n">First</span><span class="p" data-group-id="0648747644-16">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="0648747644-17">(</span><span class="n">Rest</span><span class="p" data-group-id="0648747644-17">)</span><span class="p" data-group-id="0648747644-15">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="0648747644-18">(</span><span class="p">_</span><span class="p" data-group-id="0648747644-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0648747644-19">[</span><span class="p" data-group-id="0648747644-19">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="5662297548-13">(</span><span class="p" data-group-id="5662297548-14">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5662297548-14">]</span><span class="p" data-group-id="5662297548-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5662297548-15">[</span><span class="nf">bar</span><span class="p" data-group-id="5662297548-16">(</span><span class="n">First</span><span class="p" data-group-id="5662297548-16">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="5662297548-17">(</span><span class="n">Rest</span><span class="p" data-group-id="5662297548-17">)</span><span class="p" data-group-id="5662297548-15">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="5662297548-18">(</span><span class="p">_</span><span class="p" data-group-id="5662297548-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5662297548-19">[</span><span class="p" data-group-id="5662297548-19">]</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="0648747644-20">(</span><span class="p" data-group-id="0648747644-21">&lt;&lt;</span><span class="s">&quot;foo&quot;</span><span class="p" data-group-id="0648747644-21">&gt;&gt;</span><span class="p" data-group-id="0648747644-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">foo</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="0648747644-22">(</span><span class="p" data-group-id="0648747644-23">&lt;&lt;</span><span class="s">&quot;bar&quot;</span><span class="p" data-group-id="0648747644-23">&gt;&gt;</span><span class="p" data-group-id="0648747644-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">bar</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="0648747644-24">(</span><span class="p" data-group-id="0648747644-25">&lt;&lt;</span><span class="s">&quot;quux&quot;</span><span class="p" data-group-id="0648747644-25">&gt;&gt;</span><span class="p" data-group-id="0648747644-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">quux</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="5662297548-20">(</span><span class="p" data-group-id="5662297548-21">&lt;&lt;</span><span class="s">&quot;foo&quot;</span><span class="p" data-group-id="5662297548-21">&gt;&gt;</span><span class="p" data-group-id="5662297548-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">foo</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="5662297548-22">(</span><span class="p" data-group-id="5662297548-23">&lt;&lt;</span><span class="s">&quot;bar&quot;</span><span class="p" data-group-id="5662297548-23">&gt;&gt;</span><span class="p" data-group-id="5662297548-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">bar</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="5662297548-24">(</span><span class="p" data-group-id="5662297548-25">&lt;&lt;</span><span class="s">&quot;quux&quot;</span><span class="p" data-group-id="5662297548-25">&gt;&gt;</span><span class="p" data-group-id="5662297548-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">quux</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO NOT, when set of possible atoms is known beforehand</span><span class="w">
│ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="0648747644-26">(</span><span class="n">Text</span><span class="p" data-group-id="0648747644-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">binary_to_existing_atom</span><span class="p" data-group-id="0648747644-27">(</span><span class="n">Text</span><span class="p" data-group-id="0648747644-27">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="5662297548-26">(</span><span class="n">Text</span><span class="p" data-group-id="5662297548-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">binary_to_existing_atom</span><span class="p" data-group-id="5662297548-27">(</span><span class="n">Text</span><span class="p" data-group-id="5662297548-27">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="k">try</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="0648747644-28">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0648747644-28">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0648747644-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0648747644-29">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">something</span><span class="p" data-group-id="0648747644-30">(</span><span class="n">X</span><span class="p" data-group-id="0648747644-30">)</span><span class="w">
│ │ │ +</span><span class="k">try</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="5662297548-28">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="5662297548-28">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5662297548-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="5662297548-29">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">something</span><span class="p" data-group-id="5662297548-30">(</span><span class="n">X</span><span class="p" data-group-id="5662297548-30">)</span><span class="w">
│ │ │  </span><span class="k">catch</span><span class="w">
│ │ │      </span><span class="nc">error</span><span class="p">:</span><span class="ss">specific_error</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">error</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ -</span><span class="k">try</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="0648747644-31">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0648747644-31">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0648747644-32">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0648747644-32">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">something</span><span class="p" data-group-id="0648747644-33">(</span><span class="n">X</span><span class="p" data-group-id="0648747644-33">)</span><span class="w">
│ │ │ +</span><span class="k">try</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="5662297548-31">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="5662297548-31">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5662297548-32">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="5662297548-32">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">something</span><span class="p" data-group-id="5662297548-33">(</span><span class="n">X</span><span class="p" data-group-id="5662297548-33">)</span><span class="w">
│ │ │  </span><span class="k">catch</span><span class="w">
│ │ │      </span><span class="nc">error</span><span class="p">:</span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">error</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% PREFER</span><span class="w">
│ │ │ -</span><span class="k">case</span><span class="w"> </span><span class="nf">my_filter</span><span class="p" data-group-id="0648747644-34">(</span><span class="n">List0</span><span class="p">,</span><span class="w"> </span><span class="ss">unchanged</span><span class="p" data-group-id="0648747644-34">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="k">case</span><span class="w"> </span><span class="nf">my_filter</span><span class="p" data-group-id="5662297548-34">(</span><span class="n">List0</span><span class="p">,</span><span class="w"> </span><span class="ss">unchanged</span><span class="p" data-group-id="5662297548-34">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │      </span><span class="ss">unchanged</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List0</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0648747644-35">{</span><span class="ss">changed</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="0648747644-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5662297548-35">{</span><span class="ss">changed</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="5662297548-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% AVOID</span><span class="w">
│ │ │ -</span><span class="k">case</span><span class="w"> </span><span class="nf">my_filter</span><span class="p" data-group-id="0648747644-36">(</span><span class="n">List0</span><span class="p">,</span><span class="w"> </span><span class="ss">unchanged</span><span class="p" data-group-id="0648747644-36">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="k">case</span><span class="w"> </span><span class="nf">my_filter</span><span class="p" data-group-id="5662297548-36">(</span><span class="n">List0</span><span class="p">,</span><span class="w"> </span><span class="ss">unchanged</span><span class="p" data-group-id="5662297548-36">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │      </span><span class="ss">unchanged</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List0</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="c1">%% What if a misspelled atom like &#39;uchanged&#39; is returned?</span><span class="w">
│ │ │      </span><span class="n">List</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% PREFER</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0648747644-37">[</span><span class="nf">op</span><span class="p" data-group-id="0648747644-38">(</span><span class="n">L</span><span class="p" data-group-id="0648747644-38">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="o">#</span><span class="ss">my_record</span><span class="p" data-group-id="0648747644-39">{</span><span class="p" data-group-id="0648747644-39">}</span><span class="o">=</span><span class="n">L</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">ListOfMyRecord</span><span class="p" data-group-id="0648747644-37">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5662297548-37">[</span><span class="nf">op</span><span class="p" data-group-id="5662297548-38">(</span><span class="n">L</span><span class="p" data-group-id="5662297548-38">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="o">#</span><span class="ss">my_record</span><span class="p" data-group-id="5662297548-39">{</span><span class="p" data-group-id="5662297548-39">}</span><span class="o">=</span><span class="n">L</span><span class="w"> </span><span class="o">&lt;:-</span><span class="w"> </span><span class="n">ListOfMyRecord</span><span class="p" data-group-id="5662297548-37">]</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% AVOID, this silently filters out entries that do not match #my_record{}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0648747644-40">[</span><span class="nf">op</span><span class="p" data-group-id="0648747644-41">(</span><span class="n">L</span><span class="p" data-group-id="0648747644-41">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="o">#</span><span class="ss">my_record</span><span class="p" data-group-id="0648747644-42">{</span><span class="p" data-group-id="0648747644-42">}</span><span class="o">=</span><span class="n">L</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">ListOfMyRecord</span><span class="p" data-group-id="0648747644-40">]</span></code></pre><p><a href="" id="rule-stl-002"></a></p><h4><a href="#rule-stl-002" title=""><code class="inline">STL-002</code></a> - Avoid Boolean Blindness</h4><p>Whenever boolean values have a context, prefer using more descriptive atoms to
│ │ │ +</span><span class="p" data-group-id="5662297548-40">[</span><span class="nf">op</span><span class="p" data-group-id="5662297548-41">(</span><span class="n">L</span><span class="p" data-group-id="5662297548-41">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="o">#</span><span class="ss">my_record</span><span class="p" data-group-id="5662297548-42">{</span><span class="p" data-group-id="5662297548-42">}</span><span class="o">=</span><span class="n">L</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">ListOfMyRecord</span><span class="p" data-group-id="5662297548-40">]</span></code></pre><p><a href="" id="rule-stl-002"></a></p><h4><a href="#rule-stl-002" title=""><code class="inline">STL-002</code></a> - Avoid Boolean Blindness</h4><p>Whenever boolean values have a context, prefer using more descriptive atoms to
│ │ │  express the boolean value, for example <code class="inline">initialized</code>/<code class="inline">uninitialized</code> or
│ │ │  <code class="inline">changed</code>/<code class="inline">unchanged</code>. This makes it easier to distinguish between different
│ │ │  boolean variables when many of them are used together, especially when matching
│ │ │  in function heads and the like.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Recommendation</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/628.html" title="">CWE-628</a></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="k">case</span><span class="w"> </span><span class="nf">my_filter</span><span class="p" data-group-id="9842398405-1">(</span><span class="n">List0</span><span class="p">,</span><span class="w"> </span><span class="ss">unchanged</span><span class="p" data-group-id="9842398405-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="k">case</span><span class="w"> </span><span class="nf">my_filter</span><span class="p" data-group-id="6143218280-1">(</span><span class="n">List0</span><span class="p">,</span><span class="w"> </span><span class="ss">unchanged</span><span class="p" data-group-id="6143218280-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │      </span><span class="ss">unchanged</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List0</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9842398405-2">{</span><span class="ss">changed</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9842398405-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6143218280-2">{</span><span class="ss">changed</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="6143218280-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ -</span><span class="k">case</span><span class="w"> </span><span class="nf">my_filter</span><span class="p" data-group-id="9842398405-3">(</span><span class="n">List0</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="9842398405-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="k">case</span><span class="w"> </span><span class="nf">my_filter</span><span class="p" data-group-id="6143218280-3">(</span><span class="n">List0</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="6143218280-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │      </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List0</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9842398405-4">{</span><span class="ss">true</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9842398405-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6143218280-4">{</span><span class="ss">true</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="6143218280-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">List</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p><a href="" id="rule-stl-003"></a></p><h4><a href="#rule-stl-003" title=""><code class="inline">STL-003</code></a> - Use Uppercase Names for Macros</h4><p>Macros are distinguished by a <code class="inline">?</code> prefix, so an accidental omission of the
│ │ │  prefix leaves the name there instead of applying the macro. For example,
│ │ │  <code class="inline">function_call(?my_macro, SomeArg)</code> becomes <code class="inline">function_call(my_macro, SomeArg)</code>
│ │ │  which is syntactically valid, hiding the error.</p><p>Static analysis tools can often find these issues, but a quicker way to find
│ │ │  them is to adopt the convention that all macros should be upper-case. Missing a
│ │ │  <code class="inline">?</code> will in most cases then lead to an unbound variable error or similar.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Recommendation</code></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2175253280-1">(</span><span class="n">MY_MACRO</span><span class="p">,</span><span class="w"> </span><span class="mi">65535</span><span class="p" data-group-id="2175253280-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4165318204-1">(</span><span class="n">MY_MACRO</span><span class="p">,</span><span class="w"> </span><span class="mi">65535</span><span class="p" data-group-id="4165318204-1">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2175253280-2">(</span><span class="ss">my_macro</span><span class="p">,</span><span class="w"> </span><span class="mi">65535</span><span class="p" data-group-id="2175253280-2">)</span><span class="p">.</span></code></pre><h3 id="deployment" class="section-heading">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4165318204-2">(</span><span class="ss">my_macro</span><span class="p">,</span><span class="w"> </span><span class="mi">65535</span><span class="p" data-group-id="4165318204-2">)</span><span class="p">.</span></code></pre><h3 id="deployment" class="section-heading">
│ │ │    <a href="#deployment" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Deployment</span>
│ │ │  </h3>
│ │ │  <p><a href="" id="rule-dep-001"></a></p><h4><a href="#rule-dep-001" title=""><code class="inline">DEP-001</code></a> - Do Not Expose Default Erlang Distribution on Untrusted Networks</h4><p>The builtin Erlang distribution makes it possible to easily and transparently
│ │ │  communicate between Erlang nodes. By default, communication is performed over
│ │ │ @@ -568,27 +568,27 @@
│ │ │  pervasive error handling throughout the code at large is drastically reduced,
│ │ │  and with it a large source of bugs and security issues.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Medium</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/389.html" title="">CWE-389</a>, <a href="https://cwe.mitre.org/data/definitions/544.html" title="">CWE-544</a>, <a href="https://cwe.mitre.org/data/definitions/653.html" title="">CWE-653</a>, <a href="#owasp-a10-2025" title=""><code class="inline">A10:2025</code></a></p><p><a href="" id="rule-dsg-002"></a></p><h4><a href="#rule-dsg-002" title=""><code class="inline">DSG-002</code></a> - Prefer Letting the User Decide What Warrants an Exception</h4><p>Prefer to design your interfaces so that the user decides whether an error is
│ │ │  exceptional or not, by following the <code class="inline">{ok, Result} | {error, Reason}</code>
│ │ │  convention. Generally speaking the user of an interface has more context than
│ │ │  the one implementing it, and giving them the freedom to choose through pattern
│ │ │  matching tends to result in clearer code as the handling of raised exceptions
│ │ │  is more difficult to follow.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Recommendation</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/389.html" title="">CWE-389</a>, <a href="#owasp-a10-2025" title=""><code class="inline">A10:2025</code></a></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% PREFER</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6043107163-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="6043107163-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">some_function</span><span class="p" data-group-id="6043107163-2">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="6043107163-2">)</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2448497281-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="2448497281-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">some_function</span><span class="p" data-group-id="2448497281-2">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="2448497281-2">)</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% PREFER</span><span class="w">
│ │ │ -</span><span class="k">case</span><span class="w"> </span><span class="nf">some_function</span><span class="p" data-group-id="6043107163-3">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="6043107163-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6043107163-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="6043107163-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="k">case</span><span class="w"> </span><span class="nf">some_function</span><span class="p" data-group-id="2448497281-3">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="2448497281-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2448497281-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="2448497281-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="c1">%% Happy path</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6043107163-5">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="6043107163-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2448497281-5">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="2448497281-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="c1">%% Handle it</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% AVOID</span><span class="w">
│ │ │ -</span><span class="k">try</span><span class="w"> </span><span class="nf">some_function</span><span class="p" data-group-id="6043107163-6">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="6043107163-6">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="k">try</span><span class="w"> </span><span class="nf">some_function</span><span class="p" data-group-id="2448497281-6">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="2448497281-6">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │      </span><span class="n">C</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> 
│ │ │          </span><span class="c1">%% Happy path</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="k">catch</span><span class="w">
│ │ │      </span><span class="nc">error</span><span class="p">:</span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="c1">%% Handle it</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p><a href="" id="rule-dsg-003"></a></p><h4><a href="#rule-dsg-003" title=""><code class="inline">DSG-003</code></a> - Do Not Abuse Atoms</h4><p>Atoms are designed to provide an easy way to create named constants in code.
│ │ │ @@ -610,23 +610,23 @@
│ │ │  <a href="#rule-dsg-011" title=""><code class="inline">DSG-011</code></a>) unless the API also provides some way of preventing creation of
│ │ │  atoms. For example, <a href="../../erts-17.0/doc/html/erlang.html#binary_to_term/2" title=""><code class="inline">binary_to_term/2</code></a> with the <code class="inline">safe</code> option will prevent
│ │ │  new atoms from being created. However, note that even if the <code class="inline">safe</code> option is
│ │ │  used and the data originates from an untrusted source, it still has to be
│ │ │  validated and sanitized, since it can still be harmful to the Erlang
│ │ │  application in other ways.</p><p>In general, it is best to avoid using such functions altogether on untrusted
│ │ │  data, even with the <code class="inline">safe</code> option.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">High</code></p><p>Related CWEs and OWASP risks: <a href="#cwe-770" title=""><code class="inline">CWE-770</code></a>, <a href="#owasp-api10-2023" title=""><code class="inline">API10:2023</code></a></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO, AND PREFER (see STL-001)</span><span class="w">
│ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="4002546230-1">(</span><span class="p" data-group-id="4002546230-2">&lt;&lt;</span><span class="s">&quot;foo&quot;</span><span class="p" data-group-id="4002546230-2">&gt;&gt;</span><span class="p" data-group-id="4002546230-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">foo</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="4002546230-3">(</span><span class="p" data-group-id="4002546230-4">&lt;&lt;</span><span class="s">&quot;bar&quot;</span><span class="p" data-group-id="4002546230-4">&gt;&gt;</span><span class="p" data-group-id="4002546230-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">bar</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="4002546230-5">(</span><span class="p" data-group-id="4002546230-6">&lt;&lt;</span><span class="s">&quot;quux&quot;</span><span class="p" data-group-id="4002546230-6">&gt;&gt;</span><span class="p" data-group-id="4002546230-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">quux</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="4428224004-1">(</span><span class="p" data-group-id="4428224004-2">&lt;&lt;</span><span class="s">&quot;foo&quot;</span><span class="p" data-group-id="4428224004-2">&gt;&gt;</span><span class="p" data-group-id="4428224004-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">foo</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="4428224004-3">(</span><span class="p" data-group-id="4428224004-4">&lt;&lt;</span><span class="s">&quot;bar&quot;</span><span class="p" data-group-id="4428224004-4">&gt;&gt;</span><span class="p" data-group-id="4428224004-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">bar</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="4428224004-5">(</span><span class="p" data-group-id="4428224004-6">&lt;&lt;</span><span class="s">&quot;quux&quot;</span><span class="p" data-group-id="4428224004-6">&gt;&gt;</span><span class="p" data-group-id="4428224004-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">quux</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="4002546230-7">(</span><span class="n">Text</span><span class="p" data-group-id="4002546230-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">binary_to_existing_atom</span><span class="p" data-group-id="4002546230-8">(</span><span class="n">Text</span><span class="p" data-group-id="4002546230-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="4428224004-7">(</span><span class="n">Text</span><span class="p" data-group-id="4428224004-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">binary_to_existing_atom</span><span class="p" data-group-id="4428224004-8">(</span><span class="n">Text</span><span class="p" data-group-id="4428224004-8">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ -</span><span class="nf">input_to_atom</span><span class="p" data-group-id="4002546230-9">(</span><span class="n">Text</span><span class="p" data-group-id="4002546230-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">binary_to_atom</span><span class="p" data-group-id="4002546230-10">(</span><span class="n">Text</span><span class="p" data-group-id="4002546230-10">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-dsg-004"></a></p><h4><a href="#rule-dsg-004" title=""><code class="inline">DSG-004</code></a> - Do Not Use Undocumented Functionality</h4><p>Undocumented functions or functionality must <strong>never</strong> be used. This includes
│ │ │ +</span><span class="nf">input_to_atom</span><span class="p" data-group-id="4428224004-9">(</span><span class="n">Text</span><span class="p" data-group-id="4428224004-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">binary_to_atom</span><span class="p" data-group-id="4428224004-10">(</span><span class="n">Text</span><span class="p" data-group-id="4428224004-10">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-dsg-004"></a></p><h4><a href="#rule-dsg-004" title=""><code class="inline">DSG-004</code></a> - Do Not Use Undocumented Functionality</h4><p>Undocumented functions or functionality must <strong>never</strong> be used. This includes
│ │ │  undocumented arguments to documented functions and undocumented system
│ │ │  services. Using such functionality poses a serious security risk. These
│ │ │  functions and features are intended strictly for internal use within Erlang/OTP
│ │ │  and are not supported for external use.</p><p>Merely passing the wrong arguments to these functions can cause the system to
│ │ │  behave in unexpected ways from that point on, and their behavior may change or
│ │ │  they may be removed without prior notice.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Critical</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/242.html" title="">CWE-242</a>, <a href="https://cwe.mitre.org/data/definitions/477.html" title="">CWE-477</a>, <a href="https://cwe.mitre.org/data/definitions/676.html" title="">CWE-676</a></p><p><a href="" id="rule-dsg-005"></a></p><h4><a href="#rule-dsg-005" title=""><code class="inline">DSG-005</code></a> - Do Not Use Deprecated Functionality</h4><p>When functionality is deprecated in Erlang/OTP, the documentation will
│ │ │  typically point to other or new functionality to use instead. The deprecation
│ │ │ @@ -667,28 +667,28 @@
│ │ │  them through their name instead of their process or table identifier. This
│ │ │  should be used with care, as a process or table may terminate at any time.
│ │ │  For example, if two messages are sent to a process through a registered name,
│ │ │  the second message may arrive to a newly restarted process that has not seen
│ │ │  the first, which may be significant (<a href="https://cwe.mitre.org/data/definitions/386.html" title="">CWE-386</a>).</p><p>To prevent these issues, either redesign your interface so that multiple
│ │ │  messages or lookups are not necessary, or look up the identifier from the
│ │ │  registered name and use the identifier instead.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Recommendation</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/386.html" title="">CWE-386</a></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="n">Pid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="6517849940-1">(</span><span class="ss">registered_process</span><span class="p" data-group-id="6517849940-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Pid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="1223036569-1">(</span><span class="ss">registered_process</span><span class="p" data-group-id="1223036569-1">)</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">hello</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">world</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Tid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">whereis</span><span class="p" data-group-id="6517849940-2">(</span><span class="ss">registered_table</span><span class="p" data-group-id="6517849940-2">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="6517849940-3">(</span><span class="n">Tid</span><span class="p">,</span><span class="w"> </span><span class="n">KeyA</span><span class="p" data-group-id="6517849940-3">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="6517849940-4">(</span><span class="n">Tid</span><span class="p">,</span><span class="w"> </span><span class="n">KeyB</span><span class="p" data-group-id="6517849940-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Tid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">whereis</span><span class="p" data-group-id="1223036569-2">(</span><span class="ss">registered_table</span><span class="p" data-group-id="1223036569-2">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1223036569-3">(</span><span class="n">Tid</span><span class="p">,</span><span class="w"> </span><span class="n">KeyA</span><span class="p" data-group-id="1223036569-3">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1223036569-4">(</span><span class="n">Tid</span><span class="p">,</span><span class="w"> </span><span class="n">KeyB</span><span class="p" data-group-id="1223036569-4">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │  </span><span class="ss">registered_process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">hello</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="ss">registered_process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">world</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="6517849940-5">(</span><span class="ss">registered_table</span><span class="p">,</span><span class="w"> </span><span class="n">KeyA</span><span class="p" data-group-id="6517849940-5">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="6517849940-6">(</span><span class="ss">registered_table</span><span class="p">,</span><span class="w"> </span><span class="n">KeyB</span><span class="p" data-group-id="6517849940-6">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-dsg-011"></a></p><h4><a href="#rule-dsg-011" title=""><code class="inline">DSG-011</code></a> - Only Deserialize Trusted Data</h4><p>Erlang/OTP provides various functionality that serializes and deserializes
│ │ │ +</span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1223036569-5">(</span><span class="ss">registered_table</span><span class="p">,</span><span class="w"> </span><span class="n">KeyA</span><span class="p" data-group-id="1223036569-5">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1223036569-6">(</span><span class="ss">registered_table</span><span class="p">,</span><span class="w"> </span><span class="n">KeyB</span><span class="p" data-group-id="1223036569-6">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-dsg-011"></a></p><h4><a href="#rule-dsg-011" title=""><code class="inline">DSG-011</code></a> - Only Deserialize Trusted Data</h4><p>Erlang/OTP provides various functionality that serializes and deserializes
│ │ │  general Erlang terms. Such functionality is intended to be used in a trusted
│ │ │  environment and is not suitable for communication with untrusted entities. For
│ │ │  example, you do not want to load a <a href="../../lib/mnesia-4.26/doc/html/index.html" title=""><code class="inline">mnesia</code></a> backup from an untrusted entity.
│ │ │  One issue with this being the potential for atom exhaustion, but more
│ │ │  importantly you could potentially end up with a <code class="inline">mnesia</code> table containing
│ │ │  harmful data (<a href="#cwe-502" title=""><code class="inline">CWE-502</code></a>). Other examples are <a href="../../lib/stdlib-8.0/doc/html/dets.html"><code class="inline">dets</code></a> and <a href="../../lib/kernel-11.0/doc/html/disk_log.html"><code class="inline">disk_log</code></a>.</p><p>JSON is an example of a better format to use when communicating with untrusted
│ │ │  entities. Erlang/OTP provides the <a href="../../lib/stdlib-8.0/doc/html/json.html"><code class="inline">json</code></a> module for JSON encoding/decoding.
│ │ │ @@ -705,51 +705,51 @@
│ │ │    <span class="text">Language</span>
│ │ │  </h3>
│ │ │  <p><a href="" id="rule-lng-001"></a></p><h4><a href="#rule-lng-001" title=""><code class="inline">LNG-001</code></a> - Prefer Tuples Over Exporting Variables</h4><p>For historical reasons, Erlang does not employ lexical scoping, and variables
│ │ │  defined in &quot;inner&quot; expressions are available in &quot;outer&quot; expressions that follow
│ │ │  them. Using this makes code harder to reason about, and it is preferable to
│ │ │  write your code as if Erlang has lexical scoping by returning a tuple instead.
│ │ │  There are no performance penalties for doing this.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Recommendation</code></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="nf">some_function</span><span class="p" data-group-id="6971318747-1">(</span><span class="n">State0</span><span class="p" data-group-id="6971318747-1">)</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6971318747-2">{</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="6971318747-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="6971318747-3">(</span><span class="n">State0</span><span class="p" data-group-id="6971318747-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -                      </span><span class="p" data-group-id="6971318747-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="6971318747-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                          </span><span class="p" data-group-id="6971318747-5">{</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="nf">bar</span><span class="p" data-group-id="6971318747-6">(</span><span class="n">A</span><span class="p" data-group-id="6971318747-6">)</span><span class="p" data-group-id="6971318747-5">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">some_function</span><span class="p" data-group-id="1287794382-1">(</span><span class="n">State0</span><span class="p" data-group-id="1287794382-1">)</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1287794382-2">{</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="1287794382-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="1287794382-3">(</span><span class="n">State0</span><span class="p" data-group-id="1287794382-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +                      </span><span class="p" data-group-id="1287794382-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="1287794382-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                          </span><span class="p" data-group-id="1287794382-5">{</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="nf">bar</span><span class="p" data-group-id="1287794382-6">(</span><span class="n">A</span><span class="p" data-group-id="1287794382-6">)</span><span class="p" data-group-id="1287794382-5">}</span><span class="p">;</span><span class="w">
│ │ │                        </span><span class="ss">b</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                          </span><span class="p" data-group-id="6971318747-7">{</span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">State0</span><span class="p" data-group-id="6971318747-7">}</span><span class="w">
│ │ │ +                          </span><span class="p" data-group-id="1287794382-7">{</span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">State0</span><span class="p" data-group-id="1287794382-7">}</span><span class="w">
│ │ │                    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">bar</span><span class="p" data-group-id="6971318747-8">(</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="6971318747-8">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">bar</span><span class="p" data-group-id="1287794382-8">(</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="1287794382-8">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ -</span><span class="nf">some_function</span><span class="p" data-group-id="6971318747-9">(</span><span class="n">State0</span><span class="p" data-group-id="6971318747-9">)</span><span class="w">
│ │ │ -    </span><span class="n">C</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="6971318747-10">(</span><span class="n">State0</span><span class="p" data-group-id="6971318747-10">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="6971318747-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="6971318747-11">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="n">State1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">bar</span><span class="p" data-group-id="6971318747-12">(</span><span class="n">A</span><span class="p" data-group-id="6971318747-12">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">some_function</span><span class="p" data-group-id="1287794382-9">(</span><span class="n">State0</span><span class="p" data-group-id="1287794382-9">)</span><span class="w">
│ │ │ +    </span><span class="n">C</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="1287794382-10">(</span><span class="n">State0</span><span class="p" data-group-id="1287794382-10">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="1287794382-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="1287794382-11">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                </span><span class="n">State1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">bar</span><span class="p" data-group-id="1287794382-12">(</span><span class="n">A</span><span class="p" data-group-id="1287794382-12">)</span><span class="p">,</span><span class="w">
│ │ │                  </span><span class="ss">a</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">b</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                  </span><span class="n">State1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">State0</span><span class="p">,</span><span class="w">
│ │ │                  </span><span class="ss">b</span><span class="w">
│ │ │          </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">bar</span><span class="p" data-group-id="6971318747-13">(</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="6971318747-13">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-lng-002"></a></p><h4><a href="#rule-lng-002" title=""><code class="inline">LNG-002</code></a> - Do Not Use <code class="inline">catch</code></h4><p>The legacy <code class="inline">catch</code> construct cannot distinguish between <a href="../../erts-17.0/doc/html/erlang.html#throw/1"><code class="inline">throw/1</code></a> and a normal
│ │ │ +    </span><span class="nf">bar</span><span class="p" data-group-id="1287794382-13">(</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="1287794382-13">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-lng-002"></a></p><h4><a href="#rule-lng-002" title=""><code class="inline">LNG-002</code></a> - Do Not Use <code class="inline">catch</code></h4><p>The legacy <code class="inline">catch</code> construct cannot distinguish between <a href="../../erts-17.0/doc/html/erlang.html#throw/1"><code class="inline">throw/1</code></a> and a normal
│ │ │  return, which can have very unexpected results. For instance, the
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/gen_server.html"><code class="inline">gen_server</code></a> behavior will unintentionally accept any documented return value
│ │ │  when thrown because of its use of <code class="inline">catch</code>.</p><p>Instead, the modern <a href="../../doc/system/expressions.html"><code class="inline">try ... catch ... end</code></a>
│ │ │  construct should be used.</p><p>Starting from Erlang/OTP 29, the compiler will by default raise
│ │ │  warnings for uses of the legacy <code class="inline">catch</code> construct.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Recommendation</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/253.html" title="">CWE-253</a>, <a href="https://cwe.mitre.org/data/definitions/480.html" title="">CWE-480</a>, <a href="#owasp-a10-2025" title=""><code class="inline">A10:2025</code></a></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="k">try</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="0992610723-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0992610723-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="k">try</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="1595198462-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="1595198462-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │      </span><span class="n">C</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="k">catch</span><span class="w">
│ │ │      </span><span class="nc">throw</span><span class="p">:</span><span class="n">Value</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="nc">error</span><span class="p">:</span><span class="n">Reason</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ -</span><span class="nf">case</span><span class="w"> </span><span class="p" data-group-id="0992610723-2">(</span><span class="k">catch</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="0992610723-3">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0992610723-3">)</span><span class="p" data-group-id="0992610723-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0992610723-4">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="0992610723-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">case</span><span class="w"> </span><span class="p" data-group-id="1595198462-2">(</span><span class="k">catch</span><span class="w"> </span><span class="nf">operation</span><span class="p" data-group-id="1595198462-3">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="1595198462-3">)</span><span class="p" data-group-id="1595198462-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1595198462-4">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="1595198462-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">C</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p><a href="" id="rule-lng-003"></a></p><h4><a href="#rule-lng-003" title=""><code class="inline">LNG-003</code></a> - Do Not Use the Legacy <code class="inline">and</code> and <code class="inline">or</code> Operators</h4><p>These operators have been superseded by <code class="inline">andalso</code> and <code class="inline">orelse</code>, respectively.</p><p>The legacy operators have higher precedence than in most other languages. For
│ │ │  example <code class="inline">X and Y =:= 3</code> is parsed as <code class="inline">(X and Y) =:= 3</code>. In a function body,
│ │ │  this will crash, but when used in a guard it will silently fail. It can also
│ │ │  unexpectedly corrupt the intended logic without crashing when all operands are
│ │ │ @@ -818,38 +818,38 @@
│ │ │  leaking out through a crash or core dump.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Medium</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/209.html" title="">CWE-209</a>, <a href="https://cwe.mitre.org/data/definitions/532.html" title="">CWE-532</a></p><p><a href="" id="rule-msc-005"></a></p><h4><a href="#rule-msc-005" title=""><code class="inline">MSC-005</code></a> - Treat Match Specifications As Code</h4><p>Match specifications, such as those used with ETS, are vulnerable to injection
│ │ │  attacks if they are constructed based on untrusted input.</p><p>When untrusted data is matched verbatim (such as a key), it is important to
│ │ │  wrap it in <code class="inline">{const, UntrustedData}</code> expressions. Building general queries based
│ │ │  on untrusted data should be avoided, but if that cannot be done, the query
│ │ │  should be the result of <em>parsing</em> the untrusted data into a match
│ │ │  specification (where the final shape is controlled by the programmer), rather
│ │ │  than attempting to <em>validate</em> the data before passing it in unaltered.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">High</code></p><p>Related CWEs and OWASP risks: <a href="https://cwe.mitre.org/data/definitions/74.html" title="">CWE-74</a></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="nf">find</span><span class="p" data-group-id="9211624036-1">(</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Needle</span><span class="p" data-group-id="9211624036-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match</span><span class="p" data-group-id="9211624036-2">(</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9211624036-3">{</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9211624036-4">{</span><span class="ss">const</span><span class="p">,</span><span class="w"> </span><span class="n">Needle</span><span class="p" data-group-id="9211624036-4">}</span><span class="p">,</span><span class="w"> </span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="9211624036-3">}</span><span class="p" data-group-id="9211624036-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">find</span><span class="p" data-group-id="7171497546-1">(</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Needle</span><span class="p" data-group-id="7171497546-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match</span><span class="p" data-group-id="7171497546-2">(</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7171497546-3">{</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7171497546-4">{</span><span class="ss">const</span><span class="p">,</span><span class="w"> </span><span class="n">Needle</span><span class="p" data-group-id="7171497546-4">}</span><span class="p">,</span><span class="w"> </span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="7171497546-3">}</span><span class="p" data-group-id="7171497546-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  
│ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ -</span><span class="nf">find</span><span class="p" data-group-id="9211624036-5">(</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Needle</span><span class="p" data-group-id="9211624036-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match</span><span class="p" data-group-id="9211624036-6">(</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9211624036-7">{</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Needle</span><span class="p">,</span><span class="w"> </span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="9211624036-7">}</span><span class="p" data-group-id="9211624036-6">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-msc-006"></a></p><h4><a href="#rule-msc-006" title=""><code class="inline">MSC-006</code></a> - Consider &quot;Link Following&quot; Attacks</h4><p>When operating on untrusted file paths and trying to access files through them,
│ │ │ +</span><span class="nf">find</span><span class="p" data-group-id="7171497546-5">(</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Needle</span><span class="p" data-group-id="7171497546-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match</span><span class="p" data-group-id="7171497546-6">(</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7171497546-7">{</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Needle</span><span class="p">,</span><span class="w"> </span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="7171497546-7">}</span><span class="p" data-group-id="7171497546-6">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-msc-006"></a></p><h4><a href="#rule-msc-006" title=""><code class="inline">MSC-006</code></a> - Consider &quot;Link Following&quot; Attacks</h4><p>When operating on untrusted file paths and trying to access files through them,
│ │ │  it is possible that the name does not actually identify a file, but a link
│ │ │  instead, which can in turn point at an unintended resource which is potentially
│ │ │  outside of the intended boundaries.</p><p>This can be mitigated by using <a href="../../lib/stdlib-8.0/doc/html/filelib.html#safe_relative_path/2"><code class="inline">filelib:safe_relative_path/2</code></a> to ensure that
│ │ │  the path does not escape the given bounds regardless of links. Note that it is
│ │ │  impossible to guarantee atomicity across several filesystem operations, so care
│ │ │  must be taken to avoid time-of-check time-of-use (TOCTOU) race conditions where
│ │ │  a file or symbolic link is swapped out in the middle of these operations. When
│ │ │  operating on a shared folder structure, ensure that only one entity has access
│ │ │  to said structure.</p><p><a href="#rule-priority" title="">Rule priority:</a> <code class="inline">Medium</code></p><p>Related CWEs and OWASP risks: <a href="#cwe-22" title=""><code class="inline">CWE-22</code></a>, <a href="https://cwe.mitre.org/data/definitions/59.html" title="">CWE-59</a>, <a href="https://cwe.mitre.org/data/definitions/61.html" title="">CWE-61</a></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="4295187528-1">(</span><span class="n">UntrustedPath</span><span class="p">,</span><span class="w"> </span><span class="n">Root</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4295187528-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">filelib</span><span class="p">:</span><span class="nf">safe_relative_path</span><span class="p" data-group-id="4295187528-2">(</span><span class="n">UntrustedPath</span><span class="p">,</span><span class="w"> </span><span class="n">Root</span><span class="p" data-group-id="4295187528-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="ss">unsafe</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4295187528-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">unsafe</span><span class="p" data-group-id="4295187528-3">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="n">Path</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="4295187528-4">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4295187528-5">(</span><span class="n">Root</span><span class="p">,</span><span class="w"> </span><span class="n">Path</span><span class="p" data-group-id="4295187528-5">)</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4295187528-4">)</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="4183232244-1">(</span><span class="n">UntrustedPath</span><span class="p">,</span><span class="w"> </span><span class="n">Root</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4183232244-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">filelib</span><span class="p">:</span><span class="nf">safe_relative_path</span><span class="p" data-group-id="4183232244-2">(</span><span class="n">UntrustedPath</span><span class="p">,</span><span class="w"> </span><span class="n">Root</span><span class="p" data-group-id="4183232244-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="ss">unsafe</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4183232244-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">unsafe</span><span class="p" data-group-id="4183232244-3">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="n">Path</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="4183232244-4">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4183232244-5">(</span><span class="n">Root</span><span class="p">,</span><span class="w"> </span><span class="n">Path</span><span class="p" data-group-id="4183232244-5">)</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4183232244-4">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO NOT</span><span class="w">
│ │ │ -</span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="4295187528-6">(</span><span class="n">UntrustedPath</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4295187528-6">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-msc-007"></a></p><h4><a href="#rule-msc-007" title=""><code class="inline">MSC-007</code></a> - Avoid Using Debug Functionality in Production</h4><p>Functionality that has been explicitly marked to be used only for debugging,
│ │ │ +</span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="4183232244-6">(</span><span class="n">UntrustedPath</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4183232244-6">)</span><span class="p">.</span></code></pre><p><a href="" id="rule-msc-007"></a></p><h4><a href="#rule-msc-007" title=""><code class="inline">MSC-007</code></a> - Avoid Using Debug Functionality in Production</h4><p>Functionality that has been explicitly marked to be used only for debugging,
│ │ │  such as <a href="../../erts-17.0/doc/html/erlang.html#list_to_pid/1"><code class="inline">erlang:list_to_pid/1</code></a> or the <a href="../../lib/ssl-11.6/doc/html/ssl.html#t:common_option/0"><code class="inline">keep_secrets</code></a>
│ │ │  <a href="../../lib/ssl-11.6/doc/html/index.html" title=""><code class="inline">ssl</code></a> option should not be used in production environments, except during
│ │ │  interactive debugging. Unlike with normal functionality, there are no promises
│ │ │  of API stability for debug functionality, and they may change without notice.
│ │ │  They sometimes also have adverse effects on system properties while used (such
│ │ │  as greatly increasing scheduling latency), which are acceptable during
│ │ │  testing but not in production.</p><p>In production environments, debug functionality should be considered unsafe as
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/seq_prog.html
│ │ │ @@ -136,293 +136,293 @@
│ │ │  </span><span class="mi">7</span><span class="w">
│ │ │  </span><span class="gp unselectable">2&gt; </span></code></pre><p>As shown, the Erlang shell numbers the lines that can be entered (as <code class="inline">1&gt;</code>, <code class="inline">2&gt;</code>, ...)
│ │ │  and correctly says that 2 + 5 is 7. If you make writing mistakes in the
│ │ │  shell, you can delete with the backspace key, as in most shells. There are many
│ │ │  more editing commands in the shell (see
│ │ │  <a href="../../erts-17.0/doc/html/tty.html">tty - A command line interface</a> in ERTS User's Guide).</p><p>(Notice that many line numbers given by the shell in the following examples are
│ │ │  out of sequence. This is because this tutorial was written and code-tested in
│ │ │ -separate sessions).</p><p>Here is a bit more complex calculation:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="8348507963-1">(</span><span class="mi">42</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">77</span><span class="p" data-group-id="8348507963-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">66</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │ +separate sessions).</p><p>Here is a bit more complex calculation:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="1748422300-1">(</span><span class="mi">42</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">77</span><span class="p" data-group-id="1748422300-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">66</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">2618.0</span></code></pre><p>Notice the use of brackets, the multiplication operator <code class="inline">*</code>, and the division
│ │ │  operator <code class="inline">/</code>, as in normal arithmetic (see
│ │ │  <a href="../../doc/system/expressions.html">Expressions</a>).</p><p>Press Control-C to shut down the Erlang system and the Erlang shell.</p><p>The following output is shown:</p><pre><code class="text">BREAK: (a)bort (c)ontinue (p)roc info (i)nfo (l)oaded
│ │ │         (v)ersion (k)ill (D)b-tables (d)istribution
│ │ │  a
│ │ │ -$</code></pre><p>Type <code class="inline">a</code> to leave the Erlang system.</p><p>Another way to shut down the Erlang system is by entering <a href="../../erts-17.0/doc/html/erlang.html#halt/0"><code class="inline">halt/0</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nf">halt</span><span class="p" data-group-id="9124550605-1">(</span><span class="p" data-group-id="9124550605-1">)</span><span class="p">.</span><span class="w">
│ │ │ +$</code></pre><p>Type <code class="inline">a</code> to leave the Erlang system.</p><p>Another way to shut down the Erlang system is by entering <a href="../../erts-17.0/doc/html/erlang.html#halt/0"><code class="inline">halt/0</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nf">halt</span><span class="p" data-group-id="3734316988-1">(</span><span class="p" data-group-id="3734316988-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="err">$</span></code></pre><h2 id="modules-and-functions" class="section-heading">
│ │ │    <a href="#modules-and-functions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Modules and Functions</span>
│ │ │  </h2>
│ │ │  <p>A programming language is not much use if you can only run code from the shell.
│ │ │  So here is a small Erlang program. Enter it into a file named <code class="inline">tut.erl</code> using a
│ │ │  suitable text editor. The file name <code class="inline">tut.erl</code> is important, and also that it is
│ │ │  in the same directory as the one where you started <code class="inline">erl</code>. If you are lucky, your
│ │ │  editor has an Erlang mode that makes it easier for you to enter and format your
│ │ │  code nicely (see <a href="../../lib/tools-4.2/doc/html/erlang_mode_chapter.html">The Erlang mode for Emacs</a>
│ │ │  in Tools User's Guide), but you can manage perfectly well without. Here is the
│ │ │ -code to enter:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9298771319-1">(</span><span class="ss">tut</span><span class="p" data-group-id="9298771319-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9298771319-2">(</span><span class="p" data-group-id="9298771319-3">[</span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9298771319-3">]</span><span class="p" data-group-id="9298771319-2">)</span><span class="p">.</span><span class="w">
│ │ │ +code to enter:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6464479495-1">(</span><span class="ss">tut</span><span class="p" data-group-id="6464479495-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6464479495-2">(</span><span class="p" data-group-id="6464479495-3">[</span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6464479495-3">]</span><span class="p" data-group-id="6464479495-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">double</span><span class="p" data-group-id="9298771319-4">(</span><span class="n">X</span><span class="p" data-group-id="9298771319-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">double</span><span class="p" data-group-id="6464479495-4">(</span><span class="n">X</span><span class="p" data-group-id="6464479495-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="p">.</span></code></pre><p>It is not hard to guess that this program doubles the value of numbers. The
│ │ │  first two lines of the code are described later. Let us compile the program.
│ │ │ -This can be done in an Erlang shell as follows, where <code class="inline">c</code> means compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nf">c</span><span class="p" data-group-id="5860015045-1">(</span><span class="ss">tut</span><span class="p" data-group-id="5860015045-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5860015045-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut</span><span class="p" data-group-id="5860015045-2">}</span></code></pre><p>The <code class="inline">{ok,tut}</code> means that the compilation is OK. If it says <code class="inline">error</code> it means
│ │ │ +This can be done in an Erlang shell as follows, where <code class="inline">c</code> means compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nf">c</span><span class="p" data-group-id="9923319410-1">(</span><span class="ss">tut</span><span class="p" data-group-id="9923319410-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9923319410-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut</span><span class="p" data-group-id="9923319410-2">}</span></code></pre><p>The <code class="inline">{ok,tut}</code> means that the compilation is OK. If it says <code class="inline">error</code> it means
│ │ │  that there is some mistake in the text that you entered. Additional error
│ │ │  messages give an idea about what is wrong so you can modify the text and then try
│ │ │ -to compile the program again.</p><p>Now run the program:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">tut</span><span class="p">:</span><span class="nf">double</span><span class="p" data-group-id="7475387012-1">(</span><span class="mi">10</span><span class="p" data-group-id="7475387012-1">)</span><span class="p">.</span><span class="w">
│ │ │ +to compile the program again.</p><p>Now run the program:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">tut</span><span class="p">:</span><span class="nf">double</span><span class="p" data-group-id="0630160693-1">(</span><span class="mi">10</span><span class="p" data-group-id="0630160693-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">20</span></code></pre><p>As expected, double of 10 is 20.</p><p>Now let us get back to the first two lines of the code. Erlang programs are
│ │ │  written in files. Each file contains an Erlang <em>module</em>. The first line of code
│ │ │ -in the module is the module name (see <a href="../../doc/system/modules.html">Modules</a>):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2883295264-1">(</span><span class="ss">tut</span><span class="p" data-group-id="2883295264-1">)</span><span class="p">.</span></code></pre><p>Thus, the module is called <em>tut</em>. Notice the full stop <code class="inline">.</code> at the end of the
│ │ │ +in the module is the module name (see <a href="../../doc/system/modules.html">Modules</a>):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8955631547-1">(</span><span class="ss">tut</span><span class="p" data-group-id="8955631547-1">)</span><span class="p">.</span></code></pre><p>Thus, the module is called <em>tut</em>. Notice the full stop <code class="inline">.</code> at the end of the
│ │ │  line. The files which are used to store the module must have the same name as
│ │ │  the module but with the extension <code class="inline">.erl</code>. In this case the file name is
│ │ │  <code class="inline">tut.erl</code>. When using a function in another module, the syntax
│ │ │  <code class="inline">module_name:function_name(arguments)</code> is used. So the following means call
│ │ │ -function <code class="inline">double</code> in module <code class="inline">tut</code> with argument <code class="inline">10</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">tut</span><span class="p">:</span><span class="nf">double</span><span class="p" data-group-id="3560132094-1">(</span><span class="mi">10</span><span class="p" data-group-id="3560132094-1">)</span><span class="p">.</span></code></pre><p>The second line says that the module <code class="inline">tut</code> contains a function called <code class="inline">double</code>,
│ │ │ -which takes one argument (<code class="inline">X</code> in our example):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2908687809-1">(</span><span class="p" data-group-id="2908687809-2">[</span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2908687809-2">]</span><span class="p" data-group-id="2908687809-1">)</span><span class="p">.</span></code></pre><p>The second line also says that this function can be called from outside the
│ │ │ +function <code class="inline">double</code> in module <code class="inline">tut</code> with argument <code class="inline">10</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">tut</span><span class="p">:</span><span class="nf">double</span><span class="p" data-group-id="0011295299-1">(</span><span class="mi">10</span><span class="p" data-group-id="0011295299-1">)</span><span class="p">.</span></code></pre><p>The second line says that the module <code class="inline">tut</code> contains a function called <code class="inline">double</code>,
│ │ │ +which takes one argument (<code class="inline">X</code> in our example):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3490012960-1">(</span><span class="p" data-group-id="3490012960-2">[</span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3490012960-2">]</span><span class="p" data-group-id="3490012960-1">)</span><span class="p">.</span></code></pre><p>The second line also says that this function can be called from outside the
│ │ │  module <code class="inline">tut</code>. More about this later. Again, notice the <code class="inline">.</code> at the end of the
│ │ │  line.</p><p>Now for a more complicated example, the factorial of a number. For example, the
│ │ │ -factorial of 4 is <code class="inline">4 * 3 * 2 * 1</code>, which equals 24.</p><p>Enter the following code in a file named <code class="inline">tut1.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2381583262-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="2381583262-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2381583262-2">(</span><span class="p" data-group-id="2381583262-3">[</span><span class="ss">fac</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2381583262-3">]</span><span class="p" data-group-id="2381583262-2">)</span><span class="p">.</span><span class="w">
│ │ │ +factorial of 4 is <code class="inline">4 * 3 * 2 * 1</code>, which equals 24.</p><p>Enter the following code in a file named <code class="inline">tut1.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5095061169-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="5095061169-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5095061169-2">(</span><span class="p" data-group-id="5095061169-3">[</span><span class="ss">fac</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5095061169-3">]</span><span class="p" data-group-id="5095061169-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">fac</span><span class="p" data-group-id="2381583262-4">(</span><span class="mi">1</span><span class="p" data-group-id="2381583262-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">fac</span><span class="p" data-group-id="5095061169-4">(</span><span class="mi">1</span><span class="p" data-group-id="5095061169-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">fac</span><span class="p" data-group-id="2381583262-5">(</span><span class="n">N</span><span class="p" data-group-id="2381583262-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="2381583262-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2381583262-6">)</span><span class="p">.</span></code></pre><p>So this is a module called <code class="inline">tut1</code> that contains a function called <code class="inline">fac</code>, which
│ │ │ -takes one argument, <code class="inline">N</code>.</p><p>The first part says that the factorial of 1 is 1:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fac</span><span class="p" data-group-id="3883151026-1">(</span><span class="mi">1</span><span class="p" data-group-id="3883151026-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">fac</span><span class="p" data-group-id="5095061169-5">(</span><span class="n">N</span><span class="p" data-group-id="5095061169-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="5095061169-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="5095061169-6">)</span><span class="p">.</span></code></pre><p>So this is a module called <code class="inline">tut1</code> that contains a function called <code class="inline">fac</code>, which
│ │ │ +takes one argument, <code class="inline">N</code>.</p><p>The first part says that the factorial of 1 is 1:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fac</span><span class="p" data-group-id="5123031414-1">(</span><span class="mi">1</span><span class="p" data-group-id="5123031414-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="mi">1</span><span class="p">;</span></code></pre><p>Notice that this part ends with a semicolon <code class="inline">;</code> that indicates that there is
│ │ │  more of the function <code class="inline">fac</code> to come.</p><p>The second part says that the factorial of N is N multiplied by the factorial of
│ │ │ -N - 1:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fac</span><span class="p" data-group-id="0981204242-1">(</span><span class="n">N</span><span class="p" data-group-id="0981204242-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="0981204242-2">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="0981204242-2">)</span><span class="p">.</span></code></pre><p>Notice that this part ends with a <code class="inline">.</code> saying that there are no more parts of
│ │ │ -this function.</p><p>Compile the file:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nf">c</span><span class="p" data-group-id="5921873000-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="5921873000-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5921873000-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut1</span><span class="p" data-group-id="5921873000-2">}</span></code></pre><p>And now calculate the factorial of 4.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">6&gt; </span><span class="nc">tut1</span><span class="p">:</span><span class="nf">fac</span><span class="p" data-group-id="3198442332-1">(</span><span class="mi">4</span><span class="p" data-group-id="3198442332-1">)</span><span class="p">.</span><span class="w">
│ │ │ +N - 1:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fac</span><span class="p" data-group-id="9158825089-1">(</span><span class="n">N</span><span class="p" data-group-id="9158825089-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="9158825089-2">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="9158825089-2">)</span><span class="p">.</span></code></pre><p>Notice that this part ends with a <code class="inline">.</code> saying that there are no more parts of
│ │ │ +this function.</p><p>Compile the file:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nf">c</span><span class="p" data-group-id="7057624033-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="7057624033-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7057624033-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut1</span><span class="p" data-group-id="7057624033-2">}</span></code></pre><p>And now calculate the factorial of 4.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">6&gt; </span><span class="nc">tut1</span><span class="p">:</span><span class="nf">fac</span><span class="p" data-group-id="6448202270-1">(</span><span class="mi">4</span><span class="p" data-group-id="6448202270-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">24</span></code></pre><p>Here the function <code class="inline">fac</code> in module <code class="inline">tut1</code> is called with argument <code class="inline">4</code>.</p><p>A function can have many arguments. Let us expand the module <code class="inline">tut1</code> with the
│ │ │ -function to multiply two numbers:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9253346365-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="9253346365-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9253346365-2">(</span><span class="p" data-group-id="9253346365-3">[</span><span class="ss">fac</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">mult</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9253346365-3">]</span><span class="p" data-group-id="9253346365-2">)</span><span class="p">.</span><span class="w">
│ │ │ +function to multiply two numbers:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0077115532-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="0077115532-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0077115532-2">(</span><span class="p" data-group-id="0077115532-3">[</span><span class="ss">fac</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">mult</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0077115532-3">]</span><span class="p" data-group-id="0077115532-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">fac</span><span class="p" data-group-id="9253346365-4">(</span><span class="mi">1</span><span class="p" data-group-id="9253346365-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">fac</span><span class="p" data-group-id="0077115532-4">(</span><span class="mi">1</span><span class="p" data-group-id="0077115532-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">fac</span><span class="p" data-group-id="9253346365-5">(</span><span class="n">N</span><span class="p" data-group-id="9253346365-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="9253346365-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="9253346365-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">fac</span><span class="p" data-group-id="0077115532-5">(</span><span class="n">N</span><span class="p" data-group-id="0077115532-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="0077115532-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="0077115532-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">mult</span><span class="p" data-group-id="9253346365-7">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9253346365-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">mult</span><span class="p" data-group-id="0077115532-7">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0077115532-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">Y</span><span class="p">.</span></code></pre><p>Notice that it is also required to expand the <code class="inline">-export</code> line with the
│ │ │ -information that there is another function <code class="inline">mult</code> with two arguments.</p><p>Compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">7&gt; </span><span class="nf">c</span><span class="p" data-group-id="3449662823-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="3449662823-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3449662823-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut1</span><span class="p" data-group-id="3449662823-2">}</span></code></pre><p>Try out the new function <code class="inline">mult</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">8&gt; </span><span class="nc">tut1</span><span class="p">:</span><span class="nf">mult</span><span class="p" data-group-id="0301902715-1">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0301902715-1">)</span><span class="p">.</span><span class="w">
│ │ │ +information that there is another function <code class="inline">mult</code> with two arguments.</p><p>Compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">7&gt; </span><span class="nf">c</span><span class="p" data-group-id="1990567437-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="1990567437-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1990567437-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut1</span><span class="p" data-group-id="1990567437-2">}</span></code></pre><p>Try out the new function <code class="inline">mult</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">8&gt; </span><span class="nc">tut1</span><span class="p">:</span><span class="nf">mult</span><span class="p" data-group-id="7244878979-1">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="7244878979-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">12</span></code></pre><p>In this example the numbers are integers and the arguments in the functions in
│ │ │  the code <code class="inline">N</code>, <code class="inline">X</code>, and <code class="inline">Y</code> are called variables. Variables must start with a
│ │ │  capital letter (see <a href="../../doc/system/expressions.html">Variables</a>). Examples of
│ │ │  variables are <code class="inline">Number</code>, <code class="inline">ShoeSize</code>, and <code class="inline">Age</code>.</p><h2 id="atoms" class="section-heading">
│ │ │    <a href="#atoms" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Atoms</span>
│ │ │  </h2>
│ │ │  <p>Atoms are another data type in Erlang. Atoms start with a lowercase letter (see
│ │ │  <a href="../../doc/system/data_types.html">Atom</a>), for example, <code class="inline">charles</code>, <code class="inline">centimeter</code>, and
│ │ │  <code class="inline">inch</code>. Atoms are simply names, nothing else. They are not like variables, which
│ │ │  can have a value.</p><p>Enter the next program in a file named <code class="inline">tut2.erl</code>. It can be useful for
│ │ │ -converting from inches to centimeters and conversely:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0853117006-1">(</span><span class="ss">tut2</span><span class="p" data-group-id="0853117006-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0853117006-2">(</span><span class="p" data-group-id="0853117006-3">[</span><span class="ss">convert</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0853117006-3">]</span><span class="p" data-group-id="0853117006-2">)</span><span class="p">.</span><span class="w">
│ │ │ +converting from inches to centimeters and conversely:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1997332292-1">(</span><span class="ss">tut2</span><span class="p" data-group-id="1997332292-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1997332292-2">(</span><span class="p" data-group-id="1997332292-3">[</span><span class="ss">convert</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1997332292-3">]</span><span class="p" data-group-id="1997332292-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">convert</span><span class="p" data-group-id="0853117006-4">(</span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="0853117006-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">convert</span><span class="p" data-group-id="1997332292-4">(</span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="1997332292-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">M</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">convert</span><span class="p" data-group-id="0853117006-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="ss">centimeter</span><span class="p" data-group-id="0853117006-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p">.</span></code></pre><p>Compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">9&gt; </span><span class="nf">c</span><span class="p" data-group-id="9099357557-1">(</span><span class="ss">tut2</span><span class="p" data-group-id="9099357557-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9099357557-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut2</span><span class="p" data-group-id="9099357557-2">}</span></code></pre><p>Test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">10&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="2135616935-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="2135616935-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">convert</span><span class="p" data-group-id="1997332292-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="ss">centimeter</span><span class="p" data-group-id="1997332292-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p">.</span></code></pre><p>Compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">9&gt; </span><span class="nf">c</span><span class="p" data-group-id="3554811488-1">(</span><span class="ss">tut2</span><span class="p" data-group-id="3554811488-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3554811488-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut2</span><span class="p" data-group-id="3554811488-2">}</span></code></pre><p>Test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">10&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="6860265168-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="6860265168-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">1.1811023622047243</span><span class="w">
│ │ │ -</span><span class="gp unselectable">11&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="2135616935-2">(</span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="ss">centimeter</span><span class="p" data-group-id="2135616935-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">11&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="6860265168-2">(</span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="ss">centimeter</span><span class="p" data-group-id="6860265168-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">17.78</span></code></pre><p>Notice the introduction of decimals (floating point numbers) without any
│ │ │  explanation. Hopefully you can cope with that.</p><p>Let us see what happens if something other than <code class="inline">centimeter</code> or <code class="inline">inch</code> is
│ │ │ -entered in the <code class="inline">convert</code> function:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">12&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="5285171978-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">miles</span><span class="p" data-group-id="5285171978-1">)</span><span class="p">.</span><span class="w">
│ │ │ +entered in the <code class="inline">convert</code> function:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">12&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="6288848763-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">miles</span><span class="p" data-group-id="6288848763-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no function clause matching tut2:convert(3,miles) (tut2.erl, line 4)</span></code></pre><p>The two parts of the <code class="inline">convert</code> function are called its clauses. As shown,
│ │ │  <code class="inline">miles</code> is not part of either of the clauses. The Erlang system cannot <em>match</em>
│ │ │  either of the clauses so an error message <code class="inline">function_clause</code> is returned. The
│ │ │  shell formats the error message nicely, but the error tuple is saved in the
│ │ │ -shell's history list and can be output by the shell command <code class="inline">v/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">13&gt; </span><span class="nf">v</span><span class="p" data-group-id="0914485686-1">(</span><span class="mi">12</span><span class="p" data-group-id="0914485686-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0914485686-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="0914485686-3">{</span><span class="ss">function_clause</span><span class="p">,</span><span class="p" data-group-id="0914485686-4">[</span><span class="p" data-group-id="0914485686-5">{</span><span class="ss">tut2</span><span class="p">,</span><span class="ss">convert</span><span class="p">,</span><span class="w">
│ │ │ -                                </span><span class="p" data-group-id="0914485686-6">[</span><span class="mi">3</span><span class="p">,</span><span class="ss">miles</span><span class="p" data-group-id="0914485686-6">]</span><span class="p">,</span><span class="w">
│ │ │ -                                </span><span class="p" data-group-id="0914485686-7">[</span><span class="p" data-group-id="0914485686-8">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;tut2.erl&quot;</span><span class="p" data-group-id="0914485686-8">}</span><span class="p">,</span><span class="p" data-group-id="0914485686-9">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0914485686-9">}</span><span class="p" data-group-id="0914485686-7">]</span><span class="p" data-group-id="0914485686-5">}</span><span class="p">,</span><span class="w">
│ │ │ -                          </span><span class="p" data-group-id="0914485686-10">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="w">
│ │ │ -                                    </span><span class="p" data-group-id="0914485686-11">[</span><span class="p" data-group-id="0914485686-12">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;erl_eval.erl&quot;</span><span class="p" data-group-id="0914485686-12">}</span><span class="p">,</span><span class="p" data-group-id="0914485686-13">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">677</span><span class="p" data-group-id="0914485686-13">}</span><span class="p" data-group-id="0914485686-11">]</span><span class="p" data-group-id="0914485686-10">}</span><span class="p">,</span><span class="w">
│ │ │ -                          </span><span class="p" data-group-id="0914485686-14">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="0914485686-15">[</span><span class="p" data-group-id="0914485686-16">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="0914485686-16">}</span><span class="p">,</span><span class="p" data-group-id="0914485686-17">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">687</span><span class="p" data-group-id="0914485686-17">}</span><span class="p" data-group-id="0914485686-15">]</span><span class="p" data-group-id="0914485686-14">}</span><span class="p">,</span><span class="w">
│ │ │ -                          </span><span class="p" data-group-id="0914485686-18">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="0914485686-19">[</span><span class="p" data-group-id="0914485686-20">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="0914485686-20">}</span><span class="p">,</span><span class="p" data-group-id="0914485686-21">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">642</span><span class="p" data-group-id="0914485686-21">}</span><span class="p" data-group-id="0914485686-19">]</span><span class="p" data-group-id="0914485686-18">}</span><span class="p">,</span><span class="w">
│ │ │ -                          </span><span class="p" data-group-id="0914485686-22">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_loop</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ -                                 </span><span class="p" data-group-id="0914485686-23">[</span><span class="p" data-group-id="0914485686-24">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="0914485686-24">}</span><span class="p">,</span><span class="p" data-group-id="0914485686-25">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">627</span><span class="p" data-group-id="0914485686-25">}</span><span class="p" data-group-id="0914485686-23">]</span><span class="p" data-group-id="0914485686-22">}</span><span class="p" data-group-id="0914485686-4">]</span><span class="p" data-group-id="0914485686-3">}</span><span class="p" data-group-id="0914485686-2">}</span></code></pre><h2 id="tuples" class="section-heading">
│ │ │ +shell's history list and can be output by the shell command <code class="inline">v/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">13&gt; </span><span class="nf">v</span><span class="p" data-group-id="9437265153-1">(</span><span class="mi">12</span><span class="p" data-group-id="9437265153-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9437265153-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="9437265153-3">{</span><span class="ss">function_clause</span><span class="p">,</span><span class="p" data-group-id="9437265153-4">[</span><span class="p" data-group-id="9437265153-5">{</span><span class="ss">tut2</span><span class="p">,</span><span class="ss">convert</span><span class="p">,</span><span class="w">
│ │ │ +                                </span><span class="p" data-group-id="9437265153-6">[</span><span class="mi">3</span><span class="p">,</span><span class="ss">miles</span><span class="p" data-group-id="9437265153-6">]</span><span class="p">,</span><span class="w">
│ │ │ +                                </span><span class="p" data-group-id="9437265153-7">[</span><span class="p" data-group-id="9437265153-8">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;tut2.erl&quot;</span><span class="p" data-group-id="9437265153-8">}</span><span class="p">,</span><span class="p" data-group-id="9437265153-9">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9437265153-9">}</span><span class="p" data-group-id="9437265153-7">]</span><span class="p" data-group-id="9437265153-5">}</span><span class="p">,</span><span class="w">
│ │ │ +                          </span><span class="p" data-group-id="9437265153-10">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="w">
│ │ │ +                                    </span><span class="p" data-group-id="9437265153-11">[</span><span class="p" data-group-id="9437265153-12">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;erl_eval.erl&quot;</span><span class="p" data-group-id="9437265153-12">}</span><span class="p">,</span><span class="p" data-group-id="9437265153-13">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">677</span><span class="p" data-group-id="9437265153-13">}</span><span class="p" data-group-id="9437265153-11">]</span><span class="p" data-group-id="9437265153-10">}</span><span class="p">,</span><span class="w">
│ │ │ +                          </span><span class="p" data-group-id="9437265153-14">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="9437265153-15">[</span><span class="p" data-group-id="9437265153-16">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="9437265153-16">}</span><span class="p">,</span><span class="p" data-group-id="9437265153-17">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">687</span><span class="p" data-group-id="9437265153-17">}</span><span class="p" data-group-id="9437265153-15">]</span><span class="p" data-group-id="9437265153-14">}</span><span class="p">,</span><span class="w">
│ │ │ +                          </span><span class="p" data-group-id="9437265153-18">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="9437265153-19">[</span><span class="p" data-group-id="9437265153-20">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="9437265153-20">}</span><span class="p">,</span><span class="p" data-group-id="9437265153-21">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">642</span><span class="p" data-group-id="9437265153-21">}</span><span class="p" data-group-id="9437265153-19">]</span><span class="p" data-group-id="9437265153-18">}</span><span class="p">,</span><span class="w">
│ │ │ +                          </span><span class="p" data-group-id="9437265153-22">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_loop</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ +                                 </span><span class="p" data-group-id="9437265153-23">[</span><span class="p" data-group-id="9437265153-24">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="9437265153-24">}</span><span class="p">,</span><span class="p" data-group-id="9437265153-25">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">627</span><span class="p" data-group-id="9437265153-25">}</span><span class="p" data-group-id="9437265153-23">]</span><span class="p" data-group-id="9437265153-22">}</span><span class="p" data-group-id="9437265153-4">]</span><span class="p" data-group-id="9437265153-3">}</span><span class="p" data-group-id="9437265153-2">}</span></code></pre><h2 id="tuples" class="section-heading">
│ │ │    <a href="#tuples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Tuples</span>
│ │ │  </h2>
│ │ │ -<p>Now the <code class="inline">tut2</code> program is hardly good programming style. Consider:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="0414783825-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="0414783825-1">)</span><span class="p">.</span></code></pre><p>Does this mean that 3 is in inches? Or does it mean that 3 is in centimeters and
│ │ │ +<p>Now the <code class="inline">tut2</code> program is hardly good programming style. Consider:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="5442834376-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="5442834376-1">)</span><span class="p">.</span></code></pre><p>Does this mean that 3 is in inches? Or does it mean that 3 is in centimeters and
│ │ │  is to be converted to inches? Erlang has a way to group things together to make
│ │ │  things more understandable. These are called <em>tuples</em> and are surrounded by
│ │ │  curly brackets, <code class="inline">{</code> and <code class="inline">}</code>.</p><p>So, <code class="inline">{inch,3}</code> denotes 3 inches and <code class="inline">{centimeter,5}</code> denotes 5 centimeters. Now
│ │ │  let us write a new program that converts centimeters to inches and conversely.
│ │ │ -Enter the following code in a file called <code class="inline">tut3.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9437329197-1">(</span><span class="ss">tut3</span><span class="p" data-group-id="9437329197-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9437329197-2">(</span><span class="p" data-group-id="9437329197-3">[</span><span class="ss">convert_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9437329197-3">]</span><span class="p" data-group-id="9437329197-2">)</span><span class="p">.</span><span class="w">
│ │ │ +Enter the following code in a file called <code class="inline">tut3.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5694964436-1">(</span><span class="ss">tut3</span><span class="p" data-group-id="5694964436-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5694964436-2">(</span><span class="p" data-group-id="5694964436-3">[</span><span class="ss">convert_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5694964436-3">]</span><span class="p" data-group-id="5694964436-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">convert_length</span><span class="p" data-group-id="9437329197-4">(</span><span class="p" data-group-id="9437329197-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9437329197-5">}</span><span class="p" data-group-id="9437329197-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9437329197-6">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="9437329197-6">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">convert_length</span><span class="p" data-group-id="9437329197-7">(</span><span class="p" data-group-id="9437329197-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9437329197-8">}</span><span class="p" data-group-id="9437329197-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9437329197-9">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="9437329197-9">}</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">14&gt; </span><span class="nf">c</span><span class="p" data-group-id="2008204432-1">(</span><span class="ss">tut3</span><span class="p" data-group-id="2008204432-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2008204432-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut3</span><span class="p" data-group-id="2008204432-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">15&gt; </span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="2008204432-3">(</span><span class="p" data-group-id="2008204432-4">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="2008204432-4">}</span><span class="p" data-group-id="2008204432-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2008204432-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="mf">12.7</span><span class="p" data-group-id="2008204432-5">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">16&gt; </span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="2008204432-6">(</span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="2008204432-7">(</span><span class="p" data-group-id="2008204432-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="2008204432-8">}</span><span class="p" data-group-id="2008204432-7">)</span><span class="p" data-group-id="2008204432-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2008204432-9">{</span><span class="ss">inch</span><span class="p">,</span><span class="mf">5.0</span><span class="p" data-group-id="2008204432-9">}</span></code></pre><p>Notice on line 16 that 5 inches are converted to centimeters and back again,
│ │ │ +</span><span class="nf">convert_length</span><span class="p" data-group-id="5694964436-4">(</span><span class="p" data-group-id="5694964436-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="5694964436-5">}</span><span class="p" data-group-id="5694964436-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5694964436-6">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="5694964436-6">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">convert_length</span><span class="p" data-group-id="5694964436-7">(</span><span class="p" data-group-id="5694964436-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5694964436-8">}</span><span class="p" data-group-id="5694964436-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5694964436-9">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="5694964436-9">}</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">14&gt; </span><span class="nf">c</span><span class="p" data-group-id="1711533790-1">(</span><span class="ss">tut3</span><span class="p" data-group-id="1711533790-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1711533790-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut3</span><span class="p" data-group-id="1711533790-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">15&gt; </span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="1711533790-3">(</span><span class="p" data-group-id="1711533790-4">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="1711533790-4">}</span><span class="p" data-group-id="1711533790-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1711533790-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="mf">12.7</span><span class="p" data-group-id="1711533790-5">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">16&gt; </span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="1711533790-6">(</span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="1711533790-7">(</span><span class="p" data-group-id="1711533790-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="1711533790-8">}</span><span class="p" data-group-id="1711533790-7">)</span><span class="p" data-group-id="1711533790-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1711533790-9">{</span><span class="ss">inch</span><span class="p">,</span><span class="mf">5.0</span><span class="p" data-group-id="1711533790-9">}</span></code></pre><p>Notice on line 16 that 5 inches are converted to centimeters and back again,
│ │ │  yielding the original value. This also shows that the argument to a function
│ │ │  can be the result of another function. Consider how line 16 (above) works. The
│ │ │  argument given to the function <code class="inline">{inch,5}</code> is first matched against the first
│ │ │  head clause of <code class="inline">convert_length</code>, that is, <code class="inline">convert_length({centimeter,X})</code>. It
│ │ │  can be seen that <code class="inline">{centimeter,X}</code> does not match <code class="inline">{inch,5}</code> (the head is the bit
│ │ │  before the <code class="inline">-&gt;</code>). This having failed, let us try the head of the next clause
│ │ │  that is, <code class="inline">convert_length({inch,Y})</code>. This matches, and <code class="inline">Y</code> gets the value 5.</p><p>Tuples can have more than two parts, in fact as many parts as you want, and
│ │ │  contain any valid Erlang <em>term</em>. For example, to represent the temperature of
│ │ │ -various cities of the world:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8189204472-1">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8189204472-2">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="8189204472-2">}</span><span class="p" data-group-id="8189204472-1">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8189204472-3">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8189204472-4">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="8189204472-4">}</span><span class="p" data-group-id="8189204472-3">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8189204472-5">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8189204472-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="8189204472-6">}</span><span class="p" data-group-id="8189204472-5">}</span></code></pre><p>Tuples have a fixed number of items in them. Each item in a tuple is called an
│ │ │ +various cities of the world:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3122372570-1">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3122372570-2">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="3122372570-2">}</span><span class="p" data-group-id="3122372570-1">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3122372570-3">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3122372570-4">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="3122372570-4">}</span><span class="p" data-group-id="3122372570-3">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3122372570-5">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3122372570-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="3122372570-6">}</span><span class="p" data-group-id="3122372570-5">}</span></code></pre><p>Tuples have a fixed number of items in them. Each item in a tuple is called an
│ │ │  <em>element</em>. In the tuple <code class="inline">{moscow,{c,-10}}</code>, element 1 is <code class="inline">moscow</code> and element 2
│ │ │  is <code class="inline">{c,-10}</code>. Here <code class="inline">c</code> represents Celsius and <code class="inline">f</code> Fahrenheit.</p><h2 id="lists" class="section-heading">
│ │ │    <a href="#lists" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Lists</span>
│ │ │  </h2>
│ │ │  <p>Whereas tuples group things together, it is also necessary to represent lists of
│ │ │  things. Lists in Erlang are surrounded by square brackets, <code class="inline">[</code> and <code class="inline">]</code>. For
│ │ │ -example, a list of the temperatures of various cities in the world can be:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4436743109-1">[</span><span class="p" data-group-id="4436743109-2">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4436743109-3">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="4436743109-3">}</span><span class="p" data-group-id="4436743109-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4436743109-4">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4436743109-5">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="4436743109-5">}</span><span class="p" data-group-id="4436743109-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4436743109-6">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4436743109-7">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="4436743109-7">}</span><span class="p" data-group-id="4436743109-6">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="4436743109-8">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4436743109-9">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="4436743109-9">}</span><span class="p" data-group-id="4436743109-8">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4436743109-10">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4436743109-11">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="4436743109-11">}</span><span class="p" data-group-id="4436743109-10">}</span><span class="p" data-group-id="4436743109-1">]</span></code></pre><p>Notice that this list was so long that it did not fit on one line. This does not
│ │ │ +example, a list of the temperatures of various cities in the world can be:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7169105009-1">[</span><span class="p" data-group-id="7169105009-2">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7169105009-3">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="7169105009-3">}</span><span class="p" data-group-id="7169105009-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7169105009-4">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7169105009-5">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="7169105009-5">}</span><span class="p" data-group-id="7169105009-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7169105009-6">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7169105009-7">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="7169105009-7">}</span><span class="p" data-group-id="7169105009-6">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7169105009-8">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7169105009-9">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="7169105009-9">}</span><span class="p" data-group-id="7169105009-8">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7169105009-10">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7169105009-11">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="7169105009-11">}</span><span class="p" data-group-id="7169105009-10">}</span><span class="p" data-group-id="7169105009-1">]</span></code></pre><p>Notice that this list was so long that it did not fit on one line. This does not
│ │ │  matter, Erlang allows line breaks at all &quot;sensible places&quot; but not, for example,
│ │ │  in the middle of atoms, integers, and others.</p><p>A useful way of looking at parts of lists is by using <code class="inline">|</code>. This is best
│ │ │ -explained by an example using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">17&gt; </span><span class="p" data-group-id="4479905824-1">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="n">TheRest</span><span class="p" data-group-id="4479905824-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4479905824-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="4479905824-2">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4479905824-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="4479905824-3">]</span><span class="w">
│ │ │ +explained by an example using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">17&gt; </span><span class="p" data-group-id="5915513382-1">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="n">TheRest</span><span class="p" data-group-id="5915513382-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5915513382-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5915513382-2">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5915513382-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5915513382-3">]</span><span class="w">
│ │ │  </span><span class="gp unselectable">18&gt; </span><span class="n">First</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">1</span><span class="w">
│ │ │  </span><span class="gp unselectable">19&gt; </span><span class="n">TheRest</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4479905824-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="4479905824-4">]</span></code></pre><p>To separate the first element of the list from the rest of the list, <code class="inline">|</code> is
│ │ │ -used. <code class="inline">First</code> has the value <code class="inline">1</code> and <code class="inline">TheRest</code> has the value <code class="inline">[2,3,4,5]</code>.</p><p>Another example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">20&gt; </span><span class="p" data-group-id="4419932684-1">[</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">R</span><span class="p" data-group-id="4419932684-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4419932684-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="4419932684-2">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4419932684-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="4419932684-3">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5915513382-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5915513382-4">]</span></code></pre><p>To separate the first element of the list from the rest of the list, <code class="inline">|</code> is
│ │ │ +used. <code class="inline">First</code> has the value <code class="inline">1</code> and <code class="inline">TheRest</code> has the value <code class="inline">[2,3,4,5]</code>.</p><p>Another example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">20&gt; </span><span class="p" data-group-id="6067990011-1">[</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">R</span><span class="p" data-group-id="6067990011-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6067990011-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="6067990011-2">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6067990011-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="6067990011-3">]</span><span class="w">
│ │ │  </span><span class="gp unselectable">21&gt; </span><span class="n">E1</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">1</span><span class="w">
│ │ │  </span><span class="gp unselectable">22&gt; </span><span class="n">E2</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">2</span><span class="w">
│ │ │  </span><span class="gp unselectable">23&gt; </span><span class="n">R</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4419932684-4">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="4419932684-4">]</span></code></pre><p>Here you see the use of <code class="inline">|</code> to get the first two elements from the list. If you
│ │ │ +</span><span class="p" data-group-id="6067990011-4">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="6067990011-4">]</span></code></pre><p>Here you see the use of <code class="inline">|</code> to get the first two elements from the list. If you
│ │ │  try to get more elements from the list than there are elements in the list, an
│ │ │  error is returned. Notice also the special case of the list with no elements,
│ │ │ -<code class="inline">[]</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">24&gt; </span><span class="p" data-group-id="9642987321-1">[</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="9642987321-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9642987321-2">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="9642987321-2">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9642987321-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9642987321-3">]</span><span class="w">
│ │ │ +<code class="inline">[]</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">24&gt; </span><span class="p" data-group-id="2495169367-1">[</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="2495169367-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2495169367-2">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="2495169367-2">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2495169367-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2495169367-3">]</span><span class="w">
│ │ │  </span><span class="gp unselectable">25&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">1</span><span class="w">
│ │ │  </span><span class="gp unselectable">26&gt; </span><span class="n">B</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">2</span><span class="w">
│ │ │  </span><span class="gp unselectable">27&gt; </span><span class="n">C</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9642987321-4">[</span><span class="p" data-group-id="9642987321-4">]</span></code></pre><p>In the previous examples, new variable names are used, instead of reusing the
│ │ │ +</span><span class="p" data-group-id="2495169367-4">[</span><span class="p" data-group-id="2495169367-4">]</span></code></pre><p>In the previous examples, new variable names are used, instead of reusing the
│ │ │  old ones: <code class="inline">First</code>, <code class="inline">TheRest</code>, <code class="inline">E1</code>, <code class="inline">E2</code>, <code class="inline">R</code>, <code class="inline">A</code>, <code class="inline">B</code>, and <code class="inline">C</code>. The reason for
│ │ │  this is that a variable can only be given a value once in its context (scope).
│ │ │  More about this later.</p><p>The following example shows how to find the length of a list. Enter the
│ │ │ -following code in a file named <code class="inline">tut4.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9184558214-1">(</span><span class="ss">tut4</span><span class="p" data-group-id="9184558214-1">)</span><span class="p">.</span><span class="w">
│ │ │ +following code in a file named <code class="inline">tut4.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6071881260-1">(</span><span class="ss">tut4</span><span class="p" data-group-id="6071881260-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9184558214-2">(</span><span class="p" data-group-id="9184558214-3">[</span><span class="ss">list_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9184558214-3">]</span><span class="p" data-group-id="9184558214-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6071881260-2">(</span><span class="p" data-group-id="6071881260-3">[</span><span class="ss">list_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6071881260-3">]</span><span class="p" data-group-id="6071881260-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">list_length</span><span class="p" data-group-id="9184558214-4">(</span><span class="p" data-group-id="9184558214-5">[</span><span class="p" data-group-id="9184558214-5">]</span><span class="p" data-group-id="9184558214-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">list_length</span><span class="p" data-group-id="6071881260-4">(</span><span class="p" data-group-id="6071881260-5">[</span><span class="p" data-group-id="6071881260-5">]</span><span class="p" data-group-id="6071881260-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="mi">0</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">list_length</span><span class="p" data-group-id="9184558214-6">(</span><span class="p" data-group-id="9184558214-7">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9184558214-7">]</span><span class="p" data-group-id="9184558214-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">list_length</span><span class="p" data-group-id="9184558214-8">(</span><span class="n">Rest</span><span class="p" data-group-id="9184558214-8">)</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">28&gt; </span><span class="nf">c</span><span class="p" data-group-id="6807425318-1">(</span><span class="ss">tut4</span><span class="p" data-group-id="6807425318-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6807425318-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut4</span><span class="p" data-group-id="6807425318-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">29&gt; </span><span class="nc">tut4</span><span class="p">:</span><span class="nf">list_length</span><span class="p" data-group-id="6807425318-3">(</span><span class="p" data-group-id="6807425318-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="6807425318-4">]</span><span class="p" data-group-id="6807425318-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">7</span></code></pre><p>Explanation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_length</span><span class="p" data-group-id="1840953429-1">(</span><span class="p" data-group-id="1840953429-2">[</span><span class="p" data-group-id="1840953429-2">]</span><span class="p" data-group-id="1840953429-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="mi">0</span><span class="p">;</span></code></pre><p>The length of an empty list is obviously 0.</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_length</span><span class="p" data-group-id="5769040096-1">(</span><span class="p" data-group-id="5769040096-2">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5769040096-2">]</span><span class="p" data-group-id="5769040096-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">list_length</span><span class="p" data-group-id="5769040096-3">(</span><span class="n">Rest</span><span class="p" data-group-id="5769040096-3">)</span><span class="p">.</span></code></pre><p>The length of a list with the first element <code class="inline">First</code> and the remaining elements
│ │ │ +</span><span class="nf">list_length</span><span class="p" data-group-id="6071881260-6">(</span><span class="p" data-group-id="6071881260-7">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="6071881260-7">]</span><span class="p" data-group-id="6071881260-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">list_length</span><span class="p" data-group-id="6071881260-8">(</span><span class="n">Rest</span><span class="p" data-group-id="6071881260-8">)</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">28&gt; </span><span class="nf">c</span><span class="p" data-group-id="5702544924-1">(</span><span class="ss">tut4</span><span class="p" data-group-id="5702544924-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5702544924-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut4</span><span class="p" data-group-id="5702544924-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">29&gt; </span><span class="nc">tut4</span><span class="p">:</span><span class="nf">list_length</span><span class="p" data-group-id="5702544924-3">(</span><span class="p" data-group-id="5702544924-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="5702544924-4">]</span><span class="p" data-group-id="5702544924-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">7</span></code></pre><p>Explanation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_length</span><span class="p" data-group-id="0873199787-1">(</span><span class="p" data-group-id="0873199787-2">[</span><span class="p" data-group-id="0873199787-2">]</span><span class="p" data-group-id="0873199787-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="mi">0</span><span class="p">;</span></code></pre><p>The length of an empty list is obviously 0.</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_length</span><span class="p" data-group-id="5032739946-1">(</span><span class="p" data-group-id="5032739946-2">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5032739946-2">]</span><span class="p" data-group-id="5032739946-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">list_length</span><span class="p" data-group-id="5032739946-3">(</span><span class="n">Rest</span><span class="p" data-group-id="5032739946-3">)</span><span class="p">.</span></code></pre><p>The length of a list with the first element <code class="inline">First</code> and the remaining elements
│ │ │  <code class="inline">Rest</code> is 1 + the length of <code class="inline">Rest</code>.</p><p>(Advanced readers only: This is not tail recursive, there is a better way to
│ │ │  write this function.)</p><p>In general, tuples are used where &quot;records&quot; or &quot;structs&quot; are used in other
│ │ │  languages. Also, lists are used when representing things with varying sizes,
│ │ │  that is, where linked lists are used in other languages.</p><p>Erlang does not have a string data type. Instead, strings can be represented by
│ │ │  lists of Unicode characters. This implies for example that the list <code class="inline">[97,98,99]</code>
│ │ │  is equivalent to <code class="inline">&quot;abc&quot;</code>. The Erlang shell is &quot;clever&quot; and guesses what list you
│ │ │ -mean and outputs it in what it thinks is the most appropriate form, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">30&gt; </span><span class="p" data-group-id="8528160580-1">[</span><span class="mi">97</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="8528160580-1">]</span><span class="p">.</span><span class="w">
│ │ │ +mean and outputs it in what it thinks is the most appropriate form, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">30&gt; </span><span class="p" data-group-id="3450516314-1">[</span><span class="mi">97</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="3450516314-1">]</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;abc&quot;</span></code></pre><h2 id="maps" class="section-heading">
│ │ │    <a href="#maps" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Maps</span>
│ │ │  </h2>
│ │ │  <p>Maps are a set of key to value associations. These associations are encapsulated
│ │ │ -with <code class="inline">#{</code> and <code class="inline">}</code>. To create an association from <code class="inline">&quot;key&quot;</code> to value <code class="inline">42</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="5060531122-1">#{</span><span class="w"> </span><span class="s">&quot;key&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p" data-group-id="5060531122-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5060531122-2">#{</span><span class="s">&quot;key&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="5060531122-2">}</span></code></pre><p>Let us jump straight into the deep end with an example using some interesting
│ │ │ +with <code class="inline">#{</code> and <code class="inline">}</code>. To create an association from <code class="inline">&quot;key&quot;</code> to value <code class="inline">42</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="0905055145-1">#{</span><span class="w"> </span><span class="s">&quot;key&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p" data-group-id="0905055145-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0905055145-2">#{</span><span class="s">&quot;key&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="0905055145-2">}</span></code></pre><p>Let us jump straight into the deep end with an example using some interesting
│ │ │  features.</p><p>The following example shows how to calculate alpha blending using maps to
│ │ │ -reference color and alpha channels. Enter the code in a file named <code class="inline">color.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0081742142-1">(</span><span class="ss">color</span><span class="p" data-group-id="0081742142-1">)</span><span class="p">.</span><span class="w">
│ │ │ +reference color and alpha channels. Enter the code in a file named <code class="inline">color.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0163323821-1">(</span><span class="ss">color</span><span class="p" data-group-id="0163323821-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0081742142-2">(</span><span class="p" data-group-id="0081742142-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="ss">blend</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0081742142-3">]</span><span class="p" data-group-id="0081742142-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0163323821-2">(</span><span class="p" data-group-id="0163323821-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="ss">blend</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0163323821-3">]</span><span class="p" data-group-id="0163323821-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0081742142-4">(</span><span class="nf">is_channel</span><span class="p" data-group-id="0081742142-5">(</span><span class="n">V</span><span class="p" data-group-id="0081742142-5">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0081742142-6">(</span><span class="nf">is_float</span><span class="p" data-group-id="0081742142-7">(</span><span class="n">V</span><span class="p" data-group-id="0081742142-7">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="0081742142-6">)</span><span class="p" data-group-id="0081742142-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0163323821-4">(</span><span class="nf">is_channel</span><span class="p" data-group-id="0163323821-5">(</span><span class="n">V</span><span class="p" data-group-id="0163323821-5">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0163323821-6">(</span><span class="nf">is_float</span><span class="p" data-group-id="0163323821-7">(</span><span class="n">V</span><span class="p" data-group-id="0163323821-7">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="0163323821-6">)</span><span class="p" data-group-id="0163323821-4">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">new</span><span class="p" data-group-id="0081742142-8">(</span><span class="n">R</span><span class="p">,</span><span class="n">G</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">A</span><span class="p" data-group-id="0081742142-8">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="0081742142-9">(</span><span class="n">R</span><span class="p" data-group-id="0081742142-9">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="0081742142-10">(</span><span class="n">G</span><span class="p" data-group-id="0081742142-10">)</span><span class="p">,</span><span class="w">
│ │ │ -                  </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="0081742142-11">(</span><span class="n">B</span><span class="p" data-group-id="0081742142-11">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="0081742142-12">(</span><span class="n">A</span><span class="p" data-group-id="0081742142-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0081742142-13">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">G</span><span class="p">,</span><span class="w"> </span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="0081742142-13">}</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">blend</span><span class="p" data-group-id="0081742142-14">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="0081742142-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">blend</span><span class="p" data-group-id="0081742142-15">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="nf">alpha</span><span class="p" data-group-id="0081742142-16">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="0081742142-16">)</span><span class="p" data-group-id="0081742142-15">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">blend</span><span class="p" data-group-id="0081742142-17">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="n">Alpha</span><span class="p" data-group-id="0081742142-17">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Alpha</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Dst</span><span class="p" data-group-id="0081742142-18">#{</span><span class="w">
│ │ │ -        </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="nf">red</span><span class="p" data-group-id="0081742142-19">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="0081742142-19">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="nf">green</span><span class="p" data-group-id="0081742142-20">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="0081742142-20">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="nf">blue</span><span class="p" data-group-id="0081742142-21">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="0081742142-21">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">new</span><span class="p" data-group-id="0163323821-8">(</span><span class="n">R</span><span class="p">,</span><span class="n">G</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">A</span><span class="p" data-group-id="0163323821-8">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="0163323821-9">(</span><span class="n">R</span><span class="p" data-group-id="0163323821-9">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="0163323821-10">(</span><span class="n">G</span><span class="p" data-group-id="0163323821-10">)</span><span class="p">,</span><span class="w">
│ │ │ +                  </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="0163323821-11">(</span><span class="n">B</span><span class="p" data-group-id="0163323821-11">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="0163323821-12">(</span><span class="n">A</span><span class="p" data-group-id="0163323821-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0163323821-13">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">G</span><span class="p">,</span><span class="w"> </span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="0163323821-13">}</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">blend</span><span class="p" data-group-id="0163323821-14">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="0163323821-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">blend</span><span class="p" data-group-id="0163323821-15">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="nf">alpha</span><span class="p" data-group-id="0163323821-16">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="0163323821-16">)</span><span class="p" data-group-id="0163323821-15">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">blend</span><span class="p" data-group-id="0163323821-17">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="n">Alpha</span><span class="p" data-group-id="0163323821-17">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Alpha</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Dst</span><span class="p" data-group-id="0163323821-18">#{</span><span class="w">
│ │ │ +        </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="nf">red</span><span class="p" data-group-id="0163323821-19">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="0163323821-19">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="nf">green</span><span class="p" data-group-id="0163323821-20">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="0163323821-20">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="nf">blue</span><span class="p" data-group-id="0163323821-21">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="0163323821-21">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Alpha</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0081742142-18">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">blend</span><span class="p" data-group-id="0081742142-22">(</span><span class="p">_</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0081742142-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Dst</span><span class="p" data-group-id="0081742142-23">#{</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0163323821-18">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">blend</span><span class="p" data-group-id="0163323821-22">(</span><span class="p">_</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0163323821-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Dst</span><span class="p" data-group-id="0163323821-23">#{</span><span class="w">
│ │ │          </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="mf">0.0</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mf">0.0</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="mf">0.0</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mf">0.0</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0081742142-23">}</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0163323821-23">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">alpha</span><span class="p" data-group-id="0081742142-24">(</span><span class="p" data-group-id="0081742142-25">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0081742142-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0081742142-26">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="0081742142-26">}</span><span class="p" data-group-id="0081742142-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="0081742142-27">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0081742142-27">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">alpha</span><span class="p" data-group-id="0163323821-24">(</span><span class="p" data-group-id="0163323821-25">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0163323821-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0163323821-26">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="0163323821-26">}</span><span class="p" data-group-id="0163323821-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="0163323821-27">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0163323821-27">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">red</span><span class="p" data-group-id="0081742142-28">(</span><span class="p" data-group-id="0081742142-29">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0081742142-29">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0081742142-30">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="0081742142-30">}</span><span class="p" data-group-id="0081742142-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="0081742142-31">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0081742142-31">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">green</span><span class="p" data-group-id="0081742142-32">(</span><span class="p" data-group-id="0081742142-33">#{</span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0081742142-33">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0081742142-34">#{</span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="0081742142-34">}</span><span class="p" data-group-id="0081742142-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="0081742142-35">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0081742142-35">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">blue</span><span class="p" data-group-id="0081742142-36">(</span><span class="p" data-group-id="0081742142-37">#{</span><span class="ss">blue</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0081742142-37">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0081742142-38">#{</span><span class="ss">blue</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="0081742142-38">}</span><span class="p" data-group-id="0081742142-36">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="0081742142-39">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0081742142-39">)</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">c</span><span class="p" data-group-id="0717188505-1">(</span><span class="ss">color</span><span class="p" data-group-id="0717188505-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0717188505-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">color</span><span class="p" data-group-id="0717188505-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">C1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">color</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="0717188505-3">(</span><span class="mf">0.3</span><span class="p">,</span><span class="mf">0.4</span><span class="p">,</span><span class="mf">0.5</span><span class="p">,</span><span class="mf">1.0</span><span class="p" data-group-id="0717188505-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0717188505-4">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.5</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.4</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p" data-group-id="0717188505-4">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="n">C2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">color</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="0717188505-5">(</span><span class="mf">1.0</span><span class="p">,</span><span class="mf">0.8</span><span class="p">,</span><span class="mf">0.1</span><span class="p">,</span><span class="mf">0.3</span><span class="p" data-group-id="0717188505-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0717188505-6">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.1</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.8</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="0717188505-6">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">color</span><span class="p">:</span><span class="nf">blend</span><span class="p" data-group-id="0717188505-7">(</span><span class="n">C1</span><span class="p">,</span><span class="n">C2</span><span class="p" data-group-id="0717188505-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0717188505-8">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.5</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.4</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p" data-group-id="0717188505-8">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">&gt; </span><span class="nc">color</span><span class="p">:</span><span class="nf">blend</span><span class="p" data-group-id="0717188505-9">(</span><span class="n">C2</span><span class="p">,</span><span class="n">C1</span><span class="p" data-group-id="0717188505-9">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0717188505-10">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.38</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.52</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.51</span><span class="p" data-group-id="0717188505-10">}</span></code></pre><p>This example warrants some explanation:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4023626734-1">(</span><span class="nf">is_channel</span><span class="p" data-group-id="4023626734-2">(</span><span class="n">V</span><span class="p" data-group-id="4023626734-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4023626734-3">(</span><span class="nf">is_float</span><span class="p" data-group-id="4023626734-4">(</span><span class="n">V</span><span class="p" data-group-id="4023626734-4">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="4023626734-3">)</span><span class="p" data-group-id="4023626734-1">)</span><span class="p">.</span></code></pre><p>First a macro <code class="inline">is_channel</code> is defined to help with the guard tests. This is only
│ │ │ +</span><span class="nf">red</span><span class="p" data-group-id="0163323821-28">(</span><span class="p" data-group-id="0163323821-29">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0163323821-29">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0163323821-30">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="0163323821-30">}</span><span class="p" data-group-id="0163323821-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="0163323821-31">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0163323821-31">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">green</span><span class="p" data-group-id="0163323821-32">(</span><span class="p" data-group-id="0163323821-33">#{</span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0163323821-33">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0163323821-34">#{</span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="0163323821-34">}</span><span class="p" data-group-id="0163323821-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="0163323821-35">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0163323821-35">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">blue</span><span class="p" data-group-id="0163323821-36">(</span><span class="p" data-group-id="0163323821-37">#{</span><span class="ss">blue</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0163323821-37">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0163323821-38">#{</span><span class="ss">blue</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="0163323821-38">}</span><span class="p" data-group-id="0163323821-36">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="0163323821-39">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0163323821-39">)</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">c</span><span class="p" data-group-id="6211207273-1">(</span><span class="ss">color</span><span class="p" data-group-id="6211207273-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6211207273-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">color</span><span class="p" data-group-id="6211207273-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">C1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">color</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="6211207273-3">(</span><span class="mf">0.3</span><span class="p">,</span><span class="mf">0.4</span><span class="p">,</span><span class="mf">0.5</span><span class="p">,</span><span class="mf">1.0</span><span class="p" data-group-id="6211207273-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6211207273-4">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.5</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.4</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p" data-group-id="6211207273-4">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="n">C2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">color</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="6211207273-5">(</span><span class="mf">1.0</span><span class="p">,</span><span class="mf">0.8</span><span class="p">,</span><span class="mf">0.1</span><span class="p">,</span><span class="mf">0.3</span><span class="p" data-group-id="6211207273-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6211207273-6">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.1</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.8</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="6211207273-6">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">color</span><span class="p">:</span><span class="nf">blend</span><span class="p" data-group-id="6211207273-7">(</span><span class="n">C1</span><span class="p">,</span><span class="n">C2</span><span class="p" data-group-id="6211207273-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6211207273-8">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.5</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.4</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p" data-group-id="6211207273-8">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">&gt; </span><span class="nc">color</span><span class="p">:</span><span class="nf">blend</span><span class="p" data-group-id="6211207273-9">(</span><span class="n">C2</span><span class="p">,</span><span class="n">C1</span><span class="p" data-group-id="6211207273-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6211207273-10">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.38</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.52</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.51</span><span class="p" data-group-id="6211207273-10">}</span></code></pre><p>This example warrants some explanation:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6119397079-1">(</span><span class="nf">is_channel</span><span class="p" data-group-id="6119397079-2">(</span><span class="n">V</span><span class="p" data-group-id="6119397079-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6119397079-3">(</span><span class="nf">is_float</span><span class="p" data-group-id="6119397079-4">(</span><span class="n">V</span><span class="p" data-group-id="6119397079-4">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="6119397079-3">)</span><span class="p" data-group-id="6119397079-1">)</span><span class="p">.</span></code></pre><p>First a macro <code class="inline">is_channel</code> is defined to help with the guard tests. This is only
│ │ │  here for convenience and to reduce syntax cluttering. For more information about
│ │ │ -macros, see <a href="../../doc/system/macros.html">The Preprocessor</a>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">new</span><span class="p" data-group-id="0388813332-1">(</span><span class="n">R</span><span class="p">,</span><span class="n">G</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">A</span><span class="p" data-group-id="0388813332-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="0388813332-2">(</span><span class="n">R</span><span class="p" data-group-id="0388813332-2">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="0388813332-3">(</span><span class="n">G</span><span class="p" data-group-id="0388813332-3">)</span><span class="p">,</span><span class="w">
│ │ │ -                  </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="0388813332-4">(</span><span class="n">B</span><span class="p" data-group-id="0388813332-4">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="0388813332-5">(</span><span class="n">A</span><span class="p" data-group-id="0388813332-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0388813332-6">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">G</span><span class="p">,</span><span class="w"> </span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="0388813332-6">}</span><span class="p">.</span></code></pre><p>The function <code class="inline">new/4</code> creates a new map term and lets the keys <code class="inline">red</code>, <code class="inline">green</code>,
│ │ │ +macros, see <a href="../../doc/system/macros.html">The Preprocessor</a>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">new</span><span class="p" data-group-id="3704787032-1">(</span><span class="n">R</span><span class="p">,</span><span class="n">G</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">A</span><span class="p" data-group-id="3704787032-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="3704787032-2">(</span><span class="n">R</span><span class="p" data-group-id="3704787032-2">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="3704787032-3">(</span><span class="n">G</span><span class="p" data-group-id="3704787032-3">)</span><span class="p">,</span><span class="w">
│ │ │ +                  </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="3704787032-4">(</span><span class="n">B</span><span class="p" data-group-id="3704787032-4">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="3704787032-5">(</span><span class="n">A</span><span class="p" data-group-id="3704787032-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3704787032-6">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">G</span><span class="p">,</span><span class="w"> </span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="3704787032-6">}</span><span class="p">.</span></code></pre><p>The function <code class="inline">new/4</code> creates a new map term and lets the keys <code class="inline">red</code>, <code class="inline">green</code>,
│ │ │  <code class="inline">blue</code>, and <code class="inline">alpha</code> be associated with an initial value. In this case, only
│ │ │  float values between and including 0.0 and 1.0 are allowed, as ensured by the
│ │ │  <code class="inline">?is_channel/1</code> macro for each argument. Only the <code class="inline">=&gt;</code> operator is allowed when
│ │ │  creating a new map.</p><p>By calling <code class="inline">blend/2</code> on any color term created by <code class="inline">new/4</code>, the resulting color
│ │ │ -can be calculated as determined by the two map terms.</p><p>The first thing <code class="inline">blend/2</code> does is to calculate the resulting alpha channel:</p><pre><code class="makeup erlang" translate="no"><span class="nf">alpha</span><span class="p" data-group-id="5710978507-1">(</span><span class="p" data-group-id="5710978507-2">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="5710978507-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5710978507-3">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="5710978507-3">}</span><span class="p" data-group-id="5710978507-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="5710978507-4">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="5710978507-4">)</span><span class="p">.</span></code></pre><p>The value associated with key <code class="inline">alpha</code> is fetched for both arguments using the
│ │ │ +can be calculated as determined by the two map terms.</p><p>The first thing <code class="inline">blend/2</code> does is to calculate the resulting alpha channel:</p><pre><code class="makeup erlang" translate="no"><span class="nf">alpha</span><span class="p" data-group-id="2541444879-1">(</span><span class="p" data-group-id="2541444879-2">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="2541444879-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2541444879-3">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="2541444879-3">}</span><span class="p" data-group-id="2541444879-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="2541444879-4">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="2541444879-4">)</span><span class="p">.</span></code></pre><p>The value associated with key <code class="inline">alpha</code> is fetched for both arguments using the
│ │ │  <code class="inline">:=</code> operator. The other keys in the map are ignored, only the key <code class="inline">alpha</code> is
│ │ │ -required and checked for.</p><p>This is also the case for functions <code class="inline">red/2</code>, <code class="inline">blue/2</code>, and <code class="inline">green/2</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">red</span><span class="p" data-group-id="7890825884-1">(</span><span class="p" data-group-id="7890825884-2">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="7890825884-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7890825884-3">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="7890825884-3">}</span><span class="p" data-group-id="7890825884-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="7890825884-4">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="7890825884-4">)</span><span class="p">.</span></code></pre><p>The difference here is that a check is made for two keys in each map argument.
│ │ │ -The other keys are ignored.</p><p>Finally, let us return the resulting color in <code class="inline">blend/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">blend</span><span class="p" data-group-id="4063246570-1">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="n">Alpha</span><span class="p" data-group-id="4063246570-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Alpha</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Dst</span><span class="p" data-group-id="4063246570-2">#{</span><span class="w">
│ │ │ -        </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="nf">red</span><span class="p" data-group-id="4063246570-3">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="4063246570-3">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="nf">green</span><span class="p" data-group-id="4063246570-4">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="4063246570-4">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="nf">blue</span><span class="p" data-group-id="4063246570-5">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="4063246570-5">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ +required and checked for.</p><p>This is also the case for functions <code class="inline">red/2</code>, <code class="inline">blue/2</code>, and <code class="inline">green/2</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">red</span><span class="p" data-group-id="8773962444-1">(</span><span class="p" data-group-id="8773962444-2">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8773962444-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8773962444-3">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="8773962444-3">}</span><span class="p" data-group-id="8773962444-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="8773962444-4">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8773962444-4">)</span><span class="p">.</span></code></pre><p>The difference here is that a check is made for two keys in each map argument.
│ │ │ +The other keys are ignored.</p><p>Finally, let us return the resulting color in <code class="inline">blend/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">blend</span><span class="p" data-group-id="8666281063-1">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="n">Alpha</span><span class="p" data-group-id="8666281063-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Alpha</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Dst</span><span class="p" data-group-id="8666281063-2">#{</span><span class="w">
│ │ │ +        </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="nf">red</span><span class="p" data-group-id="8666281063-3">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="8666281063-3">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="nf">green</span><span class="p" data-group-id="8666281063-4">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="8666281063-4">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="nf">blue</span><span class="p" data-group-id="8666281063-5">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="8666281063-5">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Alpha</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4063246570-2">}</span><span class="p">;</span></code></pre><p>The <code class="inline">Dst</code> map is updated with new channel values. The syntax for updating an
│ │ │ +    </span><span class="p" data-group-id="8666281063-2">}</span><span class="p">;</span></code></pre><p>The <code class="inline">Dst</code> map is updated with new channel values. The syntax for updating an
│ │ │  existing key with a new value is with the <code class="inline">:=</code> operator.</p><h2 id="standard-modules-and-manual-pages" class="section-heading">
│ │ │    <a href="#standard-modules-and-manual-pages" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Standard Modules and Manual Pages</span>
│ │ │  </h2>
│ │ │  <p>Erlang has many standard modules to help you do things. For example, the module
│ │ │ @@ -442,24 +442,24 @@
│ │ │    <a href="#writing-output-to-a-terminal" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Writing Output to a Terminal</span>
│ │ │  </h2>
│ │ │  <p>It is nice to be able to do formatted output in examples, so the next example
│ │ │  shows a simple way to use the <a href="../../lib/stdlib-8.0/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> function. Like all other exported
│ │ │ -functions, you can test the <a href="../../lib/stdlib-8.0/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> function in the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">31&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0857512522-1">(</span><span class="s">&quot;hello world</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0857512522-2">[</span><span class="p" data-group-id="0857512522-2">]</span><span class="p" data-group-id="0857512522-1">)</span><span class="p">.</span><span class="w">
│ │ │ +functions, you can test the <a href="../../lib/stdlib-8.0/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> function in the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">31&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5197054408-1">(</span><span class="s">&quot;hello world</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5197054408-2">[</span><span class="p" data-group-id="5197054408-2">]</span><span class="p" data-group-id="5197054408-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="w"> </span><span class="ss">world</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">32&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0857512522-3">(</span><span class="s">&quot;this outputs one Erlang term: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0857512522-4">[</span><span class="ss">hello</span><span class="p" data-group-id="0857512522-4">]</span><span class="p" data-group-id="0857512522-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">32&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5197054408-3">(</span><span class="s">&quot;this outputs one Erlang term: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5197054408-4">[</span><span class="ss">hello</span><span class="p" data-group-id="5197054408-4">]</span><span class="p" data-group-id="5197054408-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">this</span><span class="w"> </span><span class="ss">outputs</span><span class="w"> </span><span class="ss">one</span><span class="w"> </span><span class="n">Erlang</span><span class="w"> </span><span class="nc">term</span><span class="p">:</span><span class="w"> </span><span class="ss">hello</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">33&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0857512522-5">(</span><span class="s">&quot;this outputs two Erlang terms: </span><span class="si">~w</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0857512522-6">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">world</span><span class="p" data-group-id="0857512522-6">]</span><span class="p" data-group-id="0857512522-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">33&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5197054408-5">(</span><span class="s">&quot;this outputs two Erlang terms: </span><span class="si">~w</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5197054408-6">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">world</span><span class="p" data-group-id="5197054408-6">]</span><span class="p" data-group-id="5197054408-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">this</span><span class="w"> </span><span class="ss">outputs</span><span class="w"> </span><span class="ss">two</span><span class="w"> </span><span class="n">Erlang</span><span class="w"> </span><span class="nc">terms</span><span class="p">:</span><span class="w"> </span><span class="ss">helloworld</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">34&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0857512522-7">(</span><span class="s">&quot;this outputs two Erlang terms: </span><span class="si">~w</span><span class="s"> </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0857512522-8">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">world</span><span class="p" data-group-id="0857512522-8">]</span><span class="p" data-group-id="0857512522-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">34&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5197054408-7">(</span><span class="s">&quot;this outputs two Erlang terms: </span><span class="si">~w</span><span class="s"> </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5197054408-8">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">world</span><span class="p" data-group-id="5197054408-8">]</span><span class="p" data-group-id="5197054408-7">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">this</span><span class="w"> </span><span class="ss">outputs</span><span class="w"> </span><span class="ss">two</span><span class="w"> </span><span class="n">Erlang</span><span class="w"> </span><span class="nc">terms</span><span class="p">:</span><span class="w"> </span><span class="ss">hello</span><span class="w"> </span><span class="ss">world</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>The function <a href="../../lib/stdlib-8.0/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> (that is, <code class="inline">format</code> with two arguments) takes two lists.
│ │ │  The first one is nearly always a list written between <code class="inline">&quot; &quot;</code>. This list is printed
│ │ │  out as it is, except that each <code class="inline">~w</code> is replaced by a term taken in order from the
│ │ │  second list. Each <code class="inline">~n</code> is replaced by a new line. The <a href="../../lib/stdlib-8.0/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> function
│ │ │  itself returns the atom <code class="inline">ok</code> if everything goes as planned. Like other functions
│ │ │  in Erlang, it crashes if an error occurs. This is not a fault in Erlang, it is a
│ │ │ @@ -473,34 +473,34 @@
│ │ │    <span class="text">A Larger Example</span>
│ │ │  </h2>
│ │ │  <p>Now for a larger example to consolidate what you have learnt so far. Assume that
│ │ │  you have a list of temperature readings from a number of cities in the world.
│ │ │  Some of them are in Celsius and some in Fahrenheit (as in the previous list).
│ │ │  First let us convert them all to Celsius, then let us print the data neatly.</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% This module is in file tut5.erl</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7423899112-1">(</span><span class="ss">tut5</span><span class="p" data-group-id="7423899112-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7423899112-2">(</span><span class="p" data-group-id="7423899112-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7423899112-3">]</span><span class="p" data-group-id="7423899112-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5463888724-1">(</span><span class="ss">tut5</span><span class="p" data-group-id="5463888724-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5463888724-2">(</span><span class="p" data-group-id="5463888724-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5463888724-3">]</span><span class="p" data-group-id="5463888724-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% Only this function is exported</span><span class="w">
│ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="7423899112-4">(</span><span class="p" data-group-id="7423899112-5">[</span><span class="p" data-group-id="7423899112-5">]</span><span class="p" data-group-id="7423899112-4">)</span><span class="p">-&gt;</span><span class="w">                        </span><span class="c1">% No output for an empty list</span><span class="w">
│ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="5463888724-4">(</span><span class="p" data-group-id="5463888724-5">[</span><span class="p" data-group-id="5463888724-5">]</span><span class="p" data-group-id="5463888724-4">)</span><span class="p">-&gt;</span><span class="w">                        </span><span class="c1">% No output for an empty list</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="7423899112-6">(</span><span class="p" data-group-id="7423899112-7">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7423899112-7">]</span><span class="p" data-group-id="7423899112-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="7423899112-8">(</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="7423899112-9">(</span><span class="n">City</span><span class="p" data-group-id="7423899112-9">)</span><span class="p" data-group-id="7423899112-8">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">format_temps</span><span class="p" data-group-id="7423899112-10">(</span><span class="n">Rest</span><span class="p" data-group-id="7423899112-10">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="7423899112-11">(</span><span class="p" data-group-id="7423899112-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7423899112-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7423899112-13">}</span><span class="p" data-group-id="7423899112-12">}</span><span class="p" data-group-id="7423899112-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% No conversion needed</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7423899112-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7423899112-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7423899112-15">}</span><span class="p" data-group-id="7423899112-14">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="7423899112-16">(</span><span class="p" data-group-id="7423899112-17">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7423899112-18">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7423899112-18">}</span><span class="p" data-group-id="7423899112-17">}</span><span class="p" data-group-id="7423899112-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Do the conversion</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7423899112-19">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7423899112-20">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7423899112-21">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="7423899112-21">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="7423899112-20">}</span><span class="p" data-group-id="7423899112-19">}</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="7423899112-22">(</span><span class="p" data-group-id="7423899112-23">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7423899112-24">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7423899112-24">}</span><span class="p" data-group-id="7423899112-23">}</span><span class="p" data-group-id="7423899112-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7423899112-25">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7423899112-26">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7423899112-26">]</span><span class="p" data-group-id="7423899112-25">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">35&gt; </span><span class="nf">c</span><span class="p" data-group-id="4052243119-1">(</span><span class="ss">tut5</span><span class="p" data-group-id="4052243119-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4052243119-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut5</span><span class="p" data-group-id="4052243119-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">36&gt; </span><span class="nc">tut5</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="4052243119-3">(</span><span class="p" data-group-id="4052243119-4">[</span><span class="p" data-group-id="4052243119-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4052243119-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="4052243119-6">}</span><span class="p" data-group-id="4052243119-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4052243119-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4052243119-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="4052243119-8">}</span><span class="p" data-group-id="4052243119-7">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4052243119-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4052243119-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="4052243119-10">}</span><span class="p" data-group-id="4052243119-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4052243119-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4052243119-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="4052243119-12">}</span><span class="p" data-group-id="4052243119-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4052243119-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4052243119-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="4052243119-14">}</span><span class="p" data-group-id="4052243119-13">}</span><span class="p" data-group-id="4052243119-4">]</span><span class="p" data-group-id="4052243119-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="5463888724-6">(</span><span class="p" data-group-id="5463888724-7">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5463888724-7">]</span><span class="p" data-group-id="5463888724-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="5463888724-8">(</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="5463888724-9">(</span><span class="n">City</span><span class="p" data-group-id="5463888724-9">)</span><span class="p" data-group-id="5463888724-8">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">format_temps</span><span class="p" data-group-id="5463888724-10">(</span><span class="n">Rest</span><span class="p" data-group-id="5463888724-10">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="5463888724-11">(</span><span class="p" data-group-id="5463888724-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5463888724-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5463888724-13">}</span><span class="p" data-group-id="5463888724-12">}</span><span class="p" data-group-id="5463888724-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% No conversion needed</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5463888724-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5463888724-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5463888724-15">}</span><span class="p" data-group-id="5463888724-14">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="5463888724-16">(</span><span class="p" data-group-id="5463888724-17">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5463888724-18">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5463888724-18">}</span><span class="p" data-group-id="5463888724-17">}</span><span class="p" data-group-id="5463888724-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Do the conversion</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5463888724-19">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5463888724-20">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5463888724-21">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="5463888724-21">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="5463888724-20">}</span><span class="p" data-group-id="5463888724-19">}</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="5463888724-22">(</span><span class="p" data-group-id="5463888724-23">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5463888724-24">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5463888724-24">}</span><span class="p" data-group-id="5463888724-23">}</span><span class="p" data-group-id="5463888724-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5463888724-25">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5463888724-26">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5463888724-26">]</span><span class="p" data-group-id="5463888724-25">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">35&gt; </span><span class="nf">c</span><span class="p" data-group-id="8809747928-1">(</span><span class="ss">tut5</span><span class="p" data-group-id="8809747928-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8809747928-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut5</span><span class="p" data-group-id="8809747928-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">36&gt; </span><span class="nc">tut5</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="8809747928-3">(</span><span class="p" data-group-id="8809747928-4">[</span><span class="p" data-group-id="8809747928-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8809747928-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="8809747928-6">}</span><span class="p" data-group-id="8809747928-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8809747928-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8809747928-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="8809747928-8">}</span><span class="p" data-group-id="8809747928-7">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8809747928-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8809747928-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="8809747928-10">}</span><span class="p" data-group-id="8809747928-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8809747928-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8809747928-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="8809747928-12">}</span><span class="p" data-group-id="8809747928-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8809747928-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8809747928-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="8809747928-14">}</span><span class="p" data-group-id="8809747928-13">}</span><span class="p" data-group-id="8809747928-4">]</span><span class="p" data-group-id="8809747928-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">moscow</span><span class="w">          </span><span class="o">-</span><span class="mi">10</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">cape_town</span><span class="w">       </span><span class="mf">21.11111111111111</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">stockholm</span><span class="w">       </span><span class="o">-</span><span class="mi">4</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">paris</span><span class="w">           </span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">london</span><span class="w">          </span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>Before looking at how this program works, notice that a few comments are added
│ │ │  to the code. A comment starts with a %-character and goes on to the end of the
│ │ │ @@ -528,28 +528,28 @@
│ │ │    <a href="#matching-guards-and-scope-of-variables" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Matching, Guards, and Scope of Variables</span>
│ │ │  </h2>
│ │ │  <p>It can be useful to find the maximum and minimum temperature in lists like this.
│ │ │  Before extending the program to do this, let us look at functions for finding
│ │ │ -the maximum value of the elements in a list:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2360209100-1">(</span><span class="ss">tut6</span><span class="p" data-group-id="2360209100-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2360209100-2">(</span><span class="p" data-group-id="2360209100-3">[</span><span class="ss">list_max</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2360209100-3">]</span><span class="p" data-group-id="2360209100-2">)</span><span class="p">.</span><span class="w">
│ │ │ +the maximum value of the elements in a list:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2150714959-1">(</span><span class="ss">tut6</span><span class="p" data-group-id="2150714959-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2150714959-2">(</span><span class="p" data-group-id="2150714959-3">[</span><span class="ss">list_max</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2150714959-3">]</span><span class="p" data-group-id="2150714959-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">list_max</span><span class="p" data-group-id="2360209100-4">(</span><span class="p" data-group-id="2360209100-5">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="2360209100-5">]</span><span class="p" data-group-id="2360209100-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="nf">list_max</span><span class="p" data-group-id="2360209100-6">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Head</span><span class="p" data-group-id="2360209100-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">list_max</span><span class="p" data-group-id="2150714959-4">(</span><span class="p" data-group-id="2150714959-5">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="2150714959-5">]</span><span class="p" data-group-id="2150714959-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="nf">list_max</span><span class="p" data-group-id="2150714959-6">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Head</span><span class="p" data-group-id="2150714959-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">list_max</span><span class="p" data-group-id="2360209100-7">(</span><span class="p" data-group-id="2360209100-8">[</span><span class="p" data-group-id="2360209100-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="2360209100-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">list_max</span><span class="p" data-group-id="2150714959-7">(</span><span class="p" data-group-id="2150714959-8">[</span><span class="p" data-group-id="2150714959-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="2150714959-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Res</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">list_max</span><span class="p" data-group-id="2360209100-9">(</span><span class="p" data-group-id="2360209100-10">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="2360209100-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="2360209100-9">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Head</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Result_so_far</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">list_max</span><span class="p" data-group-id="2360209100-11">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Head</span><span class="p" data-group-id="2360209100-11">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">list_max</span><span class="p" data-group-id="2360209100-12">(</span><span class="p" data-group-id="2360209100-13">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="2360209100-13">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="2360209100-12">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">list_max</span><span class="p" data-group-id="2360209100-14">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="2360209100-14">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">37&gt; </span><span class="nf">c</span><span class="p" data-group-id="6447967883-1">(</span><span class="ss">tut6</span><span class="p" data-group-id="6447967883-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6447967883-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut6</span><span class="p" data-group-id="6447967883-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">38&gt; </span><span class="nc">tut6</span><span class="p">:</span><span class="nf">list_max</span><span class="p" data-group-id="6447967883-3">(</span><span class="p" data-group-id="6447967883-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6447967883-4">]</span><span class="p" data-group-id="6447967883-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">list_max</span><span class="p" data-group-id="2150714959-9">(</span><span class="p" data-group-id="2150714959-10">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="2150714959-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="2150714959-9">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Head</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Result_so_far</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">list_max</span><span class="p" data-group-id="2150714959-11">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Head</span><span class="p" data-group-id="2150714959-11">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">list_max</span><span class="p" data-group-id="2150714959-12">(</span><span class="p" data-group-id="2150714959-13">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="2150714959-13">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="2150714959-12">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">list_max</span><span class="p" data-group-id="2150714959-14">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="2150714959-14">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">37&gt; </span><span class="nf">c</span><span class="p" data-group-id="0141561606-1">(</span><span class="ss">tut6</span><span class="p" data-group-id="0141561606-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0141561606-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut6</span><span class="p" data-group-id="0141561606-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">38&gt; </span><span class="nc">tut6</span><span class="p">:</span><span class="nf">list_max</span><span class="p" data-group-id="0141561606-3">(</span><span class="p" data-group-id="0141561606-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0141561606-4">]</span><span class="p" data-group-id="0141561606-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">7</span></code></pre><p>First notice that two functions have the same name, <code class="inline">list_max</code>. However, each of
│ │ │  these takes a different number of arguments (parameters). In Erlang these are
│ │ │  regarded as completely different functions. Where you need to distinguish
│ │ │  between these functions, you write Name/Arity, where Name is the function name
│ │ │  and Arity is the number of arguments, in this case <code class="inline">list_max/1</code> and
│ │ │  <code class="inline">list_max/2</code>.</p><p>In this example you walk through a list &quot;carrying&quot; a value, in this case
│ │ │  <code class="inline">Result_so_far</code>. <code class="inline">list_max/1</code> simply assumes that the max value of the list is
│ │ │ @@ -578,180 +578,180 @@
│ │ │  </span><span class="mi">5</span><span class="w">
│ │ │  </span><span class="gp unselectable">40&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no match of right hand side value 6</span><span class="w">
│ │ │  </span><span class="gp unselectable">41&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no match of right hand side value 6</span><span class="w">
│ │ │  </span><span class="gp unselectable">42&gt; </span><span class="n">N</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">6</span></code></pre><p>The use of the match operator is particularly useful for pulling apart Erlang
│ │ │ -terms and creating new ones.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">43&gt; </span><span class="p" data-group-id="9765713146-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9765713146-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9765713146-2">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9765713146-3">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="9765713146-3">}</span><span class="p" data-group-id="9765713146-2">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9765713146-4">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="9765713146-5">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">28</span><span class="p" data-group-id="9765713146-5">}</span><span class="p" data-group-id="9765713146-4">}</span><span class="w">
│ │ │ +terms and creating new ones.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">43&gt; </span><span class="p" data-group-id="8959535614-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8959535614-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8959535614-2">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8959535614-3">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="8959535614-3">}</span><span class="p" data-group-id="8959535614-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8959535614-4">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="8959535614-5">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">28</span><span class="p" data-group-id="8959535614-5">}</span><span class="p" data-group-id="8959535614-4">}</span><span class="w">
│ │ │  </span><span class="gp unselectable">44&gt; </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">paris</span><span class="w">
│ │ │  </span><span class="gp unselectable">45&gt; </span><span class="n">Y</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9765713146-6">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">28</span><span class="p" data-group-id="9765713146-6">}</span></code></pre><p>Here <code class="inline">X</code> gets the value <code class="inline">paris</code> and <code class="inline">Y</code> the value <code class="inline">{f,28}</code>.</p><p>If you try to do the same again with another city, an error is returned:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">46&gt; </span><span class="p" data-group-id="3082541677-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3082541677-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3082541677-2">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3082541677-3">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="3082541677-3">}</span><span class="p" data-group-id="3082541677-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8959535614-6">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">28</span><span class="p" data-group-id="8959535614-6">}</span></code></pre><p>Here <code class="inline">X</code> gets the value <code class="inline">paris</code> and <code class="inline">Y</code> the value <code class="inline">{f,28}</code>.</p><p>If you try to do the same again with another city, an error is returned:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">46&gt; </span><span class="p" data-group-id="3427770967-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3427770967-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3427770967-2">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3427770967-3">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="3427770967-3">}</span><span class="p" data-group-id="3427770967-2">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no match of right hand side value {london,{f,36}}</span></code></pre><p>Variables can also be used to improve the readability of programs. For example,
│ │ │ -in function <code class="inline">list_max/2</code> above, you can write:</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_max</span><span class="p" data-group-id="5140476783-1">(</span><span class="p" data-group-id="5140476783-2">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="5140476783-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="5140476783-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Head</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Result_so_far</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +in function <code class="inline">list_max/2</code> above, you can write:</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_max</span><span class="p" data-group-id="7060686523-1">(</span><span class="p" data-group-id="7060686523-2">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="7060686523-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="7060686523-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Head</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Result_so_far</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">New_result_far</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Head</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">list_max</span><span class="p" data-group-id="5140476783-3">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">New_result_far</span><span class="p" data-group-id="5140476783-3">)</span><span class="p">;</span></code></pre><p>This is possibly a little clearer.</p><h2 id="more-about-lists" class="section-heading">
│ │ │ +    </span><span class="nf">list_max</span><span class="p" data-group-id="7060686523-3">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">New_result_far</span><span class="p" data-group-id="7060686523-3">)</span><span class="p">;</span></code></pre><p>This is possibly a little clearer.</p><h2 id="more-about-lists" class="section-heading">
│ │ │    <a href="#more-about-lists" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">More About Lists</span>
│ │ │  </h2>
│ │ │ -<p>Remember that the <code class="inline">|</code> operator can be used to get the head of a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">47&gt; </span><span class="p" data-group-id="6069860300-1">[</span><span class="n">M1</span><span class="p">|</span><span class="n">T1</span><span class="p" data-group-id="6069860300-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6069860300-2">[</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="ss">rome</span><span class="p" data-group-id="6069860300-2">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6069860300-3">[</span><span class="ss">paris</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="6069860300-3">]</span><span class="w">
│ │ │ +<p>Remember that the <code class="inline">|</code> operator can be used to get the head of a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">47&gt; </span><span class="p" data-group-id="2038596824-1">[</span><span class="n">M1</span><span class="p">|</span><span class="n">T1</span><span class="p" data-group-id="2038596824-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2038596824-2">[</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="ss">rome</span><span class="p" data-group-id="2038596824-2">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2038596824-3">[</span><span class="ss">paris</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="2038596824-3">]</span><span class="w">
│ │ │  </span><span class="gp unselectable">48&gt; </span><span class="n">M1</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">paris</span><span class="w">
│ │ │  </span><span class="gp unselectable">49&gt; </span><span class="n">T1</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6069860300-4">[</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="6069860300-4">]</span></code></pre><p>The <code class="inline">|</code> operator can also be used to add a head to a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">50&gt; </span><span class="n">L1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6876095407-1">[</span><span class="ss">madrid</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="6876095407-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6876095407-2">[</span><span class="ss">madrid</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="6876095407-2">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2038596824-4">[</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="2038596824-4">]</span></code></pre><p>The <code class="inline">|</code> operator can also be used to add a head to a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">50&gt; </span><span class="n">L1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7014443986-1">[</span><span class="ss">madrid</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="7014443986-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7014443986-2">[</span><span class="ss">madrid</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="7014443986-2">]</span><span class="w">
│ │ │  </span><span class="gp unselectable">51&gt; </span><span class="n">L1</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6876095407-3">[</span><span class="ss">madrid</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="6876095407-3">]</span></code></pre><p>Now an example of this when working with lists - reversing the order of a list:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3158662253-1">(</span><span class="ss">tut8</span><span class="p" data-group-id="3158662253-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7014443986-3">[</span><span class="ss">madrid</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="7014443986-3">]</span></code></pre><p>Now an example of this when working with lists - reversing the order of a list:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9315902019-1">(</span><span class="ss">tut8</span><span class="p" data-group-id="9315902019-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3158662253-2">(</span><span class="p" data-group-id="3158662253-3">[</span><span class="ss">reverse</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3158662253-3">]</span><span class="p" data-group-id="3158662253-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9315902019-2">(</span><span class="p" data-group-id="9315902019-3">[</span><span class="ss">reverse</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9315902019-3">]</span><span class="p" data-group-id="9315902019-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="3158662253-4">(</span><span class="n">List</span><span class="p" data-group-id="3158662253-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="3158662253-5">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3158662253-6">[</span><span class="p" data-group-id="3158662253-6">]</span><span class="p" data-group-id="3158662253-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="9315902019-4">(</span><span class="n">List</span><span class="p" data-group-id="9315902019-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="9315902019-5">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9315902019-6">[</span><span class="p" data-group-id="9315902019-6">]</span><span class="p" data-group-id="9315902019-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="3158662253-7">(</span><span class="p" data-group-id="3158662253-8">[</span><span class="n">Head</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3158662253-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="3158662253-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="3158662253-9">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3158662253-10">[</span><span class="n">Head</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="3158662253-10">]</span><span class="p" data-group-id="3158662253-9">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="3158662253-11">(</span><span class="p" data-group-id="3158662253-12">[</span><span class="p" data-group-id="3158662253-12">]</span><span class="p">,</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="3158662253-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Reversed_List</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">52&gt; </span><span class="nf">c</span><span class="p" data-group-id="5580842183-1">(</span><span class="ss">tut8</span><span class="p" data-group-id="5580842183-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5580842183-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut8</span><span class="p" data-group-id="5580842183-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">53&gt; </span><span class="nc">tut8</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="5580842183-3">(</span><span class="p" data-group-id="5580842183-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5580842183-4">]</span><span class="p" data-group-id="5580842183-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5580842183-5">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5580842183-5">]</span></code></pre><p>Consider how <code class="inline">Reversed_List</code> is built. It starts as [], then successively the
│ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="9315902019-7">(</span><span class="p" data-group-id="9315902019-8">[</span><span class="n">Head</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9315902019-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="9315902019-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="9315902019-9">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9315902019-10">[</span><span class="n">Head</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="9315902019-10">]</span><span class="p" data-group-id="9315902019-9">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="9315902019-11">(</span><span class="p" data-group-id="9315902019-12">[</span><span class="p" data-group-id="9315902019-12">]</span><span class="p">,</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="9315902019-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Reversed_List</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">52&gt; </span><span class="nf">c</span><span class="p" data-group-id="9135364401-1">(</span><span class="ss">tut8</span><span class="p" data-group-id="9135364401-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9135364401-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut8</span><span class="p" data-group-id="9135364401-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">53&gt; </span><span class="nc">tut8</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="9135364401-3">(</span><span class="p" data-group-id="9135364401-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9135364401-4">]</span><span class="p" data-group-id="9135364401-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9135364401-5">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9135364401-5">]</span></code></pre><p>Consider how <code class="inline">Reversed_List</code> is built. It starts as [], then successively the
│ │ │  heads are taken off of the list to be reversed and added to the
│ │ │ -<code class="inline">Reversed_List</code>, as shown in the following:</p><pre><code class="makeup erlang" translate="no"><span class="nf">reverse</span><span class="p" data-group-id="2152463635-1">(</span><span class="p" data-group-id="2152463635-2">[</span><span class="mi">1</span><span class="p">|</span><span class="p" data-group-id="2152463635-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2152463635-3">]</span><span class="p" data-group-id="2152463635-2">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2152463635-4">[</span><span class="p" data-group-id="2152463635-4">]</span><span class="p" data-group-id="2152463635-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="2152463635-5">(</span><span class="p" data-group-id="2152463635-6">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2152463635-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2152463635-7">[</span><span class="mi">1</span><span class="p">|</span><span class="p" data-group-id="2152463635-8">[</span><span class="p" data-group-id="2152463635-8">]</span><span class="p" data-group-id="2152463635-7">]</span><span class="p" data-group-id="2152463635-5">)</span><span class="w">
│ │ │ +<code class="inline">Reversed_List</code>, as shown in the following:</p><pre><code class="makeup erlang" translate="no"><span class="nf">reverse</span><span class="p" data-group-id="4764279497-1">(</span><span class="p" data-group-id="4764279497-2">[</span><span class="mi">1</span><span class="p">|</span><span class="p" data-group-id="4764279497-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4764279497-3">]</span><span class="p" data-group-id="4764279497-2">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4764279497-4">[</span><span class="p" data-group-id="4764279497-4">]</span><span class="p" data-group-id="4764279497-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="4764279497-5">(</span><span class="p" data-group-id="4764279497-6">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4764279497-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4764279497-7">[</span><span class="mi">1</span><span class="p">|</span><span class="p" data-group-id="4764279497-8">[</span><span class="p" data-group-id="4764279497-8">]</span><span class="p" data-group-id="4764279497-7">]</span><span class="p" data-group-id="4764279497-5">)</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="2152463635-9">(</span><span class="p" data-group-id="2152463635-10">[</span><span class="mi">2</span><span class="p">|</span><span class="p" data-group-id="2152463635-11">[</span><span class="mi">3</span><span class="p" data-group-id="2152463635-11">]</span><span class="p" data-group-id="2152463635-10">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2152463635-12">[</span><span class="mi">1</span><span class="p" data-group-id="2152463635-12">]</span><span class="p" data-group-id="2152463635-9">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="2152463635-13">(</span><span class="p" data-group-id="2152463635-14">[</span><span class="mi">3</span><span class="p" data-group-id="2152463635-14">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2152463635-15">[</span><span class="mi">2</span><span class="p">|</span><span class="p" data-group-id="2152463635-16">[</span><span class="mi">1</span><span class="p" data-group-id="2152463635-16">]</span><span class="p" data-group-id="2152463635-15">]</span><span class="p" data-group-id="2152463635-13">)</span><span class="w">
│ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="4764279497-9">(</span><span class="p" data-group-id="4764279497-10">[</span><span class="mi">2</span><span class="p">|</span><span class="p" data-group-id="4764279497-11">[</span><span class="mi">3</span><span class="p" data-group-id="4764279497-11">]</span><span class="p" data-group-id="4764279497-10">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4764279497-12">[</span><span class="mi">1</span><span class="p" data-group-id="4764279497-12">]</span><span class="p" data-group-id="4764279497-9">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="4764279497-13">(</span><span class="p" data-group-id="4764279497-14">[</span><span class="mi">3</span><span class="p" data-group-id="4764279497-14">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4764279497-15">[</span><span class="mi">2</span><span class="p">|</span><span class="p" data-group-id="4764279497-16">[</span><span class="mi">1</span><span class="p" data-group-id="4764279497-16">]</span><span class="p" data-group-id="4764279497-15">]</span><span class="p" data-group-id="4764279497-13">)</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="2152463635-17">(</span><span class="p" data-group-id="2152463635-18">[</span><span class="mi">3</span><span class="p">|</span><span class="p" data-group-id="2152463635-19">[</span><span class="p" data-group-id="2152463635-19">]</span><span class="p" data-group-id="2152463635-18">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2152463635-20">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2152463635-20">]</span><span class="p" data-group-id="2152463635-17">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="2152463635-21">(</span><span class="p" data-group-id="2152463635-22">[</span><span class="p" data-group-id="2152463635-22">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2152463635-23">[</span><span class="mi">3</span><span class="p">|</span><span class="p" data-group-id="2152463635-24">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2152463635-24">]</span><span class="p" data-group-id="2152463635-23">]</span><span class="p" data-group-id="2152463635-21">)</span><span class="w">
│ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="4764279497-17">(</span><span class="p" data-group-id="4764279497-18">[</span><span class="mi">3</span><span class="p">|</span><span class="p" data-group-id="4764279497-19">[</span><span class="p" data-group-id="4764279497-19">]</span><span class="p" data-group-id="4764279497-18">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4764279497-20">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4764279497-20">]</span><span class="p" data-group-id="4764279497-17">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="4764279497-21">(</span><span class="p" data-group-id="4764279497-22">[</span><span class="p" data-group-id="4764279497-22">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4764279497-23">[</span><span class="mi">3</span><span class="p">|</span><span class="p" data-group-id="4764279497-24">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4764279497-24">]</span><span class="p" data-group-id="4764279497-23">]</span><span class="p" data-group-id="4764279497-21">)</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="2152463635-25">(</span><span class="p" data-group-id="2152463635-26">[</span><span class="p" data-group-id="2152463635-26">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2152463635-27">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2152463635-27">]</span><span class="p" data-group-id="2152463635-25">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2152463635-28">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2152463635-28">]</span></code></pre><p>The module <code class="inline">lists</code> contains many functions for manipulating lists, for example,
│ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="4764279497-25">(</span><span class="p" data-group-id="4764279497-26">[</span><span class="p" data-group-id="4764279497-26">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4764279497-27">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4764279497-27">]</span><span class="p" data-group-id="4764279497-25">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4764279497-28">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4764279497-28">]</span></code></pre><p>The module <code class="inline">lists</code> contains many functions for manipulating lists, for example,
│ │ │  for reversing them. So before writing a list-manipulating function it is a good
│ │ │  idea to check if one has not already been written for you (see the <a href="../../lib/stdlib-8.0/doc/html/lists.html"><code class="inline">lists</code></a> manual
│ │ │  page in STDLIB).</p><p>Now let us get back to the cities and temperatures, but take a more structured
│ │ │ -approach this time. First let us convert the whole list to Celsius as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7068861903-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="7068861903-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7068861903-2">(</span><span class="p" data-group-id="7068861903-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7068861903-3">]</span><span class="p" data-group-id="7068861903-2">)</span><span class="p">.</span><span class="w">
│ │ │ +approach this time. First let us convert the whole list to Celsius as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2978500425-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="2978500425-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2978500425-2">(</span><span class="p" data-group-id="2978500425-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2978500425-3">]</span><span class="p" data-group-id="2978500425-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="7068861903-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="7068861903-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7068861903-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="7068861903-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="2978500425-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="2978500425-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="2978500425-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="2978500425-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7068861903-6">(</span><span class="p" data-group-id="7068861903-7">[</span><span class="p" data-group-id="7068861903-8">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7068861903-9">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="7068861903-9">}</span><span class="p" data-group-id="7068861903-8">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7068861903-7">]</span><span class="p" data-group-id="7068861903-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7068861903-10">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7068861903-11">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7068861903-12">(</span><span class="n">F</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="7068861903-12">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="7068861903-11">}</span><span class="p" data-group-id="7068861903-10">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7068861903-13">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7068861903-14">(</span><span class="n">Rest</span><span class="p" data-group-id="7068861903-14">)</span><span class="p" data-group-id="7068861903-13">]</span><span class="p">;</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7068861903-15">(</span><span class="p" data-group-id="7068861903-16">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7068861903-16">]</span><span class="p" data-group-id="7068861903-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7068861903-17">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7068861903-18">(</span><span class="n">Rest</span><span class="p" data-group-id="7068861903-18">)</span><span class="p" data-group-id="7068861903-17">]</span><span class="p">;</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7068861903-19">(</span><span class="p" data-group-id="7068861903-20">[</span><span class="p" data-group-id="7068861903-20">]</span><span class="p" data-group-id="7068861903-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7068861903-21">[</span><span class="p" data-group-id="7068861903-21">]</span><span class="p">.</span></code></pre><p>Test the function:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">54&gt; </span><span class="nf">c</span><span class="p" data-group-id="9214305811-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="9214305811-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9214305811-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut7</span><span class="p" data-group-id="9214305811-2">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">55&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="9214305811-3">(</span><span class="p" data-group-id="9214305811-4">[</span><span class="p" data-group-id="9214305811-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9214305811-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="9214305811-6">}</span><span class="p" data-group-id="9214305811-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9214305811-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9214305811-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="9214305811-8">}</span><span class="p" data-group-id="9214305811-7">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9214305811-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9214305811-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="9214305811-10">}</span><span class="p" data-group-id="9214305811-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9214305811-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9214305811-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="9214305811-12">}</span><span class="p" data-group-id="9214305811-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9214305811-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9214305811-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="9214305811-14">}</span><span class="p" data-group-id="9214305811-13">}</span><span class="p" data-group-id="9214305811-4">]</span><span class="p" data-group-id="9214305811-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9214305811-15">[</span><span class="p" data-group-id="9214305811-16">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="9214305811-17">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="9214305811-17">}</span><span class="p" data-group-id="9214305811-16">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9214305811-18">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="9214305811-19">{</span><span class="ss">c</span><span class="p">,</span><span class="mf">21.11111111111111</span><span class="p" data-group-id="9214305811-19">}</span><span class="p" data-group-id="9214305811-18">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9214305811-20">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="9214305811-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="9214305811-21">}</span><span class="p" data-group-id="9214305811-20">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9214305811-22">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="9214305811-23">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="p" data-group-id="9214305811-23">}</span><span class="p" data-group-id="9214305811-22">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9214305811-24">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="9214305811-25">{</span><span class="ss">c</span><span class="p">,</span><span class="mf">2.2222222222222223</span><span class="p" data-group-id="9214305811-25">}</span><span class="p" data-group-id="9214305811-24">}</span><span class="p" data-group-id="9214305811-15">]</span></code></pre><p>Explanation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">format_temps</span><span class="p" data-group-id="7529481358-1">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="7529481358-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7529481358-2">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="7529481358-2">)</span><span class="p">.</span></code></pre><p>Here <code class="inline">format_temps/1</code> calls <code class="inline">convert_list_to_c/1</code>. <code class="inline">convert_list_to_c/1</code> takes
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="2978500425-6">(</span><span class="p" data-group-id="2978500425-7">[</span><span class="p" data-group-id="2978500425-8">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2978500425-9">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="2978500425-9">}</span><span class="p" data-group-id="2978500425-8">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="2978500425-7">]</span><span class="p" data-group-id="2978500425-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2978500425-10">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2978500425-11">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2978500425-12">(</span><span class="n">F</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="2978500425-12">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="2978500425-11">}</span><span class="p" data-group-id="2978500425-10">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2978500425-13">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="2978500425-14">(</span><span class="n">Rest</span><span class="p" data-group-id="2978500425-14">)</span><span class="p" data-group-id="2978500425-13">]</span><span class="p">;</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="2978500425-15">(</span><span class="p" data-group-id="2978500425-16">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="2978500425-16">]</span><span class="p" data-group-id="2978500425-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2978500425-17">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="2978500425-18">(</span><span class="n">Rest</span><span class="p" data-group-id="2978500425-18">)</span><span class="p" data-group-id="2978500425-17">]</span><span class="p">;</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="2978500425-19">(</span><span class="p" data-group-id="2978500425-20">[</span><span class="p" data-group-id="2978500425-20">]</span><span class="p" data-group-id="2978500425-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2978500425-21">[</span><span class="p" data-group-id="2978500425-21">]</span><span class="p">.</span></code></pre><p>Test the function:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">54&gt; </span><span class="nf">c</span><span class="p" data-group-id="0600070445-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="0600070445-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0600070445-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut7</span><span class="p" data-group-id="0600070445-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">55&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="0600070445-3">(</span><span class="p" data-group-id="0600070445-4">[</span><span class="p" data-group-id="0600070445-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0600070445-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="0600070445-6">}</span><span class="p" data-group-id="0600070445-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0600070445-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0600070445-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="0600070445-8">}</span><span class="p" data-group-id="0600070445-7">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0600070445-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0600070445-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="0600070445-10">}</span><span class="p" data-group-id="0600070445-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0600070445-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0600070445-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="0600070445-12">}</span><span class="p" data-group-id="0600070445-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0600070445-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0600070445-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="0600070445-14">}</span><span class="p" data-group-id="0600070445-13">}</span><span class="p" data-group-id="0600070445-4">]</span><span class="p" data-group-id="0600070445-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0600070445-15">[</span><span class="p" data-group-id="0600070445-16">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="0600070445-17">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="0600070445-17">}</span><span class="p" data-group-id="0600070445-16">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0600070445-18">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="0600070445-19">{</span><span class="ss">c</span><span class="p">,</span><span class="mf">21.11111111111111</span><span class="p" data-group-id="0600070445-19">}</span><span class="p" data-group-id="0600070445-18">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0600070445-20">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="0600070445-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="0600070445-21">}</span><span class="p" data-group-id="0600070445-20">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0600070445-22">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="0600070445-23">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="p" data-group-id="0600070445-23">}</span><span class="p" data-group-id="0600070445-22">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0600070445-24">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="0600070445-25">{</span><span class="ss">c</span><span class="p">,</span><span class="mf">2.2222222222222223</span><span class="p" data-group-id="0600070445-25">}</span><span class="p" data-group-id="0600070445-24">}</span><span class="p" data-group-id="0600070445-15">]</span></code></pre><p>Explanation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">format_temps</span><span class="p" data-group-id="2361765383-1">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="2361765383-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="2361765383-2">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="2361765383-2">)</span><span class="p">.</span></code></pre><p>Here <code class="inline">format_temps/1</code> calls <code class="inline">convert_list_to_c/1</code>. <code class="inline">convert_list_to_c/1</code> takes
│ │ │  off the head of the <code class="inline">List_of_cities</code>, converts it to Celsius if needed. The <code class="inline">|</code>
│ │ │ -operator is used to add the (maybe converted) value to the rest of the list:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8460153128-1">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="8460153128-2">(</span><span class="n">Rest</span><span class="p" data-group-id="8460153128-2">)</span><span class="p" data-group-id="8460153128-1">]</span><span class="p">;</span></code></pre><p>or:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4788470338-1">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="4788470338-2">(</span><span class="n">Rest</span><span class="p" data-group-id="4788470338-2">)</span><span class="p" data-group-id="4788470338-1">]</span><span class="p">;</span></code></pre><p>This is done until the end of the list is reached, that is, the list is empty:</p><pre><code class="makeup erlang" translate="no"><span class="nf">convert_list_to_c</span><span class="p" data-group-id="4237677634-1">(</span><span class="p" data-group-id="4237677634-2">[</span><span class="p" data-group-id="4237677634-2">]</span><span class="p" data-group-id="4237677634-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4237677634-3">[</span><span class="p" data-group-id="4237677634-3">]</span><span class="p">.</span></code></pre><p>Now when the list is converted, a function to print it is added:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5975835102-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="5975835102-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5975835102-2">(</span><span class="p" data-group-id="5975835102-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5975835102-3">]</span><span class="p" data-group-id="5975835102-2">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="5975835102-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="5975835102-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Converted_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5975835102-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="5975835102-5">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="5975835102-6">(</span><span class="n">Converted_List</span><span class="p" data-group-id="5975835102-6">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5975835102-7">(</span><span class="p" data-group-id="5975835102-8">[</span><span class="p" data-group-id="5975835102-9">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5975835102-10">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="5975835102-10">}</span><span class="p" data-group-id="5975835102-9">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5975835102-8">]</span><span class="p" data-group-id="5975835102-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5975835102-11">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5975835102-12">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5975835102-13">(</span><span class="n">F</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="5975835102-13">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="5975835102-12">}</span><span class="p" data-group-id="5975835102-11">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5975835102-14">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5975835102-15">(</span><span class="n">Rest</span><span class="p" data-group-id="5975835102-15">)</span><span class="p" data-group-id="5975835102-14">]</span><span class="p">;</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5975835102-16">(</span><span class="p" data-group-id="5975835102-17">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5975835102-17">]</span><span class="p" data-group-id="5975835102-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5975835102-18">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5975835102-19">(</span><span class="n">Rest</span><span class="p" data-group-id="5975835102-19">)</span><span class="p" data-group-id="5975835102-18">]</span><span class="p">;</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5975835102-20">(</span><span class="p" data-group-id="5975835102-21">[</span><span class="p" data-group-id="5975835102-21">]</span><span class="p" data-group-id="5975835102-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5975835102-22">[</span><span class="p" data-group-id="5975835102-22">]</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="5975835102-23">(</span><span class="p" data-group-id="5975835102-24">[</span><span class="p" data-group-id="5975835102-25">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5975835102-26">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5975835102-26">}</span><span class="p" data-group-id="5975835102-25">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5975835102-24">]</span><span class="p" data-group-id="5975835102-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5975835102-27">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5975835102-28">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5975835102-28">]</span><span class="p" data-group-id="5975835102-27">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="5975835102-29">(</span><span class="n">Rest</span><span class="p" data-group-id="5975835102-29">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="5975835102-30">(</span><span class="p" data-group-id="5975835102-31">[</span><span class="p" data-group-id="5975835102-31">]</span><span class="p" data-group-id="5975835102-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ok</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">56&gt; </span><span class="nf">c</span><span class="p" data-group-id="3125889697-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="3125889697-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3125889697-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut7</span><span class="p" data-group-id="3125889697-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">57&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="3125889697-3">(</span><span class="p" data-group-id="3125889697-4">[</span><span class="p" data-group-id="3125889697-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3125889697-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="3125889697-6">}</span><span class="p" data-group-id="3125889697-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3125889697-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3125889697-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="3125889697-8">}</span><span class="p" data-group-id="3125889697-7">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3125889697-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3125889697-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="3125889697-10">}</span><span class="p" data-group-id="3125889697-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3125889697-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3125889697-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="3125889697-12">}</span><span class="p" data-group-id="3125889697-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3125889697-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3125889697-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="3125889697-14">}</span><span class="p" data-group-id="3125889697-13">}</span><span class="p" data-group-id="3125889697-4">]</span><span class="p" data-group-id="3125889697-3">)</span><span class="p">.</span><span class="w">
│ │ │ +operator is used to add the (maybe converted) value to the rest of the list:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3541392849-1">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3541392849-2">(</span><span class="n">Rest</span><span class="p" data-group-id="3541392849-2">)</span><span class="p" data-group-id="3541392849-1">]</span><span class="p">;</span></code></pre><p>or:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6579751312-1">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="6579751312-2">(</span><span class="n">Rest</span><span class="p" data-group-id="6579751312-2">)</span><span class="p" data-group-id="6579751312-1">]</span><span class="p">;</span></code></pre><p>This is done until the end of the list is reached, that is, the list is empty:</p><pre><code class="makeup erlang" translate="no"><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1979049871-1">(</span><span class="p" data-group-id="1979049871-2">[</span><span class="p" data-group-id="1979049871-2">]</span><span class="p" data-group-id="1979049871-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1979049871-3">[</span><span class="p" data-group-id="1979049871-3">]</span><span class="p">.</span></code></pre><p>Now when the list is converted, a function to print it is added:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3739233089-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="3739233089-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3739233089-2">(</span><span class="p" data-group-id="3739233089-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3739233089-3">]</span><span class="p" data-group-id="3739233089-2">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="3739233089-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="3739233089-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Converted_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3739233089-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="3739233089-5">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="3739233089-6">(</span><span class="n">Converted_List</span><span class="p" data-group-id="3739233089-6">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3739233089-7">(</span><span class="p" data-group-id="3739233089-8">[</span><span class="p" data-group-id="3739233089-9">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3739233089-10">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="3739233089-10">}</span><span class="p" data-group-id="3739233089-9">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3739233089-8">]</span><span class="p" data-group-id="3739233089-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3739233089-11">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3739233089-12">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3739233089-13">(</span><span class="n">F</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="3739233089-13">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="3739233089-12">}</span><span class="p" data-group-id="3739233089-11">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3739233089-14">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3739233089-15">(</span><span class="n">Rest</span><span class="p" data-group-id="3739233089-15">)</span><span class="p" data-group-id="3739233089-14">]</span><span class="p">;</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3739233089-16">(</span><span class="p" data-group-id="3739233089-17">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3739233089-17">]</span><span class="p" data-group-id="3739233089-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3739233089-18">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3739233089-19">(</span><span class="n">Rest</span><span class="p" data-group-id="3739233089-19">)</span><span class="p" data-group-id="3739233089-18">]</span><span class="p">;</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3739233089-20">(</span><span class="p" data-group-id="3739233089-21">[</span><span class="p" data-group-id="3739233089-21">]</span><span class="p" data-group-id="3739233089-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3739233089-22">[</span><span class="p" data-group-id="3739233089-22">]</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="3739233089-23">(</span><span class="p" data-group-id="3739233089-24">[</span><span class="p" data-group-id="3739233089-25">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3739233089-26">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="3739233089-26">}</span><span class="p" data-group-id="3739233089-25">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3739233089-24">]</span><span class="p" data-group-id="3739233089-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3739233089-27">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3739233089-28">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="3739233089-28">]</span><span class="p" data-group-id="3739233089-27">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="3739233089-29">(</span><span class="n">Rest</span><span class="p" data-group-id="3739233089-29">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="3739233089-30">(</span><span class="p" data-group-id="3739233089-31">[</span><span class="p" data-group-id="3739233089-31">]</span><span class="p" data-group-id="3739233089-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ok</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">56&gt; </span><span class="nf">c</span><span class="p" data-group-id="5254466057-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="5254466057-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5254466057-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut7</span><span class="p" data-group-id="5254466057-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">57&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="5254466057-3">(</span><span class="p" data-group-id="5254466057-4">[</span><span class="p" data-group-id="5254466057-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5254466057-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="5254466057-6">}</span><span class="p" data-group-id="5254466057-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5254466057-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5254466057-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="5254466057-8">}</span><span class="p" data-group-id="5254466057-7">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5254466057-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5254466057-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="5254466057-10">}</span><span class="p" data-group-id="5254466057-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5254466057-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5254466057-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="5254466057-12">}</span><span class="p" data-group-id="5254466057-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5254466057-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5254466057-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="5254466057-14">}</span><span class="p" data-group-id="5254466057-13">}</span><span class="p" data-group-id="5254466057-4">]</span><span class="p" data-group-id="5254466057-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">moscow</span><span class="w">          </span><span class="o">-</span><span class="mi">10</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">cape_town</span><span class="w">       </span><span class="mf">21.11111111111111</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">stockholm</span><span class="w">       </span><span class="o">-</span><span class="mi">4</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">paris</span><span class="w">           </span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">london</span><span class="w">          </span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>Now a function has to be added to find the cities with the maximum and minimum
│ │ │  temperatures. The following program is not the most efficient way of doing this
│ │ │  as you walk through the list of cities four times. But it is better to first
│ │ │  strive for clarity and correctness and to make programs efficient only if
│ │ │ -needed.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5087476061-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="5087476061-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5087476061-2">(</span><span class="p" data-group-id="5087476061-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5087476061-3">]</span><span class="p" data-group-id="5087476061-2">)</span><span class="p">.</span><span class="w">
│ │ │ +needed.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5793119602-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="5793119602-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5793119602-2">(</span><span class="p" data-group-id="5793119602-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5793119602-3">]</span><span class="p" data-group-id="5793119602-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="5087476061-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="5087476061-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Converted_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5087476061-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="5087476061-5">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="5087476061-6">(</span><span class="n">Converted_List</span><span class="p" data-group-id="5087476061-6">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5087476061-7">{</span><span class="n">Max_city</span><span class="p">,</span><span class="w"> </span><span class="n">Min_city</span><span class="p" data-group-id="5087476061-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5087476061-8">(</span><span class="n">Converted_List</span><span class="p" data-group-id="5087476061-8">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">print_max_and_min</span><span class="p" data-group-id="5087476061-9">(</span><span class="n">Max_city</span><span class="p">,</span><span class="w"> </span><span class="n">Min_city</span><span class="p" data-group-id="5087476061-9">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5087476061-10">(</span><span class="p" data-group-id="5087476061-11">[</span><span class="p" data-group-id="5087476061-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087476061-13">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5087476061-13">}</span><span class="p" data-group-id="5087476061-12">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5087476061-11">]</span><span class="p" data-group-id="5087476061-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5087476061-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087476061-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087476061-16">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="5087476061-16">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="5087476061-15">}</span><span class="p" data-group-id="5087476061-14">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5087476061-17">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5087476061-18">(</span><span class="n">Rest</span><span class="p" data-group-id="5087476061-18">)</span><span class="p" data-group-id="5087476061-17">]</span><span class="p">;</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5087476061-19">(</span><span class="p" data-group-id="5087476061-20">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5087476061-20">]</span><span class="p" data-group-id="5087476061-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5087476061-21">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5087476061-22">(</span><span class="n">Rest</span><span class="p" data-group-id="5087476061-22">)</span><span class="p" data-group-id="5087476061-21">]</span><span class="p">;</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5087476061-23">(</span><span class="p" data-group-id="5087476061-24">[</span><span class="p" data-group-id="5087476061-24">]</span><span class="p" data-group-id="5087476061-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5087476061-25">[</span><span class="p" data-group-id="5087476061-25">]</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="5087476061-26">(</span><span class="p" data-group-id="5087476061-27">[</span><span class="p" data-group-id="5087476061-28">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087476061-29">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5087476061-29">}</span><span class="p" data-group-id="5087476061-28">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5087476061-27">]</span><span class="p" data-group-id="5087476061-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5087476061-30">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087476061-31">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5087476061-31">]</span><span class="p" data-group-id="5087476061-30">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="5087476061-32">(</span><span class="n">Rest</span><span class="p" data-group-id="5087476061-32">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="5087476061-33">(</span><span class="p" data-group-id="5087476061-34">[</span><span class="p" data-group-id="5087476061-34">]</span><span class="p" data-group-id="5087476061-33">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="5793119602-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="5793119602-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Converted_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5793119602-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="5793119602-5">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="5793119602-6">(</span><span class="n">Converted_List</span><span class="p" data-group-id="5793119602-6">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5793119602-7">{</span><span class="n">Max_city</span><span class="p">,</span><span class="w"> </span><span class="n">Min_city</span><span class="p" data-group-id="5793119602-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5793119602-8">(</span><span class="n">Converted_List</span><span class="p" data-group-id="5793119602-8">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">print_max_and_min</span><span class="p" data-group-id="5793119602-9">(</span><span class="n">Max_city</span><span class="p">,</span><span class="w"> </span><span class="n">Min_city</span><span class="p" data-group-id="5793119602-9">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5793119602-10">(</span><span class="p" data-group-id="5793119602-11">[</span><span class="p" data-group-id="5793119602-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5793119602-13">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5793119602-13">}</span><span class="p" data-group-id="5793119602-12">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5793119602-11">]</span><span class="p" data-group-id="5793119602-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5793119602-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5793119602-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5793119602-16">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="5793119602-16">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="5793119602-15">}</span><span class="p" data-group-id="5793119602-14">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5793119602-17">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5793119602-18">(</span><span class="n">Rest</span><span class="p" data-group-id="5793119602-18">)</span><span class="p" data-group-id="5793119602-17">]</span><span class="p">;</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5793119602-19">(</span><span class="p" data-group-id="5793119602-20">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5793119602-20">]</span><span class="p" data-group-id="5793119602-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5793119602-21">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5793119602-22">(</span><span class="n">Rest</span><span class="p" data-group-id="5793119602-22">)</span><span class="p" data-group-id="5793119602-21">]</span><span class="p">;</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5793119602-23">(</span><span class="p" data-group-id="5793119602-24">[</span><span class="p" data-group-id="5793119602-24">]</span><span class="p" data-group-id="5793119602-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5793119602-25">[</span><span class="p" data-group-id="5793119602-25">]</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="5793119602-26">(</span><span class="p" data-group-id="5793119602-27">[</span><span class="p" data-group-id="5793119602-28">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5793119602-29">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5793119602-29">}</span><span class="p" data-group-id="5793119602-28">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5793119602-27">]</span><span class="p" data-group-id="5793119602-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5793119602-30">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5793119602-31">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5793119602-31">]</span><span class="p" data-group-id="5793119602-30">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="5793119602-32">(</span><span class="n">Rest</span><span class="p" data-group-id="5793119602-32">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="5793119602-33">(</span><span class="p" data-group-id="5793119602-34">[</span><span class="p" data-group-id="5793119602-34">]</span><span class="p" data-group-id="5793119602-33">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5087476061-35">(</span><span class="p" data-group-id="5087476061-36">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5087476061-36">]</span><span class="p" data-group-id="5087476061-35">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5087476061-37">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="n">City</span><span class="p" data-group-id="5087476061-37">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5793119602-35">(</span><span class="p" data-group-id="5793119602-36">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5793119602-36">]</span><span class="p" data-group-id="5793119602-35">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5793119602-37">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="n">City</span><span class="p" data-group-id="5793119602-37">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5087476061-38">(</span><span class="p" data-group-id="5087476061-39">[</span><span class="p" data-group-id="5087476061-40">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087476061-41">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5087476061-41">}</span><span class="p" data-group-id="5087476061-40">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5087476061-39">]</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="5087476061-42">{</span><span class="n">Max_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087476061-43">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_Temp</span><span class="p" data-group-id="5087476061-43">}</span><span class="p" data-group-id="5087476061-42">}</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="5087476061-44">{</span><span class="n">Min_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087476061-45">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_Temp</span><span class="p" data-group-id="5087476061-45">}</span><span class="p" data-group-id="5087476061-44">}</span><span class="p" data-group-id="5087476061-38">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5793119602-38">(</span><span class="p" data-group-id="5793119602-39">[</span><span class="p" data-group-id="5793119602-40">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5793119602-41">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5793119602-41">}</span><span class="p" data-group-id="5793119602-40">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5793119602-39">]</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="5793119602-42">{</span><span class="n">Max_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5793119602-43">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_Temp</span><span class="p" data-group-id="5793119602-43">}</span><span class="p" data-group-id="5793119602-42">}</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="5793119602-44">{</span><span class="n">Min_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5793119602-45">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_Temp</span><span class="p" data-group-id="5793119602-45">}</span><span class="p" data-group-id="5793119602-44">}</span><span class="p" data-group-id="5793119602-38">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">Temp</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Max_Temp</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Max_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5087476061-46">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087476061-47">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5087476061-47">}</span><span class="p" data-group-id="5087476061-46">}</span><span class="p">;</span><span class="w">           </span><span class="c1">% Change</span><span class="w">
│ │ │ +            </span><span class="n">Max_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5793119602-46">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5793119602-47">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5793119602-47">}</span><span class="p" data-group-id="5793119602-46">}</span><span class="p">;</span><span class="w">           </span><span class="c1">% Change</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Max_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5087476061-48">{</span><span class="n">Max_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087476061-49">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_Temp</span><span class="p" data-group-id="5087476061-49">}</span><span class="p" data-group-id="5087476061-48">}</span><span class="w"> </span><span class="c1">% Unchanged</span><span class="w">
│ │ │ +            </span><span class="n">Max_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5793119602-48">{</span><span class="n">Max_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5793119602-49">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_Temp</span><span class="p" data-group-id="5793119602-49">}</span><span class="p" data-group-id="5793119602-48">}</span><span class="w"> </span><span class="c1">% Unchanged</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │           </span><span class="n">Temp</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Min_Temp</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Min_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5087476061-50">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087476061-51">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5087476061-51">}</span><span class="p" data-group-id="5087476061-50">}</span><span class="p">;</span><span class="w">           </span><span class="c1">% Change</span><span class="w">
│ │ │ +            </span><span class="n">Min_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5793119602-50">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5793119602-51">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5793119602-51">}</span><span class="p" data-group-id="5793119602-50">}</span><span class="p">;</span><span class="w">           </span><span class="c1">% Change</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Min_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5087476061-52">{</span><span class="n">Min_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087476061-53">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_Temp</span><span class="p" data-group-id="5087476061-53">}</span><span class="p" data-group-id="5087476061-52">}</span><span class="w"> </span><span class="c1">% Unchanged</span><span class="w">
│ │ │ +            </span><span class="n">Min_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5793119602-52">{</span><span class="n">Min_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5793119602-53">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_Temp</span><span class="p" data-group-id="5793119602-53">}</span><span class="p" data-group-id="5793119602-52">}</span><span class="w"> </span><span class="c1">% Unchanged</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5087476061-54">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="5087476061-54">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5793119602-54">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="5793119602-54">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5087476061-55">(</span><span class="p" data-group-id="5087476061-56">[</span><span class="p" data-group-id="5087476061-56">]</span><span class="p">,</span><span class="w"> </span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="5087476061-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5087476061-57">{</span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="5087476061-57">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5793119602-55">(</span><span class="p" data-group-id="5793119602-56">[</span><span class="p" data-group-id="5793119602-56">]</span><span class="p">,</span><span class="w"> </span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="5793119602-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5793119602-57">{</span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="5793119602-57">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">print_max_and_min</span><span class="p" data-group-id="5087476061-58">(</span><span class="p" data-group-id="5087476061-59">{</span><span class="n">Max_name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087476061-60">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_temp</span><span class="p" data-group-id="5087476061-60">}</span><span class="p" data-group-id="5087476061-59">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087476061-61">{</span><span class="n">Min_name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087476061-62">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_temp</span><span class="p" data-group-id="5087476061-62">}</span><span class="p" data-group-id="5087476061-61">}</span><span class="p" data-group-id="5087476061-58">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5087476061-63">(</span><span class="s">&quot;Max temperature was </span><span class="si">~w</span><span class="s"> c in </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087476061-64">[</span><span class="n">Max_temp</span><span class="p">,</span><span class="w"> </span><span class="n">Max_name</span><span class="p" data-group-id="5087476061-64">]</span><span class="p" data-group-id="5087476061-63">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5087476061-65">(</span><span class="s">&quot;Min temperature was </span><span class="si">~w</span><span class="s"> c in </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087476061-66">[</span><span class="n">Min_temp</span><span class="p">,</span><span class="w"> </span><span class="n">Min_name</span><span class="p" data-group-id="5087476061-66">]</span><span class="p" data-group-id="5087476061-65">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">58&gt; </span><span class="nf">c</span><span class="p" data-group-id="0051789467-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="0051789467-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0051789467-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut7</span><span class="p" data-group-id="0051789467-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">59&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="0051789467-3">(</span><span class="p" data-group-id="0051789467-4">[</span><span class="p" data-group-id="0051789467-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0051789467-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="0051789467-6">}</span><span class="p" data-group-id="0051789467-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0051789467-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0051789467-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="0051789467-8">}</span><span class="p" data-group-id="0051789467-7">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0051789467-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0051789467-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="0051789467-10">}</span><span class="p" data-group-id="0051789467-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0051789467-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0051789467-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="0051789467-12">}</span><span class="p" data-group-id="0051789467-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0051789467-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0051789467-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="0051789467-14">}</span><span class="p" data-group-id="0051789467-13">}</span><span class="p" data-group-id="0051789467-4">]</span><span class="p" data-group-id="0051789467-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">print_max_and_min</span><span class="p" data-group-id="5793119602-58">(</span><span class="p" data-group-id="5793119602-59">{</span><span class="n">Max_name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5793119602-60">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_temp</span><span class="p" data-group-id="5793119602-60">}</span><span class="p" data-group-id="5793119602-59">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5793119602-61">{</span><span class="n">Min_name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5793119602-62">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_temp</span><span class="p" data-group-id="5793119602-62">}</span><span class="p" data-group-id="5793119602-61">}</span><span class="p" data-group-id="5793119602-58">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5793119602-63">(</span><span class="s">&quot;Max temperature was </span><span class="si">~w</span><span class="s"> c in </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5793119602-64">[</span><span class="n">Max_temp</span><span class="p">,</span><span class="w"> </span><span class="n">Max_name</span><span class="p" data-group-id="5793119602-64">]</span><span class="p" data-group-id="5793119602-63">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5793119602-65">(</span><span class="s">&quot;Min temperature was </span><span class="si">~w</span><span class="s"> c in </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5793119602-66">[</span><span class="n">Min_temp</span><span class="p">,</span><span class="w"> </span><span class="n">Min_name</span><span class="p" data-group-id="5793119602-66">]</span><span class="p" data-group-id="5793119602-65">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">58&gt; </span><span class="nf">c</span><span class="p" data-group-id="5388623483-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="5388623483-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5388623483-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut7</span><span class="p" data-group-id="5388623483-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">59&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="5388623483-3">(</span><span class="p" data-group-id="5388623483-4">[</span><span class="p" data-group-id="5388623483-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5388623483-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="5388623483-6">}</span><span class="p" data-group-id="5388623483-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5388623483-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5388623483-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="5388623483-8">}</span><span class="p" data-group-id="5388623483-7">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5388623483-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5388623483-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="5388623483-10">}</span><span class="p" data-group-id="5388623483-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5388623483-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5388623483-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="5388623483-12">}</span><span class="p" data-group-id="5388623483-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5388623483-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5388623483-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="5388623483-14">}</span><span class="p" data-group-id="5388623483-13">}</span><span class="p" data-group-id="5388623483-4">]</span><span class="p" data-group-id="5388623483-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">moscow</span><span class="w">          </span><span class="o">-</span><span class="mi">10</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">cape_town</span><span class="w">       </span><span class="mf">21.11111111111111</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">stockholm</span><span class="w">       </span><span class="o">-</span><span class="mi">4</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">paris</span><span class="w">           </span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">london</span><span class="w">          </span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="n">Max</span><span class="w"> </span><span class="ss">temperature</span><span class="w"> </span><span class="ss">was</span><span class="w"> </span><span class="mf">21.11111111111111</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">cape_town</span><span class="w">
│ │ │  </span><span class="n">Min</span><span class="w"> </span><span class="ss">temperature</span><span class="w"> </span><span class="ss">was</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">moscow</span><span class="w">
│ │ │ @@ -773,88 +773,88 @@
│ │ │          </span><span class="n">Action</span><span class="w"> </span><span class="mi">4</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>Notice that there is no <code class="inline">;</code> before <code class="inline">end</code>. Conditions do the same as guards, that
│ │ │  is, tests that succeed or fail. Erlang starts at the top and tests until it
│ │ │  finds a condition that succeeds. Then it evaluates (performs) the action
│ │ │  following the condition and ignores all other conditions and actions before the
│ │ │  <code class="inline">end</code>. If no condition matches, a run-time failure occurs. A condition that
│ │ │  always succeeds is the atom <code class="inline">true</code>. This is often used last in an <code class="inline">if</code>, meaning,
│ │ │ -do the action following the <code class="inline">true</code> if all other conditions have failed.</p><p>The following is a short program to show the workings of <code class="inline">if</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2071570747-1">(</span><span class="ss">tut9</span><span class="p" data-group-id="2071570747-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2071570747-2">(</span><span class="p" data-group-id="2071570747-3">[</span><span class="ss">test_if</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2071570747-3">]</span><span class="p" data-group-id="2071570747-2">)</span><span class="p">.</span><span class="w">
│ │ │ +do the action following the <code class="inline">true</code> if all other conditions have failed.</p><p>The following is a short program to show the workings of <code class="inline">if</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8645248328-1">(</span><span class="ss">tut9</span><span class="p" data-group-id="8645248328-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8645248328-2">(</span><span class="p" data-group-id="8645248328-3">[</span><span class="ss">test_if</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8645248328-3">]</span><span class="p" data-group-id="8645248328-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">test_if</span><span class="p" data-group-id="2071570747-4">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="2071570747-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">test_if</span><span class="p" data-group-id="8645248328-4">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="8645248328-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2071570747-5">(</span><span class="s">&quot;A == 5</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2071570747-6">[</span><span class="p" data-group-id="2071570747-6">]</span><span class="p" data-group-id="2071570747-5">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8645248328-5">(</span><span class="s">&quot;A == 5</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8645248328-6">[</span><span class="p" data-group-id="8645248328-6">]</span><span class="p" data-group-id="8645248328-5">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="ss">a_equals_5</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">6</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2071570747-7">(</span><span class="s">&quot;B == 6</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2071570747-8">[</span><span class="p" data-group-id="2071570747-8">]</span><span class="p" data-group-id="2071570747-7">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8645248328-7">(</span><span class="s">&quot;B == 6</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8645248328-8">[</span><span class="p" data-group-id="8645248328-8">]</span><span class="p" data-group-id="8645248328-7">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="ss">b_equals_6</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">                      </span><span class="c1">%That is A equals 2 and B equals 3</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2071570747-9">(</span><span class="s">&quot;A == 2, B == 3</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2071570747-10">[</span><span class="p" data-group-id="2071570747-10">]</span><span class="p" data-group-id="2071570747-9">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8645248328-9">(</span><span class="s">&quot;A == 2, B == 3</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8645248328-10">[</span><span class="p" data-group-id="8645248328-10">]</span><span class="p" data-group-id="8645248328-9">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="ss">a_equals_2_b_equals_3</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">7</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">                     </span><span class="c1">%That is A equals 1 or B equals 7</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2071570747-11">(</span><span class="s">&quot;A == 1 ; B == 7</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2071570747-12">[</span><span class="p" data-group-id="2071570747-12">]</span><span class="p" data-group-id="2071570747-11">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8645248328-11">(</span><span class="s">&quot;A == 1 ; B == 7</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8645248328-12">[</span><span class="p" data-group-id="8645248328-12">]</span><span class="p" data-group-id="8645248328-11">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="ss">a_equals_1_or_b_equals_7</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Testing this program gives:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">60&gt; </span><span class="nf">c</span><span class="p" data-group-id="3555012261-1">(</span><span class="ss">tut9</span><span class="p" data-group-id="3555012261-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3555012261-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut9</span><span class="p" data-group-id="3555012261-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">61&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="3555012261-3">(</span><span class="mi">5</span><span class="p">,</span><span class="mi">33</span><span class="p" data-group-id="3555012261-3">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Testing this program gives:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">60&gt; </span><span class="nf">c</span><span class="p" data-group-id="9016093609-1">(</span><span class="ss">tut9</span><span class="p" data-group-id="9016093609-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9016093609-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut9</span><span class="p" data-group-id="9016093609-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">61&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="9016093609-3">(</span><span class="mi">5</span><span class="p">,</span><span class="mi">33</span><span class="p" data-group-id="9016093609-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │  </span><span class="ss">a_equals_5</span><span class="w">
│ │ │ -</span><span class="gp unselectable">62&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="3555012261-4">(</span><span class="mi">33</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3555012261-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">62&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="9016093609-4">(</span><span class="mi">33</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="9016093609-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">6</span><span class="w">
│ │ │  </span><span class="ss">b_equals_6</span><span class="w">
│ │ │ -</span><span class="gp unselectable">63&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="3555012261-5">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3555012261-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">63&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="9016093609-5">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="9016093609-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="w">
│ │ │  </span><span class="ss">a_equals_2_b_equals_3</span><span class="w">
│ │ │ -</span><span class="gp unselectable">64&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="3555012261-6">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="3555012261-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">64&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="9016093609-6">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="9016093609-6">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">7</span><span class="w">
│ │ │  </span><span class="ss">a_equals_1_or_b_equals_7</span><span class="w">
│ │ │ -</span><span class="gp unselectable">65&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="3555012261-7">(</span><span class="mi">33</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p" data-group-id="3555012261-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">65&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="9016093609-7">(</span><span class="mi">33</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p" data-group-id="9016093609-7">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">7</span><span class="w">
│ │ │  </span><span class="ss">a_equals_1_or_b_equals_7</span><span class="w">
│ │ │ -</span><span class="gp unselectable">66&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="3555012261-8">(</span><span class="mi">33</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="3555012261-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">66&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="9016093609-8">(</span><span class="mi">33</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="9016093609-8">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no true branch found when evaluating an if expression
│ │ │       in function  tut9:test_if/2 (tut9.erl, line 5)</span></code></pre><p>Notice that <code class="inline">tut9:test_if(33,33)</code> does not cause any condition to succeed. This
│ │ │  leads to the run time error <code class="inline">if_clause</code>, here nicely formatted by the shell. See
│ │ │  <a href="../../doc/system/expressions.html">Guard Sequences</a> for details of the many guard tests
│ │ │  available.</p><p><code class="inline">case</code> is another construct in Erlang. Recall that the <code class="inline">convert_length</code> function
│ │ │ -was written as:</p><pre><code class="makeup erlang" translate="no"><span class="nf">convert_length</span><span class="p" data-group-id="2001147343-1">(</span><span class="p" data-group-id="2001147343-2">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="2001147343-2">}</span><span class="p" data-group-id="2001147343-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2001147343-3">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="2001147343-3">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">convert_length</span><span class="p" data-group-id="2001147343-4">(</span><span class="p" data-group-id="2001147343-5">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2001147343-5">}</span><span class="p" data-group-id="2001147343-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2001147343-6">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="2001147343-6">}</span><span class="p">.</span></code></pre><p>The same program can also be written as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9760051130-1">(</span><span class="ss">tut10</span><span class="p" data-group-id="9760051130-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9760051130-2">(</span><span class="p" data-group-id="9760051130-3">[</span><span class="ss">convert_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9760051130-3">]</span><span class="p" data-group-id="9760051130-2">)</span><span class="p">.</span><span class="w">
│ │ │ +was written as:</p><pre><code class="makeup erlang" translate="no"><span class="nf">convert_length</span><span class="p" data-group-id="0225988220-1">(</span><span class="p" data-group-id="0225988220-2">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0225988220-2">}</span><span class="p" data-group-id="0225988220-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0225988220-3">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="0225988220-3">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">convert_length</span><span class="p" data-group-id="0225988220-4">(</span><span class="p" data-group-id="0225988220-5">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0225988220-5">}</span><span class="p" data-group-id="0225988220-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0225988220-6">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="0225988220-6">}</span><span class="p">.</span></code></pre><p>The same program can also be written as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9237251140-1">(</span><span class="ss">tut10</span><span class="p" data-group-id="9237251140-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9237251140-2">(</span><span class="p" data-group-id="9237251140-3">[</span><span class="ss">convert_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9237251140-3">]</span><span class="p" data-group-id="9237251140-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">convert_length</span><span class="p" data-group-id="9760051130-4">(</span><span class="n">Length</span><span class="p" data-group-id="9760051130-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">convert_length</span><span class="p" data-group-id="9237251140-4">(</span><span class="n">Length</span><span class="p" data-group-id="9237251140-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9760051130-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9760051130-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="9760051130-6">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="9760051130-6">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9760051130-7">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9760051130-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="9760051130-8">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="9760051130-8">}</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">67&gt; </span><span class="nf">c</span><span class="p" data-group-id="1212590011-1">(</span><span class="ss">tut10</span><span class="p" data-group-id="1212590011-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1212590011-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut10</span><span class="p" data-group-id="1212590011-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">68&gt; </span><span class="nc">tut10</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="1212590011-3">(</span><span class="p" data-group-id="1212590011-4">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p" data-group-id="1212590011-4">}</span><span class="p" data-group-id="1212590011-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1212590011-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="mf">15.24</span><span class="p" data-group-id="1212590011-5">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">69&gt; </span><span class="nc">tut10</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="1212590011-6">(</span><span class="p" data-group-id="1212590011-7">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="mf">2.5</span><span class="p" data-group-id="1212590011-7">}</span><span class="p" data-group-id="1212590011-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1212590011-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="mf">0.984251968503937</span><span class="p" data-group-id="1212590011-8">}</span></code></pre><p>Both <code class="inline">case</code> and <code class="inline">if</code> have <em>return values</em>, that is, in the above example <code class="inline">case</code>
│ │ │ +        </span><span class="p" data-group-id="9237251140-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9237251140-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="9237251140-6">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="9237251140-6">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9237251140-7">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9237251140-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="9237251140-8">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="9237251140-8">}</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">67&gt; </span><span class="nf">c</span><span class="p" data-group-id="9639857003-1">(</span><span class="ss">tut10</span><span class="p" data-group-id="9639857003-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9639857003-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut10</span><span class="p" data-group-id="9639857003-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">68&gt; </span><span class="nc">tut10</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="9639857003-3">(</span><span class="p" data-group-id="9639857003-4">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p" data-group-id="9639857003-4">}</span><span class="p" data-group-id="9639857003-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9639857003-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="mf">15.24</span><span class="p" data-group-id="9639857003-5">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">69&gt; </span><span class="nc">tut10</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="9639857003-6">(</span><span class="p" data-group-id="9639857003-7">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="mf">2.5</span><span class="p" data-group-id="9639857003-7">}</span><span class="p" data-group-id="9639857003-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9639857003-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="mf">0.984251968503937</span><span class="p" data-group-id="9639857003-8">}</span></code></pre><p>Both <code class="inline">case</code> and <code class="inline">if</code> have <em>return values</em>, that is, in the above example <code class="inline">case</code>
│ │ │  returned either <code class="inline">{inch,X/2.54}</code> or <code class="inline">{centimeter,Y*2.54}</code>. The behaviour of
│ │ │  <code class="inline">case</code> can also be modified by using guards. The following example clarifies
│ │ │  this. It tells us the length of a month, given the year. The year must be known,
│ │ │ -since February has 29 days in a leap year.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6398561192-1">(</span><span class="ss">tut11</span><span class="p" data-group-id="6398561192-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6398561192-2">(</span><span class="p" data-group-id="6398561192-3">[</span><span class="ss">month_length</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6398561192-3">]</span><span class="p" data-group-id="6398561192-2">)</span><span class="p">.</span><span class="w">
│ │ │ +since February has 29 days in a leap year.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2307276037-1">(</span><span class="ss">tut11</span><span class="p" data-group-id="2307276037-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2307276037-2">(</span><span class="p" data-group-id="2307276037-3">[</span><span class="ss">month_length</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2307276037-3">]</span><span class="p" data-group-id="2307276037-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">month_length</span><span class="p" data-group-id="6398561192-4">(</span><span class="n">Year</span><span class="p">,</span><span class="w"> </span><span class="n">Month</span><span class="p" data-group-id="6398561192-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">month_length</span><span class="p" data-group-id="2307276037-4">(</span><span class="n">Year</span><span class="p">,</span><span class="w"> </span><span class="n">Month</span><span class="p" data-group-id="2307276037-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% All years divisible by 400 are leap</span><span class="w">
│ │ │      </span><span class="c1">%% Years divisible by 100 are not leap (except the 400 rule above)</span><span class="w">
│ │ │      </span><span class="c1">%% Years divisible by 4 are leap (except the 100 rule above)</span><span class="w">
│ │ │      </span><span class="n">Leap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">if</span><span class="w">
│ │ │ -        </span><span class="nf">trunc</span><span class="p" data-group-id="6398561192-5">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="p" data-group-id="6398561192-5">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nf">trunc</span><span class="p" data-group-id="2307276037-5">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="p" data-group-id="2307276037-5">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">leap</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="nf">trunc</span><span class="p" data-group-id="6398561192-6">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">100</span><span class="p" data-group-id="6398561192-6">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">100</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nf">trunc</span><span class="p" data-group-id="2307276037-6">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">100</span><span class="p" data-group-id="2307276037-6">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">100</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">not_leap</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="nf">trunc</span><span class="p" data-group-id="6398561192-7">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="6398561192-7">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">4</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nf">trunc</span><span class="p" data-group-id="2307276037-7">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="2307276037-7">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">4</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">leap</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">not_leap</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Month</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">sep</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">30</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">apr</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">30</span><span class="p">;</span><span class="w">
│ │ │ @@ -865,152 +865,152 @@
│ │ │          </span><span class="ss">jan</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">mar</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">may</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">jul</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">aug</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">oct</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">dec</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">70&gt; </span><span class="nf">c</span><span class="p" data-group-id="2409809453-1">(</span><span class="ss">tut11</span><span class="p" data-group-id="2409809453-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2409809453-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut11</span><span class="p" data-group-id="2409809453-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">71&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="2409809453-3">(</span><span class="mi">2004</span><span class="p">,</span><span class="w"> </span><span class="ss">feb</span><span class="p" data-group-id="2409809453-3">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">70&gt; </span><span class="nf">c</span><span class="p" data-group-id="2507155576-1">(</span><span class="ss">tut11</span><span class="p" data-group-id="2507155576-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2507155576-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut11</span><span class="p" data-group-id="2507155576-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">71&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="2507155576-3">(</span><span class="mi">2004</span><span class="p">,</span><span class="w"> </span><span class="ss">feb</span><span class="p" data-group-id="2507155576-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">29</span><span class="w">
│ │ │ -</span><span class="gp unselectable">72&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="2409809453-4">(</span><span class="mi">2003</span><span class="p">,</span><span class="w"> </span><span class="ss">feb</span><span class="p" data-group-id="2409809453-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">72&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="2507155576-4">(</span><span class="mi">2003</span><span class="p">,</span><span class="w"> </span><span class="ss">feb</span><span class="p" data-group-id="2507155576-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">28</span><span class="w">
│ │ │ -</span><span class="gp unselectable">73&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="2409809453-5">(</span><span class="mi">1947</span><span class="p">,</span><span class="w"> </span><span class="ss">aug</span><span class="p" data-group-id="2409809453-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">73&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="2507155576-5">(</span><span class="mi">1947</span><span class="p">,</span><span class="w"> </span><span class="ss">aug</span><span class="p" data-group-id="2507155576-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">31</span></code></pre><h2 id="built-in-functions-bifs" class="section-heading">
│ │ │    <a href="#built-in-functions-bifs" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Built-In Functions (BIFs)</span>
│ │ │  </h2>
│ │ │  <p>BIFs are functions that for some reason are built-in to the Erlang virtual
│ │ │  machine. BIFs often implement functionality that is impossible or is too
│ │ │  inefficient to implement in Erlang. Some BIFs can be called using the function
│ │ │  name only, but by default they belong to the <code class="inline">erlang</code> module. For example,
│ │ │  the call to the BIF <code class="inline">trunc</code> below is equivalent to a call to <code class="inline">erlang:trunc</code>.</p><p>As shown, first it is checked if a year is leap. If a year is divisible by 400,
│ │ │  it is a leap year. To determine this, first divide the year by 400 and use the
│ │ │  BIF <code class="inline">trunc</code> (more about this later) to cut off any decimals. Then multiply by
│ │ │  400 again and see if the same value is returned again. For example, year 2004:</p><pre><code class="makeup erlang" translate="no"><span class="mi">2004</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">5.01</span><span class="w">
│ │ │ -</span><span class="nf">trunc</span><span class="p" data-group-id="5368580822-1">(</span><span class="mf">5.01</span><span class="p" data-group-id="5368580822-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │ +</span><span class="nf">trunc</span><span class="p" data-group-id="3741996678-1">(</span><span class="mf">5.01</span><span class="p" data-group-id="3741996678-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │  </span><span class="mi">5</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2000</span></code></pre><p>2000 is not the same as 2004, so 2004 is not divisible by 400. Year 2000:</p><pre><code class="makeup erlang" translate="no"><span class="mi">2000</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">5.0</span><span class="w">
│ │ │ -</span><span class="nf">trunc</span><span class="p" data-group-id="1892738183-1">(</span><span class="mf">5.0</span><span class="p" data-group-id="1892738183-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │ +</span><span class="nf">trunc</span><span class="p" data-group-id="1018966841-1">(</span><span class="mf">5.0</span><span class="p" data-group-id="1018966841-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │  </span><span class="mi">5</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2000</span></code></pre><p>That is, a leap year. The next two <code class="inline">trunc</code>-tests evaluate if the year is
│ │ │  divisible by 100 or 4 in the same way. The first <code class="inline">if</code> returns <code class="inline">leap</code> or
│ │ │  <code class="inline">not_leap</code>, which ends up in the variable <code class="inline">Leap</code>. This variable is used in the
│ │ │  guard for <code class="inline">feb</code> in the following <code class="inline">case</code> that tells us how long the month is.</p><p>This example showed the use of <code class="inline">trunc</code>. It is easier to use the Erlang operator
│ │ │  <code class="inline">rem</code> that gives the remainder after division, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">74&gt; </span><span class="mi">2004</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">400</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">4</span></code></pre><p>So instead of writing:</p><pre><code class="makeup erlang" translate="no"><span class="nf">trunc</span><span class="p" data-group-id="5355228005-1">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="p" data-group-id="5355228005-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="mi">4</span></code></pre><p>So instead of writing:</p><pre><code class="makeup erlang" translate="no"><span class="nf">trunc</span><span class="p" data-group-id="6983560344-1">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="p" data-group-id="6983560344-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">leap</span><span class="p">;</span></code></pre><p>it can be written:</p><pre><code class="makeup erlang" translate="no"><span class="n">Year</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">leap</span><span class="p">;</span></code></pre><p>There are many other BIFs such as <code class="inline">trunc</code>. Only a few BIFs can be used in
│ │ │  guards, and you cannot use functions you have defined yourself in guards. (see
│ │ │  <a href="../../doc/system/expressions.html">Guard Sequences</a>) (For advanced readers: This is to
│ │ │  ensure that guards do not have side effects.) Let us play with a few of these
│ │ │ -functions in the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">75&gt; </span><span class="nf">trunc</span><span class="p" data-group-id="7482977678-1">(</span><span class="mf">5.6</span><span class="p" data-group-id="7482977678-1">)</span><span class="p">.</span><span class="w">
│ │ │ +functions in the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">75&gt; </span><span class="nf">trunc</span><span class="p" data-group-id="2670085138-1">(</span><span class="mf">5.6</span><span class="p" data-group-id="2670085138-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">5</span><span class="w">
│ │ │ -</span><span class="gp unselectable">76&gt; </span><span class="nf">round</span><span class="p" data-group-id="7482977678-2">(</span><span class="mf">5.6</span><span class="p" data-group-id="7482977678-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">76&gt; </span><span class="nf">round</span><span class="p" data-group-id="2670085138-2">(</span><span class="mf">5.6</span><span class="p" data-group-id="2670085138-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">6</span><span class="w">
│ │ │ -</span><span class="gp unselectable">77&gt; </span><span class="nf">length</span><span class="p" data-group-id="7482977678-3">(</span><span class="p" data-group-id="7482977678-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="7482977678-4">]</span><span class="p" data-group-id="7482977678-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">77&gt; </span><span class="nf">length</span><span class="p" data-group-id="2670085138-3">(</span><span class="p" data-group-id="2670085138-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="2670085138-4">]</span><span class="p" data-group-id="2670085138-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4</span><span class="w">
│ │ │ -</span><span class="gp unselectable">78&gt; </span><span class="nf">float</span><span class="p" data-group-id="7482977678-5">(</span><span class="mi">5</span><span class="p" data-group-id="7482977678-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">78&gt; </span><span class="nf">float</span><span class="p" data-group-id="2670085138-5">(</span><span class="mi">5</span><span class="p" data-group-id="2670085138-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">5.0</span><span class="w">
│ │ │ -</span><span class="gp unselectable">79&gt; </span><span class="nf">is_atom</span><span class="p" data-group-id="7482977678-6">(</span><span class="ss">hello</span><span class="p" data-group-id="7482977678-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">79&gt; </span><span class="nf">is_atom</span><span class="p" data-group-id="2670085138-6">(</span><span class="ss">hello</span><span class="p" data-group-id="2670085138-6">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="gp unselectable">80&gt; </span><span class="nf">is_atom</span><span class="p" data-group-id="7482977678-7">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="7482977678-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">80&gt; </span><span class="nf">is_atom</span><span class="p" data-group-id="2670085138-7">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="2670085138-7">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span><span class="w">
│ │ │ -</span><span class="gp unselectable">81&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="7482977678-8">(</span><span class="p" data-group-id="7482977678-9">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7482977678-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p" data-group-id="7482977678-10">}</span><span class="p" data-group-id="7482977678-9">}</span><span class="p" data-group-id="7482977678-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">81&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="2670085138-8">(</span><span class="p" data-group-id="2670085138-9">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2670085138-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p" data-group-id="2670085138-10">}</span><span class="p" data-group-id="2670085138-9">}</span><span class="p" data-group-id="2670085138-8">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="gp unselectable">82&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="7482977678-11">(</span><span class="p" data-group-id="7482977678-12">[</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7482977678-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p" data-group-id="7482977678-13">}</span><span class="p" data-group-id="7482977678-12">]</span><span class="p" data-group-id="7482977678-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">82&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="2670085138-11">(</span><span class="p" data-group-id="2670085138-12">[</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2670085138-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p" data-group-id="2670085138-13">}</span><span class="p" data-group-id="2670085138-12">]</span><span class="p" data-group-id="2670085138-11">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span></code></pre><p>All of these can be used in guards. Now for some BIFs that cannot be used in
│ │ │ -guards:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">83&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="9832759905-1">(</span><span class="ss">hello</span><span class="p" data-group-id="9832759905-1">)</span><span class="p">.</span><span class="w">
│ │ │ +guards:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">83&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="1856285176-1">(</span><span class="ss">hello</span><span class="p" data-group-id="1856285176-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;hello&quot;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">84&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="9832759905-2">(</span><span class="s">&quot;goodbye&quot;</span><span class="p" data-group-id="9832759905-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">84&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="1856285176-2">(</span><span class="s">&quot;goodbye&quot;</span><span class="p" data-group-id="1856285176-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">goodbye</span><span class="w">
│ │ │ -</span><span class="gp unselectable">85&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="9832759905-3">(</span><span class="mi">22</span><span class="p" data-group-id="9832759905-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">85&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="1856285176-3">(</span><span class="mi">22</span><span class="p" data-group-id="1856285176-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;22&quot;</span></code></pre><p>These three BIFs do conversions that would be difficult (or impossible) to do in
│ │ │  Erlang.</p><h2 id="higher-order-functions-funs" class="section-heading">
│ │ │    <a href="#higher-order-functions-funs" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Higher-Order Functions (Funs)</span>
│ │ │  </h2>
│ │ │  <p>Erlang, like most modern functional programming languages, has higher-order
│ │ │ -functions. Here is an example using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">86&gt; </span><span class="n">Xf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="2833649082-1">(</span><span class="n">X</span><span class="p" data-group-id="2833649082-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +functions. Here is an example using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">86&gt; </span><span class="n">Xf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="4739510710-1">(</span><span class="n">X</span><span class="p" data-group-id="4739510710-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">5.123085357</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">87&gt; </span><span class="n">Xf</span><span class="p" data-group-id="2833649082-2">(</span><span class="mi">5</span><span class="p" data-group-id="2833649082-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">87&gt; </span><span class="n">Xf</span><span class="p" data-group-id="4739510710-2">(</span><span class="mi">5</span><span class="p" data-group-id="4739510710-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">10</span></code></pre><p>Here a function that doubles the value of a number is defined and assigned to
│ │ │  a variable. Thus <code class="inline">Xf(5)</code> returns value 10.</p><p>Two useful functions when working with lists are <code class="inline">foreach</code> and <code class="inline">map</code>, which
│ │ │ -are defined as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="3598293004-1">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3598293004-2">[</span><span class="n">First</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="3598293004-2">]</span><span class="p" data-group-id="3598293004-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Fun</span><span class="p" data-group-id="3598293004-3">(</span><span class="n">First</span><span class="p" data-group-id="3598293004-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="3598293004-4">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3598293004-4">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">foreach</span><span class="p" data-group-id="3598293004-5">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3598293004-6">[</span><span class="p" data-group-id="3598293004-6">]</span><span class="p" data-group-id="3598293004-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +are defined as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="6734049604-1">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6734049604-2">[</span><span class="n">First</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="6734049604-2">]</span><span class="p" data-group-id="6734049604-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Fun</span><span class="p" data-group-id="6734049604-3">(</span><span class="n">First</span><span class="p" data-group-id="6734049604-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="6734049604-4">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="6734049604-4">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">foreach</span><span class="p" data-group-id="6734049604-5">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6734049604-6">[</span><span class="p" data-group-id="6734049604-6">]</span><span class="p" data-group-id="6734049604-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="3598293004-7">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3598293004-8">[</span><span class="n">First</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="3598293004-8">]</span><span class="p" data-group-id="3598293004-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3598293004-9">[</span><span class="n">Fun</span><span class="p" data-group-id="3598293004-10">(</span><span class="n">First</span><span class="p" data-group-id="3598293004-10">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="3598293004-11">(</span><span class="n">Fun</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="3598293004-11">)</span><span class="p" data-group-id="3598293004-9">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="3598293004-12">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3598293004-13">[</span><span class="p" data-group-id="3598293004-13">]</span><span class="p" data-group-id="3598293004-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3598293004-14">[</span><span class="p" data-group-id="3598293004-14">]</span><span class="p">.</span></code></pre><p>These two functions are provided in the standard library module <code class="inline">lists</code>. <code class="inline">foreach</code> takes
│ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="6734049604-7">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6734049604-8">[</span><span class="n">First</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="6734049604-8">]</span><span class="p" data-group-id="6734049604-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6734049604-9">[</span><span class="n">Fun</span><span class="p" data-group-id="6734049604-10">(</span><span class="n">First</span><span class="p" data-group-id="6734049604-10">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="6734049604-11">(</span><span class="n">Fun</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="6734049604-11">)</span><span class="p" data-group-id="6734049604-9">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="6734049604-12">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6734049604-13">[</span><span class="p" data-group-id="6734049604-13">]</span><span class="p" data-group-id="6734049604-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6734049604-14">[</span><span class="p" data-group-id="6734049604-14">]</span><span class="p">.</span></code></pre><p>These two functions are provided in the standard library module <code class="inline">lists</code>. <code class="inline">foreach</code> takes
│ │ │  a list and applies a fun to every element in the list. <code class="inline">map</code> creates a new list
│ │ │  by applying a fun to every element in a list. Going back to the shell, <code class="inline">map</code> is
│ │ │ -used with a fun to add 3 to every element of a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">88&gt; </span><span class="n">Add_3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="8388781101-1">(</span><span class="n">X</span><span class="p" data-group-id="8388781101-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +used with a fun to add 3 to every element of a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">88&gt; </span><span class="n">Add_3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="5756580565-1">(</span><span class="n">X</span><span class="p" data-group-id="5756580565-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">5.123085357</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">89&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="8388781101-2">(</span><span class="n">Add_3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8388781101-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8388781101-3">]</span><span class="p" data-group-id="8388781101-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8388781101-4">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8388781101-4">]</span></code></pre><p>Let us (again) print the temperatures in a list of cities:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">90&gt; </span><span class="n">Print_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="6002144034-1">(</span><span class="p" data-group-id="6002144034-2">{</span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6002144034-3">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="6002144034-3">}</span><span class="p" data-group-id="6002144034-2">}</span><span class="p" data-group-id="6002144034-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6002144034-4">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6002144034-5">[</span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="6002144034-5">]</span><span class="p" data-group-id="6002144034-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">89&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="5756580565-2">(</span><span class="n">Add_3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5756580565-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5756580565-3">]</span><span class="p" data-group-id="5756580565-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5756580565-4">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="5756580565-4">]</span></code></pre><p>Let us (again) print the temperatures in a list of cities:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">90&gt; </span><span class="n">Print_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0179444246-1">(</span><span class="p" data-group-id="0179444246-2">{</span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0179444246-3">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0179444246-3">}</span><span class="p" data-group-id="0179444246-2">}</span><span class="p" data-group-id="0179444246-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0179444246-4">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0179444246-5">[</span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0179444246-5">]</span><span class="p" data-group-id="0179444246-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">5.123085357</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">91&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="6002144034-6">(</span><span class="n">Print_City</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6002144034-7">[</span><span class="p" data-group-id="6002144034-8">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6002144034-9">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="6002144034-9">}</span><span class="p" data-group-id="6002144034-8">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6002144034-10">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6002144034-11">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="6002144034-11">}</span><span class="p" data-group-id="6002144034-10">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6002144034-12">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6002144034-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="6002144034-13">}</span><span class="p" data-group-id="6002144034-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6002144034-14">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6002144034-15">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="6002144034-15">}</span><span class="p" data-group-id="6002144034-14">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6002144034-16">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6002144034-17">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="6002144034-17">}</span><span class="p" data-group-id="6002144034-16">}</span><span class="p" data-group-id="6002144034-7">]</span><span class="p" data-group-id="6002144034-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">91&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="0179444246-6">(</span><span class="n">Print_City</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0179444246-7">[</span><span class="p" data-group-id="0179444246-8">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0179444246-9">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="0179444246-9">}</span><span class="p" data-group-id="0179444246-8">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0179444246-10">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0179444246-11">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="0179444246-11">}</span><span class="p" data-group-id="0179444246-10">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0179444246-12">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0179444246-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="0179444246-13">}</span><span class="p" data-group-id="0179444246-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0179444246-14">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0179444246-15">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="0179444246-15">}</span><span class="p" data-group-id="0179444246-14">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0179444246-16">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0179444246-17">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="0179444246-17">}</span><span class="p" data-group-id="0179444246-16">}</span><span class="p" data-group-id="0179444246-7">]</span><span class="p" data-group-id="0179444246-6">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">moscow</span><span class="w">          </span><span class="ss">c</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="w">
│ │ │  </span><span class="ss">cape_town</span><span class="w">       </span><span class="ss">f</span><span class="w"> </span><span class="mi">70</span><span class="w">
│ │ │  </span><span class="ss">stockholm</span><span class="w">       </span><span class="ss">c</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="w">
│ │ │  </span><span class="ss">paris</span><span class="w">           </span><span class="ss">f</span><span class="w"> </span><span class="mi">28</span><span class="w">
│ │ │  </span><span class="ss">london</span><span class="w">          </span><span class="ss">f</span><span class="w"> </span><span class="mi">36</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>Let us now define a fun that can be used to go through a list of cities and
│ │ │ -temperatures and transform them all to Celsius.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9948338463-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="9948338463-1">)</span><span class="p">.</span><span class="w">
│ │ │ +temperatures and transform them all to Celsius.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4665177127-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="4665177127-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9948338463-2">(</span><span class="p" data-group-id="9948338463-3">[</span><span class="ss">convert_list_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9948338463-3">]</span><span class="p" data-group-id="9948338463-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4665177127-2">(</span><span class="p" data-group-id="4665177127-3">[</span><span class="ss">convert_list_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4665177127-3">]</span><span class="p" data-group-id="4665177127-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">convert_to_c</span><span class="p" data-group-id="9948338463-4">(</span><span class="p" data-group-id="9948338463-5">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9948338463-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9948338463-6">}</span><span class="p" data-group-id="9948338463-5">}</span><span class="p" data-group-id="9948338463-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9948338463-7">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9948338463-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="nf">trunc</span><span class="p" data-group-id="9948338463-9">(</span><span class="p" data-group-id="9948338463-10">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="9948338463-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="9948338463-9">)</span><span class="p" data-group-id="9948338463-8">}</span><span class="p" data-group-id="9948338463-7">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">convert_to_c</span><span class="p" data-group-id="9948338463-11">(</span><span class="p" data-group-id="9948338463-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9948338463-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9948338463-13">}</span><span class="p" data-group-id="9948338463-12">}</span><span class="p" data-group-id="9948338463-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9948338463-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9948338463-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9948338463-15">}</span><span class="p" data-group-id="9948338463-14">}</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="9948338463-16">(</span><span class="n">List</span><span class="p" data-group-id="9948338463-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="9948338463-17">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9948338463-17">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">92&gt; </span><span class="nc">tut13</span><span class="p">:</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7351790331-1">(</span><span class="p" data-group-id="7351790331-2">[</span><span class="p" data-group-id="7351790331-3">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7351790331-4">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="7351790331-4">}</span><span class="p" data-group-id="7351790331-3">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7351790331-5">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7351790331-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="7351790331-6">}</span><span class="p" data-group-id="7351790331-5">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7351790331-7">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7351790331-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="7351790331-8">}</span><span class="p" data-group-id="7351790331-7">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7351790331-9">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7351790331-10">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="7351790331-10">}</span><span class="p" data-group-id="7351790331-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7351790331-11">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7351790331-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="7351790331-12">}</span><span class="p" data-group-id="7351790331-11">}</span><span class="p" data-group-id="7351790331-2">]</span><span class="p" data-group-id="7351790331-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7351790331-13">[</span><span class="p" data-group-id="7351790331-14">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="7351790331-15">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="7351790331-15">}</span><span class="p" data-group-id="7351790331-14">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7351790331-16">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="7351790331-17">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">21</span><span class="p" data-group-id="7351790331-17">}</span><span class="p" data-group-id="7351790331-16">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7351790331-18">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="7351790331-19">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="7351790331-19">}</span><span class="p" data-group-id="7351790331-18">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7351790331-20">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="7351790331-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="7351790331-21">}</span><span class="p" data-group-id="7351790331-20">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7351790331-22">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="7351790331-23">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7351790331-23">}</span><span class="p" data-group-id="7351790331-22">}</span><span class="p" data-group-id="7351790331-13">]</span></code></pre><p>The <code class="inline">convert_to_c</code> function is the same as before, but here it is used as a fun:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="3395541052-1">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="3395541052-1">)</span></code></pre><p>When a function defined elsewhere is used as a fun, it can be referred to as
│ │ │ +</span><span class="nf">convert_to_c</span><span class="p" data-group-id="4665177127-4">(</span><span class="p" data-group-id="4665177127-5">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4665177127-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="4665177127-6">}</span><span class="p" data-group-id="4665177127-5">}</span><span class="p" data-group-id="4665177127-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4665177127-7">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4665177127-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="nf">trunc</span><span class="p" data-group-id="4665177127-9">(</span><span class="p" data-group-id="4665177127-10">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="4665177127-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="4665177127-9">)</span><span class="p" data-group-id="4665177127-8">}</span><span class="p" data-group-id="4665177127-7">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">convert_to_c</span><span class="p" data-group-id="4665177127-11">(</span><span class="p" data-group-id="4665177127-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4665177127-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="4665177127-13">}</span><span class="p" data-group-id="4665177127-12">}</span><span class="p" data-group-id="4665177127-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4665177127-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4665177127-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="4665177127-15">}</span><span class="p" data-group-id="4665177127-14">}</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="4665177127-16">(</span><span class="n">List</span><span class="p" data-group-id="4665177127-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="4665177127-17">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="4665177127-17">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">92&gt; </span><span class="nc">tut13</span><span class="p">:</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0407520125-1">(</span><span class="p" data-group-id="0407520125-2">[</span><span class="p" data-group-id="0407520125-3">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0407520125-4">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="0407520125-4">}</span><span class="p" data-group-id="0407520125-3">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0407520125-5">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0407520125-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="0407520125-6">}</span><span class="p" data-group-id="0407520125-5">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0407520125-7">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0407520125-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="0407520125-8">}</span><span class="p" data-group-id="0407520125-7">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0407520125-9">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0407520125-10">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="0407520125-10">}</span><span class="p" data-group-id="0407520125-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0407520125-11">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0407520125-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="0407520125-12">}</span><span class="p" data-group-id="0407520125-11">}</span><span class="p" data-group-id="0407520125-2">]</span><span class="p" data-group-id="0407520125-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0407520125-13">[</span><span class="p" data-group-id="0407520125-14">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="0407520125-15">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="0407520125-15">}</span><span class="p" data-group-id="0407520125-14">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0407520125-16">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="0407520125-17">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">21</span><span class="p" data-group-id="0407520125-17">}</span><span class="p" data-group-id="0407520125-16">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0407520125-18">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="0407520125-19">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="0407520125-19">}</span><span class="p" data-group-id="0407520125-18">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0407520125-20">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="0407520125-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="0407520125-21">}</span><span class="p" data-group-id="0407520125-20">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0407520125-22">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="0407520125-23">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0407520125-23">}</span><span class="p" data-group-id="0407520125-22">}</span><span class="p" data-group-id="0407520125-13">]</span></code></pre><p>The <code class="inline">convert_to_c</code> function is the same as before, but here it is used as a fun:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="5575405097-1">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="5575405097-1">)</span></code></pre><p>When a function defined elsewhere is used as a fun, it can be referred to as
│ │ │  <code class="inline">fun Function/Arity</code> (remember that <code class="inline">Arity</code> = number of arguments). That is
│ │ │  why <code class="inline">fun convert_to_c/1</code> can be used in the call above. As shown,
│ │ │  <code class="inline">convert_list_to_c</code> becomes much shorter and easier to understand.</p><p>The standard module <code class="inline">lists</code> also contains a function <code class="inline">sort(Fun, List)</code> where
│ │ │  <code class="inline">Fun</code> is a fun with two arguments. This fun returns <code class="inline">true</code> if the first argument
│ │ │  is less than the second argument, or else <code class="inline">false</code>. Sorting is added to the
│ │ │ -<code class="inline">convert_list_to_c</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1585646917-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="1585646917-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">convert_list_to_c</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7953626714-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="7953626714-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1585646917-2">(</span><span class="p" data-group-id="1585646917-3">[</span><span class="ss">convert_list_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1585646917-3">]</span><span class="p" data-group-id="1585646917-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7953626714-2">(</span><span class="p" data-group-id="7953626714-3">[</span><span class="ss">convert_list_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7953626714-3">]</span><span class="p" data-group-id="7953626714-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">convert_to_c</span><span class="p" data-group-id="1585646917-4">(</span><span class="p" data-group-id="1585646917-5">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1585646917-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="1585646917-6">}</span><span class="p" data-group-id="1585646917-5">}</span><span class="p" data-group-id="1585646917-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1585646917-7">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1585646917-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="nf">trunc</span><span class="p" data-group-id="1585646917-9">(</span><span class="p" data-group-id="1585646917-10">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="1585646917-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="1585646917-9">)</span><span class="p" data-group-id="1585646917-8">}</span><span class="p" data-group-id="1585646917-7">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">convert_to_c</span><span class="p" data-group-id="1585646917-11">(</span><span class="p" data-group-id="1585646917-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1585646917-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="1585646917-13">}</span><span class="p" data-group-id="1585646917-12">}</span><span class="p" data-group-id="1585646917-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1585646917-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1585646917-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="1585646917-15">}</span><span class="p" data-group-id="1585646917-14">}</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1585646917-16">(</span><span class="n">List</span><span class="p" data-group-id="1585646917-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">New_list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="1585646917-17">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="1585646917-17">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">sort</span><span class="p" data-group-id="1585646917-18">(</span><span class="nf">fun</span><span class="p" data-group-id="1585646917-19">(</span><span class="p" data-group-id="1585646917-20">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1585646917-21">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp1</span><span class="p" data-group-id="1585646917-21">}</span><span class="p" data-group-id="1585646917-20">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1585646917-22">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1585646917-23">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp2</span><span class="p" data-group-id="1585646917-23">}</span><span class="p" data-group-id="1585646917-22">}</span><span class="p" data-group-id="1585646917-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                       </span><span class="n">Temp1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Temp2</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">New_list</span><span class="p" data-group-id="1585646917-18">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">93&gt; </span><span class="nf">c</span><span class="p" data-group-id="7701854063-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="7701854063-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7701854063-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut13</span><span class="p" data-group-id="7701854063-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">94&gt; </span><span class="nc">tut13</span><span class="p">:</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7701854063-3">(</span><span class="p" data-group-id="7701854063-4">[</span><span class="p" data-group-id="7701854063-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7701854063-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="7701854063-6">}</span><span class="p" data-group-id="7701854063-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7701854063-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7701854063-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="7701854063-8">}</span><span class="p" data-group-id="7701854063-7">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7701854063-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7701854063-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="7701854063-10">}</span><span class="p" data-group-id="7701854063-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7701854063-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7701854063-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="7701854063-12">}</span><span class="p" data-group-id="7701854063-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7701854063-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7701854063-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="7701854063-14">}</span><span class="p" data-group-id="7701854063-13">}</span><span class="p" data-group-id="7701854063-4">]</span><span class="p" data-group-id="7701854063-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7701854063-15">[</span><span class="p" data-group-id="7701854063-16">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="7701854063-17">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="7701854063-17">}</span><span class="p" data-group-id="7701854063-16">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7701854063-18">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="7701854063-19">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="7701854063-19">}</span><span class="p" data-group-id="7701854063-18">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7701854063-20">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="7701854063-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="7701854063-21">}</span><span class="p" data-group-id="7701854063-20">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7701854063-22">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="7701854063-23">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7701854063-23">}</span><span class="p" data-group-id="7701854063-22">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7701854063-24">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="7701854063-25">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">21</span><span class="p" data-group-id="7701854063-25">}</span><span class="p" data-group-id="7701854063-24">}</span><span class="p" data-group-id="7701854063-15">]</span></code></pre><p>In <code class="inline">sort</code> the fun is used:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="p" data-group-id="3817394056-1">(</span><span class="p" data-group-id="3817394056-2">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3817394056-3">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp1</span><span class="p" data-group-id="3817394056-3">}</span><span class="p" data-group-id="3817394056-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3817394056-4">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3817394056-5">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp2</span><span class="p" data-group-id="3817394056-5">}</span><span class="p" data-group-id="3817394056-4">}</span><span class="p" data-group-id="3817394056-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Temp1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Temp2</span><span class="w"> </span><span class="k">end</span><span class="p">,</span></code></pre><p>Here the concept of an <em>anonymous variable</em> <code class="inline">_</code> is introduced. This is simply
│ │ │ +</span><span class="nf">convert_to_c</span><span class="p" data-group-id="7953626714-4">(</span><span class="p" data-group-id="7953626714-5">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7953626714-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7953626714-6">}</span><span class="p" data-group-id="7953626714-5">}</span><span class="p" data-group-id="7953626714-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7953626714-7">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7953626714-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="nf">trunc</span><span class="p" data-group-id="7953626714-9">(</span><span class="p" data-group-id="7953626714-10">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="7953626714-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="7953626714-9">)</span><span class="p" data-group-id="7953626714-8">}</span><span class="p" data-group-id="7953626714-7">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">convert_to_c</span><span class="p" data-group-id="7953626714-11">(</span><span class="p" data-group-id="7953626714-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7953626714-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7953626714-13">}</span><span class="p" data-group-id="7953626714-12">}</span><span class="p" data-group-id="7953626714-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7953626714-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7953626714-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7953626714-15">}</span><span class="p" data-group-id="7953626714-14">}</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7953626714-16">(</span><span class="n">List</span><span class="p" data-group-id="7953626714-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">New_list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="7953626714-17">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7953626714-17">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">sort</span><span class="p" data-group-id="7953626714-18">(</span><span class="nf">fun</span><span class="p" data-group-id="7953626714-19">(</span><span class="p" data-group-id="7953626714-20">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7953626714-21">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp1</span><span class="p" data-group-id="7953626714-21">}</span><span class="p" data-group-id="7953626714-20">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7953626714-22">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7953626714-23">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp2</span><span class="p" data-group-id="7953626714-23">}</span><span class="p" data-group-id="7953626714-22">}</span><span class="p" data-group-id="7953626714-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                       </span><span class="n">Temp1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Temp2</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">New_list</span><span class="p" data-group-id="7953626714-18">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">93&gt; </span><span class="nf">c</span><span class="p" data-group-id="1896032311-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="1896032311-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1896032311-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut13</span><span class="p" data-group-id="1896032311-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">94&gt; </span><span class="nc">tut13</span><span class="p">:</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1896032311-3">(</span><span class="p" data-group-id="1896032311-4">[</span><span class="p" data-group-id="1896032311-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1896032311-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="1896032311-6">}</span><span class="p" data-group-id="1896032311-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1896032311-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1896032311-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="1896032311-8">}</span><span class="p" data-group-id="1896032311-7">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1896032311-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1896032311-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="1896032311-10">}</span><span class="p" data-group-id="1896032311-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1896032311-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1896032311-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="1896032311-12">}</span><span class="p" data-group-id="1896032311-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1896032311-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1896032311-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="1896032311-14">}</span><span class="p" data-group-id="1896032311-13">}</span><span class="p" data-group-id="1896032311-4">]</span><span class="p" data-group-id="1896032311-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1896032311-15">[</span><span class="p" data-group-id="1896032311-16">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="1896032311-17">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="1896032311-17">}</span><span class="p" data-group-id="1896032311-16">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="1896032311-18">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="1896032311-19">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="1896032311-19">}</span><span class="p" data-group-id="1896032311-18">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="1896032311-20">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="1896032311-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="1896032311-21">}</span><span class="p" data-group-id="1896032311-20">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="1896032311-22">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="1896032311-23">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1896032311-23">}</span><span class="p" data-group-id="1896032311-22">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="1896032311-24">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="1896032311-25">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">21</span><span class="p" data-group-id="1896032311-25">}</span><span class="p" data-group-id="1896032311-24">}</span><span class="p" data-group-id="1896032311-15">]</span></code></pre><p>In <code class="inline">sort</code> the fun is used:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="p" data-group-id="7265207575-1">(</span><span class="p" data-group-id="7265207575-2">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7265207575-3">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp1</span><span class="p" data-group-id="7265207575-3">}</span><span class="p" data-group-id="7265207575-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7265207575-4">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7265207575-5">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp2</span><span class="p" data-group-id="7265207575-5">}</span><span class="p" data-group-id="7265207575-4">}</span><span class="p" data-group-id="7265207575-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Temp1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Temp2</span><span class="w"> </span><span class="k">end</span><span class="p">,</span></code></pre><p>Here the concept of an <em>anonymous variable</em> <code class="inline">_</code> is introduced. This is simply
│ │ │  shorthand for a variable that gets a value, but the value is ignored. This can
│ │ │  be used anywhere suitable, not just in funs. <code class="inline">Temp1 &lt; Temp2</code> returns <code class="inline">true</code> if
│ │ │  <code class="inline">Temp1</code> is less than <code class="inline">Temp2</code>.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/spec_proc.html
│ │ │ @@ -123,72 +123,72 @@
│ │ │    <a href="#simple-debugging" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Simple Debugging</span>
│ │ │  </h2>
│ │ │  <p>The <a href="../../lib/stdlib-8.0/doc/html/sys.html"><code class="inline">sys</code></a> module has functions for simple debugging of processes implemented
│ │ │  using behaviours. The <code class="inline">code_lock</code> example from
│ │ │ -<a href="statem.html#example">gen_statem Behaviour</a> is used to illustrate this:</p><pre><code class="makeup erlang" translate="no"><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="4611499548-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">15.0</span><span class="p" data-group-id="4611499548-1">]</span><span class="w"> </span><span class="p" data-group-id="4611499548-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="4611499548-2">]</span><span class="w"> </span><span class="p" data-group-id="4611499548-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="4611499548-3">]</span><span class="w"> </span><span class="p" data-group-id="4611499548-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="4611499548-4">]</span><span class="w"> </span><span class="p" data-group-id="4611499548-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4611499548-5">]</span><span class="w"> </span><span class="p" data-group-id="4611499548-6">[</span><span class="ss">jit</span><span class="p" data-group-id="4611499548-6">]</span><span class="w">
│ │ │ +<a href="statem.html#example">gen_statem Behaviour</a> is used to illustrate this:</p><pre><code class="makeup erlang" translate="no"><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="0161349926-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">15.0</span><span class="p" data-group-id="0161349926-1">]</span><span class="w"> </span><span class="p" data-group-id="0161349926-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="0161349926-2">]</span><span class="w"> </span><span class="p" data-group-id="0161349926-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="0161349926-3">]</span><span class="w"> </span><span class="p" data-group-id="0161349926-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="0161349926-4">]</span><span class="w"> </span><span class="p" data-group-id="0161349926-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="0161349926-5">]</span><span class="w"> </span><span class="p" data-group-id="0161349926-6">[</span><span class="ss">jit</span><span class="p" data-group-id="0161349926-6">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V15</span><span class="p">.</span><span class="mi">0</span><span class="w"> </span><span class="p" data-group-id="4611499548-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="4611499548-8">(</span><span class="p" data-group-id="4611499548-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="4611499548-7">)</span><span class="w">
│ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="4611499548-9">(</span><span class="p" data-group-id="4611499548-10">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4611499548-10">]</span><span class="p" data-group-id="4611499548-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V15</span><span class="p">.</span><span class="mi">0</span><span class="w"> </span><span class="p" data-group-id="0161349926-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="0161349926-8">(</span><span class="p" data-group-id="0161349926-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="0161349926-7">)</span><span class="w">
│ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="0161349926-9">(</span><span class="p" data-group-id="0161349926-10">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0161349926-10">]</span><span class="p" data-group-id="0161349926-9">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="n">Lock</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4611499548-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="4611499548-11">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="4611499548-12">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4611499548-12">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0161349926-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0161349926-11">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="0161349926-12">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0161349926-12">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="4611499548-13">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4611499548-13">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="0161349926-13">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0161349926-13">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="4611499548-14">(</span><span class="mi">1</span><span class="p" data-group-id="4611499548-14">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="4611499548-15">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4611499548-15">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="0161349926-14">(</span><span class="mi">1</span><span class="p" data-group-id="0161349926-14">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="0161349926-15">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0161349926-15">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="4611499548-16">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4611499548-16">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="4611499548-17">(</span><span class="mi">2</span><span class="p" data-group-id="4611499548-17">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="4611499548-18">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4611499548-18">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="0161349926-16">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0161349926-16">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="0161349926-17">(</span><span class="mi">2</span><span class="p" data-group-id="0161349926-17">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="0161349926-18">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0161349926-18">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="4611499548-19">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4611499548-19">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="4611499548-20">(</span><span class="mi">3</span><span class="p" data-group-id="4611499548-20">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="4611499548-21">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4611499548-21">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="0161349926-19">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0161349926-19">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="0161349926-20">(</span><span class="mi">3</span><span class="p" data-group-id="0161349926-20">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="0161349926-21">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0161349926-21">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="4611499548-22">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4611499548-22">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ -</span><span class="gp unselectable">7&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="4611499548-23">(</span><span class="mi">4</span><span class="p" data-group-id="4611499548-23">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="4611499548-24">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4611499548-24">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="0161349926-22">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0161349926-22">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ +</span><span class="gp unselectable">7&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="0161349926-23">(</span><span class="mi">4</span><span class="p" data-group-id="0161349926-23">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="0161349926-24">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0161349926-24">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │  </span><span class="n">Unlock</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="4611499548-25">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4611499548-25">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="nb">start_timer</span><span class="w"> </span><span class="p" data-group-id="4611499548-26">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10000</span><span class="p">,</span><span class="ss">lock</span><span class="p">,</span><span class="p" data-group-id="4611499548-27">[</span><span class="p" data-group-id="4611499548-27">]</span><span class="p" data-group-id="4611499548-26">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="0161349926-25">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0161349926-25">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="nb">start_timer</span><span class="w"> </span><span class="p" data-group-id="0161349926-26">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10000</span><span class="p">,</span><span class="ss">lock</span><span class="p">,</span><span class="p" data-group-id="0161349926-27">[</span><span class="p" data-group-id="0161349926-27">]</span><span class="p" data-group-id="0161349926-26">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │  </span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">state_timeout</span><span class="w"> </span><span class="ss">lock</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │  </span><span class="n">Lock</span><span class="w">
│ │ │  </span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">state_timeout</span><span class="w"> </span><span class="ss">lock</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">open</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ -</span><span class="gp unselectable">8&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="4611499548-28">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="nb">get</span><span class="p" data-group-id="4611499548-28">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4611499548-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="4611499548-30">[</span><span class="p" data-group-id="4611499548-31">{</span><span class="ss">start_time</span><span class="p">,</span><span class="p" data-group-id="4611499548-32">{</span><span class="p" data-group-id="4611499548-33">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4611499548-33">}</span><span class="p">,</span><span class="p" data-group-id="4611499548-34">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4611499548-34">}</span><span class="p" data-group-id="4611499548-32">}</span><span class="p" data-group-id="4611499548-31">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="4611499548-35">{</span><span class="ss">current_time</span><span class="p">,</span><span class="p" data-group-id="4611499548-36">{</span><span class="p" data-group-id="4611499548-37">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4611499548-37">}</span><span class="p">,</span><span class="p" data-group-id="4611499548-38">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">48</span><span class="p" data-group-id="4611499548-38">}</span><span class="p" data-group-id="4611499548-36">}</span><span class="p" data-group-id="4611499548-35">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="4611499548-39">{</span><span class="ss">reductions</span><span class="p">,</span><span class="mi">4098</span><span class="p" data-group-id="4611499548-39">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="4611499548-40">{</span><span class="ss">messages_in</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="4611499548-40">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="4611499548-41">{</span><span class="ss">messages_out</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="4611499548-41">}</span><span class="p" data-group-id="4611499548-30">]</span><span class="p" data-group-id="4611499548-29">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">9&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="4611499548-42">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="4611499548-42">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">10&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="4611499548-43">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="4611499548-43">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">11&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">get_status</span><span class="p" data-group-id="4611499548-44">(</span><span class="ss">code_lock</span><span class="p" data-group-id="4611499548-44">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4611499548-45">{</span><span class="ss">status</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="4611499548-46">{</span><span class="ss">module</span><span class="p">,</span><span class="ss">gen_statem</span><span class="p" data-group-id="4611499548-46">}</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="4611499548-47">[</span><span class="p" data-group-id="4611499548-48">[</span><span class="p" data-group-id="4611499548-49">{</span><span class="ss">&#39;$initial_call&#39;</span><span class="p">,</span><span class="p" data-group-id="4611499548-50">{</span><span class="ss">code_lock</span><span class="p">,</span><span class="ss">init</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4611499548-50">}</span><span class="p" data-group-id="4611499548-49">}</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="p" data-group-id="4611499548-51">{</span><span class="ss">&#39;$ancestors&#39;</span><span class="p">,</span><span class="p" data-group-id="4611499548-52">[</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.87</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.70</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.65</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.69</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ -                         </span><span class="o">&lt;</span><span class="mf">0.64</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">kernel_sup</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.47</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="4611499548-52">]</span><span class="p" data-group-id="4611499548-51">}</span><span class="p" data-group-id="4611499548-48">]</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="ss">running</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="p" data-group-id="4611499548-53">[</span><span class="p" data-group-id="4611499548-53">]</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="4611499548-54">[</span><span class="p" data-group-id="4611499548-55">{</span><span class="ss">header</span><span class="p">,</span><span class="s">&quot;Status for state machine code_lock&quot;</span><span class="p" data-group-id="4611499548-55">}</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="p" data-group-id="4611499548-56">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="4611499548-57">[</span><span class="p" data-group-id="4611499548-58">{</span><span class="s">&quot;Status&quot;</span><span class="p">,</span><span class="ss">running</span><span class="p" data-group-id="4611499548-58">}</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="p" data-group-id="4611499548-59">{</span><span class="s">&quot;Parent&quot;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="4611499548-59">}</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="p" data-group-id="4611499548-60">{</span><span class="s">&quot;Modules&quot;</span><span class="p">,</span><span class="p" data-group-id="4611499548-61">[</span><span class="ss">code_lock</span><span class="p" data-group-id="4611499548-61">]</span><span class="p" data-group-id="4611499548-60">}</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="p" data-group-id="4611499548-62">{</span><span class="s">&quot;Time-outs&quot;</span><span class="p">,</span><span class="p" data-group-id="4611499548-63">{</span><span class="mi">0</span><span class="p">,</span><span class="p" data-group-id="4611499548-64">[</span><span class="p" data-group-id="4611499548-64">]</span><span class="p" data-group-id="4611499548-63">}</span><span class="p" data-group-id="4611499548-62">}</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="p" data-group-id="4611499548-65">{</span><span class="s">&quot;Logged Events&quot;</span><span class="p">,</span><span class="p" data-group-id="4611499548-66">[</span><span class="p" data-group-id="4611499548-66">]</span><span class="p" data-group-id="4611499548-65">}</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="p" data-group-id="4611499548-67">{</span><span class="s">&quot;Postponed&quot;</span><span class="p">,</span><span class="p" data-group-id="4611499548-68">[</span><span class="p" data-group-id="4611499548-68">]</span><span class="p" data-group-id="4611499548-67">}</span><span class="p" data-group-id="4611499548-57">]</span><span class="p" data-group-id="4611499548-56">}</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="p" data-group-id="4611499548-69">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="4611499548-70">[</span><span class="p" data-group-id="4611499548-71">{</span><span class="s">&quot;State&quot;</span><span class="p">,</span><span class="w">
│ │ │ -                  </span><span class="p" data-group-id="4611499548-72">{</span><span class="ss">locked</span><span class="p">,</span><span class="p" data-group-id="4611499548-73">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4611499548-74">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4611499548-74">]</span><span class="p">,</span><span class="w">
│ │ │ -                            </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4611499548-75">[</span><span class="p" data-group-id="4611499548-75">]</span><span class="p" data-group-id="4611499548-73">}</span><span class="p" data-group-id="4611499548-72">}</span><span class="p" data-group-id="4611499548-71">}</span><span class="p" data-group-id="4611499548-70">]</span><span class="p" data-group-id="4611499548-69">}</span><span class="p" data-group-id="4611499548-54">]</span><span class="p" data-group-id="4611499548-47">]</span><span class="p" data-group-id="4611499548-45">}</span></code></pre><h2 id="special-processes" class="section-heading">
│ │ │ +</span><span class="gp unselectable">8&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="0161349926-28">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="nb">get</span><span class="p" data-group-id="0161349926-28">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0161349926-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="0161349926-30">[</span><span class="p" data-group-id="0161349926-31">{</span><span class="ss">start_time</span><span class="p">,</span><span class="p" data-group-id="0161349926-32">{</span><span class="p" data-group-id="0161349926-33">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0161349926-33">}</span><span class="p">,</span><span class="p" data-group-id="0161349926-34">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0161349926-34">}</span><span class="p" data-group-id="0161349926-32">}</span><span class="p" data-group-id="0161349926-31">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="0161349926-35">{</span><span class="ss">current_time</span><span class="p">,</span><span class="p" data-group-id="0161349926-36">{</span><span class="p" data-group-id="0161349926-37">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0161349926-37">}</span><span class="p">,</span><span class="p" data-group-id="0161349926-38">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">48</span><span class="p" data-group-id="0161349926-38">}</span><span class="p" data-group-id="0161349926-36">}</span><span class="p" data-group-id="0161349926-35">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="0161349926-39">{</span><span class="ss">reductions</span><span class="p">,</span><span class="mi">4098</span><span class="p" data-group-id="0161349926-39">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="0161349926-40">{</span><span class="ss">messages_in</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0161349926-40">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="0161349926-41">{</span><span class="ss">messages_out</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="0161349926-41">}</span><span class="p" data-group-id="0161349926-30">]</span><span class="p" data-group-id="0161349926-29">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">9&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="0161349926-42">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="0161349926-42">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">ok</span><span class="w">
│ │ │ +</span><span class="gp unselectable">10&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="0161349926-43">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="0161349926-43">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">ok</span><span class="w">
│ │ │ +</span><span class="gp unselectable">11&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">get_status</span><span class="p" data-group-id="0161349926-44">(</span><span class="ss">code_lock</span><span class="p" data-group-id="0161349926-44">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0161349926-45">{</span><span class="ss">status</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0161349926-46">{</span><span class="ss">module</span><span class="p">,</span><span class="ss">gen_statem</span><span class="p" data-group-id="0161349926-46">}</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0161349926-47">[</span><span class="p" data-group-id="0161349926-48">[</span><span class="p" data-group-id="0161349926-49">{</span><span class="ss">&#39;$initial_call&#39;</span><span class="p">,</span><span class="p" data-group-id="0161349926-50">{</span><span class="ss">code_lock</span><span class="p">,</span><span class="ss">init</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0161349926-50">}</span><span class="p" data-group-id="0161349926-49">}</span><span class="p">,</span><span class="w">
│ │ │ +          </span><span class="p" data-group-id="0161349926-51">{</span><span class="ss">&#39;$ancestors&#39;</span><span class="p">,</span><span class="p" data-group-id="0161349926-52">[</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.87</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.70</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.65</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.69</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ +                         </span><span class="o">&lt;</span><span class="mf">0.64</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">kernel_sup</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.47</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0161349926-52">]</span><span class="p" data-group-id="0161349926-51">}</span><span class="p" data-group-id="0161349926-48">]</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="ss">running</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="p" data-group-id="0161349926-53">[</span><span class="p" data-group-id="0161349926-53">]</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="0161349926-54">[</span><span class="p" data-group-id="0161349926-55">{</span><span class="ss">header</span><span class="p">,</span><span class="s">&quot;Status for state machine code_lock&quot;</span><span class="p" data-group-id="0161349926-55">}</span><span class="p">,</span><span class="w">
│ │ │ +          </span><span class="p" data-group-id="0161349926-56">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="0161349926-57">[</span><span class="p" data-group-id="0161349926-58">{</span><span class="s">&quot;Status&quot;</span><span class="p">,</span><span class="ss">running</span><span class="p" data-group-id="0161349926-58">}</span><span class="p">,</span><span class="w">
│ │ │ +                 </span><span class="p" data-group-id="0161349926-59">{</span><span class="s">&quot;Parent&quot;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0161349926-59">}</span><span class="p">,</span><span class="w">
│ │ │ +                 </span><span class="p" data-group-id="0161349926-60">{</span><span class="s">&quot;Modules&quot;</span><span class="p">,</span><span class="p" data-group-id="0161349926-61">[</span><span class="ss">code_lock</span><span class="p" data-group-id="0161349926-61">]</span><span class="p" data-group-id="0161349926-60">}</span><span class="p">,</span><span class="w">
│ │ │ +                 </span><span class="p" data-group-id="0161349926-62">{</span><span class="s">&quot;Time-outs&quot;</span><span class="p">,</span><span class="p" data-group-id="0161349926-63">{</span><span class="mi">0</span><span class="p">,</span><span class="p" data-group-id="0161349926-64">[</span><span class="p" data-group-id="0161349926-64">]</span><span class="p" data-group-id="0161349926-63">}</span><span class="p" data-group-id="0161349926-62">}</span><span class="p">,</span><span class="w">
│ │ │ +                 </span><span class="p" data-group-id="0161349926-65">{</span><span class="s">&quot;Logged Events&quot;</span><span class="p">,</span><span class="p" data-group-id="0161349926-66">[</span><span class="p" data-group-id="0161349926-66">]</span><span class="p" data-group-id="0161349926-65">}</span><span class="p">,</span><span class="w">
│ │ │ +                 </span><span class="p" data-group-id="0161349926-67">{</span><span class="s">&quot;Postponed&quot;</span><span class="p">,</span><span class="p" data-group-id="0161349926-68">[</span><span class="p" data-group-id="0161349926-68">]</span><span class="p" data-group-id="0161349926-67">}</span><span class="p" data-group-id="0161349926-57">]</span><span class="p" data-group-id="0161349926-56">}</span><span class="p">,</span><span class="w">
│ │ │ +          </span><span class="p" data-group-id="0161349926-69">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="0161349926-70">[</span><span class="p" data-group-id="0161349926-71">{</span><span class="s">&quot;State&quot;</span><span class="p">,</span><span class="w">
│ │ │ +                  </span><span class="p" data-group-id="0161349926-72">{</span><span class="ss">locked</span><span class="p">,</span><span class="p" data-group-id="0161349926-73">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="0161349926-74">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0161349926-74">]</span><span class="p">,</span><span class="w">
│ │ │ +                            </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="0161349926-75">[</span><span class="p" data-group-id="0161349926-75">]</span><span class="p" data-group-id="0161349926-73">}</span><span class="p" data-group-id="0161349926-72">}</span><span class="p" data-group-id="0161349926-71">}</span><span class="p" data-group-id="0161349926-70">]</span><span class="p" data-group-id="0161349926-69">}</span><span class="p" data-group-id="0161349926-54">]</span><span class="p" data-group-id="0161349926-47">]</span><span class="p" data-group-id="0161349926-45">}</span></code></pre><h2 id="special-processes" class="section-heading">
│ │ │    <a href="#special-processes" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Special Processes</span>
│ │ │  </h2>
│ │ │  <p>This section describes how to write a process that complies to the OTP design
│ │ │  principles, without using a standard behaviour. Such a process is to:</p><ul><li>Be started in a way that makes the process fit into a supervision tree</li><li>Support the <code class="inline">sys</code> <a href="spec_proc.html#debug">debug facilities</a></li><li>Take care of <a href="spec_proc.html#msg">system messages</a>.</li></ul><p>System messages are messages with a special meaning, used in the supervision
│ │ │ @@ -198,238 +198,238 @@
│ │ │    <a href="#example" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Example</span>
│ │ │  </h3>
│ │ │  <p>Here follows the simple server from
│ │ │  <a href="design_principles.html#ch1">Overview</a>,
│ │ │ -implemented using <code class="inline">sys</code> and <code class="inline">proc_lib</code> to fit into a supervision tree:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3096050450-1">(</span><span class="ss">ch4</span><span class="p" data-group-id="3096050450-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3096050450-2">(</span><span class="p" data-group-id="3096050450-3">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3096050450-3">]</span><span class="p" data-group-id="3096050450-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3096050450-4">(</span><span class="p" data-group-id="3096050450-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3096050450-5">]</span><span class="p" data-group-id="3096050450-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3096050450-6">(</span><span class="p" data-group-id="3096050450-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3096050450-7">]</span><span class="p" data-group-id="3096050450-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3096050450-8">(</span><span class="p" data-group-id="3096050450-9">[</span><span class="ss">system_continue</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">system_terminate</span><span class="p">/</span><span class="mi">4</span><span class="p">,</span><span class="w">
│ │ │ +implemented using <code class="inline">sys</code> and <code class="inline">proc_lib</code> to fit into a supervision tree:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1392775877-1">(</span><span class="ss">ch4</span><span class="p" data-group-id="1392775877-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1392775877-2">(</span><span class="p" data-group-id="1392775877-3">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1392775877-3">]</span><span class="p" data-group-id="1392775877-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1392775877-4">(</span><span class="p" data-group-id="1392775877-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1392775877-5">]</span><span class="p" data-group-id="1392775877-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1392775877-6">(</span><span class="p" data-group-id="1392775877-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1392775877-7">]</span><span class="p" data-group-id="1392775877-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1392775877-8">(</span><span class="p" data-group-id="1392775877-9">[</span><span class="ss">system_continue</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">system_terminate</span><span class="p">/</span><span class="mi">4</span><span class="p">,</span><span class="w">
│ │ │           </span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="ss">system_get_state</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">system_replace_state</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3096050450-9">]</span><span class="p" data-group-id="3096050450-8">)</span><span class="p">.</span><span class="w">
│ │ │ +         </span><span class="ss">system_get_state</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">system_replace_state</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1392775877-9">]</span><span class="p" data-group-id="1392775877-8">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="3096050450-10">(</span><span class="p" data-group-id="3096050450-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="3096050450-11">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3096050450-12">[</span><span class="nf">self</span><span class="p" data-group-id="3096050450-13">(</span><span class="p" data-group-id="3096050450-13">)</span><span class="p" data-group-id="3096050450-12">]</span><span class="p" data-group-id="3096050450-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="1392775877-10">(</span><span class="p" data-group-id="1392775877-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="1392775877-11">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1392775877-12">[</span><span class="nf">self</span><span class="p" data-group-id="1392775877-13">(</span><span class="p" data-group-id="1392775877-13">)</span><span class="p" data-group-id="1392775877-12">]</span><span class="p" data-group-id="1392775877-11">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="3096050450-14">(</span><span class="p" data-group-id="3096050450-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ch4</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3096050450-15">{</span><span class="nf">self</span><span class="p" data-group-id="3096050450-16">(</span><span class="p" data-group-id="3096050450-16">)</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="3096050450-15">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="1392775877-14">(</span><span class="p" data-group-id="1392775877-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ch4</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1392775877-15">{</span><span class="nf">self</span><span class="p" data-group-id="1392775877-16">(</span><span class="p" data-group-id="1392775877-16">)</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="1392775877-15">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3096050450-17">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="3096050450-17">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="1392775877-17">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="1392775877-17">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="n">Res</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="3096050450-18">(</span><span class="n">Ch</span><span class="p" data-group-id="3096050450-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ch4</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3096050450-19">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3096050450-19">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="1392775877-18">(</span><span class="n">Ch</span><span class="p" data-group-id="1392775877-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ch4</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1392775877-19">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1392775877-19">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="3096050450-20">(</span><span class="n">Parent</span><span class="p" data-group-id="3096050450-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="3096050450-21">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3096050450-22">(</span><span class="p" data-group-id="3096050450-22">)</span><span class="p" data-group-id="3096050450-21">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Chs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="3096050450-23">(</span><span class="p" data-group-id="3096050450-23">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Deb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="3096050450-24">(</span><span class="p" data-group-id="3096050450-25">[</span><span class="p" data-group-id="3096050450-25">]</span><span class="p" data-group-id="3096050450-24">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="3096050450-26">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3096050450-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3096050450-28">(</span><span class="p" data-group-id="3096050450-28">)</span><span class="p" data-group-id="3096050450-27">}</span><span class="p" data-group-id="3096050450-26">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="3096050450-29">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="3096050450-29">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="1392775877-20">(</span><span class="n">Parent</span><span class="p" data-group-id="1392775877-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="1392775877-21">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1392775877-22">(</span><span class="p" data-group-id="1392775877-22">)</span><span class="p" data-group-id="1392775877-21">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Chs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="1392775877-23">(</span><span class="p" data-group-id="1392775877-23">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Deb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="1392775877-24">(</span><span class="p" data-group-id="1392775877-25">[</span><span class="p" data-group-id="1392775877-25">]</span><span class="p" data-group-id="1392775877-24">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="1392775877-26">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1392775877-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1392775877-28">(</span><span class="p" data-group-id="1392775877-28">)</span><span class="p" data-group-id="1392775877-27">}</span><span class="p" data-group-id="1392775877-26">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="1392775877-29">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="1392775877-29">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="3096050450-30">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="3096050450-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="1392775877-30">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="1392775877-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3096050450-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="3096050450-31">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="3096050450-32">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3096050450-33">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="3096050450-33">}</span><span class="p" data-group-id="3096050450-32">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="3096050450-34">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="3096050450-34">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="3096050450-35">(</span><span class="n">Chs</span><span class="p" data-group-id="3096050450-35">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3096050450-36">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3096050450-36">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">Deb3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="3096050450-37">(</span><span class="n">Deb2</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3096050450-38">{</span><span class="ss">out</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3096050450-39">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3096050450-39">}</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="3096050450-38">}</span><span class="p" data-group-id="3096050450-37">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="3096050450-40">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb3</span><span class="p" data-group-id="3096050450-40">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3096050450-41">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3096050450-41">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="3096050450-42">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3096050450-43">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3096050450-44">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3096050450-44">}</span><span class="p" data-group-id="3096050450-43">}</span><span class="p" data-group-id="3096050450-42">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="3096050450-45">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3096050450-45">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="3096050450-46">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb2</span><span class="p" data-group-id="3096050450-46">)</span><span class="p">;</span><span class="w">
│ │ │ -
│ │ │ -        </span><span class="p" data-group-id="3096050450-47">{</span><span class="ss">system</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="3096050450-47">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="3096050450-48">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w">
│ │ │ -                                  </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3096050450-48">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="1392775877-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="1392775877-31">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="1392775877-32">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1392775877-33">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="1392775877-33">}</span><span class="p" data-group-id="1392775877-32">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="1392775877-34">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="1392775877-34">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="1392775877-35">(</span><span class="n">Chs</span><span class="p" data-group-id="1392775877-35">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1392775877-36">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1392775877-36">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">Deb3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="1392775877-37">(</span><span class="n">Deb2</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1392775877-38">{</span><span class="ss">out</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1392775877-39">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1392775877-39">}</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="1392775877-38">}</span><span class="p" data-group-id="1392775877-37">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="1392775877-40">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb3</span><span class="p" data-group-id="1392775877-40">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="1392775877-41">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1392775877-41">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="1392775877-42">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1392775877-43">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1392775877-44">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1392775877-44">}</span><span class="p" data-group-id="1392775877-43">}</span><span class="p" data-group-id="1392775877-42">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="1392775877-45">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1392775877-45">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="1392775877-46">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb2</span><span class="p" data-group-id="1392775877-46">)</span><span class="p">;</span><span class="w">
│ │ │ +
│ │ │ +        </span><span class="p" data-group-id="1392775877-47">{</span><span class="ss">system</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="1392775877-47">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="1392775877-48">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w">
│ │ │ +                                  </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1392775877-48">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_continue</span><span class="p" data-group-id="3096050450-49">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3096050450-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="3096050450-50">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="3096050450-50">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">system_continue</span><span class="p" data-group-id="1392775877-49">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1392775877-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="1392775877-50">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="1392775877-50">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_terminate</span><span class="p" data-group-id="3096050450-51">(</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Chs</span><span class="p" data-group-id="3096050450-51">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">exit</span><span class="p" data-group-id="3096050450-52">(</span><span class="n">Reason</span><span class="p" data-group-id="3096050450-52">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">system_terminate</span><span class="p" data-group-id="1392775877-51">(</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Chs</span><span class="p" data-group-id="1392775877-51">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">exit</span><span class="p" data-group-id="1392775877-52">(</span><span class="n">Reason</span><span class="p" data-group-id="1392775877-52">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_get_state</span><span class="p" data-group-id="3096050450-53">(</span><span class="n">Chs</span><span class="p" data-group-id="3096050450-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3096050450-54">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3096050450-54">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">system_get_state</span><span class="p" data-group-id="1392775877-53">(</span><span class="n">Chs</span><span class="p" data-group-id="1392775877-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1392775877-54">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1392775877-54">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_replace_state</span><span class="p" data-group-id="3096050450-55">(</span><span class="n">StateFun</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3096050450-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">NChs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StateFun</span><span class="p" data-group-id="3096050450-56">(</span><span class="n">Chs</span><span class="p" data-group-id="3096050450-56">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3096050450-57">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p" data-group-id="3096050450-57">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">system_replace_state</span><span class="p" data-group-id="1392775877-55">(</span><span class="n">StateFun</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1392775877-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">NChs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StateFun</span><span class="p" data-group-id="1392775877-56">(</span><span class="n">Chs</span><span class="p" data-group-id="1392775877-56">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1392775877-57">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p" data-group-id="1392775877-57">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">write_debug</span><span class="p" data-group-id="3096050450-58">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3096050450-58">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3096050450-59">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> event = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3096050450-60">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="3096050450-60">]</span><span class="p" data-group-id="3096050450-59">)</span><span class="p">.</span></code></pre><p id="ex">As it is not relevant to the example, the channel handling functions have been
│ │ │ +</span><span class="nf">write_debug</span><span class="p" data-group-id="1392775877-58">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1392775877-58">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1392775877-59">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> event = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1392775877-60">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="1392775877-60">]</span><span class="p" data-group-id="1392775877-59">)</span><span class="p">.</span></code></pre><p id="ex">As it is not relevant to the example, the channel handling functions have been
│ │ │  omitted. To compile this example, the
│ │ │  <a href="design_principles.html#channels-implementation">implementation of channel handling</a>
│ │ │  needs to be added to the module.</p><p>Here is an example showing how the debugging functions in the <code class="inline">sys</code>
│ │ │  module can be used for <code class="inline">ch4</code>:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="3522142574-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">15.0</span><span class="p" data-group-id="3522142574-1">]</span><span class="w"> </span><span class="p" data-group-id="3522142574-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="3522142574-2">]</span><span class="w"> </span><span class="p" data-group-id="3522142574-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="3522142574-3">]</span><span class="w"> </span><span class="p" data-group-id="3522142574-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="3522142574-4">]</span><span class="w"> </span><span class="p" data-group-id="3522142574-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="3522142574-5">]</span><span class="w"> </span><span class="p" data-group-id="3522142574-6">[</span><span class="ss">jit</span><span class="p" data-group-id="3522142574-6">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="4427973425-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">15.0</span><span class="p" data-group-id="4427973425-1">]</span><span class="w"> </span><span class="p" data-group-id="4427973425-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="4427973425-2">]</span><span class="w"> </span><span class="p" data-group-id="4427973425-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="4427973425-3">]</span><span class="w"> </span><span class="p" data-group-id="4427973425-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="4427973425-4">]</span><span class="w"> </span><span class="p" data-group-id="4427973425-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4427973425-5">]</span><span class="w"> </span><span class="p" data-group-id="4427973425-6">[</span><span class="ss">jit</span><span class="p" data-group-id="4427973425-6">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V15</span><span class="p">.</span><span class="mi">0</span><span class="w"> </span><span class="p" data-group-id="3522142574-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="3522142574-8">(</span><span class="p" data-group-id="3522142574-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="3522142574-7">)</span><span class="w">
│ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="3522142574-9">(</span><span class="p" data-group-id="3522142574-9">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3522142574-10">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="3522142574-10">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="3522142574-11">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3522142574-11">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="3522142574-12">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3522142574-12">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">alloc</span><span class="p" data-group-id="3522142574-13">(</span><span class="p" data-group-id="3522142574-13">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3522142574-14">{</span><span class="ss">in</span><span class="p">,</span><span class="ss">alloc</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="3522142574-14">}</span><span class="w">
│ │ │ -</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3522142574-15">{</span><span class="ss">out</span><span class="p">,</span><span class="p" data-group-id="3522142574-16">{</span><span class="ss">ch4</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3522142574-16">}</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="3522142574-15">}</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V15</span><span class="p">.</span><span class="mi">0</span><span class="w"> </span><span class="p" data-group-id="4427973425-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="4427973425-8">(</span><span class="p" data-group-id="4427973425-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="4427973425-7">)</span><span class="w">
│ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="4427973425-9">(</span><span class="p" data-group-id="4427973425-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4427973425-10">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="4427973425-10">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="4427973425-11">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4427973425-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">ok</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="4427973425-12">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4427973425-12">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">ok</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">alloc</span><span class="p" data-group-id="4427973425-13">(</span><span class="p" data-group-id="4427973425-13">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4427973425-14">{</span><span class="ss">in</span><span class="p">,</span><span class="ss">alloc</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="4427973425-14">}</span><span class="w">
│ │ │ +</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4427973425-15">{</span><span class="ss">out</span><span class="p">,</span><span class="p" data-group-id="4427973425-16">{</span><span class="ss">ch4</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4427973425-16">}</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="4427973425-15">}</span><span class="w">
│ │ │  </span><span class="mi">1</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">free</span><span class="p" data-group-id="3522142574-17">(</span><span class="ss">ch1</span><span class="p" data-group-id="3522142574-17">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3522142574-18">{</span><span class="ss">in</span><span class="p">,</span><span class="p" data-group-id="3522142574-19">{</span><span class="ss">free</span><span class="p">,</span><span class="ss">ch1</span><span class="p" data-group-id="3522142574-19">}</span><span class="p" data-group-id="3522142574-18">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">free</span><span class="p" data-group-id="4427973425-17">(</span><span class="ss">ch1</span><span class="p" data-group-id="4427973425-17">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4427973425-18">{</span><span class="ss">in</span><span class="p">,</span><span class="p" data-group-id="4427973425-19">{</span><span class="ss">free</span><span class="p">,</span><span class="ss">ch1</span><span class="p" data-group-id="4427973425-19">}</span><span class="p" data-group-id="4427973425-18">}</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="3522142574-20">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="nb">get</span><span class="p" data-group-id="3522142574-20">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3522142574-21">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="3522142574-22">[</span><span class="p" data-group-id="3522142574-23">{</span><span class="ss">start_time</span><span class="p">,</span><span class="p" data-group-id="3522142574-24">{</span><span class="p" data-group-id="3522142574-25">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3522142574-25">}</span><span class="p">,</span><span class="p" data-group-id="3522142574-26">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">26</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="3522142574-26">}</span><span class="p" data-group-id="3522142574-24">}</span><span class="p" data-group-id="3522142574-23">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="3522142574-27">{</span><span class="ss">current_time</span><span class="p">,</span><span class="p" data-group-id="3522142574-28">{</span><span class="p" data-group-id="3522142574-29">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3522142574-29">}</span><span class="p">,</span><span class="p" data-group-id="3522142574-30">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">26</span><span class="p">,</span><span class="mi">49</span><span class="p" data-group-id="3522142574-30">}</span><span class="p" data-group-id="3522142574-28">}</span><span class="p" data-group-id="3522142574-27">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="3522142574-31">{</span><span class="ss">reductions</span><span class="p">,</span><span class="mi">202</span><span class="p" data-group-id="3522142574-31">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="3522142574-32">{</span><span class="ss">messages_in</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3522142574-32">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="3522142574-33">{</span><span class="ss">messages_out</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3522142574-33">}</span><span class="p" data-group-id="3522142574-22">]</span><span class="p" data-group-id="3522142574-21">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">7&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="3522142574-34">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="3522142574-34">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">8&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="3522142574-35">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="3522142574-35">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">9&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">get_status</span><span class="p" data-group-id="3522142574-36">(</span><span class="ss">ch4</span><span class="p" data-group-id="3522142574-36">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3522142574-37">{</span><span class="ss">status</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3522142574-38">{</span><span class="ss">module</span><span class="p">,</span><span class="ss">ch4</span><span class="p" data-group-id="3522142574-38">}</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3522142574-39">[</span><span class="p" data-group-id="3522142574-40">[</span><span class="p" data-group-id="3522142574-41">{</span><span class="ss">&#39;$initial_call&#39;</span><span class="p">,</span><span class="p" data-group-id="3522142574-42">{</span><span class="ss">ch4</span><span class="p">,</span><span class="ss">init</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3522142574-42">}</span><span class="p" data-group-id="3522142574-41">}</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="p" data-group-id="3522142574-43">{</span><span class="ss">&#39;$ancestors&#39;</span><span class="p">,</span><span class="p" data-group-id="3522142574-44">[</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.87</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.70</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.65</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.69</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ -                         </span><span class="o">&lt;</span><span class="mf">0.64</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">kernel_sup</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.47</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="3522142574-44">]</span><span class="p" data-group-id="3522142574-43">}</span><span class="p" data-group-id="3522142574-40">]</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="ss">running</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="p" data-group-id="3522142574-45">[</span><span class="p" data-group-id="3522142574-45">]</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="3522142574-46">{</span><span class="p" data-group-id="3522142574-47">[</span><span class="mi">1</span><span class="p" data-group-id="3522142574-47">]</span><span class="p">,</span><span class="p" data-group-id="3522142574-48">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">10</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p">,</span><span class="mi">14</span><span class="p">,</span><span class="mi">15</span><span class="p">,</span><span class="mi">16</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">18</span><span class="p">,</span><span class="mi">19</span><span class="p">|</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3522142574-48">]</span><span class="p" data-group-id="3522142574-46">}</span><span class="p" data-group-id="3522142574-39">]</span><span class="p" data-group-id="3522142574-37">}</span></code></pre><h3 id="starting-the-process" class="section-heading">
│ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="4427973425-20">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="nb">get</span><span class="p" data-group-id="4427973425-20">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4427973425-21">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="4427973425-22">[</span><span class="p" data-group-id="4427973425-23">{</span><span class="ss">start_time</span><span class="p">,</span><span class="p" data-group-id="4427973425-24">{</span><span class="p" data-group-id="4427973425-25">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4427973425-25">}</span><span class="p">,</span><span class="p" data-group-id="4427973425-26">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">26</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="4427973425-26">}</span><span class="p" data-group-id="4427973425-24">}</span><span class="p" data-group-id="4427973425-23">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="4427973425-27">{</span><span class="ss">current_time</span><span class="p">,</span><span class="p" data-group-id="4427973425-28">{</span><span class="p" data-group-id="4427973425-29">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4427973425-29">}</span><span class="p">,</span><span class="p" data-group-id="4427973425-30">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">26</span><span class="p">,</span><span class="mi">49</span><span class="p" data-group-id="4427973425-30">}</span><span class="p" data-group-id="4427973425-28">}</span><span class="p" data-group-id="4427973425-27">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="4427973425-31">{</span><span class="ss">reductions</span><span class="p">,</span><span class="mi">202</span><span class="p" data-group-id="4427973425-31">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="4427973425-32">{</span><span class="ss">messages_in</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4427973425-32">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="4427973425-33">{</span><span class="ss">messages_out</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4427973425-33">}</span><span class="p" data-group-id="4427973425-22">]</span><span class="p" data-group-id="4427973425-21">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">7&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="4427973425-34">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="4427973425-34">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">ok</span><span class="w">
│ │ │ +</span><span class="gp unselectable">8&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="4427973425-35">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="4427973425-35">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">ok</span><span class="w">
│ │ │ +</span><span class="gp unselectable">9&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">get_status</span><span class="p" data-group-id="4427973425-36">(</span><span class="ss">ch4</span><span class="p" data-group-id="4427973425-36">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4427973425-37">{</span><span class="ss">status</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="4427973425-38">{</span><span class="ss">module</span><span class="p">,</span><span class="ss">ch4</span><span class="p" data-group-id="4427973425-38">}</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="4427973425-39">[</span><span class="p" data-group-id="4427973425-40">[</span><span class="p" data-group-id="4427973425-41">{</span><span class="ss">&#39;$initial_call&#39;</span><span class="p">,</span><span class="p" data-group-id="4427973425-42">{</span><span class="ss">ch4</span><span class="p">,</span><span class="ss">init</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4427973425-42">}</span><span class="p" data-group-id="4427973425-41">}</span><span class="p">,</span><span class="w">
│ │ │ +          </span><span class="p" data-group-id="4427973425-43">{</span><span class="ss">&#39;$ancestors&#39;</span><span class="p">,</span><span class="p" data-group-id="4427973425-44">[</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.87</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.70</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.65</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.69</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ +                         </span><span class="o">&lt;</span><span class="mf">0.64</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">kernel_sup</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.47</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="4427973425-44">]</span><span class="p" data-group-id="4427973425-43">}</span><span class="p" data-group-id="4427973425-40">]</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="ss">running</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="p" data-group-id="4427973425-45">[</span><span class="p" data-group-id="4427973425-45">]</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="4427973425-46">{</span><span class="p" data-group-id="4427973425-47">[</span><span class="mi">1</span><span class="p" data-group-id="4427973425-47">]</span><span class="p">,</span><span class="p" data-group-id="4427973425-48">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">10</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p">,</span><span class="mi">14</span><span class="p">,</span><span class="mi">15</span><span class="p">,</span><span class="mi">16</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">18</span><span class="p">,</span><span class="mi">19</span><span class="p">|</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4427973425-48">]</span><span class="p" data-group-id="4427973425-46">}</span><span class="p" data-group-id="4427973425-39">]</span><span class="p" data-group-id="4427973425-37">}</span></code></pre><h3 id="starting-the-process" class="section-heading">
│ │ │    <a href="#starting-the-process" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Starting the Process</span>
│ │ │  </h3>
│ │ │  <p>A function in the <a href="../../lib/stdlib-8.0/doc/html/proc_lib.html"><code class="inline">proc_lib</code></a> module is to be used to start the process. Several
│ │ │  functions are available, for example,
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/proc_lib.html#spawn_link/4"><code class="inline">proc_lib:spawn_link/3,4</code></a>
│ │ │  for asynchronous start and
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/proc_lib.html#start_link/5"><code class="inline">proc_lib:start_link/3,4,5</code></a> for synchronous start.</p><p>Information necessary for a process within a supervision tree, such as
│ │ │  details on ancestors and the initial call, is stored when a process
│ │ │  is started through one of these functions.</p><p>If the process terminates with a reason other than <code class="inline">normal</code> or <code class="inline">shutdown</code>, a
│ │ │  crash report is generated. For more information about the crash report, see
│ │ │  <a href="../../lib/kernel-11.0/doc/html/logger_chapter.html">Logging</a> in Kernel User's Guide.</p><p>In the example, synchronous start is used. The process starts by calling
│ │ │ -<code class="inline">ch4:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="8057978359-1">(</span><span class="p" data-group-id="8057978359-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="8057978359-2">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8057978359-3">[</span><span class="nf">self</span><span class="p" data-group-id="8057978359-4">(</span><span class="p" data-group-id="8057978359-4">)</span><span class="p" data-group-id="8057978359-3">]</span><span class="p" data-group-id="8057978359-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch4:start_link/0</code> calls <a href="../../lib/stdlib-8.0/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a>, which takes a module
│ │ │ +<code class="inline">ch4:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="4555333564-1">(</span><span class="p" data-group-id="4555333564-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="4555333564-2">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4555333564-3">[</span><span class="nf">self</span><span class="p" data-group-id="4555333564-4">(</span><span class="p" data-group-id="4555333564-4">)</span><span class="p" data-group-id="4555333564-3">]</span><span class="p" data-group-id="4555333564-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch4:start_link/0</code> calls <a href="../../lib/stdlib-8.0/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a>, which takes a module
│ │ │  name, a function name, and an argument list as arguments. It then
│ │ │  spawns a new process and establishes a link. The new process starts
│ │ │  by executing the given function, here <code class="inline">ch4:init(Pid)</code>, where <code class="inline">Pid</code> is
│ │ │  the pid of the parent process (obtained by the call to
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#self/0"><code class="inline">self()</code></a> in the call to <a href="../../lib/stdlib-8.0/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a>).</p><p>All initialization, including name registration, is done in <code class="inline">init/1</code>. The new
│ │ │ -process has to acknowledge that it has been started to the parent:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="2263983219-1">(</span><span class="n">Parent</span><span class="p" data-group-id="2263983219-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +process has to acknowledge that it has been started to the parent:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="6679748670-1">(</span><span class="n">Parent</span><span class="p" data-group-id="6679748670-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="2263983219-2">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2263983219-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2263983219-4">(</span><span class="p" data-group-id="2263983219-4">)</span><span class="p" data-group-id="2263983219-3">}</span><span class="p" data-group-id="2263983219-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="2263983219-5">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2263983219-5">)</span><span class="p">.</span></code></pre><p><a href="../../lib/stdlib-8.0/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a> is synchronous and does not return until
│ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="6679748670-2">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6679748670-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6679748670-4">(</span><span class="p" data-group-id="6679748670-4">)</span><span class="p" data-group-id="6679748670-3">}</span><span class="p" data-group-id="6679748670-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="6679748670-5">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6679748670-5">)</span><span class="p">.</span></code></pre><p><a href="../../lib/stdlib-8.0/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a> is synchronous and does not return until
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/proc_lib.html#init_ack/2"><code class="inline">proc_lib:init_ack/1,2</code></a> or
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/proc_lib.html#init_fail/3"><code class="inline">proc_lib:init_fail/2,3</code></a> has been called,
│ │ │  or the process has exited.</p><p><a href="" id="debug"></a></p><h3 id="debugging" class="section-heading">
│ │ │    <a href="#debugging" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Debugging</span>
│ │ │  </h3>
│ │ │  <p>To support the debug facilities in <code class="inline">sys</code>, a <em>debug structure</em> is needed. The
│ │ │ -<code class="inline">Deb</code> term is initialized using <a href="../../lib/stdlib-8.0/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="5828375645-1">(</span><span class="n">Parent</span><span class="p" data-group-id="5828375645-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +<code class="inline">Deb</code> term is initialized using <a href="../../lib/stdlib-8.0/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="4146042143-1">(</span><span class="n">Parent</span><span class="p" data-group-id="4146042143-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="n">Deb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="5828375645-2">(</span><span class="p" data-group-id="5828375645-3">[</span><span class="p" data-group-id="5828375645-3">]</span><span class="p" data-group-id="5828375645-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Deb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="4146042143-2">(</span><span class="p" data-group-id="4146042143-3">[</span><span class="p" data-group-id="4146042143-3">]</span><span class="p" data-group-id="4146042143-2">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="5828375645-4">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="5828375645-4">)</span><span class="p">.</span></code></pre><p><a href="../../lib/stdlib-8.0/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a> takes a list of options. Given an empty list as in this
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="4146042143-4">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="4146042143-4">)</span><span class="p">.</span></code></pre><p><a href="../../lib/stdlib-8.0/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a> takes a list of options. Given an empty list as in this
│ │ │  example means that debugging is initially disabled. For information about the
│ │ │  possible options, see <a href="../../lib/stdlib-8.0/doc/html/sys.html"><code class="inline">sys</code></a> in STDLIB.</p><p>For each <em>system event</em> to be logged or traced, the following function
│ │ │ -is to be called:</p><pre><code class="makeup erlang" translate="no"><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="5296650979-1">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Func</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="5296650979-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Deb1</span></code></pre><p>The arguments have the following meaning:</p><ul><li><code class="inline">Deb</code> is the debug structure as returned from <a href="../../lib/stdlib-8.0/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a>.</li><li><code class="inline">Func</code> is a fun specifying a (user-defined) function used to format trace
│ │ │ +is to be called:</p><pre><code class="makeup erlang" translate="no"><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="0663973239-1">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Func</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="0663973239-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Deb1</span></code></pre><p>The arguments have the following meaning:</p><ul><li><code class="inline">Deb</code> is the debug structure as returned from <a href="../../lib/stdlib-8.0/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a>.</li><li><code class="inline">Func</code> is a fun specifying a (user-defined) function used to format trace
│ │ │  output. For each system event, the format function is called as
│ │ │  <code class="inline">Func(Dev, Event, Info)</code>, where:<ul><li><code class="inline">Dev</code> is the I/O device to which the output is to be printed. See <a href="../../lib/stdlib-8.0/doc/html/io.html"><code class="inline">io</code></a>
│ │ │  in STDLIB.</li><li><code class="inline">Event</code> and <code class="inline">Info</code> are passed as-is from the call to <a href="../../lib/stdlib-8.0/doc/html/sys.html#handle_debug/4"><code class="inline">sys:handle_debug/4</code></a>.</li></ul></li><li><code class="inline">Info</code> is used to pass more information to <code class="inline">Func</code>. It can be any term, and it
│ │ │  is passed as-is.</li><li><code class="inline">Event</code> is the system event. It is up to the user to define what a system
│ │ │  event is and how it is to be represented. Typically, at least incoming and
│ │ │  outgoing messages are considered system events and represented by the tuples
│ │ │  <code class="inline">{in,Msg[,From]}</code> and <code class="inline">{out,Msg,To[,State]}</code>, respectively.</li></ul><p><a href="../../lib/stdlib-8.0/doc/html/sys.html#handle_debug/4"><code class="inline">sys:handle_debug/4</code></a> returns an updated debug structure <code class="inline">Deb1</code>.</p><p>In the example, <a href="../../lib/stdlib-8.0/doc/html/sys.html#handle_debug/4"><code class="inline">sys:handle_debug/4</code></a> is called for each incoming and
│ │ │  outgoing message. The format function <code class="inline">Func</code> is the function
│ │ │ -<code class="inline">ch4:write_debug/3</code>, which prints the message using <a href="../../lib/stdlib-8.0/doc/html/io.html#format/3"><code class="inline">io:format/3</code></a>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="9391740275-1">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="9391740275-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +<code class="inline">ch4:write_debug/3</code>, which prints the message using <a href="../../lib/stdlib-8.0/doc/html/io.html#format/3"><code class="inline">io:format/3</code></a>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="2841143591-1">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="2841143591-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9391740275-2">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="9391740275-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="9391740275-3">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9391740275-4">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="9391740275-4">}</span><span class="p" data-group-id="9391740275-3">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="9391740275-5">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9391740275-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="9391740275-6">(</span><span class="n">Chs</span><span class="p" data-group-id="9391740275-6">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9391740275-7">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9391740275-7">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">Deb3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="9391740275-8">(</span><span class="n">Deb2</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9391740275-9">{</span><span class="ss">out</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9391740275-10">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9391740275-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="9391740275-9">}</span><span class="p" data-group-id="9391740275-8">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="9391740275-11">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb3</span><span class="p" data-group-id="9391740275-11">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9391740275-12">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9391740275-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="9391740275-13">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9391740275-14">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9391740275-15">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9391740275-15">}</span><span class="p" data-group-id="9391740275-14">}</span><span class="p" data-group-id="9391740275-13">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="9391740275-16">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9391740275-16">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="9391740275-17">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb2</span><span class="p" data-group-id="9391740275-17">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2841143591-2">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="2841143591-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="2841143591-3">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2841143591-4">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="2841143591-4">}</span><span class="p" data-group-id="2841143591-3">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="2841143591-5">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="2841143591-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="2841143591-6">(</span><span class="n">Chs</span><span class="p" data-group-id="2841143591-6">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2841143591-7">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2841143591-7">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">Deb3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="2841143591-8">(</span><span class="n">Deb2</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2841143591-9">{</span><span class="ss">out</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2841143591-10">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2841143591-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="2841143591-9">}</span><span class="p" data-group-id="2841143591-8">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="2841143591-11">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb3</span><span class="p" data-group-id="2841143591-11">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2841143591-12">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2841143591-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="2841143591-13">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2841143591-14">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2841143591-15">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2841143591-15">}</span><span class="p" data-group-id="2841143591-14">}</span><span class="p" data-group-id="2841143591-13">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="2841143591-16">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2841143591-16">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="2841143591-17">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb2</span><span class="p" data-group-id="2841143591-17">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">write_debug</span><span class="p" data-group-id="9391740275-18">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9391740275-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9391740275-19">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> event = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9391740275-20">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="9391740275-20">]</span><span class="p" data-group-id="9391740275-19">)</span><span class="p">.</span></code></pre><p><a href="" id="msg"></a></p><h3 id="handling-system-messages" class="section-heading">
│ │ │ +</span><span class="nf">write_debug</span><span class="p" data-group-id="2841143591-18">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="2841143591-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2841143591-19">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> event = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2841143591-20">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="2841143591-20">]</span><span class="p" data-group-id="2841143591-19">)</span><span class="p">.</span></code></pre><p><a href="" id="msg"></a></p><h3 id="handling-system-messages" class="section-heading">
│ │ │    <a href="#handling-system-messages" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Handling System Messages</span>
│ │ │  </h3>
│ │ │  <p><em>System messages</em> are received as:</p><pre><code class="text">{system, From, Request}</code></pre><p>The content and meaning of these messages are not to be interpreted by the
│ │ │ -process. Instead the following function is to be called:</p><pre><code class="makeup erlang" translate="no"><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="8541727059-1">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8541727059-1">)</span></code></pre><p>The arguments have the following meaning:</p><ul><li><code class="inline">Request</code> and <code class="inline">From</code> from the received system message are to be
│ │ │ +process. Instead the following function is to be called:</p><pre><code class="makeup erlang" translate="no"><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="3781214142-1">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="3781214142-1">)</span></code></pre><p>The arguments have the following meaning:</p><ul><li><code class="inline">Request</code> and <code class="inline">From</code> from the received system message are to be
│ │ │  passed as-is to the call to <a href="../../lib/stdlib-8.0/doc/html/sys.html#handle_system_msg/6"><code class="inline">sys:handle_system_msg/6</code></a>.</li><li><code class="inline">Parent</code> is the pid of the parent process.</li><li><code class="inline">Module</code> is the name of the module implementing the special process.</li><li><code class="inline">Deb</code> is the debug structure.</li><li><code class="inline">State</code> is a term describing the internal state and is passed on to
│ │ │  <code class="inline">Module:system_continue/3</code>, <code class="inline">Module:system_terminate/4</code>,
│ │ │  <code class="inline">Module:system_get_state/1</code>, and <code class="inline">Module:system_replace_state/2</code>.</li></ul><p><a href="../../lib/stdlib-8.0/doc/html/sys.html#handle_system_msg/6"><code class="inline">sys:handle_system_msg/6</code></a> does not return. It handles the system
│ │ │  message and <em>eventually</em> calls either of the following functions:</p><ul><li><p><code class="inline">Module:system_continue(Parent, Deb, State)</code> - if process execution is to
│ │ │  continue.</p></li><li><p><code class="inline">Module:system_terminate(Reason, Parent, Deb, State)</code> - if the
│ │ │  process is to terminate.</p></li></ul><p>While handling the system message, <a href="../../lib/stdlib-8.0/doc/html/sys.html#handle_system_msg/6"><code class="inline">sys:handle_system_msg/6</code></a> can call
│ │ │  one of the following functions:</p><ul><li><p><code class="inline">Module:system_get_state(State)</code> - if the process is to return its state.</p></li><li><p><code class="inline">Module:system_replace_state(StateFun, State)</code> - if the process is
│ │ │  to replace its state using the fun <code class="inline">StateFun</code>. See <a href="../../lib/stdlib-8.0/doc/html/sys.html#replace_state/3"><code class="inline">sys:replace_state/3</code></a>
│ │ │  for more information.</p></li><li><p><code class="inline">system_code_change(Misc, Module, OldVsn, Extra)</code> - if the process is to
│ │ │  perform a code change.</p></li></ul><p>A process in a supervision tree is expected to terminate with the same reason as
│ │ │ -its parent.</p><p>In the example, system messages are handled by the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="9255857790-1">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="9255857790-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +its parent.</p><p>In the example, system messages are handled by the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="1152579109-1">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="1152579109-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -        </span><span class="p" data-group-id="9255857790-2">{</span><span class="ss">system</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="9255857790-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="9255857790-3">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w">
│ │ │ -                                  </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9255857790-3">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="1152579109-2">{</span><span class="ss">system</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="1152579109-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="1152579109-3">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w">
│ │ │ +                                  </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1152579109-3">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_continue</span><span class="p" data-group-id="9255857790-4">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9255857790-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="9255857790-5">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="9255857790-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">system_continue</span><span class="p" data-group-id="1152579109-4">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1152579109-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="1152579109-5">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="1152579109-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_terminate</span><span class="p" data-group-id="9255857790-6">(</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9255857790-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">exit</span><span class="p" data-group-id="9255857790-7">(</span><span class="n">Reason</span><span class="p" data-group-id="9255857790-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">system_terminate</span><span class="p" data-group-id="1152579109-6">(</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1152579109-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">exit</span><span class="p" data-group-id="1152579109-7">(</span><span class="n">Reason</span><span class="p" data-group-id="1152579109-7">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_get_state</span><span class="p" data-group-id="9255857790-8">(</span><span class="n">Chs</span><span class="p" data-group-id="9255857790-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9255857790-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9255857790-9">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">system_get_state</span><span class="p" data-group-id="1152579109-8">(</span><span class="n">Chs</span><span class="p" data-group-id="1152579109-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1152579109-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1152579109-9">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_replace_state</span><span class="p" data-group-id="9255857790-10">(</span><span class="n">StateFun</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9255857790-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">NChs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StateFun</span><span class="p" data-group-id="9255857790-11">(</span><span class="n">Chs</span><span class="p" data-group-id="9255857790-11">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9255857790-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p" data-group-id="9255857790-12">}</span><span class="p">.</span></code></pre><p>If a special process is configured to trap exits, it must take notice
│ │ │ +</span><span class="nf">system_replace_state</span><span class="p" data-group-id="1152579109-10">(</span><span class="n">StateFun</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1152579109-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">NChs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StateFun</span><span class="p" data-group-id="1152579109-11">(</span><span class="n">Chs</span><span class="p" data-group-id="1152579109-11">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1152579109-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p" data-group-id="1152579109-12">}</span><span class="p">.</span></code></pre><p>If a special process is configured to trap exits, it must take notice
│ │ │  of 'EXIT' messages from its parent process and terminate using the
│ │ │ -same exit reason once the parent process has terminated.</p><p>Here is an example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="5704250202-1">(</span><span class="n">Parent</span><span class="p" data-group-id="5704250202-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +same exit reason once the parent process has terminated.</p><p>Here is an example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="6146966560-1">(</span><span class="n">Parent</span><span class="p" data-group-id="6146966560-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="5704250202-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="5704250202-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="6146966560-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="6146966560-2">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="5704250202-3">(</span><span class="n">Parent</span><span class="p" data-group-id="5704250202-3">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="6146966560-3">(</span><span class="n">Parent</span><span class="p" data-group-id="6146966560-3">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="5704250202-4">(</span><span class="n">Parent</span><span class="p" data-group-id="5704250202-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="6146966560-4">(</span><span class="n">Parent</span><span class="p" data-group-id="6146966560-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5704250202-5">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="5704250202-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="6146966560-5">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="6146966560-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="c1">%% Clean up here, if needed.</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="5704250202-6">(</span><span class="n">Reason</span><span class="p" data-group-id="5704250202-6">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="6146966560-6">(</span><span class="n">Reason</span><span class="p" data-group-id="6146966560-6">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><h2 id="user-defined-behaviours" class="section-heading">
│ │ │    <a href="#user-defined-behaviours" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">User-Defined Behaviours</span>
│ │ │  </h2>
│ │ │ @@ -448,71 +448,71 @@
│ │ │  function. Note that the <code class="inline">-optional_callbacks</code> attribute is to be used together
│ │ │  with the <code class="inline">-callback</code> attribute; it cannot be combined with the
│ │ │  <code class="inline">behaviour_info()</code> function described below.</p><p>Tools that need to know about optional callback functions can call
│ │ │  <code class="inline">Behaviour:behaviour_info(optional_callbacks)</code> to get a list of all optional
│ │ │  callback functions.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>We recommend using the <code class="inline">-callback</code> attribute rather than the
│ │ │  <code class="inline">behaviour_info()</code> function. The reason is that the extra type information can
│ │ │  be used by tools to produce documentation or find discrepancies.</p></section><p>As an alternative to the <code class="inline">-callback</code> and <code class="inline">-optional_callbacks</code> attributes you
│ │ │ -may directly implement and export <code class="inline">behaviour_info()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">behaviour_info</span><span class="p" data-group-id="8345486472-1">(</span><span class="ss">callbacks</span><span class="p" data-group-id="8345486472-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8345486472-2">[</span><span class="p" data-group-id="8345486472-3">{</span><span class="n">Name1</span><span class="p">,</span><span class="w"> </span><span class="n">Arity1</span><span class="p" data-group-id="8345486472-3">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="p" data-group-id="8345486472-4">{</span><span class="n">NameN</span><span class="p">,</span><span class="w"> </span><span class="n">ArityN</span><span class="p" data-group-id="8345486472-4">}</span><span class="p" data-group-id="8345486472-2">]</span><span class="p">.</span></code></pre><p>where each <code class="inline">{Name, Arity}</code> specifies the name and arity of a callback function.
│ │ │ +may directly implement and export <code class="inline">behaviour_info()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">behaviour_info</span><span class="p" data-group-id="6109016916-1">(</span><span class="ss">callbacks</span><span class="p" data-group-id="6109016916-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6109016916-2">[</span><span class="p" data-group-id="6109016916-3">{</span><span class="n">Name1</span><span class="p">,</span><span class="w"> </span><span class="n">Arity1</span><span class="p" data-group-id="6109016916-3">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="p" data-group-id="6109016916-4">{</span><span class="n">NameN</span><span class="p">,</span><span class="w"> </span><span class="n">ArityN</span><span class="p" data-group-id="6109016916-4">}</span><span class="p" data-group-id="6109016916-2">]</span><span class="p">.</span></code></pre><p>where each <code class="inline">{Name, Arity}</code> specifies the name and arity of a callback function.
│ │ │  This function is otherwise automatically generated by the compiler using the
│ │ │  <code class="inline">-callback</code> attributes.</p><p>When the compiler encounters the module attribute <code class="inline">-behaviour(Behaviour).</code> in a
│ │ │  module <code class="inline">Mod</code>, it calls <code class="inline">Behaviour:behaviour_info(callbacks)</code> and compares the
│ │ │  result with the set of functions actually exported from <code class="inline">Mod</code>, and issues a
│ │ │  warning if any callback function is missing.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% User-defined behaviour module</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5390065699-1">(</span><span class="ss">simple_server</span><span class="p" data-group-id="5390065699-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5390065699-2">(</span><span class="p" data-group-id="5390065699-3">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="5390065699-3">]</span><span class="p" data-group-id="5390065699-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1332571472-1">(</span><span class="ss">simple_server</span><span class="p" data-group-id="1332571472-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1332571472-2">(</span><span class="p" data-group-id="1332571472-3">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1332571472-3">]</span><span class="p" data-group-id="1332571472-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">init</span><span class="p" data-group-id="5390065699-4">(</span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="5390065699-5">(</span><span class="p" data-group-id="5390065699-5">)</span><span class="p" data-group-id="5390065699-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">&#39;ok&#39;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">handle_req</span><span class="p" data-group-id="5390065699-6">(</span><span class="n">Req</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="5390065699-7">(</span><span class="p" data-group-id="5390065699-7">)</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="5390065699-8">(</span><span class="p" data-group-id="5390065699-8">)</span><span class="p" data-group-id="5390065699-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5390065699-9">{</span><span class="ss">&#39;ok&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="5390065699-10">(</span><span class="p" data-group-id="5390065699-10">)</span><span class="p" data-group-id="5390065699-9">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">terminate</span><span class="p" data-group-id="5390065699-11">(</span><span class="p" data-group-id="5390065699-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">&#39;ok&#39;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">format_state</span><span class="p" data-group-id="5390065699-12">(</span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="5390065699-13">(</span><span class="p" data-group-id="5390065699-13">)</span><span class="p" data-group-id="5390065699-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="5390065699-14">(</span><span class="p" data-group-id="5390065699-14">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">init</span><span class="p" data-group-id="1332571472-4">(</span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="1332571472-5">(</span><span class="p" data-group-id="1332571472-5">)</span><span class="p" data-group-id="1332571472-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">&#39;ok&#39;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">handle_req</span><span class="p" data-group-id="1332571472-6">(</span><span class="n">Req</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="1332571472-7">(</span><span class="p" data-group-id="1332571472-7">)</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="1332571472-8">(</span><span class="p" data-group-id="1332571472-8">)</span><span class="p" data-group-id="1332571472-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1332571472-9">{</span><span class="ss">&#39;ok&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="1332571472-10">(</span><span class="p" data-group-id="1332571472-10">)</span><span class="p" data-group-id="1332571472-9">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">terminate</span><span class="p" data-group-id="1332571472-11">(</span><span class="p" data-group-id="1332571472-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">&#39;ok&#39;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">format_state</span><span class="p" data-group-id="1332571472-12">(</span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="1332571472-13">(</span><span class="p" data-group-id="1332571472-13">)</span><span class="p" data-group-id="1332571472-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="1332571472-14">(</span><span class="p" data-group-id="1332571472-14">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">optional_callbacks</span><span class="p" data-group-id="5390065699-15">(</span><span class="p" data-group-id="5390065699-16">[</span><span class="ss">format_state</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5390065699-16">]</span><span class="p" data-group-id="5390065699-15">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">optional_callbacks</span><span class="p" data-group-id="1332571472-15">(</span><span class="p" data-group-id="1332571472-16">[</span><span class="ss">format_state</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1332571472-16">]</span><span class="p" data-group-id="1332571472-15">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% Alternatively you may define:</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │  </span><span class="c1">%% -export([behaviour_info/1]).</span><span class="w">
│ │ │  </span><span class="c1">%% behaviour_info(callbacks) -&gt;</span><span class="w">
│ │ │  </span><span class="c1">%%     [{init,1},</span><span class="w">
│ │ │  </span><span class="c1">%%      {handle_req,2},</span><span class="w">
│ │ │  </span><span class="c1">%%      {terminate,0}].</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="5390065699-17">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="5390065699-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="5390065699-18">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5390065699-19">[</span><span class="nf">self</span><span class="p" data-group-id="5390065699-20">(</span><span class="p" data-group-id="5390065699-20">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="5390065699-19">]</span><span class="p" data-group-id="5390065699-18">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="1332571472-17">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="1332571472-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="1332571472-18">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1332571472-19">[</span><span class="nf">self</span><span class="p" data-group-id="1332571472-20">(</span><span class="p" data-group-id="1332571472-20">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="1332571472-19">]</span><span class="p" data-group-id="1332571472-18">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="5390065699-21">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="5390065699-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="5390065699-22">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5390065699-23">(</span><span class="p" data-group-id="5390065699-23">)</span><span class="p" data-group-id="5390065699-22">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="1332571472-21">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="1332571472-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="1332571472-22">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1332571472-23">(</span><span class="p" data-group-id="1332571472-23">)</span><span class="p" data-group-id="1332571472-22">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Dbg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="5390065699-24">(</span><span class="p" data-group-id="5390065699-25">[</span><span class="p" data-group-id="5390065699-25">]</span><span class="p" data-group-id="5390065699-24">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="5390065699-26">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5390065699-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5390065699-28">(</span><span class="p" data-group-id="5390065699-28">)</span><span class="p" data-group-id="5390065699-27">}</span><span class="p" data-group-id="5390065699-26">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="5390065699-29">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Dbg</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="5390065699-29">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="n">Dbg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="1332571472-24">(</span><span class="p" data-group-id="1332571472-25">[</span><span class="p" data-group-id="1332571472-25">]</span><span class="p" data-group-id="1332571472-24">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="1332571472-26">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1332571472-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1332571472-28">(</span><span class="p" data-group-id="1332571472-28">)</span><span class="p" data-group-id="1332571472-27">}</span><span class="p" data-group-id="1332571472-26">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="1332571472-29">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Dbg</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1332571472-29">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>In a callback module:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0230321563-1">(</span><span class="ss">db</span><span class="p" data-group-id="0230321563-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="0230321563-2">(</span><span class="ss">simple_server</span><span class="p" data-group-id="0230321563-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>In a callback module:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7597288798-1">(</span><span class="ss">db</span><span class="p" data-group-id="7597288798-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="7597288798-2">(</span><span class="ss">simple_server</span><span class="p" data-group-id="7597288798-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0230321563-3">(</span><span class="p" data-group-id="0230321563-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_req</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0230321563-4">]</span><span class="p" data-group-id="0230321563-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7597288798-3">(</span><span class="p" data-group-id="7597288798-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_req</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7597288798-4">]</span><span class="p" data-group-id="7597288798-3">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>The contracts specified with <code class="inline">-callback</code> attributes in behaviour modules can be
│ │ │  further refined by adding <code class="inline">-spec</code> attributes in callback modules. This can be
│ │ │  useful as <code class="inline">-callback</code> contracts are usually generic. The same callback module
│ │ │ -with contracts for the callbacks:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9841220467-1">(</span><span class="ss">db</span><span class="p" data-group-id="9841220467-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="9841220467-2">(</span><span class="ss">simple_server</span><span class="p" data-group-id="9841220467-2">)</span><span class="p">.</span><span class="w">
│ │ │ +with contracts for the callbacks:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8675878457-1">(</span><span class="ss">db</span><span class="p" data-group-id="8675878457-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="8675878457-2">(</span><span class="ss">simple_server</span><span class="p" data-group-id="8675878457-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9841220467-3">(</span><span class="p" data-group-id="9841220467-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_req</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9841220467-4">]</span><span class="p" data-group-id="9841220467-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8675878457-3">(</span><span class="p" data-group-id="8675878457-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_req</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8675878457-4">]</span><span class="p" data-group-id="8675878457-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9841220467-5">(</span><span class="ss">state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9841220467-6">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="9841220467-7">[</span><span class="nf">atom</span><span class="p" data-group-id="9841220467-8">(</span><span class="p" data-group-id="9841220467-8">)</span><span class="p" data-group-id="9841220467-7">]</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="9841220467-9">(</span><span class="p" data-group-id="9841220467-9">)</span><span class="p" data-group-id="9841220467-6">}</span><span class="p" data-group-id="9841220467-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8675878457-5">(</span><span class="ss">state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8675878457-6">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="8675878457-7">[</span><span class="nf">atom</span><span class="p" data-group-id="8675878457-8">(</span><span class="p" data-group-id="8675878457-8">)</span><span class="p" data-group-id="8675878457-7">]</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="8675878457-9">(</span><span class="p" data-group-id="8675878457-9">)</span><span class="p" data-group-id="8675878457-6">}</span><span class="p" data-group-id="8675878457-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">state</span><span class="p" data-group-id="9841220467-10">(</span><span class="p" data-group-id="9841220467-10">)</span><span class="w">   </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="9841220467-11">{</span><span class="p" data-group-id="9841220467-11">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">request</span><span class="p" data-group-id="9841220467-12">(</span><span class="p" data-group-id="9841220467-12">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="9841220467-13">{</span><span class="ss">&#39;store&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="9841220467-14">(</span><span class="p" data-group-id="9841220467-14">)</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="9841220467-15">(</span><span class="p" data-group-id="9841220467-15">)</span><span class="p" data-group-id="9841220467-13">}</span><span class="p">;</span><span class="w">
│ │ │ -                   </span><span class="p" data-group-id="9841220467-16">{</span><span class="ss">&#39;lookup&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="9841220467-17">(</span><span class="p" data-group-id="9841220467-17">)</span><span class="p" data-group-id="9841220467-16">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">state</span><span class="p" data-group-id="8675878457-10">(</span><span class="p" data-group-id="8675878457-10">)</span><span class="w">   </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="8675878457-11">{</span><span class="p" data-group-id="8675878457-11">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">request</span><span class="p" data-group-id="8675878457-12">(</span><span class="p" data-group-id="8675878457-12">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="8675878457-13">{</span><span class="ss">&#39;store&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8675878457-14">(</span><span class="p" data-group-id="8675878457-14">)</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8675878457-15">(</span><span class="p" data-group-id="8675878457-15">)</span><span class="p" data-group-id="8675878457-13">}</span><span class="p">;</span><span class="w">
│ │ │ +                   </span><span class="p" data-group-id="8675878457-16">{</span><span class="ss">&#39;lookup&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8675878457-17">(</span><span class="p" data-group-id="8675878457-17">)</span><span class="p" data-group-id="8675878457-16">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">handle_req</span><span class="p" data-group-id="9841220467-18">(</span><span class="nf">request</span><span class="p" data-group-id="9841220467-19">(</span><span class="p" data-group-id="9841220467-19">)</span><span class="p">,</span><span class="w"> </span><span class="nf">state</span><span class="p" data-group-id="9841220467-20">(</span><span class="p" data-group-id="9841220467-20">)</span><span class="p" data-group-id="9841220467-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9841220467-21">{</span><span class="ss">&#39;ok&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="9841220467-22">(</span><span class="p" data-group-id="9841220467-22">)</span><span class="p" data-group-id="9841220467-21">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">handle_req</span><span class="p" data-group-id="8675878457-18">(</span><span class="nf">request</span><span class="p" data-group-id="8675878457-19">(</span><span class="p" data-group-id="8675878457-19">)</span><span class="p">,</span><span class="w"> </span><span class="nf">state</span><span class="p" data-group-id="8675878457-20">(</span><span class="p" data-group-id="8675878457-20">)</span><span class="p" data-group-id="8675878457-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8675878457-21">{</span><span class="ss">&#39;ok&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8675878457-22">(</span><span class="p" data-group-id="8675878457-22">)</span><span class="p" data-group-id="8675878457-21">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Each <code class="inline">-spec</code> contract is to be a subtype of the respective <code class="inline">-callback</code> contract.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/statem.html
│ │ │ @@ -124,15 +124,15 @@
│ │ │  </h2>
│ │ │  <p>Established Automata Theory does not deal much with how a <em>state transition</em>
│ │ │  is triggered, but assumes that the output is a function of the input
│ │ │  (and the state) and that they are some kind of values.</p><p>For an Event-Driven State Machine, the input is an <em>event</em> that triggers
│ │ │  a <em>state transition</em> and the output is actions executed during
│ │ │  the <em>state transition</em>.  Analogously to the mathematical model
│ │ │  of a Finite State Machine, it can be described as a set of relations
│ │ │ -of the following form:</p><pre><code class="makeup erlang" translate="no"><span class="n">State</span><span class="p" data-group-id="4307572391-1">(</span><span class="n">S</span><span class="p" data-group-id="4307572391-1">)</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="4307572391-2">(</span><span class="n">E</span><span class="p" data-group-id="4307572391-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Actions</span><span class="p" data-group-id="4307572391-3">(</span><span class="n">A</span><span class="p" data-group-id="4307572391-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4307572391-4">(</span><span class="n">S</span><span class="err">&#39;</span><span class="p" data-group-id="4307572391-4">)</span></code></pre><p>These relations are interpreted as follows: if we are in state <code class="inline">S</code>,
│ │ │ +of the following form:</p><pre><code class="makeup erlang" translate="no"><span class="n">State</span><span class="p" data-group-id="6762108485-1">(</span><span class="n">S</span><span class="p" data-group-id="6762108485-1">)</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="6762108485-2">(</span><span class="n">E</span><span class="p" data-group-id="6762108485-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Actions</span><span class="p" data-group-id="6762108485-3">(</span><span class="n">A</span><span class="p" data-group-id="6762108485-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="6762108485-4">(</span><span class="n">S</span><span class="err">&#39;</span><span class="p" data-group-id="6762108485-4">)</span></code></pre><p>These relations are interpreted as follows: if we are in state <code class="inline">S</code>,
│ │ │  and event <code class="inline">E</code> occurs, we are to perform actions <code class="inline">A</code>, and make a transition
│ │ │  to state <code class="inline">S'</code>.  Notice that <code class="inline">S'</code> can be equal to <code class="inline">S</code>,
│ │ │  and that <code class="inline">A</code> can be empty.</p><p>In <code class="inline">gen_statem</code> we define a <em>state change</em> as a <em>state transition</em> in which the
│ │ │  new state <code class="inline">S'</code> is different from the current state <code class="inline">S</code>, where &quot;different&quot; means
│ │ │  Erlang's strict inequality: <code class="inline">=/=</code> also known as &quot;does not match&quot;. <code class="inline">gen_statem</code>
│ │ │  does more things during <em>state changes</em> than during other <em>state transitions</em>.</p><p>As <code class="inline">A</code> and <code class="inline">S'</code> depend only on <code class="inline">S</code> and <code class="inline">E</code>, the kind of state machine described
│ │ │  here is a Mealy machine (see, for example, the Wikipedia article
│ │ │ @@ -405,20 +405,20 @@
│ │ │    </a>
│ │ │    <span class="text">State Enter Calls</span>
│ │ │  </h2>
│ │ │  <p>The <code class="inline">gen_statem</code> behaviour can, if this is enabled, regardless of <em>callback
│ │ │  mode</em>, automatically call the <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#t:state_enter/0"><em>state callback</em></a>
│ │ │  with special arguments whenever the state changes, so you can write
│ │ │  state enter actions near the rest of the <em>state transition</em> rules.
│ │ │ -It typically looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">StateName</span><span class="p" data-group-id="7412298491-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7412298491-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +It typically looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">StateName</span><span class="p" data-group-id="3885876089-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3885876089-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">enter</span><span class="w"> </span><span class="ss">actions</span><span class="w"> </span><span class="ss">here</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7412298491-2">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">NewData</span><span class="p" data-group-id="7412298491-2">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="n">StateName</span><span class="p" data-group-id="7412298491-3">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7412298491-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3885876089-2">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">NewData</span><span class="p" data-group-id="3885876089-2">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="n">StateName</span><span class="p" data-group-id="3885876089-3">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3885876089-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">actions</span><span class="w"> </span><span class="ss">here</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7412298491-4">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="n">NewStateName</span><span class="p">,</span><span class="w"> </span><span class="n">NewData</span><span class="p" data-group-id="7412298491-4">}</span><span class="p">.</span></code></pre><p>Since the <em>state enter call</em> is not an event there are restrictions on the
│ │ │ +    </span><span class="p" data-group-id="3885876089-4">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="n">NewStateName</span><span class="p">,</span><span class="w"> </span><span class="n">NewData</span><span class="p" data-group-id="3885876089-4">}</span><span class="p">.</span></code></pre><p>Since the <em>state enter call</em> is not an event there are restrictions on the
│ │ │  allowed return value and state <a href="#transition-actions"><em>transition actions</em></a>.
│ │ │  You must not change the state, <a href="#postponing-events">postpone</a> this non-event,
│ │ │  <a href="#inserted-events">insert any events</a>, or change the
│ │ │  <a href="#callback-module"><em>callback module</em></a>.</p><p>The first state that is entered after <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#c:init/1"><code class="inline">gen_statem:init/1</code></a> will get
│ │ │  a <em>state enter call</em> with <code class="inline">OldState</code> equal to the current state.</p><p>You may repeat the <em>state enter call</em> using the <code class="inline">{repeat_state,...}</code> return
│ │ │  value from the <a href="#state-callback"><em>state callback</em></a>. In this case
│ │ │  <code class="inline">OldState</code> will also be equal to the current state.</p><p>Depending on how your state machine is specified, this can be a very useful
│ │ │ @@ -499,72 +499,72 @@
│ │ │  
│ │ │      locked      --&gt; check_code : {button, Button}&lt;br /&gt;* Collect Buttons
│ │ │      check_code  --&gt; locked     : Incorrect code
│ │ │      check_code  --&gt; open       : Correct code&lt;br /&gt;* do_unlock()&lt;br /&gt;* Clear Buttons&lt;br /&gt;* Set state_timeout 10 s
│ │ │  
│ │ │      open        --&gt; open   : {button, Digit}
│ │ │      open        --&gt; locked : state_timeout&lt;br /&gt;* do_lock()</code></pre><p>This code lock state machine can be implemented using <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html"><code class="inline">gen_statem</code></a> with
│ │ │ -the following <em>callback module</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6566399718-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="6566399718-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="6566399718-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="6566399718-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6566399718-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock</span><span class="p" data-group-id="6566399718-3">)</span><span class="p">.</span><span class="w">
│ │ │ +the following <em>callback module</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2148635747-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="2148635747-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="2148635747-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="2148635747-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2148635747-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock</span><span class="p" data-group-id="2148635747-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6566399718-4">(</span><span class="p" data-group-id="6566399718-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6566399718-5">]</span><span class="p" data-group-id="6566399718-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6566399718-6">(</span><span class="p" data-group-id="6566399718-7">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6566399718-7">]</span><span class="p" data-group-id="6566399718-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6566399718-8">(</span><span class="p" data-group-id="6566399718-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="6566399718-9">]</span><span class="p" data-group-id="6566399718-8">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6566399718-10">(</span><span class="p" data-group-id="6566399718-11">[</span><span class="ss">locked</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">open</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="6566399718-11">]</span><span class="p" data-group-id="6566399718-10">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="6566399718-12">(</span><span class="n">Code</span><span class="p" data-group-id="6566399718-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="6566399718-13">(</span><span class="p" data-group-id="6566399718-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="6566399718-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6566399718-15">[</span><span class="p" data-group-id="6566399718-15">]</span><span class="p" data-group-id="6566399718-13">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">button</span><span class="p" data-group-id="6566399718-16">(</span><span class="n">Button</span><span class="p" data-group-id="6566399718-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="6566399718-17">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6566399718-18">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6566399718-18">}</span><span class="p" data-group-id="6566399718-17">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="6566399718-19">(</span><span class="n">Code</span><span class="p" data-group-id="6566399718-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="6566399718-20">(</span><span class="p" data-group-id="6566399718-20">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6566399718-21">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="6566399718-22">(</span><span class="n">Code</span><span class="p" data-group-id="6566399718-22">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6566399718-23">[</span><span class="p" data-group-id="6566399718-23">]</span><span class="p" data-group-id="6566399718-21">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6566399718-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6566399718-24">}</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="6566399718-25">(</span><span class="p" data-group-id="6566399718-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">state_functions</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="3786007310-1">(</span><span class="w">
│ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3786007310-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3786007310-2">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3786007310-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="3786007310-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3786007310-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2148635747-4">(</span><span class="p" data-group-id="2148635747-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2148635747-5">]</span><span class="p" data-group-id="2148635747-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2148635747-6">(</span><span class="p" data-group-id="2148635747-7">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2148635747-7">]</span><span class="p" data-group-id="2148635747-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2148635747-8">(</span><span class="p" data-group-id="2148635747-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="2148635747-9">]</span><span class="p" data-group-id="2148635747-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2148635747-10">(</span><span class="p" data-group-id="2148635747-11">[</span><span class="ss">locked</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">open</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="2148635747-11">]</span><span class="p" data-group-id="2148635747-10">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="2148635747-12">(</span><span class="n">Code</span><span class="p" data-group-id="2148635747-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="2148635747-13">(</span><span class="p" data-group-id="2148635747-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="2148635747-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2148635747-15">[</span><span class="p" data-group-id="2148635747-15">]</span><span class="p" data-group-id="2148635747-13">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">button</span><span class="p" data-group-id="2148635747-16">(</span><span class="n">Button</span><span class="p" data-group-id="2148635747-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="2148635747-17">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2148635747-18">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2148635747-18">}</span><span class="p" data-group-id="2148635747-17">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="2148635747-19">(</span><span class="n">Code</span><span class="p" data-group-id="2148635747-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="2148635747-20">(</span><span class="p" data-group-id="2148635747-20">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2148635747-21">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="2148635747-22">(</span><span class="n">Code</span><span class="p" data-group-id="2148635747-22">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2148635747-23">[</span><span class="p" data-group-id="2148635747-23">]</span><span class="p" data-group-id="2148635747-21">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2148635747-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2148635747-24">}</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="2148635747-25">(</span><span class="p" data-group-id="2148635747-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">state_functions</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="7492214815-1">(</span><span class="w">
│ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7492214815-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7492214815-2">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="7492214815-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="7492214815-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7492214815-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │          </span><span class="k">if</span><span class="w">
│ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="3786007310-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="3786007310-4">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="7492214815-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="7492214815-4">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="3786007310-5">(</span><span class="n">Buttons</span><span class="p" data-group-id="3786007310-5">)</span><span class="w">
│ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="3786007310-6">[</span><span class="n">Button</span><span class="p" data-group-id="3786007310-6">]</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="7492214815-5">(</span><span class="n">Buttons</span><span class="p" data-group-id="7492214815-5">)</span><span class="w">
│ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="7492214815-6">[</span><span class="n">Button</span><span class="p" data-group-id="7492214815-6">]</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="3786007310-7">(</span><span class="p" data-group-id="3786007310-7">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="3786007310-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3786007310-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="3786007310-10">[</span><span class="p" data-group-id="3786007310-10">]</span><span class="p" data-group-id="3786007310-9">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="3786007310-11">[</span><span class="p" data-group-id="3786007310-12">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="3786007310-12">}</span><span class="p" data-group-id="3786007310-11">]</span><span class="p" data-group-id="3786007310-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="7492214815-7">(</span><span class="p" data-group-id="7492214815-7">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="7492214815-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7492214815-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="7492214815-10">[</span><span class="p" data-group-id="7492214815-10">]</span><span class="p" data-group-id="7492214815-9">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="7492214815-11">[</span><span class="p" data-group-id="7492214815-12">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="7492214815-12">}</span><span class="p" data-group-id="7492214815-11">]</span><span class="p" data-group-id="7492214815-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="3786007310-13">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3786007310-14">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="3786007310-14">}</span><span class="p" data-group-id="3786007310-13">}</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="3347684803-1">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w">  </span><span class="n">Data</span><span class="p" data-group-id="3347684803-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="3347684803-2">(</span><span class="p" data-group-id="3347684803-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3347684803-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3347684803-3">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="3347684803-4">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3347684803-5">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="3347684803-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3347684803-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3347684803-6">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3347684803-6">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">do_lock</span><span class="p" data-group-id="3745370230-1">(</span><span class="p" data-group-id="3745370230-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3745370230-2">(</span><span class="s">&quot;Lock</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3745370230-3">[</span><span class="p" data-group-id="3745370230-3">]</span><span class="p" data-group-id="3745370230-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">do_unlock</span><span class="p" data-group-id="3745370230-4">(</span><span class="p" data-group-id="3745370230-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3745370230-5">(</span><span class="s">&quot;Unlock</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3745370230-6">[</span><span class="p" data-group-id="3745370230-6">]</span><span class="p" data-group-id="3745370230-5">)</span><span class="p">.</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="7492214815-13">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7492214815-14">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="7492214815-14">}</span><span class="p" data-group-id="7492214815-13">}</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="8346995444-1">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w">  </span><span class="n">Data</span><span class="p" data-group-id="8346995444-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="8346995444-2">(</span><span class="p" data-group-id="8346995444-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8346995444-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8346995444-3">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="8346995444-4">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8346995444-5">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="8346995444-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8346995444-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8346995444-6">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8346995444-6">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">do_lock</span><span class="p" data-group-id="2790075582-1">(</span><span class="p" data-group-id="2790075582-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2790075582-2">(</span><span class="s">&quot;Lock</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2790075582-3">[</span><span class="p" data-group-id="2790075582-3">]</span><span class="p" data-group-id="2790075582-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">do_unlock</span><span class="p" data-group-id="2790075582-4">(</span><span class="p" data-group-id="2790075582-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2790075582-5">(</span><span class="s">&quot;Unlock</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2790075582-6">[</span><span class="p" data-group-id="2790075582-6">]</span><span class="p" data-group-id="2790075582-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="3745370230-7">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="3745370230-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="3745370230-8">(</span><span class="p" data-group-id="3745370230-8">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="2790075582-7">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="2790075582-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="2790075582-8">(</span><span class="p" data-group-id="2790075582-8">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><h2 id="starting-gen_statem" class="section-heading">
│ │ │    <a href="#starting-gen_statem" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Starting gen_statem</span>
│ │ │  </h2>
│ │ │  <p>In the example in the previous section, <code class="inline">gen_statem</code> is started by calling
│ │ │ -<code class="inline">code_lock:start_link(Code)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="0489032106-1">(</span><span class="n">Code</span><span class="p" data-group-id="0489032106-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="0489032106-2">(</span><span class="p" data-group-id="0489032106-3">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="0489032106-3">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0489032106-4">[</span><span class="p" data-group-id="0489032106-4">]</span><span class="p" data-group-id="0489032106-2">)</span><span class="p">.</span></code></pre><p><code class="inline">start_link/1</code> calls function <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#start_link/4"><code class="inline">gen_statem:start_link/4</code></a>,
│ │ │ +<code class="inline">code_lock:start_link(Code)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="0463602855-1">(</span><span class="n">Code</span><span class="p" data-group-id="0463602855-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="0463602855-2">(</span><span class="p" data-group-id="0463602855-3">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="0463602855-3">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0463602855-4">[</span><span class="p" data-group-id="0463602855-4">]</span><span class="p" data-group-id="0463602855-2">)</span><span class="p">.</span></code></pre><p><code class="inline">start_link/1</code> calls function <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#start_link/4"><code class="inline">gen_statem:start_link/4</code></a>,
│ │ │  which spawns and links to a new process, a <code class="inline">gen_statem</code>.</p><ul><li><p>The first argument, <code class="inline">{local,?NAME}</code>, specifies the name. In this case, the
│ │ │  <code class="inline">gen_statem</code> is locally registered as <code class="inline">code_lock</code> through the macro <code class="inline">?NAME</code>.</p><p>If the name is omitted, the <code class="inline">gen_statem</code> is not registered. Instead its pid
│ │ │  must be used. The name can also be specified as <code class="inline">{global, Name}</code>, then the
│ │ │  <code class="inline">gen_statem</code> is registered using <a href="../../lib/kernel-11.0/doc/html/global.html#register_name/2"><code class="inline">global:register_name/2</code></a> in Kernel.</p></li><li><p>The second argument, <code class="inline">?MODULE</code>, is the name of the <em>callback module</em>,
│ │ │  that is, the module where the callback functions are located,
│ │ │  which is this module.</p><p>The interface functions (<code class="inline">start_link/1</code> and <code class="inline">button/1</code>) are located in the
│ │ │  same module as the callback functions (<code class="inline">init/1</code>, <code class="inline">locked/3</code>, and <code class="inline">open/3</code>).
│ │ │ @@ -574,184 +574,184 @@
│ │ │  see <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#start_link/3"><code class="inline">gen_statem:start_link/3</code></a>.</p></li></ul><p>If name registration succeeds, the new <code class="inline">gen_statem</code> process calls callback
│ │ │  function <code class="inline">code_lock:init(Code)</code>. This function is expected to return
│ │ │  <code class="inline">{ok, State, Data}</code>, where <code class="inline">State</code> is the initial state of the <code class="inline">gen_statem</code>,
│ │ │  in this case <code class="inline">locked</code>; assuming that the door is locked to begin with.
│ │ │  <code class="inline">Data</code> is the internal server data of the <code class="inline">gen_statem</code>. Here the server data
│ │ │  is a <a href="../../lib/stdlib-8.0/doc/html/maps.html"><code class="inline">map()</code></a> with key <code class="inline">code</code> that stores the correct
│ │ │  button sequence, key <code class="inline">length</code> stores its length, and key <code class="inline">buttons</code>
│ │ │ -that stores the collected buttons up to the same length.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="6515535803-1">(</span><span class="n">Code</span><span class="p" data-group-id="6515535803-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="6515535803-2">(</span><span class="p" data-group-id="6515535803-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6515535803-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="6515535803-4">(</span><span class="n">Code</span><span class="p" data-group-id="6515535803-4">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6515535803-5">[</span><span class="p" data-group-id="6515535803-5">]</span><span class="p" data-group-id="6515535803-3">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6515535803-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6515535803-6">}</span><span class="p">.</span></code></pre><p>Function <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#start_link/3"><code class="inline">gen_statem:start_link/3,4</code></a>
│ │ │ +that stores the collected buttons up to the same length.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="9741035045-1">(</span><span class="n">Code</span><span class="p" data-group-id="9741035045-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="9741035045-2">(</span><span class="p" data-group-id="9741035045-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9741035045-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="9741035045-4">(</span><span class="n">Code</span><span class="p" data-group-id="9741035045-4">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9741035045-5">[</span><span class="p" data-group-id="9741035045-5">]</span><span class="p" data-group-id="9741035045-3">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9741035045-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9741035045-6">}</span><span class="p">.</span></code></pre><p>Function <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#start_link/3"><code class="inline">gen_statem:start_link/3,4</code></a>
│ │ │  is synchronous. It does not return until the <code class="inline">gen_statem</code> is initialized
│ │ │  and is ready to receive events.</p><p>Function <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#start_link/3"><code class="inline">gen_statem:start_link/3,4</code></a>
│ │ │  must be used if the <code class="inline">gen_statem</code> is part of a supervision tree, that is,
│ │ │  started by a supervisor.  Function
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#start/3"><code class="inline">gen_statem:start/3,4</code></a> can be used to start
│ │ │  a standalone <code class="inline">gen_statem</code>, meaning it is not part of a supervision tree.</p><p>Function <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#c:callback_mode/0"><code class="inline">Module:callback_mode/0</code></a> selects
│ │ │  the <a href="#callback-modes"><code class="inline">CallbackMode</code></a> for the <em>callback module</em>,
│ │ │  in this case <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#t:callback_mode/0"><code class="inline">state_functions</code></a>.
│ │ │ -That is, each state has its own handler function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">callback_mode</span><span class="p" data-group-id="8591225117-1">(</span><span class="p" data-group-id="8591225117-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +That is, each state has its own handler function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">callback_mode</span><span class="p" data-group-id="5617981193-1">(</span><span class="p" data-group-id="5617981193-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">state_functions</span><span class="p">.</span></code></pre><h2 id="handling-events" class="section-heading">
│ │ │    <a href="#handling-events" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Handling Events</span>
│ │ │  </h2>
│ │ │  <p>The function notifying the code lock about a button event is implemented using
│ │ │ -<a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#cast/2"><code class="inline">gen_statem:cast/2</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">button</span><span class="p" data-group-id="5240853495-1">(</span><span class="n">Button</span><span class="p" data-group-id="5240853495-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="5240853495-2">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5240853495-3">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5240853495-3">}</span><span class="p" data-group-id="5240853495-2">)</span><span class="p">.</span></code></pre><p>The first argument is the name of the <code class="inline">gen_statem</code> and must agree with
│ │ │ +<a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#cast/2"><code class="inline">gen_statem:cast/2</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">button</span><span class="p" data-group-id="3650802038-1">(</span><span class="n">Button</span><span class="p" data-group-id="3650802038-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="3650802038-2">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3650802038-3">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3650802038-3">}</span><span class="p" data-group-id="3650802038-2">)</span><span class="p">.</span></code></pre><p>The first argument is the name of the <code class="inline">gen_statem</code> and must agree with
│ │ │  the name used to start it. So, we use the same macro <code class="inline">?NAME</code> as when starting.
│ │ │  <code class="inline">{button, Button}</code> is the event content.</p><p>The event is sent to the <code class="inline">gen_statem</code>. When the event is received, the
│ │ │  <code class="inline">gen_statem</code> calls <code class="inline">StateName(cast, Event, Data)</code>, which is expected
│ │ │  to return a tuple <code class="inline">{next_state, NewStateName, NewData}</code>, or
│ │ │  <code class="inline">{next_state, NewStateName, NewData, Actions}</code>. <code class="inline">StateName</code> is the name
│ │ │  of the current state and <code class="inline">NewStateName</code> is the name of the next state.
│ │ │  <code class="inline">NewData</code> is a new value for the server data of the <code class="inline">gen_statem</code>,
│ │ │ -and <code class="inline">Actions</code> is a list of actions to be performed by the <code class="inline">gen_statem</code> engine.</p><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="2029520036-1">(</span><span class="w">
│ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2029520036-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2029520036-2">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="2029520036-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="2029520036-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2029520036-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +and <code class="inline">Actions</code> is a list of actions to be performed by the <code class="inline">gen_statem</code> engine.</p><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="3574524161-1">(</span><span class="w">
│ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3574524161-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3574524161-2">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="3574524161-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="3574524161-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3574524161-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │          </span><span class="k">if</span><span class="w">
│ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="2029520036-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="2029520036-4">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="3574524161-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="3574524161-4">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="2029520036-5">(</span><span class="n">Buttons</span><span class="p" data-group-id="2029520036-5">)</span><span class="w">
│ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="2029520036-6">[</span><span class="n">Button</span><span class="p" data-group-id="2029520036-6">]</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="3574524161-5">(</span><span class="n">Buttons</span><span class="p" data-group-id="3574524161-5">)</span><span class="w">
│ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="3574524161-6">[</span><span class="n">Button</span><span class="p" data-group-id="3574524161-6">]</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="2029520036-7">(</span><span class="p" data-group-id="2029520036-7">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="2029520036-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2029520036-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="2029520036-10">[</span><span class="p" data-group-id="2029520036-10">]</span><span class="p" data-group-id="2029520036-9">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="2029520036-11">[</span><span class="p" data-group-id="2029520036-12">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="2029520036-12">}</span><span class="p" data-group-id="2029520036-11">]</span><span class="p" data-group-id="2029520036-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="3574524161-7">(</span><span class="p" data-group-id="3574524161-7">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="3574524161-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3574524161-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="3574524161-10">[</span><span class="p" data-group-id="3574524161-10">]</span><span class="p" data-group-id="3574524161-9">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="3574524161-11">[</span><span class="p" data-group-id="3574524161-12">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="3574524161-12">}</span><span class="p" data-group-id="3574524161-11">]</span><span class="p" data-group-id="3574524161-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="2029520036-13">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2029520036-14">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="2029520036-14">}</span><span class="p" data-group-id="2029520036-13">}</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="3574524161-13">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3574524161-14">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="3574524161-14">}</span><span class="p" data-group-id="3574524161-13">}</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>In state <code class="inline">locked</code>, when a button is pressed, it is collected with the
│ │ │  previously pressed buttons up to the length of the correct code, then
│ │ │  compared with the correct code. Depending on the result, the door is
│ │ │  either unlocked and the <code class="inline">gen_statem</code> goes to state <code class="inline">open</code>, or the door
│ │ │  remains in state <code class="inline">locked</code>.</p><p>When changing to state <code class="inline">open</code>, the collected buttons are reset, the lock
│ │ │ -unlocked, and a <em>state time-out</em> for 10 seconds is started.</p><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="6596530488-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6596530488-2">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6596530488-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6596530488-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6596530488-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6596530488-3">}</span><span class="p">.</span></code></pre><p>In state <code class="inline">open</code>, a button event is ignored by staying in the same state.
│ │ │ +unlocked, and a <em>state time-out</em> for 10 seconds is started.</p><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="4196641463-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4196641463-2">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4196641463-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4196641463-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4196641463-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4196641463-3">}</span><span class="p">.</span></code></pre><p>In state <code class="inline">open</code>, a button event is ignored by staying in the same state.
│ │ │  This can also be done by returning <code class="inline">{keep_state, Data}</code>, or in this case
│ │ │  since <code class="inline">Data</code> is unchanged, by returning <code class="inline">keep_state_and_data</code>.</p><h2 id="state-time-outs" class="section-heading">
│ │ │    <a href="#state-time-outs" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">State Time-Outs</span>
│ │ │  </h2>
│ │ │  <p>When a correct code has been given, the door is unlocked and the following
│ │ │ -tuple is returned from <code class="inline">locked/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8382447031-1">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8382447031-2">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="8382447031-3">[</span><span class="p" data-group-id="8382447031-3">]</span><span class="p" data-group-id="8382447031-2">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8382447031-4">[</span><span class="p" data-group-id="8382447031-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="8382447031-5">}</span><span class="p" data-group-id="8382447031-4">]</span><span class="p" data-group-id="8382447031-1">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span></code></pre><p>10,000 is a time-out value in milliseconds. After this time (10 seconds),
│ │ │ +tuple is returned from <code class="inline">locked/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2729462826-1">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2729462826-2">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="2729462826-3">[</span><span class="p" data-group-id="2729462826-3">]</span><span class="p" data-group-id="2729462826-2">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="2729462826-4">[</span><span class="p" data-group-id="2729462826-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="2729462826-5">}</span><span class="p" data-group-id="2729462826-4">]</span><span class="p" data-group-id="2729462826-1">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span></code></pre><p>10,000 is a time-out value in milliseconds. After this time (10 seconds),
│ │ │  a time-out occurs. Then, <code class="inline">StateName(state_timeout, lock, Data)</code> is called.
│ │ │  The time-out occurs when the door has been in state <code class="inline">open</code> for 10 seconds.
│ │ │ -After that the door is locked again:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="8686578699-1">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w">  </span><span class="n">Data</span><span class="p" data-group-id="8686578699-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="8686578699-2">(</span><span class="p" data-group-id="8686578699-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8686578699-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8686578699-3">}</span><span class="p">;</span></code></pre><p>The timer for a <em>state time-out</em> is automatically canceled when
│ │ │ +After that the door is locked again:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="5801808491-1">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w">  </span><span class="n">Data</span><span class="p" data-group-id="5801808491-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="5801808491-2">(</span><span class="p" data-group-id="5801808491-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5801808491-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5801808491-3">}</span><span class="p">;</span></code></pre><p>The timer for a <em>state time-out</em> is automatically canceled when
│ │ │  the state machine does a <em>state change</em>.</p><p>You can restart, cancel, or update a <em>state time-out</em>. See section
│ │ │  <a href="#time-outs"><em>Time-Outs</em></a> for details.</p><h2 id="all-state-events" class="section-heading">
│ │ │    <a href="#all-state-events" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">All State Events</span>
│ │ │  </h2>
│ │ │  <p>Sometimes events can arrive in any state of the <code class="inline">gen_statem</code>. It is convenient
│ │ │  to handle these in a common state handler function that all state functions
│ │ │  call for events not specific to the state.</p><p>Consider a <code class="inline">code_length/0</code> function that returns the length
│ │ │  of the correct code.  We dispatch all events that are not state-specific
│ │ │  to the common function <code class="inline">handle_common/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2678021211-1">(</span><span class="p" data-group-id="2678021211-2">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2678021211-2">]</span><span class="p" data-group-id="2678021211-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7427205885-1">(</span><span class="p" data-group-id="7427205885-2">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7427205885-2">]</span><span class="p" data-group-id="7427205885-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">code_length</span><span class="p" data-group-id="2678021211-3">(</span><span class="p" data-group-id="2678021211-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="2678021211-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="2678021211-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">code_length</span><span class="p" data-group-id="7427205885-3">(</span><span class="p" data-group-id="7427205885-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="7427205885-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="7427205885-4">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="2678021211-5">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2678021211-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="2678021211-6">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2678021211-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">handle_common</span><span class="p" data-group-id="2678021211-7">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2678021211-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="7427205885-5">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7427205885-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="7427205885-6">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7427205885-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">handle_common</span><span class="p" data-group-id="7427205885-7">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7427205885-7">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="2678021211-8">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2678021211-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="2678021211-9">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2678021211-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">handle_common</span><span class="p" data-group-id="2678021211-10">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2678021211-10">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="2678021211-11">(</span><span class="p" data-group-id="2678021211-12">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="2678021211-12">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2678021211-13">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="2678021211-13">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2678021211-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2678021211-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="2678021211-15">[</span><span class="p" data-group-id="2678021211-16">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="2678021211-17">(</span><span class="n">Code</span><span class="p" data-group-id="2678021211-17">)</span><span class="p" data-group-id="2678021211-16">}</span><span class="p" data-group-id="2678021211-15">]</span><span class="p" data-group-id="2678021211-14">}</span><span class="p">.</span></code></pre><p>Another way to do it is through a convenience macro <code class="inline">?HANDLE_COMMON/0</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7436713049-1">(</span><span class="p" data-group-id="7436713049-2">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7436713049-2">]</span><span class="p" data-group-id="7436713049-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="7427205885-8">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7427205885-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="7427205885-9">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7427205885-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">handle_common</span><span class="p" data-group-id="7427205885-10">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7427205885-10">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="7427205885-11">(</span><span class="p" data-group-id="7427205885-12">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="7427205885-12">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7427205885-13">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="7427205885-13">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7427205885-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7427205885-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="7427205885-15">[</span><span class="p" data-group-id="7427205885-16">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="7427205885-17">(</span><span class="n">Code</span><span class="p" data-group-id="7427205885-17">)</span><span class="p" data-group-id="7427205885-16">}</span><span class="p" data-group-id="7427205885-15">]</span><span class="p" data-group-id="7427205885-14">}</span><span class="p">.</span></code></pre><p>Another way to do it is through a convenience macro <code class="inline">?HANDLE_COMMON/0</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7049561881-1">(</span><span class="p" data-group-id="7049561881-2">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7049561881-2">]</span><span class="p" data-group-id="7049561881-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">code_length</span><span class="p" data-group-id="7436713049-3">(</span><span class="p" data-group-id="7436713049-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="7436713049-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="7436713049-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">code_length</span><span class="p" data-group-id="7049561881-3">(</span><span class="p" data-group-id="7049561881-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="7049561881-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="7049561881-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7436713049-5">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="7436713049-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="7436713049-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="7436713049-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="7436713049-7">)</span><span class="p" data-group-id="7436713049-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7049561881-5">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="7049561881-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="7049561881-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="7049561881-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="7049561881-7">)</span><span class="p" data-group-id="7049561881-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="7436713049-8">(</span><span class="p" data-group-id="7436713049-9">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="7436713049-9">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7436713049-10">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="7436713049-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7436713049-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7436713049-11">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="7436713049-12">[</span><span class="p" data-group-id="7436713049-13">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="7436713049-14">(</span><span class="n">Code</span><span class="p" data-group-id="7436713049-14">)</span><span class="p" data-group-id="7436713049-13">}</span><span class="p" data-group-id="7436713049-12">]</span><span class="p" data-group-id="7436713049-11">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="7049561881-8">(</span><span class="p" data-group-id="7049561881-9">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="7049561881-9">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7049561881-10">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="7049561881-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7049561881-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7049561881-11">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="7049561881-12">[</span><span class="p" data-group-id="7049561881-13">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="7049561881-14">(</span><span class="n">Code</span><span class="p" data-group-id="7049561881-14">)</span><span class="p" data-group-id="7049561881-13">}</span><span class="p" data-group-id="7049561881-12">]</span><span class="p" data-group-id="7049561881-11">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="7436713049-15">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7436713049-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="7049561881-15">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7049561881-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │  </span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="7436713049-16">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7436713049-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="7049561881-16">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7049561881-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │  </span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span></code></pre><p>This example uses <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#call/2"><code class="inline">gen_statem:call/2</code></a>, which waits for a reply from the server.
│ │ │  The reply is sent with a <code class="inline">{reply, From, Reply}</code> tuple in an action list in the
│ │ │  <code class="inline">{keep_state, ...}</code> tuple that retains the current state. This return form is
│ │ │  convenient when you want to stay in the current state but do not know or care
│ │ │  about what it is.</p><p>If the common <em>state callback</em> needs to know the current state a function
│ │ │ -<code class="inline">handle_common/4</code> can be used instead:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3087426439-1">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="3087426439-2">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="3087426439-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="3087426439-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="3087426439-3">)</span><span class="p" data-group-id="3087426439-1">)</span><span class="p">.</span></code></pre><h2 id="one-state-callback" class="section-heading">
│ │ │ +<code class="inline">handle_common/4</code> can be used instead:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6076799198-1">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="6076799198-2">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="6076799198-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="6076799198-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="6076799198-3">)</span><span class="p" data-group-id="6076799198-1">)</span><span class="p">.</span></code></pre><h2 id="one-state-callback" class="section-heading">
│ │ │    <a href="#one-state-callback" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">One State Callback</span>
│ │ │  </h2>
│ │ │  <p>If <a href="#callback-modes"><em>callback mode</em></a> <code class="inline">handle_event_function</code> is used,
│ │ │  all events are handled in
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#c:handle_event/4"><code class="inline">Module:handle_event/4</code></a> and we can
│ │ │  (but do not have to) use an event-centered approach where we first branch
│ │ │  depending on event and then depending on state:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4295079606-1">(</span><span class="p" data-group-id="4295079606-2">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="4295079606-2">]</span><span class="p" data-group-id="4295079606-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3330865959-1">(</span><span class="p" data-group-id="3330865959-2">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="3330865959-2">]</span><span class="p" data-group-id="3330865959-1">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="4295079606-3">(</span><span class="p" data-group-id="4295079606-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="3330865959-3">(</span><span class="p" data-group-id="3330865959-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">handle_event_function</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="4295079606-4">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4295079606-5">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="4295079606-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4295079606-6">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="4295079606-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4295079606-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="3330865959-4">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3330865959-5">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3330865959-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3330865959-6">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="3330865959-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3330865959-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │  	</span><span class="ss">locked</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="4295079606-7">#{</span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="4295079606-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="3330865959-7">#{</span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="3330865959-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │                  </span><span class="k">if</span><span class="w">
│ │ │ -                    </span><span class="nf">length</span><span class="p" data-group-id="4295079606-8">(</span><span class="n">Buttons</span><span class="p" data-group-id="4295079606-8">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                    </span><span class="nf">length</span><span class="p" data-group-id="3330865959-8">(</span><span class="n">Buttons</span><span class="p" data-group-id="3330865959-8">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                          </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │                      </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                        </span><span class="nf">tl</span><span class="p" data-group-id="4295079606-9">(</span><span class="n">Buttons</span><span class="p" data-group-id="4295079606-9">)</span><span class="w">
│ │ │ -                </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="4295079606-10">[</span><span class="n">Button</span><span class="p" data-group-id="4295079606-10">]</span><span class="p">,</span><span class="w">
│ │ │ +                        </span><span class="nf">tl</span><span class="p" data-group-id="3330865959-9">(</span><span class="n">Buttons</span><span class="p" data-group-id="3330865959-9">)</span><span class="w">
│ │ │ +                </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="3330865959-10">[</span><span class="n">Button</span><span class="p" data-group-id="3330865959-10">]</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="k">if</span><span class="w">
│ │ │                  </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -                    </span><span class="nf">do_unlock</span><span class="p" data-group-id="4295079606-11">(</span><span class="p" data-group-id="4295079606-11">)</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="4295079606-12">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4295079606-13">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="4295079606-14">[</span><span class="p" data-group-id="4295079606-14">]</span><span class="p" data-group-id="4295079606-13">}</span><span class="p">,</span><span class="w">
│ │ │ -                     </span><span class="p" data-group-id="4295079606-15">[</span><span class="p" data-group-id="4295079606-16">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="4295079606-16">}</span><span class="p" data-group-id="4295079606-15">]</span><span class="p" data-group-id="4295079606-12">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +                    </span><span class="nf">do_unlock</span><span class="p" data-group-id="3330865959-11">(</span><span class="p" data-group-id="3330865959-11">)</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="3330865959-12">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3330865959-13">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="3330865959-14">[</span><span class="p" data-group-id="3330865959-14">]</span><span class="p" data-group-id="3330865959-13">}</span><span class="p">,</span><span class="w">
│ │ │ +                     </span><span class="p" data-group-id="3330865959-15">[</span><span class="p" data-group-id="3330865959-16">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="3330865959-16">}</span><span class="p" data-group-id="3330865959-15">]</span><span class="p" data-group-id="3330865959-12">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │                  </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="4295079606-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4295079606-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="4295079606-18">}</span><span class="p" data-group-id="4295079606-17">}</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="3330865959-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3330865959-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="3330865959-18">}</span><span class="p" data-group-id="3330865959-17">}</span><span class="w">
│ │ │              </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">open</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">keep_state_and_data</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="4295079606-19">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4295079606-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="4295079606-20">(</span><span class="p" data-group-id="4295079606-20">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4295079606-21">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4295079606-21">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="4295079606-22">(</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="4295079606-23">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="4295079606-23">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4295079606-24">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="4295079606-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4295079606-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4295079606-25">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="4295079606-26">[</span><span class="p" data-group-id="4295079606-27">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="4295079606-28">(</span><span class="n">Code</span><span class="p" data-group-id="4295079606-28">)</span><span class="p" data-group-id="4295079606-27">}</span><span class="p" data-group-id="4295079606-26">]</span><span class="p" data-group-id="4295079606-25">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="3330865959-19">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3330865959-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="3330865959-20">(</span><span class="p" data-group-id="3330865959-20">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3330865959-21">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3330865959-21">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="3330865959-22">(</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="3330865959-23">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="3330865959-23">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3330865959-24">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="3330865959-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3330865959-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3330865959-25">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="3330865959-26">[</span><span class="p" data-group-id="3330865959-27">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="3330865959-28">(</span><span class="n">Code</span><span class="p" data-group-id="3330865959-28">)</span><span class="p" data-group-id="3330865959-27">}</span><span class="p" data-group-id="3330865959-26">]</span><span class="p" data-group-id="3330865959-25">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="stopping" class="section-heading">
│ │ │    <a href="#stopping" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Stopping</span>
│ │ │  </h2>
│ │ │ @@ -763,59 +763,59 @@
│ │ │  </h3>
│ │ │  <p>If the <code class="inline">gen_statem</code> is part of a supervision tree, no stop function is needed.
│ │ │  The <code class="inline">gen_statem</code> is automatically terminated by its supervisor. Exactly how
│ │ │  this is done is defined by a <a href="sup_princ.html#shutdown">shutdown strategy</a>
│ │ │  set in the supervisor.</p><p>If it is necessary to clean up before termination, the shutdown strategy
│ │ │  must be a time-out value and the <code class="inline">gen_statem</code> must in function <code class="inline">init/1</code>
│ │ │  set itself to trap exit signals by calling
│ │ │ -<a href="../../erts-17.0/doc/html/erlang.html#process_flag/2"><code class="inline">process_flag(trap_exit, true)</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="5527857164-1">(</span><span class="n">Args</span><span class="p" data-group-id="5527857164-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="5527857164-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="5527857164-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="5527857164-3">(</span><span class="p" data-group-id="5527857164-3">)</span><span class="p">,</span><span class="w">
│ │ │ +<a href="../../erts-17.0/doc/html/erlang.html#process_flag/2"><code class="inline">process_flag(trap_exit, true)</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="3199562027-1">(</span><span class="n">Args</span><span class="p" data-group-id="3199562027-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="3199562027-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3199562027-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="3199562027-3">(</span><span class="p" data-group-id="3199562027-3">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>When ordered to shut down, the <code class="inline">gen_statem</code> then calls callback function
│ │ │  <code class="inline">terminate(shutdown, State, Data)</code>.</p><p>In this example, function <code class="inline">terminate/3</code> locks the door if it is open,
│ │ │  so we do not accidentally leave the door open
│ │ │ -when the supervision tree terminates:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="1494672791-1">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="1494672791-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="1494672791-2">(</span><span class="p" data-group-id="1494672791-2">)</span><span class="p">,</span><span class="w">
│ │ │ +when the supervision tree terminates:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="2243745428-1">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="2243745428-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="2243745428-2">(</span><span class="p" data-group-id="2243745428-2">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><h3 id="standalone-gen_statem" class="section-heading">
│ │ │    <a href="#standalone-gen_statem" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Standalone gen_statem</span>
│ │ │  </h3>
│ │ │  <p>If the <code class="inline">gen_statem</code> is not part of a supervision tree, it can be stopped
│ │ │  using <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#stop/1"><code class="inline">gen_statem:stop/1</code></a>, preferably through
│ │ │  an API function:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0717188908-1">(</span><span class="p" data-group-id="0717188908-2">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0717188908-2">]</span><span class="p" data-group-id="0717188908-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8448607579-1">(</span><span class="p" data-group-id="8448607579-2">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8448607579-2">]</span><span class="p" data-group-id="8448607579-1">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="0717188908-3">(</span><span class="p" data-group-id="0717188908-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="0717188908-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="0717188908-4">)</span><span class="p">.</span></code></pre><p>This makes the <code class="inline">gen_statem</code> call callback function <code class="inline">terminate/3</code> just like
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="8448607579-3">(</span><span class="p" data-group-id="8448607579-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="8448607579-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="8448607579-4">)</span><span class="p">.</span></code></pre><p>This makes the <code class="inline">gen_statem</code> call callback function <code class="inline">terminate/3</code> just like
│ │ │  for a supervised server and waits for the process to terminate.</p><h2 id="event-time-outs" class="section-heading">
│ │ │    <a href="#event-time-outs" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Event Time-Outs</span>
│ │ │  </h2>
│ │ │  <p>A time-out feature inherited from <code class="inline">gen_statem</code>'s predecessor <a href="../../lib/stdlib-8.0/doc/html/gen_fsm.html"><code class="inline">gen_fsm</code></a>,
│ │ │  is an <em>event time-out</em>, that is, if an event arrives the timer is canceled.
│ │ │  You get either an event or a time-out, but not both.</p><p>It is ordered by the
│ │ │  <a href="#transition-actions"><em>transition action</em></a> <code class="inline">{timeout, Time, EventContent}</code>,
│ │ │  or just an integer <code class="inline">Time</code>, even without the enclosing actions list (the latter
│ │ │  is a form inherited from <code class="inline">gen_fsm</code>).</p><p>This type of time-out is useful, for example, to act on inactivity.
│ │ │  Let's restart the code sequence if no button is pressed for say 30 seconds:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="4573365639-1">(</span><span class="ss">timeout</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4573365639-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4573365639-2">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4573365639-3">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="4573365639-4">[</span><span class="p" data-group-id="4573365639-4">]</span><span class="p" data-group-id="4573365639-3">}</span><span class="p" data-group-id="4573365639-2">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="4573365639-5">(</span><span class="w">
│ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4573365639-6">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="4573365639-6">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="4573365639-7">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="4573365639-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4573365639-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="2682275808-1">(</span><span class="ss">timeout</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2682275808-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2682275808-2">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2682275808-3">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="2682275808-4">[</span><span class="p" data-group-id="2682275808-4">]</span><span class="p" data-group-id="2682275808-3">}</span><span class="p" data-group-id="2682275808-2">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="2682275808-5">(</span><span class="w">
│ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2682275808-6">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2682275808-6">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="2682275808-7">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="2682275808-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2682275808-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="4573365639-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4573365639-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="4573365639-9">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p" data-group-id="4573365639-8">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="2682275808-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2682275808-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="2682275808-9">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p" data-group-id="2682275808-8">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Whenever we receive a button event we start an <em>event time-out</em> of 30 seconds,
│ │ │  and if we get an <em>event type</em> of <code class="inline">timeout</code> we reset the remaining
│ │ │  code sequence.</p><p>An <em>event time-out</em> is canceled by any other event so you either get
│ │ │  some other event or the time-out event. Therefore, canceling,
│ │ │  restarting, or updating an <em>event time-out</em> is neither possible nor
│ │ │  necessary. Whatever event you act on has already canceled
│ │ │  the <em>event time-out</em>, so there is never a running <em>event time-out</em>
│ │ │ @@ -834,30 +834,30 @@
│ │ │  another, maybe cancel the time-out without changing states, or perhaps run
│ │ │  multiple time-outs in parallel. All this can be accomplished with
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#t:generic_timeout/0"><em>generic time-outs</em></a>. They may look a little
│ │ │  bit like <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#t:event_timeout/0"><em>event time-outs</em></a> but contain
│ │ │  a name to allow for any number of them simultaneously and they are
│ │ │  not automatically canceled.</p><p>Here is how to accomplish the <em>state time-out</em> in the previous example
│ │ │  by instead using a <em>generic time-out</em> named for example <code class="inline">open</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="1423693291-1">(</span><span class="w">
│ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1423693291-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1423693291-2">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1423693291-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="1423693291-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1423693291-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="6301628431-1">(</span><span class="w">
│ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6301628431-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6301628431-2">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6301628431-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="6301628431-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6301628431-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="1423693291-4">(</span><span class="p" data-group-id="1423693291-4">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="1423693291-5">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1423693291-6">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="1423693291-7">[</span><span class="p" data-group-id="1423693291-7">]</span><span class="p" data-group-id="1423693291-6">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="1423693291-8">[</span><span class="p" data-group-id="1423693291-9">{</span><span class="p" data-group-id="1423693291-10">{</span><span class="ss">timeout</span><span class="p">,</span><span class="ss">open</span><span class="p" data-group-id="1423693291-10">}</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="1423693291-9">}</span><span class="p" data-group-id="1423693291-8">]</span><span class="p" data-group-id="1423693291-5">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="6301628431-4">(</span><span class="p" data-group-id="6301628431-4">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="6301628431-5">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6301628431-6">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="6301628431-7">[</span><span class="p" data-group-id="6301628431-7">]</span><span class="p" data-group-id="6301628431-6">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="6301628431-8">[</span><span class="p" data-group-id="6301628431-9">{</span><span class="p" data-group-id="6301628431-10">{</span><span class="ss">timeout</span><span class="p">,</span><span class="ss">open</span><span class="p" data-group-id="6301628431-10">}</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="6301628431-9">}</span><span class="p" data-group-id="6301628431-8">]</span><span class="p" data-group-id="6301628431-5">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="1423693291-11">(</span><span class="p" data-group-id="1423693291-12">{</span><span class="ss">timeout</span><span class="p">,</span><span class="ss">open</span><span class="p" data-group-id="1423693291-12">}</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1423693291-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="1423693291-13">(</span><span class="p" data-group-id="1423693291-13">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1423693291-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="ss">locked</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="1423693291-14">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="1423693291-15">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1423693291-16">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1423693291-16">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1423693291-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1423693291-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="1423693291-17">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="6301628431-11">(</span><span class="p" data-group-id="6301628431-12">{</span><span class="ss">timeout</span><span class="p">,</span><span class="ss">open</span><span class="p" data-group-id="6301628431-12">}</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6301628431-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="6301628431-13">(</span><span class="p" data-group-id="6301628431-13">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6301628431-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="ss">locked</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="6301628431-14">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="6301628431-15">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6301628431-16">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6301628431-16">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6301628431-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6301628431-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="6301628431-17">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Specific <em>generic time-outs</em> can just as <a href="#state-time-outs"><em>state time-outs</em></a>
│ │ │  be restarted or canceled by setting it to a new time or <code class="inline">infinity</code>.</p><p>In this particular case we do not need to cancel the time-out since
│ │ │  the time-out event is the only possible reason to do a <em>state change</em>
│ │ │  from <code class="inline">open</code> to <code class="inline">locked</code>.</p><p>Instead of bothering with when to cancel a time-out, a late time-out event
│ │ │  can be handled by ignoring it if it arrives in a state
│ │ │  where it is known to be late.</p><p>You can restart, cancel, or update a <em>generic time-out</em>.
│ │ │  See section <a href="#time-outs"><em>Time-Outs</em></a> for details.</p><h2 id="erlang-timers" class="section-heading">
│ │ │ @@ -869,32 +869,32 @@
│ │ │  <p>The most versatile way to handle time-outs is to use Erlang Timers; see
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#start_timer/4"><code class="inline">erlang:start_timer/3,4</code></a>. Most time-out tasks
│ │ │  can be performed with the time-out features in <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html"><code class="inline">gen_statem</code></a>,
│ │ │  but an example of one that cannot is if you should need the return value
│ │ │  from <a href="../../erts-17.0/doc/html/erlang.html#cancel_timer/2"><code class="inline">erlang:cancel_timer(Tref)</code></a>, that is,
│ │ │  the remaining time of the timer.</p><p>Here is how to accomplish the <em>state time-out</em> in the previous example
│ │ │  by instead using an Erlang Timer:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="8123498067-1">(</span><span class="w">
│ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8123498067-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="8123498067-2">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="8123498067-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="8123498067-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8123498067-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="3308202745-1">(</span><span class="w">
│ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3308202745-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3308202745-2">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="3308202745-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="3308202745-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3308202745-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="8123498067-4">(</span><span class="p" data-group-id="8123498067-4">)</span><span class="p">,</span><span class="w">
│ │ │ +	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="3308202745-4">(</span><span class="p" data-group-id="3308202745-4">)</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="n">Tref</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ -                 </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">start_timer</span><span class="p" data-group-id="8123498067-5">(</span><span class="w">
│ │ │ -                     </span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8123498067-6">(</span><span class="p" data-group-id="8123498067-6">)</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p" data-group-id="8123498067-5">)</span><span class="p">,</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="8123498067-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8123498067-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="8123498067-9">[</span><span class="p" data-group-id="8123498067-9">]</span><span class="p">,</span><span class="w"> </span><span class="ss">timer</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Tref</span><span class="p" data-group-id="8123498067-8">}</span><span class="p" data-group-id="8123498067-7">}</span><span class="p">;</span><span class="w">
│ │ │ +                 </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">start_timer</span><span class="p" data-group-id="3308202745-5">(</span><span class="w">
│ │ │ +                     </span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3308202745-6">(</span><span class="p" data-group-id="3308202745-6">)</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p" data-group-id="3308202745-5">)</span><span class="p">,</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="3308202745-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3308202745-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="3308202745-9">[</span><span class="p" data-group-id="3308202745-9">]</span><span class="p">,</span><span class="w"> </span><span class="ss">timer</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Tref</span><span class="p" data-group-id="3308202745-8">}</span><span class="p" data-group-id="3308202745-7">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="8123498067-10">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8123498067-11">{</span><span class="ss">timeout</span><span class="p">,</span><span class="n">Tref</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="8123498067-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8123498067-12">#{</span><span class="ss">timer</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Tref</span><span class="p" data-group-id="8123498067-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8123498067-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="8123498067-13">(</span><span class="p" data-group-id="8123498067-13">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8123498067-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="ss">locked</span><span class="p">,</span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="8123498067-15">(</span><span class="ss">timer</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8123498067-15">)</span><span class="p" data-group-id="8123498067-14">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="8123498067-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8123498067-17">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="8123498067-17">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8123498067-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8123498067-18">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="8123498067-18">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="3308202745-10">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3308202745-11">{</span><span class="ss">timeout</span><span class="p">,</span><span class="n">Tref</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="3308202745-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3308202745-12">#{</span><span class="ss">timer</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Tref</span><span class="p" data-group-id="3308202745-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3308202745-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="3308202745-13">(</span><span class="p" data-group-id="3308202745-13">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3308202745-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="ss">locked</span><span class="p">,</span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="3308202745-15">(</span><span class="ss">timer</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3308202745-15">)</span><span class="p" data-group-id="3308202745-14">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="3308202745-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3308202745-17">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="3308202745-17">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3308202745-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3308202745-18">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="3308202745-18">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Removing the <code class="inline">timer</code> key from the map when we do a <em>state change</em> to <code class="inline">locked</code>
│ │ │  is not strictly necessary since we can only get into state <code class="inline">open</code>
│ │ │  with an updated <code class="inline">timer</code> map value. But it can be nice to not have
│ │ │  outdated values in the state <code class="inline">Data</code>.</p><p>If you need to cancel a timer because of some other event, you can use
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#cancel_timer/2"><code class="inline">erlang:cancel_timer(Tref)</code></a>. Note that no time-out
│ │ │  message will arrive after this (because the timer has been
│ │ │  explicitly canceled), unless you have already postponed one earlier
│ │ │ @@ -910,16 +910,16 @@
│ │ │    <span class="text">Postponing Events</span>
│ │ │  </h2>
│ │ │  <p>If you want to ignore a particular event in the current state and handle it
│ │ │  in a future state, you can postpone the event. A postponed event
│ │ │  is retried after a <em>state change</em>, that is, <code class="inline">OldState =/= NewState</code>.</p><p>Postponing is ordered by the
│ │ │  <a href="#transition-actions"><em>transition action</em></a> <code class="inline">postpone</code>.</p><p>In this example, instead of ignoring button events while in the <code class="inline">open</code> state,
│ │ │  we can postpone them and handle them later in the <code class="inline">locked</code> state:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="9010247345-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9010247345-2">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9010247345-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9010247345-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9010247345-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p">,</span><span class="p" data-group-id="9010247345-4">[</span><span class="ss">postpone</span><span class="p" data-group-id="9010247345-4">]</span><span class="p" data-group-id="9010247345-3">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="4198274706-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4198274706-2">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4198274706-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4198274706-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4198274706-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p">,</span><span class="p" data-group-id="4198274706-4">[</span><span class="ss">postpone</span><span class="p" data-group-id="4198274706-4">]</span><span class="p" data-group-id="4198274706-3">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Since a postponed event is only retried after a <em>state change</em>, you have to
│ │ │  think about where to keep a state data item. You can keep it in the server
│ │ │  <code class="inline">Data</code> or in the <code class="inline">State</code> itself, for example by having two more or less
│ │ │  identical states to keep a boolean value, or by using a complex state (see
│ │ │  section <a href="#complex-state"><em>Complex State</em></a>) with
│ │ │  <a href="#callback-modes"><em>callback mode</em></a>
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#t:callback_mode/0"><code class="inline">handle_event_function</code></a>. If a change
│ │ │ @@ -940,55 +940,55 @@
│ │ │    <a href="#selective-receive" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Selective Receive</span>
│ │ │  </h3>
│ │ │  <p>Erlang's selective <code class="inline">receive</code> statement is often used to describe simple state
│ │ │  machine examples in straightforward Erlang code. The following is a possible
│ │ │ -implementation of the first example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7761724943-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="7761724943-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7761724943-2">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_1</span><span class="p" data-group-id="7761724943-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7761724943-3">(</span><span class="p" data-group-id="7761724943-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7761724943-4">]</span><span class="p" data-group-id="7761724943-3">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="7761724943-5">(</span><span class="n">Code</span><span class="p" data-group-id="7761724943-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="7761724943-6">(</span><span class="w">
│ │ │ -      </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="7761724943-7">(</span><span class="p" data-group-id="7761724943-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	      </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">register</span><span class="p" data-group-id="7761724943-8">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7761724943-9">(</span><span class="p" data-group-id="7761724943-9">)</span><span class="p" data-group-id="7761724943-8">)</span><span class="p">,</span><span class="w">
│ │ │ -	      </span><span class="nf">do_lock</span><span class="p" data-group-id="7761724943-10">(</span><span class="p" data-group-id="7761724943-10">)</span><span class="p">,</span><span class="w">
│ │ │ -	      </span><span class="nf">locked</span><span class="p" data-group-id="7761724943-11">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="7761724943-12">(</span><span class="n">Code</span><span class="p" data-group-id="7761724943-12">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7761724943-13">[</span><span class="p" data-group-id="7761724943-13">]</span><span class="p" data-group-id="7761724943-11">)</span><span class="w">
│ │ │ -      </span><span class="k">end</span><span class="p" data-group-id="7761724943-6">)</span><span class="p">.</span><span class="w">
│ │ │ +implementation of the first example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3654337865-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="3654337865-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3654337865-2">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_1</span><span class="p" data-group-id="3654337865-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3654337865-3">(</span><span class="p" data-group-id="3654337865-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3654337865-4">]</span><span class="p" data-group-id="3654337865-3">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="3654337865-5">(</span><span class="n">Code</span><span class="p" data-group-id="3654337865-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="3654337865-6">(</span><span class="w">
│ │ │ +      </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="3654337865-7">(</span><span class="p" data-group-id="3654337865-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	      </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">register</span><span class="p" data-group-id="3654337865-8">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3654337865-9">(</span><span class="p" data-group-id="3654337865-9">)</span><span class="p" data-group-id="3654337865-8">)</span><span class="p">,</span><span class="w">
│ │ │ +	      </span><span class="nf">do_lock</span><span class="p" data-group-id="3654337865-10">(</span><span class="p" data-group-id="3654337865-10">)</span><span class="p">,</span><span class="w">
│ │ │ +	      </span><span class="nf">locked</span><span class="p" data-group-id="3654337865-11">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="3654337865-12">(</span><span class="n">Code</span><span class="p" data-group-id="3654337865-12">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3654337865-13">[</span><span class="p" data-group-id="3654337865-13">]</span><span class="p" data-group-id="3654337865-11">)</span><span class="w">
│ │ │ +      </span><span class="k">end</span><span class="p" data-group-id="3654337865-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">button</span><span class="p" data-group-id="7761724943-14">(</span><span class="n">Button</span><span class="p" data-group-id="7761724943-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="o">?</span><span class="n">NAME</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7761724943-15">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7761724943-15">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="0693738420-1">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="0693738420-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">button</span><span class="p" data-group-id="3654337865-14">(</span><span class="n">Button</span><span class="p" data-group-id="3654337865-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="o">?</span><span class="n">NAME</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3654337865-15">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3654337865-15">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="8012132250-1">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="8012132250-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0693738420-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0693738420-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="8012132250-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="8012132250-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │                  </span><span class="k">if</span><span class="w">
│ │ │ -                    </span><span class="nf">length</span><span class="p" data-group-id="0693738420-3">(</span><span class="n">Buttons</span><span class="p" data-group-id="0693738420-3">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                    </span><span class="nf">length</span><span class="p" data-group-id="8012132250-3">(</span><span class="n">Buttons</span><span class="p" data-group-id="8012132250-3">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                          </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │                      </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                        </span><span class="nf">tl</span><span class="p" data-group-id="0693738420-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="0693738420-4">)</span><span class="w">
│ │ │ -                </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="0693738420-5">[</span><span class="n">Button</span><span class="p" data-group-id="0693738420-5">]</span><span class="p">,</span><span class="w">
│ │ │ +                        </span><span class="nf">tl</span><span class="p" data-group-id="8012132250-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="8012132250-4">)</span><span class="w">
│ │ │ +                </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="8012132250-5">[</span><span class="n">Button</span><span class="p" data-group-id="8012132250-5">]</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="k">if</span><span class="w">
│ │ │                  </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -                    </span><span class="nf">do_unlock</span><span class="p" data-group-id="0693738420-6">(</span><span class="p" data-group-id="0693738420-6">)</span><span class="p">,</span><span class="w">
│ │ │ -		    </span><span class="nf">open</span><span class="p" data-group-id="0693738420-7">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="0693738420-7">)</span><span class="p">;</span><span class="w">
│ │ │ +                    </span><span class="nf">do_unlock</span><span class="p" data-group-id="8012132250-6">(</span><span class="p" data-group-id="8012132250-6">)</span><span class="p">,</span><span class="w">
│ │ │ +		    </span><span class="nf">open</span><span class="p" data-group-id="8012132250-7">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="8012132250-7">)</span><span class="p">;</span><span class="w">
│ │ │                  </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ -                    </span><span class="nf">locked</span><span class="p" data-group-id="0693738420-8">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="0693738420-8">)</span><span class="w">
│ │ │ +                    </span><span class="nf">locked</span><span class="p" data-group-id="8012132250-8">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="8012132250-8">)</span><span class="w">
│ │ │              </span><span class="k">end</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="4413428256-1">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="4413428256-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="9868379610-1">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="9868379610-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ -	    </span><span class="nf">do_lock</span><span class="p" data-group-id="4413428256-2">(</span><span class="p" data-group-id="4413428256-2">)</span><span class="p">,</span><span class="w">
│ │ │ -	    </span><span class="nf">locked</span><span class="p" data-group-id="4413428256-3">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4413428256-4">[</span><span class="p" data-group-id="4413428256-4">]</span><span class="p" data-group-id="4413428256-3">)</span><span class="w">
│ │ │ +	    </span><span class="nf">do_lock</span><span class="p" data-group-id="9868379610-2">(</span><span class="p" data-group-id="9868379610-2">)</span><span class="p">,</span><span class="w">
│ │ │ +	    </span><span class="nf">locked</span><span class="p" data-group-id="9868379610-3">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9868379610-4">[</span><span class="p" data-group-id="9868379610-4">]</span><span class="p" data-group-id="9868379610-3">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">do_lock</span><span class="p" data-group-id="4413428256-5">(</span><span class="p" data-group-id="4413428256-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4413428256-6">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4413428256-7">[</span><span class="p" data-group-id="4413428256-7">]</span><span class="p" data-group-id="4413428256-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">do_unlock</span><span class="p" data-group-id="4413428256-8">(</span><span class="p" data-group-id="4413428256-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4413428256-9">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4413428256-10">[</span><span class="p" data-group-id="4413428256-10">]</span><span class="p" data-group-id="4413428256-9">)</span><span class="p">.</span></code></pre><p>The selective receive in this case causes <code class="inline">open</code> to implicitly postpone any
│ │ │ +</span><span class="nf">do_lock</span><span class="p" data-group-id="9868379610-5">(</span><span class="p" data-group-id="9868379610-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9868379610-6">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9868379610-7">[</span><span class="p" data-group-id="9868379610-7">]</span><span class="p" data-group-id="9868379610-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">do_unlock</span><span class="p" data-group-id="9868379610-8">(</span><span class="p" data-group-id="9868379610-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9868379610-9">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9868379610-10">[</span><span class="p" data-group-id="9868379610-10">]</span><span class="p" data-group-id="9868379610-9">)</span><span class="p">.</span></code></pre><p>The selective receive in this case causes <code class="inline">open</code> to implicitly postpone any
│ │ │  events to the <code class="inline">locked</code> state.</p><p>A catch-all receive should never be used from a <code class="inline">gen_statem</code> behaviour
│ │ │  (or from any <code class="inline">gen_*</code> behaviour), as the receive statement is within
│ │ │  the <code class="inline">gen_*</code> engine itself. <a href="../../lib/stdlib-8.0/doc/html/sys.html"><code class="inline">sys</code></a>-compatible behaviours must respond to
│ │ │  system messages and therefore do that in their engine receive loop,
│ │ │  passing non-system messages to the <em>callback module</em>. Using a catch-all
│ │ │  receive can result in system messages being discarded, which in turn
│ │ │  can lead to unexpected behaviour. If a selective receive must be used,
│ │ │ @@ -1011,40 +1011,40 @@
│ │ │  section), especially if only one or a few states have state enter actions,
│ │ │  this is a perfect use case for the built in
│ │ │  <a href="#state-enter-calls"><em>state enter calls</em></a>.</p><p>You return a list containing <code class="inline">state_enter</code> from your
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#c:callback_mode/0"><code class="inline">callback_mode/0</code></a> function and the
│ │ │  <code class="inline">gen_statem</code> engine will call your <em>state callback</em> once with an event
│ │ │  <code class="inline">(enter, OldState, ...)</code> whenever it does a <em>state change</em>. Then you
│ │ │  just need to handle these event-like calls in all states.</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="6506705883-1">(</span><span class="n">Code</span><span class="p" data-group-id="6506705883-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="6506705883-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="6506705883-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6506705883-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="6506705883-4">(</span><span class="n">Code</span><span class="p" data-group-id="6506705883-4">)</span><span class="p" data-group-id="6506705883-3">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6506705883-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6506705883-5">}</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="6506705883-6">(</span><span class="p" data-group-id="6506705883-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6506705883-7">[</span><span class="ss">state_functions</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="6506705883-7">]</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="6506705883-8">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6506705883-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="6506705883-9">(</span><span class="p" data-group-id="6506705883-9">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6506705883-10">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="6506705883-11">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6506705883-12">[</span><span class="p" data-group-id="6506705883-12">]</span><span class="p" data-group-id="6506705883-11">}</span><span class="p" data-group-id="6506705883-10">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="6506705883-13">(</span><span class="w">
│ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6506705883-14">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6506705883-14">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="6506705883-15">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="6506705883-15">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6506705883-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="8948291438-1">(</span><span class="n">Code</span><span class="p" data-group-id="8948291438-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="8948291438-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="8948291438-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8948291438-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="8948291438-4">(</span><span class="n">Code</span><span class="p" data-group-id="8948291438-4">)</span><span class="p" data-group-id="8948291438-3">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8948291438-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8948291438-5">}</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="8948291438-6">(</span><span class="p" data-group-id="8948291438-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8948291438-7">[</span><span class="ss">state_functions</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="8948291438-7">]</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="8948291438-8">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8948291438-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="8948291438-9">(</span><span class="p" data-group-id="8948291438-9">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8948291438-10">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="8948291438-11">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8948291438-12">[</span><span class="p" data-group-id="8948291438-12">]</span><span class="p" data-group-id="8948291438-11">}</span><span class="p" data-group-id="8948291438-10">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="8948291438-13">(</span><span class="w">
│ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8948291438-14">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="8948291438-14">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8948291438-15">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="8948291438-15">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8948291438-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="6506705883-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6506705883-16">}</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="8948291438-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8948291438-16">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="6506705883-17">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="6506705883-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="6506705883-18">(</span><span class="p" data-group-id="6506705883-18">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6506705883-19">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="6506705883-20">[</span><span class="p" data-group-id="6506705883-21">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="6506705883-21">}</span><span class="p" data-group-id="6506705883-20">]</span><span class="p" data-group-id="6506705883-19">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="6506705883-22">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6506705883-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6506705883-23">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6506705883-23">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="8948291438-17">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="8948291438-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="8948291438-18">(</span><span class="p" data-group-id="8948291438-18">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8948291438-19">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="8948291438-20">[</span><span class="p" data-group-id="8948291438-21">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="8948291438-21">}</span><span class="p" data-group-id="8948291438-20">]</span><span class="p" data-group-id="8948291438-19">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="8948291438-22">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8948291438-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8948291438-23">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8948291438-23">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>You can repeat the state enter code by returning one of
│ │ │  <code class="inline">{repeat_state, ...}</code>,<code class="inline">{repeat_state_and_data, _}</code>,
│ │ │  or <code class="inline">repeat_state_and_data</code> that otherwise behaves exactly like their
│ │ │  <code class="inline">keep_state</code> siblings.  See the type
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#t:state_callback_result/2"><code class="inline">state_callback_result()</code></a>
│ │ │  in the Reference Manual.</p><h2 id="inserted-events" class="section-heading">
│ │ │    <a href="#inserted-events" class="hover-link">
│ │ │ @@ -1066,44 +1066,44 @@
│ │ │  to dispatch pre-processed events as internal events to the main state
│ │ │  machine.</p><p>Using internal events also can make it easier to synchronize the state
│ │ │  machines.</p><p>A variant of this is to use a <a href="#complex-state">complex state</a> with
│ │ │  <a href="#one-state-callback">one state callback</a>, modeling the state
│ │ │  with, for example, a tuple <code class="inline">{MainFSMState, SubFSMState}</code>.</p><p>To illustrate this we make up an example where the buttons instead generate
│ │ │  down and up (press and release) events, and the lock responds
│ │ │  to an up event only after the corresponding down event.</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6966617181-1">(</span><span class="p" data-group-id="6966617181-2">[</span><span class="ss">down</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">up</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6966617181-2">]</span><span class="p" data-group-id="6966617181-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3833006019-1">(</span><span class="p" data-group-id="3833006019-2">[</span><span class="ss">down</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">up</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3833006019-2">]</span><span class="p" data-group-id="3833006019-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">down</span><span class="p" data-group-id="6966617181-3">(</span><span class="n">Button</span><span class="p" data-group-id="6966617181-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="6966617181-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6966617181-5">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6966617181-5">}</span><span class="p" data-group-id="6966617181-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">down</span><span class="p" data-group-id="3833006019-3">(</span><span class="n">Button</span><span class="p" data-group-id="3833006019-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="3833006019-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3833006019-5">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3833006019-5">}</span><span class="p" data-group-id="3833006019-4">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">up</span><span class="p" data-group-id="6966617181-6">(</span><span class="n">Button</span><span class="p" data-group-id="6966617181-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="6966617181-7">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6966617181-8">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6966617181-8">}</span><span class="p" data-group-id="6966617181-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">up</span><span class="p" data-group-id="3833006019-6">(</span><span class="n">Button</span><span class="p" data-group-id="3833006019-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="3833006019-7">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3833006019-8">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3833006019-8">}</span><span class="p" data-group-id="3833006019-7">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="6966617181-9">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6966617181-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="6966617181-10">(</span><span class="p" data-group-id="6966617181-10">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6966617181-11">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="6966617181-12">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6966617181-13">[</span><span class="p" data-group-id="6966617181-13">]</span><span class="p" data-group-id="6966617181-12">}</span><span class="p" data-group-id="6966617181-11">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="6966617181-14">(</span><span class="w">
│ │ │ -  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6966617181-15">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6966617181-15">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="6966617181-16">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="6966617181-16">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6966617181-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">handle_common</span><span class="p" data-group-id="7634128416-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7634128416-2">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7634128416-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7634128416-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7634128416-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7634128416-4">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="7634128416-4">}</span><span class="p" data-group-id="7634128416-3">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="7634128416-5">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7634128416-6">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7634128416-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7634128416-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="3833006019-9">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3833006019-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="3833006019-10">(</span><span class="p" data-group-id="3833006019-10">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3833006019-11">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="3833006019-12">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3833006019-13">[</span><span class="p" data-group-id="3833006019-13">]</span><span class="p" data-group-id="3833006019-12">}</span><span class="p" data-group-id="3833006019-11">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="3833006019-14">(</span><span class="w">
│ │ │ +  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3833006019-15">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3833006019-15">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="3833006019-16">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="3833006019-16">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3833006019-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">handle_common</span><span class="p" data-group-id="9241615797-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9241615797-2">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9241615797-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9241615797-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9241615797-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9241615797-4">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="9241615797-4">}</span><span class="p" data-group-id="9241615797-3">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="9241615797-5">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9241615797-6">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9241615797-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9241615797-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Data</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="7634128416-7">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="7634128416-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="7634128416-8">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="7634128416-9">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7634128416-9">)</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="7634128416-10">[</span><span class="p" data-group-id="7634128416-11">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="7634128416-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7634128416-12">}</span><span class="p" data-group-id="7634128416-11">}</span><span class="p" data-group-id="7634128416-10">]</span><span class="p" data-group-id="7634128416-8">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="7634128416-13">#{</span><span class="p" data-group-id="7634128416-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9241615797-7">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="9241615797-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="9241615797-8">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="9241615797-9">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9241615797-9">)</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="9241615797-10">[</span><span class="p" data-group-id="9241615797-11">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="9241615797-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9241615797-12">}</span><span class="p" data-group-id="9241615797-11">}</span><span class="p" data-group-id="9241615797-10">]</span><span class="p" data-group-id="9241615797-8">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9241615797-13">#{</span><span class="p" data-group-id="9241615797-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">keep_state_and_data</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="7634128416-14">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7634128416-15">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="7634128416-15">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7634128416-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7634128416-16">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p">,</span><span class="p" data-group-id="7634128416-17">[</span><span class="ss">postpone</span><span class="p" data-group-id="7634128416-17">]</span><span class="p" data-group-id="7634128416-16">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="9241615797-14">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9241615797-15">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9241615797-15">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9241615797-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9241615797-16">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p">,</span><span class="p" data-group-id="9241615797-17">[</span><span class="ss">postpone</span><span class="p" data-group-id="9241615797-17">]</span><span class="p" data-group-id="9241615797-16">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>If you start this program with <code class="inline">code_lock:start([17])</code> you can unlock with
│ │ │  <code class="inline">code_lock:down(17), code_lock:up(17).</code></p><h2 id="example-revisited" class="section-heading">
│ │ │    <a href="#example-revisited" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Example Revisited</span>
│ │ │  </h2>
│ │ │ @@ -1131,152 +1131,152 @@
│ │ │  Also, the state diagram does not show that the <code class="inline">code_length/0</code> call
│ │ │  must be handled in every state.</p><h3 id="callback-mode-state_functions" class="section-heading">
│ │ │    <a href="#callback-mode-state_functions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Callback Mode: state_functions</span>
│ │ │  </h3>
│ │ │ -<p>Using state functions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9240478529-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="9240478529-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="9240478529-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="9240478529-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9240478529-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_2</span><span class="p" data-group-id="9240478529-3">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Using state functions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6775430656-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="6775430656-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="6775430656-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="6775430656-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6775430656-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_2</span><span class="p" data-group-id="6775430656-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9240478529-4">(</span><span class="p" data-group-id="9240478529-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9240478529-5">]</span><span class="p" data-group-id="9240478529-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9240478529-6">(</span><span class="p" data-group-id="9240478529-7">[</span><span class="ss">down</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">up</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9240478529-7">]</span><span class="p" data-group-id="9240478529-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9240478529-8">(</span><span class="p" data-group-id="9240478529-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="9240478529-9">]</span><span class="p" data-group-id="9240478529-8">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9240478529-10">(</span><span class="p" data-group-id="9240478529-11">[</span><span class="ss">locked</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">open</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="9240478529-11">]</span><span class="p" data-group-id="9240478529-10">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="9240478529-12">(</span><span class="n">Code</span><span class="p" data-group-id="9240478529-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="9240478529-13">(</span><span class="p" data-group-id="9240478529-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="9240478529-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9240478529-15">[</span><span class="p" data-group-id="9240478529-15">]</span><span class="p" data-group-id="9240478529-13">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="9240478529-16">(</span><span class="p" data-group-id="9240478529-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="9240478529-17">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="9240478529-17">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">down</span><span class="p" data-group-id="9240478529-18">(</span><span class="n">Button</span><span class="p" data-group-id="9240478529-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="9240478529-19">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9240478529-20">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9240478529-20">}</span><span class="p" data-group-id="9240478529-19">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">up</span><span class="p" data-group-id="9240478529-21">(</span><span class="n">Button</span><span class="p" data-group-id="9240478529-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="9240478529-22">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9240478529-23">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9240478529-23">}</span><span class="p" data-group-id="9240478529-22">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">code_length</span><span class="p" data-group-id="9240478529-24">(</span><span class="p" data-group-id="9240478529-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="9240478529-25">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="9240478529-25">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="8693375583-1">(</span><span class="n">Code</span><span class="p" data-group-id="8693375583-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="8693375583-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="8693375583-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8693375583-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="8693375583-4">(</span><span class="n">Code</span><span class="p" data-group-id="8693375583-4">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8693375583-5">[</span><span class="p" data-group-id="8693375583-5">]</span><span class="p" data-group-id="8693375583-3">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8693375583-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8693375583-6">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6775430656-4">(</span><span class="p" data-group-id="6775430656-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6775430656-5">]</span><span class="p" data-group-id="6775430656-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6775430656-6">(</span><span class="p" data-group-id="6775430656-7">[</span><span class="ss">down</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">up</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6775430656-7">]</span><span class="p" data-group-id="6775430656-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6775430656-8">(</span><span class="p" data-group-id="6775430656-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="6775430656-9">]</span><span class="p" data-group-id="6775430656-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6775430656-10">(</span><span class="p" data-group-id="6775430656-11">[</span><span class="ss">locked</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">open</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="6775430656-11">]</span><span class="p" data-group-id="6775430656-10">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="6775430656-12">(</span><span class="n">Code</span><span class="p" data-group-id="6775430656-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="6775430656-13">(</span><span class="p" data-group-id="6775430656-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="6775430656-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6775430656-15">[</span><span class="p" data-group-id="6775430656-15">]</span><span class="p" data-group-id="6775430656-13">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="6775430656-16">(</span><span class="p" data-group-id="6775430656-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="6775430656-17">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="6775430656-17">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">down</span><span class="p" data-group-id="6775430656-18">(</span><span class="n">Button</span><span class="p" data-group-id="6775430656-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="6775430656-19">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6775430656-20">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6775430656-20">}</span><span class="p" data-group-id="6775430656-19">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">up</span><span class="p" data-group-id="6775430656-21">(</span><span class="n">Button</span><span class="p" data-group-id="6775430656-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="6775430656-22">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6775430656-23">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6775430656-23">}</span><span class="p" data-group-id="6775430656-22">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">code_length</span><span class="p" data-group-id="6775430656-24">(</span><span class="p" data-group-id="6775430656-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="6775430656-25">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="6775430656-25">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="6478535685-1">(</span><span class="n">Code</span><span class="p" data-group-id="6478535685-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="6478535685-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="6478535685-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6478535685-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="6478535685-4">(</span><span class="n">Code</span><span class="p" data-group-id="6478535685-4">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6478535685-5">[</span><span class="p" data-group-id="6478535685-5">]</span><span class="p" data-group-id="6478535685-3">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6478535685-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6478535685-6">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="8693375583-7">(</span><span class="p" data-group-id="8693375583-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8693375583-8">[</span><span class="ss">state_functions</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="8693375583-8">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="6478535685-7">(</span><span class="p" data-group-id="6478535685-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6478535685-8">[</span><span class="ss">state_functions</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="6478535685-8">]</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8693375583-9">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="8693375583-10">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="8693375583-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="8693375583-11">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="8693375583-11">)</span><span class="p" data-group-id="8693375583-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6478535685-9">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="6478535685-10">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="6478535685-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="6478535685-11">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="6478535685-11">)</span><span class="p" data-group-id="6478535685-9">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="8693375583-12">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8693375583-13">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="8693375583-13">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8693375583-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8693375583-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8693375583-15">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="8693375583-15">}</span><span class="p" data-group-id="8693375583-14">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="8693375583-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8693375583-17">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="8693375583-17">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8693375583-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="6478535685-12">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6478535685-13">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6478535685-13">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6478535685-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6478535685-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6478535685-15">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="6478535685-15">}</span><span class="p" data-group-id="6478535685-14">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="6478535685-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6478535685-17">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6478535685-17">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6478535685-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Data</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="8693375583-18">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="8693375583-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="8693375583-19">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="8693375583-20">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8693375583-20">)</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="8693375583-21">[</span><span class="p" data-group-id="8693375583-22">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="8693375583-23">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="8693375583-23">}</span><span class="p" data-group-id="8693375583-22">}</span><span class="p" data-group-id="8693375583-21">]</span><span class="p" data-group-id="8693375583-19">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="8693375583-24">#{</span><span class="p" data-group-id="8693375583-24">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="6478535685-18">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="6478535685-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="6478535685-19">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="6478535685-20">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6478535685-20">)</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="6478535685-21">[</span><span class="p" data-group-id="6478535685-22">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="6478535685-23">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6478535685-23">}</span><span class="p" data-group-id="6478535685-22">}</span><span class="p" data-group-id="6478535685-21">]</span><span class="p" data-group-id="6478535685-19">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="6478535685-24">#{</span><span class="p" data-group-id="6478535685-24">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">keep_state_and_data</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="8693375583-25">(</span><span class="p" data-group-id="8693375583-26">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="8693375583-26">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8693375583-27">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="8693375583-27">}</span><span class="p" data-group-id="8693375583-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8693375583-28">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="8693375583-29">[</span><span class="p" data-group-id="8693375583-30">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="8693375583-31">(</span><span class="n">Code</span><span class="p" data-group-id="8693375583-31">)</span><span class="p" data-group-id="8693375583-30">}</span><span class="p" data-group-id="8693375583-29">]</span><span class="p" data-group-id="8693375583-28">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="0268134705-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0268134705-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="0268134705-2">(</span><span class="p" data-group-id="0268134705-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0268134705-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0268134705-4">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="0268134705-5">[</span><span class="p" data-group-id="0268134705-5">]</span><span class="p" data-group-id="0268134705-4">}</span><span class="p" data-group-id="0268134705-3">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="0268134705-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0268134705-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0268134705-7">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0268134705-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="0268134705-9">[</span><span class="p" data-group-id="0268134705-9">]</span><span class="p" data-group-id="0268134705-8">}</span><span class="p" data-group-id="0268134705-7">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="0268134705-10">(</span><span class="w">
│ │ │ -  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0268134705-11">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0268134705-11">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="0268134705-12">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="0268134705-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0268134705-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="6478535685-25">(</span><span class="p" data-group-id="6478535685-26">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="6478535685-26">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6478535685-27">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="6478535685-27">}</span><span class="p" data-group-id="6478535685-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6478535685-28">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="6478535685-29">[</span><span class="p" data-group-id="6478535685-30">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="6478535685-31">(</span><span class="n">Code</span><span class="p" data-group-id="6478535685-31">)</span><span class="p" data-group-id="6478535685-30">}</span><span class="p" data-group-id="6478535685-29">]</span><span class="p" data-group-id="6478535685-28">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="8125075019-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8125075019-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="8125075019-2">(</span><span class="p" data-group-id="8125075019-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8125075019-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8125075019-4">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="8125075019-5">[</span><span class="p" data-group-id="8125075019-5">]</span><span class="p" data-group-id="8125075019-4">}</span><span class="p" data-group-id="8125075019-3">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="8125075019-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8125075019-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8125075019-7">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8125075019-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="8125075019-9">[</span><span class="p" data-group-id="8125075019-9">]</span><span class="p" data-group-id="8125075019-8">}</span><span class="p" data-group-id="8125075019-7">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="8125075019-10">(</span><span class="w">
│ │ │ +  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8125075019-11">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="8125075019-11">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8125075019-12">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="8125075019-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8125075019-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │          </span><span class="k">if</span><span class="w">
│ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="0268134705-13">(</span><span class="n">Buttons</span><span class="p" data-group-id="0268134705-13">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="8125075019-13">(</span><span class="n">Buttons</span><span class="p" data-group-id="8125075019-13">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="0268134705-14">(</span><span class="n">Buttons</span><span class="p" data-group-id="0268134705-14">)</span><span class="w">
│ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="0268134705-15">[</span><span class="n">Button</span><span class="p" data-group-id="0268134705-15">]</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="8125075019-14">(</span><span class="n">Buttons</span><span class="p" data-group-id="8125075019-14">)</span><span class="w">
│ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="8125075019-15">[</span><span class="n">Button</span><span class="p" data-group-id="8125075019-15">]</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="0268134705-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0268134705-16">}</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="8125075019-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8125075019-16">}</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="0268134705-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0268134705-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="0268134705-18">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="0268134705-19">[</span><span class="p" data-group-id="0268134705-20">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="0268134705-20">}</span><span class="p" data-group-id="0268134705-19">]</span><span class="p" data-group-id="0268134705-17">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="8125075019-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8125075019-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="8125075019-18">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="8125075019-19">[</span><span class="p" data-group-id="8125075019-20">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="8125075019-20">}</span><span class="p" data-group-id="8125075019-19">]</span><span class="p" data-group-id="8125075019-17">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="2781342061-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="2781342061-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="2781342061-2">(</span><span class="p" data-group-id="2781342061-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2781342061-3">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="2781342061-4">[</span><span class="p" data-group-id="2781342061-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="2781342061-5">}</span><span class="p" data-group-id="2781342061-4">]</span><span class="p" data-group-id="2781342061-3">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="2781342061-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2781342061-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2781342061-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2781342061-7">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="2781342061-8">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2781342061-9">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="2781342061-9">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="2781342061-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2781342061-10">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2781342061-11">[</span><span class="ss">postpone</span><span class="p" data-group-id="2781342061-11">]</span><span class="p" data-group-id="2781342061-10">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="4825934877-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="4825934877-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="4825934877-2">(</span><span class="p" data-group-id="4825934877-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4825934877-3">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="4825934877-4">[</span><span class="p" data-group-id="4825934877-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="4825934877-5">}</span><span class="p" data-group-id="4825934877-4">]</span><span class="p" data-group-id="4825934877-3">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="4825934877-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4825934877-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4825934877-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4825934877-7">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="4825934877-8">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4825934877-9">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4825934877-9">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="4825934877-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4825934877-10">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4825934877-11">[</span><span class="ss">postpone</span><span class="p" data-group-id="4825934877-11">]</span><span class="p" data-group-id="4825934877-10">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">do_lock</span><span class="p" data-group-id="2781342061-12">(</span><span class="p" data-group-id="2781342061-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2781342061-13">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2781342061-14">[</span><span class="p" data-group-id="2781342061-14">]</span><span class="p" data-group-id="2781342061-13">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">do_unlock</span><span class="p" data-group-id="2781342061-15">(</span><span class="p" data-group-id="2781342061-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2781342061-16">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2781342061-17">[</span><span class="p" data-group-id="2781342061-17">]</span><span class="p" data-group-id="2781342061-16">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">do_lock</span><span class="p" data-group-id="4825934877-12">(</span><span class="p" data-group-id="4825934877-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4825934877-13">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4825934877-14">[</span><span class="p" data-group-id="4825934877-14">]</span><span class="p" data-group-id="4825934877-13">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">do_unlock</span><span class="p" data-group-id="4825934877-15">(</span><span class="p" data-group-id="4825934877-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4825934877-16">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4825934877-17">[</span><span class="p" data-group-id="4825934877-17">]</span><span class="p" data-group-id="4825934877-16">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="2781342061-18">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="2781342061-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="2781342061-19">(</span><span class="p" data-group-id="2781342061-19">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="4825934877-18">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="4825934877-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="4825934877-19">(</span><span class="p" data-group-id="4825934877-19">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><h3 id="callback-mode-handle_event_function" class="section-heading">
│ │ │    <a href="#callback-mode-handle_event_function" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Callback Mode: handle_event_function</span>
│ │ │  </h3>
│ │ │  <p>This section describes what to change in the example to use one
│ │ │  <code class="inline">handle_event/4</code> function.  The previously used approach to first branch
│ │ │  depending on event does not work that well here because of
│ │ │ -the <em>state enter calls</em>, so this example first branches depending on state:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3467748082-1">(</span><span class="p" data-group-id="3467748082-2">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="3467748082-2">]</span><span class="p" data-group-id="3467748082-1">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">callback_mode</span><span class="p" data-group-id="2826560358-1">(</span><span class="p" data-group-id="2826560358-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2826560358-2">[</span><span class="ss">handle_event_function</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="2826560358-2">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │ +the <em>state enter calls</em>, so this example first branches depending on state:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4403510105-1">(</span><span class="p" data-group-id="4403510105-2">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="4403510105-2">]</span><span class="p" data-group-id="4403510105-1">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">callback_mode</span><span class="p" data-group-id="4572750276-1">(</span><span class="p" data-group-id="4572750276-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4572750276-2">[</span><span class="ss">handle_event_function</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="4572750276-2">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │  </span><span class="c1">%% State: locked</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="7126829036-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7126829036-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="7126829036-2">(</span><span class="p" data-group-id="7126829036-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7126829036-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7126829036-4">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="7126829036-5">[</span><span class="p" data-group-id="7126829036-5">]</span><span class="p" data-group-id="7126829036-4">}</span><span class="p" data-group-id="7126829036-3">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="7126829036-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7126829036-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7126829036-7">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7126829036-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="7126829036-9">[</span><span class="p" data-group-id="7126829036-9">]</span><span class="p" data-group-id="7126829036-8">}</span><span class="p" data-group-id="7126829036-7">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="7126829036-10">(</span><span class="w">
│ │ │ -  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7126829036-11">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7126829036-11">}</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="7126829036-12">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="7126829036-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7126829036-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1426712801-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1426712801-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="1426712801-2">(</span><span class="p" data-group-id="1426712801-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1426712801-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1426712801-4">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="1426712801-5">[</span><span class="p" data-group-id="1426712801-5">]</span><span class="p" data-group-id="1426712801-4">}</span><span class="p" data-group-id="1426712801-3">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1426712801-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1426712801-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1426712801-7">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1426712801-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="1426712801-9">[</span><span class="p" data-group-id="1426712801-9">]</span><span class="p" data-group-id="1426712801-8">}</span><span class="p" data-group-id="1426712801-7">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1426712801-10">(</span><span class="w">
│ │ │ +  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1426712801-11">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1426712801-11">}</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1426712801-12">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="1426712801-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1426712801-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │          </span><span class="k">if</span><span class="w">
│ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="7126829036-13">(</span><span class="n">Buttons</span><span class="p" data-group-id="7126829036-13">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="1426712801-13">(</span><span class="n">Buttons</span><span class="p" data-group-id="1426712801-13">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="7126829036-14">(</span><span class="n">Buttons</span><span class="p" data-group-id="7126829036-14">)</span><span class="w">
│ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="7126829036-15">[</span><span class="n">Button</span><span class="p" data-group-id="7126829036-15">]</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="1426712801-14">(</span><span class="n">Buttons</span><span class="p" data-group-id="1426712801-14">)</span><span class="w">
│ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="1426712801-15">[</span><span class="n">Button</span><span class="p" data-group-id="1426712801-15">]</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="7126829036-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7126829036-16">}</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="1426712801-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1426712801-16">}</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="7126829036-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7126829036-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="7126829036-18">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="7126829036-19">[</span><span class="p" data-group-id="7126829036-20">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="7126829036-20">}</span><span class="p" data-group-id="7126829036-19">]</span><span class="p" data-group-id="7126829036-17">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="1426712801-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1426712801-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="1426712801-18">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="1426712801-19">[</span><span class="p" data-group-id="1426712801-20">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="1426712801-20">}</span><span class="p" data-group-id="1426712801-19">]</span><span class="p" data-group-id="1426712801-17">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │  </span><span class="c1">%% State: open</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="0486930666-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="0486930666-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="0486930666-2">(</span><span class="p" data-group-id="0486930666-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0486930666-3">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="0486930666-4">[</span><span class="p" data-group-id="0486930666-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="0486930666-5">}</span><span class="p" data-group-id="0486930666-4">]</span><span class="p" data-group-id="0486930666-3">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="0486930666-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0486930666-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0486930666-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0486930666-7">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="0486930666-8">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0486930666-9">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0486930666-9">}</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="0486930666-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0486930666-10">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="p" data-group-id="0486930666-11">[</span><span class="ss">postpone</span><span class="p" data-group-id="0486930666-11">]</span><span class="p" data-group-id="0486930666-10">}</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%% Common events</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="2547806557-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2547806557-2">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2547806557-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2547806557-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2547806557-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2547806557-4">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="2547806557-4">}</span><span class="p" data-group-id="2547806557-3">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="2547806557-5">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2547806557-6">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2547806557-6">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2547806557-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="5671368532-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="5671368532-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="5671368532-2">(</span><span class="p" data-group-id="5671368532-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5671368532-3">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="5671368532-4">[</span><span class="p" data-group-id="5671368532-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="5671368532-5">}</span><span class="p" data-group-id="5671368532-4">]</span><span class="p" data-group-id="5671368532-3">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="5671368532-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5671368532-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5671368532-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5671368532-7">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="5671368532-8">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5671368532-9">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5671368532-9">}</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="5671368532-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5671368532-10">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="p" data-group-id="5671368532-11">[</span><span class="ss">postpone</span><span class="p" data-group-id="5671368532-11">]</span><span class="p" data-group-id="5671368532-10">}</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%% Common events</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="4935696779-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4935696779-2">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="4935696779-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4935696779-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4935696779-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4935696779-4">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="4935696779-4">}</span><span class="p" data-group-id="4935696779-3">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="4935696779-5">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4935696779-6">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="4935696779-6">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4935696779-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Data</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="2547806557-7">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="2547806557-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="2547806557-8">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="2547806557-9">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2547806557-9">)</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="2547806557-10">[</span><span class="p" data-group-id="2547806557-11">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="2547806557-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2547806557-12">}</span><span class="p" data-group-id="2547806557-11">}</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="2547806557-13">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="2547806557-13">}</span><span class="p" data-group-id="2547806557-10">]</span><span class="p" data-group-id="2547806557-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="2547806557-14">#{</span><span class="p" data-group-id="2547806557-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="4935696779-7">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="4935696779-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="4935696779-8">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="4935696779-9">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4935696779-9">)</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="4935696779-10">[</span><span class="p" data-group-id="4935696779-11">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="4935696779-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="4935696779-12">}</span><span class="p" data-group-id="4935696779-11">}</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="4935696779-13">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="4935696779-13">}</span><span class="p" data-group-id="4935696779-10">]</span><span class="p" data-group-id="4935696779-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="4935696779-14">#{</span><span class="p" data-group-id="4935696779-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">keep_state_and_data</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="2547806557-15">(</span><span class="p" data-group-id="2547806557-16">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="2547806557-16">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2547806557-17">#{</span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="2547806557-17">}</span><span class="p" data-group-id="2547806557-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2547806557-18">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="2547806557-19">[</span><span class="p" data-group-id="2547806557-20">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">Length</span><span class="p" data-group-id="2547806557-20">}</span><span class="p" data-group-id="2547806557-19">]</span><span class="p" data-group-id="2547806557-18">}</span><span class="p">.</span></code></pre><p>Notice that postponing buttons from the <code class="inline">open</code> state to the <code class="inline">locked</code> state
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="4935696779-15">(</span><span class="p" data-group-id="4935696779-16">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="4935696779-16">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4935696779-17">#{</span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="4935696779-17">}</span><span class="p" data-group-id="4935696779-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4935696779-18">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="4935696779-19">[</span><span class="p" data-group-id="4935696779-20">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">Length</span><span class="p" data-group-id="4935696779-20">}</span><span class="p" data-group-id="4935696779-19">]</span><span class="p" data-group-id="4935696779-18">}</span><span class="p">.</span></code></pre><p>Notice that postponing buttons from the <code class="inline">open</code> state to the <code class="inline">locked</code> state
│ │ │  seems like a strange thing to do for a code lock, but it at least
│ │ │  illustrates event postponing.</p><h2 id="filter-the-state" class="section-heading">
│ │ │    <a href="#filter-the-state" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Filter the State</span>
│ │ │  </h2>
│ │ │ @@ -1286,30 +1286,30 @@
│ │ │  and which digits that remain to unlock.</p><p>This state data can be regarded as sensitive, and maybe not what you want
│ │ │  in the error log because of some unpredictable event.</p><p>Another reason to filter the state can be that the state is too large to print,
│ │ │  as it fills the error log with uninteresting details.</p><p>To avoid this, you can format the internal state that gets in the error log
│ │ │  and gets returned from <a href="../../lib/stdlib-8.0/doc/html/sys.html#get_status/1"><code class="inline">sys:get_status/1,2</code></a>
│ │ │  by implementing function
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#c:format_status/2"><code class="inline">Module:format_status/2</code></a>,
│ │ │  for example like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9286421368-1">(</span><span class="p" data-group-id="9286421368-2">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">format_status</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9286421368-2">]</span><span class="p" data-group-id="9286421368-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7899098088-1">(</span><span class="p" data-group-id="7899098088-2">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">format_status</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7899098088-2">]</span><span class="p" data-group-id="7899098088-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">format_status</span><span class="p" data-group-id="9286421368-3">(</span><span class="n">Opt</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9286421368-4">[</span><span class="p">_</span><span class="n">PDict</span><span class="p">,</span><span class="n">State</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="9286421368-4">]</span><span class="p" data-group-id="9286421368-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">format_status</span><span class="p" data-group-id="7899098088-3">(</span><span class="n">Opt</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7899098088-4">[</span><span class="p">_</span><span class="n">PDict</span><span class="p">,</span><span class="n">State</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="7899098088-4">]</span><span class="p" data-group-id="7899098088-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">StateData</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="9286421368-5">{</span><span class="n">State</span><span class="p">,</span><span class="w">
│ │ │ -	 </span><span class="nc">maps</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="9286421368-6">(</span><span class="w">
│ │ │ -	   </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="9286421368-7">(</span><span class="ss">code</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9286421368-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">false</span><span class="p">;</span><span class="w">
│ │ │ -	       </span><span class="p" data-group-id="9286421368-8">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9286421368-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">true</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="7899098088-5">{</span><span class="n">State</span><span class="p">,</span><span class="w">
│ │ │ +	 </span><span class="nc">maps</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="7899098088-6">(</span><span class="w">
│ │ │ +	   </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="7899098088-7">(</span><span class="ss">code</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7899098088-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">false</span><span class="p">;</span><span class="w">
│ │ │ +	       </span><span class="p" data-group-id="7899098088-8">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7899098088-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">true</span><span class="w">
│ │ │  	   </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -	   </span><span class="n">Data</span><span class="p" data-group-id="9286421368-6">)</span><span class="p" data-group-id="9286421368-5">}</span><span class="p">,</span><span class="w">
│ │ │ +	   </span><span class="n">Data</span><span class="p" data-group-id="7899098088-6">)</span><span class="p" data-group-id="7899098088-5">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Opt</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │  	</span><span class="ss">terminate</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  	    </span><span class="n">StateData</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">normal</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="p" data-group-id="9286421368-9">[</span><span class="p" data-group-id="9286421368-10">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="9286421368-11">[</span><span class="p" data-group-id="9286421368-12">{</span><span class="s">&quot;State&quot;</span><span class="p">,</span><span class="n">StateData</span><span class="p" data-group-id="9286421368-12">}</span><span class="p" data-group-id="9286421368-11">]</span><span class="p" data-group-id="9286421368-10">}</span><span class="p" data-group-id="9286421368-9">]</span><span class="w">
│ │ │ +	    </span><span class="p" data-group-id="7899098088-9">[</span><span class="p" data-group-id="7899098088-10">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="7899098088-11">[</span><span class="p" data-group-id="7899098088-12">{</span><span class="s">&quot;State&quot;</span><span class="p">,</span><span class="n">StateData</span><span class="p" data-group-id="7899098088-12">}</span><span class="p" data-group-id="7899098088-11">]</span><span class="p" data-group-id="7899098088-10">}</span><span class="p" data-group-id="7899098088-9">]</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>It is not mandatory to implement a
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#c:format_status/2"><code class="inline">Module:format_status/2</code></a> function.
│ │ │  If you do not, a default implementation is used that does the same
│ │ │  as this example function without filtering the <code class="inline">Data</code> term, that is,
│ │ │  <code class="inline">StateData = {State, Data}</code>, in this example containing sensitive information.</p><h2 id="complex-state" class="section-heading">
│ │ │    <a href="#complex-state" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -1322,104 +1322,104 @@
│ │ │  like a tuple.</p><p>One reason to use this is when you have a state item that when changed
│ │ │  should cancel the <a href="#state-time-outs"><em>state time-out</em></a>, or one that affects
│ │ │  the event handling in combination with postponing events. We will go for
│ │ │  the latter and complicate the previous example by introducing
│ │ │  a configurable lock button (this is the state item in question),
│ │ │  which in the <code class="inline">open</code> state immediately locks the door, and an API function
│ │ │  <code class="inline">set_lock_button/1</code> to set the lock button.</p><p>Suppose now that we call <code class="inline">set_lock_button</code> while the door is open,
│ │ │ -and we have already postponed a button event that was the new lock button:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="4566072542-1">(</span><span class="p" data-group-id="4566072542-2">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4566072542-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">x</span><span class="p" data-group-id="4566072542-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4566072542-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.666</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="4566072542-3">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="4566072542-4">(</span><span class="ss">a</span><span class="p" data-group-id="4566072542-4">)</span><span class="p">.</span><span class="w">
│ │ │ +and we have already postponed a button event that was the new lock button:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="9971961672-1">(</span><span class="p" data-group-id="9971961672-2">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="9971961672-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">x</span><span class="p" data-group-id="9971961672-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9971961672-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.666</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="9971961672-3">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="9971961672-4">(</span><span class="ss">a</span><span class="p" data-group-id="9971961672-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="4566072542-5">(</span><span class="ss">b</span><span class="p" data-group-id="4566072542-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="9971961672-5">(</span><span class="ss">b</span><span class="p" data-group-id="9971961672-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="4566072542-6">(</span><span class="ss">c</span><span class="p" data-group-id="4566072542-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="9971961672-6">(</span><span class="ss">c</span><span class="p" data-group-id="9971961672-6">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │  </span><span class="n">Open</span><span class="w">
│ │ │ -</span><span class="gp unselectable">5&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="4566072542-7">(</span><span class="ss">y</span><span class="p" data-group-id="4566072542-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">5&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="9971961672-7">(</span><span class="ss">y</span><span class="p" data-group-id="9971961672-7">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">6&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">set_lock_button</span><span class="p" data-group-id="4566072542-8">(</span><span class="ss">y</span><span class="p" data-group-id="4566072542-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">6&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">set_lock_button</span><span class="p" data-group-id="9971961672-8">(</span><span class="ss">y</span><span class="p" data-group-id="9971961672-8">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">x</span><span class="w">
│ │ │  </span><span class="c1">% What should happen here?  Immediate lock or nothing?</span></code></pre><p>We could say that the button was pressed too early so it should not be
│ │ │  recognized as the lock button. Or we can make the lock button part of
│ │ │  the state so when we then change the lock button in the locked state,
│ │ │  the change becomes a <em>state change</em> and all postponed events are retried,
│ │ │  therefore the lock is immediately locked!</p><p>We define the state as <code class="inline">{StateName, LockButton}</code>, where <code class="inline">StateName</code>
│ │ │ -is as before and <code class="inline">LockButton</code> is the current lock button:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4783132180-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="4783132180-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="4783132180-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="4783132180-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4783132180-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_3</span><span class="p" data-group-id="4783132180-3">)</span><span class="p">.</span><span class="w">
│ │ │ +is as before and <code class="inline">LockButton</code> is the current lock button:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0263605009-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="0263605009-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="0263605009-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="0263605009-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0263605009-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_3</span><span class="p" data-group-id="0263605009-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4783132180-4">(</span><span class="p" data-group-id="4783132180-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4783132180-5">]</span><span class="p" data-group-id="4783132180-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4783132180-6">(</span><span class="p" data-group-id="4783132180-7">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">set_lock_button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4783132180-7">]</span><span class="p" data-group-id="4783132180-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4783132180-8">(</span><span class="p" data-group-id="4783132180-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="4783132180-9">]</span><span class="p" data-group-id="4783132180-8">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4783132180-10">(</span><span class="p" data-group-id="4783132180-11">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="4783132180-11">]</span><span class="p" data-group-id="4783132180-10">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="4783132180-12">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">LockButton</span><span class="p" data-group-id="4783132180-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="4783132180-13">(</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="4783132180-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="4783132180-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4783132180-15">{</span><span class="n">Code</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="4783132180-15">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4783132180-16">[</span><span class="p" data-group-id="4783132180-16">]</span><span class="p" data-group-id="4783132180-13">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="4783132180-17">(</span><span class="p" data-group-id="4783132180-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="4783132180-18">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="4783132180-18">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">button</span><span class="p" data-group-id="4783132180-19">(</span><span class="n">Button</span><span class="p" data-group-id="4783132180-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="4783132180-20">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4783132180-21">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="4783132180-21">}</span><span class="p" data-group-id="4783132180-20">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">set_lock_button</span><span class="p" data-group-id="4783132180-22">(</span><span class="n">LockButton</span><span class="p" data-group-id="4783132180-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="4783132180-23">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4783132180-24">{</span><span class="ss">set_lock_button</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="4783132180-24">}</span><span class="p" data-group-id="4783132180-23">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="5912685412-1">(</span><span class="p" data-group-id="5912685412-2">{</span><span class="n">Code</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="5912685412-2">}</span><span class="p" data-group-id="5912685412-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="5912685412-3">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="5912685412-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5912685412-4">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="5912685412-5">(</span><span class="n">Code</span><span class="p" data-group-id="5912685412-5">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5912685412-6">[</span><span class="p" data-group-id="5912685412-6">]</span><span class="p" data-group-id="5912685412-4">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5912685412-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5912685412-8">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="5912685412-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5912685412-7">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0263605009-4">(</span><span class="p" data-group-id="0263605009-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0263605009-5">]</span><span class="p" data-group-id="0263605009-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0263605009-6">(</span><span class="p" data-group-id="0263605009-7">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">set_lock_button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0263605009-7">]</span><span class="p" data-group-id="0263605009-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0263605009-8">(</span><span class="p" data-group-id="0263605009-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="0263605009-9">]</span><span class="p" data-group-id="0263605009-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0263605009-10">(</span><span class="p" data-group-id="0263605009-11">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="0263605009-11">]</span><span class="p" data-group-id="0263605009-10">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="0263605009-12">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">LockButton</span><span class="p" data-group-id="0263605009-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="0263605009-13">(</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0263605009-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="0263605009-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0263605009-15">{</span><span class="n">Code</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="0263605009-15">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0263605009-16">[</span><span class="p" data-group-id="0263605009-16">]</span><span class="p" data-group-id="0263605009-13">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="0263605009-17">(</span><span class="p" data-group-id="0263605009-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="0263605009-18">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="0263605009-18">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">button</span><span class="p" data-group-id="0263605009-19">(</span><span class="n">Button</span><span class="p" data-group-id="0263605009-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="0263605009-20">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0263605009-21">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0263605009-21">}</span><span class="p" data-group-id="0263605009-20">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">set_lock_button</span><span class="p" data-group-id="0263605009-22">(</span><span class="n">LockButton</span><span class="p" data-group-id="0263605009-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="0263605009-23">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0263605009-24">{</span><span class="ss">set_lock_button</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="0263605009-24">}</span><span class="p" data-group-id="0263605009-23">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="1044711585-1">(</span><span class="p" data-group-id="1044711585-2">{</span><span class="n">Code</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="1044711585-2">}</span><span class="p" data-group-id="1044711585-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="1044711585-3">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="1044711585-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1044711585-4">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="1044711585-5">(</span><span class="n">Code</span><span class="p" data-group-id="1044711585-5">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1044711585-6">[</span><span class="p" data-group-id="1044711585-6">]</span><span class="p" data-group-id="1044711585-4">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1044711585-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1044711585-8">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="1044711585-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1044711585-7">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="5912685412-9">(</span><span class="p" data-group-id="5912685412-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5912685412-10">[</span><span class="ss">handle_event_function</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="5912685412-10">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="1044711585-9">(</span><span class="p" data-group-id="1044711585-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1044711585-10">[</span><span class="ss">handle_event_function</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="1044711585-10">]</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% State: locked</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="5912685412-11">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5912685412-12">{</span><span class="ss">locked</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5912685412-12">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5912685412-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="5912685412-13">(</span><span class="p" data-group-id="5912685412-13">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5912685412-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5912685412-15">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="5912685412-16">[</span><span class="p" data-group-id="5912685412-16">]</span><span class="p" data-group-id="5912685412-15">}</span><span class="p" data-group-id="5912685412-14">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="5912685412-17">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5912685412-18">{</span><span class="ss">locked</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5912685412-18">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5912685412-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5912685412-19">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5912685412-20">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="5912685412-21">[</span><span class="p" data-group-id="5912685412-21">]</span><span class="p" data-group-id="5912685412-20">}</span><span class="p" data-group-id="5912685412-19">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="5912685412-22">(</span><span class="w">
│ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5912685412-23">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5912685412-23">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5912685412-24">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="5912685412-24">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5912685412-25">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="5912685412-25">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5912685412-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1044711585-11">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1044711585-12">{</span><span class="ss">locked</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1044711585-12">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1044711585-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="1044711585-13">(</span><span class="p" data-group-id="1044711585-13">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1044711585-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1044711585-15">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="1044711585-16">[</span><span class="p" data-group-id="1044711585-16">]</span><span class="p" data-group-id="1044711585-15">}</span><span class="p" data-group-id="1044711585-14">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1044711585-17">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1044711585-18">{</span><span class="ss">locked</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1044711585-18">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1044711585-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1044711585-19">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1044711585-20">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="1044711585-21">[</span><span class="p" data-group-id="1044711585-21">]</span><span class="p" data-group-id="1044711585-20">}</span><span class="p" data-group-id="1044711585-19">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1044711585-22">(</span><span class="w">
│ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1044711585-23">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1044711585-23">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1044711585-24">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="1044711585-24">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1044711585-25">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="1044711585-25">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1044711585-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │          </span><span class="k">if</span><span class="w">
│ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="5912685412-26">(</span><span class="n">Buttons</span><span class="p" data-group-id="5912685412-26">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="1044711585-26">(</span><span class="n">Buttons</span><span class="p" data-group-id="1044711585-26">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="5912685412-27">(</span><span class="n">Buttons</span><span class="p" data-group-id="5912685412-27">)</span><span class="w">
│ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="5912685412-28">[</span><span class="n">Button</span><span class="p" data-group-id="5912685412-28">]</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="1044711585-27">(</span><span class="n">Buttons</span><span class="p" data-group-id="1044711585-27">)</span><span class="w">
│ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="1044711585-28">[</span><span class="n">Button</span><span class="p" data-group-id="1044711585-28">]</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="5912685412-29">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5912685412-30">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="5912685412-30">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5912685412-29">}</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="1044711585-29">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1044711585-30">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="1044711585-30">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1044711585-29">}</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="5912685412-31">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5912685412-32">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="5912685412-32">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="5912685412-33">[</span><span class="p" data-group-id="5912685412-34">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="5912685412-34">}</span><span class="p" data-group-id="5912685412-33">]</span><span class="p" data-group-id="5912685412-31">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="1044711585-31">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1044711585-32">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="1044711585-32">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="1044711585-33">[</span><span class="p" data-group-id="1044711585-34">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="1044711585-34">}</span><span class="p" data-group-id="1044711585-33">]</span><span class="p" data-group-id="1044711585-31">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │  </span><span class="c1">%% State: open</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="4191334405-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4191334405-2">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4191334405-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="4191334405-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="4191334405-3">(</span><span class="p" data-group-id="4191334405-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4191334405-4">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="4191334405-5">[</span><span class="p" data-group-id="4191334405-6">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="4191334405-6">}</span><span class="p" data-group-id="4191334405-5">]</span><span class="p" data-group-id="4191334405-4">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="4191334405-7">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4191334405-8">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="4191334405-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4191334405-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4191334405-9">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4191334405-10">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="4191334405-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4191334405-9">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="4191334405-11">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4191334405-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="4191334405-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4191334405-13">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="4191334405-13">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4191334405-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4191334405-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4191334405-15">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="4191334405-15">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4191334405-14">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="4191334405-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4191334405-17">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4191334405-17">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4191334405-18">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4191334405-18">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="4191334405-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4191334405-19">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="p" data-group-id="4191334405-20">[</span><span class="ss">postpone</span><span class="p" data-group-id="4191334405-20">]</span><span class="p" data-group-id="4191334405-19">}</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="6175629023-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6175629023-2">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6175629023-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="6175629023-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="6175629023-3">(</span><span class="p" data-group-id="6175629023-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6175629023-4">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="6175629023-5">[</span><span class="p" data-group-id="6175629023-6">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="6175629023-6">}</span><span class="p" data-group-id="6175629023-5">]</span><span class="p" data-group-id="6175629023-4">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="6175629023-7">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6175629023-8">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6175629023-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6175629023-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6175629023-9">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6175629023-10">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6175629023-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6175629023-9">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="6175629023-11">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6175629023-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6175629023-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6175629023-13">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6175629023-13">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6175629023-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6175629023-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6175629023-15">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6175629023-15">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6175629023-14">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="6175629023-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6175629023-17">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6175629023-17">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6175629023-18">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6175629023-18">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="6175629023-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6175629023-19">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="p" data-group-id="6175629023-20">[</span><span class="ss">postpone</span><span class="p" data-group-id="6175629023-20">]</span><span class="p" data-group-id="6175629023-19">}</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │  </span><span class="c1">%% Common events</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="4356081858-1">(</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="4356081858-2">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="4356081858-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4356081858-3">{</span><span class="ss">set_lock_button</span><span class="p">,</span><span class="n">NewLockButton</span><span class="p" data-group-id="4356081858-3">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="4356081858-4">{</span><span class="n">StateName</span><span class="p">,</span><span class="n">OldLockButton</span><span class="p" data-group-id="4356081858-4">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4356081858-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4356081858-5">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4356081858-6">{</span><span class="n">StateName</span><span class="p">,</span><span class="n">NewLockButton</span><span class="p" data-group-id="4356081858-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="4356081858-7">[</span><span class="p" data-group-id="4356081858-8">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">OldLockButton</span><span class="p" data-group-id="4356081858-8">}</span><span class="p" data-group-id="4356081858-7">]</span><span class="p" data-group-id="4356081858-5">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">do_lock</span><span class="p" data-group-id="3612948103-1">(</span><span class="p" data-group-id="3612948103-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3612948103-2">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3612948103-3">[</span><span class="p" data-group-id="3612948103-3">]</span><span class="p" data-group-id="3612948103-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">do_unlock</span><span class="p" data-group-id="3612948103-4">(</span><span class="p" data-group-id="3612948103-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3612948103-5">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3612948103-6">[</span><span class="p" data-group-id="3612948103-6">]</span><span class="p" data-group-id="3612948103-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="5493118159-1">(</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="5493118159-2">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="5493118159-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5493118159-3">{</span><span class="ss">set_lock_button</span><span class="p">,</span><span class="n">NewLockButton</span><span class="p" data-group-id="5493118159-3">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="5493118159-4">{</span><span class="n">StateName</span><span class="p">,</span><span class="n">OldLockButton</span><span class="p" data-group-id="5493118159-4">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5493118159-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5493118159-5">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5493118159-6">{</span><span class="n">StateName</span><span class="p">,</span><span class="n">NewLockButton</span><span class="p" data-group-id="5493118159-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="5493118159-7">[</span><span class="p" data-group-id="5493118159-8">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">OldLockButton</span><span class="p" data-group-id="5493118159-8">}</span><span class="p" data-group-id="5493118159-7">]</span><span class="p" data-group-id="5493118159-5">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">do_lock</span><span class="p" data-group-id="0433388394-1">(</span><span class="p" data-group-id="0433388394-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0433388394-2">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0433388394-3">[</span><span class="p" data-group-id="0433388394-3">]</span><span class="p" data-group-id="0433388394-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">do_unlock</span><span class="p" data-group-id="0433388394-4">(</span><span class="p" data-group-id="0433388394-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0433388394-5">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0433388394-6">[</span><span class="p" data-group-id="0433388394-6">]</span><span class="p" data-group-id="0433388394-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="3612948103-7">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="3612948103-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="3612948103-8">(</span><span class="p" data-group-id="3612948103-8">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="0433388394-7">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="0433388394-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="0433388394-8">(</span><span class="p" data-group-id="0433388394-8">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><h2 id="hibernation" class="section-heading">
│ │ │    <a href="#hibernation" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Hibernation</span>
│ │ │  </h2>
│ │ │  <p>If you have many servers in one node and they have some state(s) in their
│ │ │ @@ -1428,19 +1428,19 @@
│ │ │  footprint of a server can be minimized by hibernating it through
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/proc_lib.html#hibernate/3"><code class="inline">proc_lib:hibernate/3</code></a>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>It is rather costly to hibernate a process; see <a href="../../erts-17.0/doc/html/erlang.html#hibernate/3"><code class="inline">erlang:hibernate/3</code></a>. It is
│ │ │  not something you want to do after every event.</p></section><p>We can in this example hibernate in the <code class="inline">{open, _}</code> state,
│ │ │  because what normally occurs in that state is that the <em>state time-out</em>
│ │ │  after a while triggers a transition to <code class="inline">{locked, _}</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │  </span><span class="c1">%% State: open</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="7944793364-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7944793364-2">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="7944793364-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="7944793364-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="7944793364-3">(</span><span class="p" data-group-id="7944793364-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7944793364-4">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="7944793364-5">[</span><span class="p" data-group-id="7944793364-6">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="7944793364-6">}</span><span class="p">,</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ -      </span><span class="ss">hibernate</span><span class="p" data-group-id="7944793364-5">]</span><span class="p" data-group-id="7944793364-4">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="0323622072-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0323622072-2">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0323622072-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="0323622072-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="0323622072-3">(</span><span class="p" data-group-id="0323622072-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0323622072-4">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="0323622072-5">[</span><span class="p" data-group-id="0323622072-6">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="0323622072-6">}</span><span class="p">,</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +      </span><span class="ss">hibernate</span><span class="p" data-group-id="0323622072-5">]</span><span class="p" data-group-id="0323622072-4">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>The atom <a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#t:hibernate/0"><code class="inline">hibernate</code></a> in the action list on the
│ │ │  last line when entering the <code class="inline">{open, _}</code> state is the only change. If any event
│ │ │  arrives in the <code class="inline">{open, _},</code> state, we do not bother to rehibernate,
│ │ │  so the server stays awake after any event.</p><p>To change that we would need to insert action <code class="inline">hibernate</code> in more places.
│ │ │  For example, the state-independent <code class="inline">set_lock_button</code> operation
│ │ │  would have to use <code class="inline">hibernate</code> but only in the <code class="inline">{open, _}</code> state,
│ │ │  which would clutter the code.</p><p>Another not uncommon scenario is to use the
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/sup_princ.html
│ │ │ @@ -128,48 +128,48 @@
│ │ │  the order specified by this list, and are terminated in the reverse order.</p><h2 id="example" class="section-heading">
│ │ │    <a href="#example" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Example</span>
│ │ │  </h2>
│ │ │  <p>The callback module for a supervisor starting the server from
│ │ │ -<a href="gen_server_concepts.html#ex">gen_server Behaviour</a> can look as follows:</p><p><a href="" id="ex"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5288235649-1">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="5288235649-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="5288235649-2">(</span><span class="ss">supervisor</span><span class="p" data-group-id="5288235649-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<a href="gen_server_concepts.html#ex">gen_server Behaviour</a> can look as follows:</p><p><a href="" id="ex"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3635053359-1">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="3635053359-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="3635053359-2">(</span><span class="ss">supervisor</span><span class="p" data-group-id="3635053359-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5288235649-3">(</span><span class="p" data-group-id="5288235649-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5288235649-4">]</span><span class="p" data-group-id="5288235649-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5288235649-5">(</span><span class="p" data-group-id="5288235649-6">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5288235649-6">]</span><span class="p" data-group-id="5288235649-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3635053359-3">(</span><span class="p" data-group-id="3635053359-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3635053359-4">]</span><span class="p" data-group-id="3635053359-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3635053359-5">(</span><span class="p" data-group-id="3635053359-6">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3635053359-6">]</span><span class="p" data-group-id="3635053359-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="5288235649-7">(</span><span class="p" data-group-id="5288235649-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="5288235649-8">(</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5288235649-9">[</span><span class="p" data-group-id="5288235649-9">]</span><span class="p" data-group-id="5288235649-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="3635053359-7">(</span><span class="p" data-group-id="3635053359-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="3635053359-8">(</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3635053359-9">[</span><span class="p" data-group-id="3635053359-9">]</span><span class="p" data-group-id="3635053359-8">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="5288235649-10">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="5288235649-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5288235649-11">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">one_for_one</span><span class="p">,</span><span class="w"> </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="5288235649-11">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5288235649-12">[</span><span class="p" data-group-id="5288235649-13">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5288235649-14">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5288235649-15">[</span><span class="p" data-group-id="5288235649-15">]</span><span class="p" data-group-id="5288235649-14">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="3635053359-10">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="3635053359-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3635053359-11">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">one_for_one</span><span class="p">,</span><span class="w"> </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="3635053359-11">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3635053359-12">[</span><span class="p" data-group-id="3635053359-13">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3635053359-14">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3635053359-15">[</span><span class="p" data-group-id="3635053359-15">]</span><span class="p" data-group-id="3635053359-14">}</span><span class="p">,</span><span class="w">
│ │ │                      </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">permanent</span><span class="p">,</span><span class="w">
│ │ │                      </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p">,</span><span class="w">
│ │ │                      </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">worker</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5288235649-16">[</span><span class="ss">ch3</span><span class="p" data-group-id="5288235649-16">]</span><span class="p" data-group-id="5288235649-13">}</span><span class="p" data-group-id="5288235649-12">]</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5288235649-17">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5288235649-18">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="5288235649-18">}</span><span class="p" data-group-id="5288235649-17">}</span><span class="p">.</span></code></pre><p>The <code class="inline">SupFlags</code> variable in the return value from <code class="inline">init/1</code> represents the
│ │ │ +                    </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3635053359-16">[</span><span class="ss">ch3</span><span class="p" data-group-id="3635053359-16">]</span><span class="p" data-group-id="3635053359-13">}</span><span class="p" data-group-id="3635053359-12">]</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3635053359-17">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3635053359-18">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="3635053359-18">}</span><span class="p" data-group-id="3635053359-17">}</span><span class="p">.</span></code></pre><p>The <code class="inline">SupFlags</code> variable in the return value from <code class="inline">init/1</code> represents the
│ │ │  <a href="sup_princ.html#flags">supervisor flags</a>.</p><p>The <code class="inline">ChildSpecs</code> variable in the return value from <code class="inline">init/1</code> is a list of
│ │ │  <a href="sup_princ.html#spec">child specifications</a>.</p><p><a href="" id="flags"></a></p><h2 id="supervisor-flags" class="section-heading">
│ │ │    <a href="#supervisor-flags" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Supervisor Flags</span>
│ │ │  </h2>
│ │ │ -<p>This is the type definition for the supervisor flags:</p><pre><code class="makeup erlang" translate="no"><span class="nf">sup_flags</span><span class="p" data-group-id="9738828548-1">(</span><span class="p" data-group-id="9738828548-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9738828548-2">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">strategy</span><span class="p" data-group-id="9738828548-3">(</span><span class="p" data-group-id="9738828548-3">)</span><span class="p">,</span><span class="w">           </span><span class="c1">% optional</span><span class="w">
│ │ │ -                </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="9738828548-4">(</span><span class="p" data-group-id="9738828548-4">)</span><span class="p">,</span><span class="w">   </span><span class="c1">% optional</span><span class="w">
│ │ │ -                </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="9738828548-5">(</span><span class="p" data-group-id="9738828548-5">)</span><span class="p">,</span><span class="w">          </span><span class="c1">% optional</span><span class="w">
│ │ │ -                </span><span class="ss">auto_shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">auto_shutdown</span><span class="p" data-group-id="9738828548-6">(</span><span class="p" data-group-id="9738828548-6">)</span><span class="p" data-group-id="9738828548-2">}</span><span class="w"> </span><span class="c1">% optional</span><span class="w">
│ │ │ -    </span><span class="nf">strategy</span><span class="p" data-group-id="9738828548-7">(</span><span class="p" data-group-id="9738828548-7">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">one_for_all</span><span class="w">
│ │ │ +<p>This is the type definition for the supervisor flags:</p><pre><code class="makeup erlang" translate="no"><span class="nf">sup_flags</span><span class="p" data-group-id="1178204008-1">(</span><span class="p" data-group-id="1178204008-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1178204008-2">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">strategy</span><span class="p" data-group-id="1178204008-3">(</span><span class="p" data-group-id="1178204008-3">)</span><span class="p">,</span><span class="w">           </span><span class="c1">% optional</span><span class="w">
│ │ │ +                </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="1178204008-4">(</span><span class="p" data-group-id="1178204008-4">)</span><span class="p">,</span><span class="w">   </span><span class="c1">% optional</span><span class="w">
│ │ │ +                </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="1178204008-5">(</span><span class="p" data-group-id="1178204008-5">)</span><span class="p">,</span><span class="w">          </span><span class="c1">% optional</span><span class="w">
│ │ │ +                </span><span class="ss">auto_shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">auto_shutdown</span><span class="p" data-group-id="1178204008-6">(</span><span class="p" data-group-id="1178204008-6">)</span><span class="p" data-group-id="1178204008-2">}</span><span class="w"> </span><span class="c1">% optional</span><span class="w">
│ │ │ +    </span><span class="nf">strategy</span><span class="p" data-group-id="1178204008-7">(</span><span class="p" data-group-id="1178204008-7">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">one_for_all</span><span class="w">
│ │ │                 </span><span class="p">|</span><span class="w"> </span><span class="ss">one_for_one</span><span class="w">
│ │ │                 </span><span class="p">|</span><span class="w"> </span><span class="ss">rest_for_one</span><span class="w">
│ │ │                 </span><span class="p">|</span><span class="w"> </span><span class="ss">simple_one_for_one</span><span class="w">
│ │ │ -    </span><span class="nf">auto_shutdown</span><span class="p" data-group-id="9738828548-8">(</span><span class="p" data-group-id="9738828548-8">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">never</span><span class="w">
│ │ │ +    </span><span class="nf">auto_shutdown</span><span class="p" data-group-id="1178204008-8">(</span><span class="p" data-group-id="1178204008-8">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">never</span><span class="w">
│ │ │                      </span><span class="p">|</span><span class="w"> </span><span class="ss">any_significant</span><span class="w">
│ │ │                      </span><span class="p">|</span><span class="w"> </span><span class="ss">all_significant</span></code></pre><ul><li><code class="inline">strategy</code> specifies the <a href="sup_princ.html#strategy">restart strategy</a>.</li><li><code class="inline">intensity</code> and <code class="inline">period</code> specify the
│ │ │  <a href="sup_princ.html#max_intensity">maximum restart intensity</a>.</li><li><code class="inline">auto_shutdown</code> specifies whether and when a supervisor should
│ │ │  <a href="sup_princ.html#automatic-shutdown">automatically shut itself down</a>.</li></ul><p><a href="" id="strategy"></a></p><h2 id="restart-strategy" class="section-heading">
│ │ │    <a href="#restart-strategy" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -408,28 +408,28 @@
│ │ │  exhaust the <a href="sup_princ.html#max_intensity">Maximum Restart Intensity</a> of the
│ │ │  parent supervisor.</p></section><p><a href="" id="spec"></a></p><h2 id="child-specification" class="section-heading">
│ │ │    <a href="#child-specification" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Child Specification</span>
│ │ │  </h2>
│ │ │ -<p>The type definition for a child specification is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">child_spec</span><span class="p" data-group-id="7010849194-1">(</span><span class="p" data-group-id="7010849194-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7010849194-2">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">child_id</span><span class="p" data-group-id="7010849194-3">(</span><span class="p" data-group-id="7010849194-3">)</span><span class="p">,</span><span class="w">             </span><span class="c1">% mandatory</span><span class="w">
│ │ │ -                 </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">mfargs</span><span class="p" data-group-id="7010849194-4">(</span><span class="p" data-group-id="7010849194-4">)</span><span class="p">,</span><span class="w">            </span><span class="c1">% mandatory</span><span class="w">
│ │ │ -                 </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">restart</span><span class="p" data-group-id="7010849194-5">(</span><span class="p" data-group-id="7010849194-5">)</span><span class="p">,</span><span class="w">         </span><span class="c1">% optional</span><span class="w">
│ │ │ -                 </span><span class="ss">significant</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">significant</span><span class="p" data-group-id="7010849194-6">(</span><span class="p" data-group-id="7010849194-6">)</span><span class="p">,</span><span class="w"> </span><span class="c1">% optional</span><span class="w">
│ │ │ -                 </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">shutdown</span><span class="p" data-group-id="7010849194-7">(</span><span class="p" data-group-id="7010849194-7">)</span><span class="p">,</span><span class="w">       </span><span class="c1">% optional</span><span class="w">
│ │ │ -                 </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">worker</span><span class="p" data-group-id="7010849194-8">(</span><span class="p" data-group-id="7010849194-8">)</span><span class="p">,</span><span class="w">             </span><span class="c1">% optional</span><span class="w">
│ │ │ -                 </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">modules</span><span class="p" data-group-id="7010849194-9">(</span><span class="p" data-group-id="7010849194-9">)</span><span class="p" data-group-id="7010849194-2">}</span><span class="w">         </span><span class="c1">% optional</span><span class="w">
│ │ │ -    </span><span class="nf">child_id</span><span class="p" data-group-id="7010849194-10">(</span><span class="p" data-group-id="7010849194-10">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="7010849194-11">(</span><span class="p" data-group-id="7010849194-11">)</span><span class="w">
│ │ │ -    </span><span class="nf">mfargs</span><span class="p" data-group-id="7010849194-12">(</span><span class="p" data-group-id="7010849194-12">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7010849194-13">{</span><span class="n">M</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">module</span><span class="p" data-group-id="7010849194-14">(</span><span class="p" data-group-id="7010849194-14">)</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="7010849194-15">(</span><span class="p" data-group-id="7010849194-15">)</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="7010849194-16">[</span><span class="nf">term</span><span class="p" data-group-id="7010849194-17">(</span><span class="p" data-group-id="7010849194-17">)</span><span class="p" data-group-id="7010849194-16">]</span><span class="p" data-group-id="7010849194-13">}</span><span class="w">
│ │ │ -    </span><span class="nf">modules</span><span class="p" data-group-id="7010849194-18">(</span><span class="p" data-group-id="7010849194-18">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7010849194-19">[</span><span class="nf">module</span><span class="p" data-group-id="7010849194-20">(</span><span class="p" data-group-id="7010849194-20">)</span><span class="p" data-group-id="7010849194-19">]</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">dynamic</span><span class="w">
│ │ │ -    </span><span class="nf">restart</span><span class="p" data-group-id="7010849194-21">(</span><span class="p" data-group-id="7010849194-21">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">permanent</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">transient</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">temporary</span><span class="w">
│ │ │ -    </span><span class="nf">significant</span><span class="p" data-group-id="7010849194-22">(</span><span class="p" data-group-id="7010849194-22">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">boolean</span><span class="p" data-group-id="7010849194-23">(</span><span class="p" data-group-id="7010849194-23">)</span><span class="w">
│ │ │ -    </span><span class="nf">shutdown</span><span class="p" data-group-id="7010849194-24">(</span><span class="p" data-group-id="7010849194-24">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">timeout</span><span class="p" data-group-id="7010849194-25">(</span><span class="p" data-group-id="7010849194-25">)</span><span class="w">
│ │ │ -    </span><span class="nf">worker</span><span class="p" data-group-id="7010849194-26">(</span><span class="p" data-group-id="7010849194-26">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">worker</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">supervisor</span></code></pre><ul><li><p><code class="inline">id</code> is used to identify the child specification internally by the supervisor.</p><p>The <code class="inline">id</code> key is mandatory.</p><p>Note that this identifier occasionally has been called &quot;name&quot;. As far as
│ │ │ +<p>The type definition for a child specification is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">child_spec</span><span class="p" data-group-id="7758362413-1">(</span><span class="p" data-group-id="7758362413-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7758362413-2">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">child_id</span><span class="p" data-group-id="7758362413-3">(</span><span class="p" data-group-id="7758362413-3">)</span><span class="p">,</span><span class="w">             </span><span class="c1">% mandatory</span><span class="w">
│ │ │ +                 </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">mfargs</span><span class="p" data-group-id="7758362413-4">(</span><span class="p" data-group-id="7758362413-4">)</span><span class="p">,</span><span class="w">            </span><span class="c1">% mandatory</span><span class="w">
│ │ │ +                 </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">restart</span><span class="p" data-group-id="7758362413-5">(</span><span class="p" data-group-id="7758362413-5">)</span><span class="p">,</span><span class="w">         </span><span class="c1">% optional</span><span class="w">
│ │ │ +                 </span><span class="ss">significant</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">significant</span><span class="p" data-group-id="7758362413-6">(</span><span class="p" data-group-id="7758362413-6">)</span><span class="p">,</span><span class="w"> </span><span class="c1">% optional</span><span class="w">
│ │ │ +                 </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">shutdown</span><span class="p" data-group-id="7758362413-7">(</span><span class="p" data-group-id="7758362413-7">)</span><span class="p">,</span><span class="w">       </span><span class="c1">% optional</span><span class="w">
│ │ │ +                 </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">worker</span><span class="p" data-group-id="7758362413-8">(</span><span class="p" data-group-id="7758362413-8">)</span><span class="p">,</span><span class="w">             </span><span class="c1">% optional</span><span class="w">
│ │ │ +                 </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">modules</span><span class="p" data-group-id="7758362413-9">(</span><span class="p" data-group-id="7758362413-9">)</span><span class="p" data-group-id="7758362413-2">}</span><span class="w">         </span><span class="c1">% optional</span><span class="w">
│ │ │ +    </span><span class="nf">child_id</span><span class="p" data-group-id="7758362413-10">(</span><span class="p" data-group-id="7758362413-10">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="7758362413-11">(</span><span class="p" data-group-id="7758362413-11">)</span><span class="w">
│ │ │ +    </span><span class="nf">mfargs</span><span class="p" data-group-id="7758362413-12">(</span><span class="p" data-group-id="7758362413-12">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7758362413-13">{</span><span class="n">M</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">module</span><span class="p" data-group-id="7758362413-14">(</span><span class="p" data-group-id="7758362413-14">)</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="7758362413-15">(</span><span class="p" data-group-id="7758362413-15">)</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="7758362413-16">[</span><span class="nf">term</span><span class="p" data-group-id="7758362413-17">(</span><span class="p" data-group-id="7758362413-17">)</span><span class="p" data-group-id="7758362413-16">]</span><span class="p" data-group-id="7758362413-13">}</span><span class="w">
│ │ │ +    </span><span class="nf">modules</span><span class="p" data-group-id="7758362413-18">(</span><span class="p" data-group-id="7758362413-18">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7758362413-19">[</span><span class="nf">module</span><span class="p" data-group-id="7758362413-20">(</span><span class="p" data-group-id="7758362413-20">)</span><span class="p" data-group-id="7758362413-19">]</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">dynamic</span><span class="w">
│ │ │ +    </span><span class="nf">restart</span><span class="p" data-group-id="7758362413-21">(</span><span class="p" data-group-id="7758362413-21">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">permanent</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">transient</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">temporary</span><span class="w">
│ │ │ +    </span><span class="nf">significant</span><span class="p" data-group-id="7758362413-22">(</span><span class="p" data-group-id="7758362413-22">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">boolean</span><span class="p" data-group-id="7758362413-23">(</span><span class="p" data-group-id="7758362413-23">)</span><span class="w">
│ │ │ +    </span><span class="nf">shutdown</span><span class="p" data-group-id="7758362413-24">(</span><span class="p" data-group-id="7758362413-24">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">timeout</span><span class="p" data-group-id="7758362413-25">(</span><span class="p" data-group-id="7758362413-25">)</span><span class="w">
│ │ │ +    </span><span class="nf">worker</span><span class="p" data-group-id="7758362413-26">(</span><span class="p" data-group-id="7758362413-26">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">worker</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">supervisor</span></code></pre><ul><li><p><code class="inline">id</code> is used to identify the child specification internally by the supervisor.</p><p>The <code class="inline">id</code> key is mandatory.</p><p>Note that this identifier occasionally has been called &quot;name&quot;. As far as
│ │ │  possible, the terms &quot;identifier&quot; or &quot;id&quot; are now used but in order to keep
│ │ │  backwards compatibility, some occurrences of &quot;name&quot; can still be found, for
│ │ │  example in error messages.</p></li><li><p><code class="inline">start</code> defines the function call used to start the child process. It is a
│ │ │  module-function-arguments tuple used as <a href="../../erts-17.0/doc/html/erlang.html#apply/3"><code class="inline">apply(M, F, A)</code></a>.</p><p>It is to be (or result in) a call to any of the following:</p><ul><li><a href="../../lib/stdlib-8.0/doc/html/supervisor.html#start_link/3"><code class="inline">supervisor:start_link/2,3</code></a></li><li><a href="../../lib/stdlib-8.0/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/3,4</code></a></li><li><a href="../../lib/stdlib-8.0/doc/html/gen_statem.html#start_link/4"><code class="inline">gen_statem:start_link/3,4</code></a></li><li><a href="../../lib/stdlib-8.0/doc/html/gen_event.html#start_link/2"><code class="inline">gen_event:start_link/0,1,2</code></a></li><li>A function compliant with these functions. For details, see
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/supervisor.html"><code class="inline">supervisor</code></a>.</li></ul><p>The <code class="inline">start</code> key is mandatory.</p></li><li><p><a href="" id="restart"></a> <code class="inline">restart</code> defines when a terminated child process is to be
│ │ │  restarted.</p><ul><li>A <code class="inline">permanent</code> child process is always restarted.</li><li>A <code class="inline">temporary</code> child process is never restarted (not even when the supervisor
│ │ │  restart strategy is <code class="inline">rest_for_one</code> or <code class="inline">one_for_all</code> and a sibling death
│ │ │ @@ -457,53 +457,53 @@
│ │ │  <code class="inline">supervisor</code>, the default value <code class="inline">infinity</code> will be used.</p></li><li><p><code class="inline">type</code> specifies whether the child process is a supervisor or a worker.</p><p>The <code class="inline">type</code> key is optional. If it is not given, the default value <code class="inline">worker</code>
│ │ │  will be used.</p></li><li><p><code class="inline">modules</code> has to be a list consisting of a single element. The value
│ │ │  of that element depends on the behaviour of the process:</p><ul><li>If the child process is a <code class="inline">gen_event</code>, the element has to be the atom
│ │ │  <code class="inline">dynamic</code>.</li><li>Otherwise, the element should be <code class="inline">Module</code>, where <code class="inline">Module</code> is the
│ │ │  name of the callback module.</li></ul><p>This information is used by the release handler during upgrades and
│ │ │  downgrades; see <a href="release_handling.html">Release Handling</a>.</p><p>The <code class="inline">modules</code> key is optional. If it is not given, it defaults to <code class="inline">[M]</code>, where
│ │ │  <code class="inline">M</code> comes from the child's start <code class="inline">{M,F,A}</code>.</p></li></ul><p><em>Example:</em> The child specification to start the server <code class="inline">ch3</code> in the previous
│ │ │ -example looks as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3710880335-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3710880335-2">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3710880335-3">[</span><span class="p" data-group-id="3710880335-3">]</span><span class="p" data-group-id="3710880335-2">}</span><span class="p">,</span><span class="w">
│ │ │ +example looks as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4136341675-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4136341675-2">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4136341675-3">[</span><span class="p" data-group-id="4136341675-3">]</span><span class="p" data-group-id="4136341675-2">}</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">permanent</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">worker</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3710880335-4">[</span><span class="ss">ch3</span><span class="p" data-group-id="3710880335-4">]</span><span class="p" data-group-id="3710880335-1">}</span></code></pre><p>or simplified, relying on the default values:</p><pre><code class="text">#{id =&gt; ch3,
│ │ │ +  </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4136341675-4">[</span><span class="ss">ch3</span><span class="p" data-group-id="4136341675-4">]</span><span class="p" data-group-id="4136341675-1">}</span></code></pre><p>or simplified, relying on the default values:</p><pre><code class="text">#{id =&gt; ch3,
│ │ │    start =&gt; {ch3, start_link, []},
│ │ │    shutdown =&gt; brutal_kill}</code></pre><p>Example: A child specification to start the event manager from the chapter about
│ │ │ -<a href="events.html#mgr">gen_event</a>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1304709756-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">error_man</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1304709756-2">{</span><span class="ss">gen_event</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1304709756-3">[</span><span class="p" data-group-id="1304709756-4">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">error_man</span><span class="p" data-group-id="1304709756-4">}</span><span class="p" data-group-id="1304709756-3">]</span><span class="p" data-group-id="1304709756-2">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">dynamic</span><span class="p" data-group-id="1304709756-1">}</span></code></pre><p>Both server and event manager are registered processes which can be expected to
│ │ │ +<a href="events.html#mgr">gen_event</a>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1200650490-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">error_man</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1200650490-2">{</span><span class="ss">gen_event</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1200650490-3">[</span><span class="p" data-group-id="1200650490-4">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">error_man</span><span class="p" data-group-id="1200650490-4">}</span><span class="p" data-group-id="1200650490-3">]</span><span class="p" data-group-id="1200650490-2">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">dynamic</span><span class="p" data-group-id="1200650490-1">}</span></code></pre><p>Both server and event manager are registered processes which can be expected to
│ │ │  be always accessible. Thus they are specified to be <code class="inline">permanent</code>.</p><p><code class="inline">ch3</code> does not need to do any cleaning up before termination. Thus, no shutdown
│ │ │  time is needed, but <code class="inline">brutal_kill</code> is sufficient. <code class="inline">error_man</code> can need some time
│ │ │  for the event handlers to clean up, thus the shutdown time is set to 5000 ms
│ │ │ -(which is the default value).</p><p>Example: A child specification to start another supervisor:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7718593875-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">sup</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7718593875-2">{</span><span class="ss">sup</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7718593875-3">[</span><span class="p" data-group-id="7718593875-3">]</span><span class="p" data-group-id="7718593875-2">}</span><span class="p">,</span><span class="w">
│ │ │ +(which is the default value).</p><p>Example: A child specification to start another supervisor:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5972566509-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">sup</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5972566509-2">{</span><span class="ss">sup</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5972566509-3">[</span><span class="p" data-group-id="5972566509-3">]</span><span class="p" data-group-id="5972566509-2">}</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">transient</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="7718593875-1">}</span><span class="w"> </span><span class="c1">% will cause default shutdown=&gt;infinity</span></code></pre><p><a href="" id="super_tree"></a></p><h2 id="starting-a-supervisor" class="section-heading">
│ │ │ +  </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="5972566509-1">}</span><span class="w"> </span><span class="c1">% will cause default shutdown=&gt;infinity</span></code></pre><p><a href="" id="super_tree"></a></p><h2 id="starting-a-supervisor" class="section-heading">
│ │ │    <a href="#starting-a-supervisor" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Starting a Supervisor</span>
│ │ │  </h2>
│ │ │  <p>In the previous example, the supervisor is started by calling
│ │ │ -<code class="inline">ch_sup:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="9029775249-1">(</span><span class="p" data-group-id="9029775249-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="9029775249-2">(</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9029775249-3">[</span><span class="p" data-group-id="9029775249-3">]</span><span class="p" data-group-id="9029775249-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch_sup:start_link</code> calls function <a href="../../lib/stdlib-8.0/doc/html/supervisor.html#start_link/2"><code class="inline">supervisor:start_link/2</code></a>, which spawns and
│ │ │ +<code class="inline">ch_sup:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="7827239480-1">(</span><span class="p" data-group-id="7827239480-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="7827239480-2">(</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7827239480-3">[</span><span class="p" data-group-id="7827239480-3">]</span><span class="p" data-group-id="7827239480-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch_sup:start_link</code> calls function <a href="../../lib/stdlib-8.0/doc/html/supervisor.html#start_link/2"><code class="inline">supervisor:start_link/2</code></a>, which spawns and
│ │ │  links to a new process, a supervisor.</p><ul><li>The first argument, <code class="inline">ch_sup</code>, is the name of the callback module, that is, the
│ │ │  module where the <code class="inline">init</code> callback function is located.</li><li>The second argument, <code class="inline">[]</code>, is a term that is passed as is to the callback
│ │ │  function <code class="inline">init</code>. Here, <code class="inline">init</code> does not need any data and ignores the argument.</li></ul><p>In this case, the supervisor is not registered. Instead its pid must be used. A
│ │ │  name can be specified by calling
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/supervisor.html#start_link/3"><code class="inline">supervisor:start_link({local, Name}, Module, Args)</code></a>
│ │ │  or
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/supervisor.html#start_link/3"><code class="inline">supervisor:start_link({global, Name}, Module, Args)</code></a>.</p><p>The new supervisor process calls the callback function <code class="inline">ch_sup:init([])</code>. <code class="inline">init</code>
│ │ │ -has to return <code class="inline">{ok, {SupFlags, ChildSpecs}}</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="7549095482-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="7549095482-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7549095482-2">#{</span><span class="p" data-group-id="7549095482-2">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7549095482-3">[</span><span class="p" data-group-id="7549095482-4">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7549095482-5">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7549095482-6">[</span><span class="p" data-group-id="7549095482-6">]</span><span class="p" data-group-id="7549095482-5">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p" data-group-id="7549095482-4">}</span><span class="p" data-group-id="7549095482-3">]</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7549095482-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7549095482-8">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="7549095482-8">}</span><span class="p" data-group-id="7549095482-7">}</span><span class="p">.</span></code></pre><p>Subsequently, the supervisor starts its child processes according to the child
│ │ │ +has to return <code class="inline">{ok, {SupFlags, ChildSpecs}}</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="4003971716-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="4003971716-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4003971716-2">#{</span><span class="p" data-group-id="4003971716-2">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4003971716-3">[</span><span class="p" data-group-id="4003971716-4">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4003971716-5">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4003971716-6">[</span><span class="p" data-group-id="4003971716-6">]</span><span class="p" data-group-id="4003971716-5">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p" data-group-id="4003971716-4">}</span><span class="p" data-group-id="4003971716-3">]</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4003971716-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4003971716-8">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="4003971716-8">}</span><span class="p" data-group-id="4003971716-7">}</span><span class="p">.</span></code></pre><p>Subsequently, the supervisor starts its child processes according to the child
│ │ │  specifications in the start specification. In this case there is a single child
│ │ │  process, called <code class="inline">ch3</code>.</p><p><a href="../../lib/stdlib-8.0/doc/html/supervisor.html#start_link/3"><code class="inline">supervisor:start_link/3</code></a> is synchronous. It does not return until all child
│ │ │  processes have been started.</p><h2 id="adding-a-child-process" class="section-heading">
│ │ │    <a href="#adding-a-child-process" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Adding a Child Process</span>
│ │ │ @@ -532,31 +532,31 @@
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Simplified one_for_one Supervisors</span>
│ │ │  </h2>
│ │ │  <p>A supervisor with restart strategy <code class="inline">simple_one_for_one</code> is a simplified
│ │ │  <code class="inline">one_for_one</code> supervisor, where all child processes are dynamically added
│ │ │  instances of the same process.</p><p>The following is an example of a callback module for a <code class="inline">simple_one_for_one</code>
│ │ │ -supervisor:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6528712565-1">(</span><span class="ss">simple_sup</span><span class="p" data-group-id="6528712565-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="6528712565-2">(</span><span class="ss">supervisor</span><span class="p" data-group-id="6528712565-2">)</span><span class="p">.</span><span class="w">
│ │ │ +supervisor:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3178175493-1">(</span><span class="ss">simple_sup</span><span class="p" data-group-id="3178175493-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="3178175493-2">(</span><span class="ss">supervisor</span><span class="p" data-group-id="3178175493-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6528712565-3">(</span><span class="p" data-group-id="6528712565-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6528712565-4">]</span><span class="p" data-group-id="6528712565-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6528712565-5">(</span><span class="p" data-group-id="6528712565-6">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6528712565-6">]</span><span class="p" data-group-id="6528712565-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3178175493-3">(</span><span class="p" data-group-id="3178175493-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3178175493-4">]</span><span class="p" data-group-id="3178175493-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3178175493-5">(</span><span class="p" data-group-id="3178175493-6">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3178175493-6">]</span><span class="p" data-group-id="3178175493-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="6528712565-7">(</span><span class="p" data-group-id="6528712565-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="6528712565-8">(</span><span class="ss">simple_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6528712565-9">[</span><span class="p" data-group-id="6528712565-9">]</span><span class="p" data-group-id="6528712565-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="3178175493-7">(</span><span class="p" data-group-id="3178175493-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="3178175493-8">(</span><span class="ss">simple_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3178175493-9">[</span><span class="p" data-group-id="3178175493-9">]</span><span class="p" data-group-id="3178175493-8">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="6528712565-10">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="6528712565-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6528712565-11">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">simple_one_for_one</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="3178175493-10">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="3178175493-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3178175493-11">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">simple_one_for_one</span><span class="p">,</span><span class="w">
│ │ │                   </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="6528712565-11">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6528712565-12">[</span><span class="p" data-group-id="6528712565-13">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">call</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6528712565-14">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6528712565-15">[</span><span class="p" data-group-id="6528712565-15">]</span><span class="p" data-group-id="6528712565-14">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p" data-group-id="6528712565-13">}</span><span class="p" data-group-id="6528712565-12">]</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6528712565-16">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6528712565-17">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="6528712565-17">}</span><span class="p" data-group-id="6528712565-16">}</span><span class="p">.</span></code></pre><p>When started, the supervisor does not start any child
│ │ │ +                 </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="3178175493-11">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3178175493-12">[</span><span class="p" data-group-id="3178175493-13">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">call</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3178175493-14">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3178175493-15">[</span><span class="p" data-group-id="3178175493-15">]</span><span class="p" data-group-id="3178175493-14">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p" data-group-id="3178175493-13">}</span><span class="p" data-group-id="3178175493-12">]</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3178175493-16">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3178175493-17">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="3178175493-17">}</span><span class="p" data-group-id="3178175493-16">}</span><span class="p">.</span></code></pre><p>When started, the supervisor does not start any child
│ │ │  processes. Instead, all child processes need to be added dynamically by
│ │ │  calling <a href="../../lib/stdlib-8.0/doc/html/supervisor.html#start_child/2"><code class="inline">supervisor:start_child(Sup, List)</code></a>.</p><p><code class="inline">Sup</code> is the pid, or name, of the supervisor. <code class="inline">List</code> is an arbitrary list of
│ │ │  terms, which are added to the list of arguments specified in the child
│ │ │  specification. If the start function is specified as <code class="inline">{M, F, A}</code>, the child
│ │ │  process is started by calling <a href="../../erts-17.0/doc/html/erlang.html#apply/3"><code class="inline">apply(M, F, A++List)</code></a>.</p><p>For example, adding a child to <code class="inline">simple_sup</code> above:</p><pre><code class="text">supervisor:start_child(Pid, [id1])</code></pre><p>The result is that the child process is started by calling
│ │ │  <a href="../../erts-17.0/doc/html/erlang.html#apply/3"><code class="inline">apply(call, start_link, []++[id1])</code></a>, or actually:</p><pre><code class="text">call:start_link(id1)</code></pre><p>A child under a <code class="inline">simple_one_for_one</code> supervisor can be terminated with the
│ │ │  following:</p><pre><code class="text">supervisor:terminate_child(Sup, Pid)</code></pre><p><code class="inline">Sup</code> is the pid, or name, of the supervisor and <code class="inline">Pid</code> is the pid of the child.</p><p>Because a <code class="inline">simple_one_for_one</code> supervisor can have many children, it shuts them
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/tablesdatabases.html
│ │ │ @@ -146,73 +146,73 @@
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Deleting an Element</span>
│ │ │  </h3>
│ │ │  <p>The <code class="inline">delete</code> operation is considered successful if the element was not present
│ │ │  in the table. Hence all attempts to check that the element is present in the
│ │ │  Ets/Mnesia table before deletion are unnecessary. Here follows an example for
│ │ │ -Ets tables:</p><p><strong>DO</strong></p><pre><code class="text">ets:delete(Tab, Key),</code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="8220271490-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="8220271490-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8220271490-2">[</span><span class="p" data-group-id="8220271490-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +Ets tables:</p><p><strong>DO</strong></p><pre><code class="text">ets:delete(Tab, Key),</code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="8230073230-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="8230073230-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8230073230-2">[</span><span class="p" data-group-id="8230073230-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8220271490-3">[</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="8220271490-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nc">ets</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="8220271490-4">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="8220271490-4">)</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8230073230-3">[</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="8230073230-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nc">ets</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="8230073230-4">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="8230073230-4">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">,</span></code></pre><h3 id="fetching-data" class="section-heading">
│ │ │    <a href="#fetching-data" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Fetching Data</span>
│ │ │  </h3>
│ │ │  <p>Do not fetch data that you already have.</p><p>Consider that you have a module that handles the abstract data type <code class="inline">Person</code>.
│ │ │  You export the interface function <code class="inline">print_person/1</code>, which uses the internal
│ │ │  functions <code class="inline">print_name/1</code>, <code class="inline">print_age/1</code>, and <code class="inline">print_occupation/1</code>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>If the function <code class="inline">print_name/1</code>, and so on, had been interface functions, the
│ │ │  situation would have been different, as you do not want the user of the
│ │ │  interface to know about the internal data representation.</p></section><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="c1">%%% Interface function</span><span class="w">
│ │ │ -</span><span class="nf">print_person</span><span class="p" data-group-id="7866852447-1">(</span><span class="n">PersonId</span><span class="p" data-group-id="7866852447-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">print_person</span><span class="p" data-group-id="2641487726-1">(</span><span class="n">PersonId</span><span class="p" data-group-id="2641487726-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Look up the person in the named table person,</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="7866852447-2">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="7866852447-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="7866852447-3">[</span><span class="n">Person</span><span class="p" data-group-id="7866852447-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">print_name</span><span class="p" data-group-id="7866852447-4">(</span><span class="n">Person</span><span class="p" data-group-id="7866852447-4">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">print_age</span><span class="p" data-group-id="7866852447-5">(</span><span class="n">Person</span><span class="p" data-group-id="7866852447-5">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">print_occupation</span><span class="p" data-group-id="7866852447-6">(</span><span class="n">Person</span><span class="p" data-group-id="7866852447-6">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="7866852447-7">[</span><span class="p" data-group-id="7866852447-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7866852447-8">(</span><span class="s">&quot;No person with ID = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7866852447-9">[</span><span class="n">PersonId</span><span class="p" data-group-id="7866852447-9">]</span><span class="p" data-group-id="7866852447-8">)</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="2641487726-2">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="2641487726-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2641487726-3">[</span><span class="n">Person</span><span class="p" data-group-id="2641487726-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">print_name</span><span class="p" data-group-id="2641487726-4">(</span><span class="n">Person</span><span class="p" data-group-id="2641487726-4">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">print_age</span><span class="p" data-group-id="2641487726-5">(</span><span class="n">Person</span><span class="p" data-group-id="2641487726-5">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">print_occupation</span><span class="p" data-group-id="2641487726-6">(</span><span class="n">Person</span><span class="p" data-group-id="2641487726-6">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2641487726-7">[</span><span class="p" data-group-id="2641487726-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2641487726-8">(</span><span class="s">&quot;No person with ID = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2641487726-9">[</span><span class="n">PersonId</span><span class="p" data-group-id="2641487726-9">]</span><span class="p" data-group-id="2641487726-8">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Internal functions</span><span class="w">
│ │ │ -</span><span class="nf">print_name</span><span class="p" data-group-id="7866852447-10">(</span><span class="n">Person</span><span class="p" data-group-id="7866852447-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7866852447-11">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7866852447-12">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="7866852447-12">]</span><span class="p" data-group-id="7866852447-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">print_name</span><span class="p" data-group-id="2641487726-10">(</span><span class="n">Person</span><span class="p" data-group-id="2641487726-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2641487726-11">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2641487726-12">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="2641487726-12">]</span><span class="p" data-group-id="2641487726-11">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">print_age</span><span class="p" data-group-id="7866852447-13">(</span><span class="n">Person</span><span class="p" data-group-id="7866852447-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7866852447-14">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7866852447-15">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="7866852447-15">]</span><span class="p" data-group-id="7866852447-14">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">print_age</span><span class="p" data-group-id="2641487726-13">(</span><span class="n">Person</span><span class="p" data-group-id="2641487726-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2641487726-14">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2641487726-15">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="2641487726-15">]</span><span class="p" data-group-id="2641487726-14">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">print_occupation</span><span class="p" data-group-id="7866852447-16">(</span><span class="n">Person</span><span class="p" data-group-id="7866852447-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7866852447-17">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7866852447-18">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">occupation</span><span class="p" data-group-id="7866852447-18">]</span><span class="p" data-group-id="7866852447-17">)</span><span class="p">.</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="c1">%%% Interface function</span><span class="w">
│ │ │ -</span><span class="nf">print_person</span><span class="p" data-group-id="3033640665-1">(</span><span class="n">PersonId</span><span class="p" data-group-id="3033640665-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">print_occupation</span><span class="p" data-group-id="2641487726-16">(</span><span class="n">Person</span><span class="p" data-group-id="2641487726-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2641487726-17">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2641487726-18">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">occupation</span><span class="p" data-group-id="2641487726-18">]</span><span class="p" data-group-id="2641487726-17">)</span><span class="p">.</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="c1">%%% Interface function</span><span class="w">
│ │ │ +</span><span class="nf">print_person</span><span class="p" data-group-id="5627318283-1">(</span><span class="n">PersonId</span><span class="p" data-group-id="5627318283-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Look up the person in the named table person,</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="3033640665-2">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="3033640665-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3033640665-3">[</span><span class="n">Person</span><span class="p" data-group-id="3033640665-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">print_name</span><span class="p" data-group-id="3033640665-4">(</span><span class="n">PersonId</span><span class="p" data-group-id="3033640665-4">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">print_age</span><span class="p" data-group-id="3033640665-5">(</span><span class="n">PersonId</span><span class="p" data-group-id="3033640665-5">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">print_occupation</span><span class="p" data-group-id="3033640665-6">(</span><span class="n">PersonId</span><span class="p" data-group-id="3033640665-6">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3033640665-7">[</span><span class="p" data-group-id="3033640665-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3033640665-8">(</span><span class="s">&quot;No person with ID = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3033640665-9">[</span><span class="n">PersonId</span><span class="p" data-group-id="3033640665-9">]</span><span class="p" data-group-id="3033640665-8">)</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="5627318283-2">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="5627318283-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="5627318283-3">[</span><span class="n">Person</span><span class="p" data-group-id="5627318283-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">print_name</span><span class="p" data-group-id="5627318283-4">(</span><span class="n">PersonId</span><span class="p" data-group-id="5627318283-4">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">print_age</span><span class="p" data-group-id="5627318283-5">(</span><span class="n">PersonId</span><span class="p" data-group-id="5627318283-5">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">print_occupation</span><span class="p" data-group-id="5627318283-6">(</span><span class="n">PersonId</span><span class="p" data-group-id="5627318283-6">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="5627318283-7">[</span><span class="p" data-group-id="5627318283-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5627318283-8">(</span><span class="s">&quot;No person with ID = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5627318283-9">[</span><span class="n">PersonId</span><span class="p" data-group-id="5627318283-9">]</span><span class="p" data-group-id="5627318283-8">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Internal functions</span><span class="w">
│ │ │ -</span><span class="nf">print_name</span><span class="p" data-group-id="3033640665-10">(</span><span class="n">PersonId</span><span class="p" data-group-id="3033640665-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3033640665-11">[</span><span class="n">Person</span><span class="p" data-group-id="3033640665-11">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="3033640665-12">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="3033640665-12">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3033640665-13">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3033640665-14">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="3033640665-14">]</span><span class="p" data-group-id="3033640665-13">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">print_age</span><span class="p" data-group-id="3033640665-15">(</span><span class="n">PersonId</span><span class="p" data-group-id="3033640665-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3033640665-16">[</span><span class="n">Person</span><span class="p" data-group-id="3033640665-16">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="3033640665-17">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="3033640665-17">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3033640665-18">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3033640665-19">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="3033640665-19">]</span><span class="p" data-group-id="3033640665-18">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">print_occupation</span><span class="p" data-group-id="3033640665-20">(</span><span class="n">PersonId</span><span class="p" data-group-id="3033640665-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3033640665-21">[</span><span class="n">Person</span><span class="p" data-group-id="3033640665-21">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="3033640665-22">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="3033640665-22">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3033640665-23">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3033640665-24">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">occupation</span><span class="p" data-group-id="3033640665-24">]</span><span class="p" data-group-id="3033640665-23">)</span><span class="p">.</span></code></pre><h3 id="non-persistent-database-storage" class="section-heading">
│ │ │ +</span><span class="nf">print_name</span><span class="p" data-group-id="5627318283-10">(</span><span class="n">PersonId</span><span class="p" data-group-id="5627318283-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5627318283-11">[</span><span class="n">Person</span><span class="p" data-group-id="5627318283-11">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="5627318283-12">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="5627318283-12">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5627318283-13">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5627318283-14">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="5627318283-14">]</span><span class="p" data-group-id="5627318283-13">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">print_age</span><span class="p" data-group-id="5627318283-15">(</span><span class="n">PersonId</span><span class="p" data-group-id="5627318283-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5627318283-16">[</span><span class="n">Person</span><span class="p" data-group-id="5627318283-16">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="5627318283-17">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="5627318283-17">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5627318283-18">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5627318283-19">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="5627318283-19">]</span><span class="p" data-group-id="5627318283-18">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">print_occupation</span><span class="p" data-group-id="5627318283-20">(</span><span class="n">PersonId</span><span class="p" data-group-id="5627318283-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5627318283-21">[</span><span class="n">Person</span><span class="p" data-group-id="5627318283-21">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="5627318283-22">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="5627318283-22">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5627318283-23">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5627318283-24">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">occupation</span><span class="p" data-group-id="5627318283-24">]</span><span class="p" data-group-id="5627318283-23">)</span><span class="p">.</span></code></pre><h3 id="non-persistent-database-storage" class="section-heading">
│ │ │    <a href="#non-persistent-database-storage" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Non-Persistent Database Storage</span>
│ │ │  </h3>
│ │ │  <p>For non-persistent database storage, prefer Ets tables over Mnesia
│ │ │  <code class="inline">local_content</code> tables. Even the Mnesia <code class="inline">dirty_write</code> operations carry a fixed
│ │ │ @@ -226,38 +226,38 @@
│ │ │  </h3>
│ │ │  <p>Assuming an Ets table that uses <code class="inline">idno</code> as key and contains the following:</p><pre><code class="text">[#person{idno = 1, name = &quot;Adam&quot;,  age = 31, occupation = &quot;mailman&quot;},
│ │ │   #person{idno = 2, name = &quot;Bryan&quot;, age = 31, occupation = &quot;cashier&quot;},
│ │ │   #person{idno = 3, name = &quot;Bryan&quot;, age = 35, occupation = &quot;banker&quot;},
│ │ │   #person{idno = 4, name = &quot;Carl&quot;,  age = 25, occupation = &quot;mailman&quot;}]</code></pre><p>If you <em>must</em> return all data stored in the Ets table, you can use
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/ets.html#tab2list/1"><code class="inline">ets:tab2list/1</code></a>. However, usually you are only interested in a subset of the
│ │ │  information in which case <a href="../../lib/stdlib-8.0/doc/html/ets.html#tab2list/1"><code class="inline">ets:tab2list/1</code></a> is expensive. If you only want to
│ │ │ -extract one field from each record, for example, the age of every person, then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="1138781512-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1138781512-2">[</span><span class="p" data-group-id="1138781512-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1138781512-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ +extract one field from each record, for example, the age of every person, then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="4773012972-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4773012972-2">[</span><span class="p" data-group-id="4773012972-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="4773012972-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │                            </span><span class="ss">name</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │                            </span><span class="ss">age</span><span class="o">=</span><span class="ss">&#39;$1&#39;</span><span class="p">,</span><span class="w">
│ │ │ -                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="1138781512-4">}</span><span class="p">,</span><span class="w">
│ │ │ -                </span><span class="p" data-group-id="1138781512-5">[</span><span class="p" data-group-id="1138781512-5">]</span><span class="p">,</span><span class="w">
│ │ │ -                </span><span class="p" data-group-id="1138781512-6">[</span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="1138781512-6">]</span><span class="p" data-group-id="1138781512-3">}</span><span class="p" data-group-id="1138781512-2">]</span><span class="p" data-group-id="1138781512-1">)</span><span class="p">,</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="0954826585-1">(</span><span class="n">Tab</span><span class="p" data-group-id="0954826585-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="0954826585-2">(</span><span class="nf">fun</span><span class="p" data-group-id="0954826585-3">(</span><span class="n">X</span><span class="p" data-group-id="0954826585-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="0954826585-2">)</span><span class="p">,</span></code></pre><p>If you are only interested in the age of all persons named &quot;Bryan&quot;, then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="1269621371-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1269621371-2">[</span><span class="p" data-group-id="1269621371-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1269621371-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ +                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="4773012972-4">}</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="p" data-group-id="4773012972-5">[</span><span class="p" data-group-id="4773012972-5">]</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="p" data-group-id="4773012972-6">[</span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="4773012972-6">]</span><span class="p" data-group-id="4773012972-3">}</span><span class="p" data-group-id="4773012972-2">]</span><span class="p" data-group-id="4773012972-1">)</span><span class="p">,</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="1830578455-1">(</span><span class="n">Tab</span><span class="p" data-group-id="1830578455-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="1830578455-2">(</span><span class="nf">fun</span><span class="p" data-group-id="1830578455-3">(</span><span class="n">X</span><span class="p" data-group-id="1830578455-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="1830578455-2">)</span><span class="p">,</span></code></pre><p>If you are only interested in the age of all persons named &quot;Bryan&quot;, then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="1667451416-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1667451416-2">[</span><span class="p" data-group-id="1667451416-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1667451416-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │                            </span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Bryan&quot;</span><span class="p">,</span><span class="w">
│ │ │                            </span><span class="ss">age</span><span class="o">=</span><span class="ss">&#39;$1&#39;</span><span class="p">,</span><span class="w">
│ │ │ -                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="1269621371-4">}</span><span class="p">,</span><span class="w">
│ │ │ -                </span><span class="p" data-group-id="1269621371-5">[</span><span class="p" data-group-id="1269621371-5">]</span><span class="p">,</span><span class="w">
│ │ │ -                </span><span class="p" data-group-id="1269621371-6">[</span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="1269621371-6">]</span><span class="p" data-group-id="1269621371-3">}</span><span class="p" data-group-id="1269621371-2">]</span><span class="p" data-group-id="1269621371-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="1373350218-1">(</span><span class="n">Tab</span><span class="p" data-group-id="1373350218-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="1373350218-2">(</span><span class="nf">fun</span><span class="p" data-group-id="1373350218-3">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="1373350218-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="1667451416-4">}</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="p" data-group-id="1667451416-5">[</span><span class="p" data-group-id="1667451416-5">]</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="p" data-group-id="1667451416-6">[</span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="1667451416-6">]</span><span class="p" data-group-id="1667451416-3">}</span><span class="p" data-group-id="1667451416-2">]</span><span class="p" data-group-id="1667451416-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="4551942813-1">(</span><span class="n">Tab</span><span class="p" data-group-id="4551942813-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="4551942813-2">(</span><span class="nf">fun</span><span class="p" data-group-id="4551942813-3">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="4551942813-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │                                  </span><span class="s">&quot;Bryan&quot;</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                                    </span><span class="p" data-group-id="1373350218-4">[</span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="1373350218-4">]</span><span class="p">;</span><span class="w">
│ │ │ +                                    </span><span class="p" data-group-id="4551942813-4">[</span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="4551942813-4">]</span><span class="p">;</span><span class="w">
│ │ │                                   </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                                       </span><span class="n">Acc</span><span class="w">
│ │ │                             </span><span class="k">end</span><span class="w">
│ │ │ -             </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1373350218-5">[</span><span class="p" data-group-id="1373350218-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="1373350218-2">)</span></code></pre><p>If you need all information stored in the Ets table about persons named &quot;Bryan&quot;,
│ │ │ -then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="7386185964-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7386185964-2">[</span><span class="p" data-group-id="7386185964-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7386185964-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4551942813-5">[</span><span class="p" data-group-id="4551942813-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="4551942813-2">)</span></code></pre><p>If you need all information stored in the Ets table about persons named &quot;Bryan&quot;,
│ │ │ +then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="5011129640-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5011129640-2">[</span><span class="p" data-group-id="5011129640-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5011129640-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │                            </span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Bryan&quot;</span><span class="p">,</span><span class="w">
│ │ │                            </span><span class="ss">age</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ -                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="7386185964-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7386185964-5">[</span><span class="p" data-group-id="7386185964-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7386185964-6">[</span><span class="ss">&#39;$_&#39;</span><span class="p" data-group-id="7386185964-6">]</span><span class="p" data-group-id="7386185964-3">}</span><span class="p" data-group-id="7386185964-2">]</span><span class="p" data-group-id="7386185964-1">)</span><span class="p">,</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="7218669538-1">(</span><span class="n">Tab</span><span class="p" data-group-id="7218669538-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="7218669538-2">(</span><span class="nf">fun</span><span class="p" data-group-id="7218669538-3">(</span><span class="n">X</span><span class="p" data-group-id="7218669538-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="s">&quot;Bryan&quot;</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="7218669538-2">)</span><span class="p">,</span></code></pre><h3 id="ordered_set-tables" class="section-heading">
│ │ │ +                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="5011129640-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5011129640-5">[</span><span class="p" data-group-id="5011129640-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5011129640-6">[</span><span class="ss">&#39;$_&#39;</span><span class="p" data-group-id="5011129640-6">]</span><span class="p" data-group-id="5011129640-3">}</span><span class="p" data-group-id="5011129640-2">]</span><span class="p" data-group-id="5011129640-1">)</span><span class="p">,</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="2829137388-1">(</span><span class="n">Tab</span><span class="p" data-group-id="2829137388-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="2829137388-2">(</span><span class="nf">fun</span><span class="p" data-group-id="2829137388-3">(</span><span class="n">X</span><span class="p" data-group-id="2829137388-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="s">&quot;Bryan&quot;</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="2829137388-2">)</span><span class="p">,</span></code></pre><h3 id="ordered_set-tables" class="section-heading">
│ │ │    <a href="#ordered_set-tables" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text"><code class="inline">ordered_set</code> Tables</span>
│ │ │  </h3>
│ │ │  <p>If the data in the table is to be accessed so that the order of the keys in the
│ │ │  table is significant, the table type <code class="inline">ordered_set</code> can be used instead of the
│ │ │ @@ -293,20 +293,20 @@
│ │ │  Clearly, the second table would have to be kept consistent with the master
│ │ │  table. Mnesia can do this for you, but a home-brew index table can be very
│ │ │  efficient compared to the overhead involved in using Mnesia.</p><p>An index table for the table in the previous examples would have to be a bag (as
│ │ │  keys would appear more than once) and can have the following contents:</p><pre><code class="text">[#index_entry{name=&quot;Adam&quot;, idno=1},
│ │ │   #index_entry{name=&quot;Bryan&quot;, idno=2},
│ │ │   #index_entry{name=&quot;Bryan&quot;, idno=3},
│ │ │   #index_entry{name=&quot;Carl&quot;, idno=4}]</code></pre><p>Given this index table, a lookup of the <code class="inline">age</code> fields for all persons named
│ │ │ -&quot;Bryan&quot; can be done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="n">MatchingIDs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1090409938-1">(</span><span class="n">IndexTable</span><span class="p">,</span><span class="s">&quot;Bryan&quot;</span><span class="p" data-group-id="1090409938-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="1090409938-2">(</span><span class="nf">fun</span><span class="p" data-group-id="1090409938-3">(</span><span class="o">#</span><span class="ss">index_entry</span><span class="p" data-group-id="1090409938-4">{</span><span class="ss">idno</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ID</span><span class="p" data-group-id="1090409938-4">}</span><span class="p" data-group-id="1090409938-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                 </span><span class="p" data-group-id="1090409938-5">[</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1090409938-6">{</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="1090409938-6">}</span><span class="p" data-group-id="1090409938-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1090409938-7">(</span><span class="n">PersonTable</span><span class="p">,</span><span class="w"> </span><span class="n">ID</span><span class="p" data-group-id="1090409938-7">)</span><span class="p">,</span><span class="w">
│ │ │ +&quot;Bryan&quot; can be done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="n">MatchingIDs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="9086721806-1">(</span><span class="n">IndexTable</span><span class="p">,</span><span class="s">&quot;Bryan&quot;</span><span class="p" data-group-id="9086721806-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="9086721806-2">(</span><span class="nf">fun</span><span class="p" data-group-id="9086721806-3">(</span><span class="o">#</span><span class="ss">index_entry</span><span class="p" data-group-id="9086721806-4">{</span><span class="ss">idno</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ID</span><span class="p" data-group-id="9086721806-4">}</span><span class="p" data-group-id="9086721806-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                 </span><span class="p" data-group-id="9086721806-5">[</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9086721806-6">{</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="9086721806-6">}</span><span class="p" data-group-id="9086721806-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="9086721806-7">(</span><span class="n">PersonTable</span><span class="p">,</span><span class="w"> </span><span class="n">ID</span><span class="p" data-group-id="9086721806-7">)</span><span class="p">,</span><span class="w">
│ │ │                   </span><span class="n">Age</span><span class="w">
│ │ │            </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="n">MatchingIDs</span><span class="p" data-group-id="1090409938-2">)</span><span class="p">,</span></code></pre><p>Notice that this code does not use <a href="../../lib/stdlib-8.0/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a>, but instead uses the
│ │ │ +          </span><span class="n">MatchingIDs</span><span class="p" data-group-id="9086721806-2">)</span><span class="p">,</span></code></pre><p>Notice that this code does not use <a href="../../lib/stdlib-8.0/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a>, but instead uses the
│ │ │  <a href="../../lib/stdlib-8.0/doc/html/ets.html#lookup/2"><code class="inline">ets:lookup/2</code></a> call. The <a href="../../lib/stdlib-8.0/doc/html/lists.html#map/2"><code class="inline">lists:map/2</code></a> call is only used to traverse the <code class="inline">idno</code>s
│ │ │  matching the name &quot;Bryan&quot; in the table; thus the number of lookups in the master
│ │ │  table is minimized.</p><p>Keeping an index table introduces some overhead when inserting records in the
│ │ │  table. The number of operations gained from the table must therefore be compared
│ │ │  against the number of operations inserting objects in the table. However, notice
│ │ │  that the gain is significant when the key can be used to lookup elements.</p><h2 id="mnesia" class="section-heading">
│ │ │    <a href="#mnesia" class="hover-link">
│ │ │ @@ -321,51 +321,51 @@
│ │ │    <span class="text">Secondary Index</span>
│ │ │  </h3>
│ │ │  <p>If you frequently do lookups on a field that is not the key of the table, you
│ │ │  lose performance using <a href="../../lib/mnesia-4.26/doc/html/mnesia.html#select/3">mnesia:select()</a> or
│ │ │  <a href="../../lib/mnesia-4.26/doc/html/mnesia.html#match_object/1"><code class="inline">mnesia:match_object()</code></a> as these functions traverse
│ │ │  the whole table. Instead, you can create a secondary index and use
│ │ │  <a href="../../lib/mnesia-4.26/doc/html/mnesia.html#index_read/3"><code class="inline">mnesia:index_read/3</code></a> to get faster access at the expense of using more
│ │ │ -memory.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7865745275-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7865745275-2">{</span><span class="ss">idno</span><span class="p">,</span><span class="w"> </span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="ss">occupation</span><span class="p" data-group-id="7865745275-2">}</span><span class="p" data-group-id="7865745275-1">)</span><span class="p">.</span><span class="w">
│ │ │ +memory.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6276437322-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6276437322-2">{</span><span class="ss">idno</span><span class="p">,</span><span class="w"> </span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="ss">occupation</span><span class="p" data-group-id="6276437322-2">}</span><span class="p" data-group-id="6276437322-1">)</span><span class="p">.</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7865745275-3">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="7865745275-3">}</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ -</span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">create_table</span><span class="p" data-group-id="7865745275-4">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7865745275-5">[</span><span class="p" data-group-id="7865745275-6">{</span><span class="ss">index</span><span class="p">,</span><span class="p" data-group-id="7865745275-7">[</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="7865745275-7">]</span><span class="p" data-group-id="7865745275-6">}</span><span class="p">,</span><span class="w">
│ │ │ -                              </span><span class="p" data-group-id="7865745275-8">{</span><span class="ss">attributes</span><span class="p">,</span><span class="w">
│ │ │ -                                    </span><span class="nf">record_info</span><span class="p" data-group-id="7865745275-9">(</span><span class="ss">fields</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="7865745275-9">)</span><span class="p" data-group-id="7865745275-8">}</span><span class="p" data-group-id="7865745275-5">]</span><span class="p" data-group-id="7865745275-4">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7865745275-10">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="7865745275-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">add_table_index</span><span class="p" data-group-id="7865745275-11">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="7865745275-11">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6276437322-3">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="6276437322-3">}</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ +</span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">create_table</span><span class="p" data-group-id="6276437322-4">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6276437322-5">[</span><span class="p" data-group-id="6276437322-6">{</span><span class="ss">index</span><span class="p">,</span><span class="p" data-group-id="6276437322-7">[</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="6276437322-7">]</span><span class="p" data-group-id="6276437322-6">}</span><span class="p">,</span><span class="w">
│ │ │ +                              </span><span class="p" data-group-id="6276437322-8">{</span><span class="ss">attributes</span><span class="p">,</span><span class="w">
│ │ │ +                                    </span><span class="nf">record_info</span><span class="p" data-group-id="6276437322-9">(</span><span class="ss">fields</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="6276437322-9">)</span><span class="p" data-group-id="6276437322-8">}</span><span class="p" data-group-id="6276437322-5">]</span><span class="p" data-group-id="6276437322-4">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6276437322-10">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="6276437322-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">add_table_index</span><span class="p" data-group-id="6276437322-11">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="6276437322-11">)</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="n">PersonsAge42</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ -     </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_index_read</span><span class="p" data-group-id="7865745275-12">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="7865745275-12">)</span><span class="p">,</span></code></pre><h3 id="transactions" class="section-heading">
│ │ │ +     </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_index_read</span><span class="p" data-group-id="6276437322-12">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="6276437322-12">)</span><span class="p">,</span></code></pre><h3 id="transactions" class="section-heading">
│ │ │    <a href="#transactions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Transactions</span>
│ │ │  </h3>
│ │ │  <p>Using transactions is a way to guarantee that the distributed Mnesia database
│ │ │  remains consistent, even when many different processes update it in parallel.
│ │ │  However, if you have real-time requirements it is recommended to use dirty
│ │ │  operations instead of transactions. When using dirty operations, you lose the
│ │ │  consistency guarantee; this is usually solved by only letting one process update
│ │ │  the table. Other processes must send update requests to that process.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% Using transaction</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="9519328396-1">(</span><span class="p" data-group-id="9519328396-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -          </span><span class="p" data-group-id="9519328396-2">[</span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="9519328396-3">(</span><span class="p" data-group-id="9519328396-4">{</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="9519328396-4">}</span><span class="p" data-group-id="9519328396-3">)</span><span class="p">,</span><span class="w">
│ │ │ -           </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="9519328396-5">(</span><span class="p" data-group-id="9519328396-6">{</span><span class="n">Table2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="p" data-group-id="9519328396-6">}</span><span class="p" data-group-id="9519328396-5">)</span><span class="p" data-group-id="9519328396-2">]</span><span class="w">
│ │ │ +</span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="5232131557-1">(</span><span class="p" data-group-id="5232131557-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +          </span><span class="p" data-group-id="5232131557-2">[</span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="5232131557-3">(</span><span class="p" data-group-id="5232131557-4">{</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="5232131557-4">}</span><span class="p" data-group-id="5232131557-3">)</span><span class="p">,</span><span class="w">
│ │ │ +           </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="5232131557-5">(</span><span class="p" data-group-id="5232131557-6">{</span><span class="n">Table2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="p" data-group-id="5232131557-6">}</span><span class="p" data-group-id="5232131557-5">)</span><span class="p" data-group-id="5232131557-2">]</span><span class="w">
│ │ │        </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │  
│ │ │ -</span><span class="p" data-group-id="9519328396-7">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9519328396-8">[</span><span class="n">Result1</span><span class="p">,</span><span class="w"> </span><span class="n">Result2</span><span class="p" data-group-id="9519328396-8">]</span><span class="p" data-group-id="9519328396-7">}</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">transaction</span><span class="p" data-group-id="9519328396-9">(</span><span class="n">Fun</span><span class="p" data-group-id="9519328396-9">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5232131557-7">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5232131557-8">[</span><span class="n">Result1</span><span class="p">,</span><span class="w"> </span><span class="n">Result2</span><span class="p" data-group-id="5232131557-8">]</span><span class="p" data-group-id="5232131557-7">}</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">transaction</span><span class="p" data-group-id="5232131557-9">(</span><span class="n">Fun</span><span class="p" data-group-id="5232131557-9">)</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% Same thing using dirty operations</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Result1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_read</span><span class="p" data-group-id="9519328396-10">(</span><span class="p" data-group-id="9519328396-11">{</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="9519328396-11">}</span><span class="p" data-group-id="9519328396-10">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Result2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_read</span><span class="p" data-group-id="9519328396-12">(</span><span class="p" data-group-id="9519328396-13">{</span><span class="n">Table2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="p" data-group-id="9519328396-13">}</span><span class="p" data-group-id="9519328396-12">)</span><span class="p">,</span></code></pre>
│ │ │ +</span><span class="n">Result1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_read</span><span class="p" data-group-id="5232131557-10">(</span><span class="p" data-group-id="5232131557-11">{</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="5232131557-11">}</span><span class="p" data-group-id="5232131557-10">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Result2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_read</span><span class="p" data-group-id="5232131557-12">(</span><span class="p" data-group-id="5232131557-13">{</span><span class="n">Table2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="p" data-group-id="5232131557-13">}</span><span class="p" data-group-id="5232131557-12">)</span><span class="p">,</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="eff_guide_functions.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/typespec.html
│ │ │ @@ -238,128 +238,128 @@
│ │ │  and optional <code class="inline">(=&gt;)</code> association types. If an association type is mandatory, an
│ │ │  association with that type needs to be present. In the case of an optional
│ │ │  association type it is not required for the key type to be present.</p><p>The notation <code class="inline">#{}</code> specifies the singleton type for the empty map. Note that
│ │ │  this notation is not a shorthand for the <a href="../../erts-17.0/doc/html/erlang.html#t:map/0"><code class="inline">map/0</code></a> type.</p><p>For convenience, the following types are also built-in. They can be thought of as
│ │ │  predefined aliases for the type unions also shown in the table.</p><p><a href="" id="builtin_types"></a></p><table><thead><tr><th style="text-align: left;">Built-in type</th><th style="text-align: left;">Defined as</th></tr></thead><tbody><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:term/0"><code class="inline">term/0</code></a></td><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:any/0"><code class="inline">any/0</code></a></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:binary/0"><code class="inline">binary/0</code></a></td><td style="text-align: left;"><code class="inline">&lt;&lt;_:_*8&gt;&gt;</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:nonempty_binary/0"><code class="inline">nonempty_binary/0</code></a></td><td style="text-align: left;"><code class="inline">&lt;&lt;_:8, _:_*8&gt;&gt;</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:bitstring/0"><code class="inline">bitstring/0</code></a></td><td style="text-align: left;"><code class="inline">&lt;&lt;_:_*1&gt;&gt;</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:nonempty_bitstring/0"><code class="inline">nonempty_bitstring/0</code></a></td><td style="text-align: left;"><code class="inline">&lt;&lt;_:1, _:_*1&gt;&gt;</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:boolean/0"><code class="inline">boolean/0</code></a></td><td style="text-align: left;"><code class="inline">'false'</code> | <code class="inline">'true'</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:byte/0"><code class="inline">byte/0</code></a></td><td style="text-align: left;"><code class="inline">0..255</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:char/0"><code class="inline">char/0</code></a></td><td style="text-align: left;"><code class="inline">0..16#10ffff</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:nil/0"><code class="inline">nil/0</code></a></td><td style="text-align: left;"><code class="inline">[]</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:number/0"><code class="inline">number/0</code></a></td><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:integer/0"><code class="inline">integer/0</code></a> | <a href="../../erts-17.0/doc/html/erlang.html#t:float/0"><code class="inline">float/0</code></a></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:list/0"><code class="inline">list/0</code></a></td><td style="text-align: left;"><code class="inline">[any()]</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:maybe_improper_list/0"><code class="inline">maybe_improper_list/0</code></a></td><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:maybe_improper_list/2"><code class="inline">maybe_improper_list(any(), any())</code></a></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:nonempty_list/0"><code class="inline">nonempty_list/0</code></a></td><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:nonempty_list/1"><code class="inline">nonempty_list(any())</code></a></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:string/0"><code class="inline">string/0</code></a></td><td style="text-align: left;"><code class="inline">[char()]</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:nonempty_string/0"><code class="inline">nonempty_string/0</code></a></td><td style="text-align: left;"><code class="inline">[char(), ...]</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:iodata/0"><code class="inline">iodata/0</code></a></td><td style="text-align: left;"><code class="inline">iolist()</code> | <code class="inline">binary()</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:iolist/0"><code class="inline">iolist/0</code></a></td><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:maybe_improper_list/2"><code class="inline">maybe_improper_list(byte() | binary() | iolist(), binary() | [])</code></a></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:map/0"><code class="inline">map/0</code></a></td><td style="text-align: left;"><code class="inline">#{any() =&gt; any()}</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:function/0"><code class="inline">function/0</code></a></td><td style="text-align: left;"><code class="inline">fun()</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:module/0"><code class="inline">module/0</code></a></td><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:atom/0"><code class="inline">atom/0</code></a></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:mfa/0"><code class="inline">mfa/0</code></a></td><td style="text-align: left;"><code class="inline">{module(),atom(),arity()}</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:arity/0"><code class="inline">arity/0</code></a></td><td style="text-align: left;"><code class="inline">0..255</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:identifier/0"><code class="inline">identifier/0</code></a></td><td style="text-align: left;"><code class="inline">pid()</code> | <code class="inline">port()</code> | <code class="inline">reference()</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#node/0"><code class="inline">node/0</code></a></td><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:atom/0"><code class="inline">atom/0</code></a></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:timeout/0"><code class="inline">timeout/0</code></a></td><td style="text-align: left;"><code class="inline">'infinity'</code> | <code class="inline">non_neg_integer()</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:no_return/0"><code class="inline">no_return/0</code></a></td><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:none/0"><code class="inline">none/0</code></a></td></tr></tbody></table><p><em>Table: Built-in types, predefined aliases</em></p><p>In addition, the following three built-in types exist and can be thought of as
│ │ │  defined below, though strictly their &quot;type definition&quot; is not valid syntax
│ │ │  according to the type language defined above.</p><table><thead><tr><th style="text-align: left;">Built-in type</th><th style="text-align: left;">Can be thought of as defined by the syntax</th></tr></thead><tbody><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:non_neg_integer/0"><code class="inline">non_neg_integer/0</code></a></td><td style="text-align: left;"><code class="inline">0..</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:pos_integer/0"><code class="inline">pos_integer/0</code></a></td><td style="text-align: left;"><code class="inline">1..</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-17.0/doc/html/erlang.html#t:neg_integer/0"><code class="inline">neg_integer/0</code></a></td><td style="text-align: left;"><code class="inline">..-1</code></td></tr></tbody></table><p><em>Table: Additional built-in types</em></p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The following built-in list types also exist, but they are expected to be
│ │ │ -rarely used. Hence, they have long names:</p></section><pre><code class="makeup erlang" translate="no"><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="2213129437-1">(</span><span class="p" data-group-id="2213129437-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="2213129437-2">(</span><span class="nf">any</span><span class="p" data-group-id="2213129437-3">(</span><span class="p" data-group-id="2213129437-3">)</span><span class="p">,</span><span class="w"> </span><span class="nf">any</span><span class="p" data-group-id="2213129437-4">(</span><span class="p" data-group-id="2213129437-4">)</span><span class="p" data-group-id="2213129437-2">)</span><span class="w">
│ │ │ -</span><span class="nf">nonempty_improper_list</span><span class="p" data-group-id="2213129437-5">(</span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="n">Type2</span><span class="p" data-group-id="2213129437-5">)</span><span class="w">
│ │ │ -</span><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="2213129437-6">(</span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="n">Type2</span><span class="p" data-group-id="2213129437-6">)</span></code></pre><p>where the last two types define the set of Erlang terms one would expect.</p><p>Also for convenience, record notation is allowed to be used. Records are
│ │ │ -shorthands for the corresponding tuples:</p><pre><code class="makeup erlang" translate="no"><span class="n">Record</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p">#</span><span class="n">Erlang_Atom</span><span class="p" data-group-id="0547116706-1">{</span><span class="p" data-group-id="0547116706-1">}</span><span class="w">
│ │ │ -        </span><span class="p">|</span><span class="w"> </span><span class="p">#</span><span class="n">Erlang_Atom</span><span class="p" data-group-id="0547116706-2">{</span><span class="n">Fields</span><span class="p" data-group-id="0547116706-2">}</span></code></pre><p>Records are extended to possibly contain type information. This is described in
│ │ │ +rarely used. Hence, they have long names:</p></section><pre><code class="makeup erlang" translate="no"><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="2175935931-1">(</span><span class="p" data-group-id="2175935931-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="2175935931-2">(</span><span class="nf">any</span><span class="p" data-group-id="2175935931-3">(</span><span class="p" data-group-id="2175935931-3">)</span><span class="p">,</span><span class="w"> </span><span class="nf">any</span><span class="p" data-group-id="2175935931-4">(</span><span class="p" data-group-id="2175935931-4">)</span><span class="p" data-group-id="2175935931-2">)</span><span class="w">
│ │ │ +</span><span class="nf">nonempty_improper_list</span><span class="p" data-group-id="2175935931-5">(</span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="n">Type2</span><span class="p" data-group-id="2175935931-5">)</span><span class="w">
│ │ │ +</span><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="2175935931-6">(</span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="n">Type2</span><span class="p" data-group-id="2175935931-6">)</span></code></pre><p>where the last two types define the set of Erlang terms one would expect.</p><p>Also for convenience, record notation is allowed to be used. Records are
│ │ │ +shorthands for the corresponding tuples:</p><pre><code class="makeup erlang" translate="no"><span class="n">Record</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p">#</span><span class="n">Erlang_Atom</span><span class="p" data-group-id="0559219693-1">{</span><span class="p" data-group-id="0559219693-1">}</span><span class="w">
│ │ │ +        </span><span class="p">|</span><span class="w"> </span><span class="p">#</span><span class="n">Erlang_Atom</span><span class="p" data-group-id="0559219693-2">{</span><span class="n">Fields</span><span class="p" data-group-id="0559219693-2">}</span></code></pre><p>Records are extended to possibly contain type information. This is described in
│ │ │  <a href="typespec.html#typeinrecords">Type Information in Record Declarations</a>.</p><h3 id="redefining-built-in-types" class="section-heading">
│ │ │    <a href="#redefining-built-in-types" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Redefining built-in types</span>
│ │ │  </h3>
│ │ │  <section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Starting from Erlang/OTP 26, it is permitted to define a type having the same
│ │ │  name as a built-in type.</p></section><p>It is recommended to avoid deliberately reusing built-in names because it can be
│ │ │  confusing. However, when an Erlang/OTP release introduces a new type, code that
│ │ │  happened to define its own type having the same name will continue to work.</p><p>As an example, imagine that the Erlang/OTP 42 release introduces a new type
│ │ │ -<code class="inline">gadget()</code> defined like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">gadget</span><span class="p" data-group-id="1010816743-1">(</span><span class="p" data-group-id="1010816743-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="1010816743-2">{</span><span class="ss">&#39;gadget&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">reference</span><span class="p" data-group-id="1010816743-3">(</span><span class="p" data-group-id="1010816743-3">)</span><span class="p" data-group-id="1010816743-2">}</span><span class="p">.</span></code></pre><p>Further imagine that some code has its own (different) definition of <code class="inline">gadget()</code>,
│ │ │ -for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">gadget</span><span class="p" data-group-id="8601940957-1">(</span><span class="p" data-group-id="8601940957-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="8601940957-2">#{</span><span class="p" data-group-id="8601940957-2">}</span><span class="p">.</span></code></pre><p>Since redefinitions are allowed, the code will still compile (but with a
│ │ │ +<code class="inline">gadget()</code> defined like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">gadget</span><span class="p" data-group-id="6783918349-1">(</span><span class="p" data-group-id="6783918349-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="6783918349-2">{</span><span class="ss">&#39;gadget&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">reference</span><span class="p" data-group-id="6783918349-3">(</span><span class="p" data-group-id="6783918349-3">)</span><span class="p" data-group-id="6783918349-2">}</span><span class="p">.</span></code></pre><p>Further imagine that some code has its own (different) definition of <code class="inline">gadget()</code>,
│ │ │ +for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">gadget</span><span class="p" data-group-id="8949416311-1">(</span><span class="p" data-group-id="8949416311-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="8949416311-2">#{</span><span class="p" data-group-id="8949416311-2">}</span><span class="p">.</span></code></pre><p>Since redefinitions are allowed, the code will still compile (but with a
│ │ │  warning), and Dialyzer will not emit any additional warnings.</p><h2 id="type-declarations-of-user-defined-types" class="section-heading">
│ │ │    <a href="#type-declarations-of-user-defined-types" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Type Declarations of User-Defined Types</span>
│ │ │  </h2>
│ │ │  <p>As seen, the basic syntax of a type is an atom followed by closed parentheses.
│ │ │  New types are declared using <code class="inline">-type</code>, <a href="opaques.html"><code class="inline">-opaque</code></a>, and
│ │ │ -<a href="nominals.html"><code class="inline">-nominal</code></a> attributes as in the following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">my_struct_type</span><span class="p" data-group-id="5024090001-1">(</span><span class="p" data-group-id="5024090001-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">my_opaq_type</span><span class="p" data-group-id="5024090001-2">(</span><span class="p" data-group-id="5024090001-2">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">my_nominal_type</span><span class="p" data-group-id="5024090001-3">(</span><span class="p" data-group-id="5024090001-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span></code></pre><p>The type name is the atom <code class="inline">my_struct_type</code>, followed by parentheses. <code class="inline">Type</code> is a
│ │ │ +<a href="nominals.html"><code class="inline">-nominal</code></a> attributes as in the following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">my_struct_type</span><span class="p" data-group-id="6615415070-1">(</span><span class="p" data-group-id="6615415070-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">my_opaq_type</span><span class="p" data-group-id="6615415070-2">(</span><span class="p" data-group-id="6615415070-2">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">nominal</span><span class="w"> </span><span class="nf">my_nominal_type</span><span class="p" data-group-id="6615415070-3">(</span><span class="p" data-group-id="6615415070-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span></code></pre><p>The type name is the atom <code class="inline">my_struct_type</code>, followed by parentheses. <code class="inline">Type</code> is a
│ │ │  type as defined in the previous section. A current restriction is that <code class="inline">Type</code>
│ │ │  can contain only predefined types, or user-defined types which are either of the
│ │ │  following:</p><ul><li>Module-local type, that is, with a definition that is present in the code of
│ │ │  the module</li><li>Remote type, that is, type defined in, and exported by, other modules; more
│ │ │  about this soon.</li></ul><p>For module-local types, the restriction that their definition exists in the
│ │ │  module is enforced by the compiler and results in a compilation error. (A
│ │ │  similar restriction currently exists for records.)</p><p>Type declarations can also be parameterized by including type variables between
│ │ │  the parentheses. The syntax of type variables is the same as Erlang variables,
│ │ │  that is, they start with an uppercase letter. These variables are to
│ │ │ -appear on the RHS of the definition. A concrete example follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">orddict</span><span class="p" data-group-id="4178569603-1">(</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Val</span><span class="p" data-group-id="4178569603-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="4178569603-2">[</span><span class="p" data-group-id="4178569603-3">{</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Val</span><span class="p" data-group-id="4178569603-3">}</span><span class="p" data-group-id="4178569603-2">]</span><span class="p">.</span></code></pre><p>A module can export some types to declare that other modules are allowed to
│ │ │ -refer to them as <em>remote types</em>. This declaration has the following form:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export_type</span><span class="p" data-group-id="6784509979-1">(</span><span class="p" data-group-id="6784509979-2">[</span><span class="n">T1</span><span class="o">/</span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Tk</span><span class="o">/</span><span class="n">Ak</span><span class="p" data-group-id="6784509979-2">]</span><span class="p" data-group-id="6784509979-1">)</span><span class="p">.</span></code></pre><p>Here the <code class="inline">Ti</code>s are atoms (the name of the type) and the <code class="inline">Ai</code>s are their arities.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export_type</span><span class="p" data-group-id="4586894895-1">(</span><span class="p" data-group-id="4586894895-2">[</span><span class="ss">my_struct_type</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">orddict</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4586894895-2">]</span><span class="p" data-group-id="4586894895-1">)</span><span class="p">.</span></code></pre><p>Assuming that these types are exported from module <code class="inline">'mod'</code>, you can refer to
│ │ │ -them from other modules using remote type expressions like the following:</p><pre><code class="makeup erlang" translate="no"><span class="nc">mod</span><span class="p">:</span><span class="nf">my_struct_type</span><span class="p" data-group-id="0684591302-1">(</span><span class="p" data-group-id="0684591302-1">)</span><span class="w">
│ │ │ -</span><span class="nc">mod</span><span class="p">:</span><span class="nf">orddict</span><span class="p" data-group-id="0684591302-2">(</span><span class="nf">atom</span><span class="p" data-group-id="0684591302-3">(</span><span class="p" data-group-id="0684591302-3">)</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="0684591302-4">(</span><span class="p" data-group-id="0684591302-4">)</span><span class="p" data-group-id="0684591302-2">)</span></code></pre><p>It is not allowed to refer to types that are not declared as exported.</p><p>Types declared as <code class="inline">opaque</code> represent sets of terms whose structure is not
│ │ │ +appear on the RHS of the definition. A concrete example follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">orddict</span><span class="p" data-group-id="0301357335-1">(</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Val</span><span class="p" data-group-id="0301357335-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0301357335-2">[</span><span class="p" data-group-id="0301357335-3">{</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Val</span><span class="p" data-group-id="0301357335-3">}</span><span class="p" data-group-id="0301357335-2">]</span><span class="p">.</span></code></pre><p>A module can export some types to declare that other modules are allowed to
│ │ │ +refer to them as <em>remote types</em>. This declaration has the following form:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export_type</span><span class="p" data-group-id="9444874587-1">(</span><span class="p" data-group-id="9444874587-2">[</span><span class="n">T1</span><span class="o">/</span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Tk</span><span class="o">/</span><span class="n">Ak</span><span class="p" data-group-id="9444874587-2">]</span><span class="p" data-group-id="9444874587-1">)</span><span class="p">.</span></code></pre><p>Here the <code class="inline">Ti</code>s are atoms (the name of the type) and the <code class="inline">Ai</code>s are their arities.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export_type</span><span class="p" data-group-id="5089910833-1">(</span><span class="p" data-group-id="5089910833-2">[</span><span class="ss">my_struct_type</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">orddict</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5089910833-2">]</span><span class="p" data-group-id="5089910833-1">)</span><span class="p">.</span></code></pre><p>Assuming that these types are exported from module <code class="inline">'mod'</code>, you can refer to
│ │ │ +them from other modules using remote type expressions like the following:</p><pre><code class="makeup erlang" translate="no"><span class="nc">mod</span><span class="p">:</span><span class="nf">my_struct_type</span><span class="p" data-group-id="2415044279-1">(</span><span class="p" data-group-id="2415044279-1">)</span><span class="w">
│ │ │ +</span><span class="nc">mod</span><span class="p">:</span><span class="nf">orddict</span><span class="p" data-group-id="2415044279-2">(</span><span class="nf">atom</span><span class="p" data-group-id="2415044279-3">(</span><span class="p" data-group-id="2415044279-3">)</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="2415044279-4">(</span><span class="p" data-group-id="2415044279-4">)</span><span class="p" data-group-id="2415044279-2">)</span></code></pre><p>It is not allowed to refer to types that are not declared as exported.</p><p>Types declared as <code class="inline">opaque</code> represent sets of terms whose structure is not
│ │ │  supposed to be visible from outside of their defining module. That is, only the
│ │ │  module defining them is allowed to depend on their term structure. Consequently,
│ │ │  such types do not make much sense as module local - module local types are not
│ │ │  accessible by other modules anyway - and are always to be exported.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Nominal types were introduced in Erlang/OTP 28.</p></section><p>Types declared as <code class="inline">nominal</code> are type-checked according to the user-defined
│ │ │  names instead of their structure. That is, <code class="inline">-nominal feet() :: integer()</code> and
│ │ │  <code class="inline">-nominal meter() :: integer()</code> are not the same type, while if <code class="inline">-type</code> is
│ │ │  used it would be.</p><p>Read more on <a href="opaques.html">Opaques</a> and <a href="nominals.html">Nominals</a>.</p><p><a href="" id="typeinrecords"></a></p><h2 id="type-information-in-record-declarations" class="section-heading">
│ │ │    <a href="#type-information-in-record-declarations" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Type Information in Record Declarations</span>
│ │ │  </h2>
│ │ │  <p>The types of record fields can be specified in the declaration of the record.
│ │ │ -The syntax for this is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0077462138-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0077462138-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="0077462138-2">}</span><span class="p" data-group-id="0077462138-1">)</span><span class="p">.</span></code></pre><p>For fields without type annotations, their type defaults to <code class="inline">any()</code>. That is, the
│ │ │ -previous example is a shorthand for the following:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6430364653-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6430364653-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">any</span><span class="p" data-group-id="6430364653-3">(</span><span class="p" data-group-id="6430364653-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="6430364653-2">}</span><span class="p" data-group-id="6430364653-1">)</span><span class="p">.</span></code></pre><p>In the presence of initial values for fields, the type must be declared after
│ │ │ -the initialization, as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8291580990-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8291580990-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8291580990-3">[</span><span class="p" data-group-id="8291580990-3">]</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="8291580990-2">}</span><span class="p" data-group-id="8291580990-1">)</span><span class="p">.</span></code></pre><p>The initial values for fields are to be compatible with (that is, a member of)
│ │ │ +The syntax for this is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0537636337-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0537636337-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="0537636337-2">}</span><span class="p" data-group-id="0537636337-1">)</span><span class="p">.</span></code></pre><p>For fields without type annotations, their type defaults to <code class="inline">any()</code>. That is, the
│ │ │ +previous example is a shorthand for the following:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2420725550-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2420725550-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">any</span><span class="p" data-group-id="2420725550-3">(</span><span class="p" data-group-id="2420725550-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="2420725550-2">}</span><span class="p" data-group-id="2420725550-1">)</span><span class="p">.</span></code></pre><p>In the presence of initial values for fields, the type must be declared after
│ │ │ +the initialization, as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6960750406-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6960750406-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6960750406-3">[</span><span class="p" data-group-id="6960750406-3">]</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="6960750406-2">}</span><span class="p" data-group-id="6960750406-1">)</span><span class="p">.</span></code></pre><p>The initial values for fields are to be compatible with (that is, a member of)
│ │ │  the corresponding types. This is checked by the compiler and results in a
│ │ │  compilation error if a violation is detected.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 19, for fields without initial values, the singleton type
│ │ │  <code class="inline">'undefined'</code> was added to all declared types. In other words, the following
│ │ │ -two record declarations had identical effects:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4228172525-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4228172525-2">{</span><span class="ss">f1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="4228172525-3">(</span><span class="p" data-group-id="4228172525-3">)</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="ss">f2</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">float</span><span class="p" data-group-id="4228172525-4">(</span><span class="p" data-group-id="4228172525-4">)</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="ss">f3</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;a&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;b&#39;</span><span class="p" data-group-id="4228172525-2">}</span><span class="p" data-group-id="4228172525-1">)</span><span class="p">.</span><span class="w">
│ │ │ +two record declarations had identical effects:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4746716336-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4746716336-2">{</span><span class="ss">f1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="4746716336-3">(</span><span class="p" data-group-id="4746716336-3">)</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="ss">f2</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">float</span><span class="p" data-group-id="4746716336-4">(</span><span class="p" data-group-id="4746716336-4">)</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="ss">f3</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;a&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;b&#39;</span><span class="p" data-group-id="4746716336-2">}</span><span class="p" data-group-id="4746716336-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4228172525-5">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4228172525-6">{</span><span class="ss">f1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="4228172525-7">(</span><span class="p" data-group-id="4228172525-7">)</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="ss">f2</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;undefined&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">float</span><span class="p" data-group-id="4228172525-8">(</span><span class="p" data-group-id="4228172525-8">)</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="ss">f3</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;undefined&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;a&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;b&#39;</span><span class="p" data-group-id="4228172525-6">}</span><span class="p" data-group-id="4228172525-5">)</span><span class="p">.</span></code></pre><p>This is no longer the case. If you require <code class="inline">'undefined'</code> in your record field
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4746716336-5">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4746716336-6">{</span><span class="ss">f1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="4746716336-7">(</span><span class="p" data-group-id="4746716336-7">)</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="ss">f2</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;undefined&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">float</span><span class="p" data-group-id="4746716336-8">(</span><span class="p" data-group-id="4746716336-8">)</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="ss">f3</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;undefined&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;a&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;b&#39;</span><span class="p" data-group-id="4746716336-6">}</span><span class="p" data-group-id="4746716336-5">)</span><span class="p">.</span></code></pre><p>This is no longer the case. If you require <code class="inline">'undefined'</code> in your record field
│ │ │  type, you must explicitly add it to the typespec, as in the 2nd example.</p></section><p>Any record, containing type information or not, once defined, can be used as a
│ │ │  type using the following syntax:</p><pre><code class="text">#rec{}</code></pre><p>In addition, the record fields can be further specified when using a record type
│ │ │  by adding type information about the field as follows:</p><pre><code class="text">#rec{some_field :: Type}</code></pre><p>Any unspecified fields are assumed to have the type in the original record
│ │ │  declaration.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>When records are used to create patterns for ETS and Mnesia match functions,
│ │ │ -Dialyzer may need some help not to emit bad warnings. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="1344479551-1">(</span><span class="p" data-group-id="1344479551-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="1344479551-2">(</span><span class="p" data-group-id="1344479551-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1344479551-3">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1344479551-4">{</span><span class="ss">name</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="1344479551-5">(</span><span class="p" data-group-id="1344479551-5">)</span><span class="p">,</span><span class="w"> </span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="1344479551-6">(</span><span class="p" data-group-id="1344479551-6">)</span><span class="p" data-group-id="1344479551-4">}</span><span class="p" data-group-id="1344479551-3">)</span><span class="p">.</span><span class="w">
│ │ │ +Dialyzer may need some help not to emit bad warnings. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="6057075858-1">(</span><span class="p" data-group-id="6057075858-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="6057075858-2">(</span><span class="p" data-group-id="6057075858-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6057075858-3">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6057075858-4">{</span><span class="ss">name</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="6057075858-5">(</span><span class="p" data-group-id="6057075858-5">)</span><span class="p">,</span><span class="w"> </span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="6057075858-6">(</span><span class="p" data-group-id="6057075858-6">)</span><span class="p" data-group-id="6057075858-4">}</span><span class="p" data-group-id="6057075858-3">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">lookup</span><span class="p" data-group-id="1344479551-7">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Tab</span><span class="p" data-group-id="1344479551-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match_object</span><span class="p" data-group-id="1344479551-8">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1344479551-9">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="1344479551-9">}</span><span class="p" data-group-id="1344479551-8">)</span><span class="p">.</span></code></pre><p>Dialyzer will emit a warning since <code class="inline">'_'</code> is not in the type of record field
│ │ │ +</span><span class="nf">lookup</span><span class="p" data-group-id="6057075858-7">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Tab</span><span class="p" data-group-id="6057075858-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match_object</span><span class="p" data-group-id="6057075858-8">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6057075858-9">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="6057075858-9">}</span><span class="p" data-group-id="6057075858-8">)</span><span class="p">.</span></code></pre><p>Dialyzer will emit a warning since <code class="inline">'_'</code> is not in the type of record field
│ │ │  <code class="inline">height</code>.</p><p>The recommended way of dealing with this is to declare the smallest record
│ │ │  field types to accommodate all your needs, and then create refinements as
│ │ │ -needed. The modified example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2117907984-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2117907984-2">{</span><span class="ss">name</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="2117907984-3">(</span><span class="p" data-group-id="2117907984-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="2117907984-4">(</span><span class="p" data-group-id="2117907984-4">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="2117907984-2">}</span><span class="p" data-group-id="2117907984-1">)</span><span class="p">.</span><span class="w">
│ │ │ +needed. The modified example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0660469890-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0660469890-2">{</span><span class="ss">name</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="0660469890-3">(</span><span class="p" data-group-id="0660469890-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="0660469890-4">(</span><span class="p" data-group-id="0660469890-4">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="0660469890-2">}</span><span class="p" data-group-id="0660469890-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">person</span><span class="p" data-group-id="2117907984-5">(</span><span class="p" data-group-id="2117907984-5">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2117907984-6">{</span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="2117907984-7">(</span><span class="p" data-group-id="2117907984-7">)</span><span class="p" data-group-id="2117907984-6">}</span><span class="p">.</span></code></pre><p>In specifications and type declarations the type <code class="inline">person()</code> is to be preferred
│ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">person</span><span class="p" data-group-id="0660469890-5">(</span><span class="p" data-group-id="0660469890-5">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="0660469890-6">{</span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="0660469890-7">(</span><span class="p" data-group-id="0660469890-7">)</span><span class="p" data-group-id="0660469890-6">}</span><span class="p">.</span></code></pre><p>In specifications and type declarations the type <code class="inline">person()</code> is to be preferred
│ │ │  over <code class="inline">#person{}</code>.</p></section><h2 id="specifications-for-functions" class="section-heading">
│ │ │    <a href="#specifications-for-functions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Specifications for Functions</span>
│ │ │  </h2>
│ │ │  <p>A specification (or contract) for a function is given using the <code class="inline">-spec</code>
│ │ │  attribute. The general format is as follows:</p><pre><code class="text">-spec Function(ArgType1, ..., ArgTypeN) -&gt; ReturnType.</code></pre><p>An implementation of the function with the same name <code class="inline">Function</code> must exist in
│ │ │  the current module, and the arity of the function must match the number of
│ │ │  arguments, otherwise the compilation fails.</p><p>The following longer format with module name is also valid as long as <code class="inline">Module</code>
│ │ │  is the name of the current module. This can be useful for documentation
│ │ │  purposes.</p><pre><code class="text">-spec Module:Function(ArgType1, ..., ArgTypeN) -&gt; ReturnType.</code></pre><p>Also, for documentation purposes, argument names can be given:</p><pre><code class="text">-spec Function(ArgName1 :: Type1, ..., ArgNameN :: TypeN) -&gt; RT.</code></pre><p>A function specification can be overloaded. That is, it can have several types,
│ │ │ -separated by a semicolon (<code class="inline">;</code>). For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="7097831283-1">(</span><span class="n">T1</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p" data-group-id="7097831283-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">T3</span><span class="p">;</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="7097831283-2">(</span><span class="n">T4</span><span class="p">,</span><span class="w"> </span><span class="n">T5</span><span class="p" data-group-id="7097831283-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">T6</span><span class="p">.</span></code></pre><p>A current restriction, which currently results in a warning by Dialyzer, is that
│ │ │ +separated by a semicolon (<code class="inline">;</code>). For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="0999290933-1">(</span><span class="n">T1</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p" data-group-id="0999290933-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">T3</span><span class="p">;</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="0999290933-2">(</span><span class="n">T4</span><span class="p">,</span><span class="w"> </span><span class="n">T5</span><span class="p" data-group-id="0999290933-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">T6</span><span class="p">.</span></code></pre><p>A current restriction, which currently results in a warning by Dialyzer, is that
│ │ │  the domains of the argument types cannot overlap. For example, the following
│ │ │ -specification results in a warning:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="3209504832-1">(</span><span class="nf">pos_integer</span><span class="p" data-group-id="3209504832-2">(</span><span class="p" data-group-id="3209504832-2">)</span><span class="p" data-group-id="3209504832-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="3209504832-3">(</span><span class="p" data-group-id="3209504832-3">)</span><span class="p">;</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="3209504832-4">(</span><span class="nf">integer</span><span class="p" data-group-id="3209504832-5">(</span><span class="p" data-group-id="3209504832-5">)</span><span class="p" data-group-id="3209504832-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3209504832-6">(</span><span class="p" data-group-id="3209504832-6">)</span><span class="p">.</span></code></pre><p>Type variables can be used in specifications to specify relations for the input
│ │ │ +specification results in a warning:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="7891743246-1">(</span><span class="nf">pos_integer</span><span class="p" data-group-id="7891743246-2">(</span><span class="p" data-group-id="7891743246-2">)</span><span class="p" data-group-id="7891743246-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="7891743246-3">(</span><span class="p" data-group-id="7891743246-3">)</span><span class="p">;</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="7891743246-4">(</span><span class="nf">integer</span><span class="p" data-group-id="7891743246-5">(</span><span class="p" data-group-id="7891743246-5">)</span><span class="p" data-group-id="7891743246-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="7891743246-6">(</span><span class="p" data-group-id="7891743246-6">)</span><span class="p">.</span></code></pre><p>Type variables can be used in specifications to specify relations for the input
│ │ │  and output arguments of a function. For example, the following specification
│ │ │  defines the type of a polymorphic identity function:</p><pre><code class="text">-spec id(X) -&gt; X.</code></pre><p>Notice that the above specification does not restrict the input and output type
│ │ │  in any way. These types can be constrained by guard-like subtype constraints and
│ │ │ -provide bounded quantification:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">id</span><span class="p" data-group-id="6670135687-1">(</span><span class="n">X</span><span class="p" data-group-id="6670135687-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">tuple</span><span class="p" data-group-id="6670135687-2">(</span><span class="p" data-group-id="6670135687-2">)</span><span class="p">.</span></code></pre><p>Currently, the <code class="inline">::</code> constraint (read as &quot;is a subtype of&quot;) is the only guard
│ │ │ +provide bounded quantification:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">id</span><span class="p" data-group-id="5429792043-1">(</span><span class="n">X</span><span class="p" data-group-id="5429792043-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">tuple</span><span class="p" data-group-id="5429792043-2">(</span><span class="p" data-group-id="5429792043-2">)</span><span class="p">.</span></code></pre><p>Currently, the <code class="inline">::</code> constraint (read as &quot;is a subtype of&quot;) is the only guard
│ │ │  constraint that can be used in the <code class="inline">when</code> part of a <code class="inline">-spec</code> attribute.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The above function specification uses multiple occurrences of the same type
│ │ │  variable. That provides more type information than the following function
│ │ │ -specification, where the type variables are missing:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">id</span><span class="p" data-group-id="8654018816-1">(</span><span class="nf">tuple</span><span class="p" data-group-id="8654018816-2">(</span><span class="p" data-group-id="8654018816-2">)</span><span class="p" data-group-id="8654018816-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">tuple</span><span class="p" data-group-id="8654018816-3">(</span><span class="p" data-group-id="8654018816-3">)</span><span class="p">.</span></code></pre><p>The latter specification says that the function takes some tuple and returns
│ │ │ +specification, where the type variables are missing:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">id</span><span class="p" data-group-id="2392818980-1">(</span><span class="nf">tuple</span><span class="p" data-group-id="2392818980-2">(</span><span class="p" data-group-id="2392818980-2">)</span><span class="p" data-group-id="2392818980-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">tuple</span><span class="p" data-group-id="2392818980-3">(</span><span class="p" data-group-id="2392818980-3">)</span><span class="p">.</span></code></pre><p>The latter specification says that the function takes some tuple and returns
│ │ │  some tuple. The specification with the <code class="inline">X</code> type variable specifies that the
│ │ │  function takes a tuple and returns <em>the same</em> tuple.</p><p>However, it is up to the tools that process the specifications to choose
│ │ │  whether to take this extra information into account or not.</p></section><p>The scope of a <code class="inline">::</code> constraint is the <code class="inline">(...) -&gt; RetType</code> specification after
│ │ │  which it appears. To avoid confusion, it is suggested that different variables
│ │ │  are used in different constituents of an overloaded contract, as shown in the
│ │ │ -following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="2203416171-1">(</span><span class="p" data-group-id="2203416171-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="2203416171-3">(</span><span class="p" data-group-id="2203416171-3">)</span><span class="p" data-group-id="2203416171-2">}</span><span class="p" data-group-id="2203416171-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="2203416171-4">(</span><span class="p" data-group-id="2203416171-4">)</span><span class="p">;</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="2203416171-5">(</span><span class="p" data-group-id="2203416171-6">[</span><span class="n">Y</span><span class="p" data-group-id="2203416171-6">]</span><span class="p" data-group-id="2203416171-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="2203416171-7">(</span><span class="p" data-group-id="2203416171-7">)</span><span class="p">.</span></code></pre><p>Some functions in Erlang are not meant to return; either because they define
│ │ │ +following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="9003698141-1">(</span><span class="p" data-group-id="9003698141-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="9003698141-3">(</span><span class="p" data-group-id="9003698141-3">)</span><span class="p" data-group-id="9003698141-2">}</span><span class="p" data-group-id="9003698141-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="9003698141-4">(</span><span class="p" data-group-id="9003698141-4">)</span><span class="p">;</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="9003698141-5">(</span><span class="p" data-group-id="9003698141-6">[</span><span class="n">Y</span><span class="p" data-group-id="9003698141-6">]</span><span class="p" data-group-id="9003698141-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9003698141-7">(</span><span class="p" data-group-id="9003698141-7">)</span><span class="p">.</span></code></pre><p>Some functions in Erlang are not meant to return; either because they define
│ │ │  servers or because they are used to throw exceptions, as in the following
│ │ │ -function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">my_error</span><span class="p" data-group-id="5533586060-1">(</span><span class="n">Err</span><span class="p" data-group-id="5533586060-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="5533586060-2">(</span><span class="p" data-group-id="5533586060-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Err</span><span class="p" data-group-id="5533586060-3">}</span><span class="p" data-group-id="5533586060-2">)</span><span class="p">.</span></code></pre><p>For such functions, it is recommended to use the special <a href="../../erts-17.0/doc/html/erlang.html#t:no_return/0"><code class="inline">no_return/0</code></a> type
│ │ │ +function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">my_error</span><span class="p" data-group-id="2434934897-1">(</span><span class="n">Err</span><span class="p" data-group-id="2434934897-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="2434934897-2">(</span><span class="p" data-group-id="2434934897-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Err</span><span class="p" data-group-id="2434934897-3">}</span><span class="p" data-group-id="2434934897-2">)</span><span class="p">.</span></code></pre><p>For such functions, it is recommended to use the special <a href="../../erts-17.0/doc/html/erlang.html#t:no_return/0"><code class="inline">no_return/0</code></a> type
│ │ │  for their &quot;return&quot;, through a contract of the following form:</p><pre><code class="text">-spec my_error(term()) -&gt; no_return().</code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Erlang uses the shorthand version <code class="inline">_</code> as an anonymous type variable equivalent
│ │ │  to <a href="../../erts-17.0/doc/html/erlang.html#t:term/0"><code class="inline">term/0</code></a> or <a href="../../erts-17.0/doc/html/erlang.html#t:any/0"><code class="inline">any/0</code></a>. For example, the following function</p><pre><code class="text">-spec Function(string(), _) -&gt; string().</code></pre><p>is equivalent to:</p><pre><code class="text">-spec Function(string(), any()) -&gt; string().</code></pre></section>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/vulnerabilities.html
│ │ │ @@ -143,69 +143,69 @@
│ │ │  vulnerability (<code class="inline">affected</code>), the affected Erlang/OTP releases, namely <code class="inline">28.0</code>,
│ │ │  <code class="inline">28.0.1</code>, and <code class="inline">28.0.2</code>, and the Erlang/OTP application that was vulnerable
│ │ │  in application version <code class="inline">ssh@5.3</code>, <code class="inline">ssh@5.3.1</code>, and <code class="inline">ssh@5.3.2</code>.
│ │ │  Erlang/OTP reports the affected versions using the release and the
│ │ │  application versions because it is possible to update the application independently
│ │ │  from the release.
│ │ │  In some cases, there may be an optional action statement that describes a workaround
│ │ │ -to avoid the mentioned vulnerability.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7901202084-1">{</span><span class="w">
│ │ │ -  </span><span class="s">&quot;vulnerability&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="7901202084-2">{</span><span class="w">
│ │ │ +to avoid the mentioned vulnerability.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9782479570-1">{</span><span class="w">
│ │ │ +  </span><span class="s">&quot;vulnerability&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="9782479570-2">{</span><span class="w">
│ │ │      </span><span class="s">&quot;name&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;CVE-2025-48038&quot;</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="7901202084-2">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="9782479570-2">}</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="s">&quot;timestamp&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;2025-09-16T08:22:13.223967395Z&quot;</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="s">&quot;products&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="7901202084-3">[</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7901202084-4">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0&quot;</span><span class="w"> </span><span class="p" data-group-id="7901202084-4">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7901202084-5">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0.1&quot;</span><span class="w"> </span><span class="p" data-group-id="7901202084-5">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7901202084-6">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0.2&quot;</span><span class="w"> </span><span class="p" data-group-id="7901202084-6">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7901202084-7">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:otp/ssh@5.3&quot;</span><span class="w"> </span><span class="p" data-group-id="7901202084-7">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7901202084-8">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:otp/ssh@5.3.1&quot;</span><span class="w"> </span><span class="p" data-group-id="7901202084-8">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7901202084-9">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:otp/ssh@5.3.2&quot;</span><span class="w"> </span><span class="p" data-group-id="7901202084-9">}</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="7901202084-3">]</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="s">&quot;products&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="9782479570-3">[</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9782479570-4">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0&quot;</span><span class="w"> </span><span class="p" data-group-id="9782479570-4">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9782479570-5">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0.1&quot;</span><span class="w"> </span><span class="p" data-group-id="9782479570-5">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9782479570-6">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0.2&quot;</span><span class="w"> </span><span class="p" data-group-id="9782479570-6">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9782479570-7">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:otp/ssh@5.3&quot;</span><span class="w"> </span><span class="p" data-group-id="9782479570-7">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9782479570-8">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:otp/ssh@5.3.1&quot;</span><span class="w"> </span><span class="p" data-group-id="9782479570-8">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9782479570-9">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:otp/ssh@5.3.2&quot;</span><span class="w"> </span><span class="p" data-group-id="9782479570-9">}</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="9782479570-3">]</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="s">&quot;status&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;affected&quot;</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="s">&quot;action_statement&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;Update to any of the following versions: pkg:otp/ssh@5.3.3&quot;</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="s">&quot;action_statement_timestamp&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;2025-09-16T08:22:13.223967395Z&quot;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7901202084-1">}</span><span class="p">,</span></code></pre><p>Erlang/OTP reports the fixed version in a similar fashion as follows, in the same document.
│ │ │ +</span><span class="p" data-group-id="9782479570-1">}</span><span class="p">,</span></code></pre><p>Erlang/OTP reports the fixed version in a similar fashion as follows, in the same document.
│ │ │  As an example, there is a new statement for <code class="inline">CVE-2025-48038</code> with status <code class="inline">fixed</code>,
│ │ │  that links to the first release that do not suffer from <code class="inline">CVE-2025-48038</code>, namely
│ │ │ -OTP version <code class="inline">28.0.3</code> and application <code class="inline">ssh@5.3.3</code>. </p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4059758826-1">{</span><span class="w">
│ │ │ -  </span><span class="s">&quot;vulnerability&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="4059758826-2">{</span><span class="w">
│ │ │ +OTP version <code class="inline">28.0.3</code> and application <code class="inline">ssh@5.3.3</code>. </p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2353520798-1">{</span><span class="w">
│ │ │ +  </span><span class="s">&quot;vulnerability&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="2353520798-2">{</span><span class="w">
│ │ │      </span><span class="s">&quot;name&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;CVE-2025-48038&quot;</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="4059758826-2">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="2353520798-2">}</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="s">&quot;timestamp&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;2025-09-16T08:22:13.241103494Z&quot;</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="s">&quot;products&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="4059758826-3">[</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4059758826-4">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0.4&quot;</span><span class="w"> </span><span class="p" data-group-id="4059758826-4">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4059758826-5">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0.3&quot;</span><span class="w"> </span><span class="p" data-group-id="4059758826-5">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4059758826-6">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:otp/ssh@5.3.3&quot;</span><span class="w"> </span><span class="p" data-group-id="4059758826-6">}</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="4059758826-3">]</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="s">&quot;products&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="2353520798-3">[</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2353520798-4">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0.4&quot;</span><span class="w"> </span><span class="p" data-group-id="2353520798-4">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2353520798-5">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/erlang/otp@OTP-28.0.3&quot;</span><span class="w"> </span><span class="p" data-group-id="2353520798-5">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2353520798-6">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:otp/ssh@5.3.3&quot;</span><span class="w"> </span><span class="p" data-group-id="2353520798-6">}</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="2353520798-3">]</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="s">&quot;status&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;fixed&quot;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4059758826-1">}</span><span class="p">,</span></code></pre><h2 id="third-party-vex-statements" class="section-heading">
│ │ │ +</span><span class="p" data-group-id="2353520798-1">}</span><span class="p">,</span></code></pre><h2 id="third-party-vex-statements" class="section-heading">
│ │ │    <a href="#third-party-vex-statements" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Third Party VEX Statements</span>
│ │ │  </h2>
│ │ │  <p>Erlang/OTP generates statements for third parties from which the project depends
│ │ │  on. It is really important to understand the scope of the third party
│ │ │  applications, since Erlang/OTP vendors some libraries as part of the runtime.</p><p>Vendoring means that Erlang/OTP code contains a local copy of a library.
│ │ │  There are numerous use cases for why this is necessary, and we will not cover the use cases here.</p><p><strong>This excludes dynamically or statically linked libraries during the Erlang/OTP build process. For instance, any security related Erlang application will rely on dynamically or statically linked version of OpenSSL cryptolib.</strong></p><p>Erlang/OTP reports vulnerabilities for any source code that is vulnerable and
│ │ │  included in the Erlang/OTP release.</p><p>The OpenVEX statements for our third party libraries specify the affected/fixed
│ │ │  version using the commit SHA1 from their respective repository. This is simply
│ │ │  because our third party dependencies are in C/C++ and vulnerability scanners
│ │ │  such as OSV report vulnerabilities in SHA1 ranges.</p><p>As an example, we mention that the OpenSSL code that Erlang/OTP vendors
│ │ │ -is not susceptible for <code class="inline">CVE-2023-6129</code>, as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2449256517-1">{</span><span class="w">
│ │ │ -  </span><span class="s">&quot;vulnerability&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="2449256517-2">{</span><span class="w">
│ │ │ +is not susceptible for <code class="inline">CVE-2023-6129</code>, as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7237147652-1">{</span><span class="w">
│ │ │ +  </span><span class="s">&quot;vulnerability&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="7237147652-2">{</span><span class="w">
│ │ │      </span><span class="s">&quot;name&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;CVE-2023-6129&quot;</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="2449256517-2">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="7237147652-2">}</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="s">&quot;timestamp&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;2025-06-18T12:18:16.47247833+02:00&quot;</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="s">&quot;products&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="2449256517-3">[</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="2449256517-4">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/openssl/openssl@01d5e2318405362b4de5e670c90d9b40a351d053&quot;</span><span class="w"> </span><span class="p" data-group-id="2449256517-4">}</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="2449256517-3">]</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="s">&quot;products&quot;</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="7237147652-3">[</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="7237147652-4">{</span><span class="w"> </span><span class="s">&quot;@id&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;pkg:github/openssl/openssl@01d5e2318405362b4de5e670c90d9b40a351d053&quot;</span><span class="w"> </span><span class="p" data-group-id="7237147652-4">}</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="7237147652-3">]</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="s">&quot;status&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;not_affected&quot;</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="s">&quot;justification&quot;</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;vulnerable_code_not_present&quot;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2449256517-1">}</span></code></pre><p>Diving into the example, this means that Erlang/OTP vendors a version of <code class="inline">openssl</code> taken from commit <code class="inline">01d5e2318405362b4de5e670c90d9b40a351d053</code> from the repository <code class="inline">https://github.com/openssl/openssl/commit/01d5e2318405362b4de5e670c90d9b40a351d053</code> (version of OpenSSL 3.1.4). The <code class="inline">openssl</code> code that Erlang/OTP vendors can be found in <code class="inline">./lib/erl_interface/src/openssl/</code> and <code class="inline">./erts/emulator/openssl/</code>. The OpenVEX statement claims that the code in those folders is not susceptible to <code class="inline">CVE-2023-6129</code>. The claim is towards <strong>source code existing in Erlang/OTP</strong>.</p><p>In other words, the <code class="inline">not_affected</code> status refers to the library that Erlang/OTP vendors for OpenSSL (the library that comes
│ │ │ +</span><span class="p" data-group-id="7237147652-1">}</span></code></pre><p>Diving into the example, this means that Erlang/OTP vendors a version of <code class="inline">openssl</code> taken from commit <code class="inline">01d5e2318405362b4de5e670c90d9b40a351d053</code> from the repository <code class="inline">https://github.com/openssl/openssl/commit/01d5e2318405362b4de5e670c90d9b40a351d053</code> (version of OpenSSL 3.1.4). The <code class="inline">openssl</code> code that Erlang/OTP vendors can be found in <code class="inline">./lib/erl_interface/src/openssl/</code> and <code class="inline">./erts/emulator/openssl/</code>. The OpenVEX statement claims that the code in those folders is not susceptible to <code class="inline">CVE-2023-6129</code>. The claim is towards <strong>source code existing in Erlang/OTP</strong>.</p><p>In other words, the <code class="inline">not_affected</code> status refers to the library that Erlang/OTP vendors for OpenSSL (the library that comes
│ │ │  included with Erlang/OTP). If you build Erlang/OTP and link to any OpenSSL version (e.g., 3.5.2 or even 3.1.4) during the building process,
│ │ │  your project has now a new build and runtime dependency and may be subject to <code class="inline">CVE-2023-6129</code>.</p><h2 id="windows-binaries" class="section-heading">
│ │ │    <a href="#windows-binaries" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Windows Binaries</span>
│ │ │  </h2>
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/upcoming_incompatibilities.html
│ │ │ @@ -167,45 +167,45 @@
│ │ │  occurrences of <code class="inline">maybe</code> without quotes.</p><p><a href="" id="float_matching"></a></p><h3 id="0-0-and-0-0-will-no-longer-be-exactly-equal" class="section-heading">
│ │ │    <a href="#0-0-and-0-0-will-no-longer-be-exactly-equal" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">0.0 and -0.0 will no longer be exactly equal</span>
│ │ │  </h3>
│ │ │  <p>Currently, the floating point numbers <code class="inline">0.0</code> and <code class="inline">-0.0</code> have distinct internal
│ │ │ -representations. That can be seen if they are converted to binaries:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3481187865-1">&lt;&lt;</span><span class="mf">0.0</span><span class="o">/</span><span class="nb">float</span><span class="p" data-group-id="3481187865-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3481187865-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="3481187865-2">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="3481187865-3">&lt;&lt;</span><span class="o">-</span><span class="mf">0.0</span><span class="o">/</span><span class="nb">float</span><span class="p" data-group-id="3481187865-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3481187865-4">&lt;&lt;</span><span class="mi">128</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="3481187865-4">&gt;&gt;</span></code></pre><p>However, when they are matched against each other or compared using the <code class="inline">=:=</code>
│ │ │ +representations. That can be seen if they are converted to binaries:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4620582024-1">&lt;&lt;</span><span class="mf">0.0</span><span class="o">/</span><span class="nb">float</span><span class="p" data-group-id="4620582024-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4620582024-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="4620582024-2">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="4620582024-3">&lt;&lt;</span><span class="o">-</span><span class="mf">0.0</span><span class="o">/</span><span class="nb">float</span><span class="p" data-group-id="4620582024-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4620582024-4">&lt;&lt;</span><span class="mi">128</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="4620582024-4">&gt;&gt;</span></code></pre><p>However, when they are matched against each other or compared using the <code class="inline">=:=</code>
│ │ │  operator, they are considered to be equal. Thus, <code class="inline">0.0 =:= -0.0</code> currently
│ │ │  returns <code class="inline">true</code>.</p><p>In Erlang/OTP 27, <code class="inline">0.0 =:= -0.0</code> will return <code class="inline">false</code>, and matching <code class="inline">0.0</code> against
│ │ │  <code class="inline">-0.0</code> will fail. When used as map keys, <code class="inline">0.0</code> and <code class="inline">-0.0</code> will be considered to
│ │ │  be distinct.</p><p>The <code class="inline">==</code> operator will continue to return <code class="inline">true</code> for <code class="inline">0.0 == -0.0</code>.</p><p>To help to find code that might need to be revised, in OTP 27 there will be a
│ │ │  new compiler warning when matching against <code class="inline">0.0</code> or comparing to that value
│ │ │  using the <code class="inline">=:=</code> operator. The warning can be suppressed by matching against
│ │ │  <code class="inline">+0.0</code> instead of <code class="inline">0.0</code>.</p><p>We plan to introduce the same warning in OTP 26.1, but by default it will be
│ │ │  disabled.</p><p><a href="" id="singleton_typevars"></a></p><h3 id="singleton-type-variables-will-become-a-compile-time-error" class="section-heading">
│ │ │    <a href="#singleton-type-variables-will-become-a-compile-time-error" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Singleton type variables will become a compile-time error</span>
│ │ │  </h3>
│ │ │ -<p>Before Erlang/OTP 26, the compiler would silenty accept the following spec:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="7357953057-1">(</span><span class="n">Opts</span><span class="p" data-group-id="7357953057-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="7357953057-2">(</span><span class="p" data-group-id="7357953057-2">)</span><span class="w"> </span><span class="k">when</span><span class="w">
│ │ │ -    </span><span class="n">Opts</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="7357953057-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Unknown</span><span class="p" data-group-id="7357953057-3">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="7357953057-4">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Unknown</span><span class="p" data-group-id="7357953057-4">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="7357953057-5">(</span><span class="p">_</span><span class="p" data-group-id="7357953057-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">error</span><span class="p">.</span></code></pre><p>In OTP 26, the compiler emits a warning pointing out that the type variable
│ │ │ -<code class="inline">Unknown</code> is unbound:</p><pre><code class="makeup erlang" translate="no"><span class="ss">t</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">6</span><span class="p">:</span><span class="mi">18</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="ss">variable</span><span class="w"> </span><span class="ss">&#39;Unknown&#39;</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">only</span><span class="w"> </span><span class="ss">used</span><span class="w"> </span><span class="nf">once</span><span class="w"> </span><span class="p" data-group-id="2702311559-1">(</span><span class="ss">is</span><span class="w"> </span><span class="ss">unbound</span><span class="p" data-group-id="2702311559-1">)</span><span class="w">
│ │ │ +<p>Before Erlang/OTP 26, the compiler would silenty accept the following spec:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="7097530329-1">(</span><span class="n">Opts</span><span class="p" data-group-id="7097530329-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="7097530329-2">(</span><span class="p" data-group-id="7097530329-2">)</span><span class="w"> </span><span class="k">when</span><span class="w">
│ │ │ +    </span><span class="n">Opts</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="7097530329-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Unknown</span><span class="p" data-group-id="7097530329-3">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="7097530329-4">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Unknown</span><span class="p" data-group-id="7097530329-4">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="7097530329-5">(</span><span class="p">_</span><span class="p" data-group-id="7097530329-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">error</span><span class="p">.</span></code></pre><p>In OTP 26, the compiler emits a warning pointing out that the type variable
│ │ │ +<code class="inline">Unknown</code> is unbound:</p><pre><code class="makeup erlang" translate="no"><span class="ss">t</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">6</span><span class="p">:</span><span class="mi">18</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="ss">variable</span><span class="w"> </span><span class="ss">&#39;Unknown&#39;</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">only</span><span class="w"> </span><span class="ss">used</span><span class="w"> </span><span class="nf">once</span><span class="w"> </span><span class="p" data-group-id="5937035282-1">(</span><span class="ss">is</span><span class="w"> </span><span class="ss">unbound</span><span class="p" data-group-id="5937035282-1">)</span><span class="w">
│ │ │  </span><span class="c1">%    6|     Opts :: {ok, Unknown} | {error, Unknown}.</span><span class="w">
│ │ │  </span><span class="c1">%     |                  ^</span></code></pre><p>In OTP 27, that warning will become an error.</p><p><a href="" id="escripts_will_be_compiled"></a></p><h3 id="escripts-will-be-compiled-by-default" class="section-heading">
│ │ │    <a href="#escripts-will-be-compiled-by-default" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Escripts will be compiled by default</span>
│ │ │  </h3>
│ │ │  <p>Escripts will be compiled by default instead of interpreted. That means that the
│ │ │  <code class="inline">compiler</code> application must be available.</p><p>The old behavior of interpreting escripts can be restored by adding the
│ │ │ -following line to the script file:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">mode</span><span class="p" data-group-id="4549344520-1">(</span><span class="ss">interpret</span><span class="p" data-group-id="4549344520-1">)</span><span class="p">.</span></code></pre><p>In OTP 28, support for interpreting an escript will be removed.</p><h3 id="code_path_choice-will-default-to-strict" class="section-heading">
│ │ │ +following line to the script file:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">mode</span><span class="p" data-group-id="4597683967-1">(</span><span class="ss">interpret</span><span class="p" data-group-id="4597683967-1">)</span><span class="p">.</span></code></pre><p>In OTP 28, support for interpreting an escript will be removed.</p><h3 id="code_path_choice-will-default-to-strict" class="section-heading">
│ │ │    <a href="#code_path_choice-will-default-to-strict" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">-code_path_choice will default to strict</span>
│ │ │  </h3>
│ │ │  <p>This command line option controls if paths given in the command line, boot
│ │ │  scripts, and the code server should be interpreted as is strict or relaxed.</p><p>OTP 26 and earlier defaults to <code class="inline">relaxed</code>, which means <code class="inline">-pa myapp/ebin</code> would
│ │ │ @@ -249,18 +249,18 @@
│ │ │  &quot;
│ │ │  String Content
│ │ │  &quot;
│ │ │  %%
│ │ │  %% In OTP 27 it is instead interpreted as a
│ │ │  %% Triple-Quoted String equivalent to
│ │ │  &quot;String Content&quot;</code></pre><pre><code class="makeup erlang" translate="no"><span class="s">&quot;&quot;</span><span class="s">&quot;&quot;</span><span class="w">
│ │ │ -</span><span class="o">++</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="9582144007-1">(</span><span class="p" data-group-id="9582144007-1">)</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ +</span><span class="o">++</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="5370612735-1">(</span><span class="p" data-group-id="5370612735-1">)</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │  </span><span class="s">&quot;&quot;</span><span class="s">&quot;&quot;</span><span class="w">
│ │ │  </span><span class="c1">%% Became</span><span class="w">
│ │ │ -</span><span class="s">&quot;&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="9582144007-2">(</span><span class="p" data-group-id="9582144007-2">)</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="w">
│ │ │ +</span><span class="s">&quot;&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="5370612735-2">(</span><span class="p" data-group-id="5370612735-2">)</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │  </span><span class="c1">%% In OTP 27 it is instead interpreted as a</span><span class="w">
│ │ │  </span><span class="c1">%% Triple-Quoted String (triple-or-more) equivalent to</span><span class="w">
│ │ │  </span><span class="s">&quot;++ foo() ++&quot;</span></code></pre><p>From Erlang/OTP 26.1 up to 27.0 the compiler issues a warning for a sequence of
│ │ │  3 or more double-quote characters since that is almost certainly a mistake or
│ │ │  something like a result of bad automatic code generation. If a users gets that
│ │ │  warning, the code should be corrected for example by inserting appropriate
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-17.0/doc/html/alt_dist.html
│ │ │ @@ -237,50 +237,50 @@
│ │ │  <code class="inline">uds_dist</code> example using a port driver written in C, <code class="inline">erl_uds_dist</code> is written
│ │ │  entirely in Erlang.</p><h3 id="exported-callback-functions" class="section-heading">
│ │ │    <a href="#exported-callback-functions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Exported Callback Functions</span>
│ │ │  </h3>
│ │ │ -<p>The following functions are mandatory:</p><ul><li><pre id="listen"><code class="makeup erlang" translate="no"><span class="nf">listen</span><span class="p" data-group-id="4469091308-1">(</span><span class="n">Name</span><span class="p" data-group-id="4469091308-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="err"> </span><span class="err"> </span><span class="p" data-group-id="4469091308-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4469091308-3">{</span><span class="n">Listen</span><span class="p">,</span><span class="w"> </span><span class="n">Address</span><span class="p">,</span><span class="w"> </span><span class="n">Creation</span><span class="p" data-group-id="4469091308-3">}</span><span class="p" data-group-id="4469091308-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="4469091308-4">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="4469091308-4">}</span><span class="w">
│ │ │ -</span><span class="nf">listen</span><span class="p" data-group-id="4469091308-5">(</span><span class="n">Name</span><span class="p">,</span><span class="n">Host</span><span class="p" data-group-id="4469091308-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="err"> </span><span class="err"> </span><span class="p" data-group-id="4469091308-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4469091308-7">{</span><span class="n">Listen</span><span class="p">,</span><span class="w"> </span><span class="n">Address</span><span class="p">,</span><span class="w"> </span><span class="n">Creation</span><span class="p" data-group-id="4469091308-7">}</span><span class="p" data-group-id="4469091308-6">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="4469091308-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="4469091308-8">}</span></code></pre><p><code class="inline">listen/2</code> is called once in order to listen for incoming connection requests.
│ │ │ +<p>The following functions are mandatory:</p><ul><li><pre id="listen"><code class="makeup erlang" translate="no"><span class="nf">listen</span><span class="p" data-group-id="5775619827-1">(</span><span class="n">Name</span><span class="p" data-group-id="5775619827-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="err"> </span><span class="err"> </span><span class="p" data-group-id="5775619827-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5775619827-3">{</span><span class="n">Listen</span><span class="p">,</span><span class="w"> </span><span class="n">Address</span><span class="p">,</span><span class="w"> </span><span class="n">Creation</span><span class="p" data-group-id="5775619827-3">}</span><span class="p" data-group-id="5775619827-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="5775619827-4">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="5775619827-4">}</span><span class="w">
│ │ │ +</span><span class="nf">listen</span><span class="p" data-group-id="5775619827-5">(</span><span class="n">Name</span><span class="p">,</span><span class="n">Host</span><span class="p" data-group-id="5775619827-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="err"> </span><span class="err"> </span><span class="p" data-group-id="5775619827-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5775619827-7">{</span><span class="n">Listen</span><span class="p">,</span><span class="w"> </span><span class="n">Address</span><span class="p">,</span><span class="w"> </span><span class="n">Creation</span><span class="p" data-group-id="5775619827-7">}</span><span class="p" data-group-id="5775619827-6">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="5775619827-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="5775619827-8">}</span></code></pre><p><code class="inline">listen/2</code> is called once in order to listen for incoming connection requests.
│ │ │  The call is made when the distribution is brought up. The argument <code class="inline">Name</code> is
│ │ │  the part of the node name before the <code class="inline">@</code> sign in the full node name. It can be
│ │ │  either an atom or a string. The argument <code class="inline">Host</code> is the part of the node name
│ │ │  after the <code class="inline">@</code> sign in the full node name. It is always a string.</p><p>The return value consists of a <code class="inline">Listen</code> handle (which is later passed to the
│ │ │  <a href="alt_dist.html#accept"><code class="inline">accept/1</code></a> callback), <code class="inline">Address</code> which is a
│ │ │  <code class="inline">#net_address{}</code> record with information about the address for the node (the
│ │ │  <code class="inline">#net_address{}</code> record is defined in <code class="inline">kernel/include/net_address.hrl</code>), and
│ │ │  <code class="inline">Creation</code> which (currently) is an integer <code class="inline">1</code>, <code class="inline">2</code>, or <code class="inline">3</code>.</p><p>If <a href="epmd_cmd.html"><code class="inline">epmd</code></a> is to be used for node discovery, you typically want
│ │ │  to use the <code class="inline">erl_epmd</code> module (part of the <code class="inline">kernel</code> application) in order to
│ │ │ -register the listen port with <code class="inline">epmd</code> and retrieve <code class="inline">Creation</code> to use.</p></li><li><pre id="address"><code class="makeup erlang" translate="no"><span class="nf">address</span><span class="p" data-group-id="6073922402-1">(</span><span class="p" data-group-id="6073922402-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +register the listen port with <code class="inline">epmd</code> and retrieve <code class="inline">Creation</code> to use.</p></li><li><pre id="address"><code class="makeup erlang" translate="no"><span class="nf">address</span><span class="p" data-group-id="7719129005-1">(</span><span class="p" data-group-id="7719129005-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="err"> </span><span class="err"> </span><span class="n">Address</span></code></pre><p><code class="inline">address/0</code> is called in order to get the <code class="inline">Address</code> part of the
│ │ │  <a href="alt_dist.html#listen"><code class="inline">listen/2</code></a> function without creating a listen socket.
│ │ │ -All fields except <code class="inline">address</code> have to be set in the returned record</p><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">address</span><span class="p" data-group-id="3922830947-1">(</span><span class="p" data-group-id="3922830947-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3922830947-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Host</span><span class="p" data-group-id="3922830947-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">inet</span><span class="p">:</span><span class="nf">gethostname</span><span class="p" data-group-id="3922830947-3">(</span><span class="p" data-group-id="3922830947-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="o">#</span><span class="ss">net_address</span><span class="p" data-group-id="3922830947-4">{</span><span class="w"> </span><span class="ss">host</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Host</span><span class="p">,</span><span class="w"> </span><span class="ss">protocol</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">tcp</span><span class="p">,</span><span class="w"> </span><span class="ss">family</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">inet6</span><span class="w"> </span><span class="p" data-group-id="3922830947-4">}</span><span class="p">.</span></code></pre></li><li><pre id="accept"><code class="makeup erlang" translate="no"><span class="nf">accept</span><span class="p" data-group-id="2156003894-1">(</span><span class="n">Listen</span><span class="p" data-group-id="2156003894-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +All fields except <code class="inline">address</code> have to be set in the returned record</p><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">address</span><span class="p" data-group-id="7448733993-1">(</span><span class="p" data-group-id="7448733993-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7448733993-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Host</span><span class="p" data-group-id="7448733993-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">inet</span><span class="p">:</span><span class="nf">gethostname</span><span class="p" data-group-id="7448733993-3">(</span><span class="p" data-group-id="7448733993-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="o">#</span><span class="ss">net_address</span><span class="p" data-group-id="7448733993-4">{</span><span class="w"> </span><span class="ss">host</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Host</span><span class="p">,</span><span class="w"> </span><span class="ss">protocol</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">tcp</span><span class="p">,</span><span class="w"> </span><span class="ss">family</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">inet6</span><span class="w"> </span><span class="p" data-group-id="7448733993-4">}</span><span class="p">.</span></code></pre></li><li><pre id="accept"><code class="makeup erlang" translate="no"><span class="nf">accept</span><span class="p" data-group-id="2835161318-1">(</span><span class="n">Listen</span><span class="p" data-group-id="2835161318-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="err"> </span><span class="err"> </span><span class="n">AcceptorPid</span></code></pre><p><code class="inline">accept/1</code> should spawn a process that accepts connections. This process
│ │ │  should preferably execute on <code class="inline">max</code> priority. The process identifier of this
│ │ │  process should be returned.</p><p>The <code class="inline">Listen</code> argument will be the same as the <code class="inline">Listen</code> handle part of the
│ │ │  return value of the <a href="alt_dist.html#listen"><code class="inline">listen/1</code></a> callback above.
│ │ │  <code class="inline">accept/1</code> is called only once when the distribution protocol is started.</p><p>The caller of this function is a representative for <code class="inline">net_kernel</code> (this may or
│ │ │  may not be the process registered as <code class="inline">net_kernel</code>) and is in this document
│ │ │  identified as <code class="inline">Kernel</code>. When a connection has been accepted by the acceptor
│ │ │  process, it needs to inform <code class="inline">Kernel</code> about the accepted connection. This is
│ │ │ -done by passing a message of the form:</p><pre><code class="makeup erlang" translate="no"><span class="n">Kernel</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2192174834-1">{</span><span class="ss">accept</span><span class="p">,</span><span class="w"> </span><span class="n">AcceptorPid</span><span class="p">,</span><span class="w"> </span><span class="n">DistController</span><span class="p">,</span><span class="w"> </span><span class="n">Family</span><span class="p">,</span><span class="w"> </span><span class="n">Proto</span><span class="p" data-group-id="2192174834-1">}</span></code></pre><p><code class="inline">DistController</code> is either the process or port identifier of the distribution
│ │ │ +done by passing a message of the form:</p><pre><code class="makeup erlang" translate="no"><span class="n">Kernel</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3996116841-1">{</span><span class="ss">accept</span><span class="p">,</span><span class="w"> </span><span class="n">AcceptorPid</span><span class="p">,</span><span class="w"> </span><span class="n">DistController</span><span class="p">,</span><span class="w"> </span><span class="n">Family</span><span class="p">,</span><span class="w"> </span><span class="n">Proto</span><span class="p" data-group-id="3996116841-1">}</span></code></pre><p><code class="inline">DistController</code> is either the process or port identifier of the distribution
│ │ │  controller for the connection. The distribution controller should be created
│ │ │  by the acceptor processes when a new connection is accepted. Its job is to
│ │ │  dispatch traffic on the connection.</p><p><code class="inline">Kernel</code> responds with one of the following messages:</p><ul><li><p><strong><code class="inline">{Kernel, controller, SupervisorPid}</code></strong> - The request was accepted and
│ │ │  <code class="inline">SupervisorPid</code> is the process identifier of the connection supervisor
│ │ │  process (which is created in the
│ │ │  <a href="alt_dist.html#accept_connection"><code class="inline">accept_connection/5</code></a> callback).</p></li><li><p><strong><code class="inline">{Kernel, unsupported_protocol}</code></strong> - The request was rejected. This is a
│ │ │  fatal error. The acceptor process should terminate.</p></li></ul><p>When an accept sequence has been completed the acceptor process is expected to
│ │ │ -continue accepting further requests.</p></li><li><pre id="accept_connection"><code class="makeup erlang" translate="no"><span class="nf">accept_connection</span><span class="p" data-group-id="9869037509-1">(</span><span class="n">AcceptorPid</span><span class="p">,</span><span class="w"> </span><span class="n">DistCtrl</span><span class="p">,</span><span class="w"> </span><span class="n">MyNode</span><span class="p">,</span><span class="w"> </span><span class="n">Allowed</span><span class="p">,</span><span class="w"> </span><span class="n">SetupTime</span><span class="p" data-group-id="9869037509-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +continue accepting further requests.</p></li><li><pre id="accept_connection"><code class="makeup erlang" translate="no"><span class="nf">accept_connection</span><span class="p" data-group-id="9366221428-1">(</span><span class="n">AcceptorPid</span><span class="p">,</span><span class="w"> </span><span class="n">DistCtrl</span><span class="p">,</span><span class="w"> </span><span class="n">MyNode</span><span class="p">,</span><span class="w"> </span><span class="n">Allowed</span><span class="p">,</span><span class="w"> </span><span class="n">SetupTime</span><span class="p" data-group-id="9366221428-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="err"> </span><span class="err"> </span><span class="n">ConnectionSupervisorPid</span></code></pre><p><code class="inline">accept_connection/5</code> should spawn a process that will perform the Erlang
│ │ │  distribution handshake for the connection. If the handshake successfully
│ │ │  completes it should continue to function as a connection supervisor. This
│ │ │  process should preferably execute on <code class="inline">max</code> priority and should be linked to
│ │ │  the caller. The <code class="inline">dist_util:net_ticker_spawn_options()</code> function can be called
│ │ │  to get spawn options suitable for this process which can be passed directly to
│ │ │  <a href="erlang.html#spawn_opt/4"><code class="inline">erlang:spawn_opt/4</code></a>. <code class="inline">dist_util:net_ticker_spawn_options()</code> will by default
│ │ │ @@ -294,15 +294,15 @@
│ │ │  <code class="inline">dist_util:handshake_other_started(HsData)</code>.</p></li><li><p><strong><code class="inline">Allowed</code></strong> - To be passed along to
│ │ │  <code class="inline">dist_util:handshake_other_started(HsData)</code>.</p></li><li><p><strong><code class="inline">SetupTime</code></strong> - Time used for creating a setup timer by a call to
│ │ │  <code class="inline">dist_util:start_timer(SetupTime)</code>. The timer should be passed along to
│ │ │  <code class="inline">dist_util:handshake_other_started(HsData)</code>.</p></li></ul><p>The created process should provide callbacks and other information needed for
│ │ │  the handshake in a <a href="alt_dist.html#hs_data_record"><code class="inline">#hs_data{}</code></a> record and call
│ │ │  <code class="inline">dist_util:handshake_other_started(HsData)</code> with this record.</p><p><code class="inline">dist_util:handshake_other_started(HsData)</code> will perform the handshake and if
│ │ │  the handshake successfully completes this process will then continue in a
│ │ │ -connection supervisor loop as long as the connection is up.</p></li><li><pre id="setup"><code class="makeup erlang" translate="no"><span class="nf">setup</span><span class="p" data-group-id="2232146841-1">(</span><span class="n">Node</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">MyNode</span><span class="p">,</span><span class="w"> </span><span class="n">LongOrShortNames</span><span class="p">,</span><span class="w"> </span><span class="n">SetupTime</span><span class="p" data-group-id="2232146841-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +connection supervisor loop as long as the connection is up.</p></li><li><pre id="setup"><code class="makeup erlang" translate="no"><span class="nf">setup</span><span class="p" data-group-id="7153854235-1">(</span><span class="n">Node</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">MyNode</span><span class="p">,</span><span class="w"> </span><span class="n">LongOrShortNames</span><span class="p">,</span><span class="w"> </span><span class="n">SetupTime</span><span class="p" data-group-id="7153854235-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="err"> </span><span class="err"> </span><span class="n">ConnectionSupervisorPid</span></code></pre><p><code class="inline">setup/5</code> should spawn a process that connects to <code class="inline">Node</code>. When connection has
│ │ │  been established it should perform the Erlang distribution handshake for the
│ │ │  connection. If the handshake successfully completes it should continue to
│ │ │  function as a connection supervisor. This process should preferably execute on
│ │ │  <code class="inline">max</code> priority and should be linked to the caller. The
│ │ │  <code class="inline">dist_util:net_ticker_spawn_options()</code> function can be called to get spawn
│ │ │  options suitable for this process which can be passed directly to
│ │ │ @@ -320,23 +320,23 @@
│ │ │  may not be the process registered as <code class="inline">net_kernel</code>) and is in this document
│ │ │  identified as <code class="inline">Kernel</code>.</p><p>This function should, besides spawning the connection supervisor, also create
│ │ │  a distribution controller. The distribution controller is either a process or
│ │ │  a port which is responsible for dispatching traffic.</p><p>The created process should provide callbacks and other information needed for
│ │ │  the handshake in a <a href="alt_dist.html#hs_data_record"><code class="inline">#hs_data{}</code></a> record and call
│ │ │  <code class="inline">dist_util:handshake_we_started(HsData)</code> with this record.</p><p><code class="inline">dist_util:handshake_we_started(HsData)</code> will perform the handshake and the
│ │ │  handshake successfully completes this process will then continue in a
│ │ │ -connection supervisor loop as long as the connection is up.</p></li><li><pre id="close"><code class="makeup erlang" translate="no"><span class="nf">close</span><span class="p" data-group-id="2896610919-1">(</span><span class="n">Listen</span><span class="p" data-group-id="2896610919-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="err"> </span><span class="err"> </span><span class="nf">void</span><span class="p" data-group-id="2896610919-2">(</span><span class="p" data-group-id="2896610919-2">)</span></code></pre><p>Called in order to close the <code class="inline">Listen</code> handle that originally was passed from
│ │ │ -the <a href="alt_dist.html#listen"><code class="inline">listen/1</code></a> callback.</p></li><li><pre id="select"><code class="makeup erlang" translate="no"><span class="nf">select</span><span class="p" data-group-id="7429229665-1">(</span><span class="n">NodeName</span><span class="p" data-group-id="7429229665-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="err"> </span><span class="err"> </span><span class="nf">boolean</span><span class="p" data-group-id="7429229665-2">(</span><span class="p" data-group-id="7429229665-2">)</span></code></pre><p>Return <code class="inline">true</code> if the host name part of the <code class="inline">NodeName</code> is valid for use with
│ │ │ -this protocol; otherwise, <code class="inline">false</code>.</p></li></ul><p>There are also two optional functions that may be exported:</p><ul><li><pre id="setopts"><code class="makeup erlang" translate="no"><span class="nf">setopts</span><span class="p" data-group-id="4664987728-1">(</span><span class="n">Listen</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4664987728-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="err"> </span><span class="err"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="4664987728-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="4664987728-2">}</span></code></pre><p>The argument <code class="inline">Listen</code> is the handle originally passed from the
│ │ │ +connection supervisor loop as long as the connection is up.</p></li><li><pre id="close"><code class="makeup erlang" translate="no"><span class="nf">close</span><span class="p" data-group-id="8311576845-1">(</span><span class="n">Listen</span><span class="p" data-group-id="8311576845-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="err"> </span><span class="err"> </span><span class="nf">void</span><span class="p" data-group-id="8311576845-2">(</span><span class="p" data-group-id="8311576845-2">)</span></code></pre><p>Called in order to close the <code class="inline">Listen</code> handle that originally was passed from
│ │ │ +the <a href="alt_dist.html#listen"><code class="inline">listen/1</code></a> callback.</p></li><li><pre id="select"><code class="makeup erlang" translate="no"><span class="nf">select</span><span class="p" data-group-id="8280432881-1">(</span><span class="n">NodeName</span><span class="p" data-group-id="8280432881-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="err"> </span><span class="err"> </span><span class="nf">boolean</span><span class="p" data-group-id="8280432881-2">(</span><span class="p" data-group-id="8280432881-2">)</span></code></pre><p>Return <code class="inline">true</code> if the host name part of the <code class="inline">NodeName</code> is valid for use with
│ │ │ +this protocol; otherwise, <code class="inline">false</code>.</p></li></ul><p>There are also two optional functions that may be exported:</p><ul><li><pre id="setopts"><code class="makeup erlang" translate="no"><span class="nf">setopts</span><span class="p" data-group-id="0897074333-1">(</span><span class="n">Listen</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="0897074333-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="err"> </span><span class="err"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="0897074333-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="0897074333-2">}</span></code></pre><p>The argument <code class="inline">Listen</code> is the handle originally passed from the
│ │ │  <a href="alt_dist.html#listen"><code class="inline">listen/1</code></a> callback. The argument <code class="inline">Opts</code> is a list of
│ │ │ -options to set on future connections.</p></li><li><pre id="getopts"><code class="makeup erlang" translate="no"><span class="nf">getopts</span><span class="p" data-group-id="1062342774-1">(</span><span class="n">Listen</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="1062342774-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="err"> </span><span class="err"> </span><span class="p" data-group-id="1062342774-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">OptionValues</span><span class="p" data-group-id="1062342774-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="1062342774-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="1062342774-3">}</span></code></pre><p>The argument <code class="inline">Listen</code> is the handle originally passed from the
│ │ │ +options to set on future connections.</p></li><li><pre id="getopts"><code class="makeup erlang" translate="no"><span class="nf">getopts</span><span class="p" data-group-id="0589652689-1">(</span><span class="n">Listen</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="0589652689-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="err"> </span><span class="err"> </span><span class="p" data-group-id="0589652689-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">OptionValues</span><span class="p" data-group-id="0589652689-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="0589652689-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="0589652689-3">}</span></code></pre><p>The argument <code class="inline">Listen</code> is the handle originally passed from the
│ │ │  <a href="alt_dist.html#listen"><code class="inline">listen/1</code></a> callback. The argument <code class="inline">Opts</code> is a list of
│ │ │  options to read for future connections.</p></li></ul><p><a href="" id="hs_data_record"></a></p><h3 id="the-hs_data-record" class="section-heading">
│ │ │    <a href="#the-hs_data-record" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">The #hs_data{} Record</span>
│ │ │  </h3>
│ │ │ @@ -350,45 +350,45 @@
│ │ │  <a href="alt_dist.html#accept_connection"><code class="inline">accept_connection/5</code></a>.</p></li><li><p><strong><code class="inline" id="hs_data_other_node">other_node</code></strong> - Name of the other node. This field
│ │ │  is only mandatory when this node initiates the connection. That is, when
│ │ │  connection is set up via <a href="alt_dist.html#setup"><code class="inline">setup/5</code></a>.</p></li><li><p><strong><code class="inline" id="hs_data_this_node">this_node</code></strong> - The node name of this node.</p></li><li><p><strong><code class="inline" id="hs_data_socket">socket</code></strong> - The identifier of the distribution
│ │ │  controller.</p></li><li><p><strong><code class="inline" id="hs_data_timer">timer</code></strong> - The timer created using
│ │ │  <code class="inline">dist_util:start_timer/1</code>.</p></li><li><p><strong><code class="inline" id="hs_data_allowed">allowed</code></strong> - Information passed as <code class="inline">Allowed</code> to
│ │ │  <code class="inline">accept_connection/5</code>. This field is only mandatory when the remote node
│ │ │  initiated the connection. That is, when the connection is set up via
│ │ │ -<a href="alt_dist.html#accept_connection"><code class="inline">accept_connection/5</code></a>.</p></li><li><p><strong><code class="inline" id="hs_data_f_send">f_send</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="0905834432-1">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0905834432-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="0905834432-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="0905834432-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller and <code class="inline">Data</code>
│ │ │ -is io data to pass to the other side.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_f_recv">f_recv</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="2971790244-1">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">Timeout</span><span class="p" data-group-id="2971790244-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2971790244-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Packet</span><span class="p" data-group-id="2971790244-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="2971790244-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="2971790244-3">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller. If
│ │ │ +<a href="alt_dist.html#accept_connection"><code class="inline">accept_connection/5</code></a>.</p></li><li><p><strong><code class="inline" id="hs_data_f_send">f_send</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5750202885-1">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5750202885-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="5750202885-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="5750202885-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller and <code class="inline">Data</code>
│ │ │ +is io data to pass to the other side.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_f_recv">f_recv</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8280207140-1">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">Timeout</span><span class="p" data-group-id="8280207140-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8280207140-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Packet</span><span class="p" data-group-id="8280207140-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="8280207140-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="8280207140-3">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller. If
│ │ │  <code class="inline">Length</code> is <code class="inline">0</code>, all available bytes should be returned. If <code class="inline">Length &gt; 0</code>,
│ │ │  exactly <code class="inline">Length</code> bytes should be returned, or an error; possibly discarding
│ │ │  less than <code class="inline">Length</code> bytes of data when the connection is closed from the other
│ │ │  side. It is used for passive receive of data from the other end.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_f_setopts_pre_nodeup">f_setopts_pre_nodeup</code></strong> - A fun with the
│ │ │ -following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="7073329141-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="7073329141-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="7073329141-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="7073329141-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller. Called
│ │ │ +following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="9027785037-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="9027785037-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="9027785037-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="9027785037-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller. Called
│ │ │  just before the distribution channel is taken up for normal traffic.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_f_setopts_post_nodeup">f_setopts_post_nodeup</code></strong> - A fun with
│ │ │ -the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="7945174506-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="7945174506-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="7945174506-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="7945174506-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller. Called
│ │ │ -just after distribution channel has been taken up for normal traffic.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_f_getll">f_getll</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="6502103006-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="6502103006-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">ID</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller and <code class="inline">ID</code> is
│ │ │ +the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="1142295271-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="1142295271-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="1142295271-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="1142295271-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller. Called
│ │ │ +just after distribution channel has been taken up for normal traffic.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_f_getll">f_getll</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="7969116922-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="7969116922-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">ID</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller and <code class="inline">ID</code> is
│ │ │  the identifier of the low level entity that handles the connection (often
│ │ │ -<code class="inline">DistCtrlr</code> itself).</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_f_address">f_address</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="4570202706-1">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="4570202706-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">NetAddress</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller, <code class="inline">Node</code> is
│ │ │ +<code class="inline">DistCtrlr</code> itself).</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_f_address">f_address</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="2886242603-1">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="2886242603-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">NetAddress</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller, <code class="inline">Node</code> is
│ │ │  the node name of the node on the other end, and <code class="inline">NetAddress</code> is a
│ │ │  <code class="inline">#net_address{}</code> record with information about the address for the <code class="inline">Node</code> on
│ │ │  the other end of the connection. The <code class="inline">#net_address{}</code> record is defined in
│ │ │ -<code class="inline">kernel/include/net_address.hrl</code>.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_mf_tick">mf_tick</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="1296817942-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="1296817942-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">void</span><span class="p" data-group-id="1296817942-2">(</span><span class="p" data-group-id="1296817942-2">)</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller. This
│ │ │ +<code class="inline">kernel/include/net_address.hrl</code>.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_mf_tick">mf_tick</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8645365884-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="8645365884-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">void</span><span class="p" data-group-id="8645365884-2">(</span><span class="p" data-group-id="8645365884-2">)</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller. This
│ │ │  function should send information over the connection that is not interpreted
│ │ │  by the other end while increasing the statistics of received packets on the
│ │ │  other end. This is usually implemented by sending an empty packet.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>It is of vital importance that this operation does not block the caller for
│ │ │ -a long time. This since it is called from the connection supervisor.</p></section><p>Used when connection is up.</p></li><li><p><strong><code class="inline" id="hs_data_mf_getstat">mf_getstat</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="0130027757-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="0130027757-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0130027757-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Received</span><span class="p">,</span><span class="w"> </span><span class="n">Sent</span><span class="p">,</span><span class="w"> </span><span class="n">PendSend</span><span class="p" data-group-id="0130027757-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller, <code class="inline">Received</code>
│ │ │ +a long time. This since it is called from the connection supervisor.</p></section><p>Used when connection is up.</p></li><li><p><strong><code class="inline" id="hs_data_mf_getstat">mf_getstat</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5184052998-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="5184052998-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5184052998-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Received</span><span class="p">,</span><span class="w"> </span><span class="n">Sent</span><span class="p">,</span><span class="w"> </span><span class="n">PendSend</span><span class="p" data-group-id="5184052998-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller, <code class="inline">Received</code>
│ │ │  is received packets, <code class="inline">Sent</code> is sent packets, and <code class="inline">PendSend</code> is amount of data
│ │ │  in queue to be sent (typically in bytes, but <code class="inline">dist_util</code> only checks whether
│ │ │  the value is non-zero to know there is data in queue) or a <a href="erlang.html#t:boolean/0"><code class="inline">boolean/0</code></a>
│ │ │  indicating whether there are packets in queue to be sent.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>It is of vital importance that this operation does not block the caller for
│ │ │  a long time. This since it is called from the connection supervisor.</p></section><p>Used when connection is up.</p></li><li><p><strong><code class="inline" id="hs_data_request_type">request_type</code></strong> - The request <code class="inline">Type</code> as passed to
│ │ │  <a href="alt_dist.html#setup"><code class="inline">setup/5</code></a>. This is only mandatory when the connection has
│ │ │ -been initiated by this node. That is, the connection is set up via <code class="inline">setup/5</code>.</p></li><li><p><strong><code class="inline" id="hs_data_mf_setopts">mf_setopts</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8410942047-1">(</span><span class="n">DistCtrl</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="8410942047-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="8410942047-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="8410942047-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller and <code class="inline">Opts</code>
│ │ │ -is a list of options to set on the connection.</p><p>This function is optional. Used when connection is up.</p></li><li><p><strong><code class="inline" id="hs_data_mf_getopts">mf_getopts</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8151493218-1">(</span><span class="n">DistCtrl</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="8151493218-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8151493218-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">OptionValues</span><span class="p" data-group-id="8151493218-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="8151493218-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="8151493218-3">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller and <code class="inline">Opts</code>
│ │ │ +been initiated by this node. That is, the connection is set up via <code class="inline">setup/5</code>.</p></li><li><p><strong><code class="inline" id="hs_data_mf_setopts">mf_setopts</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5299900786-1">(</span><span class="n">DistCtrl</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="5299900786-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="5299900786-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="5299900786-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller and <code class="inline">Opts</code>
│ │ │ +is a list of options to set on the connection.</p><p>This function is optional. Used when connection is up.</p></li><li><p><strong><code class="inline" id="hs_data_mf_getopts">mf_getopts</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="9653640544-1">(</span><span class="n">DistCtrl</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="9653640544-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9653640544-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">OptionValues</span><span class="p" data-group-id="9653640544-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="9653640544-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="9653640544-3">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller and <code class="inline">Opts</code>
│ │ │  is a list of options to read for the connection.</p><p>This function is optional. Used when connection is up.</p></li><li><p><strong><code class="inline" id="hs_data_f_handshake_complete">f_handshake_complete</code></strong> - A fun with the
│ │ │ -following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8253970541-1">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p">,</span><span class="w"> </span><span class="n">DHandle</span><span class="p" data-group-id="8253970541-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">void</span><span class="p" data-group-id="8253970541-2">(</span><span class="p" data-group-id="8253970541-2">)</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │ -</span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8253970541-3">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p">,</span><span class="w"> </span><span class="n">DHandle</span><span class="p">,</span><span class="w"> </span><span class="n">Context</span><span class="p" data-group-id="8253970541-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">void</span><span class="p" data-group-id="8253970541-4">(</span><span class="p" data-group-id="8253970541-4">)</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller, <code class="inline">Node</code> is
│ │ │ +following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5147717194-1">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p">,</span><span class="w"> </span><span class="n">DHandle</span><span class="p" data-group-id="5147717194-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">void</span><span class="p" data-group-id="5147717194-2">(</span><span class="p" data-group-id="5147717194-2">)</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │ +</span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5147717194-3">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p">,</span><span class="w"> </span><span class="n">DHandle</span><span class="p">,</span><span class="w"> </span><span class="n">Context</span><span class="p" data-group-id="5147717194-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">void</span><span class="p" data-group-id="5147717194-4">(</span><span class="p" data-group-id="5147717194-4">)</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller, <code class="inline">Node</code> is
│ │ │  the node name of the node connected at the other end. <code class="inline">Context</code> is a map of
│ │ │  <code class="inline">#{creation =&gt; Creation, flags =&gt; Flags}</code>, and <code class="inline">Creation</code> / <code class="inline">Flags</code> are the
│ │ │  node incarnation identifier / <a href="erl_dist_protocol.html#dflags">capability flags</a>
│ │ │  of the node connected at the other end. <code class="inline">DHandle</code> is a distribution handle
│ │ │  needed by a distribution controller process when calling the following BIFs:</p><ul><li><a href="erlang.html#dist_ctrl_get_data/1"><code class="inline">erlang:dist_ctrl_get_data/1</code></a></li><li><a href="erlang.html#dist_ctrl_get_data_notification/1"><code class="inline">erlang:dist_ctrl_get_data_notification/1</code></a></li><li><a href="erlang.html#dist_ctrl_input_handler/2"><code class="inline">erlang:dist_ctrl_input_handler/2</code></a></li><li><a href="erlang.html#dist_ctrl_put_data/2"><code class="inline">erlang:dist_ctrl_put_data/2</code></a></li></ul><p>This function is called when the handshake has completed and the distribution
│ │ │  channel is up. The distribution controller can begin dispatching traffic over
│ │ │  the channel. This function is optional.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_add_flags">add_flags</code></strong> -
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-17.0/doc/html/automaticyieldingofccode.html
│ │ │ @@ -209,17 +209,17 @@
│ │ │  they have to follow certain restrictions. The convention for making
│ │ │  this clear is to have a comment above the function that explains that
│ │ │  the function is transformed by YCF (see <code class="inline">maps_values_1_helper</code> in
│ │ │  <code class="inline">erl_map.c</code> for an example). If only the transformed version of the
│ │ │  function is used, the convention is to &quot;comment out&quot; the source for the
│ │ │  function by surrounding it with the following <code class="inline">#ifdef</code> (this way, one
│ │ │  will not get warnings about unused functions):</p><pre><code class="makeup erlang" translate="no"><span class="p">#</span><span class="ss">ifdef</span><span class="w"> </span><span class="n">INCLUDE_YCF_TRANSFORMED_ONLY_FUNCTIONS</span><span class="w">
│ │ │ -</span><span class="ss">void</span><span class="w"> </span><span class="nf">my_fun</span><span class="p" data-group-id="3307941010-1">(</span><span class="p" data-group-id="3307941010-1">)</span><span class="w"> </span><span class="p" data-group-id="3307941010-2">{</span><span class="w">
│ │ │ +</span><span class="ss">void</span><span class="w"> </span><span class="nf">my_fun</span><span class="p" data-group-id="9229782294-1">(</span><span class="p" data-group-id="9229782294-1">)</span><span class="w"> </span><span class="p" data-group-id="9229782294-2">{</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3307941010-2">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9229782294-2">}</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="ss">endif</span><span class="w"> </span><span class="o">/</span><span class="o">*</span><span class="w"> </span><span class="n">INCLUDE_YCF_TRANSFORMED_ONLY_FUNCTIONS</span><span class="w"> </span><span class="o">*</span><span class="o">/</span></code></pre><p>While editing the function one can define
│ │ │  <code class="inline">INCLUDE_YCF_TRANSFORMED_ONLY_FUNCTIONS</code> so that one can see errors
│ │ │  and warnings in the non-transformed source.</p><h3 id="where-to-place-ycf-transformed-functions" class="section-heading">
│ │ │    <a href="#where-to-place-ycf-transformed-functions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Where to Place YCF Transformed Functions</span>
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-17.0/doc/html/beam_makeops.html
│ │ │ @@ -151,17 +151,17 @@
│ │ │  The loader translates generic instructions to specific instructions.
│ │ │  In general, for each generic instruction, there exists a family of
│ │ │  specific instructions.  The OTP 20 release has 389 specific
│ │ │  instructions.</p></li><li><p>The implementation of specific instructions for the traditional
│ │ │  BEAM interpreter. For the <a href="beamasm.html">BeamAsm JIT</a> introduced
│ │ │  in OTP 24, the implementation of instructions are defined in emitter
│ │ │  functions written in C++.</p></li></ul><p>Generic instructions have typed operands. Here are a few examples of
│ │ │ -operands for <code class="inline">move/2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6487382858-1">{</span><span class="ss">move</span><span class="p">,</span><span class="p" data-group-id="6487382858-2">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">id</span><span class="p" data-group-id="6487382858-2">}</span><span class="p">,</span><span class="p" data-group-id="6487382858-3">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="6487382858-3">}</span><span class="p" data-group-id="6487382858-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6487382858-4">{</span><span class="ss">move</span><span class="p">,</span><span class="p" data-group-id="6487382858-5">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6487382858-5">}</span><span class="p">,</span><span class="p" data-group-id="6487382858-6">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="6487382858-6">}</span><span class="p" data-group-id="6487382858-4">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6487382858-7">{</span><span class="ss">move</span><span class="p">,</span><span class="p" data-group-id="6487382858-8">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6487382858-8">}</span><span class="p">,</span><span class="p" data-group-id="6487382858-9">{</span><span class="ss">y</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6487382858-9">}</span><span class="p" data-group-id="6487382858-7">}</span><span class="p">.</span></code></pre><p>When those instructions are loaded, the loader rewrites them
│ │ │ +operands for <code class="inline">move/2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2371327258-1">{</span><span class="ss">move</span><span class="p">,</span><span class="p" data-group-id="2371327258-2">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">id</span><span class="p" data-group-id="2371327258-2">}</span><span class="p">,</span><span class="p" data-group-id="2371327258-3">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="2371327258-3">}</span><span class="p" data-group-id="2371327258-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2371327258-4">{</span><span class="ss">move</span><span class="p">,</span><span class="p" data-group-id="2371327258-5">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2371327258-5">}</span><span class="p">,</span><span class="p" data-group-id="2371327258-6">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="2371327258-6">}</span><span class="p" data-group-id="2371327258-4">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2371327258-7">{</span><span class="ss">move</span><span class="p">,</span><span class="p" data-group-id="2371327258-8">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2371327258-8">}</span><span class="p">,</span><span class="p" data-group-id="2371327258-9">{</span><span class="ss">y</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2371327258-9">}</span><span class="p" data-group-id="2371327258-7">}</span><span class="p">.</span></code></pre><p>When those instructions are loaded, the loader rewrites them
│ │ │  to specific instructions:</p><pre><code class="makeup erlang" translate="no"><span class="ss">move_cx</span><span class="w"> </span><span class="ss">id</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │  </span><span class="ss">move_xx</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="mi">0</span><span class="w">
│ │ │  </span><span class="ss">move_xy</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="mi">1</span></code></pre><p>Corresponding to each generic instruction, there is a family of
│ │ │  specific instructions.  The types that an instance of a specific
│ │ │  instruction can handle are encoded in the instruction names.  For
│ │ │  example, <code class="inline">move_xy</code> takes an X register number as the first operand and
│ │ │  a Y register number as the second operand.  <code class="inline">move_cx</code> takes a tagged
│ │ │ @@ -185,17 +185,17 @@
│ │ │  </span><span class="ss">move</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="ss">x</span></code></pre><p>Each specific instructions is defined by following the name of the
│ │ │  instruction with the types for each operand.  An operand type is a
│ │ │  single letter.  For example, <code class="inline">x</code> means an X register, <code class="inline">y</code>
│ │ │  means a Y register, and <code class="inline">c</code> is a &quot;constant&quot; (a tagged term such as
│ │ │  an integer, an atom, or a literal).</p><p>Now let's look at the implementation of the <code class="inline">move</code> instruction.  There
│ │ │  are multiple files containing implementations of instructions in the
│ │ │  <code class="inline">erts/emulator/beam/emu</code> directory.  The <code class="inline">move</code> instruction is defined
│ │ │ -in <code class="inline">instrs.tab</code>.  It looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">move</span><span class="p" data-group-id="5951638611-1">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="5951638611-1">)</span><span class="w"> </span><span class="p" data-group-id="5951638611-2">{</span><span class="w">
│ │ │ +in <code class="inline">instrs.tab</code>.  It looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">move</span><span class="p" data-group-id="8806070037-1">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="8806070037-1">)</span><span class="w"> </span><span class="p" data-group-id="8806070037-2">{</span><span class="w">
│ │ │      </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">rc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5951638611-2">}</span></code></pre><p>The implementation for an instruction largely follows the C syntax,
│ │ │ +</span><span class="p" data-group-id="8806070037-2">}</span></code></pre><p>The implementation for an instruction largely follows the C syntax,
│ │ │  except that the variables in the function head don't have any types.
│ │ │  The <code class="inline">$</code> before an identifier denotes a macro expansion.  Thus,
│ │ │  <code class="inline">$Src</code> will expand to the code to pick up the source operand for
│ │ │  the instruction and <code class="inline">$Dst</code> to the code for the destination register.</p><p>We will look at the code for each specific instruction in turn.  To
│ │ │  make the code easier to understand, let's first look at the memory
│ │ │  layout for the instruction <code class="inline">{move,{atom,id},{x,5}}</code>:</p><pre><code class="makeup erlang" translate="no"><span class="w">     </span><span class="o">+</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">+</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">+</span><span class="w">
│ │ │  </span><span class="n">I</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">|</span><span class="w">                 </span><span class="mi">40</span><span class="w"> </span><span class="p">|</span><span class="w">       </span><span class="p">&amp;&amp;</span><span class="ss">lb_move_cx</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │ @@ -204,61 +204,61 @@
│ │ │       </span><span class="o">+</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">+</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">+</span></code></pre><p>This example and all other examples in the document assumes a 64-bit
│ │ │  architecture, and furthermore that pointers to C code fit in 32 bits.</p><p><code class="inline">I</code> in the BEAM virtual machine is the instruction pointer.  When BEAM
│ │ │  executes an instruction, <code class="inline">I</code> points to the first word of the
│ │ │  instruction.</p><p><code class="inline">&amp;&amp;lb_move_cx</code> is the address to C code that implements <code class="inline">move_cx</code>.  It
│ │ │  is stored in the lower 32 bits of the word.  In the upper 32 bits is
│ │ │  the byte offset to the X register; the register number 5 has been
│ │ │  multiplied by the word size size 8.</p><p>In the next word the tagged atom <code class="inline">id</code> is stored.</p><p>With that background, we can look at the generated code for <code class="inline">move_cx</code>
│ │ │ -in <code class="inline">beam_hot.h</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="6479464565-1">(</span><span class="ss">move_cx</span><span class="p" data-group-id="6479464565-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6479464565-2">{</span><span class="w">
│ │ │ -  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="6479464565-3">(</span><span class="n">I</span><span class="p" data-group-id="6479464565-4">[</span><span class="mi">2</span><span class="p" data-group-id="6479464565-4">]</span><span class="p" data-group-id="6479464565-3">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="nf">xb</span><span class="p" data-group-id="6479464565-5">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="6479464565-6">(</span><span class="n">I</span><span class="p" data-group-id="6479464565-7">[</span><span class="mi">0</span><span class="p" data-group-id="6479464565-7">]</span><span class="p" data-group-id="6479464565-6">)</span><span class="p" data-group-id="6479464565-5">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="6479464565-8">[</span><span class="mi">1</span><span class="p" data-group-id="6479464565-8">]</span><span class="p">;</span><span class="w">
│ │ │ +in <code class="inline">beam_hot.h</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="4977457658-1">(</span><span class="ss">move_cx</span><span class="p" data-group-id="4977457658-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4977457658-2">{</span><span class="w">
│ │ │ +  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="4977457658-3">(</span><span class="n">I</span><span class="p" data-group-id="4977457658-4">[</span><span class="mi">2</span><span class="p" data-group-id="4977457658-4">]</span><span class="p" data-group-id="4977457658-3">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="nf">xb</span><span class="p" data-group-id="4977457658-5">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="4977457658-6">(</span><span class="n">I</span><span class="p" data-group-id="4977457658-7">[</span><span class="mi">0</span><span class="p" data-group-id="4977457658-7">]</span><span class="p" data-group-id="4977457658-6">)</span><span class="p" data-group-id="4977457658-5">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="4977457658-8">[</span><span class="mi">1</span><span class="p" data-group-id="4977457658-8">]</span><span class="p">;</span><span class="w">
│ │ │    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="6479464565-9">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="6479464565-10">(</span><span class="ss">next_pf</span><span class="p" data-group-id="6479464565-10">)</span><span class="p" data-group-id="6479464565-9">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">GotoPF</span><span class="p" data-group-id="6479464565-11">(</span><span class="ss">next_pf</span><span class="p" data-group-id="6479464565-11">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6479464565-2">}</span></code></pre><p>We will go through each line in turn.</p><ul><li><p><code class="inline">OpCase(move_cx):</code> defines a label for the instruction.  The
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="4977457658-9">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="4977457658-10">(</span><span class="ss">next_pf</span><span class="p" data-group-id="4977457658-10">)</span><span class="p" data-group-id="4977457658-9">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">GotoPF</span><span class="p" data-group-id="4977457658-11">(</span><span class="ss">next_pf</span><span class="p" data-group-id="4977457658-11">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4977457658-2">}</span></code></pre><p>We will go through each line in turn.</p><ul><li><p><code class="inline">OpCase(move_cx):</code> defines a label for the instruction.  The
│ │ │  <code class="inline">OpCase()</code> macro is defined in <code class="inline">beam_emu.c</code>.  It will expand this line
│ │ │  to <code class="inline">lb_move_cx:</code>.</p></li><li><p><code class="inline">BeamInstr next_pf = BeamCodeAddr(I[2]);</code> fetches the pointer to
│ │ │  code for the next instruction to be executed.  The <code class="inline">BeamCodeAddr()</code>
│ │ │  macro extracts the pointer from the lower 32 bits of the instruction
│ │ │  word.</p></li><li><p><code class="inline">xb(BeamExtraData(I[0])) = I[1];</code> is the expansion of <code class="inline">$Dst = $Src</code>.
│ │ │  <code class="inline">BeamExtraData()</code> is a macro that will extract the upper 32 bits from
│ │ │  the instruction word.  In this example, it will return 40 which is the
│ │ │  byte offset for X register 5.  The <code class="inline">xb()</code> macro will cast a byte
│ │ │  pointer to an <code class="inline">Eterm</code> pointer and dereference it.  The <code class="inline">I[1]</code> on
│ │ │  the right-hand side of the <code class="inline">=</code> fetches an Erlang term (the atom <code class="inline">id</code> in
│ │ │  this case).</p></li><li><p><code class="inline">I += 2</code> advances the instruction pointer to the next
│ │ │  instruction.</p></li><li><p>In a debug-compiled emulator, <code class="inline">ASSERT(VALID_INSTR(next_pf));</code> makes
│ │ │  sure that <code class="inline">next_pf</code> is a valid instruction (that is, that it points
│ │ │ -within the <code class="inline">process_main()</code> function in <code class="inline">beam_emu.c</code>).</p></li><li><p><code class="inline">GotoPF(next_pf);</code> transfers control to the next instruction.</p></li></ul><p>Now let's look at the implementation of <code class="inline">move_xx</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="8805095586-1">(</span><span class="ss">move_xx</span><span class="p" data-group-id="8805095586-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8805095586-2">{</span><span class="w">
│ │ │ -  </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">tmp_packed1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamExtraData</span><span class="p" data-group-id="8805095586-3">(</span><span class="n">I</span><span class="p" data-group-id="8805095586-4">[</span><span class="mi">0</span><span class="p" data-group-id="8805095586-4">]</span><span class="p" data-group-id="8805095586-3">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="8805095586-5">(</span><span class="n">I</span><span class="p" data-group-id="8805095586-6">[</span><span class="mi">1</span><span class="p" data-group-id="8805095586-6">]</span><span class="p" data-group-id="8805095586-5">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="nf">xb</span><span class="p" data-group-id="8805095586-7">(</span><span class="p" data-group-id="8805095586-8">(</span><span class="ss">tmp_packed1</span><span class="p">&gt;&gt;</span><span class="n">BEAM_TIGHT_SHIFT</span><span class="p" data-group-id="8805095586-8">)</span><span class="p" data-group-id="8805095586-7">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">xb</span><span class="p" data-group-id="8805095586-9">(</span><span class="ss">tmp_packed1</span><span class="err">&amp;</span><span class="n">BEAM_TIGHT_MASK</span><span class="p" data-group-id="8805095586-9">)</span><span class="p">;</span><span class="w">
│ │ │ +within the <code class="inline">process_main()</code> function in <code class="inline">beam_emu.c</code>).</p></li><li><p><code class="inline">GotoPF(next_pf);</code> transfers control to the next instruction.</p></li></ul><p>Now let's look at the implementation of <code class="inline">move_xx</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="9202191067-1">(</span><span class="ss">move_xx</span><span class="p" data-group-id="9202191067-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9202191067-2">{</span><span class="w">
│ │ │ +  </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">tmp_packed1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamExtraData</span><span class="p" data-group-id="9202191067-3">(</span><span class="n">I</span><span class="p" data-group-id="9202191067-4">[</span><span class="mi">0</span><span class="p" data-group-id="9202191067-4">]</span><span class="p" data-group-id="9202191067-3">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="9202191067-5">(</span><span class="n">I</span><span class="p" data-group-id="9202191067-6">[</span><span class="mi">1</span><span class="p" data-group-id="9202191067-6">]</span><span class="p" data-group-id="9202191067-5">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="nf">xb</span><span class="p" data-group-id="9202191067-7">(</span><span class="p" data-group-id="9202191067-8">(</span><span class="ss">tmp_packed1</span><span class="p">&gt;&gt;</span><span class="n">BEAM_TIGHT_SHIFT</span><span class="p" data-group-id="9202191067-8">)</span><span class="p" data-group-id="9202191067-7">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">xb</span><span class="p" data-group-id="9202191067-9">(</span><span class="ss">tmp_packed1</span><span class="err">&amp;</span><span class="n">BEAM_TIGHT_MASK</span><span class="p" data-group-id="9202191067-9">)</span><span class="p">;</span><span class="w">
│ │ │    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="8805095586-10">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="8805095586-11">(</span><span class="ss">next_pf</span><span class="p" data-group-id="8805095586-11">)</span><span class="p" data-group-id="8805095586-10">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">GotoPF</span><span class="p" data-group-id="8805095586-12">(</span><span class="ss">next_pf</span><span class="p" data-group-id="8805095586-12">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8805095586-2">}</span></code></pre><p>We will go through the lines that are new or have changed compared to
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="9202191067-10">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="9202191067-11">(</span><span class="ss">next_pf</span><span class="p" data-group-id="9202191067-11">)</span><span class="p" data-group-id="9202191067-10">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">GotoPF</span><span class="p" data-group-id="9202191067-12">(</span><span class="ss">next_pf</span><span class="p" data-group-id="9202191067-12">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9202191067-2">}</span></code></pre><p>We will go through the lines that are new or have changed compared to
│ │ │  <code class="inline">move_cx</code>.</p><ul><li><p><code class="inline">Eterm tmp_packed1 = BeamExtraData(I[0]);</code> picks up both X register
│ │ │  numbers packed into the upper 32 bits of the instruction word.</p></li><li><p><code class="inline">BeamInstr next_pf = BeamCodeAddr(I[1]);</code> pre-fetches the address of
│ │ │  the next instruction. Note that because both X registers operands fits
│ │ │  into the instruction word, the next instruction is in the very next
│ │ │  word.</p></li><li><p><code class="inline">xb((tmp_packed1&gt;&gt;BEAM_TIGHT_SHIFT)) = xb(tmp_packed1&amp;BEAM_TIGHT_MASK);</code>
│ │ │  copies the source to the destination.  (For a 64-bit architecture,
│ │ │  <code class="inline">BEAM_TIGHT_SHIFT</code> is 16 and <code class="inline">BEAM_TIGHT_MASK</code> is <code class="inline">0xFFFF</code>.)</p></li><li><p><code class="inline">I += 1;</code> advances the instruction pointer to the next instruction.</p></li></ul><p><code class="inline">move_xy</code> is almost identical to <code class="inline">move_xx</code>.  The only difference is
│ │ │  the use of the <code class="inline">yb()</code> macro instead of <code class="inline">xb()</code> to reference the
│ │ │ -destination register:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="9415995162-1">(</span><span class="ss">move_xy</span><span class="p" data-group-id="9415995162-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9415995162-2">{</span><span class="w">
│ │ │ -  </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">tmp_packed1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamExtraData</span><span class="p" data-group-id="9415995162-3">(</span><span class="n">I</span><span class="p" data-group-id="9415995162-4">[</span><span class="mi">0</span><span class="p" data-group-id="9415995162-4">]</span><span class="p" data-group-id="9415995162-3">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="9415995162-5">(</span><span class="n">I</span><span class="p" data-group-id="9415995162-6">[</span><span class="mi">1</span><span class="p" data-group-id="9415995162-6">]</span><span class="p" data-group-id="9415995162-5">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="nf">yb</span><span class="p" data-group-id="9415995162-7">(</span><span class="p" data-group-id="9415995162-8">(</span><span class="ss">tmp_packed1</span><span class="p">&gt;&gt;</span><span class="n">BEAM_TIGHT_SHIFT</span><span class="p" data-group-id="9415995162-8">)</span><span class="p" data-group-id="9415995162-7">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">xb</span><span class="p" data-group-id="9415995162-9">(</span><span class="ss">tmp_packed1</span><span class="err">&amp;</span><span class="n">BEAM_TIGHT_MASK</span><span class="p" data-group-id="9415995162-9">)</span><span class="p">;</span><span class="w">
│ │ │ +destination register:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="1437651315-1">(</span><span class="ss">move_xy</span><span class="p" data-group-id="1437651315-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1437651315-2">{</span><span class="w">
│ │ │ +  </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">tmp_packed1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamExtraData</span><span class="p" data-group-id="1437651315-3">(</span><span class="n">I</span><span class="p" data-group-id="1437651315-4">[</span><span class="mi">0</span><span class="p" data-group-id="1437651315-4">]</span><span class="p" data-group-id="1437651315-3">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="1437651315-5">(</span><span class="n">I</span><span class="p" data-group-id="1437651315-6">[</span><span class="mi">1</span><span class="p" data-group-id="1437651315-6">]</span><span class="p" data-group-id="1437651315-5">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="nf">yb</span><span class="p" data-group-id="1437651315-7">(</span><span class="p" data-group-id="1437651315-8">(</span><span class="ss">tmp_packed1</span><span class="p">&gt;&gt;</span><span class="n">BEAM_TIGHT_SHIFT</span><span class="p" data-group-id="1437651315-8">)</span><span class="p" data-group-id="1437651315-7">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">xb</span><span class="p" data-group-id="1437651315-9">(</span><span class="ss">tmp_packed1</span><span class="err">&amp;</span><span class="n">BEAM_TIGHT_MASK</span><span class="p" data-group-id="1437651315-9">)</span><span class="p">;</span><span class="w">
│ │ │    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="9415995162-10">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="9415995162-11">(</span><span class="ss">next_pf</span><span class="p" data-group-id="9415995162-11">)</span><span class="p" data-group-id="9415995162-10">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">GotoPF</span><span class="p" data-group-id="9415995162-12">(</span><span class="ss">next_pf</span><span class="p" data-group-id="9415995162-12">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9415995162-2">}</span></code></pre><h3 id="transformation-rules" class="section-heading">
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="1437651315-10">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="1437651315-11">(</span><span class="ss">next_pf</span><span class="p" data-group-id="1437651315-11">)</span><span class="p" data-group-id="1437651315-10">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">GotoPF</span><span class="p" data-group-id="1437651315-12">(</span><span class="ss">next_pf</span><span class="p" data-group-id="1437651315-12">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1437651315-2">}</span></code></pre><h3 id="transformation-rules" class="section-heading">
│ │ │    <a href="#transformation-rules" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Transformation rules</span>
│ │ │  </h3>
│ │ │  <p>Next let's look at how we can do some optimizations using transformation
│ │ │  rules.  For simple instructions such as <code class="inline">move/2</code>, the instruction dispatch
│ │ │ @@ -271,21 +271,21 @@
│ │ │  with an uppercase letter just as in Erlang.  A pattern variable may be
│ │ │  followed <code class="inline">=</code> and one or more type letters to constrain the match to
│ │ │  one of those types.  The variables that are bound on the left-hand side can
│ │ │  be used on the right-hand side.</p><p>We will also need to define a specific instruction and an implementation:</p><pre><code class="makeup erlang" translate="no"><span class="p">#</span><span class="w"> </span><span class="n">In</span><span class="w"> </span><span class="ss">ops</span><span class="p">.</span><span class="ss">tab</span><span class="w">
│ │ │  </span><span class="ss">move2</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">y</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">In</span><span class="w"> </span><span class="ss">instrs</span><span class="p">.</span><span class="ss">tab</span><span class="w">
│ │ │ -</span><span class="nf">move2</span><span class="p" data-group-id="4763406324-1">(</span><span class="n">S1</span><span class="p">,</span><span class="w"> </span><span class="n">D1</span><span class="p">,</span><span class="w"> </span><span class="n">S2</span><span class="p">,</span><span class="w"> </span><span class="n">D2</span><span class="p" data-group-id="4763406324-1">)</span><span class="w"> </span><span class="p" data-group-id="4763406324-2">{</span><span class="w">
│ │ │ +</span><span class="nf">move2</span><span class="p" data-group-id="5016758098-1">(</span><span class="n">S1</span><span class="p">,</span><span class="w"> </span><span class="n">D1</span><span class="p">,</span><span class="w"> </span><span class="n">S2</span><span class="p">,</span><span class="w"> </span><span class="n">D2</span><span class="p" data-group-id="5016758098-1">)</span><span class="w"> </span><span class="p" data-group-id="5016758098-2">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="n">V2</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">V1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">V2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="sc">$D</span><span class="mi">1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">V1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="sc">$D</span><span class="mi">2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">V2</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4763406324-2">}</span></code></pre><p>When the loader has found a match and replaced the matched instructions,
│ │ │ +</span><span class="p" data-group-id="5016758098-2">}</span></code></pre><p>When the loader has found a match and replaced the matched instructions,
│ │ │  it will match the new instructions against the transformation rules.
│ │ │  Because of that, we can define the rule for a <code class="inline">move3/6</code> instruction
│ │ │  as follows:</p><pre><code class="makeup erlang" translate="no"><span class="ss">move2</span><span class="w"> </span><span class="n">X1</span><span class="o">=</span><span class="ss">x</span><span class="w"> </span><span class="n">Y1</span><span class="o">=</span><span class="ss">y</span><span class="w"> </span><span class="n">X2</span><span class="o">=</span><span class="ss">x</span><span class="w"> </span><span class="n">Y2</span><span class="o">=</span><span class="ss">y</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">move</span><span class="w"> </span><span class="n">X3</span><span class="o">=</span><span class="ss">x</span><span class="w"> </span><span class="n">Y3</span><span class="o">=</span><span class="ss">y</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │        </span><span class="ss">move3</span><span class="w"> </span><span class="n">X1</span><span class="w"> </span><span class="n">Y1</span><span class="w"> </span><span class="n">X2</span><span class="w"> </span><span class="n">Y2</span><span class="w"> </span><span class="n">X3</span><span class="w"> </span><span class="n">Y3</span></code></pre><p>(For readability, a long transformation line can be broken after <code class="inline">|</code>
│ │ │  and <code class="inline">=&gt;</code> operators.)</p><p>It would also be possible to define it like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">move</span><span class="w"> </span><span class="n">X1</span><span class="o">=</span><span class="ss">x</span><span class="w"> </span><span class="n">Y1</span><span class="o">=</span><span class="ss">y</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">move</span><span class="w"> </span><span class="n">X2</span><span class="o">=</span><span class="ss">x</span><span class="w"> </span><span class="n">Y2</span><span class="o">=</span><span class="ss">y</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">move</span><span class="w"> </span><span class="n">X3</span><span class="o">=</span><span class="ss">x</span><span class="w"> </span><span class="n">Y3</span><span class="o">=</span><span class="ss">y</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │       </span><span class="ss">move3</span><span class="w"> </span><span class="n">X1</span><span class="w"> </span><span class="n">Y1</span><span class="w"> </span><span class="n">X2</span><span class="w"> </span><span class="n">Y2</span><span class="w"> </span><span class="n">X3</span><span class="w"> </span><span class="n">Y3</span></code></pre><p>but in that case it must be defined before the rule for <code class="inline">move2/4</code>
│ │ │  because the first matching rule will be applied.</p><p>One must be careful not to create infinite loops.  For example, if we
│ │ │ @@ -433,29 +433,29 @@
│ │ │  </span><span class="ss">i_bs_get_integer_32</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">f</span><span class="o">?</span><span class="w"> </span><span class="ss">x</span><span class="w">
│ │ │  </span><span class="c1">%endif</span></code></pre><p>The specific instruction <code class="inline">i_bs_get_integer_32</code> will only be defined
│ │ │  on a 64-bit machine.</p><p>The condition can be inverted by using <code class="inline">%unless</code> instead of <code class="inline">%if</code>:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%unless NO_FPE_SIGNALS</span><span class="w">
│ │ │  </span><span class="ss">fcheckerror</span><span class="w"> </span><span class="ss">p</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">i_fcheckerror</span><span class="w">
│ │ │  </span><span class="ss">i_fcheckerror</span><span class="w">
│ │ │  </span><span class="ss">fclearerror</span><span class="w">
│ │ │  </span><span class="c1">%endif</span></code></pre><p>It is also possible to add an <code class="inline">%else</code> clause:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%if ARCH_64</span><span class="w">
│ │ │ -</span><span class="n">BS_SAFE_MUL</span><span class="p" data-group-id="9093908893-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="9093908893-1">)</span><span class="w"> </span><span class="p" data-group-id="9093908893-2">{</span><span class="w">
│ │ │ -    </span><span class="n">Uint64</span><span class="w"> </span><span class="ss">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9093908893-3">(</span><span class="sc">$A</span><span class="p" data-group-id="9093908893-3">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="p" data-group-id="9093908893-4">(</span><span class="sc">$B</span><span class="p" data-group-id="9093908893-4">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="9093908893-5">(</span><span class="ss">res</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="sc">$B</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="sc">$A</span><span class="p" data-group-id="9093908893-5">)</span><span class="w"> </span><span class="p" data-group-id="9093908893-6">{</span><span class="w">
│ │ │ +</span><span class="n">BS_SAFE_MUL</span><span class="p" data-group-id="3193862457-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="3193862457-1">)</span><span class="w"> </span><span class="p" data-group-id="3193862457-2">{</span><span class="w">
│ │ │ +    </span><span class="n">Uint64</span><span class="w"> </span><span class="ss">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3193862457-3">(</span><span class="sc">$A</span><span class="p" data-group-id="3193862457-3">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="p" data-group-id="3193862457-4">(</span><span class="sc">$B</span><span class="p" data-group-id="3193862457-4">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="3193862457-5">(</span><span class="ss">res</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="sc">$B</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="sc">$A</span><span class="p" data-group-id="3193862457-5">)</span><span class="w"> </span><span class="p" data-group-id="3193862457-6">{</span><span class="w">
│ │ │          </span><span class="sc">$F</span><span class="ss">ail</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9093908893-6">}</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3193862457-6">}</span><span class="w">
│ │ │      </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">res</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9093908893-2">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3193862457-2">}</span><span class="w">
│ │ │  </span><span class="c1">%else</span><span class="w">
│ │ │ -</span><span class="n">BS_SAFE_MUL</span><span class="p" data-group-id="9093908893-7">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="9093908893-7">)</span><span class="w"> </span><span class="p" data-group-id="9093908893-8">{</span><span class="w">
│ │ │ -    </span><span class="n">Uint64</span><span class="w"> </span><span class="ss">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9093908893-9">(</span><span class="n">Uint64</span><span class="p" data-group-id="9093908893-9">)</span><span class="p" data-group-id="9093908893-10">(</span><span class="sc">$A</span><span class="p" data-group-id="9093908893-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="p" data-group-id="9093908893-11">(</span><span class="n">Uint64</span><span class="p" data-group-id="9093908893-11">)</span><span class="p" data-group-id="9093908893-12">(</span><span class="sc">$B</span><span class="p" data-group-id="9093908893-12">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="9093908893-13">(</span><span class="p" data-group-id="9093908893-14">(</span><span class="ss">res</span><span class="w"> </span><span class="p">&gt;&gt;</span><span class="w"> </span><span class="p" data-group-id="9093908893-15">(</span><span class="mi">8</span><span class="o">*</span><span class="nf">sizeof</span><span class="p" data-group-id="9093908893-16">(</span><span class="n">Uint</span><span class="p" data-group-id="9093908893-16">)</span><span class="p" data-group-id="9093908893-15">)</span><span class="p" data-group-id="9093908893-14">)</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="9093908893-13">)</span><span class="w"> </span><span class="p" data-group-id="9093908893-17">{</span><span class="w">
│ │ │ +</span><span class="n">BS_SAFE_MUL</span><span class="p" data-group-id="3193862457-7">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="3193862457-7">)</span><span class="w"> </span><span class="p" data-group-id="3193862457-8">{</span><span class="w">
│ │ │ +    </span><span class="n">Uint64</span><span class="w"> </span><span class="ss">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3193862457-9">(</span><span class="n">Uint64</span><span class="p" data-group-id="3193862457-9">)</span><span class="p" data-group-id="3193862457-10">(</span><span class="sc">$A</span><span class="p" data-group-id="3193862457-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="p" data-group-id="3193862457-11">(</span><span class="n">Uint64</span><span class="p" data-group-id="3193862457-11">)</span><span class="p" data-group-id="3193862457-12">(</span><span class="sc">$B</span><span class="p" data-group-id="3193862457-12">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="3193862457-13">(</span><span class="p" data-group-id="3193862457-14">(</span><span class="ss">res</span><span class="w"> </span><span class="p">&gt;&gt;</span><span class="w"> </span><span class="p" data-group-id="3193862457-15">(</span><span class="mi">8</span><span class="o">*</span><span class="nf">sizeof</span><span class="p" data-group-id="3193862457-16">(</span><span class="n">Uint</span><span class="p" data-group-id="3193862457-16">)</span><span class="p" data-group-id="3193862457-15">)</span><span class="p" data-group-id="3193862457-14">)</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="3193862457-13">)</span><span class="w"> </span><span class="p" data-group-id="3193862457-17">{</span><span class="w">
│ │ │          </span><span class="sc">$F</span><span class="ss">ail</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9093908893-17">}</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3193862457-17">}</span><span class="w">
│ │ │      </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">res</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9093908893-8">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3193862457-8">}</span><span class="w">
│ │ │  </span><span class="c1">%endif</span></code></pre><h4>Symbols that are defined in directives</h4><p>The following symbols are always defined.</p><ul><li><code class="inline">ARCH_64</code> - is 1 for a 64-bit machine, and 0 otherwise.</li><li><code class="inline">ARCH_32</code> - is 1 for 32-bit machine, and 0 otherwise.</li></ul><p>The <code class="inline">Makefile</code> for building the emulator currently defines the
│ │ │  following symbols by using the <code class="inline">-D</code> option on the command line for
│ │ │  <strong>beam_makeops</strong>.</p><ul><li><code class="inline">USE_VM_PROBES</code> - 1 if the runtime system is compiled to use VM
│ │ │  probes (support for dtrace or systemtap), 0 otherwise.</li></ul><h3 id="defining-external-generic-instructions" class="section-heading">
│ │ │    <a href="#defining-external-generic-instructions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -680,57 +680,57 @@
│ │ │  match both source and destination registers.  As an operand in a specific
│ │ │  instruction, it must only be used for a destination register.)</p></li><li><p><code class="inline">o</code> - Overflow.  An untagged integer that does not fit in a machine word.</p></li></ul><h4>Predicates</h4><p>If the constraints described so far is not enough, additional
│ │ │  constraints can be implemented in C and be called as a guard function
│ │ │  on the left-hand side of the transformation.  If the guard function returns
│ │ │  a non-zero value, the matching of the rule will continue, otherwise
│ │ │  the match will fail.  Such guard functions are hereafter called
│ │ │  <em>predicates</em>.</p><p>The most commonly used guard constraints is <code class="inline">equal()</code>. It can be used
│ │ │ -to remove a redundant <code class="inline">move</code> instruction like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">move</span><span class="w"> </span><span class="n">R1</span><span class="w"> </span><span class="n">R2</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">equal</span><span class="p" data-group-id="3101316867-1">(</span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p" data-group-id="3101316867-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p">_</span></code></pre><p>or remove a redundant <code class="inline">is_eq_exact</code> instruction like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">is_eq_exact</span><span class="w"> </span><span class="n">Lbl</span><span class="w"> </span><span class="n">Src1</span><span class="w"> </span><span class="n">Src2</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">equal</span><span class="p" data-group-id="9351990861-1">(</span><span class="n">Src1</span><span class="p">,</span><span class="w"> </span><span class="n">Src2</span><span class="p" data-group-id="9351990861-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p">_</span></code></pre><p>At the time of writing, all predicates are defined in files named
│ │ │ +to remove a redundant <code class="inline">move</code> instruction like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">move</span><span class="w"> </span><span class="n">R1</span><span class="w"> </span><span class="n">R2</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">equal</span><span class="p" data-group-id="1418067707-1">(</span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p" data-group-id="1418067707-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p">_</span></code></pre><p>or remove a redundant <code class="inline">is_eq_exact</code> instruction like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">is_eq_exact</span><span class="w"> </span><span class="n">Lbl</span><span class="w"> </span><span class="n">Src1</span><span class="w"> </span><span class="n">Src2</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">equal</span><span class="p" data-group-id="1172208897-1">(</span><span class="n">Src1</span><span class="p">,</span><span class="w"> </span><span class="n">Src2</span><span class="p" data-group-id="1172208897-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p">_</span></code></pre><p>At the time of writing, all predicates are defined in files named
│ │ │  <code class="inline">predicates.tab</code> in several directories:</p><ul><li><p>Predicates used by both the interpreter and the JIT implementations
│ │ │  are contained in <code class="inline">$ERL_TOP/erts/emulator/beam/predicates.tab</code>.</p></li><li><p>Predicates only used by x86_64 JIT can be found in
│ │ │  <code class="inline">$ERL_TOP/erts/emulator/beam/jit/x86/predicates.tab</code>.</p></li><li><p>Predicates only used by AArc64 (Arm64) JIT can be found in
│ │ │  <code class="inline">$ERL_TOP/erts/emulator/beam/jit/arm/predicates.tab</code>.</p></li><li><p>Predicates only used by the interpreter can be found in
│ │ │  <code class="inline">$ERL_TOP/erts/emulator/beam/emu/predicates.tab</code>.</p></li></ul><h3 id="a-very-brief-note-on-implementation-of-predicates" class="section-heading">
│ │ │    <a href="#a-very-brief-note-on-implementation-of-predicates" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">A very brief note on implementation of predicates</span>
│ │ │  </h3>
│ │ │  <p>It is outside the scope for this document to describe in detail how
│ │ │  predicates are implemented because it requires knowledge of the
│ │ │  internal loader data structures, but here is quick look at the
│ │ │ -implementation of a simple predicate called <code class="inline">literal_is_map()</code>.</p><p>Here is first an example how it is used:</p><pre><code class="makeup erlang" translate="no"><span class="ss">is_map</span><span class="w"> </span><span class="n">Fail</span><span class="w"> </span><span class="n">Lit</span><span class="o">=</span><span class="ss">q</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">literal_is_map</span><span class="p" data-group-id="2847508113-1">(</span><span class="n">Lit</span><span class="p" data-group-id="2847508113-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p">_</span></code></pre><p>If the <code class="inline">Lit</code> operand is a literal, then the <code class="inline">literal_is_map()</code>
│ │ │ +implementation of a simple predicate called <code class="inline">literal_is_map()</code>.</p><p>Here is first an example how it is used:</p><pre><code class="makeup erlang" translate="no"><span class="ss">is_map</span><span class="w"> </span><span class="n">Fail</span><span class="w"> </span><span class="n">Lit</span><span class="o">=</span><span class="ss">q</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">literal_is_map</span><span class="p" data-group-id="2711638180-1">(</span><span class="n">Lit</span><span class="p" data-group-id="2711638180-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p">_</span></code></pre><p>If the <code class="inline">Lit</code> operand is a literal, then the <code class="inline">literal_is_map()</code>
│ │ │  predicate is called to determine whether it is a map literal.
│ │ │ -If it is, the instruction is not needed and can be removed.</p><p><code class="inline">literal_is_map()</code> is implemented like this (in <code class="inline">emu/predicates.tab</code>):</p><pre><code class="makeup erlang" translate="no"><span class="ss">pred</span><span class="p">.</span><span class="nf">literal_is_map</span><span class="p" data-group-id="9872345564-1">(</span><span class="n">Lit</span><span class="p" data-group-id="9872345564-1">)</span><span class="w"> </span><span class="p" data-group-id="9872345564-2">{</span><span class="w">
│ │ │ +If it is, the instruction is not needed and can be removed.</p><p><code class="inline">literal_is_map()</code> is implemented like this (in <code class="inline">emu/predicates.tab</code>):</p><pre><code class="makeup erlang" translate="no"><span class="ss">pred</span><span class="p">.</span><span class="nf">literal_is_map</span><span class="p" data-group-id="7505912312-1">(</span><span class="n">Lit</span><span class="p" data-group-id="7505912312-1">)</span><span class="w"> </span><span class="p" data-group-id="7505912312-2">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">term</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="9872345564-3">(</span><span class="n">Lit</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_q</span><span class="p" data-group-id="9872345564-3">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">term</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">beamfile_get_literal</span><span class="p" data-group-id="9872345564-4">(</span><span class="err">&amp;</span><span class="n">S</span><span class="p">-&gt;</span><span class="ss">beam</span><span class="p">,</span><span class="w"> </span><span class="n">Lit</span><span class="p">.</span><span class="ss">val</span><span class="p" data-group-id="9872345564-4">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">return</span><span class="w"> </span><span class="nf">is_map</span><span class="p" data-group-id="9872345564-5">(</span><span class="ss">term</span><span class="p" data-group-id="9872345564-5">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9872345564-2">}</span></code></pre><p>The <code class="inline">pred.</code> prefix tells <strong>beam_makeops</strong> that this function is a
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="7505912312-3">(</span><span class="n">Lit</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_q</span><span class="p" data-group-id="7505912312-3">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">term</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">beamfile_get_literal</span><span class="p" data-group-id="7505912312-4">(</span><span class="err">&amp;</span><span class="n">S</span><span class="p">-&gt;</span><span class="ss">beam</span><span class="p">,</span><span class="w"> </span><span class="n">Lit</span><span class="p">.</span><span class="ss">val</span><span class="p" data-group-id="7505912312-4">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">return</span><span class="w"> </span><span class="nf">is_map</span><span class="p" data-group-id="7505912312-5">(</span><span class="ss">term</span><span class="p" data-group-id="7505912312-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7505912312-2">}</span></code></pre><p>The <code class="inline">pred.</code> prefix tells <strong>beam_makeops</strong> that this function is a
│ │ │  predicate.  Without the prefix, it would have been interpreted as the
│ │ │  implementation of an instruction (described in <strong>Defining the
│ │ │  implementation</strong>).</p><p>Predicate functions have a magic variable called <code class="inline">S</code>, which is a
│ │ │  pointer to a state struct. In the example,
│ │ │  <code class="inline">beamfile_get_literal(&amp;S-&gt;beam, Lit.val);</code> is used to retrieve the actual term
│ │ │  for the literal.</p><p>At the time of writing, the expanded C code generated by
│ │ │ -<strong>beam_makeops</strong> looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">static</span><span class="w"> </span><span class="ss">int</span><span class="w"> </span><span class="nf">literal_is_map</span><span class="p" data-group-id="3719992232-1">(</span><span class="n">LoaderState</span><span class="o">*</span><span class="w"> </span><span class="n">S</span><span class="p">,</span><span class="w"> </span><span class="n">BeamOpArg</span><span class="w"> </span><span class="n">Lit</span><span class="p" data-group-id="3719992232-1">)</span><span class="w"> </span><span class="p" data-group-id="3719992232-2">{</span><span class="w">
│ │ │ +<strong>beam_makeops</strong> looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">static</span><span class="w"> </span><span class="ss">int</span><span class="w"> </span><span class="nf">literal_is_map</span><span class="p" data-group-id="7137251883-1">(</span><span class="n">LoaderState</span><span class="o">*</span><span class="w"> </span><span class="n">S</span><span class="p">,</span><span class="w"> </span><span class="n">BeamOpArg</span><span class="w"> </span><span class="n">Lit</span><span class="p" data-group-id="7137251883-1">)</span><span class="w"> </span><span class="p" data-group-id="7137251883-2">{</span><span class="w">
│ │ │    </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">term</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="3719992232-3">(</span><span class="n">Lit</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_q</span><span class="p" data-group-id="3719992232-3">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="ss">term</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p">-&gt;</span><span class="ss">literals</span><span class="p" data-group-id="3719992232-4">[</span><span class="n">Lit</span><span class="p">.</span><span class="ss">val</span><span class="p" data-group-id="3719992232-4">]</span><span class="p">.</span><span class="ss">term</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="ss">return</span><span class="w"> </span><span class="nf">is_map</span><span class="p" data-group-id="3719992232-5">(</span><span class="ss">term</span><span class="p" data-group-id="3719992232-5">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3719992232-2">}</span></code></pre><h4>Handling instructions with variable number of operands</h4><p>Some instructions, such as <code class="inline">select_val/3</code>, essentially has a variable
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="7137251883-3">(</span><span class="n">Lit</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_q</span><span class="p" data-group-id="7137251883-3">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="ss">term</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p">-&gt;</span><span class="ss">literals</span><span class="p" data-group-id="7137251883-4">[</span><span class="n">Lit</span><span class="p">.</span><span class="ss">val</span><span class="p" data-group-id="7137251883-4">]</span><span class="p">.</span><span class="ss">term</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="ss">return</span><span class="w"> </span><span class="nf">is_map</span><span class="p" data-group-id="7137251883-5">(</span><span class="ss">term</span><span class="p" data-group-id="7137251883-5">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7137251883-2">}</span></code></pre><h4>Handling instructions with variable number of operands</h4><p>Some instructions, such as <code class="inline">select_val/3</code>, essentially has a variable
│ │ │  number of operands.  Such instructions have a <code class="inline">{list,[...]}</code> operand
│ │ │ -as their last operand in the BEAM assembly code.  For example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1532241586-1">{</span><span class="ss">select_val</span><span class="p">,</span><span class="p" data-group-id="1532241586-2">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="1532241586-2">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="1532241586-3">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="1532241586-3">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="1532241586-4">{</span><span class="ss">list</span><span class="p">,</span><span class="p" data-group-id="1532241586-5">[</span><span class="p" data-group-id="1532241586-6">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1532241586-6">}</span><span class="p">,</span><span class="p" data-group-id="1532241586-7">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="1532241586-7">}</span><span class="p">,</span><span class="p" data-group-id="1532241586-8">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1532241586-8">}</span><span class="p">,</span><span class="p" data-group-id="1532241586-9">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="1532241586-9">}</span><span class="p" data-group-id="1532241586-5">]</span><span class="p" data-group-id="1532241586-4">}</span><span class="p" data-group-id="1532241586-1">}</span><span class="p">.</span></code></pre><p>The loader will convert a <code class="inline">{list,[...]}</code> operand to an <code class="inline">u</code> operand whose
│ │ │ +as their last operand in the BEAM assembly code.  For example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5328279043-1">{</span><span class="ss">select_val</span><span class="p">,</span><span class="p" data-group-id="5328279043-2">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="5328279043-2">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="5328279043-3">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5328279043-3">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="5328279043-4">{</span><span class="ss">list</span><span class="p">,</span><span class="p" data-group-id="5328279043-5">[</span><span class="p" data-group-id="5328279043-6">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="5328279043-6">}</span><span class="p">,</span><span class="p" data-group-id="5328279043-7">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5328279043-7">}</span><span class="p">,</span><span class="p" data-group-id="5328279043-8">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="5328279043-8">}</span><span class="p">,</span><span class="p" data-group-id="5328279043-9">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5328279043-9">}</span><span class="p" data-group-id="5328279043-5">]</span><span class="p" data-group-id="5328279043-4">}</span><span class="p" data-group-id="5328279043-1">}</span><span class="p">.</span></code></pre><p>The loader will convert a <code class="inline">{list,[...]}</code> operand to an <code class="inline">u</code> operand whose
│ │ │  value is the number of elements in the list, followed by each element in
│ │ │  the list.  The instruction above would be translated to the following
│ │ │ -generic instruction:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0422628973-1">{</span><span class="ss">select_val</span><span class="p">,</span><span class="p" data-group-id="0422628973-2">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="0422628973-2">}</span><span class="p">,</span><span class="p" data-group-id="0422628973-3">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0422628973-3">}</span><span class="p">,</span><span class="p" data-group-id="0422628973-4">{</span><span class="ss">u</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0422628973-4">}</span><span class="p">,</span><span class="p" data-group-id="0422628973-5">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="0422628973-5">}</span><span class="p">,</span><span class="p" data-group-id="0422628973-6">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0422628973-6">}</span><span class="p">,</span><span class="p" data-group-id="0422628973-7">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="0422628973-7">}</span><span class="p">,</span><span class="p" data-group-id="0422628973-8">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0422628973-8">}</span><span class="p" data-group-id="0422628973-1">}</span></code></pre><p>To match a variable number of arguments we need to use the special
│ │ │ +generic instruction:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8332161424-1">{</span><span class="ss">select_val</span><span class="p">,</span><span class="p" data-group-id="8332161424-2">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="8332161424-2">}</span><span class="p">,</span><span class="p" data-group-id="8332161424-3">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="8332161424-3">}</span><span class="p">,</span><span class="p" data-group-id="8332161424-4">{</span><span class="ss">u</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="8332161424-4">}</span><span class="p">,</span><span class="p" data-group-id="8332161424-5">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="8332161424-5">}</span><span class="p">,</span><span class="p" data-group-id="8332161424-6">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="8332161424-6">}</span><span class="p">,</span><span class="p" data-group-id="8332161424-7">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="8332161424-7">}</span><span class="p">,</span><span class="p" data-group-id="8332161424-8">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8332161424-8">}</span><span class="p" data-group-id="8332161424-1">}</span></code></pre><p>To match a variable number of arguments we need to use the special
│ │ │  operand type <code class="inline">*</code> like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">select_val</span><span class="w"> </span><span class="n">Src</span><span class="o">=</span><span class="ss">aiq</span><span class="w"> </span><span class="n">Fail</span><span class="o">=</span><span class="ss">f</span><span class="w"> </span><span class="n">Size</span><span class="o">=</span><span class="ss">u</span><span class="w"> </span><span class="n">List</span><span class="o">=</span><span class="o">*</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │      </span><span class="ss">i_const_select_val</span><span class="w"> </span><span class="n">Src</span><span class="w"> </span><span class="n">Fail</span><span class="w"> </span><span class="n">Size</span><span class="w"> </span><span class="n">List</span></code></pre><p>This transformation renames a <code class="inline">select_val/3</code> instruction
│ │ │  with a constant source operand to <code class="inline">i_const_select_val/3</code>.</p><h4>Constructing new instructions on the right-hand side</h4><p>The most common operand on the right-hand side is a variable that was
│ │ │  bound while matching the pattern on the left-hand side.  For example:</p><pre><code class="makeup erlang" translate="no"><span class="ss">trim</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="n">Remaining</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">i_trim</span><span class="w"> </span><span class="n">N</span></code></pre><p>An operand can also be a type letter to construct an operand of that
│ │ │  type.  Each type has a default value.  For example, the type <code class="inline">x</code> has
│ │ │  the default value 1023, which is the highest X register.  That makes
│ │ │  <code class="inline">x</code> on the right-hand side a convenient shortcut for a temporary X
│ │ │ @@ -751,53 +751,53 @@
│ │ │  transformation rule.</p><ul><li><p><code class="inline">u</code> - Construct an untagged integer.  The default value is 0.</p></li><li><p><code class="inline">x</code> - X register.  The default value is 1023.  That makes <code class="inline">x</code> convenient to
│ │ │  use as a temporary X register.</p></li><li><p><code class="inline">y</code> - Y register.  The default value is 0.</p></li><li><p><code class="inline">l</code> - Floating point register number.  The default value is 0.</p></li><li><p><code class="inline">i</code> - Tagged literal integer.  The default value is 0.</p></li><li><p><code class="inline">a</code> - Tagged atom.  The default value is the empty atom (<code class="inline">am_Empty</code>).</p></li><li><p><code class="inline">p</code> - Zero failure label.</p></li><li><p><code class="inline">n</code> - NIL (<code class="inline">[]</code>, the empty list).</p></li></ul><h4>Function call on the right-hand side</h4><p>Transformations that are not possible to describe with the rule
│ │ │  language as described here can be implemented as a generator function
│ │ │  in C and called from the right-hand side of a transformation.  The left-hand
│ │ │  side of the transformation will perform the match and bind operands to
│ │ │  variables.  The variables can then be passed to a generator function
│ │ │  on the right-hand side.  For example:</p><pre><code class="makeup erlang" translate="no"><span class="ss">bif2</span><span class="w"> </span><span class="n">Fail</span><span class="o">=</span><span class="ss">j</span><span class="w"> </span><span class="ss">u</span><span class="sc">$b</span><span class="nc">if</span><span class="p">:</span><span class="nc">erlang</span><span class="p">:</span><span class="nb">element</span><span class="p">/</span><span class="mi">2</span><span class="w"> </span><span class="n">Index</span><span class="o">=</span><span class="ss">s</span><span class="w"> </span><span class="n">Tuple</span><span class="o">=</span><span class="ss">xy</span><span class="w"> </span><span class="n">Dst</span><span class="o">=</span><span class="ss">d</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">element</span><span class="p" data-group-id="2560579209-1">(</span><span class="n">Jump</span><span class="p">,</span><span class="w"> </span><span class="n">Index</span><span class="p">,</span><span class="w"> </span><span class="n">Tuple</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="2560579209-1">)</span></code></pre><p>This transformation rule matches a call to the BIF <a href="erlang.html#element/2"><code class="inline">element/2</code></a>.
│ │ │ +    </span><span class="nf">element</span><span class="p" data-group-id="3688761999-1">(</span><span class="n">Jump</span><span class="p">,</span><span class="w"> </span><span class="n">Index</span><span class="p">,</span><span class="w"> </span><span class="n">Tuple</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="3688761999-1">)</span></code></pre><p>This transformation rule matches a call to the BIF <a href="erlang.html#element/2"><code class="inline">element/2</code></a>.
│ │ │  The operands will be captured and the generator function <code class="inline">element()</code> will
│ │ │  be called.</p><p>The <code class="inline">element()</code> generator will produce one of two instructions
│ │ │  depending on <code class="inline">Index</code>.  If <code class="inline">Index</code> is an integer in the range from 1 up
│ │ │  to the maximum tuple size, the instruction <code class="inline">i_fast_element/2</code> will be
│ │ │  produced, otherwise the instruction <code class="inline">i_element/4</code> will be produced.
│ │ │  The corresponding specific instructions are:</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_fast_element</span><span class="w"> </span><span class="ss">xy</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="n">I</span><span class="w"> </span><span class="ss">d</span><span class="w">
│ │ │  </span><span class="ss">i_element</span><span class="w"> </span><span class="ss">xy</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="ss">d</span></code></pre><p>The <code class="inline">i_fast_element/2</code> instruction is faster because the tuple is
│ │ │  already an untagged integer.  It also knows that the index is at least
│ │ │  1, so it does not have to test for that.  The <code class="inline">i_element/4</code>
│ │ │  instruction will have to fetch the index from a register, test that it
│ │ │  is an integer, and untag the integer.</p><p>At the time of writing, all generators functions were defined in files
│ │ │  named <code class="inline">generators.tab</code> in several directories (in the same directories
│ │ │  as the <code class="inline">predicates.tab</code> files).</p><p>It is outside the scope of this document to describe in detail how
│ │ │  generator functions are written, but here is the implementation of
│ │ │ -<code class="inline">element()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">gen</span><span class="p">.</span><span class="nf">element</span><span class="p" data-group-id="8841702307-1">(</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Index</span><span class="p">,</span><span class="w"> </span><span class="n">Tuple</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="8841702307-1">)</span><span class="w"> </span><span class="p" data-group-id="8841702307-2">{</span><span class="w">
│ │ │ +<code class="inline">element()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">gen</span><span class="p">.</span><span class="nf">element</span><span class="p" data-group-id="2138052772-1">(</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Index</span><span class="p">,</span><span class="w"> </span><span class="n">Tuple</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="2138052772-1">)</span><span class="w"> </span><span class="p" data-group-id="2138052772-2">{</span><span class="w">
│ │ │      </span><span class="n">BeamOp</span><span class="o">*</span><span class="w"> </span><span class="ss">op</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="sc">$N</span><span class="nf">ewBeamOp</span><span class="p" data-group-id="8841702307-3">(</span><span class="n">S</span><span class="p">,</span><span class="w"> </span><span class="ss">op</span><span class="p" data-group-id="8841702307-3">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="sc">$N</span><span class="nf">ewBeamOp</span><span class="p" data-group-id="2138052772-3">(</span><span class="n">S</span><span class="p">,</span><span class="w"> </span><span class="ss">op</span><span class="p" data-group-id="2138052772-3">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="8841702307-4">(</span><span class="n">Index</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_i</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Index</span><span class="p">.</span><span class="ss">val</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="2138052772-4">(</span><span class="n">Index</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_i</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Index</span><span class="p">.</span><span class="ss">val</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w">
│ │ │          </span><span class="n">Index</span><span class="p">.</span><span class="ss">val</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">ERTS_MAX_TUPLE_SIZE</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="8841702307-5">(</span><span class="n">Tuple</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_x</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Tuple</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_y</span><span class="p" data-group-id="8841702307-5">)</span><span class="p" data-group-id="8841702307-4">)</span><span class="w"> </span><span class="p" data-group-id="8841702307-6">{</span><span class="w">
│ │ │ -        </span><span class="sc">$B</span><span class="nf">eamOpNameArity</span><span class="p" data-group-id="8841702307-7">(</span><span class="ss">op</span><span class="p">,</span><span class="w"> </span><span class="ss">i_fast_element</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="8841702307-7">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="8841702307-8">[</span><span class="mi">0</span><span class="p" data-group-id="8841702307-8">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Tuple</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="8841702307-9">[</span><span class="mi">1</span><span class="p" data-group-id="8841702307-9">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Fail</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="8841702307-10">[</span><span class="mi">2</span><span class="p" data-group-id="8841702307-10">]</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">TAG_u</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="8841702307-11">[</span><span class="mi">2</span><span class="p" data-group-id="8841702307-11">]</span><span class="p">.</span><span class="ss">val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Index</span><span class="p">.</span><span class="ss">val</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="8841702307-12">[</span><span class="mi">3</span><span class="p" data-group-id="8841702307-12">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dst</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8841702307-6">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p" data-group-id="8841702307-13">{</span><span class="w">
│ │ │ -        </span><span class="sc">$B</span><span class="nf">eamOpNameArity</span><span class="p" data-group-id="8841702307-14">(</span><span class="ss">op</span><span class="p">,</span><span class="w"> </span><span class="ss">i_element</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="8841702307-14">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="8841702307-15">[</span><span class="mi">0</span><span class="p" data-group-id="8841702307-15">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Tuple</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="8841702307-16">[</span><span class="mi">1</span><span class="p" data-group-id="8841702307-16">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Fail</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="8841702307-17">[</span><span class="mi">2</span><span class="p" data-group-id="8841702307-17">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Index</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="8841702307-18">[</span><span class="mi">3</span><span class="p" data-group-id="8841702307-18">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dst</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8841702307-13">}</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2138052772-5">(</span><span class="n">Tuple</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_x</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Tuple</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_y</span><span class="p" data-group-id="2138052772-5">)</span><span class="p" data-group-id="2138052772-4">)</span><span class="w"> </span><span class="p" data-group-id="2138052772-6">{</span><span class="w">
│ │ │ +        </span><span class="sc">$B</span><span class="nf">eamOpNameArity</span><span class="p" data-group-id="2138052772-7">(</span><span class="ss">op</span><span class="p">,</span><span class="w"> </span><span class="ss">i_fast_element</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="2138052772-7">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="2138052772-8">[</span><span class="mi">0</span><span class="p" data-group-id="2138052772-8">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Tuple</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="2138052772-9">[</span><span class="mi">1</span><span class="p" data-group-id="2138052772-9">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Fail</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="2138052772-10">[</span><span class="mi">2</span><span class="p" data-group-id="2138052772-10">]</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">TAG_u</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="2138052772-11">[</span><span class="mi">2</span><span class="p" data-group-id="2138052772-11">]</span><span class="p">.</span><span class="ss">val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Index</span><span class="p">.</span><span class="ss">val</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="2138052772-12">[</span><span class="mi">3</span><span class="p" data-group-id="2138052772-12">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dst</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2138052772-6">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p" data-group-id="2138052772-13">{</span><span class="w">
│ │ │ +        </span><span class="sc">$B</span><span class="nf">eamOpNameArity</span><span class="p" data-group-id="2138052772-14">(</span><span class="ss">op</span><span class="p">,</span><span class="w"> </span><span class="ss">i_element</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="2138052772-14">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="2138052772-15">[</span><span class="mi">0</span><span class="p" data-group-id="2138052772-15">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Tuple</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="2138052772-16">[</span><span class="mi">1</span><span class="p" data-group-id="2138052772-16">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Fail</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="2138052772-17">[</span><span class="mi">2</span><span class="p" data-group-id="2138052772-17">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Index</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="2138052772-18">[</span><span class="mi">3</span><span class="p" data-group-id="2138052772-18">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dst</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2138052772-13">}</span><span class="w">
│ │ │  
│ │ │      </span><span class="ss">return</span><span class="w"> </span><span class="ss">op</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8841702307-2">}</span></code></pre><p>The <code class="inline">gen.</code> prefix tells <strong>beam_makeops</strong> that this function is a
│ │ │ +</span><span class="p" data-group-id="2138052772-2">}</span></code></pre><p>The <code class="inline">gen.</code> prefix tells <strong>beam_makeops</strong> that this function is a
│ │ │  generator.  Without the prefix, it would have been interpreted as the
│ │ │  implementation of an instruction (described in <strong>Defining the
│ │ │  implementation</strong>).</p><p>Generator functions have a magic variable called <code class="inline">S</code>, which is a
│ │ │  pointer to a state struct.  In the example, <code class="inline">S</code> is used in the invocation
│ │ │  of the <code class="inline">NewBeamOp</code> macro.</p><h3 id="defining-the-implementation" class="section-heading">
│ │ │    <a href="#defining-the-implementation" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -819,431 +819,431 @@
│ │ │  </span><span class="ss">msg_instrs</span><span class="p">.</span><span class="ss">tab</span><span class="w">
│ │ │  </span><span class="ss">select_instrs</span><span class="p">.</span><span class="ss">tab</span><span class="w">
│ │ │  </span><span class="ss">trace_instrs</span><span class="p">.</span><span class="ss">tab</span></code></pre><p>There is also a file that only contains macro definitions:</p><pre><code class="makeup erlang" translate="no"><span class="ss">macros</span><span class="p">.</span><span class="ss">tab</span></code></pre><p>The syntax of each file is similar to C code.  In fact, most of
│ │ │  the contents <em>is</em> C code, interspersed with macro invocations.</p><p>To allow Emacs to auto-indent the code, each file starts with the
│ │ │  following line:</p><pre><code class="makeup erlang" translate="no"><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="o">-</span><span class="o">*</span><span class="o">-</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="o">-</span><span class="o">*</span><span class="o">-</span></code></pre><p>To avoid messing up the indentation, all comments are written
│ │ │  as C++ style comments (<code class="inline">//</code>) instead of <code class="inline">#</code>.  Note that a comment
│ │ │  must start at the beginning of a line.</p><p>The meat of an instruction definition file are macro definitions.
│ │ │ -We have seen this macro definition before:</p><pre><code class="makeup erlang" translate="no"><span class="nf">move</span><span class="p" data-group-id="5463187162-1">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="5463187162-1">)</span><span class="w"> </span><span class="p" data-group-id="5463187162-2">{</span><span class="w">
│ │ │ +We have seen this macro definition before:</p><pre><code class="makeup erlang" translate="no"><span class="nf">move</span><span class="p" data-group-id="5262632485-1">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="5262632485-1">)</span><span class="w"> </span><span class="p" data-group-id="5262632485-2">{</span><span class="w">
│ │ │      </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">rc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5463187162-2">}</span></code></pre><p>A macro definitions must start at the beginning of the line (no spaces
│ │ │ +</span><span class="p" data-group-id="5262632485-2">}</span></code></pre><p>A macro definitions must start at the beginning of the line (no spaces
│ │ │  allowed), the opening curly bracket must be on the same line, and the
│ │ │  finishing curly bracket must be at the beginning of a line.  It is
│ │ │  recommended that the macro body is properly indented.</p><p>As a convention, the macro arguments in the head all start with an
│ │ │  uppercase letter.  In the body, the macro arguments can be expanded
│ │ │  by preceding them with <code class="inline">$</code>.</p><p>A macro definition whose name and arity matches a family of
│ │ │  specific instructions is assumed to be the implementation of that
│ │ │  instruction.</p><p>A macro can also be invoked from within another macro.  For example,
│ │ │  <code class="inline">move_deallocate_return/2</code> avoids repeating code by invoking
│ │ │ -<code class="inline">$deallocate_return()</code> as a macro:</p><pre><code class="makeup erlang" translate="no"><span class="nf">move_deallocate_return</span><span class="p" data-group-id="5759188802-1">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Deallocate</span><span class="p" data-group-id="5759188802-1">)</span><span class="w"> </span><span class="p" data-group-id="5759188802-2">{</span><span class="w">
│ │ │ -    </span><span class="nf">x</span><span class="p" data-group-id="5759188802-3">(</span><span class="mi">0</span><span class="p" data-group-id="5759188802-3">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">rc</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="sc">$d</span><span class="nf">eallocate_return</span><span class="p" data-group-id="5759188802-4">(</span><span class="sc">$D</span><span class="ss">eallocate</span><span class="p" data-group-id="5759188802-4">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5759188802-2">}</span></code></pre><p>Here is the definition of <code class="inline">deallocate_return/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">deallocate_return</span><span class="p" data-group-id="0045060150-1">(</span><span class="n">Deallocate</span><span class="p" data-group-id="0045060150-1">)</span><span class="w"> </span><span class="p" data-group-id="0045060150-2">{</span><span class="w">
│ │ │ +<code class="inline">$deallocate_return()</code> as a macro:</p><pre><code class="makeup erlang" translate="no"><span class="nf">move_deallocate_return</span><span class="p" data-group-id="5529752311-1">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Deallocate</span><span class="p" data-group-id="5529752311-1">)</span><span class="w"> </span><span class="p" data-group-id="5529752311-2">{</span><span class="w">
│ │ │ +    </span><span class="nf">x</span><span class="p" data-group-id="5529752311-3">(</span><span class="mi">0</span><span class="p" data-group-id="5529752311-3">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">rc</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="sc">$d</span><span class="nf">eallocate_return</span><span class="p" data-group-id="5529752311-4">(</span><span class="sc">$D</span><span class="ss">eallocate</span><span class="p" data-group-id="5529752311-4">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5529752311-2">}</span></code></pre><p>Here is the definition of <code class="inline">deallocate_return/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">deallocate_return</span><span class="p" data-group-id="7005358496-1">(</span><span class="n">Deallocate</span><span class="p" data-group-id="7005358496-1">)</span><span class="w"> </span><span class="p" data-group-id="7005358496-2">{</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="p">|</span><span class="w"> </span><span class="o">-</span><span class="ss">no_next</span><span class="w">
│ │ │      </span><span class="ss">int</span><span class="w"> </span><span class="ss">words_to_pop</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$D</span><span class="ss">eallocate</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">SET_I</span><span class="p" data-group-id="0045060150-3">(</span><span class="p" data-group-id="0045060150-4">(</span><span class="n">BeamInstr</span><span class="w"> </span><span class="o">*</span><span class="p" data-group-id="0045060150-4">)</span><span class="w"> </span><span class="nf">cp_val</span><span class="p" data-group-id="0045060150-5">(</span><span class="o">*</span><span class="n">E</span><span class="p" data-group-id="0045060150-5">)</span><span class="p" data-group-id="0045060150-3">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">E</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ADD_BYTE_OFFSET</span><span class="p" data-group-id="0045060150-6">(</span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="ss">words_to_pop</span><span class="p" data-group-id="0045060150-6">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">CHECK_TERM</span><span class="p" data-group-id="0045060150-7">(</span><span class="nf">x</span><span class="p" data-group-id="0045060150-8">(</span><span class="mi">0</span><span class="p" data-group-id="0045060150-8">)</span><span class="p" data-group-id="0045060150-7">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">SET_I</span><span class="p" data-group-id="7005358496-3">(</span><span class="p" data-group-id="7005358496-4">(</span><span class="n">BeamInstr</span><span class="w"> </span><span class="o">*</span><span class="p" data-group-id="7005358496-4">)</span><span class="w"> </span><span class="nf">cp_val</span><span class="p" data-group-id="7005358496-5">(</span><span class="o">*</span><span class="n">E</span><span class="p" data-group-id="7005358496-5">)</span><span class="p" data-group-id="7005358496-3">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">E</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ADD_BYTE_OFFSET</span><span class="p" data-group-id="7005358496-6">(</span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="ss">words_to_pop</span><span class="p" data-group-id="7005358496-6">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">CHECK_TERM</span><span class="p" data-group-id="7005358496-7">(</span><span class="nf">x</span><span class="p" data-group-id="7005358496-8">(</span><span class="mi">0</span><span class="p" data-group-id="7005358496-8">)</span><span class="p" data-group-id="7005358496-7">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">DispatchReturn</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0045060150-2">}</span></code></pre><p>The expanded code for <code class="inline">move_deallocate_return</code> will look this:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="2410425942-1">(</span><span class="ss">move_deallocate_return_cQ</span><span class="p" data-group-id="2410425942-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2410425942-2">{</span><span class="w">
│ │ │ -  </span><span class="nf">x</span><span class="p" data-group-id="2410425942-3">(</span><span class="mi">0</span><span class="p" data-group-id="2410425942-3">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="2410425942-4">[</span><span class="mi">1</span><span class="p" data-group-id="2410425942-4">]</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="ss">do</span><span class="w"> </span><span class="p" data-group-id="2410425942-5">{</span><span class="w">
│ │ │ -    </span><span class="ss">int</span><span class="w"> </span><span class="ss">words_to_pop</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Qb</span><span class="p" data-group-id="2410425942-6">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="2410425942-7">(</span><span class="n">I</span><span class="p" data-group-id="2410425942-8">[</span><span class="mi">0</span><span class="p" data-group-id="2410425942-8">]</span><span class="p" data-group-id="2410425942-7">)</span><span class="p" data-group-id="2410425942-6">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">SET_I</span><span class="p" data-group-id="2410425942-9">(</span><span class="p" data-group-id="2410425942-10">(</span><span class="n">BeamInstr</span><span class="w"> </span><span class="o">*</span><span class="p" data-group-id="2410425942-10">)</span><span class="w"> </span><span class="nf">cp_val</span><span class="p" data-group-id="2410425942-11">(</span><span class="o">*</span><span class="n">E</span><span class="p" data-group-id="2410425942-11">)</span><span class="p" data-group-id="2410425942-9">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">E</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ADD_BYTE_OFFSET</span><span class="p" data-group-id="2410425942-12">(</span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="ss">words_to_pop</span><span class="p" data-group-id="2410425942-12">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">CHECK_TERM</span><span class="p" data-group-id="2410425942-13">(</span><span class="nf">x</span><span class="p" data-group-id="2410425942-14">(</span><span class="mi">0</span><span class="p" data-group-id="2410425942-14">)</span><span class="p" data-group-id="2410425942-13">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7005358496-2">}</span></code></pre><p>The expanded code for <code class="inline">move_deallocate_return</code> will look this:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="0584960357-1">(</span><span class="ss">move_deallocate_return_cQ</span><span class="p" data-group-id="0584960357-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0584960357-2">{</span><span class="w">
│ │ │ +  </span><span class="nf">x</span><span class="p" data-group-id="0584960357-3">(</span><span class="mi">0</span><span class="p" data-group-id="0584960357-3">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="0584960357-4">[</span><span class="mi">1</span><span class="p" data-group-id="0584960357-4">]</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="ss">do</span><span class="w"> </span><span class="p" data-group-id="0584960357-5">{</span><span class="w">
│ │ │ +    </span><span class="ss">int</span><span class="w"> </span><span class="ss">words_to_pop</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Qb</span><span class="p" data-group-id="0584960357-6">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="0584960357-7">(</span><span class="n">I</span><span class="p" data-group-id="0584960357-8">[</span><span class="mi">0</span><span class="p" data-group-id="0584960357-8">]</span><span class="p" data-group-id="0584960357-7">)</span><span class="p" data-group-id="0584960357-6">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">SET_I</span><span class="p" data-group-id="0584960357-9">(</span><span class="p" data-group-id="0584960357-10">(</span><span class="n">BeamInstr</span><span class="w"> </span><span class="o">*</span><span class="p" data-group-id="0584960357-10">)</span><span class="w"> </span><span class="nf">cp_val</span><span class="p" data-group-id="0584960357-11">(</span><span class="o">*</span><span class="n">E</span><span class="p" data-group-id="0584960357-11">)</span><span class="p" data-group-id="0584960357-9">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">E</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ADD_BYTE_OFFSET</span><span class="p" data-group-id="0584960357-12">(</span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="ss">words_to_pop</span><span class="p" data-group-id="0584960357-12">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">CHECK_TERM</span><span class="p" data-group-id="0584960357-13">(</span><span class="nf">x</span><span class="p" data-group-id="0584960357-14">(</span><span class="mi">0</span><span class="p" data-group-id="0584960357-14">)</span><span class="p" data-group-id="0584960357-13">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">DispatchReturn</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="2410425942-5">}</span><span class="w"> </span><span class="nf">while</span><span class="w"> </span><span class="p" data-group-id="2410425942-15">(</span><span class="mi">0</span><span class="p" data-group-id="2410425942-15">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2410425942-2">}</span></code></pre><p>When expanding macros, <strong>beam_makeops</strong> wraps the expansion in a
│ │ │ +  </span><span class="p" data-group-id="0584960357-5">}</span><span class="w"> </span><span class="nf">while</span><span class="w"> </span><span class="p" data-group-id="0584960357-15">(</span><span class="mi">0</span><span class="p" data-group-id="0584960357-15">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0584960357-2">}</span></code></pre><p>When expanding macros, <strong>beam_makeops</strong> wraps the expansion in a
│ │ │  <code class="inline">do</code>/<code class="inline">while</code> wrapper unless <strong>beam_makeops</strong> can clearly see that no
│ │ │  wrapper is needed.  In this case, the wrapper is needed.</p><p>Note that arguments for macros cannot be complex expressions, because
│ │ │  the arguments are split on <code class="inline">,</code>.  For example, the following would
│ │ │  not work because <strong>beam_makeops</strong> would split the expression into
│ │ │ -two arguments:</p><pre><code class="makeup erlang" translate="no"><span class="sc">$d</span><span class="nf">eallocate_return</span><span class="p" data-group-id="0300582961-1">(</span><span class="nf">get_deallocation</span><span class="p" data-group-id="0300582961-2">(</span><span class="ss">y</span><span class="p">,</span><span class="w"> </span><span class="sc">$D</span><span class="ss">eallocate</span><span class="p" data-group-id="0300582961-2">)</span><span class="p" data-group-id="0300582961-1">)</span><span class="p">;</span></code></pre><h4>Code generation directives</h4><p>Within macro definitions, <code class="inline">//</code> comments are in general not treated
│ │ │ +two arguments:</p><pre><code class="makeup erlang" translate="no"><span class="sc">$d</span><span class="nf">eallocate_return</span><span class="p" data-group-id="5405180707-1">(</span><span class="nf">get_deallocation</span><span class="p" data-group-id="5405180707-2">(</span><span class="ss">y</span><span class="p">,</span><span class="w"> </span><span class="sc">$D</span><span class="ss">eallocate</span><span class="p" data-group-id="5405180707-2">)</span><span class="p" data-group-id="5405180707-1">)</span><span class="p">;</span></code></pre><h4>Code generation directives</h4><p>Within macro definitions, <code class="inline">//</code> comments are in general not treated
│ │ │  specially.  They will be copied to the file with the generated code
│ │ │  along with the rest of code in the body.</p><p>However, there is an exception. Within a macro definition, a line that
│ │ │  starts with whitespace followed by <code class="inline">//|</code> is treated specially.  The
│ │ │  rest of the line is assumed to contain directives to control code
│ │ │  generation.</p><p>Currently, two code generation directives are recognized:</p><ul><li><code class="inline">-no_prefetch</code></li><li><code class="inline">-no_next</code></li></ul><h5>The -no_prefetch directive</h5><p>To see what <code class="inline">-no_prefetch</code> does, let's first look at the default code
│ │ │ -generation.  Here is the code generated for <code class="inline">move_cx</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="4432722021-1">(</span><span class="ss">move_cx</span><span class="p" data-group-id="4432722021-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4432722021-2">{</span><span class="w">
│ │ │ -  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="4432722021-3">(</span><span class="n">I</span><span class="p" data-group-id="4432722021-4">[</span><span class="mi">2</span><span class="p" data-group-id="4432722021-4">]</span><span class="p" data-group-id="4432722021-3">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="nf">xb</span><span class="p" data-group-id="4432722021-5">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="4432722021-6">(</span><span class="n">I</span><span class="p" data-group-id="4432722021-7">[</span><span class="mi">0</span><span class="p" data-group-id="4432722021-7">]</span><span class="p" data-group-id="4432722021-6">)</span><span class="p" data-group-id="4432722021-5">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="4432722021-8">[</span><span class="mi">1</span><span class="p" data-group-id="4432722021-8">]</span><span class="p">;</span><span class="w">
│ │ │ +generation.  Here is the code generated for <code class="inline">move_cx</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="3148153140-1">(</span><span class="ss">move_cx</span><span class="p" data-group-id="3148153140-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3148153140-2">{</span><span class="w">
│ │ │ +  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="3148153140-3">(</span><span class="n">I</span><span class="p" data-group-id="3148153140-4">[</span><span class="mi">2</span><span class="p" data-group-id="3148153140-4">]</span><span class="p" data-group-id="3148153140-3">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="nf">xb</span><span class="p" data-group-id="3148153140-5">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="3148153140-6">(</span><span class="n">I</span><span class="p" data-group-id="3148153140-7">[</span><span class="mi">0</span><span class="p" data-group-id="3148153140-7">]</span><span class="p" data-group-id="3148153140-6">)</span><span class="p" data-group-id="3148153140-5">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="3148153140-8">[</span><span class="mi">1</span><span class="p" data-group-id="3148153140-8">]</span><span class="p">;</span><span class="w">
│ │ │    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="4432722021-9">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="4432722021-10">(</span><span class="ss">next_pf</span><span class="p" data-group-id="4432722021-10">)</span><span class="p" data-group-id="4432722021-9">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">GotoPF</span><span class="p" data-group-id="4432722021-11">(</span><span class="ss">next_pf</span><span class="p" data-group-id="4432722021-11">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4432722021-2">}</span></code></pre><p>Note that the very first thing done is to fetch the address to the
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="3148153140-9">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="3148153140-10">(</span><span class="ss">next_pf</span><span class="p" data-group-id="3148153140-10">)</span><span class="p" data-group-id="3148153140-9">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">GotoPF</span><span class="p" data-group-id="3148153140-11">(</span><span class="ss">next_pf</span><span class="p" data-group-id="3148153140-11">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3148153140-2">}</span></code></pre><p>Note that the very first thing done is to fetch the address to the
│ │ │  next instruction.  The reason is that it usually improves performance.</p><p>Just as a demonstration, we can add a <code class="inline">-no_prefetch</code> directive to
│ │ │ -the <code class="inline">move/2</code> instruction:</p><pre><code class="makeup erlang" translate="no"><span class="nf">move</span><span class="p" data-group-id="0225768780-1">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="0225768780-1">)</span><span class="w"> </span><span class="p" data-group-id="0225768780-2">{</span><span class="w">
│ │ │ +the <code class="inline">move/2</code> instruction:</p><pre><code class="makeup erlang" translate="no"><span class="nf">move</span><span class="p" data-group-id="4117810766-1">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="4117810766-1">)</span><span class="w"> </span><span class="p" data-group-id="4117810766-2">{</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="p">|</span><span class="w"> </span><span class="o">-</span><span class="ss">no_prefetch</span><span class="w">
│ │ │      </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">rc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0225768780-2">}</span></code></pre><p>We can see that the prefetch is no longer done:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="6785873078-1">(</span><span class="ss">move_cx</span><span class="p" data-group-id="6785873078-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6785873078-2">{</span><span class="w">
│ │ │ -  </span><span class="nf">xb</span><span class="p" data-group-id="6785873078-3">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="6785873078-4">(</span><span class="n">I</span><span class="p" data-group-id="6785873078-5">[</span><span class="mi">0</span><span class="p" data-group-id="6785873078-5">]</span><span class="p" data-group-id="6785873078-4">)</span><span class="p" data-group-id="6785873078-3">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="6785873078-6">[</span><span class="mi">1</span><span class="p" data-group-id="6785873078-6">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4117810766-2">}</span></code></pre><p>We can see that the prefetch is no longer done:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="7182888321-1">(</span><span class="ss">move_cx</span><span class="p" data-group-id="7182888321-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7182888321-2">{</span><span class="w">
│ │ │ +  </span><span class="nf">xb</span><span class="p" data-group-id="7182888321-3">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="7182888321-4">(</span><span class="n">I</span><span class="p" data-group-id="7182888321-5">[</span><span class="mi">0</span><span class="p" data-group-id="7182888321-5">]</span><span class="p" data-group-id="7182888321-4">)</span><span class="p" data-group-id="7182888321-3">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="7182888321-6">[</span><span class="mi">1</span><span class="p" data-group-id="7182888321-6">]</span><span class="p">;</span><span class="w">
│ │ │    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="6785873078-7">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="6785873078-8">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="6785873078-8">)</span><span class="p" data-group-id="6785873078-7">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">Goto</span><span class="p" data-group-id="6785873078-9">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="6785873078-9">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6785873078-2">}</span></code></pre><p>When would we want to turn off the prefetch in practice?</p><p>In instructions that will not always execute the next instruction.
│ │ │ -For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">is_atom</span><span class="p" data-group-id="6646807011-1">(</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Src</span><span class="p" data-group-id="6646807011-1">)</span><span class="w"> </span><span class="p" data-group-id="6646807011-2">{</span><span class="w">
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="6646807011-3">(</span><span class="nf">is_not_atom</span><span class="p" data-group-id="6646807011-4">(</span><span class="sc">$S</span><span class="ss">rc</span><span class="p" data-group-id="6646807011-4">)</span><span class="p" data-group-id="6646807011-3">)</span><span class="w"> </span><span class="p" data-group-id="6646807011-5">{</span><span class="w">
│ │ │ -        </span><span class="sc">$F</span><span class="n">AIL</span><span class="p" data-group-id="6646807011-6">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="6646807011-6">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6646807011-5">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6646807011-2">}</span><span class="w">
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="7182888321-7">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="7182888321-8">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="7182888321-8">)</span><span class="p" data-group-id="7182888321-7">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">Goto</span><span class="p" data-group-id="7182888321-9">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="7182888321-9">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7182888321-2">}</span></code></pre><p>When would we want to turn off the prefetch in practice?</p><p>In instructions that will not always execute the next instruction.
│ │ │ +For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">is_atom</span><span class="p" data-group-id="4618262836-1">(</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Src</span><span class="p" data-group-id="4618262836-1">)</span><span class="w"> </span><span class="p" data-group-id="4618262836-2">{</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="4618262836-3">(</span><span class="nf">is_not_atom</span><span class="p" data-group-id="4618262836-4">(</span><span class="sc">$S</span><span class="ss">rc</span><span class="p" data-group-id="4618262836-4">)</span><span class="p" data-group-id="4618262836-3">)</span><span class="w"> </span><span class="p" data-group-id="4618262836-5">{</span><span class="w">
│ │ │ +        </span><span class="sc">$F</span><span class="n">AIL</span><span class="p" data-group-id="4618262836-6">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="4618262836-6">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4618262836-5">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4618262836-2">}</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">From</span><span class="w"> </span><span class="ss">macros</span><span class="p">.</span><span class="ss">tab</span><span class="w">
│ │ │ -</span><span class="n">FAIL</span><span class="p" data-group-id="6646807011-7">(</span><span class="n">Fail</span><span class="p" data-group-id="6646807011-7">)</span><span class="w"> </span><span class="p" data-group-id="6646807011-8">{</span><span class="w">
│ │ │ +</span><span class="n">FAIL</span><span class="p" data-group-id="4618262836-7">(</span><span class="n">Fail</span><span class="p" data-group-id="4618262836-7">)</span><span class="w"> </span><span class="p" data-group-id="4618262836-8">{</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="p">|</span><span class="w"> </span><span class="o">-</span><span class="ss">no_prefetch</span><span class="w">
│ │ │ -    </span><span class="sc">$S</span><span class="n">ET_I_REL</span><span class="p" data-group-id="6646807011-9">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="6646807011-9">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">Goto</span><span class="p" data-group-id="6646807011-10">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="6646807011-10">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6646807011-8">}</span></code></pre><p><code class="inline">is_atom/2</code> may either execute the next instruction (if the second
│ │ │ -operand is an atom) or branch to the failure label.</p><p>The generated code looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="2533826916-1">(</span><span class="ss">is_atom_fx</span><span class="p" data-group-id="2533826916-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2533826916-2">{</span><span class="w">
│ │ │ -  </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="2533826916-3">(</span><span class="nf">is_not_atom</span><span class="p" data-group-id="2533826916-4">(</span><span class="nf">xb</span><span class="p" data-group-id="2533826916-5">(</span><span class="n">I</span><span class="p" data-group-id="2533826916-6">[</span><span class="mi">1</span><span class="p" data-group-id="2533826916-6">]</span><span class="p" data-group-id="2533826916-5">)</span><span class="p" data-group-id="2533826916-4">)</span><span class="p" data-group-id="2533826916-3">)</span><span class="w"> </span><span class="p" data-group-id="2533826916-7">{</span><span class="w">
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="2533826916-8">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="2533826916-9">(</span><span class="o">*</span><span class="p" data-group-id="2533826916-10">(</span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="2533826916-11">(</span><span class="nf">fb</span><span class="p" data-group-id="2533826916-12">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="2533826916-13">(</span><span class="n">I</span><span class="p" data-group-id="2533826916-14">[</span><span class="mi">0</span><span class="p" data-group-id="2533826916-14">]</span><span class="p" data-group-id="2533826916-13">)</span><span class="p" data-group-id="2533826916-12">)</span><span class="p" data-group-id="2533826916-11">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="2533826916-10">)</span><span class="p" data-group-id="2533826916-9">)</span><span class="p" data-group-id="2533826916-8">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">fb</span><span class="p" data-group-id="2533826916-15">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="2533826916-16">(</span><span class="n">I</span><span class="p" data-group-id="2533826916-17">[</span><span class="mi">0</span><span class="p" data-group-id="2533826916-17">]</span><span class="p" data-group-id="2533826916-16">)</span><span class="p" data-group-id="2533826916-15">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">Goto</span><span class="p" data-group-id="2533826916-18">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="2533826916-18">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="2533826916-7">}</span><span class="w">
│ │ │ +    </span><span class="sc">$S</span><span class="n">ET_I_REL</span><span class="p" data-group-id="4618262836-9">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="4618262836-9">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">Goto</span><span class="p" data-group-id="4618262836-10">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="4618262836-10">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4618262836-8">}</span></code></pre><p><code class="inline">is_atom/2</code> may either execute the next instruction (if the second
│ │ │ +operand is an atom) or branch to the failure label.</p><p>The generated code looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="3706833901-1">(</span><span class="ss">is_atom_fx</span><span class="p" data-group-id="3706833901-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3706833901-2">{</span><span class="w">
│ │ │ +  </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="3706833901-3">(</span><span class="nf">is_not_atom</span><span class="p" data-group-id="3706833901-4">(</span><span class="nf">xb</span><span class="p" data-group-id="3706833901-5">(</span><span class="n">I</span><span class="p" data-group-id="3706833901-6">[</span><span class="mi">1</span><span class="p" data-group-id="3706833901-6">]</span><span class="p" data-group-id="3706833901-5">)</span><span class="p" data-group-id="3706833901-4">)</span><span class="p" data-group-id="3706833901-3">)</span><span class="w"> </span><span class="p" data-group-id="3706833901-7">{</span><span class="w">
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="3706833901-8">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="3706833901-9">(</span><span class="o">*</span><span class="p" data-group-id="3706833901-10">(</span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="3706833901-11">(</span><span class="nf">fb</span><span class="p" data-group-id="3706833901-12">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="3706833901-13">(</span><span class="n">I</span><span class="p" data-group-id="3706833901-14">[</span><span class="mi">0</span><span class="p" data-group-id="3706833901-14">]</span><span class="p" data-group-id="3706833901-13">)</span><span class="p" data-group-id="3706833901-12">)</span><span class="p" data-group-id="3706833901-11">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="3706833901-10">)</span><span class="p" data-group-id="3706833901-9">)</span><span class="p" data-group-id="3706833901-8">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">fb</span><span class="p" data-group-id="3706833901-15">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="3706833901-16">(</span><span class="n">I</span><span class="p" data-group-id="3706833901-17">[</span><span class="mi">0</span><span class="p" data-group-id="3706833901-17">]</span><span class="p" data-group-id="3706833901-16">)</span><span class="p" data-group-id="3706833901-15">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">Goto</span><span class="p" data-group-id="3706833901-18">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="3706833901-18">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="3706833901-7">}</span><span class="w">
│ │ │    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="2533826916-19">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="2533826916-20">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="2533826916-20">)</span><span class="p" data-group-id="2533826916-19">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">Goto</span><span class="p" data-group-id="2533826916-21">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="2533826916-21">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2533826916-2">}</span></code></pre><h5>The -no_next directive</h5><p>Next we will look at when the <code class="inline">-no_next</code> directive can be used.  Here
│ │ │ -is the <code class="inline">jump/1</code> instruction:</p><pre><code class="makeup erlang" translate="no"><span class="nf">jump</span><span class="p" data-group-id="1487503520-1">(</span><span class="n">Fail</span><span class="p" data-group-id="1487503520-1">)</span><span class="w"> </span><span class="p" data-group-id="1487503520-2">{</span><span class="w">
│ │ │ -    </span><span class="sc">$J</span><span class="n">UMP</span><span class="p" data-group-id="1487503520-3">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="1487503520-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1487503520-2">}</span><span class="w">
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="3706833901-19">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="3706833901-20">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="3706833901-20">)</span><span class="p" data-group-id="3706833901-19">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">Goto</span><span class="p" data-group-id="3706833901-21">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="3706833901-21">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3706833901-2">}</span></code></pre><h5>The -no_next directive</h5><p>Next we will look at when the <code class="inline">-no_next</code> directive can be used.  Here
│ │ │ +is the <code class="inline">jump/1</code> instruction:</p><pre><code class="makeup erlang" translate="no"><span class="nf">jump</span><span class="p" data-group-id="6784935055-1">(</span><span class="n">Fail</span><span class="p" data-group-id="6784935055-1">)</span><span class="w"> </span><span class="p" data-group-id="6784935055-2">{</span><span class="w">
│ │ │ +    </span><span class="sc">$J</span><span class="n">UMP</span><span class="p" data-group-id="6784935055-3">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="6784935055-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6784935055-2">}</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">From</span><span class="w"> </span><span class="ss">macros</span><span class="p">.</span><span class="ss">tab</span><span class="w">
│ │ │ -</span><span class="n">JUMP</span><span class="p" data-group-id="1487503520-4">(</span><span class="n">Fail</span><span class="p" data-group-id="1487503520-4">)</span><span class="w"> </span><span class="p" data-group-id="1487503520-5">{</span><span class="w">
│ │ │ +</span><span class="n">JUMP</span><span class="p" data-group-id="6784935055-4">(</span><span class="n">Fail</span><span class="p" data-group-id="6784935055-4">)</span><span class="w"> </span><span class="p" data-group-id="6784935055-5">{</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="p">|</span><span class="w"> </span><span class="o">-</span><span class="ss">no_next</span><span class="w">
│ │ │ -    </span><span class="sc">$S</span><span class="n">ET_I_REL</span><span class="p" data-group-id="1487503520-6">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="1487503520-6">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">Goto</span><span class="p" data-group-id="1487503520-7">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="1487503520-7">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1487503520-5">}</span></code></pre><p>The generated code looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="7667086358-1">(</span><span class="ss">jump_f</span><span class="p" data-group-id="7667086358-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7667086358-2">{</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="7667086358-3">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="7667086358-4">(</span><span class="o">*</span><span class="p" data-group-id="7667086358-5">(</span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="7667086358-6">(</span><span class="nf">fb</span><span class="p" data-group-id="7667086358-7">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="7667086358-8">(</span><span class="n">I</span><span class="p" data-group-id="7667086358-9">[</span><span class="mi">0</span><span class="p" data-group-id="7667086358-9">]</span><span class="p" data-group-id="7667086358-8">)</span><span class="p" data-group-id="7667086358-7">)</span><span class="p" data-group-id="7667086358-6">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="7667086358-5">)</span><span class="p" data-group-id="7667086358-4">)</span><span class="p" data-group-id="7667086358-3">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">fb</span><span class="p" data-group-id="7667086358-10">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="7667086358-11">(</span><span class="n">I</span><span class="p" data-group-id="7667086358-12">[</span><span class="mi">0</span><span class="p" data-group-id="7667086358-12">]</span><span class="p" data-group-id="7667086358-11">)</span><span class="p" data-group-id="7667086358-10">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">Goto</span><span class="p" data-group-id="7667086358-13">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="7667086358-13">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7667086358-2">}</span></code></pre><p>If we remove the <code class="inline">-no_next</code> directive, the code would look like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="9455162345-1">(</span><span class="ss">jump_f</span><span class="p" data-group-id="9455162345-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9455162345-2">{</span><span class="w">
│ │ │ -  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="9455162345-3">(</span><span class="n">I</span><span class="p" data-group-id="9455162345-4">[</span><span class="mi">1</span><span class="p" data-group-id="9455162345-4">]</span><span class="p" data-group-id="9455162345-3">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="9455162345-5">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="9455162345-6">(</span><span class="o">*</span><span class="p" data-group-id="9455162345-7">(</span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="9455162345-8">(</span><span class="nf">fb</span><span class="p" data-group-id="9455162345-9">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="9455162345-10">(</span><span class="n">I</span><span class="p" data-group-id="9455162345-11">[</span><span class="mi">0</span><span class="p" data-group-id="9455162345-11">]</span><span class="p" data-group-id="9455162345-10">)</span><span class="p" data-group-id="9455162345-9">)</span><span class="p" data-group-id="9455162345-8">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="9455162345-7">)</span><span class="p" data-group-id="9455162345-6">)</span><span class="p" data-group-id="9455162345-5">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">fb</span><span class="p" data-group-id="9455162345-12">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="9455162345-13">(</span><span class="n">I</span><span class="p" data-group-id="9455162345-14">[</span><span class="mi">0</span><span class="p" data-group-id="9455162345-14">]</span><span class="p" data-group-id="9455162345-13">)</span><span class="p" data-group-id="9455162345-12">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">Goto</span><span class="p" data-group-id="9455162345-15">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="9455162345-15">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="sc">$S</span><span class="n">ET_I_REL</span><span class="p" data-group-id="6784935055-6">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="6784935055-6">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">Goto</span><span class="p" data-group-id="6784935055-7">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="6784935055-7">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6784935055-5">}</span></code></pre><p>The generated code looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="7599674559-1">(</span><span class="ss">jump_f</span><span class="p" data-group-id="7599674559-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7599674559-2">{</span><span class="w">
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="7599674559-3">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="7599674559-4">(</span><span class="o">*</span><span class="p" data-group-id="7599674559-5">(</span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="7599674559-6">(</span><span class="nf">fb</span><span class="p" data-group-id="7599674559-7">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="7599674559-8">(</span><span class="n">I</span><span class="p" data-group-id="7599674559-9">[</span><span class="mi">0</span><span class="p" data-group-id="7599674559-9">]</span><span class="p" data-group-id="7599674559-8">)</span><span class="p" data-group-id="7599674559-7">)</span><span class="p" data-group-id="7599674559-6">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="7599674559-5">)</span><span class="p" data-group-id="7599674559-4">)</span><span class="p" data-group-id="7599674559-3">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">fb</span><span class="p" data-group-id="7599674559-10">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="7599674559-11">(</span><span class="n">I</span><span class="p" data-group-id="7599674559-12">[</span><span class="mi">0</span><span class="p" data-group-id="7599674559-12">]</span><span class="p" data-group-id="7599674559-11">)</span><span class="p" data-group-id="7599674559-10">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">Goto</span><span class="p" data-group-id="7599674559-13">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="7599674559-13">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7599674559-2">}</span></code></pre><p>If we remove the <code class="inline">-no_next</code> directive, the code would look like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="5756087908-1">(</span><span class="ss">jump_f</span><span class="p" data-group-id="5756087908-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5756087908-2">{</span><span class="w">
│ │ │ +  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="5756087908-3">(</span><span class="n">I</span><span class="p" data-group-id="5756087908-4">[</span><span class="mi">1</span><span class="p" data-group-id="5756087908-4">]</span><span class="p" data-group-id="5756087908-3">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="5756087908-5">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="5756087908-6">(</span><span class="o">*</span><span class="p" data-group-id="5756087908-7">(</span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="5756087908-8">(</span><span class="nf">fb</span><span class="p" data-group-id="5756087908-9">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="5756087908-10">(</span><span class="n">I</span><span class="p" data-group-id="5756087908-11">[</span><span class="mi">0</span><span class="p" data-group-id="5756087908-11">]</span><span class="p" data-group-id="5756087908-10">)</span><span class="p" data-group-id="5756087908-9">)</span><span class="p" data-group-id="5756087908-8">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="5756087908-7">)</span><span class="p" data-group-id="5756087908-6">)</span><span class="p" data-group-id="5756087908-5">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">fb</span><span class="p" data-group-id="5756087908-12">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="5756087908-13">(</span><span class="n">I</span><span class="p" data-group-id="5756087908-14">[</span><span class="mi">0</span><span class="p" data-group-id="5756087908-14">]</span><span class="p" data-group-id="5756087908-13">)</span><span class="p" data-group-id="5756087908-12">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">Goto</span><span class="p" data-group-id="5756087908-15">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="5756087908-15">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="9455162345-16">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="9455162345-17">(</span><span class="ss">next_pf</span><span class="p" data-group-id="9455162345-17">)</span><span class="p" data-group-id="9455162345-16">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">GotoPF</span><span class="p" data-group-id="9455162345-18">(</span><span class="ss">next_pf</span><span class="p" data-group-id="9455162345-18">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9455162345-2">}</span></code></pre><p>In the end, the C compiler will probably optimize this code to the
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="5756087908-16">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="5756087908-17">(</span><span class="ss">next_pf</span><span class="p" data-group-id="5756087908-17">)</span><span class="p" data-group-id="5756087908-16">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">GotoPF</span><span class="p" data-group-id="5756087908-18">(</span><span class="ss">next_pf</span><span class="p" data-group-id="5756087908-18">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5756087908-2">}</span></code></pre><p>In the end, the C compiler will probably optimize this code to the
│ │ │  same native code as the first version, but the first version is certainly
│ │ │  much easier to read for human readers.</p><h4>Macros in the macros.tab file</h4><p>The file <code class="inline">macros.tab</code> contains many useful macros.  When implementing
│ │ │  new instructions it is good practice to look through <code class="inline">macros.tab</code> to
│ │ │  see if any of existing macros can be used rather than re-inventing
│ │ │  the wheel.</p><p>We will describe a few of the most useful macros here.</p><p><a href="" id="the-GC_REGEXP-definition"></a></p><h5>The GC_REGEXP definition</h5><p>The following line defines a regular expression that will recognize
│ │ │  a call to a function that does a garbage collection:</p><pre><code class="makeup erlang" translate="no"><span class="w"> </span><span class="n">GC_REGEXP</span><span class="o">=</span><span class="ss">erts_garbage_collect</span><span class="p">|</span><span class="ss">erts_gc</span><span class="p">|</span><span class="n">GcBifFunction</span><span class="p">;</span></code></pre><p>The purpose is that <strong>beam_makeops</strong> can verify that an instruction
│ │ │  that does a garbage collection and has an <code class="inline">d</code> operand uses the
│ │ │  <code class="inline">$REFRESH_GEN_DEST()</code> macro.</p><p>If you need to define a new function that does garbage collection,
│ │ │  you should give it the prefix <code class="inline">erts_gc_</code>.  If that is not possible
│ │ │  you should update the regular expression so that it will match your
│ │ │ -new function.</p><h5>FAIL(Fail)</h5><p>Branch to <code class="inline">$Fail</code>.  Will suppress prefetch (<code class="inline">-no_prefetch</code>).  Typical use:</p><pre><code class="makeup erlang" translate="no"><span class="nf">is_nonempty_list</span><span class="p" data-group-id="8653331118-1">(</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Src</span><span class="p" data-group-id="8653331118-1">)</span><span class="w"> </span><span class="p" data-group-id="8653331118-2">{</span><span class="w">
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="8653331118-3">(</span><span class="nf">is_not_list</span><span class="p" data-group-id="8653331118-4">(</span><span class="sc">$S</span><span class="ss">rc</span><span class="p" data-group-id="8653331118-4">)</span><span class="p" data-group-id="8653331118-3">)</span><span class="w"> </span><span class="p" data-group-id="8653331118-5">{</span><span class="w">
│ │ │ -        </span><span class="sc">$F</span><span class="n">AIL</span><span class="p" data-group-id="8653331118-6">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="8653331118-6">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8653331118-5">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8653331118-2">}</span></code></pre><h5>JUMP(Fail)</h5><p>Branch to <code class="inline">$Fail</code>.  Suppresses generation of dispatch of the next
│ │ │ -instruction (<code class="inline">-no_next</code>).  Typical use:</p><pre><code class="makeup erlang" translate="no"><span class="nf">jump</span><span class="p" data-group-id="4655354957-1">(</span><span class="n">Fail</span><span class="p" data-group-id="4655354957-1">)</span><span class="w"> </span><span class="p" data-group-id="4655354957-2">{</span><span class="w">
│ │ │ -    </span><span class="sc">$J</span><span class="n">UMP</span><span class="p" data-group-id="4655354957-3">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="4655354957-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4655354957-2">}</span></code></pre><h5>GC_TEST(NeedStack, NeedHeap, Live)</h5><p><code class="inline">$GC_TEST(NeedStack, NeedHeap, Live)</code> tests that given amount of
│ │ │ +new function.</p><h5>FAIL(Fail)</h5><p>Branch to <code class="inline">$Fail</code>.  Will suppress prefetch (<code class="inline">-no_prefetch</code>).  Typical use:</p><pre><code class="makeup erlang" translate="no"><span class="nf">is_nonempty_list</span><span class="p" data-group-id="2044602297-1">(</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Src</span><span class="p" data-group-id="2044602297-1">)</span><span class="w"> </span><span class="p" data-group-id="2044602297-2">{</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="2044602297-3">(</span><span class="nf">is_not_list</span><span class="p" data-group-id="2044602297-4">(</span><span class="sc">$S</span><span class="ss">rc</span><span class="p" data-group-id="2044602297-4">)</span><span class="p" data-group-id="2044602297-3">)</span><span class="w"> </span><span class="p" data-group-id="2044602297-5">{</span><span class="w">
│ │ │ +        </span><span class="sc">$F</span><span class="n">AIL</span><span class="p" data-group-id="2044602297-6">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="2044602297-6">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2044602297-5">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2044602297-2">}</span></code></pre><h5>JUMP(Fail)</h5><p>Branch to <code class="inline">$Fail</code>.  Suppresses generation of dispatch of the next
│ │ │ +instruction (<code class="inline">-no_next</code>).  Typical use:</p><pre><code class="makeup erlang" translate="no"><span class="nf">jump</span><span class="p" data-group-id="8482877791-1">(</span><span class="n">Fail</span><span class="p" data-group-id="8482877791-1">)</span><span class="w"> </span><span class="p" data-group-id="8482877791-2">{</span><span class="w">
│ │ │ +    </span><span class="sc">$J</span><span class="n">UMP</span><span class="p" data-group-id="8482877791-3">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="8482877791-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8482877791-2">}</span></code></pre><h5>GC_TEST(NeedStack, NeedHeap, Live)</h5><p><code class="inline">$GC_TEST(NeedStack, NeedHeap, Live)</code> tests that given amount of
│ │ │  stack space and heap space is available.  If not it will do a
│ │ │ -garbage collection.  Typical use:</p><pre><code class="makeup erlang" translate="no"><span class="nf">test_heap</span><span class="p" data-group-id="7169366351-1">(</span><span class="n">Nh</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p" data-group-id="7169366351-1">)</span><span class="w"> </span><span class="p" data-group-id="7169366351-2">{</span><span class="w">
│ │ │ -    </span><span class="sc">$G</span><span class="n">C_TEST</span><span class="p" data-group-id="7169366351-3">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="sc">$N</span><span class="ss">h</span><span class="p">,</span><span class="w"> </span><span class="sc">$L</span><span class="ss">ive</span><span class="p" data-group-id="7169366351-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7169366351-2">}</span></code></pre><h5>AH(NeedStack, NeedHeap, Live)</h5><p><code class="inline">AH(NeedStack, NeedHeap, Live)</code> allocates a stack frame and
│ │ │ +garbage collection.  Typical use:</p><pre><code class="makeup erlang" translate="no"><span class="nf">test_heap</span><span class="p" data-group-id="2304118669-1">(</span><span class="n">Nh</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p" data-group-id="2304118669-1">)</span><span class="w"> </span><span class="p" data-group-id="2304118669-2">{</span><span class="w">
│ │ │ +    </span><span class="sc">$G</span><span class="n">C_TEST</span><span class="p" data-group-id="2304118669-3">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="sc">$N</span><span class="ss">h</span><span class="p">,</span><span class="w"> </span><span class="sc">$L</span><span class="ss">ive</span><span class="p" data-group-id="2304118669-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2304118669-2">}</span></code></pre><h5>AH(NeedStack, NeedHeap, Live)</h5><p><code class="inline">AH(NeedStack, NeedHeap, Live)</code> allocates a stack frame and
│ │ │  optionally additional heap space.</p><h4>Pre-defined macros and variables</h4><p><strong>beam_makeops</strong> defines several built-in macros and pre-bound variables.</p><h5>The NEXT_INSTRUCTION pre-bound variable</h5><p>The NEXT_INSTRUCTION is a pre-bound variable that is available in
│ │ │ -all instructions.  It expands to the address of the next instruction.</p><p>Here is an example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">i_call</span><span class="p" data-group-id="6179528204-1">(</span><span class="n">CallDest</span><span class="p" data-group-id="6179528204-1">)</span><span class="w"> </span><span class="p" data-group-id="6179528204-2">{</span><span class="w">
│ │ │ +all instructions.  It expands to the address of the next instruction.</p><p>Here is an example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">i_call</span><span class="p" data-group-id="6584578521-1">(</span><span class="n">CallDest</span><span class="p" data-group-id="6584578521-1">)</span><span class="w"> </span><span class="p" data-group-id="6584578521-2">{</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="p">|</span><span class="w"> </span><span class="o">-</span><span class="ss">no_next</span><span class="w">
│ │ │ -    </span><span class="sc">$S</span><span class="n">AVE_CONTINUATION_POINTER</span><span class="p" data-group-id="6179528204-3">(</span><span class="sc">$N</span><span class="n">EXT_INSTRUCTION</span><span class="p" data-group-id="6179528204-3">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="sc">$D</span><span class="n">ISPATCH_REL</span><span class="p" data-group-id="6179528204-4">(</span><span class="sc">$C</span><span class="ss">allDest</span><span class="p" data-group-id="6179528204-4">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6179528204-2">}</span></code></pre><p>When calling a function, the return address is first stored in <code class="inline">E[0]</code>
│ │ │ +    </span><span class="sc">$S</span><span class="n">AVE_CONTINUATION_POINTER</span><span class="p" data-group-id="6584578521-3">(</span><span class="sc">$N</span><span class="n">EXT_INSTRUCTION</span><span class="p" data-group-id="6584578521-3">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="sc">$D</span><span class="n">ISPATCH_REL</span><span class="p" data-group-id="6584578521-4">(</span><span class="sc">$C</span><span class="ss">allDest</span><span class="p" data-group-id="6584578521-4">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6584578521-2">}</span></code></pre><p>When calling a function, the return address is first stored in <code class="inline">E[0]</code>
│ │ │  (using the <code class="inline">$SAVE_CONTINUATION_POINTER()</code> macro), and then control is
│ │ │ -transferred to the callee.  Here is the generated code:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="5617282396-1">(</span><span class="ss">i_call_f</span><span class="p" data-group-id="5617282396-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5617282396-2">{</span><span class="w">
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="5617282396-3">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="5617282396-4">(</span><span class="o">*</span><span class="p" data-group-id="5617282396-5">(</span><span class="n">I</span><span class="o">+</span><span class="mi">2</span><span class="p" data-group-id="5617282396-5">)</span><span class="p" data-group-id="5617282396-4">)</span><span class="p" data-group-id="5617282396-3">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="o">*</span><span class="n">E</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5617282396-6">(</span><span class="n">BeamInstr</span><span class="p" data-group-id="5617282396-6">)</span><span class="w"> </span><span class="p" data-group-id="5617282396-7">(</span><span class="n">I</span><span class="o">+</span><span class="mi">2</span><span class="p" data-group-id="5617282396-7">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ +transferred to the callee.  Here is the generated code:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="8252964452-1">(</span><span class="ss">i_call_f</span><span class="p" data-group-id="8252964452-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8252964452-2">{</span><span class="w">
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="8252964452-3">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="8252964452-4">(</span><span class="o">*</span><span class="p" data-group-id="8252964452-5">(</span><span class="n">I</span><span class="o">+</span><span class="mi">2</span><span class="p" data-group-id="8252964452-5">)</span><span class="p" data-group-id="8252964452-4">)</span><span class="p" data-group-id="8252964452-3">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="o">*</span><span class="n">E</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8252964452-6">(</span><span class="n">BeamInstr</span><span class="p" data-group-id="8252964452-6">)</span><span class="w"> </span><span class="p" data-group-id="8252964452-7">(</span><span class="n">I</span><span class="o">+</span><span class="mi">2</span><span class="p" data-group-id="8252964452-7">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │      </span><span class="o">/</span><span class="o">*</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="ss">dispatch</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">intentionally</span><span class="w"> </span><span class="ss">left</span><span class="w"> </span><span class="ss">out</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="o">*</span><span class="o">/</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5617282396-2">}</span></code></pre><p>We can see that that <code class="inline">$NEXT_INSTRUCTION</code> has been expanded to <code class="inline">I+2</code>.
│ │ │ +</span><span class="p" data-group-id="8252964452-2">}</span></code></pre><p>We can see that that <code class="inline">$NEXT_INSTRUCTION</code> has been expanded to <code class="inline">I+2</code>.
│ │ │  That makes sense since the size of the <code class="inline">i_call_f/1</code> instruction is
│ │ │  two words.</p><h5>The IP_ADJUSTMENT pre-bound variable</h5><p><code class="inline">$IP_ADJUSTMENT</code> is usually 0.  In a few combined instructions
│ │ │  (described below) it can be non-zero.  It is used like this
│ │ │ -in <code class="inline">macros.tab</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">SET_I_REL</span><span class="p" data-group-id="6947493803-1">(</span><span class="n">Offset</span><span class="p" data-group-id="6947493803-1">)</span><span class="w"> </span><span class="p" data-group-id="6947493803-2">{</span><span class="w">
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="6947493803-3">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="6947493803-4">(</span><span class="o">*</span><span class="p" data-group-id="6947493803-5">(</span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="6947493803-6">(</span><span class="sc">$O</span><span class="ss">ffset</span><span class="p" data-group-id="6947493803-6">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">$I</span><span class="n">P_ADJUSTMENT</span><span class="p" data-group-id="6947493803-5">)</span><span class="p" data-group-id="6947493803-4">)</span><span class="p" data-group-id="6947493803-3">)</span><span class="p">;</span><span class="w">
│ │ │ +in <code class="inline">macros.tab</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">SET_I_REL</span><span class="p" data-group-id="8642619268-1">(</span><span class="n">Offset</span><span class="p" data-group-id="8642619268-1">)</span><span class="w"> </span><span class="p" data-group-id="8642619268-2">{</span><span class="w">
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="8642619268-3">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="8642619268-4">(</span><span class="o">*</span><span class="p" data-group-id="8642619268-5">(</span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="8642619268-6">(</span><span class="sc">$O</span><span class="ss">ffset</span><span class="p" data-group-id="8642619268-6">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">$I</span><span class="n">P_ADJUSTMENT</span><span class="p" data-group-id="8642619268-5">)</span><span class="p" data-group-id="8642619268-4">)</span><span class="p" data-group-id="8642619268-3">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="sc">$O</span><span class="ss">ffset</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">$I</span><span class="n">P_ADJUSTMENT</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6947493803-2">}</span></code></pre><p>Avoid using <code class="inline">IP_ADJUSTMENT</code> directly.  Use <code class="inline">SET_I_REL()</code> or
│ │ │ +</span><span class="p" data-group-id="8642619268-2">}</span></code></pre><p>Avoid using <code class="inline">IP_ADJUSTMENT</code> directly.  Use <code class="inline">SET_I_REL()</code> or
│ │ │  one of the macros that invoke such as <code class="inline">FAIL()</code> or <code class="inline">JUMP()</code>
│ │ │  defined in <code class="inline">macros.tab</code>.</p><h4>Pre-defined macro functions</h4><h5>The IF() macro</h5><p><code class="inline">$IF(Expr, IfTrue, IfFalse)</code> evaluates <code class="inline">Expr</code>, which must be a valid
│ │ │  Perl expression (which for simple numeric expressions have the same
│ │ │  syntax as C).  If <code class="inline">Expr</code> evaluates to 0, the entire <code class="inline">IF()</code> expression will be
│ │ │  replaced with <code class="inline">IfFalse</code>, otherwise it will be replaced with <code class="inline">IfTrue</code>.</p><p>See the description of <code class="inline">OPERAND_POSITION()</code> for an example.</p><h5>The OPERAND_POSITION() macro</h5><p><code class="inline">$OPERAND_POSITION(Expr)</code> returns the position for <code class="inline">Expr</code>, if
│ │ │  <code class="inline">Expr</code> is an operand that is not packed.  The first operand is
│ │ │ -at position 1.</p><p>Returns 0 otherwise.</p><p>This macro could be used like this in order to share code:</p><pre><code class="makeup erlang" translate="no"><span class="n">FAIL</span><span class="p" data-group-id="7628357269-1">(</span><span class="n">Fail</span><span class="p" data-group-id="7628357269-1">)</span><span class="w"> </span><span class="p" data-group-id="7628357269-2">{</span><span class="w">
│ │ │ +at position 1.</p><p>Returns 0 otherwise.</p><p>This macro could be used like this in order to share code:</p><pre><code class="makeup erlang" translate="no"><span class="n">FAIL</span><span class="p" data-group-id="2724637453-1">(</span><span class="n">Fail</span><span class="p" data-group-id="2724637453-1">)</span><span class="w"> </span><span class="p" data-group-id="2724637453-2">{</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="p">|</span><span class="w"> </span><span class="o">-</span><span class="ss">no_prefetch</span><span class="w">
│ │ │ -    </span><span class="sc">$I</span><span class="n">F</span><span class="p" data-group-id="7628357269-3">(</span><span class="sc">$O</span><span class="n">PERAND_POSITION</span><span class="p" data-group-id="7628357269-4">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="7628357269-4">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="sc">$I</span><span class="n">P_ADJUSTMENT</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="sc">$I</span><span class="n">F</span><span class="p" data-group-id="2724637453-3">(</span><span class="sc">$O</span><span class="n">PERAND_POSITION</span><span class="p" data-group-id="2724637453-4">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="2724637453-4">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="sc">$I</span><span class="n">P_ADJUSTMENT</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="ss">goto</span><span class="w"> </span><span class="ss">common_jump</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="sc">$D</span><span class="n">O_JUMP</span><span class="p" data-group-id="7628357269-5">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="7628357269-5">)</span><span class="p" data-group-id="7628357269-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7628357269-2">}</span><span class="w">
│ │ │ +        </span><span class="sc">$D</span><span class="n">O_JUMP</span><span class="p" data-group-id="2724637453-5">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="2724637453-5">)</span><span class="p" data-group-id="2724637453-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2724637453-2">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">DO_JUMP</span><span class="p" data-group-id="7628357269-6">(</span><span class="n">Fail</span><span class="p" data-group-id="7628357269-6">)</span><span class="w"> </span><span class="p" data-group-id="7628357269-7">{</span><span class="w">
│ │ │ -    </span><span class="sc">$S</span><span class="n">ET_I_REL</span><span class="p" data-group-id="7628357269-8">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="7628357269-8">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">Goto</span><span class="p" data-group-id="7628357269-9">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="7628357269-9">)</span><span class="p">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7628357269-7">}</span><span class="w">
│ │ │ +</span><span class="n">DO_JUMP</span><span class="p" data-group-id="2724637453-6">(</span><span class="n">Fail</span><span class="p" data-group-id="2724637453-6">)</span><span class="w"> </span><span class="p" data-group-id="2724637453-7">{</span><span class="w">
│ │ │ +    </span><span class="sc">$S</span><span class="n">ET_I_REL</span><span class="p" data-group-id="2724637453-8">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="2724637453-8">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">Goto</span><span class="p" data-group-id="2724637453-9">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="2724637453-9">)</span><span class="p">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2724637453-7">}</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">In</span><span class="w"> </span><span class="ss">beam_emu</span><span class="p">.</span><span class="nc">c</span><span class="p">:</span><span class="w">
│ │ │  </span><span class="nc">common_jump</span><span class="p">:</span><span class="w">
│ │ │ -   </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="7628357269-10">[</span><span class="mi">1</span><span class="p" data-group-id="7628357269-10">]</span><span class="p">;</span><span class="w">
│ │ │ -   </span><span class="n">Goto</span><span class="p" data-group-id="7628357269-11">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="7628357269-11">)</span><span class="p">)</span><span class="p">;</span></code></pre><h4>The $REFRESH_GEN_DEST() macro</h4><p>When a specific instruction has a <code class="inline">d</code> operand, early during execution
│ │ │ +   </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="2724637453-10">[</span><span class="mi">1</span><span class="p" data-group-id="2724637453-10">]</span><span class="p">;</span><span class="w">
│ │ │ +   </span><span class="n">Goto</span><span class="p" data-group-id="2724637453-11">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="2724637453-11">)</span><span class="p">)</span><span class="p">;</span></code></pre><h4>The $REFRESH_GEN_DEST() macro</h4><p>When a specific instruction has a <code class="inline">d</code> operand, early during execution
│ │ │  of the instruction, a pointer will be initialized to point to the X or
│ │ │  Y register in question.</p><p>If there is a garbage collection before the result is stored,
│ │ │  the stack will move and if the <code class="inline">d</code> operand referred to a Y
│ │ │  register, the pointer will no longer be valid.  (Y registers are
│ │ │  stored on the stack.)</p><p>In those circumstances, <code class="inline">$REFRESH_GEN_DEST()</code> must be invoked
│ │ │  to set up the pointer again. <strong>beam_makeops</strong> will notice
│ │ │  if there is a call to a function that does a garbage collection and
│ │ │  <code class="inline">$REFRESH_GEN_DEST()</code> is not called.</p><p>Here is a complete example.  The <code class="inline">new_map</code> instruction is defined
│ │ │ -like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">new_map</span><span class="w"> </span><span class="ss">d</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="n">I</span></code></pre><p>It is implemented like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">new_map</span><span class="p" data-group-id="1523729265-1">(</span><span class="n">Dst</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p" data-group-id="1523729265-1">)</span><span class="w"> </span><span class="p" data-group-id="1523729265-2">{</span><span class="w">
│ │ │ +like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">new_map</span><span class="w"> </span><span class="ss">d</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="n">I</span></code></pre><p>It is implemented like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">new_map</span><span class="p" data-group-id="9770649844-1">(</span><span class="n">Dst</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p" data-group-id="9770649844-1">)</span><span class="w"> </span><span class="p" data-group-id="9770649844-2">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">res</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │      </span><span class="n">HEAVY_SWAPOUT</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erts_gc_new_map</span><span class="p" data-group-id="1523729265-3">(</span><span class="ss">c_p</span><span class="p">,</span><span class="w"> </span><span class="ss">reg</span><span class="p">,</span><span class="w"> </span><span class="sc">$L</span><span class="ss">ive</span><span class="p">,</span><span class="w"> </span><span class="sc">$N</span><span class="p">,</span><span class="w"> </span><span class="sc">$N</span><span class="n">EXT_INSTRUCTION</span><span class="p" data-group-id="1523729265-3">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erts_gc_new_map</span><span class="p" data-group-id="9770649844-3">(</span><span class="ss">c_p</span><span class="p">,</span><span class="w"> </span><span class="ss">reg</span><span class="p">,</span><span class="w"> </span><span class="sc">$L</span><span class="ss">ive</span><span class="p">,</span><span class="w"> </span><span class="sc">$N</span><span class="p">,</span><span class="w"> </span><span class="sc">$N</span><span class="n">EXT_INSTRUCTION</span><span class="p" data-group-id="9770649844-3">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">HEAVY_SWAPIN</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="sc">$R</span><span class="n">EFRESH_GEN_DEST</span><span class="p" data-group-id="1523729265-4">(</span><span class="p" data-group-id="1523729265-4">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="sc">$R</span><span class="n">EFRESH_GEN_DEST</span><span class="p" data-group-id="9770649844-4">(</span><span class="p" data-group-id="9770649844-4">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">res</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="sc">$N</span><span class="n">EXT</span><span class="p" data-group-id="1523729265-5">(</span><span class="sc">$N</span><span class="n">EXT_INSTRUCTION</span><span class="o">+</span><span class="sc">$N</span><span class="p" data-group-id="1523729265-5">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1523729265-2">}</span></code></pre><p>If we have forgotten the <code class="inline">$REFRESH_GEN_DEST()</code> there would be a message
│ │ │ -similar to this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">pointer</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">destination</span><span class="w"> </span><span class="nb">register</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">invalid</span><span class="w"> </span><span class="k">after</span><span class="w"> </span><span class="n">GC</span><span class="w"> </span><span class="o">--</span><span class="w"> </span><span class="ss">use</span><span class="w"> </span><span class="sc">$R</span><span class="n">EFRESH_GEN_DEST</span><span class="p" data-group-id="8414765548-1">(</span><span class="p" data-group-id="8414765548-1">)</span><span class="w">
│ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">body</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="ss">new_map</span><span class="w"> </span><span class="ss">at</span><span class="w"> </span><span class="ss">beam</span><span class="o">/</span><span class="ss">map_instrs</span><span class="p">.</span><span class="nf">tab</span><span class="p" data-group-id="8414765548-2">(</span><span class="mi">30</span><span class="p" data-group-id="8414765548-2">)</span></code></pre><h4>Variable number of operands</h4><p>Here follows an example of how to handle an instruction with a variable number
│ │ │ +    </span><span class="sc">$N</span><span class="n">EXT</span><span class="p" data-group-id="9770649844-5">(</span><span class="sc">$N</span><span class="n">EXT_INSTRUCTION</span><span class="o">+</span><span class="sc">$N</span><span class="p" data-group-id="9770649844-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9770649844-2">}</span></code></pre><p>If we have forgotten the <code class="inline">$REFRESH_GEN_DEST()</code> there would be a message
│ │ │ +similar to this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">pointer</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">destination</span><span class="w"> </span><span class="nb">register</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">invalid</span><span class="w"> </span><span class="k">after</span><span class="w"> </span><span class="n">GC</span><span class="w"> </span><span class="o">--</span><span class="w"> </span><span class="ss">use</span><span class="w"> </span><span class="sc">$R</span><span class="n">EFRESH_GEN_DEST</span><span class="p" data-group-id="1098127735-1">(</span><span class="p" data-group-id="1098127735-1">)</span><span class="w">
│ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">body</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="ss">new_map</span><span class="w"> </span><span class="ss">at</span><span class="w"> </span><span class="ss">beam</span><span class="o">/</span><span class="ss">map_instrs</span><span class="p">.</span><span class="nf">tab</span><span class="p" data-group-id="1098127735-2">(</span><span class="mi">30</span><span class="p" data-group-id="1098127735-2">)</span></code></pre><h4>Variable number of operands</h4><p>Here follows an example of how to handle an instruction with a variable number
│ │ │  of operands for the interpreter.  Here is the instruction definition in <code class="inline">emu/ops.tab</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">put_tuple2</span><span class="w"> </span><span class="ss">xy</span><span class="w"> </span><span class="n">I</span><span class="w"> </span><span class="o">*</span></code></pre><p>For the interpreter, the <code class="inline">*</code> is optional, because it does not effect code generation
│ │ │  in any way. However, it is recommended to include it to make it clear for human readers
│ │ │  that there is a variable number of operands.</p><p>Use the <code class="inline">$NEXT_INSTRUCTION</code> macro to obtain a pointer to the first of the variable
│ │ │ -operands.</p><p>Here is the implementation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">put_tuple2</span><span class="p" data-group-id="3798746903-1">(</span><span class="n">Dst</span><span class="p">,</span><span class="w"> </span><span class="n">Arity</span><span class="p" data-group-id="3798746903-1">)</span><span class="w"> </span><span class="p" data-group-id="3798746903-2">{</span><span class="w">
│ │ │ +operands.</p><p>Here is the implementation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">put_tuple2</span><span class="p" data-group-id="5147032230-1">(</span><span class="n">Dst</span><span class="p">,</span><span class="w"> </span><span class="n">Arity</span><span class="p" data-group-id="5147032230-1">)</span><span class="w"> </span><span class="p" data-group-id="5147032230-2">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="o">*</span><span class="w"> </span><span class="ss">hp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">HTOP</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">arity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$A</span><span class="ss">rity</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">Eterm</span><span class="o">*</span><span class="w"> </span><span class="ss">dst_ptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="err">&amp;</span><span class="p" data-group-id="3798746903-3">(</span><span class="sc">$D</span><span class="ss">st</span><span class="p" data-group-id="3798746903-3">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">Eterm</span><span class="o">*</span><span class="w"> </span><span class="ss">dst_ptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="err">&amp;</span><span class="p" data-group-id="5147032230-3">(</span><span class="sc">$D</span><span class="ss">st</span><span class="p" data-group-id="5147032230-3">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="p">|</span><span class="w"> </span><span class="o">-</span><span class="ss">no_next</span><span class="w">
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="3798746903-4">(</span><span class="ss">arity</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="3798746903-4">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="o">*</span><span class="ss">hp</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_arityval</span><span class="p" data-group-id="3798746903-5">(</span><span class="ss">arity</span><span class="p" data-group-id="3798746903-5">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="5147032230-4">(</span><span class="ss">arity</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="5147032230-4">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="o">*</span><span class="ss">hp</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_arityval</span><span class="p" data-group-id="5147032230-5">(</span><span class="ss">arity</span><span class="p" data-group-id="5147032230-5">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │      </span><span class="o">/</span><span class="o">*</span><span class="w">
│ │ │       </span><span class="o">*</span><span class="w"> </span><span class="n">The</span><span class="w"> </span><span class="sc">$N</span><span class="n">EXT_INSTRUCTION</span><span class="w"> </span><span class="ss">macro</span><span class="w"> </span><span class="ss">points</span><span class="w"> </span><span class="ss">just</span><span class="w"> </span><span class="ss">beyond</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">fixed</span><span class="w">
│ │ │       </span><span class="o">*</span><span class="w"> </span><span class="ss">operands</span><span class="p">.</span><span class="w"> </span><span class="n">In</span><span class="w"> </span><span class="ss">this</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="ss">it</span><span class="w"> </span><span class="ss">points</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">descriptor</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │       </span><span class="o">*</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">first</span><span class="w"> </span><span class="nb">element</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">be</span><span class="w"> </span><span class="nb">put</span><span class="w"> </span><span class="ss">into</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">tuple</span><span class="p">.</span><span class="w">
│ │ │       </span><span class="o">*</span><span class="o">/</span><span class="w">
│ │ │      </span><span class="n">I</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$N</span><span class="n">EXT_INSTRUCTION</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">do</span><span class="w"> </span><span class="p" data-group-id="3798746903-6">{</span><span class="w">
│ │ │ +    </span><span class="ss">do</span><span class="w"> </span><span class="p" data-group-id="5147032230-6">{</span><span class="w">
│ │ │          </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">term</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">*</span><span class="n">I</span><span class="o">++</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="nf">switch</span><span class="w"> </span><span class="p" data-group-id="3798746903-7">(</span><span class="nf">loader_tag</span><span class="p" data-group-id="3798746903-8">(</span><span class="ss">term</span><span class="p" data-group-id="3798746903-8">)</span><span class="p" data-group-id="3798746903-7">)</span><span class="w"> </span><span class="p" data-group-id="3798746903-9">{</span><span class="w">
│ │ │ +        </span><span class="nf">switch</span><span class="w"> </span><span class="p" data-group-id="5147032230-7">(</span><span class="nf">loader_tag</span><span class="p" data-group-id="5147032230-8">(</span><span class="ss">term</span><span class="p" data-group-id="5147032230-8">)</span><span class="p" data-group-id="5147032230-7">)</span><span class="w"> </span><span class="p" data-group-id="5147032230-9">{</span><span class="w">
│ │ │          </span><span class="k">case</span><span class="w"> </span><span class="n">LOADER_X_REG</span><span class="p">:</span><span class="w">
│ │ │ -            </span><span class="o">*</span><span class="ss">hp</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">x</span><span class="p" data-group-id="3798746903-10">(</span><span class="nf">loader_x_reg_index</span><span class="p" data-group-id="3798746903-11">(</span><span class="ss">term</span><span class="p" data-group-id="3798746903-11">)</span><span class="p" data-group-id="3798746903-10">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="o">*</span><span class="ss">hp</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">x</span><span class="p" data-group-id="5147032230-10">(</span><span class="nf">loader_x_reg_index</span><span class="p" data-group-id="5147032230-11">(</span><span class="ss">term</span><span class="p" data-group-id="5147032230-11">)</span><span class="p" data-group-id="5147032230-10">)</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">break</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="k">case</span><span class="w"> </span><span class="n">LOADER_Y_REG</span><span class="p">:</span><span class="w">
│ │ │ -            </span><span class="o">*</span><span class="ss">hp</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">y</span><span class="p" data-group-id="3798746903-12">(</span><span class="nf">loader_y_reg_index</span><span class="p" data-group-id="3798746903-13">(</span><span class="ss">term</span><span class="p" data-group-id="3798746903-13">)</span><span class="p" data-group-id="3798746903-12">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="o">*</span><span class="ss">hp</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">y</span><span class="p" data-group-id="5147032230-12">(</span><span class="nf">loader_y_reg_index</span><span class="p" data-group-id="5147032230-13">(</span><span class="ss">term</span><span class="p" data-group-id="5147032230-13">)</span><span class="p" data-group-id="5147032230-12">)</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">break</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="nc">default</span><span class="p">:</span><span class="w">
│ │ │              </span><span class="o">*</span><span class="ss">hp</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">term</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">break</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3798746903-9">}</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3798746903-6">}</span><span class="w"> </span><span class="nf">while</span><span class="w"> </span><span class="p" data-group-id="3798746903-14">(</span><span class="o">--</span><span class="ss">arity</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="3798746903-14">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="o">*</span><span class="ss">dst_ptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_tuple</span><span class="p" data-group-id="3798746903-15">(</span><span class="n">HTOP</span><span class="p" data-group-id="3798746903-15">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="5147032230-9">}</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5147032230-6">}</span><span class="w"> </span><span class="nf">while</span><span class="w"> </span><span class="p" data-group-id="5147032230-14">(</span><span class="o">--</span><span class="ss">arity</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="5147032230-14">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="o">*</span><span class="ss">dst_ptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_tuple</span><span class="p" data-group-id="5147032230-15">(</span><span class="n">HTOP</span><span class="p" data-group-id="5147032230-15">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">HTOP</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">hp</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="3798746903-16">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="3798746903-17">(</span><span class="o">*</span><span class="w"> </span><span class="p" data-group-id="3798746903-18">(</span><span class="n">Eterm</span><span class="w"> </span><span class="o">*</span><span class="p" data-group-id="3798746903-18">)</span><span class="n">I</span><span class="p" data-group-id="3798746903-17">)</span><span class="p" data-group-id="3798746903-16">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">Goto</span><span class="p" data-group-id="3798746903-19">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="3798746903-19">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3798746903-2">}</span></code></pre><h4>Combined instructions</h4><p><strong>Problem</strong>: For frequently executed instructions we want to use
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="5147032230-16">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="5147032230-17">(</span><span class="o">*</span><span class="w"> </span><span class="p" data-group-id="5147032230-18">(</span><span class="n">Eterm</span><span class="w"> </span><span class="o">*</span><span class="p" data-group-id="5147032230-18">)</span><span class="n">I</span><span class="p" data-group-id="5147032230-17">)</span><span class="p" data-group-id="5147032230-16">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">Goto</span><span class="p" data-group-id="5147032230-19">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="5147032230-19">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5147032230-2">}</span></code></pre><h4>Combined instructions</h4><p><strong>Problem</strong>: For frequently executed instructions we want to use
│ │ │  &quot;fast&quot; operands types such as <code class="inline">x</code> and <code class="inline">y</code>, as opposed to <code class="inline">s</code> or <code class="inline">S</code>.
│ │ │  To avoid an explosion in code size, we want to share most of the
│ │ │  implementation between the instructions.  Here are the specific
│ │ │  instructions for <code class="inline">i_increment/5</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_increment</span><span class="w"> </span><span class="ss">r</span><span class="w"> </span><span class="n">W</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">d</span><span class="w">
│ │ │  </span><span class="ss">i_increment</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="n">W</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">d</span><span class="w">
│ │ │ -</span><span class="ss">i_increment</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="n">W</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">d</span></code></pre><p>The <code class="inline">i_increment</code> instruction is implemented like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">i_increment</span><span class="p" data-group-id="9863707830-1">(</span><span class="n">Source</span><span class="p">,</span><span class="w"> </span><span class="n">IncrementVal</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="9863707830-1">)</span><span class="w"> </span><span class="p" data-group-id="9863707830-2">{</span><span class="w">
│ │ │ +</span><span class="ss">i_increment</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="n">W</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">d</span></code></pre><p>The <code class="inline">i_increment</code> instruction is implemented like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">i_increment</span><span class="p" data-group-id="0145405325-1">(</span><span class="n">Source</span><span class="p">,</span><span class="w"> </span><span class="n">IncrementVal</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="0145405325-1">)</span><span class="w"> </span><span class="p" data-group-id="0145405325-2">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">increment_reg_source</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">ource</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">increment_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$I</span><span class="ss">ncrementVal</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Uint</span><span class="w"> </span><span class="ss">live</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">result</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="9863707830-3">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="9863707830-4">(</span><span class="nf">is_small</span><span class="p" data-group-id="9863707830-5">(</span><span class="ss">increment_reg_val</span><span class="p" data-group-id="9863707830-5">)</span><span class="p" data-group-id="9863707830-4">)</span><span class="p" data-group-id="9863707830-3">)</span><span class="w"> </span><span class="p" data-group-id="9863707830-6">{</span><span class="w">
│ │ │ -        </span><span class="n">Sint</span><span class="w"> </span><span class="ss">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">signed_val</span><span class="p" data-group-id="9863707830-7">(</span><span class="ss">increment_reg_val</span><span class="p" data-group-id="9863707830-7">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="ss">increment_val</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="9863707830-8">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="9863707830-9">(</span><span class="n">IS_SSMALL</span><span class="p" data-group-id="9863707830-10">(</span><span class="ss">i</span><span class="p" data-group-id="9863707830-10">)</span><span class="p" data-group-id="9863707830-9">)</span><span class="p" data-group-id="9863707830-8">)</span><span class="w"> </span><span class="p" data-group-id="9863707830-11">{</span><span class="w">
│ │ │ -            </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_small</span><span class="p" data-group-id="9863707830-12">(</span><span class="ss">i</span><span class="p" data-group-id="9863707830-12">)</span><span class="p">;</span><span class="w">
│ │ │ -            </span><span class="sc">$N</span><span class="n">EXT0</span><span class="p" data-group-id="9863707830-13">(</span><span class="p" data-group-id="9863707830-13">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9863707830-11">}</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9863707830-6">}</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="0145405325-3">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="0145405325-4">(</span><span class="nf">is_small</span><span class="p" data-group-id="0145405325-5">(</span><span class="ss">increment_reg_val</span><span class="p" data-group-id="0145405325-5">)</span><span class="p" data-group-id="0145405325-4">)</span><span class="p" data-group-id="0145405325-3">)</span><span class="w"> </span><span class="p" data-group-id="0145405325-6">{</span><span class="w">
│ │ │ +        </span><span class="n">Sint</span><span class="w"> </span><span class="ss">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">signed_val</span><span class="p" data-group-id="0145405325-7">(</span><span class="ss">increment_reg_val</span><span class="p" data-group-id="0145405325-7">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="ss">increment_val</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="0145405325-8">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="0145405325-9">(</span><span class="n">IS_SSMALL</span><span class="p" data-group-id="0145405325-10">(</span><span class="ss">i</span><span class="p" data-group-id="0145405325-10">)</span><span class="p" data-group-id="0145405325-9">)</span><span class="p" data-group-id="0145405325-8">)</span><span class="w"> </span><span class="p" data-group-id="0145405325-11">{</span><span class="w">
│ │ │ +            </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_small</span><span class="p" data-group-id="0145405325-12">(</span><span class="ss">i</span><span class="p" data-group-id="0145405325-12">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="sc">$N</span><span class="n">EXT0</span><span class="p" data-group-id="0145405325-13">(</span><span class="p" data-group-id="0145405325-13">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0145405325-11">}</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0145405325-6">}</span><span class="w">
│ │ │      </span><span class="ss">live</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$L</span><span class="ss">ive</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">HEAVY_SWAPOUT</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">reg</span><span class="p" data-group-id="9863707830-14">[</span><span class="ss">live</span><span class="p" data-group-id="9863707830-14">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">increment_reg_val</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">reg</span><span class="p" data-group-id="9863707830-15">[</span><span class="ss">live</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="9863707830-15">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_small</span><span class="p" data-group-id="9863707830-16">(</span><span class="ss">increment_val</span><span class="p" data-group-id="9863707830-16">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erts_gc_mixed_plus</span><span class="p" data-group-id="9863707830-17">(</span><span class="ss">c_p</span><span class="p">,</span><span class="w"> </span><span class="ss">reg</span><span class="p">,</span><span class="w"> </span><span class="ss">live</span><span class="p" data-group-id="9863707830-17">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">reg</span><span class="p" data-group-id="0145405325-14">[</span><span class="ss">live</span><span class="p" data-group-id="0145405325-14">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">increment_reg_val</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">reg</span><span class="p" data-group-id="0145405325-15">[</span><span class="ss">live</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="0145405325-15">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_small</span><span class="p" data-group-id="0145405325-16">(</span><span class="ss">increment_val</span><span class="p" data-group-id="0145405325-16">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erts_gc_mixed_plus</span><span class="p" data-group-id="0145405325-17">(</span><span class="ss">c_p</span><span class="p">,</span><span class="w"> </span><span class="ss">reg</span><span class="p">,</span><span class="w"> </span><span class="ss">live</span><span class="p" data-group-id="0145405325-17">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">HEAVY_SWAPIN</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">ERTS_HOLE_CHECK</span><span class="p" data-group-id="9863707830-18">(</span><span class="ss">c_p</span><span class="p" data-group-id="9863707830-18">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="9863707830-19">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="9863707830-20">(</span><span class="nf">is_value</span><span class="p" data-group-id="9863707830-21">(</span><span class="ss">result</span><span class="p" data-group-id="9863707830-21">)</span><span class="p" data-group-id="9863707830-20">)</span><span class="p" data-group-id="9863707830-19">)</span><span class="w"> </span><span class="p" data-group-id="9863707830-22">{</span><span class="w">
│ │ │ -        </span><span class="sc">$R</span><span class="n">EFRESH_GEN_DEST</span><span class="p" data-group-id="9863707830-23">(</span><span class="p" data-group-id="9863707830-23">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">ERTS_HOLE_CHECK</span><span class="p" data-group-id="0145405325-18">(</span><span class="ss">c_p</span><span class="p" data-group-id="0145405325-18">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="0145405325-19">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="0145405325-20">(</span><span class="nf">is_value</span><span class="p" data-group-id="0145405325-21">(</span><span class="ss">result</span><span class="p" data-group-id="0145405325-21">)</span><span class="p" data-group-id="0145405325-20">)</span><span class="p" data-group-id="0145405325-19">)</span><span class="w"> </span><span class="p" data-group-id="0145405325-22">{</span><span class="w">
│ │ │ +        </span><span class="sc">$R</span><span class="n">EFRESH_GEN_DEST</span><span class="p" data-group-id="0145405325-23">(</span><span class="p" data-group-id="0145405325-23">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">result</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="sc">$N</span><span class="n">EXT0</span><span class="p" data-group-id="9863707830-24">(</span><span class="p" data-group-id="9863707830-24">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9863707830-22">}</span><span class="w">
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="9863707830-25">(</span><span class="ss">c_p</span><span class="p">-&gt;</span><span class="ss">freason</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="n">BADMATCH</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_value</span><span class="p" data-group-id="9863707830-26">(</span><span class="ss">c_p</span><span class="p">-&gt;</span><span class="ss">fvalue</span><span class="p" data-group-id="9863707830-26">)</span><span class="p" data-group-id="9863707830-25">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="sc">$N</span><span class="n">EXT0</span><span class="p" data-group-id="0145405325-24">(</span><span class="p" data-group-id="0145405325-24">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0145405325-22">}</span><span class="w">
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="0145405325-25">(</span><span class="ss">c_p</span><span class="p">-&gt;</span><span class="ss">freason</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="n">BADMATCH</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_value</span><span class="p" data-group-id="0145405325-26">(</span><span class="ss">c_p</span><span class="p">-&gt;</span><span class="ss">fvalue</span><span class="p" data-group-id="0145405325-26">)</span><span class="p" data-group-id="0145405325-25">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">goto</span><span class="w"> </span><span class="ss">find_func_info</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9863707830-2">}</span></code></pre><p>There will be three almost identical copies of the code.  Given the
│ │ │ +</span><span class="p" data-group-id="0145405325-2">}</span></code></pre><p>There will be three almost identical copies of the code.  Given the
│ │ │  size of the code, that could be too high cost to pay.</p><p>To avoid the three copies of the code, we could use only one specific
│ │ │  instruction:</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_increment</span><span class="w"> </span><span class="n">S</span><span class="w"> </span><span class="n">W</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">d</span></code></pre><p>(The same implementation as above will work.)</p><p>That reduces the code size, but is slower because <code class="inline">S</code> means that
│ │ │  there will be extra code to test whether the operand refers to an X
│ │ │  register or a Y register.</p><p><strong>Solution</strong>: We can use &quot;combined instructions&quot;.  Combined
│ │ │  instructions are combined from instruction fragments.  The
│ │ │  bulk of the code can be shared.</p><p>Here we will show how <code class="inline">i_increment</code> can be implemented as a combined
│ │ │  instruction.  We will show each individual fragment first, and then
│ │ │  show how to connect them together.  First we will need a variable that
│ │ │ -we can store the value fetched from the register in:</p><pre><code class="makeup erlang" translate="no"><span class="ss">increment</span><span class="p">.</span><span class="nf">head</span><span class="p" data-group-id="0234807744-1">(</span><span class="p" data-group-id="0234807744-1">)</span><span class="w"> </span><span class="p" data-group-id="0234807744-2">{</span><span class="w">
│ │ │ +we can store the value fetched from the register in:</p><pre><code class="makeup erlang" translate="no"><span class="ss">increment</span><span class="p">.</span><span class="nf">head</span><span class="p" data-group-id="6441902672-1">(</span><span class="p" data-group-id="6441902672-1">)</span><span class="w"> </span><span class="p" data-group-id="6441902672-2">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">increment_reg_val</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0234807744-2">}</span></code></pre><p>The name <code class="inline">increment</code> is the name of the group that the fragment
│ │ │ +</span><span class="p" data-group-id="6441902672-2">}</span></code></pre><p>The name <code class="inline">increment</code> is the name of the group that the fragment
│ │ │  belongs to.  Note that it does not need to have the same
│ │ │  name as the instruction.  The group name is followed by <code class="inline">.</code> and
│ │ │  the name of the fragment.  The name <code class="inline">head</code> is pre-defined.
│ │ │  The code in it will be placed at the beginning of a block, so
│ │ │  that all fragments in the group can access it.</p><p>Next we define the fragment that will pick up the value from the
│ │ │ -register from the first operand:</p><pre><code class="makeup erlang" translate="no"><span class="ss">increment</span><span class="p">.</span><span class="nf">fetch</span><span class="p" data-group-id="4247136281-1">(</span><span class="n">Src</span><span class="p" data-group-id="4247136281-1">)</span><span class="w"> </span><span class="p" data-group-id="4247136281-2">{</span><span class="w">
│ │ │ +register from the first operand:</p><pre><code class="makeup erlang" translate="no"><span class="ss">increment</span><span class="p">.</span><span class="nf">fetch</span><span class="p" data-group-id="5287771389-1">(</span><span class="n">Src</span><span class="p" data-group-id="5287771389-1">)</span><span class="w"> </span><span class="p" data-group-id="5287771389-2">{</span><span class="w">
│ │ │      </span><span class="ss">increment_reg_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">rc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4247136281-2">}</span></code></pre><p>We call this fragment <code class="inline">fetch</code>.  This fragment will be duplicated three
│ │ │ -times, one for each value of the first operand (<code class="inline">r</code>, <code class="inline">x</code>, and <code class="inline">y</code>).</p><p>Next we define the main part of the code that do the actual incrementing.</p><pre><code class="makeup erlang" translate="no"><span class="ss">increment</span><span class="p">.</span><span class="nf">execute</span><span class="p" data-group-id="2345918487-1">(</span><span class="n">IncrementVal</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="2345918487-1">)</span><span class="w"> </span><span class="p" data-group-id="2345918487-2">{</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5287771389-2">}</span></code></pre><p>We call this fragment <code class="inline">fetch</code>.  This fragment will be duplicated three
│ │ │ +times, one for each value of the first operand (<code class="inline">r</code>, <code class="inline">x</code>, and <code class="inline">y</code>).</p><p>Next we define the main part of the code that do the actual incrementing.</p><pre><code class="makeup erlang" translate="no"><span class="ss">increment</span><span class="p">.</span><span class="nf">execute</span><span class="p" data-group-id="8911789179-1">(</span><span class="n">IncrementVal</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="8911789179-1">)</span><span class="w"> </span><span class="p" data-group-id="8911789179-2">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">increment_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$I</span><span class="ss">ncrementVal</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Uint</span><span class="w"> </span><span class="ss">live</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">result</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="2345918487-3">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="2345918487-4">(</span><span class="nf">is_small</span><span class="p" data-group-id="2345918487-5">(</span><span class="ss">increment_reg_val</span><span class="p" data-group-id="2345918487-5">)</span><span class="p" data-group-id="2345918487-4">)</span><span class="p" data-group-id="2345918487-3">)</span><span class="w"> </span><span class="p" data-group-id="2345918487-6">{</span><span class="w">
│ │ │ -        </span><span class="n">Sint</span><span class="w"> </span><span class="ss">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">signed_val</span><span class="p" data-group-id="2345918487-7">(</span><span class="ss">increment_reg_val</span><span class="p" data-group-id="2345918487-7">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="ss">increment_val</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="2345918487-8">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="2345918487-9">(</span><span class="n">IS_SSMALL</span><span class="p" data-group-id="2345918487-10">(</span><span class="ss">i</span><span class="p" data-group-id="2345918487-10">)</span><span class="p" data-group-id="2345918487-9">)</span><span class="p" data-group-id="2345918487-8">)</span><span class="w"> </span><span class="p" data-group-id="2345918487-11">{</span><span class="w">
│ │ │ -            </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_small</span><span class="p" data-group-id="2345918487-12">(</span><span class="ss">i</span><span class="p" data-group-id="2345918487-12">)</span><span class="p">;</span><span class="w">
│ │ │ -            </span><span class="sc">$N</span><span class="n">EXT0</span><span class="p" data-group-id="2345918487-13">(</span><span class="p" data-group-id="2345918487-13">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="2345918487-11">}</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2345918487-6">}</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="8911789179-3">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="8911789179-4">(</span><span class="nf">is_small</span><span class="p" data-group-id="8911789179-5">(</span><span class="ss">increment_reg_val</span><span class="p" data-group-id="8911789179-5">)</span><span class="p" data-group-id="8911789179-4">)</span><span class="p" data-group-id="8911789179-3">)</span><span class="w"> </span><span class="p" data-group-id="8911789179-6">{</span><span class="w">
│ │ │ +        </span><span class="n">Sint</span><span class="w"> </span><span class="ss">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">signed_val</span><span class="p" data-group-id="8911789179-7">(</span><span class="ss">increment_reg_val</span><span class="p" data-group-id="8911789179-7">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="ss">increment_val</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="8911789179-8">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="8911789179-9">(</span><span class="n">IS_SSMALL</span><span class="p" data-group-id="8911789179-10">(</span><span class="ss">i</span><span class="p" data-group-id="8911789179-10">)</span><span class="p" data-group-id="8911789179-9">)</span><span class="p" data-group-id="8911789179-8">)</span><span class="w"> </span><span class="p" data-group-id="8911789179-11">{</span><span class="w">
│ │ │ +            </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_small</span><span class="p" data-group-id="8911789179-12">(</span><span class="ss">i</span><span class="p" data-group-id="8911789179-12">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="sc">$N</span><span class="n">EXT0</span><span class="p" data-group-id="8911789179-13">(</span><span class="p" data-group-id="8911789179-13">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="8911789179-11">}</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8911789179-6">}</span><span class="w">
│ │ │      </span><span class="ss">live</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$L</span><span class="ss">ive</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">HEAVY_SWAPOUT</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">reg</span><span class="p" data-group-id="2345918487-14">[</span><span class="ss">live</span><span class="p" data-group-id="2345918487-14">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">increment_reg_val</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">reg</span><span class="p" data-group-id="2345918487-15">[</span><span class="ss">live</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="2345918487-15">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_small</span><span class="p" data-group-id="2345918487-16">(</span><span class="ss">increment_val</span><span class="p" data-group-id="2345918487-16">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erts_gc_mixed_plus</span><span class="p" data-group-id="2345918487-17">(</span><span class="ss">c_p</span><span class="p">,</span><span class="w"> </span><span class="ss">reg</span><span class="p">,</span><span class="w"> </span><span class="ss">live</span><span class="p" data-group-id="2345918487-17">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">reg</span><span class="p" data-group-id="8911789179-14">[</span><span class="ss">live</span><span class="p" data-group-id="8911789179-14">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">increment_reg_val</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">reg</span><span class="p" data-group-id="8911789179-15">[</span><span class="ss">live</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="8911789179-15">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_small</span><span class="p" data-group-id="8911789179-16">(</span><span class="ss">increment_val</span><span class="p" data-group-id="8911789179-16">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erts_gc_mixed_plus</span><span class="p" data-group-id="8911789179-17">(</span><span class="ss">c_p</span><span class="p">,</span><span class="w"> </span><span class="ss">reg</span><span class="p">,</span><span class="w"> </span><span class="ss">live</span><span class="p" data-group-id="8911789179-17">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">HEAVY_SWAPIN</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">ERTS_HOLE_CHECK</span><span class="p" data-group-id="2345918487-18">(</span><span class="ss">c_p</span><span class="p" data-group-id="2345918487-18">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="2345918487-19">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="2345918487-20">(</span><span class="nf">is_value</span><span class="p" data-group-id="2345918487-21">(</span><span class="ss">result</span><span class="p" data-group-id="2345918487-21">)</span><span class="p" data-group-id="2345918487-20">)</span><span class="p" data-group-id="2345918487-19">)</span><span class="w"> </span><span class="p" data-group-id="2345918487-22">{</span><span class="w">
│ │ │ -        </span><span class="sc">$R</span><span class="n">EFRESH_GEN_DEST</span><span class="p" data-group-id="2345918487-23">(</span><span class="p" data-group-id="2345918487-23">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">ERTS_HOLE_CHECK</span><span class="p" data-group-id="8911789179-18">(</span><span class="ss">c_p</span><span class="p" data-group-id="8911789179-18">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="8911789179-19">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="8911789179-20">(</span><span class="nf">is_value</span><span class="p" data-group-id="8911789179-21">(</span><span class="ss">result</span><span class="p" data-group-id="8911789179-21">)</span><span class="p" data-group-id="8911789179-20">)</span><span class="p" data-group-id="8911789179-19">)</span><span class="w"> </span><span class="p" data-group-id="8911789179-22">{</span><span class="w">
│ │ │ +        </span><span class="sc">$R</span><span class="n">EFRESH_GEN_DEST</span><span class="p" data-group-id="8911789179-23">(</span><span class="p" data-group-id="8911789179-23">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">result</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="sc">$N</span><span class="n">EXT0</span><span class="p" data-group-id="2345918487-24">(</span><span class="p" data-group-id="2345918487-24">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2345918487-22">}</span><span class="w">
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="2345918487-25">(</span><span class="ss">c_p</span><span class="p">-&gt;</span><span class="ss">freason</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="n">BADMATCH</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_value</span><span class="p" data-group-id="2345918487-26">(</span><span class="ss">c_p</span><span class="p">-&gt;</span><span class="ss">fvalue</span><span class="p" data-group-id="2345918487-26">)</span><span class="p" data-group-id="2345918487-25">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="sc">$N</span><span class="n">EXT0</span><span class="p" data-group-id="8911789179-24">(</span><span class="p" data-group-id="8911789179-24">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8911789179-22">}</span><span class="w">
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="8911789179-25">(</span><span class="ss">c_p</span><span class="p">-&gt;</span><span class="ss">freason</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="n">BADMATCH</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_value</span><span class="p" data-group-id="8911789179-26">(</span><span class="ss">c_p</span><span class="p">-&gt;</span><span class="ss">fvalue</span><span class="p" data-group-id="8911789179-26">)</span><span class="p" data-group-id="8911789179-25">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">goto</span><span class="w"> </span><span class="ss">find_func_info</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2345918487-2">}</span></code></pre><p>We call this fragment <code class="inline">execute</code>.  It will handle the three remaining
│ │ │ +</span><span class="p" data-group-id="8911789179-2">}</span></code></pre><p>We call this fragment <code class="inline">execute</code>.  It will handle the three remaining
│ │ │  operands (<code class="inline">W t d</code>).  There will only be one copy of this fragment.</p><p>Now that we have defined the fragments, we need to inform
│ │ │  <strong>beam_makeops</strong> how they should be connected:</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_increment</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">increment</span><span class="p">.</span><span class="ss">fetch</span><span class="p">.</span><span class="ss">execute</span><span class="p">;</span></code></pre><p>To the left of the <code class="inline">:=</code> is the name of the specific instruction that
│ │ │  should be implemented by the fragments, in this case <code class="inline">i_increment</code>.
│ │ │  To the right of <code class="inline">:=</code> is the name of the group with the fragments,
│ │ │  followed by a <code class="inline">.</code>.  Then the name of the fragments in the group are
│ │ │  listed in the order they should be executed.  Note that the <code class="inline">head</code>
│ │ │  fragment is not listed.</p><p>The line ends in <code class="inline">;</code> (to avoid messing up the indentation in Emacs).</p><p>(Note that in practice the <code class="inline">:=</code> line is usually placed before the
│ │ │ -fragments.)</p><p>The generated code looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8377594130-1">{</span><span class="w">
│ │ │ +fragments.)</p><p>The generated code looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7794547741-1">{</span><span class="w">
│ │ │    </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">increment_reg_val</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">OpCase</span><span class="p" data-group-id="8377594130-2">(</span><span class="ss">i_increment_rWtd</span><span class="p" data-group-id="8377594130-2">)</span><span class="p">:</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="8377594130-3">{</span><span class="w">
│ │ │ -    </span><span class="ss">increment_reg_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">r</span><span class="p" data-group-id="8377594130-4">(</span><span class="mi">0</span><span class="p" data-group-id="8377594130-4">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="8377594130-3">}</span><span class="w">
│ │ │ +  </span><span class="n">OpCase</span><span class="p" data-group-id="7794547741-2">(</span><span class="ss">i_increment_rWtd</span><span class="p" data-group-id="7794547741-2">)</span><span class="p">:</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="7794547741-3">{</span><span class="w">
│ │ │ +    </span><span class="ss">increment_reg_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">r</span><span class="p" data-group-id="7794547741-4">(</span><span class="mi">0</span><span class="p" data-group-id="7794547741-4">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="7794547741-3">}</span><span class="w">
│ │ │    </span><span class="ss">goto</span><span class="w"> </span><span class="ss">increment__execute</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -  </span><span class="n">OpCase</span><span class="p" data-group-id="8377594130-5">(</span><span class="ss">i_increment_xWtd</span><span class="p" data-group-id="8377594130-5">)</span><span class="p">:</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="8377594130-6">{</span><span class="w">
│ │ │ -    </span><span class="ss">increment_reg_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">xb</span><span class="p" data-group-id="8377594130-7">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="8377594130-8">(</span><span class="n">I</span><span class="p" data-group-id="8377594130-9">[</span><span class="mi">0</span><span class="p" data-group-id="8377594130-9">]</span><span class="p" data-group-id="8377594130-8">)</span><span class="p" data-group-id="8377594130-7">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="8377594130-6">}</span><span class="w">
│ │ │ +  </span><span class="n">OpCase</span><span class="p" data-group-id="7794547741-5">(</span><span class="ss">i_increment_xWtd</span><span class="p" data-group-id="7794547741-5">)</span><span class="p">:</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="7794547741-6">{</span><span class="w">
│ │ │ +    </span><span class="ss">increment_reg_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">xb</span><span class="p" data-group-id="7794547741-7">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="7794547741-8">(</span><span class="n">I</span><span class="p" data-group-id="7794547741-9">[</span><span class="mi">0</span><span class="p" data-group-id="7794547741-9">]</span><span class="p" data-group-id="7794547741-8">)</span><span class="p" data-group-id="7794547741-7">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="7794547741-6">}</span><span class="w">
│ │ │    </span><span class="ss">goto</span><span class="w"> </span><span class="ss">increment__execute</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -  </span><span class="n">OpCase</span><span class="p" data-group-id="8377594130-10">(</span><span class="ss">i_increment_yWtd</span><span class="p" data-group-id="8377594130-10">)</span><span class="p">:</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="8377594130-11">{</span><span class="w">
│ │ │ -    </span><span class="ss">increment_reg_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">yb</span><span class="p" data-group-id="8377594130-12">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="8377594130-13">(</span><span class="n">I</span><span class="p" data-group-id="8377594130-14">[</span><span class="mi">0</span><span class="p" data-group-id="8377594130-14">]</span><span class="p" data-group-id="8377594130-13">)</span><span class="p" data-group-id="8377594130-12">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="8377594130-11">}</span><span class="w">
│ │ │ +  </span><span class="n">OpCase</span><span class="p" data-group-id="7794547741-10">(</span><span class="ss">i_increment_yWtd</span><span class="p" data-group-id="7794547741-10">)</span><span class="p">:</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="7794547741-11">{</span><span class="w">
│ │ │ +    </span><span class="ss">increment_reg_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">yb</span><span class="p" data-group-id="7794547741-12">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="7794547741-13">(</span><span class="n">I</span><span class="p" data-group-id="7794547741-14">[</span><span class="mi">0</span><span class="p" data-group-id="7794547741-14">]</span><span class="p" data-group-id="7794547741-13">)</span><span class="p" data-group-id="7794547741-12">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="7794547741-11">}</span><span class="w">
│ │ │    </span><span class="ss">goto</span><span class="w"> </span><span class="ss">increment__execute</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │    </span><span class="nc">increment__execute</span><span class="p">:</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="8377594130-15">{</span><span class="w">
│ │ │ -    </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">Here</span><span class="w"> </span><span class="ss">follows</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">increment</span><span class="p">.</span><span class="nf">execute</span><span class="p" data-group-id="8377594130-16">(</span><span class="p" data-group-id="8377594130-16">)</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="7794547741-15">{</span><span class="w">
│ │ │ +    </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">Here</span><span class="w"> </span><span class="ss">follows</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">increment</span><span class="p">.</span><span class="nf">execute</span><span class="p" data-group-id="7794547741-16">(</span><span class="p" data-group-id="7794547741-16">)</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8377594130-15">}</span></code></pre><h5>Some notes about combined instructions</h5><p>The operands that are different must be at
│ │ │ +</span><span class="p" data-group-id="7794547741-15">}</span></code></pre><h5>Some notes about combined instructions</h5><p>The operands that are different must be at
│ │ │  the beginning of the instruction.  All operands in the last
│ │ │  fragment must have the same operands in all variants of
│ │ │  the specific instruction.</p><p>As an example, the following specific instructions cannot be
│ │ │  implemented as a combined instruction:</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_times</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">d</span><span class="w">
│ │ │  </span><span class="ss">i_times</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="ss">d</span><span class="w">
│ │ │  </span><span class="ss">i_times</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="ss">d</span></code></pre><p>We would have to change the order of the operands so that the
│ │ │  two operands that are different are placed first:</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_times</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">d</span><span class="w">
│ │ │  </span><span class="ss">i_times</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">d</span><span class="w">
│ │ │  </span><span class="ss">i_times</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">d</span></code></pre><p>We can then define:</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_times</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">times</span><span class="p">.</span><span class="ss">fetch</span><span class="p">.</span><span class="ss">execute</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">times</span><span class="p">.</span><span class="ss">head</span><span class="w"> </span><span class="p" data-group-id="0602635205-1">{</span><span class="w">
│ │ │ +</span><span class="ss">times</span><span class="p">.</span><span class="ss">head</span><span class="w"> </span><span class="p" data-group-id="7130262679-1">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">op1</span><span class="p">,</span><span class="w"> </span><span class="ss">op2</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0602635205-1">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7130262679-1">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">times</span><span class="p">.</span><span class="nf">fetch</span><span class="p" data-group-id="0602635205-2">(</span><span class="n">Src1</span><span class="p">,</span><span class="w"> </span><span class="n">Src2</span><span class="p" data-group-id="0602635205-2">)</span><span class="w"> </span><span class="p" data-group-id="0602635205-3">{</span><span class="w">
│ │ │ +</span><span class="ss">times</span><span class="p">.</span><span class="nf">fetch</span><span class="p" data-group-id="7130262679-2">(</span><span class="n">Src1</span><span class="p">,</span><span class="w"> </span><span class="n">Src2</span><span class="p" data-group-id="7130262679-2">)</span><span class="w"> </span><span class="p" data-group-id="7130262679-3">{</span><span class="w">
│ │ │      </span><span class="ss">op1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">rc1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">op2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">rc2</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0602635205-3">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7130262679-3">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">times</span><span class="p">.</span><span class="nf">execute</span><span class="p" data-group-id="0602635205-4">(</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="0602635205-4">)</span><span class="w"> </span><span class="p" data-group-id="0602635205-5">{</span><span class="w">
│ │ │ +</span><span class="ss">times</span><span class="p">.</span><span class="nf">execute</span><span class="p" data-group-id="7130262679-4">(</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="7130262679-4">)</span><span class="w"> </span><span class="p" data-group-id="7130262679-5">{</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">Multiply</span><span class="w"> </span><span class="ss">op1</span><span class="w"> </span><span class="ow">and</span><span class="w"> </span><span class="ss">op2</span><span class="p">.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0602635205-5">}</span></code></pre><p>Several instructions can share a group.  As an example, the following
│ │ │ +</span><span class="p" data-group-id="7130262679-5">}</span></code></pre><p>Several instructions can share a group.  As an example, the following
│ │ │  instructions have different names, but in the end they all create a
│ │ │  binary.  The last two operands are common for all of them:</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_bs_init_fail</span><span class="w">       </span><span class="ss">xy</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">t</span><span class="o">?</span><span class="w"> </span><span class="ss">x</span><span class="w">
│ │ │  </span><span class="ss">i_bs_init_fail_heap</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="n">I</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">t</span><span class="o">?</span><span class="w"> </span><span class="ss">x</span><span class="w">
│ │ │  </span><span class="ss">i_bs_init</span><span class="w">                </span><span class="n">W</span><span class="w"> </span><span class="ss">t</span><span class="o">?</span><span class="w"> </span><span class="ss">x</span><span class="w">
│ │ │  </span><span class="ss">i_bs_init_heap</span><span class="w">         </span><span class="n">W</span><span class="w"> </span><span class="n">I</span><span class="w"> </span><span class="ss">t</span><span class="o">?</span><span class="w"> </span><span class="ss">x</span></code></pre><p>The instructions are defined like this (formatted with extra
│ │ │  spaces for clarity):</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_bs_init_fail_heap</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">bs_init</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="ss">fail_heap</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="ss">verify</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="ss">execute</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="ss">i_bs_init_fail</span><span class="w">      </span><span class="p">:=</span><span class="w"> </span><span class="ss">bs_init</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="ss">fail</span><span class="w">      </span><span class="p">.</span><span class="w"> </span><span class="ss">verify</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="ss">execute</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="ss">i_bs_init</span><span class="w">           </span><span class="p">:=</span><span class="w"> </span><span class="ss">bs_init</span><span class="w"> </span><span class="p">.</span><span class="w">           </span><span class="p">.</span><span class="w">  </span><span class="ss">plain</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="ss">execute</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="ss">i_bs_init_heap</span><span class="w">      </span><span class="p">:=</span><span class="w"> </span><span class="ss">bs_init</span><span class="w"> </span><span class="p">.</span><span class="w">               </span><span class="ss">heap</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="ss">execute</span><span class="p">;</span></code></pre><p>Note that the first two instruction have three fragments, while the
│ │ │ -other two only have two fragments.  Here are the fragments:</p><pre><code class="makeup erlang" translate="no"><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">head</span><span class="p" data-group-id="5033089493-1">(</span><span class="p" data-group-id="5033089493-1">)</span><span class="w"> </span><span class="p" data-group-id="5033089493-2">{</span><span class="w">
│ │ │ +other two only have two fragments.  Here are the fragments:</p><pre><code class="makeup erlang" translate="no"><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">head</span><span class="p" data-group-id="0021058346-1">(</span><span class="p" data-group-id="0021058346-1">)</span><span class="w"> </span><span class="p" data-group-id="0021058346-2">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">num_bits_term</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Uint</span><span class="w"> </span><span class="ss">num_bits</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Uint</span><span class="w"> </span><span class="ss">alloc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5033089493-2">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0021058346-2">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">plain</span><span class="p" data-group-id="5033089493-3">(</span><span class="n">NumBits</span><span class="p" data-group-id="5033089493-3">)</span><span class="w"> </span><span class="p" data-group-id="5033089493-4">{</span><span class="w">
│ │ │ +</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">plain</span><span class="p" data-group-id="0021058346-3">(</span><span class="n">NumBits</span><span class="p" data-group-id="0021058346-3">)</span><span class="w"> </span><span class="p" data-group-id="0021058346-4">{</span><span class="w">
│ │ │      </span><span class="ss">num_bits</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$N</span><span class="ss">umBits</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">alloc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5033089493-4">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0021058346-4">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">heap</span><span class="p" data-group-id="5033089493-5">(</span><span class="n">NumBits</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="5033089493-5">)</span><span class="w"> </span><span class="p" data-group-id="5033089493-6">{</span><span class="w">
│ │ │ +</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">heap</span><span class="p" data-group-id="0021058346-5">(</span><span class="n">NumBits</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="0021058346-5">)</span><span class="w"> </span><span class="p" data-group-id="0021058346-6">{</span><span class="w">
│ │ │      </span><span class="ss">num_bits</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$N</span><span class="ss">umBits</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">alloc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$A</span><span class="ss">lloc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5033089493-6">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0021058346-6">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">fail</span><span class="p" data-group-id="5033089493-7">(</span><span class="n">NumBitsTerm</span><span class="p" data-group-id="5033089493-7">)</span><span class="w"> </span><span class="p" data-group-id="5033089493-8">{</span><span class="w">
│ │ │ +</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">fail</span><span class="p" data-group-id="0021058346-7">(</span><span class="n">NumBitsTerm</span><span class="p" data-group-id="0021058346-7">)</span><span class="w"> </span><span class="p" data-group-id="0021058346-8">{</span><span class="w">
│ │ │      </span><span class="ss">num_bits_term</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$N</span><span class="ss">umBitsTerm</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">alloc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5033089493-8">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0021058346-8">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">fail_heap</span><span class="p" data-group-id="5033089493-9">(</span><span class="n">NumBitsTerm</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="5033089493-9">)</span><span class="w"> </span><span class="p" data-group-id="5033089493-10">{</span><span class="w">
│ │ │ +</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">fail_heap</span><span class="p" data-group-id="0021058346-9">(</span><span class="n">NumBitsTerm</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="0021058346-9">)</span><span class="w"> </span><span class="p" data-group-id="0021058346-10">{</span><span class="w">
│ │ │      </span><span class="ss">num_bits_term</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$N</span><span class="ss">umBitsTerm</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">alloc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$A</span><span class="ss">lloc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5033089493-10">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0021058346-10">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">verify</span><span class="p" data-group-id="5033089493-11">(</span><span class="n">Fail</span><span class="p" data-group-id="5033089493-11">)</span><span class="w"> </span><span class="p" data-group-id="5033089493-12">{</span><span class="w">
│ │ │ +</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">verify</span><span class="p" data-group-id="0021058346-11">(</span><span class="n">Fail</span><span class="p" data-group-id="0021058346-11">)</span><span class="w"> </span><span class="p" data-group-id="0021058346-12">{</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">Verify</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">num_bits_term</span><span class="p">,</span><span class="w"> </span><span class="ss">fail</span><span class="w"> </span><span class="ss">using</span><span class="w"> </span><span class="sc">$F</span><span class="n">AIL</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="ss">there</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="ss">problem</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5033089493-12">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0021058346-12">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">execute</span><span class="p" data-group-id="5033089493-13">(</span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="5033089493-13">)</span><span class="w"> </span><span class="p" data-group-id="5033089493-14">{</span><span class="w">
│ │ │ +</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">execute</span><span class="p" data-group-id="0021058346-13">(</span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="0021058346-13">)</span><span class="w"> </span><span class="p" data-group-id="0021058346-14">{</span><span class="w">
│ │ │     </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="ss">complicated</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="ss">create</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="ss">binary</span><span class="p">.</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5033089493-14">}</span></code></pre><p>The full definitions of those instructions can be found in <code class="inline">bs_instrs.tab</code>.
│ │ │ +</span><span class="p" data-group-id="0021058346-14">}</span></code></pre><p>The full definitions of those instructions can be found in <code class="inline">bs_instrs.tab</code>.
│ │ │  The generated code can be found in <code class="inline">beam_warm.h</code>.</p><h3 id="code-generation-for-beamasm" class="section-heading">
│ │ │    <a href="#code-generation-for-beamasm" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Code generation for BeamAsm</span>
│ │ │  </h3>
│ │ │  <p>For the BeamAsm runtime system, the implementation of each instruction is defined
│ │ │ @@ -1251,47 +1251,47 @@
│ │ │  There is one emitter function for each family of specific instructions.</p><p>All source files containing the emitter functions for generating
│ │ │  x86_64 native instructions are found in the <code class="inline">beam/jit/x86</code> directory,
│ │ │  while the corresponding files for AArch64 (Arm64) are found in
│ │ │  <code class="inline">beam/jit/arm</code>. Common source code and header files for both back-ends
│ │ │  are located in the <code class="inline">beam/jit</code> directory.</p><p>Take for example the <code class="inline">move</code> instruction. In <code class="inline">beam/jit/x86/ops.tab</code>
│ │ │  there used to be a single specific instruction for <code class="inline">move</code> defined like
│ │ │  this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">move</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="ss">d</span></code></pre><p>The implementation found in <code class="inline">beam/jit/x86/instr_common.cpp</code> used to
│ │ │ -look like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">void</span><span class="w"> </span><span class="n">BeamModuleAssembler</span><span class="p">:</span><span class="p">:</span><span class="nf">emit_move</span><span class="p" data-group-id="0522362454-1">(</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Dst</span><span class="p" data-group-id="0522362454-1">)</span><span class="w"> </span><span class="p" data-group-id="0522362454-2">{</span><span class="w">
│ │ │ -    </span><span class="nf">mov_arg</span><span class="p" data-group-id="0522362454-3">(</span><span class="n">Dst</span><span class="p">,</span><span class="w"> </span><span class="n">Src</span><span class="p" data-group-id="0522362454-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0522362454-2">}</span></code></pre><p>(The current implementation is slightly more complicated because of additional
│ │ │ +look like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">void</span><span class="w"> </span><span class="n">BeamModuleAssembler</span><span class="p">:</span><span class="p">:</span><span class="nf">emit_move</span><span class="p" data-group-id="7100046794-1">(</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Dst</span><span class="p" data-group-id="7100046794-1">)</span><span class="w"> </span><span class="p" data-group-id="7100046794-2">{</span><span class="w">
│ │ │ +    </span><span class="nf">mov_arg</span><span class="p" data-group-id="7100046794-3">(</span><span class="n">Dst</span><span class="p">,</span><span class="w"> </span><span class="n">Src</span><span class="p" data-group-id="7100046794-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7100046794-2">}</span></code></pre><p>(The current implementation is slightly more complicated because of additional
│ │ │  optimizations.)</p><p>The <code class="inline">mov_arg()</code> helper function will handle all combinations of source and destination
│ │ │ -operands.  For example, the instruction <code class="inline">{move,{x,1},{y,1}}</code> will be translated like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">mov</span><span class="w"> </span><span class="ss">rdi</span><span class="p">,</span><span class="w"> </span><span class="ss">qword</span><span class="w"> </span><span class="p" data-group-id="2023095369-1">[</span><span class="ss">rbx</span><span class="o">+</span><span class="mi">8</span><span class="p" data-group-id="2023095369-1">]</span><span class="w">
│ │ │ -</span><span class="ss">mov</span><span class="w"> </span><span class="ss">qword</span><span class="w"> </span><span class="p" data-group-id="2023095369-2">[</span><span class="ss">rsp</span><span class="o">+</span><span class="mi">8</span><span class="p" data-group-id="2023095369-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">rdi</span></code></pre><p>while <code class="inline">{move,{integer,42},{x,0}}</code> will be translated like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">mov</span><span class="w"> </span><span class="ss">qword</span><span class="w"> </span><span class="p" data-group-id="9707701206-1">[</span><span class="ss">rbx</span><span class="p" data-group-id="9707701206-1">]</span><span class="p">,</span><span class="w"> </span><span class="mi">687</span></code></pre><p>It is possible to define more than one specific instruction. For example:</p><pre><code class="makeup erlang" translate="no"><span class="ss">fload</span><span class="w"> </span><span class="n">S</span><span class="w"> </span><span class="ss">l</span><span class="w">
│ │ │ +operands.  For example, the instruction <code class="inline">{move,{x,1},{y,1}}</code> will be translated like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">mov</span><span class="w"> </span><span class="ss">rdi</span><span class="p">,</span><span class="w"> </span><span class="ss">qword</span><span class="w"> </span><span class="p" data-group-id="5771863815-1">[</span><span class="ss">rbx</span><span class="o">+</span><span class="mi">8</span><span class="p" data-group-id="5771863815-1">]</span><span class="w">
│ │ │ +</span><span class="ss">mov</span><span class="w"> </span><span class="ss">qword</span><span class="w"> </span><span class="p" data-group-id="5771863815-2">[</span><span class="ss">rsp</span><span class="o">+</span><span class="mi">8</span><span class="p" data-group-id="5771863815-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">rdi</span></code></pre><p>while <code class="inline">{move,{integer,42},{x,0}}</code> will be translated like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">mov</span><span class="w"> </span><span class="ss">qword</span><span class="w"> </span><span class="p" data-group-id="5117856248-1">[</span><span class="ss">rbx</span><span class="p" data-group-id="5117856248-1">]</span><span class="p">,</span><span class="w"> </span><span class="mi">687</span></code></pre><p>It is possible to define more than one specific instruction. For example:</p><pre><code class="makeup erlang" translate="no"><span class="ss">fload</span><span class="w"> </span><span class="n">S</span><span class="w"> </span><span class="ss">l</span><span class="w">
│ │ │  </span><span class="ss">fload</span><span class="w"> </span><span class="ss">q</span><span class="w"> </span><span class="ss">l</span></code></pre><p>By defining <code class="inline">fload</code> like this, the source operand must be a X register, Y register, or
│ │ │  a literal.  If not, the loading will be aborted.  If the instruction instead had been
│ │ │  defined like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">fload</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="ss">l</span></code></pre><p>attempting to load an invalid instruction such as <code class="inline">{fload,{atom,clearly_bad},{fr,0}}</code>
│ │ │  would cause a crash (either at load time or when the instruction was executed).</p><p>Regardless on how many specific instructions there are in the family,
│ │ │ -only a single <code class="inline">emit_fload()</code> function is allowed:</p><pre><code class="makeup erlang" translate="no"><span class="ss">void</span><span class="w"> </span><span class="n">BeamModuleAssembler</span><span class="p">:</span><span class="p">:</span><span class="nf">emit_fload</span><span class="p" data-group-id="4438693670-1">(</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Dst</span><span class="p" data-group-id="4438693670-1">)</span><span class="w"> </span><span class="p" data-group-id="4438693670-2">{</span><span class="w">
│ │ │ +only a single <code class="inline">emit_fload()</code> function is allowed:</p><pre><code class="makeup erlang" translate="no"><span class="ss">void</span><span class="w"> </span><span class="n">BeamModuleAssembler</span><span class="p">:</span><span class="p">:</span><span class="nf">emit_fload</span><span class="p" data-group-id="9221445652-1">(</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Dst</span><span class="p" data-group-id="9221445652-1">)</span><span class="w"> </span><span class="p" data-group-id="9221445652-2">{</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4438693670-2">}</span></code></pre><p><a href="" id="handling-a-variable-number-of-operands"></a></p><h4>Handling a variable number of operands</h4><p>Here follows an example of how an instruction with a variable number
│ │ │ +</span><span class="p" data-group-id="9221445652-2">}</span></code></pre><p><a href="" id="handling-a-variable-number-of-operands"></a></p><h4>Handling a variable number of operands</h4><p>Here follows an example of how an instruction with a variable number
│ │ │  of operands could be handled.  One such instructions is
│ │ │ -<code class="inline">select_val/3</code>. Here is an example how it can look like in BEAM code:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4692432653-1">{</span><span class="ss">select_val</span><span class="p">,</span><span class="p" data-group-id="4692432653-2">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="4692432653-2">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="4692432653-3">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4692432653-3">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="4692432653-4">{</span><span class="ss">list</span><span class="p">,</span><span class="p" data-group-id="4692432653-5">[</span><span class="p" data-group-id="4692432653-6">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="4692432653-6">}</span><span class="p">,</span><span class="p" data-group-id="4692432653-7">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4692432653-7">}</span><span class="p">,</span><span class="p" data-group-id="4692432653-8">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="4692432653-8">}</span><span class="p">,</span><span class="p" data-group-id="4692432653-9">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="4692432653-9">}</span><span class="p" data-group-id="4692432653-5">]</span><span class="p" data-group-id="4692432653-4">}</span><span class="p" data-group-id="4692432653-1">}</span><span class="p">.</span></code></pre><p>The loader will convert a <code class="inline">{list,[...]}</code> operand to an <code class="inline">u</code> operand whose
│ │ │ +<code class="inline">select_val/3</code>. Here is an example how it can look like in BEAM code:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0940224539-1">{</span><span class="ss">select_val</span><span class="p">,</span><span class="p" data-group-id="0940224539-2">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="0940224539-2">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="0940224539-3">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0940224539-3">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="0940224539-4">{</span><span class="ss">list</span><span class="p">,</span><span class="p" data-group-id="0940224539-5">[</span><span class="p" data-group-id="0940224539-6">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="0940224539-6">}</span><span class="p">,</span><span class="p" data-group-id="0940224539-7">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0940224539-7">}</span><span class="p">,</span><span class="p" data-group-id="0940224539-8">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="0940224539-8">}</span><span class="p">,</span><span class="p" data-group-id="0940224539-9">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0940224539-9">}</span><span class="p" data-group-id="0940224539-5">]</span><span class="p" data-group-id="0940224539-4">}</span><span class="p" data-group-id="0940224539-1">}</span><span class="p">.</span></code></pre><p>The loader will convert a <code class="inline">{list,[...]}</code> operand to an <code class="inline">u</code> operand whose
│ │ │  value is the number of elements in the list, followed by each element in
│ │ │  the list.  The instruction above would be translated to the following
│ │ │ -instruction:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7100403137-1">{</span><span class="ss">select_val</span><span class="p">,</span><span class="p" data-group-id="7100403137-2">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="7100403137-2">}</span><span class="p">,</span><span class="p" data-group-id="7100403137-3">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="7100403137-3">}</span><span class="p">,</span><span class="p" data-group-id="7100403137-4">{</span><span class="ss">u</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="7100403137-4">}</span><span class="p">,</span><span class="p" data-group-id="7100403137-5">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7100403137-5">}</span><span class="p">,</span><span class="p" data-group-id="7100403137-6">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="7100403137-6">}</span><span class="p">,</span><span class="p" data-group-id="7100403137-7">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="7100403137-7">}</span><span class="p">,</span><span class="p" data-group-id="7100403137-8">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7100403137-8">}</span><span class="p" data-group-id="7100403137-1">}</span></code></pre><p>A definition of a specific instruction for that instruction would look
│ │ │ +instruction:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0225616852-1">{</span><span class="ss">select_val</span><span class="p">,</span><span class="p" data-group-id="0225616852-2">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="0225616852-2">}</span><span class="p">,</span><span class="p" data-group-id="0225616852-3">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0225616852-3">}</span><span class="p">,</span><span class="p" data-group-id="0225616852-4">{</span><span class="ss">u</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0225616852-4">}</span><span class="p">,</span><span class="p" data-group-id="0225616852-5">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="0225616852-5">}</span><span class="p">,</span><span class="p" data-group-id="0225616852-6">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0225616852-6">}</span><span class="p">,</span><span class="p" data-group-id="0225616852-7">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="0225616852-7">}</span><span class="p">,</span><span class="p" data-group-id="0225616852-8">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0225616852-8">}</span><span class="p" data-group-id="0225616852-1">}</span></code></pre><p>A definition of a specific instruction for that instruction would look
│ │ │  like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">select_val</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="ss">f</span><span class="w"> </span><span class="n">I</span><span class="w"> </span><span class="o">*</span></code></pre><p>The <code class="inline">*</code> as the last operand will make sure that the variable operands
│ │ │  are passed in as a <code class="inline">Span</code> of <code class="inline">ArgVal</code> (will be <code class="inline">std::span</code> in C++20 onwards).
│ │ │ -Here is the emitter function:</p><pre><code class="makeup erlang" translate="no"><span class="ss">void</span><span class="w"> </span><span class="n">BeamModuleAssembler</span><span class="p">:</span><span class="p">:</span><span class="nf">emit_select_val</span><span class="p" data-group-id="8984858302-1">(</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Src</span><span class="p">,</span><span class="w">
│ │ │ +Here is the emitter function:</p><pre><code class="makeup erlang" translate="no"><span class="ss">void</span><span class="w"> </span><span class="n">BeamModuleAssembler</span><span class="p">:</span><span class="p">:</span><span class="nf">emit_select_val</span><span class="p" data-group-id="9567598507-1">(</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Src</span><span class="p">,</span><span class="w">
│ │ │                                            </span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Fail</span><span class="p">,</span><span class="w">
│ │ │                                            </span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Size</span><span class="p">,</span><span class="w">
│ │ │ -                                          </span><span class="ss">const</span><span class="w"> </span><span class="n">Span</span><span class="o">&lt;</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="o">&gt;</span><span class="w"> </span><span class="err">&amp;</span><span class="ss">args</span><span class="p" data-group-id="8984858302-1">)</span><span class="w"> </span><span class="p" data-group-id="8984858302-2">{</span><span class="w">
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="8984858302-3">(</span><span class="n">Size</span><span class="p">.</span><span class="nf">getValue</span><span class="p" data-group-id="8984858302-4">(</span><span class="p" data-group-id="8984858302-4">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="ss">args</span><span class="p">.</span><span class="nf">size</span><span class="p" data-group-id="8984858302-5">(</span><span class="p" data-group-id="8984858302-5">)</span><span class="p" data-group-id="8984858302-3">)</span><span class="p">;</span><span class="w">
│ │ │ +                                          </span><span class="ss">const</span><span class="w"> </span><span class="n">Span</span><span class="o">&lt;</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="o">&gt;</span><span class="w"> </span><span class="err">&amp;</span><span class="ss">args</span><span class="p" data-group-id="9567598507-1">)</span><span class="w"> </span><span class="p" data-group-id="9567598507-2">{</span><span class="w">
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="9567598507-3">(</span><span class="n">Size</span><span class="p">.</span><span class="nf">getValue</span><span class="p" data-group-id="9567598507-4">(</span><span class="p" data-group-id="9567598507-4">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="ss">args</span><span class="p">.</span><span class="nf">size</span><span class="p" data-group-id="9567598507-5">(</span><span class="p" data-group-id="9567598507-5">)</span><span class="p" data-group-id="9567598507-3">)</span><span class="p">;</span><span class="w">
│ │ │         </span><span class="p">.</span><span class="w">
│ │ │         </span><span class="p">.</span><span class="w">
│ │ │         </span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8984858302-2">}</span></code></pre>
│ │ │ +</span><span class="p" data-group-id="9567598507-2">}</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="tracing.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-17.0/doc/html/beamasm.html
│ │ │ @@ -145,26 +145,26 @@
│ │ │  </h2>
│ │ │  <p>The code is loaded very similarly to how it is loaded for the interpreter. Each beam
│ │ │  file is parsed and then optimized through the transformations described in
│ │ │  <a href="beam_makeops.html#defining-transformation-rules">beam_makeops</a>. The transformations
│ │ │  used in BeamAsm are much simpler than the interpreter's, as most of the
│ │ │  transformations for the interpreter are done only to eliminate the instruction
│ │ │  dispatch overhead.</p><p>Then each instruction is encoded using the C++ functions in the
│ │ │ -<code class="inline">jit/$ARCH/instr_*.cpp</code> files. For example:</p><pre><code class="makeup erlang" translate="no"><span class="ss">void</span><span class="w"> </span><span class="n">BeamModuleAssembler</span><span class="p">:</span><span class="p">:</span><span class="nf">emit_is_nonempty_list</span><span class="p" data-group-id="9817526805-1">(</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Src</span><span class="p" data-group-id="9817526805-1">)</span><span class="w"> </span><span class="p" data-group-id="9817526805-2">{</span><span class="w">
│ │ │ -  </span><span class="ss">a</span><span class="p">.</span><span class="nf">test</span><span class="p" data-group-id="9817526805-3">(</span><span class="nf">getArgRef</span><span class="p" data-group-id="9817526805-4">(</span><span class="n">Src</span><span class="p" data-group-id="9817526805-4">)</span><span class="p">,</span><span class="w"> </span><span class="nf">imm</span><span class="p" data-group-id="9817526805-5">(</span><span class="p">_</span><span class="n">TAG_PRIMARY_MASK</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">TAG_PRIMARY_LIST</span><span class="p" data-group-id="9817526805-5">)</span><span class="p" data-group-id="9817526805-3">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="ss">a</span><span class="p">.</span><span class="nf">jne</span><span class="p" data-group-id="9817526805-6">(</span><span class="ss">labels</span><span class="p" data-group-id="9817526805-7">[</span><span class="n">Fail</span><span class="p">.</span><span class="nf">getLabel</span><span class="p" data-group-id="9817526805-8">(</span><span class="p" data-group-id="9817526805-8">)</span><span class="p" data-group-id="9817526805-7">]</span><span class="p" data-group-id="9817526805-6">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9817526805-2">}</span></code></pre><p><a href="https://github.com/asmjit/asmjit">asmjit</a> provides a fairly straightforward
│ │ │ +<code class="inline">jit/$ARCH/instr_*.cpp</code> files. For example:</p><pre><code class="makeup erlang" translate="no"><span class="ss">void</span><span class="w"> </span><span class="n">BeamModuleAssembler</span><span class="p">:</span><span class="p">:</span><span class="nf">emit_is_nonempty_list</span><span class="p" data-group-id="8352652997-1">(</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Src</span><span class="p" data-group-id="8352652997-1">)</span><span class="w"> </span><span class="p" data-group-id="8352652997-2">{</span><span class="w">
│ │ │ +  </span><span class="ss">a</span><span class="p">.</span><span class="nf">test</span><span class="p" data-group-id="8352652997-3">(</span><span class="nf">getArgRef</span><span class="p" data-group-id="8352652997-4">(</span><span class="n">Src</span><span class="p" data-group-id="8352652997-4">)</span><span class="p">,</span><span class="w"> </span><span class="nf">imm</span><span class="p" data-group-id="8352652997-5">(</span><span class="p">_</span><span class="n">TAG_PRIMARY_MASK</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">TAG_PRIMARY_LIST</span><span class="p" data-group-id="8352652997-5">)</span><span class="p" data-group-id="8352652997-3">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="ss">a</span><span class="p">.</span><span class="nf">jne</span><span class="p" data-group-id="8352652997-6">(</span><span class="ss">labels</span><span class="p" data-group-id="8352652997-7">[</span><span class="n">Fail</span><span class="p">.</span><span class="nf">getLabel</span><span class="p" data-group-id="8352652997-8">(</span><span class="p" data-group-id="8352652997-8">)</span><span class="p" data-group-id="8352652997-7">]</span><span class="p" data-group-id="8352652997-6">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8352652997-2">}</span></code></pre><p><a href="https://github.com/asmjit/asmjit">asmjit</a> provides a fairly straightforward
│ │ │  mapping from a C++ function call to the x86 assembly instruction. The above
│ │ │  instruction tests if the value in the <code class="inline">Src</code> register is a non-empty list and if
│ │ │  it is not then it jumps to the fail label.</p><p>For comparison, the interpreter has 8 combinations and specializations of
│ │ │  this implementation to minimize the instruction dispatch overhead for
│ │ │  common patterns.</p><p>The original register allocation done by the Erlang compiler is used to manage the
│ │ │  liveness of values and the physical registers are statically allocated to keep
│ │ │  the necessary process state. At the moment this is the static register
│ │ │ -allocation on x86-64:</p><pre><code class="makeup erlang" translate="no"><span class="nc">rbx</span><span class="p">:</span><span class="w"> </span><span class="n">ErtsSchedulerRegisters</span><span class="w"> </span><span class="nf">struct</span><span class="w"> </span><span class="p" data-group-id="8851572734-1">(</span><span class="ss">contains</span><span class="w"> </span><span class="ss">x</span><span class="o">/</span><span class="nb">float</span><span class="w"> </span><span class="ss">registers</span><span class="w"> </span><span class="ow">and</span><span class="w"> </span><span class="ss">some</span><span class="w"> </span><span class="ss">metadata</span><span class="p" data-group-id="8851572734-1">)</span><span class="w">
│ │ │ +allocation on x86-64:</p><pre><code class="makeup erlang" translate="no"><span class="nc">rbx</span><span class="p">:</span><span class="w"> </span><span class="n">ErtsSchedulerRegisters</span><span class="w"> </span><span class="nf">struct</span><span class="w"> </span><span class="p" data-group-id="6706953412-1">(</span><span class="ss">contains</span><span class="w"> </span><span class="ss">x</span><span class="o">/</span><span class="nb">float</span><span class="w"> </span><span class="ss">registers</span><span class="w"> </span><span class="ow">and</span><span class="w"> </span><span class="ss">some</span><span class="w"> </span><span class="ss">metadata</span><span class="p" data-group-id="6706953412-1">)</span><span class="w">
│ │ │  </span><span class="nc">rbp</span><span class="p">:</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="ss">frame</span><span class="w"> </span><span class="ss">pointer</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="err">`</span><span class="ss">perf</span><span class="err">`</span><span class="w"> </span><span class="ss">support</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">enabled</span><span class="p">,</span><span class="w"> </span><span class="ss">otherwise</span><span class="w"> </span><span class="ss">this</span><span class="w">
│ │ │       </span><span class="ss">is</span><span class="w"> </span><span class="ss">an</span><span class="w"> </span><span class="ss">optional</span><span class="w"> </span><span class="ss">save</span><span class="w"> </span><span class="ss">slot</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="n">Erlang</span><span class="w"> </span><span class="ss">stack</span><span class="w"> </span><span class="ss">pointer</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="ss">executing</span><span class="w"> </span><span class="n">C</span><span class="w">
│ │ │       </span><span class="ss">code</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="nc">r12</span><span class="p">:</span><span class="w"> </span><span class="n">Active</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">index</span><span class="w">
│ │ │  </span><span class="nc">r13</span><span class="p">:</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="ss">running</span><span class="w"> </span><span class="ss">process</span><span class="w">
│ │ │  </span><span class="nc">r14</span><span class="p">:</span><span class="w"> </span><span class="n">Remaining</span><span class="w"> </span><span class="ss">reductions</span><span class="w">
│ │ │  </span><span class="nc">r15</span><span class="p">:</span><span class="w"> </span><span class="n">Erlang</span><span class="w"> </span><span class="ss">heap</span><span class="w"> </span><span class="ss">pointer</span></code></pre><p>Note that all of these are callee save registers under the System V and Windows
│ │ │ @@ -183,21 +183,21 @@
│ │ │  shared and only the arguments to the instructions vary. Using as little memory as
│ │ │  possible has many advantages; less memory is used, loading time decreases,
│ │ │  higher cache hit-rate.</p><p>In BeamAsm we need to achieve something similar since the load-time of a module
│ │ │  scales almost linearly with the amount of memory it uses. Early BeamAsm prototypes
│ │ │  used about double the amount of memory for code as the interpreter, while current
│ │ │  versions use about 10% more. How was this achieved?</p><p>In BeamAsm we heavily use shared code fragments to try to emit as much code as
│ │ │  possible as global shared fragments instead of duplicating the code unnecessarily.
│ │ │ -For instance, the return instruction looks something like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">Label</span><span class="w"> </span><span class="ss">yield</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">a</span><span class="p">.</span><span class="nf">newLabel</span><span class="p" data-group-id="2781162904-1">(</span><span class="p" data-group-id="2781162904-1">)</span><span class="p">;</span><span class="w">
│ │ │ +For instance, the return instruction looks something like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">Label</span><span class="w"> </span><span class="ss">yield</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">a</span><span class="p">.</span><span class="nf">newLabel</span><span class="p" data-group-id="0810271162-1">(</span><span class="p" data-group-id="0810271162-1">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">*</span><span class="w"> </span><span class="n">Decrement</span><span class="w"> </span><span class="ss">reduction</span><span class="w"> </span><span class="ss">counter</span><span class="w"> </span><span class="o">*</span><span class="o">/</span><span class="w">
│ │ │ -</span><span class="ss">a</span><span class="p">.</span><span class="nf">dec</span><span class="p" data-group-id="2781162904-2">(</span><span class="n">FCALLS</span><span class="p" data-group-id="2781162904-2">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="ss">a</span><span class="p">.</span><span class="nf">dec</span><span class="p" data-group-id="0810271162-2">(</span><span class="n">FCALLS</span><span class="p" data-group-id="0810271162-2">)</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="o">/</span><span class="o">*</span><span class="w"> </span><span class="n">If</span><span class="w"> </span><span class="n">FCALLS</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">jump</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">yield</span><span class="o">-</span><span class="ss">on</span><span class="o">-</span><span class="ss">return</span><span class="w"> </span><span class="ss">fragment</span><span class="w"> </span><span class="o">*</span><span class="o">/</span><span class="w">
│ │ │ -</span><span class="ss">a</span><span class="p">.</span><span class="nf">jl</span><span class="p" data-group-id="2781162904-3">(</span><span class="nf">resolve_fragment</span><span class="p" data-group-id="2781162904-4">(</span><span class="ss">ga</span><span class="p">-&gt;</span><span class="nf">get_dispatch_return</span><span class="p" data-group-id="2781162904-5">(</span><span class="p" data-group-id="2781162904-5">)</span><span class="p" data-group-id="2781162904-4">)</span><span class="p" data-group-id="2781162904-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="ss">a</span><span class="p">.</span><span class="nf">ret</span><span class="p" data-group-id="2781162904-6">(</span><span class="p" data-group-id="2781162904-6">)</span><span class="p">;</span></code></pre><p>The code above is not exactly what is emitted, but close enough. The thing to note
│ │ │ +</span><span class="ss">a</span><span class="p">.</span><span class="nf">jl</span><span class="p" data-group-id="0810271162-3">(</span><span class="nf">resolve_fragment</span><span class="p" data-group-id="0810271162-4">(</span><span class="ss">ga</span><span class="p">-&gt;</span><span class="nf">get_dispatch_return</span><span class="p" data-group-id="0810271162-5">(</span><span class="p" data-group-id="0810271162-5">)</span><span class="p" data-group-id="0810271162-4">)</span><span class="p" data-group-id="0810271162-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="ss">a</span><span class="p">.</span><span class="nf">ret</span><span class="p" data-group-id="0810271162-6">(</span><span class="p" data-group-id="0810271162-6">)</span><span class="p">;</span></code></pre><p>The code above is not exactly what is emitted, but close enough. The thing to note
│ │ │  is that the code for doing the context switch is never emitted. Instead, we jump
│ │ │  to a global fragment that all return instructions share. This greatly reduces
│ │ │  the amount of code that has to be emitted for each module.</p><h2 id="running-erlang-code" class="section-heading">
│ │ │    <a href="#running-erlang-code" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Running Erlang code</span>
│ │ │ @@ -239,43 +239,43 @@
│ │ │    <a href="#running-c-code" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Running C code</span>
│ │ │  </h2>
│ │ │  <p>As Erlang stacks can be very small, we have to switch over to a different stack
│ │ │  when we need to execute C code (which may expect a much larger stack). This is
│ │ │ -done through <code class="inline">emit_enter_runtime</code> and <code class="inline">emit_leave_runtime</code>, for example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">mov_arg</span><span class="p" data-group-id="3897223042-1">(</span><span class="n">ARG4</span><span class="p">,</span><span class="w"> </span><span class="n">NumFree</span><span class="p" data-group-id="3897223042-1">)</span><span class="p">;</span><span class="w">
│ │ │ +done through <code class="inline">emit_enter_runtime</code> and <code class="inline">emit_leave_runtime</code>, for example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">mov_arg</span><span class="p" data-group-id="0201105350-1">(</span><span class="n">ARG4</span><span class="p">,</span><span class="w"> </span><span class="n">NumFree</span><span class="p" data-group-id="0201105350-1">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">*</span><span class="w"> </span><span class="n">Move</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="ss">stack</span><span class="w"> </span><span class="ow">and</span><span class="w"> </span><span class="ss">swap</span><span class="w"> </span><span class="ss">out</span><span class="w"> </span><span class="ss">our</span><span class="w"> </span><span class="ss">current</span><span class="w"> </span><span class="ss">reductions</span><span class="p">,</span><span class="w"> </span><span class="ss">stack</span><span class="o">-</span><span class="p">,</span><span class="w"> </span><span class="ow">and</span><span class="w">
│ │ │   </span><span class="o">*</span><span class="w"> </span><span class="ss">heap</span><span class="w"> </span><span class="ss">pointer</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">process</span><span class="w"> </span><span class="ss">structure</span><span class="p">.</span><span class="w"> </span><span class="o">*</span><span class="o">/</span><span class="w">
│ │ │ -</span><span class="ss">emit_enter_runtime</span><span class="o">&lt;</span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eReductions</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eStack</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eHeap</span><span class="o">&gt;</span><span class="p" data-group-id="3897223042-2">(</span><span class="p" data-group-id="3897223042-2">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="ss">emit_enter_runtime</span><span class="o">&lt;</span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eReductions</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eStack</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eHeap</span><span class="o">&gt;</span><span class="p" data-group-id="0201105350-2">(</span><span class="p" data-group-id="0201105350-2">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">a</span><span class="p">.</span><span class="nf">mov</span><span class="p" data-group-id="3897223042-3">(</span><span class="n">ARG1</span><span class="p">,</span><span class="w"> </span><span class="ss">c_p</span><span class="p" data-group-id="3897223042-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">load_x_reg_array</span><span class="p" data-group-id="3897223042-4">(</span><span class="n">ARG2</span><span class="p" data-group-id="3897223042-4">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">make_move_patch</span><span class="p" data-group-id="3897223042-5">(</span><span class="n">ARG3</span><span class="p">,</span><span class="w"> </span><span class="ss">lambdas</span><span class="p" data-group-id="3897223042-6">[</span><span class="n">Fun</span><span class="p">.</span><span class="nf">getValue</span><span class="p" data-group-id="3897223042-7">(</span><span class="p" data-group-id="3897223042-7">)</span><span class="p" data-group-id="3897223042-6">]</span><span class="p">.</span><span class="ss">patches</span><span class="p" data-group-id="3897223042-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="ss">a</span><span class="p">.</span><span class="nf">mov</span><span class="p" data-group-id="0201105350-3">(</span><span class="n">ARG1</span><span class="p">,</span><span class="w"> </span><span class="ss">c_p</span><span class="p" data-group-id="0201105350-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">load_x_reg_array</span><span class="p" data-group-id="0201105350-4">(</span><span class="n">ARG2</span><span class="p" data-group-id="0201105350-4">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">make_move_patch</span><span class="p" data-group-id="0201105350-5">(</span><span class="n">ARG3</span><span class="p">,</span><span class="w"> </span><span class="ss">lambdas</span><span class="p" data-group-id="0201105350-6">[</span><span class="n">Fun</span><span class="p">.</span><span class="nf">getValue</span><span class="p" data-group-id="0201105350-7">(</span><span class="p" data-group-id="0201105350-7">)</span><span class="p" data-group-id="0201105350-6">]</span><span class="p">.</span><span class="ss">patches</span><span class="p" data-group-id="0201105350-5">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">*</span><span class="w"> </span><span class="n">Call</span><span class="w"> </span><span class="err">`</span><span class="ss">new_fun</span><span class="err">`</span><span class="p">,</span><span class="w"> </span><span class="ss">asserting</span><span class="w"> </span><span class="ss">that</span><span class="w"> </span><span class="ss">we</span><span class="err">&#39;</span><span class="ss">re</span><span class="w"> </span><span class="ss">on</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="ss">stack</span><span class="p">.</span><span class="w"> </span><span class="o">*</span><span class="o">/</span><span class="w">
│ │ │ -</span><span class="ss">runtime_call</span><span class="o">&lt;</span><span class="mi">4</span><span class="o">&gt;</span><span class="p" data-group-id="3897223042-8">(</span><span class="ss">new_fun</span><span class="p" data-group-id="3897223042-8">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="ss">runtime_call</span><span class="o">&lt;</span><span class="mi">4</span><span class="o">&gt;</span><span class="p" data-group-id="0201105350-8">(</span><span class="ss">new_fun</span><span class="p" data-group-id="0201105350-8">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">*</span><span class="w"> </span><span class="n">Move</span><span class="w"> </span><span class="ss">back</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="ss">stack</span><span class="p">,</span><span class="w"> </span><span class="ow">and</span><span class="w"> </span><span class="ss">read</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">updated</span><span class="w"> </span><span class="ss">values</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">process</span><span class="w">
│ │ │   </span><span class="o">*</span><span class="w"> </span><span class="ss">structure</span><span class="w"> </span><span class="o">*</span><span class="o">/</span><span class="w">
│ │ │ -</span><span class="ss">emit_leave_runtime</span><span class="o">&lt;</span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eReductions</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eStack</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eHeap</span><span class="o">&gt;</span><span class="p" data-group-id="3897223042-9">(</span><span class="p" data-group-id="3897223042-9">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="ss">emit_leave_runtime</span><span class="o">&lt;</span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eReductions</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eStack</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eHeap</span><span class="o">&gt;</span><span class="p" data-group-id="0201105350-9">(</span><span class="p" data-group-id="0201105350-9">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">a</span><span class="p">.</span><span class="nf">mov</span><span class="p" data-group-id="3897223042-10">(</span><span class="nf">getXRef</span><span class="p" data-group-id="3897223042-11">(</span><span class="mi">0</span><span class="p" data-group-id="3897223042-11">)</span><span class="p">,</span><span class="w"> </span><span class="n">RET</span><span class="p" data-group-id="3897223042-10">)</span><span class="p">;</span></code></pre><p>All combinations of the <code class="inline">Update</code> constants are legal, but the ones given to
│ │ │ +</span><span class="ss">a</span><span class="p">.</span><span class="nf">mov</span><span class="p" data-group-id="0201105350-10">(</span><span class="nf">getXRef</span><span class="p" data-group-id="0201105350-11">(</span><span class="mi">0</span><span class="p" data-group-id="0201105350-11">)</span><span class="p">,</span><span class="w"> </span><span class="n">RET</span><span class="p" data-group-id="0201105350-10">)</span><span class="p">;</span></code></pre><p>All combinations of the <code class="inline">Update</code> constants are legal, but the ones given to
│ │ │  <code class="inline">emit_leave_runtime</code> <em>must</em> be the same as those given to <code class="inline">emit_enter_runtime</code>.</p><h2 id="tracing-and-nif-loading" class="section-heading">
│ │ │    <a href="#tracing-and-nif-loading" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Tracing and NIF Loading</span>
│ │ │  </h2>
│ │ │  <p>To make tracing and NIF loading work there needs to be a way to intercept
│ │ │  any function call. In the interpreter, this is done by rewriting the loaded
│ │ │  BEAM code, but this is more complicated in BeamAsm as we want to have a fast
│ │ │  and compact way to do this. This is solved by emitting the code below at the
│ │ │ -start of each function (x86 variant below):</p><pre><code class="makeup erlang" translate="no"><span class="w">  </span><span class="mi">0</span><span class="nc">x0</span><span class="p">:</span><span class="w"> </span><span class="ss">short</span><span class="w"> </span><span class="ss">jmp</span><span class="w"> </span><span class="mi">6</span><span class="w"> </span><span class="p" data-group-id="9316870971-1">(</span><span class="ss">address</span><span class="w"> </span><span class="mi">0</span><span class="ss">x8</span><span class="p" data-group-id="9316870971-1">)</span><span class="w">
│ │ │ +start of each function (x86 variant below):</p><pre><code class="makeup erlang" translate="no"><span class="w">  </span><span class="mi">0</span><span class="nc">x0</span><span class="p">:</span><span class="w"> </span><span class="ss">short</span><span class="w"> </span><span class="ss">jmp</span><span class="w"> </span><span class="mi">6</span><span class="w"> </span><span class="p" data-group-id="6147683889-1">(</span><span class="ss">address</span><span class="w"> </span><span class="mi">0</span><span class="ss">x8</span><span class="p" data-group-id="6147683889-1">)</span><span class="w">
│ │ │    </span><span class="mi">0</span><span class="nc">x2</span><span class="p">:</span><span class="w"> </span><span class="ss">nop</span><span class="w">
│ │ │    </span><span class="mi">0</span><span class="nc">x3</span><span class="p">:</span><span class="w"> </span><span class="ss">relative</span><span class="w"> </span><span class="ss">near</span><span class="w"> </span><span class="ss">call</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">shared</span><span class="w"> </span><span class="ss">breakpoint</span><span class="w"> </span><span class="ss">fragment</span><span class="w">
│ │ │    </span><span class="mi">0</span><span class="nc">x8</span><span class="p">:</span><span class="w"> </span><span class="ss">actual</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">function</span></code></pre><p>When code starts to execute it will simply see the <code class="inline">short jmp 6</code> instruction
│ │ │  which skips the prologue and starts to execute the code directly.</p><p>When we want to enable a certain breakpoint we set the jmp target to be 1,
│ │ │  which means it will land on the call to the shared breakpoint fragment. This
│ │ │  fragment checks the current <code class="inline">breakpoint_flag</code> stored in the ErtsCodeInfo of
│ │ │  this function, and then calls <code class="inline">erts_call_nif_early</code> and
│ │ │ @@ -289,31 +289,31 @@
│ │ │    <span class="text">Updating code</span>
│ │ │  </h3>
│ │ │  <p>Because many environments enforce <a href="https://en.wikipedia.org/wiki/W%5EX" title="">W^X</a> it's not always possible to write
│ │ │  directly to the code pages. Because of this we map code twice: once with an
│ │ │  executable page and once with a writable page. Since they're backed by the
│ │ │  same memory, writes to the writable page appear magically in the executable
│ │ │  one.</p><p>The <code class="inline">erts_writable_code_ptr</code> function can be used to get writable pointers
│ │ │ -given a module instance, provided that it has been unsealed first:</p><pre><code class="makeup erlang" translate="no"><span class="nf">for</span><span class="w"> </span><span class="p" data-group-id="9833993436-1">(</span><span class="ss">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="ss">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="ss">n</span><span class="p">;</span><span class="w"> </span><span class="ss">i</span><span class="o">++</span><span class="p" data-group-id="9833993436-1">)</span><span class="w"> </span><span class="p" data-group-id="9833993436-2">{</span><span class="w">
│ │ │ +given a module instance, provided that it has been unsealed first:</p><pre><code class="makeup erlang" translate="no"><span class="nf">for</span><span class="w"> </span><span class="p" data-group-id="8580945301-1">(</span><span class="ss">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="ss">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="ss">n</span><span class="p">;</span><span class="w"> </span><span class="ss">i</span><span class="o">++</span><span class="p" data-group-id="8580945301-1">)</span><span class="w"> </span><span class="p" data-group-id="8580945301-2">{</span><span class="w">
│ │ │      </span><span class="ss">const</span><span class="w"> </span><span class="n">ErtsCodeInfo</span><span class="o">*</span><span class="w"> </span><span class="ss">ci_exec</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">ErtsCodeInfo</span><span class="o">*</span><span class="w"> </span><span class="ss">ci_rw</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">void</span><span class="w"> </span><span class="o">*</span><span class="ss">w_ptr</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nf">erts_unseal_module</span><span class="p" data-group-id="9833993436-3">(</span><span class="err">&amp;</span><span class="ss">modp</span><span class="p">-&gt;</span><span class="ss">curr</span><span class="p" data-group-id="9833993436-3">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nf">erts_unseal_module</span><span class="p" data-group-id="8580945301-3">(</span><span class="err">&amp;</span><span class="ss">modp</span><span class="p">-&gt;</span><span class="ss">curr</span><span class="p" data-group-id="8580945301-3">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="ss">ci_exec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">code_hdr</span><span class="p">-&gt;</span><span class="ss">functions</span><span class="p" data-group-id="9833993436-4">[</span><span class="ss">i</span><span class="p" data-group-id="9833993436-4">]</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">w_ptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erts_writable_code_ptr</span><span class="p" data-group-id="9833993436-5">(</span><span class="err">&amp;</span><span class="ss">modp</span><span class="p">-&gt;</span><span class="ss">curr</span><span class="p">,</span><span class="w"> </span><span class="ss">ci_exec</span><span class="p" data-group-id="9833993436-5">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">ci_rw</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9833993436-6">(</span><span class="n">ErtsCodeInfo</span><span class="o">*</span><span class="p" data-group-id="9833993436-6">)</span><span class="ss">w_ptr</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">ci_exec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">code_hdr</span><span class="p">-&gt;</span><span class="ss">functions</span><span class="p" data-group-id="8580945301-4">[</span><span class="ss">i</span><span class="p" data-group-id="8580945301-4">]</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">w_ptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erts_writable_code_ptr</span><span class="p" data-group-id="8580945301-5">(</span><span class="err">&amp;</span><span class="ss">modp</span><span class="p">-&gt;</span><span class="ss">curr</span><span class="p">,</span><span class="w"> </span><span class="ss">ci_exec</span><span class="p" data-group-id="8580945301-5">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">ci_rw</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8580945301-6">(</span><span class="n">ErtsCodeInfo</span><span class="o">*</span><span class="p" data-group-id="8580945301-6">)</span><span class="ss">w_ptr</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nf">uninstall_breakpoint</span><span class="p" data-group-id="9833993436-7">(</span><span class="ss">ci_rw</span><span class="p">,</span><span class="w"> </span><span class="ss">ci_exec</span><span class="p" data-group-id="9833993436-7">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="nf">consolidate_bp_data</span><span class="p" data-group-id="9833993436-8">(</span><span class="ss">modp</span><span class="p">,</span><span class="w"> </span><span class="ss">ci_rw</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="9833993436-8">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="9833993436-9">(</span><span class="ss">ci_rw</span><span class="p">-&gt;</span><span class="ss">gen_bp</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">NULL</span><span class="p" data-group-id="9833993436-9">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nf">uninstall_breakpoint</span><span class="p" data-group-id="8580945301-7">(</span><span class="ss">ci_rw</span><span class="p">,</span><span class="w"> </span><span class="ss">ci_exec</span><span class="p" data-group-id="8580945301-7">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nf">consolidate_bp_data</span><span class="p" data-group-id="8580945301-8">(</span><span class="ss">modp</span><span class="p">,</span><span class="w"> </span><span class="ss">ci_rw</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="8580945301-8">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="8580945301-9">(</span><span class="ss">ci_rw</span><span class="p">-&gt;</span><span class="ss">gen_bp</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">NULL</span><span class="p" data-group-id="8580945301-9">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nf">erts_seal_module</span><span class="p" data-group-id="9833993436-10">(</span><span class="err">&amp;</span><span class="ss">modp</span><span class="p">-&gt;</span><span class="ss">curr</span><span class="p" data-group-id="9833993436-10">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9833993436-2">}</span></code></pre><p>Without the module instance there's no reliable way to figure out the writable
│ │ │ +    </span><span class="nf">erts_seal_module</span><span class="p" data-group-id="8580945301-10">(</span><span class="err">&amp;</span><span class="ss">modp</span><span class="p">-&gt;</span><span class="ss">curr</span><span class="p" data-group-id="8580945301-10">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8580945301-2">}</span></code></pre><p>Without the module instance there's no reliable way to figure out the writable
│ │ │  address of a code page, and we rely on <em>address space layout randomization</em>
│ │ │  (ASLR) to make it difficult to guess. On some platforms, security is further
│ │ │  enhanced by protecting the writable area from writes until the module has been
│ │ │  unsealed by <code class="inline">erts_unseal_module</code>.</p><h3 id="export-tracing" class="section-heading">
│ │ │    <a href="#export-tracing" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -393,15 +393,15 @@
│ │ │  </span><span class="ss">perf</span><span class="w"> </span><span class="ss">script</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="ss">out</span><span class="p">.</span><span class="ss">perf</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="p">#</span><span class="w"> </span><span class="ss">run</span><span class="w"> </span><span class="ss">stackcollapse</span><span class="w">
│ │ │  </span><span class="ss">stackcollapse</span><span class="o">-</span><span class="ss">perf</span><span class="p">.</span><span class="ss">pl</span><span class="w"> </span><span class="ss">out</span><span class="p">.</span><span class="ss">perf</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="ss">out</span><span class="p">.</span><span class="ss">folded</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="p">#</span><span class="w"> </span><span class="n">Create</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">svg</span><span class="w">
│ │ │  </span><span class="ss">flamegraph</span><span class="p">.</span><span class="ss">pl</span><span class="w"> </span><span class="ss">out</span><span class="p">.</span><span class="ss">folded</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="ss">out</span><span class="p">.</span><span class="ss">svg</span></code></pre><p>We get a graph that would look something like this:</p><p><img src="assets/perf-beamasm.svg" alt="Linux Perf FlameGraph: dialyzer PLT build"/></p><p>You can view a larger version <a href="assets/perf-beamasm.svg">here</a>. It contains
│ │ │  the same information, but it is easier to share with others as it does
│ │ │  not need the symbols in the executable.</p><p>Using the same data we can also produce a graph where the scheduler profile data
│ │ │ -has been merged by using <code class="inline">sed</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">#</span><span class="p">#</span><span class="w"> </span><span class="n">Strip</span><span class="w"> </span><span class="p" data-group-id="5507222633-1">[</span><span class="mi">0</span><span class="o">-</span><span class="mi">9</span><span class="p" data-group-id="5507222633-1">]</span><span class="o">+</span><span class="p">_</span><span class="w"> </span><span class="ow">and</span><span class="o">/</span><span class="ow">or</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="5507222633-2">[</span><span class="mi">0</span><span class="o">-</span><span class="mi">9</span><span class="p" data-group-id="5507222633-2">]</span><span class="o">+</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">all</span><span class="w"> </span><span class="ss">scheduler</span><span class="w"> </span><span class="ss">names</span><span class="w">
│ │ │ +has been merged by using <code class="inline">sed</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">#</span><span class="p">#</span><span class="w"> </span><span class="n">Strip</span><span class="w"> </span><span class="p" data-group-id="5999050398-1">[</span><span class="mi">0</span><span class="o">-</span><span class="mi">9</span><span class="p" data-group-id="5999050398-1">]</span><span class="o">+</span><span class="p">_</span><span class="w"> </span><span class="ow">and</span><span class="o">/</span><span class="ow">or</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="5999050398-2">[</span><span class="mi">0</span><span class="o">-</span><span class="mi">9</span><span class="p" data-group-id="5999050398-2">]</span><span class="o">+</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">all</span><span class="w"> </span><span class="ss">scheduler</span><span class="w"> </span><span class="ss">names</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="p">#</span><span class="w"> </span><span class="ss">scheduler</span><span class="w"> </span><span class="ss">names</span><span class="w"> </span><span class="ss">changed</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="n">OTP26</span><span class="p">,</span><span class="w"> </span><span class="ss">hence</span><span class="w"> </span><span class="ss">two</span><span class="w"> </span><span class="ss">expressions</span><span class="w">
│ │ │  </span><span class="ss">sed</span><span class="w"> </span><span class="o">-</span><span class="ss">e</span><span class="w"> </span><span class="ss">&#39;s/^[0-9]\+_//&#39;</span><span class="w"> </span><span class="o">-</span><span class="ss">e</span><span class="w"> </span><span class="ss">&#39;s/^erts_\([^_]\+\)_[0-9]\+/erts_\1/&#39;</span><span class="w"> </span><span class="ss">out</span><span class="p">.</span><span class="ss">folded</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="ss">out</span><span class="p">.</span><span class="ss">folded_sched</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="p">#</span><span class="w"> </span><span class="n">Create</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">svg</span><span class="w">
│ │ │  </span><span class="ss">flamegraph</span><span class="p">.</span><span class="ss">pl</span><span class="w"> </span><span class="ss">out</span><span class="p">.</span><span class="ss">folded_sched</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="ss">out_sched</span><span class="p">.</span><span class="ss">svg</span></code></pre><p><img src="assets/perf-beamasm-merged.svg" alt="Linux Perf FlameGraph: dialyzer PLT build"/></p><p>You can view a larger version <a href="assets/perf-beamasm-merged.svg">here</a>.
│ │ │  There are many different transformations that you can do to make the graph show
│ │ │  you what you want.</p><h3 id="annotate-perf-functions" class="section-heading">
│ │ │    <a href="#annotate-perf-functions" class="hover-link">
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-17.0/doc/html/codeloading.html
│ │ │ @@ -163,16 +163,16 @@
│ │ │  only be done by one loader process at a time. A second loader process
│ │ │  trying to enter finishing phase will be suspended until the first
│ │ │  loader is done. This will only block the process, the scheduler is
│ │ │  free to schedule other work while the second loader is waiting. (See
│ │ │  <code class="inline">erts_try_seize_code_load_permission</code> and
│ │ │  <code class="inline">erts_release_code_load_permission</code>).</p><p>The ability to prepare several modules in parallel is not currently
│ │ │  used as almost all code loading is serialized by the code_server
│ │ │ -process. The BIF interface is however prepared for this.</p><pre><code class="makeup erlang" translate="no"><span class="w">  </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">prepare_loading</span><span class="p" data-group-id="3071945753-1">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="3071945753-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">LoaderState</span><span class="w">
│ │ │ -  </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">finish_loading</span><span class="p" data-group-id="3071945753-2">(</span><span class="p" data-group-id="3071945753-3">[</span><span class="n">LoaderState</span><span class="p" data-group-id="3071945753-3">]</span><span class="p" data-group-id="3071945753-2">)</span></code></pre><p>The idea is that <code class="inline">prepare_loading</code> could be called in parallel for
│ │ │ +process. The BIF interface is however prepared for this.</p><pre><code class="makeup erlang" translate="no"><span class="w">  </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">prepare_loading</span><span class="p" data-group-id="9646149832-1">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="9646149832-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">LoaderState</span><span class="w">
│ │ │ +  </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">finish_loading</span><span class="p" data-group-id="9646149832-2">(</span><span class="p" data-group-id="9646149832-3">[</span><span class="n">LoaderState</span><span class="p" data-group-id="9646149832-3">]</span><span class="p" data-group-id="9646149832-2">)</span></code></pre><p>The idea is that <code class="inline">prepare_loading</code> could be called in parallel for
│ │ │  different modules and returns a &quot;magic binary&quot; containing the internal
│ │ │  state of each prepared module. Function <code class="inline">finish_loading</code> could take a
│ │ │  list of such states and do the finishing of all of them in one go.</p><p>Currently we use the legacy BIF <code class="inline">erlang:load_module</code> which is now
│ │ │  implemented in Erlang by calling the above two functions in
│ │ │  sequence. Function <code class="inline">finish_loading</code> is limited to only accepts a list
│ │ │  with one module state as we do not yet use the multi module loading
│ │ │  feature.</p><h2 id="the-finishing-sequence" class="section-heading">
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-17.0/doc/html/crash_dump.html
│ │ │ @@ -401,21 +401,21 @@
│ │ │  <a href="erlang.html#put/2"><code class="inline">put/2</code></a> and <a href="erlang.html#get/1"><code class="inline">get/1</code></a> thing) is non-empty.</p><p>The raw memory information can be decoded by the Crashdump Viewer tool. You can
│ │ │  then see the stack dump, the message queue (if any), and the dictionary (if
│ │ │  any).</p><p>The stack dump is a dump of the Erlang process stack. Most of the live data
│ │ │  (that is, variables currently in use) are placed on the stack; thus this can be
│ │ │  interesting. One has to &quot;guess&quot; what is what, but as the information is
│ │ │  symbolic, thorough reading of this information can be useful. As an example, we
│ │ │  can find the state variable of the Erlang primitive loader online <code class="inline">(5)</code> and
│ │ │ -<code class="inline">(6)</code> in the following example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3244306342-1">(</span><span class="mi">1</span><span class="p" data-group-id="3244306342-1">)</span><span class="w">  </span><span class="mi">3</span><span class="ss">cac44</span><span class="w">   </span><span class="n">Return</span><span class="w"> </span><span class="ss">addr</span><span class="w"> </span><span class="mi">0</span><span class="nf">x13BF58</span><span class="w"> </span><span class="p" data-group-id="3244306342-2">(</span><span class="o">&lt;</span><span class="ss">terminate</span><span class="w"> </span><span class="ss">process</span><span class="w"> </span><span class="ss">normally</span><span class="o">&gt;</span><span class="p" data-group-id="3244306342-2">)</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3244306342-3">(</span><span class="mi">2</span><span class="p" data-group-id="3244306342-3">)</span><span class="w">  </span><span class="nf">y</span><span class="p" data-group-id="3244306342-4">(</span><span class="mi">0</span><span class="p" data-group-id="3244306342-4">)</span><span class="w">     </span><span class="p" data-group-id="3244306342-5">[</span><span class="s">&quot;/view/siri_r10_dev/clearcase/otp/erts/lib/kernel/ebin&quot;</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3244306342-6">(</span><span class="mi">3</span><span class="p" data-group-id="3244306342-6">)</span><span class="w">            </span><span class="s">&quot;/view/siri_r10_dev/clearcase/otp/erts/lib/stdlib/ebin&quot;</span><span class="p" data-group-id="3244306342-5">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3244306342-7">(</span><span class="mi">4</span><span class="p" data-group-id="3244306342-7">)</span><span class="w">  </span><span class="nf">y</span><span class="p" data-group-id="3244306342-8">(</span><span class="mi">1</span><span class="p" data-group-id="3244306342-8">)</span><span class="w">     </span><span class="o">&lt;</span><span class="mf">0.1</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3244306342-9">(</span><span class="mi">5</span><span class="p" data-group-id="3244306342-9">)</span><span class="w">  </span><span class="nf">y</span><span class="p" data-group-id="3244306342-10">(</span><span class="mi">2</span><span class="p" data-group-id="3244306342-10">)</span><span class="w">     </span><span class="p" data-group-id="3244306342-11">{</span><span class="ss">state</span><span class="p">,</span><span class="p" data-group-id="3244306342-12">[</span><span class="p" data-group-id="3244306342-12">]</span><span class="p">,</span><span class="ss">none</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_prim_loader</span><span class="p">.</span><span class="mf">6.7085890</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">undefined</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_prim_loader</span><span class="p">.</span><span class="mf">7.9000327</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3244306342-13">(</span><span class="mi">6</span><span class="p" data-group-id="3244306342-13">)</span><span class="w">            </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_prim_loader</span><span class="p">.</span><span class="mf">8.116480692</span><span class="o">&gt;</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.2</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">infinity</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_prim_loader</span><span class="p">.</span><span class="mf">9.10708760</span><span class="o">&gt;</span><span class="p" data-group-id="3244306342-11">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3244306342-14">(</span><span class="mi">7</span><span class="p" data-group-id="3244306342-14">)</span><span class="w">  </span><span class="nf">y</span><span class="p" data-group-id="3244306342-15">(</span><span class="mi">3</span><span class="p" data-group-id="3244306342-15">)</span><span class="w">     </span><span class="ss">infinity</span></code></pre><p>When interpreting the data for a process, it is helpful to know that anonymous
│ │ │ +<code class="inline">(6)</code> in the following example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9078334976-1">(</span><span class="mi">1</span><span class="p" data-group-id="9078334976-1">)</span><span class="w">  </span><span class="mi">3</span><span class="ss">cac44</span><span class="w">   </span><span class="n">Return</span><span class="w"> </span><span class="ss">addr</span><span class="w"> </span><span class="mi">0</span><span class="nf">x13BF58</span><span class="w"> </span><span class="p" data-group-id="9078334976-2">(</span><span class="o">&lt;</span><span class="ss">terminate</span><span class="w"> </span><span class="ss">process</span><span class="w"> </span><span class="ss">normally</span><span class="o">&gt;</span><span class="p" data-group-id="9078334976-2">)</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9078334976-3">(</span><span class="mi">2</span><span class="p" data-group-id="9078334976-3">)</span><span class="w">  </span><span class="nf">y</span><span class="p" data-group-id="9078334976-4">(</span><span class="mi">0</span><span class="p" data-group-id="9078334976-4">)</span><span class="w">     </span><span class="p" data-group-id="9078334976-5">[</span><span class="s">&quot;/view/siri_r10_dev/clearcase/otp/erts/lib/kernel/ebin&quot;</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9078334976-6">(</span><span class="mi">3</span><span class="p" data-group-id="9078334976-6">)</span><span class="w">            </span><span class="s">&quot;/view/siri_r10_dev/clearcase/otp/erts/lib/stdlib/ebin&quot;</span><span class="p" data-group-id="9078334976-5">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9078334976-7">(</span><span class="mi">4</span><span class="p" data-group-id="9078334976-7">)</span><span class="w">  </span><span class="nf">y</span><span class="p" data-group-id="9078334976-8">(</span><span class="mi">1</span><span class="p" data-group-id="9078334976-8">)</span><span class="w">     </span><span class="o">&lt;</span><span class="mf">0.1</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9078334976-9">(</span><span class="mi">5</span><span class="p" data-group-id="9078334976-9">)</span><span class="w">  </span><span class="nf">y</span><span class="p" data-group-id="9078334976-10">(</span><span class="mi">2</span><span class="p" data-group-id="9078334976-10">)</span><span class="w">     </span><span class="p" data-group-id="9078334976-11">{</span><span class="ss">state</span><span class="p">,</span><span class="p" data-group-id="9078334976-12">[</span><span class="p" data-group-id="9078334976-12">]</span><span class="p">,</span><span class="ss">none</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_prim_loader</span><span class="p">.</span><span class="mf">6.7085890</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">undefined</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_prim_loader</span><span class="p">.</span><span class="mf">7.9000327</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9078334976-13">(</span><span class="mi">6</span><span class="p" data-group-id="9078334976-13">)</span><span class="w">            </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_prim_loader</span><span class="p">.</span><span class="mf">8.116480692</span><span class="o">&gt;</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.2</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">infinity</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_prim_loader</span><span class="p">.</span><span class="mf">9.10708760</span><span class="o">&gt;</span><span class="p" data-group-id="9078334976-11">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9078334976-14">(</span><span class="mi">7</span><span class="p" data-group-id="9078334976-14">)</span><span class="w">  </span><span class="nf">y</span><span class="p" data-group-id="9078334976-15">(</span><span class="mi">3</span><span class="p" data-group-id="9078334976-15">)</span><span class="w">     </span><span class="ss">infinity</span></code></pre><p>When interpreting the data for a process, it is helpful to know that anonymous
│ │ │  function objects (funs) are given the following:</p><ul><li>A name constructed from the name of the function in which they are created</li><li>A number (starting with 0) indicating the number of that fun within that
│ │ │  function</li></ul><h2 id="atoms" class="section-heading">
│ │ │    <a href="#atoms" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Atoms</span>
│ │ │  </h2>
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-17.0/doc/html/driver.html
│ │ │ @@ -364,41 +364,41 @@
│ │ │  <p>Before a driver can be called from Erlang, it must be loaded and opened. Loading
│ │ │  is done using the <a href="../../../lib/kernel-11.0/doc/html/erl_ddll.html"><code class="inline">erl_ddll</code></a> module (the <a href="../../../lib/kernel-11.0/doc/html/erl_ddll.html"><code class="inline">erl_ddll</code></a> driver that loads dynamic
│ │ │  driver is actually a driver itself). If loading is successful, the port can be
│ │ │  opened with <a href="erlang.html#open_port/2"><code class="inline">open_port/2</code></a>. The port name must match the name of
│ │ │  the shared library and the name in the driver entry structure.</p><p>When the port has been opened, the driver can be called. In the <code class="inline">pg_sync</code>
│ │ │  example, we do not have any data from the port, only the return value from the
│ │ │  <a href="erlang.html#port_control/3"><code class="inline">port_control/3</code></a>.</p><p>The following code is the Erlang part of the synchronous postgres driver,
│ │ │ -<code class="inline">pg_sync.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4130536492-1">(</span><span class="ss">pg_sync</span><span class="p" data-group-id="4130536492-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">pg_sync.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7476974781-1">(</span><span class="ss">pg_sync</span><span class="p" data-group-id="7476974781-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4130536492-2">(</span><span class="n">DRV_CONNECT</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="4130536492-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4130536492-3">(</span><span class="n">DRV_DISCONNECT</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="4130536492-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4130536492-4">(</span><span class="n">DRV_SELECT</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="4130536492-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7476974781-2">(</span><span class="n">DRV_CONNECT</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="7476974781-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7476974781-3">(</span><span class="n">DRV_DISCONNECT</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="7476974781-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7476974781-4">(</span><span class="n">DRV_SELECT</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="7476974781-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4130536492-5">(</span><span class="p" data-group-id="4130536492-6">[</span><span class="ss">connect</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">disconnect</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">select</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4130536492-6">]</span><span class="p" data-group-id="4130536492-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7476974781-5">(</span><span class="p" data-group-id="7476974781-6">[</span><span class="ss">connect</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">disconnect</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">select</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7476974781-6">]</span><span class="p" data-group-id="7476974781-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">connect</span><span class="p" data-group-id="4130536492-7">(</span><span class="n">ConnectStr</span><span class="p" data-group-id="4130536492-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="4130536492-8">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;pg_sync&quot;</span><span class="p" data-group-id="4130536492-8">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">connect</span><span class="p" data-group-id="7476974781-7">(</span><span class="n">ConnectStr</span><span class="p" data-group-id="7476974781-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="7476974781-8">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;pg_sync&quot;</span><span class="p" data-group-id="7476974781-8">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="4130536492-9">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="4130536492-9">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="n">E</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="4130536492-10">(</span><span class="p" data-group-id="4130536492-11">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="p" data-group-id="4130536492-11">}</span><span class="p" data-group-id="4130536492-10">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7476974781-9">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="7476974781-9">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="n">E</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="7476974781-10">(</span><span class="p" data-group-id="7476974781-11">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="p" data-group-id="7476974781-11">}</span><span class="p" data-group-id="7476974781-10">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="4130536492-12">(</span><span class="p" data-group-id="4130536492-13">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p" data-group-id="4130536492-13">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4130536492-14">[</span><span class="p" data-group-id="4130536492-14">]</span><span class="p" data-group-id="4130536492-12">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="4130536492-15">(</span><span class="nf">port_control</span><span class="p" data-group-id="4130536492-16">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_CONNECT</span><span class="p">,</span><span class="w"> </span><span class="n">ConnectStr</span><span class="p" data-group-id="4130536492-16">)</span><span class="p" data-group-id="4130536492-15">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4130536492-17">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p" data-group-id="4130536492-17">}</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="7476974781-12">(</span><span class="p" data-group-id="7476974781-13">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p" data-group-id="7476974781-13">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7476974781-14">[</span><span class="p" data-group-id="7476974781-14">]</span><span class="p" data-group-id="7476974781-12">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="7476974781-15">(</span><span class="nf">port_control</span><span class="p" data-group-id="7476974781-16">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_CONNECT</span><span class="p">,</span><span class="w"> </span><span class="n">ConnectStr</span><span class="p" data-group-id="7476974781-16">)</span><span class="p" data-group-id="7476974781-15">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7476974781-17">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p" data-group-id="7476974781-17">}</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="n">Error</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Error</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">disconnect</span><span class="p" data-group-id="4130536492-18">(</span><span class="n">Port</span><span class="p" data-group-id="4130536492-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">R</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="4130536492-19">(</span><span class="nf">port_control</span><span class="p" data-group-id="4130536492-20">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_DISCONNECT</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p" data-group-id="4130536492-20">)</span><span class="p" data-group-id="4130536492-19">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">port_close</span><span class="p" data-group-id="4130536492-21">(</span><span class="n">Port</span><span class="p" data-group-id="4130536492-21">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">disconnect</span><span class="p" data-group-id="7476974781-18">(</span><span class="n">Port</span><span class="p" data-group-id="7476974781-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">R</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="7476974781-19">(</span><span class="nf">port_control</span><span class="p" data-group-id="7476974781-20">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_DISCONNECT</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p" data-group-id="7476974781-20">)</span><span class="p" data-group-id="7476974781-19">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">port_close</span><span class="p" data-group-id="7476974781-21">(</span><span class="n">Port</span><span class="p" data-group-id="7476974781-21">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="n">R</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">select</span><span class="p" data-group-id="4130536492-22">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Query</span><span class="p" data-group-id="4130536492-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">binary_to_term</span><span class="p" data-group-id="4130536492-23">(</span><span class="nf">port_control</span><span class="p" data-group-id="4130536492-24">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_SELECT</span><span class="p">,</span><span class="w"> </span><span class="n">Query</span><span class="p" data-group-id="4130536492-24">)</span><span class="p" data-group-id="4130536492-23">)</span><span class="p">.</span></code></pre><p>The API is simple:</p><ul><li><code class="inline">connect/1</code> loads the driver, opens it, and logs on to the database, returning
│ │ │ +</span><span class="nf">select</span><span class="p" data-group-id="7476974781-22">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Query</span><span class="p" data-group-id="7476974781-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">binary_to_term</span><span class="p" data-group-id="7476974781-23">(</span><span class="nf">port_control</span><span class="p" data-group-id="7476974781-24">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_SELECT</span><span class="p">,</span><span class="w"> </span><span class="n">Query</span><span class="p" data-group-id="7476974781-24">)</span><span class="p" data-group-id="7476974781-23">)</span><span class="p">.</span></code></pre><p>The API is simple:</p><ul><li><code class="inline">connect/1</code> loads the driver, opens it, and logs on to the database, returning
│ │ │  the Erlang port if successful.</li><li><code class="inline">select/2</code> sends a query to the driver and returns the result.</li><li><code class="inline">disconnect/1</code> closes the database connection and the driver. (However, it
│ │ │  does not unload it.)</li></ul><p>The connection string is to be a connection string for postgres.</p><p>The driver is loaded with <a href="../../../lib/kernel-11.0/doc/html/erl_ddll.html#load_driver/2"><code class="inline">erl_ddll:load_driver/2</code></a>. If this is successful, or if
│ │ │  it is already loaded, it is opened. This will call the <code class="inline">start</code> function in the
│ │ │  driver.</p><p>We use the <a href="erlang.html#port_control/3"><code class="inline">port_control/3</code></a> function for all calls into the
│ │ │  driver. The result from the driver is returned immediately and converted to
│ │ │  terms by calling <a href="erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a>. (We trust that the
│ │ │  terms returned from the driver are well-formed, otherwise the <a href="erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a>
│ │ │ @@ -536,51 +536,51 @@
│ │ │  successful, or error if it is not. If the connection is not yet established, we
│ │ │  simply return; <code class="inline">ready_io</code> is called again.</p><p>If we have a result from a connect, indicated by having data in the <code class="inline">x</code> buffer,
│ │ │  we no longer need to select on output (<a href="../../../erts-17.0/doc/html/driver_entry.html#ready_output" title=""><code class="inline">ready_output</code></a>), so we remove this by
│ │ │  calling <a href="../../../erts-17.0/doc/html/erl_driver.html#driver_select" title=""><code class="inline">driver_select</code></a>.</p><p>If we are not connecting, we wait for results from a <code class="inline">PQsendQuery</code>, so we get
│ │ │  the result and return it. The encoding is done with the same functions as in the
│ │ │  earlier example.</p><p>Error handling is to be added here, for example, checking that the socket is
│ │ │  still open, but this is only a simple example.</p><p>The Erlang part of the asynchronous driver consists of the sample file
│ │ │ -<code class="inline">pg_async.erl</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0585133786-1">(</span><span class="ss">pg_async</span><span class="p" data-group-id="0585133786-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">pg_async.erl</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9266841838-1">(</span><span class="ss">pg_async</span><span class="p" data-group-id="9266841838-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0585133786-2">(</span><span class="n">DRV_CONNECT</span><span class="p">,</span><span class="w"> </span><span class="sc">$C</span><span class="p" data-group-id="0585133786-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0585133786-3">(</span><span class="n">DRV_DISCONNECT</span><span class="p">,</span><span class="w"> </span><span class="sc">$D</span><span class="p" data-group-id="0585133786-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0585133786-4">(</span><span class="n">DRV_SELECT</span><span class="p">,</span><span class="w"> </span><span class="sc">$S</span><span class="p" data-group-id="0585133786-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9266841838-2">(</span><span class="n">DRV_CONNECT</span><span class="p">,</span><span class="w"> </span><span class="sc">$C</span><span class="p" data-group-id="9266841838-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9266841838-3">(</span><span class="n">DRV_DISCONNECT</span><span class="p">,</span><span class="w"> </span><span class="sc">$D</span><span class="p" data-group-id="9266841838-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9266841838-4">(</span><span class="n">DRV_SELECT</span><span class="p">,</span><span class="w"> </span><span class="sc">$S</span><span class="p" data-group-id="9266841838-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0585133786-5">(</span><span class="p" data-group-id="0585133786-6">[</span><span class="ss">connect</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">disconnect</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">select</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0585133786-6">]</span><span class="p" data-group-id="0585133786-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9266841838-5">(</span><span class="p" data-group-id="9266841838-6">[</span><span class="ss">connect</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">disconnect</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">select</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9266841838-6">]</span><span class="p" data-group-id="9266841838-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">connect</span><span class="p" data-group-id="0585133786-7">(</span><span class="n">ConnectStr</span><span class="p" data-group-id="0585133786-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="0585133786-8">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;pg_async&quot;</span><span class="p" data-group-id="0585133786-8">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">connect</span><span class="p" data-group-id="9266841838-7">(</span><span class="n">ConnectStr</span><span class="p" data-group-id="9266841838-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="9266841838-8">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;pg_async&quot;</span><span class="p" data-group-id="9266841838-8">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0585133786-9">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="0585133786-9">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="0585133786-10">(</span><span class="p" data-group-id="0585133786-11">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="0585133786-11">}</span><span class="p" data-group-id="0585133786-10">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9266841838-9">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="9266841838-9">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="9266841838-10">(</span><span class="p" data-group-id="9266841838-11">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="9266841838-11">}</span><span class="p" data-group-id="9266841838-10">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="0585133786-12">(</span><span class="p" data-group-id="0585133786-13">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p" data-group-id="0585133786-13">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0585133786-14">[</span><span class="ss">binary</span><span class="p" data-group-id="0585133786-14">]</span><span class="p" data-group-id="0585133786-12">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">port_control</span><span class="p" data-group-id="0585133786-15">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_CONNECT</span><span class="p">,</span><span class="w"> </span><span class="n">ConnectStr</span><span class="p" data-group-id="0585133786-15">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">return_port_data</span><span class="p" data-group-id="0585133786-16">(</span><span class="n">Port</span><span class="p" data-group-id="0585133786-16">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="9266841838-12">(</span><span class="p" data-group-id="9266841838-13">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p" data-group-id="9266841838-13">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9266841838-14">[</span><span class="ss">binary</span><span class="p" data-group-id="9266841838-14">]</span><span class="p" data-group-id="9266841838-12">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">port_control</span><span class="p" data-group-id="9266841838-15">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_CONNECT</span><span class="p">,</span><span class="w"> </span><span class="n">ConnectStr</span><span class="p" data-group-id="9266841838-15">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">return_port_data</span><span class="p" data-group-id="9266841838-16">(</span><span class="n">Port</span><span class="p" data-group-id="9266841838-16">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="0585133786-17">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p" data-group-id="0585133786-17">}</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="9266841838-17">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p" data-group-id="9266841838-17">}</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="n">Error</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="n">Error</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">disconnect</span><span class="p" data-group-id="0585133786-18">(</span><span class="n">Port</span><span class="p" data-group-id="0585133786-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">port_control</span><span class="p" data-group-id="0585133786-19">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_DISCONNECT</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p" data-group-id="0585133786-19">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">R</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">return_port_data</span><span class="p" data-group-id="0585133786-20">(</span><span class="n">Port</span><span class="p" data-group-id="0585133786-20">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">port_close</span><span class="p" data-group-id="0585133786-21">(</span><span class="n">Port</span><span class="p" data-group-id="0585133786-21">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">disconnect</span><span class="p" data-group-id="9266841838-18">(</span><span class="n">Port</span><span class="p" data-group-id="9266841838-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">port_control</span><span class="p" data-group-id="9266841838-19">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_DISCONNECT</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p" data-group-id="9266841838-19">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">R</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">return_port_data</span><span class="p" data-group-id="9266841838-20">(</span><span class="n">Port</span><span class="p" data-group-id="9266841838-20">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">port_close</span><span class="p" data-group-id="9266841838-21">(</span><span class="n">Port</span><span class="p" data-group-id="9266841838-21">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="n">R</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">select</span><span class="p" data-group-id="0585133786-22">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Query</span><span class="p" data-group-id="0585133786-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">port_control</span><span class="p" data-group-id="0585133786-23">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_SELECT</span><span class="p">,</span><span class="w"> </span><span class="n">Query</span><span class="p" data-group-id="0585133786-23">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">return_port_data</span><span class="p" data-group-id="0585133786-24">(</span><span class="n">Port</span><span class="p" data-group-id="0585133786-24">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">select</span><span class="p" data-group-id="9266841838-22">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Query</span><span class="p" data-group-id="9266841838-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">port_control</span><span class="p" data-group-id="9266841838-23">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_SELECT</span><span class="p">,</span><span class="w"> </span><span class="n">Query</span><span class="p" data-group-id="9266841838-23">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">return_port_data</span><span class="p" data-group-id="9266841838-24">(</span><span class="n">Port</span><span class="p" data-group-id="9266841838-24">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">return_port_data</span><span class="p" data-group-id="0585133786-25">(</span><span class="n">Port</span><span class="p" data-group-id="0585133786-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">return_port_data</span><span class="p" data-group-id="9266841838-25">(</span><span class="n">Port</span><span class="p" data-group-id="9266841838-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0585133786-26">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0585133786-27">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0585133786-27">}</span><span class="p" data-group-id="0585133786-26">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">binary_to_term</span><span class="p" data-group-id="0585133786-28">(</span><span class="n">Data</span><span class="p" data-group-id="0585133786-28">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9266841838-26">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9266841838-27">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9266841838-27">}</span><span class="p" data-group-id="9266841838-26">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">binary_to_term</span><span class="p" data-group-id="9266841838-28">(</span><span class="n">Data</span><span class="p" data-group-id="9266841838-28">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The Erlang code is slightly different, as we do not return the result
│ │ │  synchronously from <a href="erlang.html#port_control/3"><code class="inline">port_control/3</code></a>, instead we get it from <a href="../../../erts-17.0/doc/html/erl_driver.html#driver_output" title=""><code class="inline">driver_output</code></a> as
│ │ │  data in the message queue. The function <code class="inline">return_port_data</code> above receives data
│ │ │  from the port. As the data is in binary format, we use
│ │ │  <a href="erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a> to convert it to an Erlang term. Notice
│ │ │  that the driver is opened in binary mode (<a href="erlang.html#open_port/2"><code class="inline">open_port/2</code></a> is
│ │ │  called with option <code class="inline">[binary]</code>). This means that data sent from the driver to the
│ │ │ @@ -677,59 +677,59 @@
│ │ │      *rp++ = ERL_DRV_LIST;
│ │ │      *rp++ = n+1;
│ │ │      driver_output_term(port, result, result_n);
│ │ │      delete[] result;
│ │ │      delete d;
│ │ │  }</code></pre><p>This driver is called like the others from Erlang. However, as we use
│ │ │  <a href="../../../erts-17.0/doc/html/erl_driver.html#driver_output_term" title=""><code class="inline">driver_output_term</code></a>, there is no need to call <a href="erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a>. The Erlang code
│ │ │ -is in the sample file <code class="inline">next_perm.erl</code>.</p><p>The input is changed into a list of integers and sent to the driver.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4914684035-1">(</span><span class="ss">next_perm</span><span class="p" data-group-id="4914684035-1">)</span><span class="p">.</span><span class="w">
│ │ │ +is in the sample file <code class="inline">next_perm.erl</code>.</p><p>The input is changed into a list of integers and sent to the driver.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7731511405-1">(</span><span class="ss">next_perm</span><span class="p" data-group-id="7731511405-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4914684035-2">(</span><span class="p" data-group-id="4914684035-3">[</span><span class="ss">next_perm</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">prev_perm</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">load</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">all_perm</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4914684035-3">]</span><span class="p" data-group-id="4914684035-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7731511405-2">(</span><span class="p" data-group-id="7731511405-3">[</span><span class="ss">next_perm</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">prev_perm</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">load</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">all_perm</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7731511405-3">]</span><span class="p" data-group-id="7731511405-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">load</span><span class="p" data-group-id="4914684035-4">(</span><span class="p" data-group-id="4914684035-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="4914684035-5">(</span><span class="ss">next_perm</span><span class="p" data-group-id="4914684035-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">load</span><span class="p" data-group-id="7731511405-4">(</span><span class="p" data-group-id="7731511405-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="7731511405-5">(</span><span class="ss">next_perm</span><span class="p" data-group-id="7731511405-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="4914684035-6">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;next_perm&quot;</span><span class="p" data-group-id="4914684035-6">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +            </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="7731511405-6">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;next_perm&quot;</span><span class="p" data-group-id="7731511405-6">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │                  </span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -                </span><span class="p" data-group-id="4914684035-7">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="4914684035-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -                </span><span class="n">E</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="4914684035-8">(</span><span class="n">E</span><span class="p" data-group-id="4914684035-8">)</span><span class="w">
│ │ │ +                </span><span class="p" data-group-id="7731511405-7">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="7731511405-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ +                </span><span class="n">E</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="7731511405-8">(</span><span class="n">E</span><span class="p" data-group-id="7731511405-8">)</span><span class="w">
│ │ │              </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="4914684035-9">(</span><span class="p" data-group-id="4914684035-10">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;next_perm&quot;</span><span class="p" data-group-id="4914684035-10">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4914684035-11">[</span><span class="p" data-group-id="4914684035-11">]</span><span class="p" data-group-id="4914684035-9">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">register</span><span class="p" data-group-id="4914684035-12">(</span><span class="ss">next_perm</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p" data-group-id="4914684035-12">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="7731511405-9">(</span><span class="p" data-group-id="7731511405-10">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;next_perm&quot;</span><span class="p" data-group-id="7731511405-10">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7731511405-11">[</span><span class="p" data-group-id="7731511405-11">]</span><span class="p" data-group-id="7731511405-9">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">register</span><span class="p" data-group-id="7731511405-12">(</span><span class="ss">next_perm</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p" data-group-id="7731511405-12">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">ok</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">list_to_integer_binaries</span><span class="p" data-group-id="4914684035-13">(</span><span class="n">L</span><span class="p" data-group-id="4914684035-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4914684035-14">[</span><span class="p" data-group-id="4914684035-15">&lt;&lt;</span><span class="n">I</span><span class="p">:</span><span class="mi">32</span><span class="o">/</span><span class="ss">integer</span><span class="o">-</span><span class="ss">native</span><span class="p" data-group-id="4914684035-15">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">I</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4914684035-14">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">list_to_integer_binaries</span><span class="p" data-group-id="7731511405-13">(</span><span class="n">L</span><span class="p" data-group-id="7731511405-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7731511405-14">[</span><span class="p" data-group-id="7731511405-15">&lt;&lt;</span><span class="n">I</span><span class="p">:</span><span class="mi">32</span><span class="o">/</span><span class="ss">integer</span><span class="o">-</span><span class="ss">native</span><span class="p" data-group-id="7731511405-15">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">I</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="7731511405-14">]</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">next_perm</span><span class="p" data-group-id="4914684035-16">(</span><span class="n">L</span><span class="p" data-group-id="4914684035-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">next_perm</span><span class="p" data-group-id="4914684035-17">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="4914684035-17">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">next_perm</span><span class="p" data-group-id="7731511405-16">(</span><span class="n">L</span><span class="p" data-group-id="7731511405-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">next_perm</span><span class="p" data-group-id="7731511405-17">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="7731511405-17">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">prev_perm</span><span class="p" data-group-id="4914684035-18">(</span><span class="n">L</span><span class="p" data-group-id="4914684035-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">next_perm</span><span class="p" data-group-id="4914684035-19">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="4914684035-19">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">prev_perm</span><span class="p" data-group-id="7731511405-18">(</span><span class="n">L</span><span class="p" data-group-id="7731511405-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">next_perm</span><span class="p" data-group-id="7731511405-19">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="7731511405-19">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">next_perm</span><span class="p" data-group-id="4914684035-20">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Nxt</span><span class="p" data-group-id="4914684035-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">load</span><span class="p" data-group-id="4914684035-21">(</span><span class="p" data-group-id="4914684035-21">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">list_to_integer_binaries</span><span class="p" data-group-id="4914684035-22">(</span><span class="n">L</span><span class="p" data-group-id="4914684035-22">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">port_control</span><span class="p" data-group-id="4914684035-23">(</span><span class="ss">next_perm</span><span class="p">,</span><span class="w"> </span><span class="n">Nxt</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="4914684035-23">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">next_perm</span><span class="p" data-group-id="7731511405-20">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Nxt</span><span class="p" data-group-id="7731511405-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">load</span><span class="p" data-group-id="7731511405-21">(</span><span class="p" data-group-id="7731511405-21">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">list_to_integer_binaries</span><span class="p" data-group-id="7731511405-22">(</span><span class="n">L</span><span class="p" data-group-id="7731511405-22">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">port_control</span><span class="p" data-group-id="7731511405-23">(</span><span class="ss">next_perm</span><span class="p">,</span><span class="w"> </span><span class="n">Nxt</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="7731511405-23">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="n">Result</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="n">Result</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">all_perm</span><span class="p" data-group-id="4914684035-24">(</span><span class="n">L</span><span class="p" data-group-id="4914684035-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">New</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">prev_perm</span><span class="p" data-group-id="4914684035-25">(</span><span class="n">L</span><span class="p" data-group-id="4914684035-25">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">all_perm</span><span class="p" data-group-id="4914684035-26">(</span><span class="n">New</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4914684035-27">[</span><span class="n">New</span><span class="p" data-group-id="4914684035-27">]</span><span class="p" data-group-id="4914684035-26">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">all_perm</span><span class="p" data-group-id="7731511405-24">(</span><span class="n">L</span><span class="p" data-group-id="7731511405-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">New</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">prev_perm</span><span class="p" data-group-id="7731511405-25">(</span><span class="n">L</span><span class="p" data-group-id="7731511405-25">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">all_perm</span><span class="p" data-group-id="7731511405-26">(</span><span class="n">New</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7731511405-27">[</span><span class="n">New</span><span class="p" data-group-id="7731511405-27">]</span><span class="p" data-group-id="7731511405-26">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">all_perm</span><span class="p" data-group-id="4914684035-28">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="4914684035-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">all_perm</span><span class="p" data-group-id="7731511405-28">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="7731511405-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Acc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">all_perm</span><span class="p" data-group-id="4914684035-29">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Orig</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="4914684035-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">New</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">prev_perm</span><span class="p" data-group-id="4914684035-30">(</span><span class="n">L</span><span class="p" data-group-id="4914684035-30">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">all_perm</span><span class="p" data-group-id="4914684035-31">(</span><span class="n">New</span><span class="p">,</span><span class="w"> </span><span class="n">Orig</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4914684035-32">[</span><span class="n">New</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="4914684035-32">]</span><span class="p" data-group-id="4914684035-31">)</span><span class="p">.</span></code></pre>
│ │ │ +</span><span class="nf">all_perm</span><span class="p" data-group-id="7731511405-29">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Orig</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="7731511405-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">New</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">prev_perm</span><span class="p" data-group-id="7731511405-30">(</span><span class="n">L</span><span class="p" data-group-id="7731511405-30">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">all_perm</span><span class="p" data-group-id="7731511405-31">(</span><span class="n">New</span><span class="p">,</span><span class="w"> </span><span class="n">Orig</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7731511405-32">[</span><span class="n">New</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="7731511405-32">]</span><span class="p" data-group-id="7731511405-31">)</span><span class="p">.</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="tty.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-17.0/doc/html/erl_cmd.html
│ │ │ @@ -149,26 +149,26 @@
│ │ │  runtime system, more specifically to the <code class="inline">init</code> system process, see <a href="init.html"><code class="inline">init</code></a>.</p><p>The <code class="inline">init</code> process itself interprets some of these flags, the <em>init flags</em>. It
│ │ │  also stores any remaining flags, the <em>user flags</em>. The latter can be retrieved
│ │ │  by calling <a href="init.html#get_argument/1"><code class="inline">init:get_argument/1</code></a>.</p><p>A small number of &quot;-&quot; flags exist, which now actually are emulator flags, see
│ │ │  the description below.</p></li><li><p>Plain arguments are not interpreted in any way. They are also stored by the
│ │ │  <code class="inline">init</code> process and can be retrieved by calling <a href="init.html#get_plain_arguments/0"><code class="inline">init:get_plain_arguments/0</code></a>.
│ │ │  Plain arguments can occur before the first flag, or after a <code class="inline">--</code> flag. Also,
│ │ │  the <code class="inline">-extra</code> flag causes everything that follows to become plain arguments.</p></li></ul><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl +W w -sname arnie +S 2 -s my_init -extra +bertie</span><span class="w">
│ │ │ -</span><span class="gp unselectable">(arnie@host)1&gt; </span><span class="nc">init</span><span class="p">:</span><span class="nf">get_argument</span><span class="p" data-group-id="8395293181-1">(</span><span class="ss">sname</span><span class="p" data-group-id="8395293181-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8395293181-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="8395293181-3">[</span><span class="p" data-group-id="8395293181-4">[</span><span class="s">&quot;arnie&quot;</span><span class="p" data-group-id="8395293181-4">]</span><span class="p" data-group-id="8395293181-3">]</span><span class="p" data-group-id="8395293181-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">(arnie@host)2&gt; </span><span class="nc">init</span><span class="p">:</span><span class="nf">get_plain_arguments</span><span class="p" data-group-id="8395293181-5">(</span><span class="p" data-group-id="8395293181-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8395293181-6">[</span><span class="s">&quot;+bertie&quot;</span><span class="p" data-group-id="8395293181-6">]</span></code></pre><p>Here <code class="inline">+W w</code> and <code class="inline">+S 2</code> are emulator flags. <code class="inline">-s my_init</code> is an init flag,
│ │ │ +</span><span class="gp unselectable">(arnie@host)1&gt; </span><span class="nc">init</span><span class="p">:</span><span class="nf">get_argument</span><span class="p" data-group-id="2844944249-1">(</span><span class="ss">sname</span><span class="p" data-group-id="2844944249-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2844944249-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="2844944249-3">[</span><span class="p" data-group-id="2844944249-4">[</span><span class="s">&quot;arnie&quot;</span><span class="p" data-group-id="2844944249-4">]</span><span class="p" data-group-id="2844944249-3">]</span><span class="p" data-group-id="2844944249-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">(arnie@host)2&gt; </span><span class="nc">init</span><span class="p">:</span><span class="nf">get_plain_arguments</span><span class="p" data-group-id="2844944249-5">(</span><span class="p" data-group-id="2844944249-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2844944249-6">[</span><span class="s">&quot;+bertie&quot;</span><span class="p" data-group-id="2844944249-6">]</span></code></pre><p>Here <code class="inline">+W w</code> and <code class="inline">+S 2</code> are emulator flags. <code class="inline">-s my_init</code> is an init flag,
│ │ │  interpreted by <code class="inline">init</code>. <code class="inline">-sname arnie</code> is a user flag, stored by <code class="inline">init</code>. It is
│ │ │  read by Kernel and causes the Erlang runtime system to become distributed.
│ │ │  Finally, everything after <code class="inline">-extra</code> (that is, <code class="inline">+bertie</code>) is considered as plain
│ │ │  arguments.</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -myflag 1</span><span class="w">
│ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nc">init</span><span class="p">:</span><span class="nf">get_argument</span><span class="p" data-group-id="2701616215-1">(</span><span class="ss">myflag</span><span class="p" data-group-id="2701616215-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2701616215-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="2701616215-3">[</span><span class="p" data-group-id="2701616215-4">[</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="2701616215-4">]</span><span class="p" data-group-id="2701616215-3">]</span><span class="p" data-group-id="2701616215-2">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">init</span><span class="p">:</span><span class="nf">get_plain_arguments</span><span class="p" data-group-id="2701616215-5">(</span><span class="p" data-group-id="2701616215-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2701616215-6">[</span><span class="p" data-group-id="2701616215-6">]</span></code></pre><p>Here the user flag <code class="inline">-myflag 1</code> is passed to and stored by the <code class="inline">init</code> process. It
│ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nc">init</span><span class="p">:</span><span class="nf">get_argument</span><span class="p" data-group-id="0535195248-1">(</span><span class="ss">myflag</span><span class="p" data-group-id="0535195248-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0535195248-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="0535195248-3">[</span><span class="p" data-group-id="0535195248-4">[</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="0535195248-4">]</span><span class="p" data-group-id="0535195248-3">]</span><span class="p" data-group-id="0535195248-2">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">init</span><span class="p">:</span><span class="nf">get_plain_arguments</span><span class="p" data-group-id="0535195248-5">(</span><span class="p" data-group-id="0535195248-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0535195248-6">[</span><span class="p" data-group-id="0535195248-6">]</span></code></pre><p>Here the user flag <code class="inline">-myflag 1</code> is passed to and stored by the <code class="inline">init</code> process. It
│ │ │  is a user-defined flag, presumably used by some user-defined application.</p><h2 id="flags" class="section-heading">
│ │ │    <a href="#flags" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Flags</span>
│ │ │  </h2>
│ │ │  <p>In the following list, init flags are marked &quot;(init flag)&quot;. Unless otherwise
│ │ │ @@ -698,15 +698,15 @@
│ │ │  processes) into a smaller set of schedulers when schedulers frequently run
│ │ │  out of work. When disabled, the frequency with which schedulers run out of
│ │ │  work is not taken into account by the load balancing logic.</p><p><code class="inline">+scl false</code> is similar to <a href="#%2Bsub"><code class="inline">+sub true</code></a>, but <code class="inline">+sub true</code>
│ │ │  also balances scheduler utilization between schedulers.</p></li><li><p><strong><code class="inline" id="+sct">+sct CpuTopology</code></strong> - Sets a user-defined CPU topology.
│ │ │  The user-defined CPU topology overrides
│ │ │  any automatically detected CPU topology. The CPU topology is used when
│ │ │  <a href="#%2Bsbt">binding schedulers to logical processors</a>. This option must be before
│ │ │ -<a href="#%2Bsbt"><code class="inline">+sbt</code></a> on the command-line.</p><pre><code class="makeup erlang" translate="no"><span class="o">&lt;</span><span class="n">Id</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="9546125264-1">(</span><span class="p" data-group-id="9546125264-1">)</span><span class="p">;</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="o">&lt;</span><span class="n">Id</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mi">65535</span><span class="w">
│ │ │ +<a href="#%2Bsbt"><code class="inline">+sbt</code></a> on the command-line.</p><pre><code class="makeup erlang" translate="no"><span class="o">&lt;</span><span class="n">Id</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="6740506564-1">(</span><span class="p" data-group-id="6740506564-1">)</span><span class="p">;</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="o">&lt;</span><span class="n">Id</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mi">65535</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="n">IdRange</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&lt;</span><span class="n">Id</span><span class="o">&gt;</span><span class="o">-</span><span class="o">&lt;</span><span class="n">Id</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="n">IdOrIdRange</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&lt;</span><span class="n">Id</span><span class="o">&gt;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="o">&lt;</span><span class="n">IdRange</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="n">IdList</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&lt;</span><span class="n">IdOrIdRange</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="n">IdOrIdRange</span><span class="o">&gt;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="o">&lt;</span><span class="n">IdOrIdRange</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="n">LogicalIds</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L</span><span class="o">&lt;</span><span class="n">IdList</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="n">ThreadIds</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">T</span><span class="o">&lt;</span><span class="n">IdList</span><span class="o">&gt;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">t</span><span class="o">&lt;</span><span class="n">IdList</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="n">CoreIds</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">C</span><span class="o">&lt;</span><span class="n">IdList</span><span class="o">&gt;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">c</span><span class="o">&lt;</span><span class="n">IdList</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="n">ProcessorIds</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">&lt;</span><span class="n">IdList</span><span class="o">&gt;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">p</span><span class="o">&lt;</span><span class="n">IdList</span><span class="o">&gt;</span><span class="w">
│ │ │ @@ -731,30 +731,30 @@
│ │ │  node.</li><li><code class="inline">&lt;LogicalIds&gt;&lt;ThreadIds&gt;&lt;CoreIds&gt;&lt;NodeIds&gt;&lt;ProcessorIds&gt;</code>, that is, thread
│ │ │  is part of a core that is part of a NUMA node, which is part of a
│ │ │  processor.</li></ul><p>A CPU topology can consist of both processor external, and processor
│ │ │  internal NUMA nodes as long as each logical processor belongs to only one
│ │ │  NUMA node. If <code class="inline">&lt;ProcessorIds&gt;</code> is omitted, its default position is before
│ │ │  <code class="inline">&lt;NodeIds&gt;</code>. That is, the default is processor external NUMA nodes.</p><p>If a list of identifiers is used in an <code class="inline">&lt;IdDefs&gt;</code>:</p><ul><li><code class="inline">&lt;LogicalIds&gt;</code> must be a list of identifiers.</li><li>At least one other identifier type besides <code class="inline">&lt;LogicalIds&gt;</code> must also have a
│ │ │  list of identifiers.</li><li>All lists of identifiers must produce the same number of identifiers.</li></ul><p>A simple example. A single quad core processor can be described as follows:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl +sct L0-3c0-3</span><span class="w">
│ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="4780267584-1">(</span><span class="ss">cpu_topology</span><span class="p" data-group-id="4780267584-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4780267584-2">[</span><span class="p" data-group-id="4780267584-3">{</span><span class="ss">processor</span><span class="p">,</span><span class="p" data-group-id="4780267584-4">[</span><span class="p" data-group-id="4780267584-5">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="4780267584-6">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="4780267584-6">}</span><span class="p" data-group-id="4780267584-5">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="4780267584-7">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="4780267584-8">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4780267584-8">}</span><span class="p" data-group-id="4780267584-7">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="4780267584-9">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="4780267584-10">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4780267584-10">}</span><span class="p" data-group-id="4780267584-9">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="4780267584-11">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="4780267584-12">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4780267584-12">}</span><span class="p" data-group-id="4780267584-11">}</span><span class="p" data-group-id="4780267584-4">]</span><span class="p" data-group-id="4780267584-3">}</span><span class="p" data-group-id="4780267584-2">]</span></code></pre><p>A more complicated example with two quad core processors, each processor in
│ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="2185878318-1">(</span><span class="ss">cpu_topology</span><span class="p" data-group-id="2185878318-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2185878318-2">[</span><span class="p" data-group-id="2185878318-3">{</span><span class="ss">processor</span><span class="p">,</span><span class="p" data-group-id="2185878318-4">[</span><span class="p" data-group-id="2185878318-5">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="2185878318-6">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="2185878318-6">}</span><span class="p" data-group-id="2185878318-5">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="2185878318-7">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="2185878318-8">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2185878318-8">}</span><span class="p" data-group-id="2185878318-7">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="2185878318-9">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="2185878318-10">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2185878318-10">}</span><span class="p" data-group-id="2185878318-9">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="2185878318-11">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="2185878318-12">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2185878318-12">}</span><span class="p" data-group-id="2185878318-11">}</span><span class="p" data-group-id="2185878318-4">]</span><span class="p" data-group-id="2185878318-3">}</span><span class="p" data-group-id="2185878318-2">]</span></code></pre><p>A more complicated example with two quad core processors, each processor in
│ │ │  its own NUMA node. The ordering of logical processors is a bit weird. This
│ │ │  to give a better example of identifier lists:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl +sct L0-1,3-2c0-3p0N0:L7,4,6-5c0-3p1N1</span><span class="w">
│ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="0473851476-1">(</span><span class="ss">cpu_topology</span><span class="p" data-group-id="0473851476-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0473851476-2">[</span><span class="p" data-group-id="0473851476-3">{</span><span class="nb">node</span><span class="p">,</span><span class="p" data-group-id="0473851476-4">[</span><span class="p" data-group-id="0473851476-5">{</span><span class="ss">processor</span><span class="p">,</span><span class="p" data-group-id="0473851476-6">[</span><span class="p" data-group-id="0473851476-7">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="0473851476-8">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="0473851476-8">}</span><span class="p" data-group-id="0473851476-7">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="0473851476-9">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="0473851476-10">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0473851476-10">}</span><span class="p" data-group-id="0473851476-9">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="0473851476-11">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="0473851476-12">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0473851476-12">}</span><span class="p" data-group-id="0473851476-11">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="0473851476-13">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="0473851476-14">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0473851476-14">}</span><span class="p" data-group-id="0473851476-13">}</span><span class="p" data-group-id="0473851476-6">]</span><span class="p" data-group-id="0473851476-5">}</span><span class="p" data-group-id="0473851476-4">]</span><span class="p" data-group-id="0473851476-3">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0473851476-15">{</span><span class="nb">node</span><span class="p">,</span><span class="p" data-group-id="0473851476-16">[</span><span class="p" data-group-id="0473851476-17">{</span><span class="ss">processor</span><span class="p">,</span><span class="p" data-group-id="0473851476-18">[</span><span class="p" data-group-id="0473851476-19">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="0473851476-20">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="0473851476-20">}</span><span class="p" data-group-id="0473851476-19">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="0473851476-21">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="0473851476-22">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0473851476-22">}</span><span class="p" data-group-id="0473851476-21">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="0473851476-23">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="0473851476-24">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="0473851476-24">}</span><span class="p" data-group-id="0473851476-23">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="0473851476-25">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="0473851476-26">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0473851476-26">}</span><span class="p" data-group-id="0473851476-25">}</span><span class="p" data-group-id="0473851476-18">]</span><span class="p" data-group-id="0473851476-17">}</span><span class="p" data-group-id="0473851476-16">]</span><span class="p" data-group-id="0473851476-15">}</span><span class="p" data-group-id="0473851476-2">]</span></code></pre><p>As long as real identifiers are correct, it is OK to pass a CPU topology
│ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="4693432597-1">(</span><span class="ss">cpu_topology</span><span class="p" data-group-id="4693432597-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4693432597-2">[</span><span class="p" data-group-id="4693432597-3">{</span><span class="nb">node</span><span class="p">,</span><span class="p" data-group-id="4693432597-4">[</span><span class="p" data-group-id="4693432597-5">{</span><span class="ss">processor</span><span class="p">,</span><span class="p" data-group-id="4693432597-6">[</span><span class="p" data-group-id="4693432597-7">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="4693432597-8">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="4693432597-8">}</span><span class="p" data-group-id="4693432597-7">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="4693432597-9">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="4693432597-10">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4693432597-10">}</span><span class="p" data-group-id="4693432597-9">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="4693432597-11">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="4693432597-12">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4693432597-12">}</span><span class="p" data-group-id="4693432597-11">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="4693432597-13">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="4693432597-14">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4693432597-14">}</span><span class="p" data-group-id="4693432597-13">}</span><span class="p" data-group-id="4693432597-6">]</span><span class="p" data-group-id="4693432597-5">}</span><span class="p" data-group-id="4693432597-4">]</span><span class="p" data-group-id="4693432597-3">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4693432597-15">{</span><span class="nb">node</span><span class="p">,</span><span class="p" data-group-id="4693432597-16">[</span><span class="p" data-group-id="4693432597-17">{</span><span class="ss">processor</span><span class="p">,</span><span class="p" data-group-id="4693432597-18">[</span><span class="p" data-group-id="4693432597-19">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="4693432597-20">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="4693432597-20">}</span><span class="p" data-group-id="4693432597-19">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="4693432597-21">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="4693432597-22">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4693432597-22">}</span><span class="p" data-group-id="4693432597-21">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="4693432597-23">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="4693432597-24">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="4693432597-24">}</span><span class="p" data-group-id="4693432597-23">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="4693432597-25">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="4693432597-26">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="4693432597-26">}</span><span class="p" data-group-id="4693432597-25">}</span><span class="p" data-group-id="4693432597-18">]</span><span class="p" data-group-id="4693432597-17">}</span><span class="p" data-group-id="4693432597-16">]</span><span class="p" data-group-id="4693432597-15">}</span><span class="p" data-group-id="4693432597-2">]</span></code></pre><p>As long as real identifiers are correct, it is OK to pass a CPU topology
│ │ │  that is not a correct description of the CPU topology. When used with care
│ │ │  this can be very useful. This to trick the emulator to bind its schedulers
│ │ │  as you want. For example, if you want to run multiple Erlang runtime systems
│ │ │  on the same machine, you want to reduce the number of schedulers used and
│ │ │  manipulate the CPU topology so that they bind to different logical CPUs. An
│ │ │  example, with two Erlang runtime systems on a quad core machine:</p><pre><code class="text">% erl +sct L0-3c0-3 +sbt db +S3:2 -detached -noinput -noshell -sname one
│ │ │  % erl +sct L3-0c0-3 +sbt db +S3:2 -detached -noinput -noshell -sname two</code></pre><p>In this example, each runtime system have two schedulers each online, and
│ │ │ @@ -923,18 +923,18 @@
│ │ │  </h2>
│ │ │  <p>The standard Erlang/OTP system can be reconfigured to change the default
│ │ │  behavior on startup.</p><ul><li><p><strong>The <code class="inline">.erlang</code> startup file</strong> - When Erlang/OTP is started, the system
│ │ │  searches for a file named <code class="inline">.erlang</code> in the
│ │ │  <a href="init.html#home">user's home directory</a> and then
│ │ │  <a href="../../../lib/stdlib-8.0/doc/html/filename.html#user_config"><code class="inline">filename:basedir(user_config, &quot;erlang&quot;)</code></a>.</p><p>If an <code class="inline">.erlang</code> file is found, it is assumed to contain valid Erlang
│ │ │  expressions. These expressions are evaluated as if they were input to the
│ │ │ -shell.</p><p>A typical <code class="inline">.erlang</code> file contains a set of search paths, for example:</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9405900326-1">(</span><span class="s">&quot;executing user profile in $HOME/.erlang\n&quot;</span><span class="p">,</span><span class="p" data-group-id="9405900326-2">[</span><span class="p" data-group-id="9405900326-2">]</span><span class="p" data-group-id="9405900326-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nc">code</span><span class="p">:</span><span class="nf">add_path</span><span class="p" data-group-id="9405900326-3">(</span><span class="s">&quot;/home/calvin/test/ebin&quot;</span><span class="p" data-group-id="9405900326-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nc">code</span><span class="p">:</span><span class="nf">add_path</span><span class="p" data-group-id="9405900326-4">(</span><span class="s">&quot;/home/hobbes/bigappl-1.2/ebin&quot;</span><span class="p" data-group-id="9405900326-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9405900326-5">(</span><span class="s">&quot;.erlang rc finished\n&quot;</span><span class="p">,</span><span class="p" data-group-id="9405900326-6">[</span><span class="p" data-group-id="9405900326-6">]</span><span class="p" data-group-id="9405900326-5">)</span><span class="p">.</span></code></pre></li><li><p><strong>user_default</strong> and <strong>shell_default</strong> - Functions in the shell that are not
│ │ │ +shell.</p><p>A typical <code class="inline">.erlang</code> file contains a set of search paths, for example:</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4138461316-1">(</span><span class="s">&quot;executing user profile in $HOME/.erlang\n&quot;</span><span class="p">,</span><span class="p" data-group-id="4138461316-2">[</span><span class="p" data-group-id="4138461316-2">]</span><span class="p" data-group-id="4138461316-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nc">code</span><span class="p">:</span><span class="nf">add_path</span><span class="p" data-group-id="4138461316-3">(</span><span class="s">&quot;/home/calvin/test/ebin&quot;</span><span class="p" data-group-id="4138461316-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nc">code</span><span class="p">:</span><span class="nf">add_path</span><span class="p" data-group-id="4138461316-4">(</span><span class="s">&quot;/home/hobbes/bigappl-1.2/ebin&quot;</span><span class="p" data-group-id="4138461316-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4138461316-5">(</span><span class="s">&quot;.erlang rc finished\n&quot;</span><span class="p">,</span><span class="p" data-group-id="4138461316-6">[</span><span class="p" data-group-id="4138461316-6">]</span><span class="p" data-group-id="4138461316-5">)</span><span class="p">.</span></code></pre></li><li><p><strong>user_default</strong> and <strong>shell_default</strong> - Functions in the shell that are not
│ │ │  prefixed by a module name are assumed to be functional objects (funs),
│ │ │  built-in functions (BIFs), or belong to the module <code class="inline">user_default</code> or
│ │ │  <code class="inline">shell_default</code>.</p><p>To include private shell commands, define them in a module <code class="inline">user_default</code> and
│ │ │  add the following argument as the first line in the <code class="inline">.erlang</code> file:</p><pre><code class="text">code:load_abs(&quot;..../user_default&quot;).</code></pre></li><li><p><strong>erl</strong> - If the contents of <code class="inline">.erlang</code> are changed and a private version of
│ │ │  <code class="inline">user_default</code> is defined, the Erlang/OTP environment can be customized. More
│ │ │  powerful changes can be made by supplying command-line arguments in the
│ │ │  startup script <code class="inline">erl</code>. For more information, see <a href="init.html"><code class="inline">init</code></a>.</p></li></ul><h2 id="see-also" class="section-heading">
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-17.0/doc/html/erl_dist_protocol.html
│ │ │ @@ -252,32 +252,32 @@
│ │ │  ---
│ │ │  sequenceDiagram
│ │ │      participant client as Client (or Node)
│ │ │      participant EPMD
│ │ │      
│ │ │      client -&gt;&gt; EPMD: EPMD_NAMES_REQ
│ │ │      EPMD --&gt;&gt; client: NAMES_RESP</code></pre><table><thead><tr><th style="text-align: left;">1</th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">110</code></td></tr></tbody></table><p><em>Table: EPMD_NAMES_REQ (110)</em></p><p>The response for a <code class="inline">EPMD_NAMES_REQ</code> is as follows:</p><table><thead><tr><th style="text-align: left;">4</th><th style="text-align: left;"></th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">EPMDPortNo</code></td><td style="text-align: left;"><code class="inline">NodeInfo*</code></td></tr></tbody></table><p><em>Table: NAMES_RESP</em></p><p><code class="inline">NodeInfo</code> is a string written for each active node. When all <code class="inline">NodeInfo</code> has
│ │ │ -been written the connection is closed by the EPMD.</p><p><code class="inline">NodeInfo</code> is, as expressed in Erlang:</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6157048788-1">(</span><span class="s">&quot;name ~ts at port </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6157048788-2">[</span><span class="n">NodeName</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p" data-group-id="6157048788-2">]</span><span class="p" data-group-id="6157048788-1">)</span><span class="p">.</span></code></pre><h3 id="dump-all-data-from-epmd" class="section-heading">
│ │ │ +been written the connection is closed by the EPMD.</p><p><code class="inline">NodeInfo</code> is, as expressed in Erlang:</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0997403354-1">(</span><span class="s">&quot;name ~ts at port </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0997403354-2">[</span><span class="n">NodeName</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p" data-group-id="0997403354-2">]</span><span class="p" data-group-id="0997403354-1">)</span><span class="p">.</span></code></pre><h3 id="dump-all-data-from-epmd" class="section-heading">
│ │ │    <a href="#dump-all-data-from-epmd" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Dump All Data from EPMD</span>
│ │ │  </h3>
│ │ │  <p>This request is not really used, it is to be regarded as a debug feature.</p><pre><code class="mermaid">---
│ │ │  title: Dump All Data from EPMD
│ │ │  ---
│ │ │  sequenceDiagram
│ │ │      participant client as Client (or Node)
│ │ │      participant EPMD
│ │ │      
│ │ │      client -&gt;&gt; EPMD: EPMD_DUMP_REQ
│ │ │      EPMD --&gt;&gt; client: DUMP_RESP</code></pre><table><thead><tr><th style="text-align: left;">1</th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">100</code></td></tr></tbody></table><p><em>Table: EPMD_DUMP_REQ</em></p><p>The response for a <code class="inline">EPMD_DUMP_REQ</code> is as follows:</p><table><thead><tr><th style="text-align: left;">4</th><th style="text-align: left;"></th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">EPMDPortNo</code></td><td style="text-align: left;"><code class="inline">NodeInfo*</code></td></tr></tbody></table><p><em>Table: DUMP_RESP</em></p><p><code class="inline">NodeInfo</code> is a string written for each node kept in the EPMD. When all
│ │ │ -<code class="inline">NodeInfo</code> has been written the connection is closed by the EPMD.</p><p><code class="inline">NodeInfo</code> is, as expressed in Erlang:</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8276406014-1">(</span><span class="s">&quot;active name     ~ts at port </span><span class="si">~p</span><span class="s">, fd = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="p" data-group-id="8276406014-2">[</span><span class="n">NodeName</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="8276406014-2">]</span><span class="p" data-group-id="8276406014-1">)</span><span class="p">.</span></code></pre><p>or</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1846516253-1">(</span><span class="s">&quot;old/unused name ~ts at port </span><span class="si">~p</span><span class="s">, fd = </span><span class="si">~p</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="p" data-group-id="1846516253-2">[</span><span class="n">NodeName</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="1846516253-2">]</span><span class="p" data-group-id="1846516253-1">)</span><span class="p">.</span></code></pre><h3 id="kill-epmd" class="section-heading">
│ │ │ +<code class="inline">NodeInfo</code> has been written the connection is closed by the EPMD.</p><p><code class="inline">NodeInfo</code> is, as expressed in Erlang:</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4445499821-1">(</span><span class="s">&quot;active name     ~ts at port </span><span class="si">~p</span><span class="s">, fd = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +          </span><span class="p" data-group-id="4445499821-2">[</span><span class="n">NodeName</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="4445499821-2">]</span><span class="p" data-group-id="4445499821-1">)</span><span class="p">.</span></code></pre><p>or</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7826016709-1">(</span><span class="s">&quot;old/unused name ~ts at port </span><span class="si">~p</span><span class="s">, fd = </span><span class="si">~p</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +          </span><span class="p" data-group-id="7826016709-2">[</span><span class="n">NodeName</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7826016709-2">]</span><span class="p" data-group-id="7826016709-1">)</span><span class="p">.</span></code></pre><h3 id="kill-epmd" class="section-heading">
│ │ │    <a href="#kill-epmd" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Kill EPMD</span>
│ │ │  </h3>
│ │ │  <p>This request kills the running EPMD. It is almost never used.</p><pre><code class="mermaid">---
│ │ │  title: Kill EPMD
│ │ │ @@ -407,54 +407,54 @@
│ │ │  received from <code class="inline">A</code> is correct and generates a digest from the challenge
│ │ │  received from <code class="inline">A</code>. The digest is then sent to <code class="inline">A</code>. The message is as follows:</p><table><thead><tr><th style="text-align: left;">1</th><th style="text-align: left;">16</th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">'a'</code></td><td style="text-align: left;"><code class="inline">Digest</code></td></tr></tbody></table><p><em>Table: The challenge_ack message</em></p><p><code class="inline">Digest</code> is the digest calculated by <code class="inline">B</code> for <code class="inline">A</code>'s challenge.</p></li><li><p><strong>7) check</strong> - <code class="inline">A</code> checks the digest from <code class="inline">B</code> and the connection is up.</p></li></ul><h3 id="semigraphic-view" class="section-heading">
│ │ │    <a href="#semigraphic-view" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Semigraphic View</span>
│ │ │  </h3>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="n">A</span><span class="w"> </span><span class="p" data-group-id="9818038428-1">(</span><span class="ss">initiator</span><span class="p" data-group-id="9818038428-1">)</span><span class="w">                                      </span><span class="n">B</span><span class="w"> </span><span class="p" data-group-id="9818038428-2">(</span><span class="ss">acceptor</span><span class="p" data-group-id="9818038428-2">)</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="n">A</span><span class="w"> </span><span class="p" data-group-id="4157727238-1">(</span><span class="ss">initiator</span><span class="p" data-group-id="4157727238-1">)</span><span class="w">                                      </span><span class="n">B</span><span class="w"> </span><span class="p" data-group-id="4157727238-2">(</span><span class="ss">acceptor</span><span class="p" data-group-id="4157727238-2">)</span><span class="w">
│ │ │  
│ │ │  </span><span class="n">TCP</span><span class="w"> </span><span class="ss">connect</span><span class="w"> </span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">&gt;</span><span class="w">
│ │ │                                                     </span><span class="n">TCP</span><span class="w"> </span><span class="ss">accept</span><span class="w">
│ │ │  
│ │ │  </span><span class="ss">send_name</span><span class="w"> </span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">&gt;</span><span class="w">
│ │ │                                                     </span><span class="ss">recv_name</span><span class="w">
│ │ │  
│ │ │    </span><span class="o">&lt;-</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">-</span><span class="w"> </span><span class="ss">send_status</span><span class="w">
│ │ │  </span><span class="nf">recv_status</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9818038428-3">(</span><span class="k">if</span><span class="w"> </span><span class="ss">status</span><span class="w"> </span><span class="ss">was</span><span class="w"> </span><span class="ss">&#39;alive&#39;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4157727238-3">(</span><span class="k">if</span><span class="w"> </span><span class="ss">status</span><span class="w"> </span><span class="ss">was</span><span class="w"> </span><span class="ss">&#39;alive&#39;</span><span class="w">
│ │ │   </span><span class="ss">send_status</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                                                   </span><span class="ss">recv_status</span><span class="p" data-group-id="9818038428-3">)</span><span class="w">
│ │ │ +                                                   </span><span class="ss">recv_status</span><span class="p" data-group-id="4157727238-3">)</span><span class="w">
│ │ │  
│ │ │ -                          </span><span class="p" data-group-id="9818038428-4">(</span><span class="n">ChB</span><span class="p" data-group-id="9818038428-4">)</span><span class="w">                      </span><span class="n">ChB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">gen_challenge</span><span class="p" data-group-id="9818038428-5">(</span><span class="p" data-group-id="9818038428-5">)</span><span class="w">
│ │ │ +                          </span><span class="p" data-group-id="4157727238-4">(</span><span class="n">ChB</span><span class="p" data-group-id="4157727238-4">)</span><span class="w">                      </span><span class="n">ChB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">gen_challenge</span><span class="p" data-group-id="4157727238-5">(</span><span class="p" data-group-id="4157727238-5">)</span><span class="w">
│ │ │    </span><span class="o">&lt;-</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">-</span><span class="w"> </span><span class="ss">send_challenge</span><span class="w">
│ │ │  </span><span class="nf">recv_challenge</span><span class="w">
│ │ │  
│ │ │ -</span><span class="p" data-group-id="9818038428-6">(</span><span class="k">if</span><span class="w"> </span><span class="ss">old</span><span class="w"> </span><span class="ss">send_name</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4157727238-6">(</span><span class="k">if</span><span class="w"> </span><span class="ss">old</span><span class="w"> </span><span class="ss">send_name</span><span class="w">
│ │ │   </span><span class="ss">send_complement</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                                                   </span><span class="ss">recv_complement</span><span class="p" data-group-id="9818038428-6">)</span><span class="w">
│ │ │ +                                                   </span><span class="ss">recv_complement</span><span class="p" data-group-id="4157727238-6">)</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">ChA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">gen_challenge</span><span class="p" data-group-id="9818038428-7">(</span><span class="p" data-group-id="9818038428-7">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">OCA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">out_cookie</span><span class="p" data-group-id="9818038428-8">(</span><span class="n">B</span><span class="p" data-group-id="9818038428-8">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">DiA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">gen_digest</span><span class="p" data-group-id="9818038428-9">(</span><span class="n">ChB</span><span class="p">,</span><span class="w"> </span><span class="n">OCA</span><span class="p" data-group-id="9818038428-9">)</span><span class="w">
│ │ │ -                          </span><span class="p" data-group-id="9818038428-10">(</span><span class="n">ChA</span><span class="p">,</span><span class="w"> </span><span class="n">DiA</span><span class="p" data-group-id="9818038428-10">)</span><span class="w">
│ │ │ +</span><span class="n">ChA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">gen_challenge</span><span class="p" data-group-id="4157727238-7">(</span><span class="p" data-group-id="4157727238-7">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">OCA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">out_cookie</span><span class="p" data-group-id="4157727238-8">(</span><span class="n">B</span><span class="p" data-group-id="4157727238-8">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">DiA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">gen_digest</span><span class="p" data-group-id="4157727238-9">(</span><span class="n">ChB</span><span class="p">,</span><span class="w"> </span><span class="n">OCA</span><span class="p" data-group-id="4157727238-9">)</span><span class="w">
│ │ │ +                          </span><span class="p" data-group-id="4157727238-10">(</span><span class="n">ChA</span><span class="p">,</span><span class="w"> </span><span class="n">DiA</span><span class="p" data-group-id="4157727238-10">)</span><span class="w">
│ │ │  </span><span class="ss">send_challenge_reply</span><span class="w"> </span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="p">-&gt;</span><span class="w">
│ │ │                                                     </span><span class="ss">recv_challenge_reply</span><span class="w">
│ │ │ -                                                   </span><span class="n">ICB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">in_cookie</span><span class="p" data-group-id="9818038428-11">(</span><span class="n">A</span><span class="p" data-group-id="9818038428-11">)</span><span class="p">,</span><span class="w">
│ │ │ +                                                   </span><span class="n">ICB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">in_cookie</span><span class="p" data-group-id="4157727238-11">(</span><span class="n">A</span><span class="p" data-group-id="4157727238-11">)</span><span class="p">,</span><span class="w">
│ │ │                                                     </span><span class="nc">check</span><span class="p">:</span><span class="w">
│ │ │ -                                                   </span><span class="n">DiA</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="nf">gen_digest</span><span class="w"> </span><span class="p" data-group-id="9818038428-12">(</span><span class="n">ChB</span><span class="p">,</span><span class="w"> </span><span class="n">ICB</span><span class="p" data-group-id="9818038428-12">)</span><span class="o">?</span><span class="w">
│ │ │ +                                                   </span><span class="n">DiA</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="nf">gen_digest</span><span class="w"> </span><span class="p" data-group-id="4157727238-12">(</span><span class="n">ChB</span><span class="p">,</span><span class="w"> </span><span class="n">ICB</span><span class="p" data-group-id="4157727238-12">)</span><span class="o">?</span><span class="w">
│ │ │  </span><span class="w">                                                   </span><span class="p">-</span><span class="w"> </span><span class="na">if</span><span class="w"> </span><span class="n">OK</span><span class="p">:</span><span class="w">
│ │ │ -                                                    </span><span class="n">OCB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">out_cookie</span><span class="p" data-group-id="9818038428-13">(</span><span class="n">A</span><span class="p" data-group-id="9818038428-13">)</span><span class="p">,</span><span class="w">
│ │ │ -                                                    </span><span class="n">DiB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">gen_digest</span><span class="w"> </span><span class="p" data-group-id="9818038428-14">(</span><span class="n">ChA</span><span class="p">,</span><span class="w"> </span><span class="n">OCB</span><span class="p" data-group-id="9818038428-14">)</span><span class="w">
│ │ │ -                          </span><span class="p" data-group-id="9818038428-15">(</span><span class="n">DiB</span><span class="p" data-group-id="9818038428-15">)</span><span class="w">
│ │ │ +                                                    </span><span class="n">OCB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">out_cookie</span><span class="p" data-group-id="4157727238-13">(</span><span class="n">A</span><span class="p" data-group-id="4157727238-13">)</span><span class="p">,</span><span class="w">
│ │ │ +                                                    </span><span class="n">DiB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">gen_digest</span><span class="w"> </span><span class="p" data-group-id="4157727238-14">(</span><span class="n">ChA</span><span class="p">,</span><span class="w"> </span><span class="n">OCB</span><span class="p" data-group-id="4157727238-14">)</span><span class="w">
│ │ │ +                          </span><span class="p" data-group-id="4157727238-15">(</span><span class="n">DiB</span><span class="p" data-group-id="4157727238-15">)</span><span class="w">
│ │ │    </span><span class="o">&lt;-</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="w"> </span><span class="ss">send_challenge_ack</span><span class="w">
│ │ │  </span><span class="ss">recv_challenge_ack</span><span class="w">                                  </span><span class="n">DONE</span><span class="w">
│ │ │ -</span><span class="n">ICA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">in_cookie</span><span class="p" data-group-id="9818038428-16">(</span><span class="n">B</span><span class="p" data-group-id="9818038428-16">)</span><span class="p">,</span><span class="w">                                </span><span class="o">-</span><span class="w"> </span><span class="nc">else</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="n">ICA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">in_cookie</span><span class="p" data-group-id="4157727238-16">(</span><span class="n">B</span><span class="p" data-group-id="4157727238-16">)</span><span class="p">,</span><span class="w">                                </span><span class="o">-</span><span class="w"> </span><span class="nc">else</span><span class="p">:</span><span class="w">
│ │ │  </span><span class="nc">check</span><span class="p">:</span><span class="w">                                              </span><span class="n">CLOSE</span><span class="w">
│ │ │ -</span><span class="n">DiB</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="nf">gen_digest</span><span class="p" data-group-id="9818038428-17">(</span><span class="n">ChA</span><span class="p">,</span><span class="w"> </span><span class="n">ICA</span><span class="p" data-group-id="9818038428-17">)</span><span class="o">?</span><span class="w">
│ │ │ +</span><span class="n">DiB</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="nf">gen_digest</span><span class="p" data-group-id="4157727238-17">(</span><span class="n">ChA</span><span class="p">,</span><span class="w"> </span><span class="n">ICA</span><span class="p" data-group-id="4157727238-17">)</span><span class="o">?</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="w"> </span><span class="na">if</span><span class="w"> </span><span class="n">OK</span><span class="p">:</span><span class="w">
│ │ │   </span><span class="n">DONE</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="w"> </span><span class="na">else</span><span class="p">:</span><span class="w">
│ │ │   </span><span class="n">CLOSE</span></code></pre><p><a href="" id="dflags"></a></p><h3 id="distribution-flags" class="section-heading">
│ │ │    <a href="#distribution-flags" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-17.0/doc/html/erl_ext_dist.html
│ │ │ @@ -434,15 +434,15 @@
│ │ │    </a>
│ │ │    <span class="text">SMALL_BIG_EXT</span>
│ │ │  </h2>
│ │ │  <table><thead><tr><th style="text-align: left;">1</th><th style="text-align: left;">1</th><th style="text-align: left;">1</th><th style="text-align: left;">n</th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">110</code></td><td style="text-align: left;"><code class="inline">n</code></td><td style="text-align: left;"><code class="inline">Sign</code></td><td style="text-align: left;"><code class="inline">d(0)</code> ... <code class="inline">d(n-1)</code></td></tr></tbody></table><p>Bignums are stored in unary form with a <code class="inline">Sign</code> byte, that is, 0 if the bignum is
│ │ │  positive and 1 if it is negative. The digits are stored with the least
│ │ │  significant byte stored first. To calculate the integer, the following formula
│ │ │  can be used:</p><pre><code class="makeup erlang" translate="no"><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">256</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9064754225-1">(</span><span class="ss">d0</span><span class="o">*</span><span class="n">B</span><span class="err">^</span><span class="mi">0</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="ss">d1</span><span class="o">*</span><span class="n">B</span><span class="err">^</span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="ss">d2</span><span class="o">*</span><span class="n">B</span><span class="err">^</span><span class="mi">2</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="nf">d</span><span class="p" data-group-id="9064754225-2">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="9064754225-2">)</span><span class="o">*</span><span class="n">B</span><span class="err">^</span><span class="p" data-group-id="9064754225-3">(</span><span class="ss">n</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="9064754225-3">)</span><span class="p" data-group-id="9064754225-1">)</span></code></pre><h2 id="large_big_ext" class="section-heading">
│ │ │ +</span><span class="p" data-group-id="3171846464-1">(</span><span class="ss">d0</span><span class="o">*</span><span class="n">B</span><span class="err">^</span><span class="mi">0</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="ss">d1</span><span class="o">*</span><span class="n">B</span><span class="err">^</span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="ss">d2</span><span class="o">*</span><span class="n">B</span><span class="err">^</span><span class="mi">2</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="nf">d</span><span class="p" data-group-id="3171846464-2">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="3171846464-2">)</span><span class="o">*</span><span class="n">B</span><span class="err">^</span><span class="p" data-group-id="3171846464-3">(</span><span class="ss">n</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="3171846464-3">)</span><span class="p" data-group-id="3171846464-1">)</span></code></pre><h2 id="large_big_ext" class="section-heading">
│ │ │    <a href="#large_big_ext" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">LARGE_BIG_EXT</span>
│ │ │  </h2>
│ │ │  <table><thead><tr><th style="text-align: left;">1</th><th style="text-align: left;">4</th><th style="text-align: left;">1</th><th style="text-align: left;">n</th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">111</code></td><td style="text-align: left;"><code class="inline">n</code></td><td style="text-align: left;"><code class="inline">Sign</code></td><td style="text-align: left;"><code class="inline">d(0)</code> ... <code class="inline">d(n-1)</code></td></tr></tbody></table><p>Same as <a href="erl_ext_dist.html#small_big_ext"><code class="inline">SMALL_BIG_EXT</code></a> except that the length
│ │ │  field is an unsigned 4 byte integer.</p><h2 id="reference_ext-deprecated" class="section-heading">
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-17.0/doc/html/erl_nif.html
│ │ │ @@ -161,27 +161,27 @@
│ │ │  }
│ │ │  
│ │ │  static ErlNifFunc nif_funcs[] =
│ │ │  {
│ │ │      {&quot;hello&quot;, 0, hello}
│ │ │  };
│ │ │  
│ │ │ -ERL_NIF_INIT(niftest,nif_funcs,NULL,NULL,NULL,NULL)</code></pre><p>The Erlang module can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9771803133-1">(</span><span class="ss">niftest</span><span class="p" data-group-id="9771803133-1">)</span><span class="p">.</span><span class="w">
│ │ │ +ERL_NIF_INIT(niftest,nif_funcs,NULL,NULL,NULL,NULL)</code></pre><p>The Erlang module can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0969592334-1">(</span><span class="ss">niftest</span><span class="p" data-group-id="0969592334-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9771803133-2">(</span><span class="p" data-group-id="9771803133-3">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">hello</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9771803133-3">]</span><span class="p" data-group-id="9771803133-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0969592334-2">(</span><span class="p" data-group-id="0969592334-3">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">hello</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0969592334-3">]</span><span class="p" data-group-id="0969592334-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">nifs</span><span class="p" data-group-id="9771803133-4">(</span><span class="p" data-group-id="9771803133-5">[</span><span class="ss">hello</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9771803133-5">]</span><span class="p" data-group-id="9771803133-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">nifs</span><span class="p" data-group-id="0969592334-4">(</span><span class="p" data-group-id="0969592334-5">[</span><span class="ss">hello</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0969592334-5">]</span><span class="p" data-group-id="0969592334-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="9771803133-6">(</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9771803133-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="0969592334-6">(</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0969592334-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="9771803133-7">(</span><span class="p" data-group-id="9771803133-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -      </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="9771803133-8">(</span><span class="s">&quot;./niftest&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="9771803133-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="0969592334-7">(</span><span class="p" data-group-id="0969592334-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +      </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="0969592334-8">(</span><span class="s">&quot;./niftest&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="0969592334-8">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">hello</span><span class="p" data-group-id="9771803133-9">(</span><span class="p" data-group-id="9771803133-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -      </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="9771803133-10">(</span><span class="s">&quot;NIF library not loaded&quot;</span><span class="p" data-group-id="9771803133-10">)</span><span class="p">.</span></code></pre><p>Compile and test can look as follows (on Linux):</p><pre><code class="text">$&gt; gcc -fPIC -shared -o niftest.so niftest.c -I $ERL_ROOT/usr/include/
│ │ │ +</span><span class="nf">hello</span><span class="p" data-group-id="0969592334-9">(</span><span class="p" data-group-id="0969592334-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +      </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="0969592334-10">(</span><span class="s">&quot;NIF library not loaded&quot;</span><span class="p" data-group-id="0969592334-10">)</span><span class="p">.</span></code></pre><p>Compile and test can look as follows (on Linux):</p><pre><code class="text">$&gt; gcc -fPIC -shared -o niftest.so niftest.c -I $ERL_ROOT/usr/include/
│ │ │  $&gt; erl
│ │ │  
│ │ │  1&gt; c(niftest).
│ │ │  {ok,niftest}
│ │ │  2&gt; niftest:hello().
│ │ │  &quot;Hello world!&quot;</code></pre><p>In the example above the <a href="../../../doc/system/code_loading.html#on_load"><em><code class="inline">on_load</code></em></a>
│ │ │  directive is used get function <code class="inline">init</code> called automatically when the module is
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-17.0/doc/html/erl_prim_loader.html
│ │ │ @@ -398,15 +398,15 @@
│ │ │                          when Filename :: <a href="erlang.html#t:string/0">string</a>(), FileInfo :: <a href="../../../lib/kernel-11.0/doc/html/file.html#t:file_info/0">file:file_info</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Retrieves information about a file.</p><p>Returns <code class="inline">{ok, FileInfo}</code> if successful, otherwise <code class="inline">error</code>. <code class="inline">FileInfo</code> is a
│ │ │  record <a href="../../../lib/kernel-11.0/doc/html/file.html#t:file_info/0"><code class="inline">file_info</code></a>, defined in the Kernel include file
│ │ │   <code class="inline">file.hrl</code>. Include the following directive in the module from which the
│ │ │ -function is called:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="3390332269-1">(</span><span class="s">&quot;kernel/include/file.hrl&quot;</span><span class="p" data-group-id="3390332269-1">)</span><span class="p">.</span></code></pre><p>For more information about the record see <a href="../../../lib/kernel-11.0/doc/html/file.html#read_file_info/2"><code class="inline">file:read_file_info/2</code></a>.</p><p><code class="inline">Filename</code> can also be a file in an archive, for example,
│ │ │ +function is called:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="3011826547-1">(</span><span class="s">&quot;kernel/include/file.hrl&quot;</span><span class="p" data-group-id="3011826547-1">)</span><span class="p">.</span></code></pre><p>For more information about the record see <a href="../../../lib/kernel-11.0/doc/html/file.html#read_file_info/2"><code class="inline">file:read_file_info/2</code></a>.</p><p><code class="inline">Filename</code> can also be a file in an archive, for example,
│ │ │  <code class="inline">$OTPROOT/lib/mnesia-4.4.7.ez/mnesia-4.4.7/ebin/mnesia</code>. For information
│ │ │  about archive files, see <a href="../../../lib/kernel-11.0/doc/html/code.html"><code class="inline">code</code></a>.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="read_link_info/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-17.0/doc/html/erl_tracer.html
│ │ │ @@ -145,44 +145,44 @@
│ │ │    <span class="text">Erl Tracer Module Example</span>
│ │ │  </h2>
│ │ │  <p>In this example, a tracer module with a NIF back end sends a message for each
│ │ │  <code class="inline">send</code> trace tag containing only the sender and receiver. Using this tracer
│ │ │  module, a much more lightweight message tracer is used, which only records who
│ │ │  sent messages to who.</p><p>The following is an example session using it on Linux:</p><pre><code class="makeup erlang" translate="no"><span class="sc">$ </span><span class="ss">gcc</span><span class="w"> </span><span class="o">-</span><span class="n">I</span><span class="w"> </span><span class="ss">erts</span><span class="o">-</span><span class="mf">8.0</span><span class="o">/</span><span class="ss">include</span><span class="o">/</span><span class="w"> </span><span class="o">-</span><span class="ss">fPIC</span><span class="w"> </span><span class="o">-</span><span class="ss">shared</span><span class="w"> </span><span class="o">-</span><span class="ss">o</span><span class="w"> </span><span class="ss">erl_msg_tracer</span><span class="p">.</span><span class="ss">so</span><span class="w"> </span><span class="ss">erl_msg_tracer</span><span class="p">.</span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="sc">$ </span><span class="ss">erl</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">19</span><span class="w"> </span><span class="p" data-group-id="0189024943-1">[</span><span class="n">DEVELOPMENT</span><span class="p" data-group-id="0189024943-1">]</span><span class="w"> </span><span class="p" data-group-id="0189024943-2">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">8.0</span><span class="p" data-group-id="0189024943-2">]</span><span class="w"> </span><span class="p" data-group-id="0189024943-3">[</span><span class="ss">source</span><span class="o">-</span><span class="ss">ed2b56b</span><span class="p" data-group-id="0189024943-3">]</span><span class="w"> </span><span class="p" data-group-id="0189024943-4">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="0189024943-4">]</span><span class="w"> </span><span class="p" data-group-id="0189024943-5">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="0189024943-5">]</span><span class="w"> </span><span class="p" data-group-id="0189024943-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="0189024943-6">]</span><span class="w"> </span><span class="p" data-group-id="0189024943-7">[</span><span class="ss">hipe</span><span class="p" data-group-id="0189024943-7">]</span><span class="w"> </span><span class="p" data-group-id="0189024943-8">[</span><span class="ss">kernel</span><span class="o">-</span><span class="nc">poll</span><span class="p">:</span><span class="ss">false</span><span class="p" data-group-id="0189024943-8">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">19</span><span class="w"> </span><span class="p" data-group-id="1467970717-1">[</span><span class="n">DEVELOPMENT</span><span class="p" data-group-id="1467970717-1">]</span><span class="w"> </span><span class="p" data-group-id="1467970717-2">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">8.0</span><span class="p" data-group-id="1467970717-2">]</span><span class="w"> </span><span class="p" data-group-id="1467970717-3">[</span><span class="ss">source</span><span class="o">-</span><span class="ss">ed2b56b</span><span class="p" data-group-id="1467970717-3">]</span><span class="w"> </span><span class="p" data-group-id="1467970717-4">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="1467970717-4">]</span><span class="w"> </span><span class="p" data-group-id="1467970717-5">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="1467970717-5">]</span><span class="w"> </span><span class="p" data-group-id="1467970717-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="1467970717-6">]</span><span class="w"> </span><span class="p" data-group-id="1467970717-7">[</span><span class="ss">hipe</span><span class="p" data-group-id="1467970717-7">]</span><span class="w"> </span><span class="p" data-group-id="1467970717-8">[</span><span class="ss">kernel</span><span class="o">-</span><span class="nc">poll</span><span class="p">:</span><span class="ss">false</span><span class="p" data-group-id="1467970717-8">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V8</span><span class="p">.</span><span class="mi">0</span><span class="w">  </span><span class="p" data-group-id="0189024943-9">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="0189024943-9">)</span><span class="w">
│ │ │ -</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="0189024943-10">(</span><span class="ss">erl_msg_tracer</span><span class="p" data-group-id="0189024943-10">)</span><span class="p">,</span><span class="w"> </span><span class="nc">erl_msg_tracer</span><span class="p">:</span><span class="nf">load</span><span class="p" data-group-id="0189024943-11">(</span><span class="p" data-group-id="0189024943-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V8</span><span class="p">.</span><span class="mi">0</span><span class="w">  </span><span class="p" data-group-id="1467970717-9">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="1467970717-9">)</span><span class="w">
│ │ │ +</span><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="1467970717-10">(</span><span class="ss">erl_msg_tracer</span><span class="p" data-group-id="1467970717-10">)</span><span class="p">,</span><span class="w"> </span><span class="nc">erl_msg_tracer</span><span class="p">:</span><span class="nf">load</span><span class="p" data-group-id="1467970717-11">(</span><span class="p" data-group-id="1467970717-11">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">Tracer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="0189024943-12">(</span><span class="k">fun</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="0189024943-13">(</span><span class="p" data-group-id="0189024943-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0189024943-14">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="0189024943-15">[</span><span class="n">M</span><span class="p" data-group-id="0189024943-15">]</span><span class="p" data-group-id="0189024943-14">)</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="0189024943-16">(</span><span class="p" data-group-id="0189024943-16">)</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p" data-group-id="0189024943-12">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">Tracer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="1467970717-12">(</span><span class="k">fun</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="1467970717-13">(</span><span class="p" data-group-id="1467970717-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1467970717-14">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="1467970717-15">[</span><span class="n">M</span><span class="p" data-group-id="1467970717-15">]</span><span class="p" data-group-id="1467970717-14">)</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="1467970717-16">(</span><span class="p" data-group-id="1467970717-16">)</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p" data-group-id="1467970717-12">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.37</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="0189024943-17">(</span><span class="ss">new</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0189024943-18">[</span><span class="nb">send</span><span class="p">,</span><span class="p" data-group-id="0189024943-19">{</span><span class="ss">tracer</span><span class="p">,</span><span class="w"> </span><span class="ss">erl_msg_tracer</span><span class="p">,</span><span class="w"> </span><span class="n">Tracer</span><span class="p" data-group-id="0189024943-19">}</span><span class="p" data-group-id="0189024943-18">]</span><span class="p" data-group-id="0189024943-17">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="1467970717-17">(</span><span class="ss">new</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1467970717-18">[</span><span class="nb">send</span><span class="p">,</span><span class="p" data-group-id="1467970717-19">{</span><span class="ss">tracer</span><span class="p">,</span><span class="w"> </span><span class="ss">erl_msg_tracer</span><span class="p">,</span><span class="w"> </span><span class="n">Tracer</span><span class="p" data-group-id="1467970717-19">}</span><span class="p" data-group-id="1467970717-18">]</span><span class="p" data-group-id="1467970717-17">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">0</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0189024943-20">{</span><span class="nb">trace</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.39</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.27</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0189024943-20">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="p" data-group-id="0189024943-21">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="0189024943-21">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="0189024943-22">(</span><span class="s">&quot;/tmp/tmp.data&quot;</span><span class="p">,</span><span class="p" data-group-id="0189024943-23">[</span><span class="ss">write</span><span class="p" data-group-id="0189024943-23">]</span><span class="p" data-group-id="0189024943-22">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0189024943-24">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.486</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.40</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0189024943-24">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0189024943-25">{</span><span class="nb">trace</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.40</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.21</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0189024943-25">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0189024943-26">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.487</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0189024943-26">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0189024943-27">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.488</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0189024943-27">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0189024943-28">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.489</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0189024943-28">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0189024943-29">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.490</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0189024943-29">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0189024943-30">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.40</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0189024943-30">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0189024943-31">{</span><span class="nb">trace</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.41</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.27</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0189024943-31">}</span><span class="w">
│ │ │ -</span><span class="mi">5</span><span class="o">&gt;</span></code></pre><p><code class="inline">erl_msg_tracer.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8045285200-1">(</span><span class="ss">erl_msg_tracer</span><span class="p" data-group-id="8045285200-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1467970717-20">{</span><span class="nb">trace</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.39</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.27</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="1467970717-20">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="p" data-group-id="1467970717-21">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="1467970717-21">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="1467970717-22">(</span><span class="s">&quot;/tmp/tmp.data&quot;</span><span class="p">,</span><span class="p" data-group-id="1467970717-23">[</span><span class="ss">write</span><span class="p" data-group-id="1467970717-23">]</span><span class="p" data-group-id="1467970717-22">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1467970717-24">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.486</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.40</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="1467970717-24">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1467970717-25">{</span><span class="nb">trace</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.40</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.21</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="1467970717-25">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1467970717-26">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.487</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="1467970717-26">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1467970717-27">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.488</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="1467970717-27">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1467970717-28">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.489</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="1467970717-28">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1467970717-29">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.490</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="1467970717-29">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1467970717-30">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.40</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="1467970717-30">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1467970717-31">{</span><span class="nb">trace</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.41</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.27</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="1467970717-31">}</span><span class="w">
│ │ │ +</span><span class="mi">5</span><span class="o">&gt;</span></code></pre><p><code class="inline">erl_msg_tracer.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9349017565-1">(</span><span class="ss">erl_msg_tracer</span><span class="p" data-group-id="9349017565-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8045285200-2">(</span><span class="p" data-group-id="8045285200-3">[</span><span class="ss">enabled</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="nb">trace</span><span class="p">/</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="ss">load</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8045285200-3">]</span><span class="p" data-group-id="8045285200-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9349017565-2">(</span><span class="p" data-group-id="9349017565-3">[</span><span class="ss">enabled</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="nb">trace</span><span class="p">/</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="ss">load</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9349017565-3">]</span><span class="p" data-group-id="9349017565-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">load</span><span class="p" data-group-id="8045285200-4">(</span><span class="p" data-group-id="8045285200-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="8045285200-5">(</span><span class="s">&quot;erl_msg_tracer&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8045285200-6">[</span><span class="p" data-group-id="8045285200-6">]</span><span class="p" data-group-id="8045285200-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">load</span><span class="p" data-group-id="9349017565-4">(</span><span class="p" data-group-id="9349017565-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="9349017565-5">(</span><span class="s">&quot;erl_msg_tracer&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9349017565-6">[</span><span class="p" data-group-id="9349017565-6">]</span><span class="p" data-group-id="9349017565-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">enabled</span><span class="p" data-group-id="8045285200-7">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="8045285200-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">enabled</span><span class="p" data-group-id="9349017565-7">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9349017565-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">error</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">trace</span><span class="p" data-group-id="8045285200-8">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="8045285200-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">trace</span><span class="p" data-group-id="9349017565-8">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9349017565-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">error</span><span class="p">.</span></code></pre><p><code class="inline">erl_msg_tracer.c</code>:</p><pre><code class="c">#include &lt;erl_nif.h&gt;
│ │ │  
│ │ │  /* NIF interface declarations */
│ │ │  static int load(ErlNifEnv* env, void** priv_data, ERL_NIF_TERM load_info);
│ │ │  static int upgrade(ErlNifEnv* env, void** priv_data, void** old_priv_data, ERL_NIF_TERM load_info);
│ │ │  static void unload(ErlNifEnv* env, void* priv_data);
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-17.0/doc/html/erlang.html
│ │ │ @@ -6989,19 +6989,19 @@
│ │ │  <p>Returns an integer or float representing the absolute value of <code class="inline">Float</code>
│ │ │  or <code class="inline">Int</code>.</p><h2 id="abs/1-examples" class="section-heading">
│ │ │    <a href="#abs/1-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">abs</span><span class="p" data-group-id="7558724524-1">(</span><span class="o">-</span><span class="mf">3.33</span><span class="p" data-group-id="7558724524-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">abs</span><span class="p" data-group-id="0184008055-1">(</span><span class="o">-</span><span class="mf">3.33</span><span class="p" data-group-id="0184008055-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">3.33</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">abs</span><span class="p" data-group-id="7558724524-2">(</span><span class="o">-</span><span class="mi">3</span><span class="p" data-group-id="7558724524-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">abs</span><span class="p" data-group-id="0184008055-2">(</span><span class="o">-</span><span class="mi">3</span><span class="p" data-group-id="0184008055-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">abs</span><span class="p" data-group-id="7558724524-3">(</span><span class="mi">5</span><span class="p" data-group-id="7558724524-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">abs</span><span class="p" data-group-id="0184008055-3">(</span><span class="mi">5</span><span class="p" data-group-id="0184008055-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">5</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="adler32/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#adler32/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -7027,15 +7027,15 @@
│ │ │  <p>Computes and returns the adler32 checksum for <code class="inline">Data</code>.</p><h2 id="adler32/1-examples" class="section-heading">
│ │ │    <a href="#adler32/1-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;abc&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="5263548114-1">(</span><span class="n">Data</span><span class="p" data-group-id="5263548114-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="9092480572-1">(</span><span class="n">Data</span><span class="p" data-group-id="9092480572-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">38600999</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="adler32/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#adler32/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -7056,19 +7056,19 @@
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> adler32(OldAdler, Data) -> <a href="#t:non_neg_integer/0">non_neg_integer</a>() when OldAdler :: <a href="#t:non_neg_integer/0">non_neg_integer</a>(), Data :: <a href="#t:iodata/0">iodata</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Continues computing the adler32 checksum by combining the previous checksum,
│ │ │  <code class="inline">OldAdler</code>, with the checksum of <code class="inline">Data</code>.</p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Data1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;abc&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Data2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;def&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="9321033535-1">(</span><span class="n">Data1</span><span class="p" data-group-id="9321033535-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="5712368414-1">(</span><span class="n">Data1</span><span class="p" data-group-id="5712368414-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">38600999</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="9321033535-2">(</span><span class="n">X</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="9321033535-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="5712368414-2">(</span><span class="n">X</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="5712368414-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">136184406</span></code></pre><p>assigns the same value to <code class="inline">Y</code> as this:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Data1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;abc&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Data2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;def&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="3105317108-1">(</span><span class="p" data-group-id="3105317108-2">[</span><span class="n">Data1</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="3105317108-2">]</span><span class="p" data-group-id="3105317108-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="5145687771-1">(</span><span class="p" data-group-id="5145687771-2">[</span><span class="n">Data1</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="5145687771-2">]</span><span class="p" data-group-id="5145687771-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">136184406</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="adler32_combine/3">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#adler32_combine/3" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -7093,23 +7093,23 @@
│ │ │                               SecondAdler :: <a href="#t:non_neg_integer/0">non_neg_integer</a>(),
│ │ │                               SecondSize :: <a href="#t:non_neg_integer/0">non_neg_integer</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Combines two previously computed adler32 checksums.</p><p>This computation requires the size of the data object for the second checksum
│ │ │  to be known.</p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Data1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;abc&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Data2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;def&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="4231883918-1">(</span><span class="n">Data1</span><span class="p" data-group-id="4231883918-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="9442083941-1">(</span><span class="n">Data1</span><span class="p" data-group-id="9442083941-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">38600999</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="n">Z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="4231883918-2">(</span><span class="n">X</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="4231883918-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="n">Z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="9442083941-2">(</span><span class="n">X</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="9442083941-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">136184406</span></code></pre><p>assigns the same value to <code class="inline">Z</code> as this:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Data1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;abc&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Data2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;def&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="2384383200-1">(</span><span class="n">Data1</span><span class="p" data-group-id="2384383200-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="3519199769-1">(</span><span class="n">Data1</span><span class="p" data-group-id="3519199769-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">38600999</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="2384383200-2">(</span><span class="n">Data2</span><span class="p" data-group-id="2384383200-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="3519199769-2">(</span><span class="n">Data2</span><span class="p" data-group-id="3519199769-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">39780656</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="n">Z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32_combine</span><span class="p" data-group-id="2384383200-3">(</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="nf">iolist_size</span><span class="p" data-group-id="2384383200-4">(</span><span class="n">Data2</span><span class="p" data-group-id="2384383200-4">)</span><span class="p" data-group-id="2384383200-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="n">Z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32_combine</span><span class="p" data-group-id="3519199769-3">(</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="nf">iolist_size</span><span class="p" data-group-id="3519199769-4">(</span><span class="n">Data2</span><span class="p" data-group-id="3519199769-4">)</span><span class="p" data-group-id="3519199769-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">136184406</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="alias/0">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#alias/0" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -7175,35 +7175,35 @@
│ │ │  call to <a href="#unalias/1"><code class="inline">unalias/1</code></a>.</p></li><li><p><strong><code class="inline">priority</code></strong> - <a href="" id="priority_alias"></a> Since OTP 28.0</p><p>The alias can be used for sending
│ │ │  <a href="../../../doc/system/ref_man_processes.html#priority-messages">priority messages</a> to the
│ │ │  process that created this alias. An alias created with this option is also
│ │ │  known as a <em>priority process alias</em> or shorter <em>priority alias</em>.</p><section role="note" class="admonition warning"><h4 class="admonition-title warning">Warning</h4><p>You <em>very seldom</em> need to resort to using priority messages and you may
│ │ │  <a href="../../../doc/system/ref_man_processes.html#priority-message-warning">cause issues</a>
│ │ │  instead of solving issues if not used with care.</p></section><p>For more information see, the
│ │ │  <a href="../../../doc/system/ref_man_processes.html#enable-prio-msg-recv">Enabling Priority Message Reception</a>
│ │ │ -section of the <em>Erlang Reference Manual</em>.</p></li></ul><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server</span><span class="p" data-group-id="9119810847-1">(</span><span class="p" data-group-id="9119810847-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +section of the <em>Erlang Reference Manual</em>.</p></li></ul><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server</span><span class="p" data-group-id="3422243905-1">(</span><span class="p" data-group-id="3422243905-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9119810847-2">{</span><span class="ss">request</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="9119810847-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">perform_request</span><span class="p" data-group-id="9119810847-3">(</span><span class="n">Request</span><span class="p" data-group-id="9119810847-3">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">AliasReqId</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9119810847-4">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="9119810847-4">}</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3422243905-2">{</span><span class="ss">request</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="3422243905-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">Result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">perform_request</span><span class="p" data-group-id="3422243905-3">(</span><span class="n">Request</span><span class="p" data-group-id="3422243905-3">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">AliasReqId</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3422243905-4">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="3422243905-4">}</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">server</span><span class="p" data-group-id="9119810847-5">(</span><span class="p" data-group-id="9119810847-5">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">server</span><span class="p" data-group-id="3422243905-5">(</span><span class="p" data-group-id="3422243905-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="9119810847-6">(</span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="9119810847-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">AliasReqId</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alias</span><span class="p" data-group-id="9119810847-7">(</span><span class="p" data-group-id="9119810847-8">[</span><span class="ss">reply</span><span class="p" data-group-id="9119810847-8">]</span><span class="p" data-group-id="9119810847-7">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">ServerPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9119810847-9">{</span><span class="ss">request</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="9119810847-9">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="3422243905-6">(</span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="3422243905-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">AliasReqId</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alias</span><span class="p" data-group-id="3422243905-7">(</span><span class="p" data-group-id="3422243905-8">[</span><span class="ss">reply</span><span class="p" data-group-id="3422243905-8">]</span><span class="p" data-group-id="3422243905-7">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">ServerPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3422243905-9">{</span><span class="ss">request</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="3422243905-9">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="c1">%% Alias will be automatically deactivated if we receive a reply</span><span class="w">
│ │ │      </span><span class="c1">%% since we used the &#39;reply&#39; option...</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9119810847-10">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="9119810847-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Result</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3422243905-10">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="3422243905-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Result</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">unalias</span><span class="p" data-group-id="9119810847-11">(</span><span class="n">AliasReqId</span><span class="p" data-group-id="9119810847-11">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">unalias</span><span class="p" data-group-id="3422243905-11">(</span><span class="n">AliasReqId</span><span class="p" data-group-id="3422243905-11">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="c1">%% Flush message queue in case the reply arrived</span><span class="w">
│ │ │              </span><span class="c1">%% just before the alias was deactivated...</span><span class="w">
│ │ │ -            </span><span class="k">receive</span><span class="w"> </span><span class="p" data-group-id="9119810847-12">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="9119810847-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Result</span><span class="w">
│ │ │ -            </span><span class="k">after</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="9119810847-13">(</span><span class="ss">timeout</span><span class="p" data-group-id="9119810847-13">)</span><span class="w">
│ │ │ +            </span><span class="k">receive</span><span class="w"> </span><span class="p" data-group-id="3422243905-12">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="3422243905-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Result</span><span class="w">
│ │ │ +            </span><span class="k">after</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="3422243905-13">(</span><span class="ss">timeout</span><span class="p" data-group-id="3422243905-13">)</span><span class="w">
│ │ │              </span><span class="k">end</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Note that both the server and the client in this example must be executing on at
│ │ │  least OTP 24 systems in order for this to work.</p><p>For more information on process aliases see the
│ │ │  <a href="../../../doc/system/ref_man_processes.html#process-aliases"><em>Process Aliases</em></a> section of
│ │ │  the <em>Erlang Reference Manual</em>.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │ @@ -7235,16 +7235,16 @@
│ │ │  <a href="#list_to_tuple/1"><code class="inline">list_to_tuple(tuple_to_list(Tuple1) ++ [Term])</code></a>, but
│ │ │  faster.</p><h2 id="append_element/2-examples" class="section-heading">
│ │ │    <a href="#append_element/2-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">append_element</span><span class="p" data-group-id="5392003401-1">(</span><span class="p" data-group-id="5392003401-2">{</span><span class="ss">one</span><span class="p">,</span><span class="w"> </span><span class="ss">two</span><span class="p" data-group-id="5392003401-2">}</span><span class="p">,</span><span class="w"> </span><span class="ss">three</span><span class="p" data-group-id="5392003401-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5392003401-3">{</span><span class="ss">one</span><span class="p">,</span><span class="ss">two</span><span class="p">,</span><span class="ss">three</span><span class="p" data-group-id="5392003401-3">}</span></code></pre>
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">append_element</span><span class="p" data-group-id="8565994604-1">(</span><span class="p" data-group-id="8565994604-2">{</span><span class="ss">one</span><span class="p">,</span><span class="w"> </span><span class="ss">two</span><span class="p" data-group-id="8565994604-2">}</span><span class="p">,</span><span class="w"> </span><span class="ss">three</span><span class="p" data-group-id="8565994604-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8565994604-3">{</span><span class="ss">one</span><span class="p">,</span><span class="ss">two</span><span class="p">,</span><span class="ss">three</span><span class="p" data-group-id="8565994604-3">}</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="apply/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#apply/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -7298,17 +7298,17 @@
│ │ │            <pre translate="no"><span class="attribute">-spec</span> apply(Module, Function, Args) -> <a href="#t:term/0">term</a>()
│ │ │                 when Module :: <a href="#t:module/0">module</a>(), Function :: <a href="#t:atom/0">atom</a>(), Args :: [<a href="#t:term/0">term</a>()].</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns the result of applying <code class="inline">Function</code> in <code class="inline">Module</code> to <code class="inline">Args</code>. The applied
│ │ │  function must be exported from <code class="inline">Module</code>. The arity of the function is the length
│ │ │ -of <code class="inline">Args</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">apply</span><span class="p" data-group-id="9469523737-1">(</span><span class="ss">lists</span><span class="p">,</span><span class="w"> </span><span class="ss">reverse</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9469523737-2">[</span><span class="p" data-group-id="9469523737-3">[</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="9469523737-3">]</span><span class="p" data-group-id="9469523737-2">]</span><span class="p" data-group-id="9469523737-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9469523737-4">[</span><span class="ss">c</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="9469523737-4">]</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">apply</span><span class="p" data-group-id="9469523737-5">(</span><span class="ss">erlang</span><span class="p">,</span><span class="w"> </span><span class="nb">atom_to_list</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9469523737-6">[</span><span class="ss">&#39;Erlang&#39;</span><span class="p" data-group-id="9469523737-6">]</span><span class="p" data-group-id="9469523737-5">)</span><span class="p">.</span><span class="w">
│ │ │ +of <code class="inline">Args</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">apply</span><span class="p" data-group-id="9762114154-1">(</span><span class="ss">lists</span><span class="p">,</span><span class="w"> </span><span class="ss">reverse</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9762114154-2">[</span><span class="p" data-group-id="9762114154-3">[</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="9762114154-3">]</span><span class="p" data-group-id="9762114154-2">]</span><span class="p" data-group-id="9762114154-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9762114154-4">[</span><span class="ss">c</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="9762114154-4">]</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">apply</span><span class="p" data-group-id="9762114154-5">(</span><span class="ss">erlang</span><span class="p">,</span><span class="w"> </span><span class="nb">atom_to_list</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9762114154-6">[</span><span class="ss">&#39;Erlang&#39;</span><span class="p" data-group-id="9762114154-6">]</span><span class="p" data-group-id="9762114154-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;Erlang&quot;</span></code></pre><p>If the number of arguments are known at compile time, the call is better written
│ │ │  as <code class="inline">Module:Function(Arg1, Arg2, ..., ArgN)</code>.</p><p>Failure: <a href="../../../lib/kernel-11.0/doc/html/error_handler.html#undefined_function/3"><code class="inline">error_handler:undefined_function/3</code></a> is called if the applied function
│ │ │  is not exported. The error handler can be redefined (see <a href="#process_flag/2"><code class="inline">process_flag/2</code></a>). If
│ │ │  <code class="inline">error_handler</code> is undefined, or if the user has redefined the default
│ │ │  <code class="inline">error_handler</code> so the replacement module is undefined, an error with reason
│ │ │  <code class="inline">undef</code> is generated.</p>
│ │ │    </section>
│ │ │ @@ -7376,19 +7376,19 @@
│ │ │  <a href="#atom_to_binary/2"><code class="inline">atom_to_binary(Atom, latin1)</code></a> may fail if the text
│ │ │  representation for <code class="inline">Atom</code> contains a Unicode character &gt; 255.</p></section><h2 id="atom_to_binary/2-examples" class="section-heading">
│ │ │    <a href="#atom_to_binary/2-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">atom_to_binary</span><span class="p" data-group-id="7661618161-1">(</span><span class="ss">&#39;Erlang&#39;</span><span class="p">,</span><span class="w"> </span><span class="ss">latin1</span><span class="p" data-group-id="7661618161-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7661618161-2">&lt;&lt;</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="7661618161-2">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">atom_to_binary</span><span class="p" data-group-id="7661618161-3">(</span><span class="ss">&#39;π&#39;</span><span class="p">,</span><span class="w"> </span><span class="ss">unicode</span><span class="p" data-group-id="7661618161-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7661618161-4">&lt;&lt;</span><span class="mi">207</span><span class="p">,</span><span class="mi">128</span><span class="p" data-group-id="7661618161-4">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">atom_to_binary</span><span class="p" data-group-id="7661618161-5">(</span><span class="ss">&#39;π&#39;</span><span class="p">,</span><span class="w"> </span><span class="ss">latin1</span><span class="p" data-group-id="7661618161-5">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">atom_to_binary</span><span class="p" data-group-id="9196909744-1">(</span><span class="ss">&#39;Erlang&#39;</span><span class="p">,</span><span class="w"> </span><span class="ss">latin1</span><span class="p" data-group-id="9196909744-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9196909744-2">&lt;&lt;</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="9196909744-2">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">atom_to_binary</span><span class="p" data-group-id="9196909744-3">(</span><span class="ss">&#39;π&#39;</span><span class="p">,</span><span class="w"> </span><span class="ss">unicode</span><span class="p" data-group-id="9196909744-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9196909744-4">&lt;&lt;</span><span class="mi">207</span><span class="p">,</span><span class="mi">128</span><span class="p" data-group-id="9196909744-4">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">atom_to_binary</span><span class="p" data-group-id="9196909744-5">(</span><span class="ss">&#39;π&#39;</span><span class="p">,</span><span class="w"> </span><span class="ss">latin1</span><span class="p" data-group-id="9196909744-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: bad argument
│ │ │       in function  atom_to_binary/2
│ │ │          called as atom_to_binary(&#39;π&#39;,latin1)
│ │ │          *** argument 1: contains a character not expressible in latin1</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="atom_to_list/1">
│ │ │ @@ -7420,20 +7420,20 @@
│ │ │  of <code class="inline">Atom</code>.</p><p>See the <a href="../../../lib/stdlib-8.0/doc/html/unicode.html"><code class="inline">unicode</code></a> module for instructions on converting the resulting list into
│ │ │  different formats.</p><h2 id="atom_to_list/1-examples" class="section-heading">
│ │ │    <a href="#atom_to_list/1-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="8646333151-1">(</span><span class="ss">&#39;Erlang&#39;</span><span class="p" data-group-id="8646333151-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="1067691945-1">(</span><span class="ss">&#39;Erlang&#39;</span><span class="p" data-group-id="1067691945-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;Erlang&quot;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="8646333151-2">(</span><span class="ss">&#39;π&#39;</span><span class="p" data-group-id="8646333151-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8646333151-3">[</span><span class="mi">960</span><span class="p" data-group-id="8646333151-3">]</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="8646333151-4">(</span><span class="ss">&#39;你好&#39;</span><span class="p" data-group-id="8646333151-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8646333151-5">[</span><span class="mi">20320</span><span class="p">,</span><span class="mi">22909</span><span class="p" data-group-id="8646333151-5">]</span></code></pre>
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="1067691945-2">(</span><span class="ss">&#39;π&#39;</span><span class="p" data-group-id="1067691945-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1067691945-3">[</span><span class="mi">960</span><span class="p" data-group-id="1067691945-3">]</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="1067691945-4">(</span><span class="ss">&#39;你好&#39;</span><span class="p" data-group-id="1067691945-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1067691945-5">[</span><span class="mi">20320</span><span class="p">,</span><span class="mi">22909</span><span class="p" data-group-id="1067691945-5">]</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="binary_part/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#binary_part/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -7501,21 +7501,21 @@
│ │ │  outside the binary.</p><p>For details about the semantics of <code class="inline">Start</code> and <code class="inline">Length</code>, see
│ │ │  <a href="../../../lib/stdlib-8.0/doc/html/binary.html#part/3"><code class="inline">binary:part/3</code></a>.</p><h2 id="binary_part/3-examples" class="section-heading">
│ │ │    <a href="#binary_part/3-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6164274599-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="6164274599-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">binary_part</span><span class="p" data-group-id="6164274599-2">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="6164274599-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6164274599-3">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6164274599-3">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">binary_part</span><span class="p" data-group-id="6164274599-4">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="6164274599-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6164274599-5">&lt;&lt;</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="6164274599-5">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nf">binary_part</span><span class="p" data-group-id="6164274599-6">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="nf">byte_size</span><span class="p" data-group-id="6164274599-7">(</span><span class="n">Bin</span><span class="p" data-group-id="6164274599-7">)</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">5</span><span class="p" data-group-id="6164274599-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6164274599-8">&lt;&lt;</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="6164274599-8">&gt;&gt;</span></code></pre>
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4579952586-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="4579952586-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">binary_part</span><span class="p" data-group-id="4579952586-2">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="4579952586-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4579952586-3">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4579952586-3">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">binary_part</span><span class="p" data-group-id="4579952586-4">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="4579952586-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4579952586-5">&lt;&lt;</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="4579952586-5">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nf">binary_part</span><span class="p" data-group-id="4579952586-6">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="nf">byte_size</span><span class="p" data-group-id="4579952586-7">(</span><span class="n">Bin</span><span class="p" data-group-id="4579952586-7">)</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">5</span><span class="p" data-group-id="4579952586-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4579952586-8">&lt;&lt;</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="4579952586-8">&gt;&gt;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="binary_to_atom/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#binary_to_atom/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -7583,17 +7583,17 @@
│ │ │  capable of decoding any Unicode character. Earlier versions would fail if the
│ │ │  binary contained Unicode characters &gt; 255.</p></section><h2 id="binary_to_atom/2-examples" class="section-heading">
│ │ │    <a href="#binary_to_atom/2-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">binary_to_atom</span><span class="p" data-group-id="9210285241-1">(</span><span class="p" data-group-id="9210285241-2">&lt;&lt;</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="9210285241-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="ss">latin1</span><span class="p" data-group-id="9210285241-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">binary_to_atom</span><span class="p" data-group-id="0919914803-1">(</span><span class="p" data-group-id="0919914803-2">&lt;&lt;</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="0919914803-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="ss">latin1</span><span class="p" data-group-id="0919914803-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">&#39;Erlang&#39;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">binary_to_atom</span><span class="p" data-group-id="9210285241-3">(</span><span class="p" data-group-id="9210285241-4">&lt;&lt;</span><span class="mi">960</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="9210285241-4">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="ss">utf8</span><span class="p" data-group-id="9210285241-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">binary_to_atom</span><span class="p" data-group-id="0919914803-3">(</span><span class="p" data-group-id="0919914803-4">&lt;&lt;</span><span class="mi">960</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="0919914803-4">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="ss">utf8</span><span class="p" data-group-id="0919914803-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">&#39;π&#39;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="binary_to_existing_atom/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#binary_to_existing_atom/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -7671,22 +7671,22 @@
│ │ │  default limits can be found in the
│ │ │  <a href="../../../doc/system/system_limits.html">Efficiency Guide (section System Limits)</a>.</p></section><h2 id="binary_to_existing_atom/2-examples" class="section-heading">
│ │ │    <a href="#binary_to_existing_atom/2-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">binary_to_existing_atom</span><span class="p" data-group-id="8484020899-1">(</span><span class="s">~&quot;definitely_not_existing_at_all&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">utf8</span><span class="p" data-group-id="8484020899-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">binary_to_existing_atom</span><span class="p" data-group-id="4404414843-1">(</span><span class="s">~&quot;definitely_not_existing_at_all&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">utf8</span><span class="p" data-group-id="4404414843-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: bad argument
│ │ │       in function  binary_to_existing_atom/2
│ │ │          called as binary_to_existing_atom(&lt;&lt;&quot;definitely_not_existing_at_all&quot;&gt;&gt;,utf8)
│ │ │          *** argument 1: not an already existing atom</span><span class="w">
│ │ │  </span><span class="gp unselectable">2&gt; </span><span class="ss">hello</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">binary_to_existing_atom</span><span class="p" data-group-id="8484020899-2">(</span><span class="s">~&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">utf8</span><span class="p" data-group-id="8484020899-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">binary_to_existing_atom</span><span class="p" data-group-id="4404414843-2">(</span><span class="s">~&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">utf8</span><span class="p" data-group-id="4404414843-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">hello</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="binary_to_float/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#binary_to_float/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -7717,19 +7717,19 @@
│ │ │  <a href="../../../doc/system/data_types.html">Erlang float literals</a>, except that underscores
│ │ │  are not permitted.</p><p>Failure: <code class="inline">badarg</code> if <code class="inline">Binary</code> contains an invalid representation of a float.</p><h2 id="binary_to_float/1-examples" class="section-heading">
│ │ │    <a href="#binary_to_float/1-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">binary_to_float</span><span class="p" data-group-id="4960016683-1">(</span><span class="s">~&quot;10.5&quot;</span><span class="p" data-group-id="4960016683-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">binary_to_float</span><span class="p" data-group-id="8150708841-1">(</span><span class="s">~&quot;10.5&quot;</span><span class="p" data-group-id="8150708841-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">10.5</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">binary_to_float</span><span class="p" data-group-id="4960016683-2">(</span><span class="s">~&quot;17.0&quot;</span><span class="p" data-group-id="4960016683-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">binary_to_float</span><span class="p" data-group-id="8150708841-2">(</span><span class="s">~&quot;17.0&quot;</span><span class="p" data-group-id="8150708841-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">17.0</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">binary_to_float</span><span class="p" data-group-id="4960016683-3">(</span><span class="p" data-group-id="4960016683-4">&lt;&lt;</span><span class="s">&quot;2.2017764e+1&quot;</span><span class="p" data-group-id="4960016683-4">&gt;&gt;</span><span class="p" data-group-id="4960016683-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">binary_to_float</span><span class="p" data-group-id="8150708841-3">(</span><span class="p" data-group-id="8150708841-4">&lt;&lt;</span><span class="s">&quot;2.2017764e+1&quot;</span><span class="p" data-group-id="8150708841-4">&gt;&gt;</span><span class="p" data-group-id="8150708841-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">22.017764</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="binary_to_integer/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#binary_to_integer/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -7759,19 +7759,19 @@
│ │ │  <p>Returns an integer whose text representation is <code class="inline">Binary</code>.</p><p><a href="#binary_to_integer/1"><code class="inline">binary_to_integer/1</code></a> accepts the same string formats
│ │ │  as <a href="#list_to_integer/1"><code class="inline">list_to_integer/1</code></a>.</p><p>Failure: <code class="inline">badarg</code> if <code class="inline">Binary</code> contains an invalid representation of an integer.</p><h2 id="binary_to_integer/1-examples" class="section-heading">
│ │ │    <a href="#binary_to_integer/1-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="6611272716-1">(</span><span class="p" data-group-id="6611272716-2">&lt;&lt;</span><span class="s">&quot;123&quot;</span><span class="p" data-group-id="6611272716-2">&gt;&gt;</span><span class="p" data-group-id="6611272716-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="5668481295-1">(</span><span class="p" data-group-id="5668481295-2">&lt;&lt;</span><span class="s">&quot;123&quot;</span><span class="p" data-group-id="5668481295-2">&gt;&gt;</span><span class="p" data-group-id="5668481295-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">123</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="6611272716-3">(</span><span class="p" data-group-id="6611272716-4">&lt;&lt;</span><span class="s">&quot;-99&quot;</span><span class="p" data-group-id="6611272716-4">&gt;&gt;</span><span class="p" data-group-id="6611272716-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="5668481295-3">(</span><span class="p" data-group-id="5668481295-4">&lt;&lt;</span><span class="s">&quot;-99&quot;</span><span class="p" data-group-id="5668481295-4">&gt;&gt;</span><span class="p" data-group-id="5668481295-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">-</span><span class="mi">99</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="6611272716-5">(</span><span class="p" data-group-id="6611272716-6">&lt;&lt;</span><span class="s">&quot;+33&quot;</span><span class="p" data-group-id="6611272716-6">&gt;&gt;</span><span class="p" data-group-id="6611272716-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="5668481295-5">(</span><span class="p" data-group-id="5668481295-6">&lt;&lt;</span><span class="s">&quot;+33&quot;</span><span class="p" data-group-id="5668481295-6">&gt;&gt;</span><span class="p" data-group-id="5668481295-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">33</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="binary_to_integer/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#binary_to_integer/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -7800,17 +7800,17 @@
│ │ │  
│ │ │  <p>Returns an integer whose text representation in base <code class="inline">Base</code> is <code class="inline">Binary</code>.</p><h2 id="binary_to_integer/2-example" class="section-heading">
│ │ │    <a href="#binary_to_integer/2-example" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Example</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="5159896067-1">(</span><span class="p" data-group-id="5159896067-2">&lt;&lt;</span><span class="s">&quot;3FF&quot;</span><span class="p" data-group-id="5159896067-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="5159896067-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="3672203584-1">(</span><span class="p" data-group-id="3672203584-2">&lt;&lt;</span><span class="s">&quot;3FF&quot;</span><span class="p" data-group-id="3672203584-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="3672203584-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">1023</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="5159896067-3">(</span><span class="p" data-group-id="5159896067-4">&lt;&lt;</span><span class="s">&quot;101&quot;</span><span class="p" data-group-id="5159896067-4">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="5159896067-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="3672203584-3">(</span><span class="p" data-group-id="3672203584-4">&lt;&lt;</span><span class="s">&quot;101&quot;</span><span class="p" data-group-id="3672203584-4">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="3672203584-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">5</span></code></pre><p><a href="#binary_to_integer/2"><code class="inline">binary_to_integer/2</code></a> accepts the same string formats
│ │ │  as <a href="#list_to_integer/2"><code class="inline">list_to_integer/2</code></a>.</p><p>Failure: <code class="inline">badarg</code> if <code class="inline">Binary</code> contains a invalid representation of an integer.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="binary_to_list/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │ @@ -7838,16 +7838,16 @@
│ │ │  
│ │ │  <p>Returns a list of integers corresponding to the bytes of <code class="inline">Binary</code>.</p><h2 id="binary_to_list/1-examples" class="section-heading">
│ │ │    <a href="#binary_to_list/1-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="5656316823-1">(</span><span class="p" data-group-id="5656316823-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5656316823-2">&gt;&gt;</span><span class="p" data-group-id="5656316823-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5656316823-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5656316823-3">]</span></code></pre>
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="9719698290-1">(</span><span class="p" data-group-id="9719698290-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9719698290-2">&gt;&gt;</span><span class="p" data-group-id="9719698290-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9719698290-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9719698290-3">]</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="binary_to_list/3">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#binary_to_list/3" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -7877,15 +7877,15 @@
│ │ │  code should use <a href="../../../lib/stdlib-8.0/doc/html/binary.html#bin_to_list/3"><code class="inline">binary:bin_to_list/3</code></a>. All functions in
│ │ │  module <code class="inline">binary</code> consistently use zero-based indexing.</p></section><h2 id="binary_to_list/3-examples" class="section-heading">
│ │ │    <a href="#binary_to_list/3-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="3294528599-1">(</span><span class="s">~&quot;abcdef&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3294528599-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="7030118704-1">(</span><span class="s">~&quot;abcdef&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="7030118704-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;bc&quot;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="binary_to_term/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#binary_to_term/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -7918,17 +7918,17 @@
│ │ │  In such cases, use <a href="#binary_to_term/2"><code class="inline">binary_to_term/2</code></a> with the <code class="inline">safe</code>
│ │ │  option.</p></section><h2 id="binary_to_term/1-examples" class="section-heading">
│ │ │    <a href="#binary_to_term/1-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="9544004422-1">(</span><span class="ss">hello</span><span class="p" data-group-id="9544004422-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9544004422-2">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">119</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="9544004422-2">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="ss">hello</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="9544004422-3">(</span><span class="n">Bin</span><span class="p" data-group-id="9544004422-3">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="1460185266-1">(</span><span class="ss">hello</span><span class="p" data-group-id="1460185266-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1460185266-2">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">119</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="1460185266-2">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="ss">hello</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="1460185266-3">(</span><span class="n">Bin</span><span class="p" data-group-id="1460185266-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">hello</span></code></pre><p>See also <a href="#term_to_binary/1"><code class="inline">term_to_binary/1</code></a> and <a href="#binary_to_term/2"><code class="inline">binary_to_term/2</code></a>.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="binary_to_term/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#binary_to_term/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -7972,36 +7972,36 @@
│ │ │  Always validate data from untrusted sources. If a binary is stored or
│ │ │  transmitted through untrusted sources, consider cryptographically signing it.</p></section><h2 id="binary_to_term/2-examples" class="section-heading">
│ │ │    <a href="#binary_to_term/2-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3163045916-1">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">119</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="s">&quot;tjenixen&quot;</span><span class="p" data-group-id="3163045916-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">binary_to_term</span><span class="p" data-group-id="3163045916-2">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163045916-3">[</span><span class="ss">safe</span><span class="p" data-group-id="3163045916-3">]</span><span class="p" data-group-id="3163045916-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1820825010-1">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">119</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="s">&quot;tjenixen&quot;</span><span class="p" data-group-id="1820825010-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">binary_to_term</span><span class="p" data-group-id="1820825010-2">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1820825010-3">[</span><span class="ss">safe</span><span class="p" data-group-id="1820825010-3">]</span><span class="p" data-group-id="1820825010-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: bad argument
│ │ │       in function  binary_to_term/2
│ │ │          called as binary_to_term(&lt;&lt;131,119,8,116,106,101,110,105,120,101,110&gt;&gt;,[safe])
│ │ │          *** argument 1: invalid or unsafe external representation of a term</span><span class="w">
│ │ │  </span><span class="gp unselectable">3&gt; </span><span class="ss">tjenixen</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">tjenixen</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="nf">binary_to_term</span><span class="p" data-group-id="3163045916-4">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163045916-5">[</span><span class="ss">safe</span><span class="p" data-group-id="3163045916-5">]</span><span class="p" data-group-id="3163045916-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="nf">binary_to_term</span><span class="p" data-group-id="1820825010-4">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1820825010-5">[</span><span class="ss">safe</span><span class="p" data-group-id="1820825010-5">]</span><span class="p" data-group-id="1820825010-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">tjenixen</span></code></pre></li><li><p><strong><code class="inline">used</code></strong> - Changes the return value to <code class="inline">{Term, Used}</code> where <code class="inline">Used</code> is the
│ │ │  number of bytes actually read from <code class="inline">Binary</code>.</p><h2 id="binary_to_term/2-examples-1" class="section-heading">
│ │ │    <a href="#binary_to_term/2-examples-1" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Input</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4590687724-1">&lt;&lt;</span><span class="p" data-group-id="4590687724-2">(</span><span class="nf">term_to_binary</span><span class="p" data-group-id="4590687724-3">(</span><span class="ss">hello</span><span class="p" data-group-id="4590687724-3">)</span><span class="p" data-group-id="4590687724-2">)</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;world&quot;</span><span class="p" data-group-id="4590687724-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4590687724-4">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">119</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p">,</span><span class="mi">119</span><span class="p">,</span><span class="mi">111</span><span class="p">,</span><span class="mi">114</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">100</span><span class="p" data-group-id="4590687724-4">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="4590687724-5">{</span><span class="n">Term</span><span class="p">,</span><span class="w"> </span><span class="n">Used</span><span class="p" data-group-id="4590687724-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="4590687724-6">(</span><span class="n">Input</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4590687724-7">[</span><span class="ss">used</span><span class="p" data-group-id="4590687724-7">]</span><span class="p" data-group-id="4590687724-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4590687724-8">{</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">8</span><span class="p" data-group-id="4590687724-8">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">split_binary</span><span class="p" data-group-id="4590687724-9">(</span><span class="n">Input</span><span class="p">,</span><span class="w"> </span><span class="n">Used</span><span class="p" data-group-id="4590687724-9">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4590687724-10">{</span><span class="p" data-group-id="4590687724-11">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">119</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="4590687724-11">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4590687724-12">&lt;&lt;</span><span class="s">&quot;world&quot;</span><span class="p" data-group-id="4590687724-12">&gt;&gt;</span><span class="p" data-group-id="4590687724-10">}</span></code></pre></li></ul><p>Failure: <code class="inline">badarg</code> if <code class="inline">safe</code> is specified and unsafe data is decoded.</p><p>See also <a href="#term_to_binary/1"><code class="inline">term_to_binary/1</code></a>, <a href="#binary_to_term/1"><code class="inline">binary_to_term/1</code></a>, and <a href="#list_to_existing_atom/1"><code class="inline">list_to_existing_atom/1</code></a>.</p>
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Input</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7629662911-1">&lt;&lt;</span><span class="p" data-group-id="7629662911-2">(</span><span class="nf">term_to_binary</span><span class="p" data-group-id="7629662911-3">(</span><span class="ss">hello</span><span class="p" data-group-id="7629662911-3">)</span><span class="p" data-group-id="7629662911-2">)</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;world&quot;</span><span class="p" data-group-id="7629662911-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7629662911-4">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">119</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p">,</span><span class="mi">119</span><span class="p">,</span><span class="mi">111</span><span class="p">,</span><span class="mi">114</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">100</span><span class="p" data-group-id="7629662911-4">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="7629662911-5">{</span><span class="n">Term</span><span class="p">,</span><span class="w"> </span><span class="n">Used</span><span class="p" data-group-id="7629662911-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="7629662911-6">(</span><span class="n">Input</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7629662911-7">[</span><span class="ss">used</span><span class="p" data-group-id="7629662911-7">]</span><span class="p" data-group-id="7629662911-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7629662911-8">{</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">8</span><span class="p" data-group-id="7629662911-8">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">split_binary</span><span class="p" data-group-id="7629662911-9">(</span><span class="n">Input</span><span class="p">,</span><span class="w"> </span><span class="n">Used</span><span class="p" data-group-id="7629662911-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7629662911-10">{</span><span class="p" data-group-id="7629662911-11">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">119</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="7629662911-11">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7629662911-12">&lt;&lt;</span><span class="s">&quot;world&quot;</span><span class="p" data-group-id="7629662911-12">&gt;&gt;</span><span class="p" data-group-id="7629662911-10">}</span></code></pre></li></ul><p>Failure: <code class="inline">badarg</code> if <code class="inline">safe</code> is specified and unsafe data is decoded.</p><p>See also <a href="#term_to_binary/1"><code class="inline">term_to_binary/1</code></a>, <a href="#binary_to_term/1"><code class="inline">binary_to_term/1</code></a>, and <a href="#list_to_existing_atom/1"><code class="inline">list_to_existing_atom/1</code></a>.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="bit_size/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#bit_size/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -8029,17 +8029,17 @@
│ │ │  
│ │ │  <p>Returns an integer that is the size in bits of <code class="inline">Bitstring</code>.</p><h2 id="bit_size/1-examples" class="section-heading">
│ │ │    <a href="#bit_size/1-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">bit_size</span><span class="p" data-group-id="8680810138-1">(</span><span class="p" data-group-id="8680810138-2">&lt;&lt;</span><span class="mi">433</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="mi">3</span><span class="p">:</span><span class="mi">3</span><span class="p" data-group-id="8680810138-2">&gt;&gt;</span><span class="p" data-group-id="8680810138-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">bit_size</span><span class="p" data-group-id="0104438513-1">(</span><span class="p" data-group-id="0104438513-2">&lt;&lt;</span><span class="mi">433</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="mi">3</span><span class="p">:</span><span class="mi">3</span><span class="p" data-group-id="0104438513-2">&gt;&gt;</span><span class="p" data-group-id="0104438513-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">19</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">bit_size</span><span class="p" data-group-id="8680810138-3">(</span><span class="p" data-group-id="8680810138-4">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8680810138-4">&gt;&gt;</span><span class="p" data-group-id="8680810138-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">bit_size</span><span class="p" data-group-id="0104438513-3">(</span><span class="p" data-group-id="0104438513-4">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0104438513-4">&gt;&gt;</span><span class="p" data-group-id="0104438513-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">24</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="bitstring_to_list/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#bitstring_to_list/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -8067,18 +8067,18 @@
│ │ │  <p>Returns a list of integers corresponding to the bytes of <code class="inline">Bitstring</code>.</p><p>If the number of bits in the binary is not a multiple of 8, the last element of
│ │ │  the list is a bitstring containing the remaining 1 to 7 bits.</p><h2 id="bitstring_to_list/1-examples" class="section-heading">
│ │ │    <a href="#bitstring_to_list/1-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">bitstring_to_list</span><span class="p" data-group-id="9951003071-1">(</span><span class="p" data-group-id="9951003071-2">&lt;&lt;</span><span class="mi">433</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9951003071-2">&gt;&gt;</span><span class="p" data-group-id="9951003071-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9951003071-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">177</span><span class="p" data-group-id="9951003071-3">]</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">bitstring_to_list</span><span class="p" data-group-id="9951003071-4">(</span><span class="p" data-group-id="9951003071-5">&lt;&lt;</span><span class="mi">433</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="mi">3</span><span class="p">:</span><span class="mi">3</span><span class="p" data-group-id="9951003071-5">&gt;&gt;</span><span class="p" data-group-id="9951003071-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9951003071-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">177</span><span class="p">,</span><span class="p" data-group-id="9951003071-7">&lt;&lt;</span><span class="mi">3</span><span class="p">:</span><span class="mi">3</span><span class="p" data-group-id="9951003071-7">&gt;&gt;</span><span class="p" data-group-id="9951003071-6">]</span></code></pre>
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">bitstring_to_list</span><span class="p" data-group-id="8000344237-1">(</span><span class="p" data-group-id="8000344237-2">&lt;&lt;</span><span class="mi">433</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="8000344237-2">&gt;&gt;</span><span class="p" data-group-id="8000344237-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8000344237-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">177</span><span class="p" data-group-id="8000344237-3">]</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">bitstring_to_list</span><span class="p" data-group-id="8000344237-4">(</span><span class="p" data-group-id="8000344237-5">&lt;&lt;</span><span class="mi">433</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="mi">3</span><span class="p">:</span><span class="mi">3</span><span class="p" data-group-id="8000344237-5">&gt;&gt;</span><span class="p" data-group-id="8000344237-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8000344237-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">177</span><span class="p">,</span><span class="p" data-group-id="8000344237-7">&lt;&lt;</span><span class="mi">3</span><span class="p">:</span><span class="mi">3</span><span class="p" data-group-id="8000344237-7">&gt;&gt;</span><span class="p" data-group-id="8000344237-6">]</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="bump_reductions/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#bump_reductions/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -8137,17 +8137,17 @@
│ │ │  <p>Returns an integer that is the number of bytes needed to contain <code class="inline">Bitstring</code>.</p><p>If the number of bits in <code class="inline">Bitstring</code> is not a multiple of 8, the
│ │ │  result is rounded <strong>up</strong>.</p><h2 id="byte_size/1-examples" class="section-heading">
│ │ │    <a href="#byte_size/1-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">byte_size</span><span class="p" data-group-id="0260560589-1">(</span><span class="p" data-group-id="0260560589-2">&lt;&lt;</span><span class="mi">433</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="mi">3</span><span class="p">:</span><span class="mi">3</span><span class="p" data-group-id="0260560589-2">&gt;&gt;</span><span class="p" data-group-id="0260560589-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">byte_size</span><span class="p" data-group-id="2751870498-1">(</span><span class="p" data-group-id="2751870498-2">&lt;&lt;</span><span class="mi">433</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="mi">3</span><span class="p">:</span><span class="mi">3</span><span class="p" data-group-id="2751870498-2">&gt;&gt;</span><span class="p" data-group-id="2751870498-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">byte_size</span><span class="p" data-group-id="0260560589-3">(</span><span class="p" data-group-id="0260560589-4">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0260560589-4">&gt;&gt;</span><span class="p" data-group-id="0260560589-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">byte_size</span><span class="p" data-group-id="2751870498-3">(</span><span class="p" data-group-id="2751870498-4">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="2751870498-4">&gt;&gt;</span><span class="p" data-group-id="2751870498-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="cancel_timer/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#cancel_timer/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -8267,19 +8267,19 @@
│ │ │  
│ │ │  <p>Returns the smallest integer not less than <code class="inline">Number</code>.</p><p>See also <a href="#trunc/1"><code class="inline">trunc/1</code></a>.</p><h2 id="ceil/1-examples" class="section-heading">
│ │ │    <a href="#ceil/1-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">ceil</span><span class="p" data-group-id="3368774028-1">(</span><span class="mf">5.5</span><span class="p" data-group-id="3368774028-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">ceil</span><span class="p" data-group-id="6362077433-1">(</span><span class="mf">5.5</span><span class="p" data-group-id="6362077433-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">6</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">ceil</span><span class="p" data-group-id="3368774028-2">(</span><span class="o">-</span><span class="mf">2.3</span><span class="p" data-group-id="3368774028-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">ceil</span><span class="p" data-group-id="6362077433-2">(</span><span class="o">-</span><span class="mf">2.3</span><span class="p" data-group-id="6362077433-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">-</span><span class="mi">2</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">ceil</span><span class="p" data-group-id="3368774028-3">(</span><span class="mf">10.0</span><span class="p" data-group-id="3368774028-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">ceil</span><span class="p" data-group-id="6362077433-3">(</span><span class="mf">10.0</span><span class="p" data-group-id="6362077433-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">10</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="check_old_code/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#check_old_code/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -8468,15 +8468,15 @@
│ │ │  <p>Computes and returns the crc32 (IEEE 802.3 style) checksum for <code class="inline">Data</code>.</p><h2 id="crc32/1-examples" class="section-heading">
│ │ │    <a href="#crc32/1-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples:</span>
│ │ │  </h2>
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;abc&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="1916261822-1">(</span><span class="n">Data</span><span class="p" data-group-id="1916261822-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="4608732369-1">(</span><span class="n">Data</span><span class="p" data-group-id="4608732369-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">891568578</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="crc32/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#crc32/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -8497,19 +8497,19 @@
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> crc32(OldCrc, Data) -> <a href="#t:non_neg_integer/0">non_neg_integer</a>() when OldCrc :: <a href="#t:non_neg_integer/0">non_neg_integer</a>(), Data :: <a href="#t:iodata/0">iodata</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Continues computing the crc32 checksum by combining the previous checksum,
│ │ │  <code class="inline">OldCrc</code>, with the checksum of <code class="inline">Data</code>.</p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Data1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;abc&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Data2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;def&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="8120989281-1">(</span><span class="n">Data1</span><span class="p" data-group-id="8120989281-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="7027824830-1">(</span><span class="n">Data1</span><span class="p" data-group-id="7027824830-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">891568578</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="8120989281-2">(</span><span class="n">X</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="8120989281-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="7027824830-2">(</span><span class="n">X</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="7027824830-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">1267612143</span></code></pre><p>assigns the same value to <code class="inline">Y</code> as this:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Data1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;abc&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Data2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;def&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="9834201571-1">(</span><span class="p" data-group-id="9834201571-2">[</span><span class="n">Data1</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="9834201571-2">]</span><span class="p" data-group-id="9834201571-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="7802060471-1">(</span><span class="p" data-group-id="7802060471-2">[</span><span class="n">Data1</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="7802060471-2">]</span><span class="p" data-group-id="7802060471-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">1267612143</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="crc32_combine/3">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#crc32_combine/3" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -8534,23 +8534,23 @@
│ │ │                             SecondCrc :: <a href="#t:non_neg_integer/0">non_neg_integer</a>(),
│ │ │                             SecondSize :: <a href="#t:non_neg_integer/0">non_neg_integer</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Combines two previously computed crc32 checksums.</p><p>This computation requires the size of the data object for the second checksum
│ │ │  to be known.</p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Data1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;abc&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Data2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;def&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="9729831558-1">(</span><span class="n">Data1</span><span class="p" data-group-id="9729831558-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="3143786985-1">(</span><span class="n">Data1</span><span class="p" data-group-id="3143786985-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">891568578</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="9729831558-2">(</span><span class="n">X</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="9729831558-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="3143786985-2">(</span><span class="n">X</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="3143786985-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">1267612143</span></code></pre><p>assigns the same value to <code class="inline">Z</code> as this:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Data1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;abc&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Data2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">~&quot;def&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="5817620664-1">(</span><span class="n">Data1</span><span class="p" data-group-id="5817620664-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="8445452369-1">(</span><span class="n">Data1</span><span class="p" data-group-id="8445452369-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">891568578</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="5817620664-2">(</span><span class="n">Data2</span><span class="p" data-group-id="5817620664-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="8445452369-2">(</span><span class="n">Data2</span><span class="p" data-group-id="8445452369-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">214229345</span><span class="w">
│ │ │ -</span><span class="gp unselectable">4&gt; </span><span class="n">Z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32_combine</span><span class="p" data-group-id="5817620664-3">(</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="nf">iolist_size</span><span class="p" data-group-id="5817620664-4">(</span><span class="n">Data2</span><span class="p" data-group-id="5817620664-4">)</span><span class="p" data-group-id="5817620664-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">4&gt; </span><span class="n">Z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32_combine</span><span class="p" data-group-id="8445452369-3">(</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="nf">iolist_size</span><span class="p" data-group-id="8445452369-4">(</span><span class="n">Data2</span><span class="p" data-group-id="8445452369-4">)</span><span class="p" data-group-id="8445452369-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">1267612143</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="date/0">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#date/0" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -8573,16 +8573,16 @@
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> date() -> Date when Date :: <a href="../../../lib/stdlib-8.0/doc/html/calendar.html#t:date/0">calendar:date</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns the current date as <code class="inline">{Year, Month, Day}</code>.</p><p>The time zone and Daylight Saving Time correction depend on the underlying OS.
│ │ │  The return value is based on the
│ │ │ -<a href="time_correction.html#os-system-time">OS System Time</a>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">date</span><span class="p" data-group-id="0815237725-1">(</span><span class="p" data-group-id="0815237725-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0815237725-2">{</span><span class="mi">1995</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">19</span><span class="p" data-group-id="0815237725-2">}</span></code></pre>
│ │ │ +<a href="time_correction.html#os-system-time">OS System Time</a>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">date</span><span class="p" data-group-id="1495521074-1">(</span><span class="p" data-group-id="1495521074-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1495521074-2">{</span><span class="mi">1995</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">19</span><span class="p" data-group-id="1495521074-2">}</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="decode_packet/3">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#decode_packet/3" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -8687,18 +8687,18 @@
│ │ │  intended for backward compatibility.</p></li><li><p><strong><code class="inline">{line_delimiter, 0 =&lt; byte() =&lt; 255}</code></strong> - For packet type <code class="inline">line</code>, sets the
│ │ │  delimiting byte. Default is the latin-1 character <code class="inline">$\n</code>.</p></li></ul><h2 id="decode_packet/3-examples" class="section-heading">
│ │ │    <a href="#decode_packet/3-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">decode_packet</span><span class="p" data-group-id="7838610315-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7838610315-2">&lt;&lt;</span><span class="mi">3</span><span class="p">,</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="7838610315-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7838610315-3">[</span><span class="p" data-group-id="7838610315-3">]</span><span class="p" data-group-id="7838610315-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7838610315-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="7838610315-5">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="7838610315-5">&gt;&gt;</span><span class="p">,</span><span class="p" data-group-id="7838610315-6">&lt;&lt;</span><span class="s">&quot;d&quot;</span><span class="p" data-group-id="7838610315-6">&gt;&gt;</span><span class="p" data-group-id="7838610315-4">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">decode_packet</span><span class="p" data-group-id="7838610315-7">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7838610315-8">&lt;&lt;</span><span class="mi">5</span><span class="p">,</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="7838610315-8">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7838610315-9">[</span><span class="p" data-group-id="7838610315-9">]</span><span class="p" data-group-id="7838610315-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7838610315-10">{</span><span class="ss">more</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7838610315-10">}</span></code></pre>
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">decode_packet</span><span class="p" data-group-id="2594809797-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2594809797-2">&lt;&lt;</span><span class="mi">3</span><span class="p">,</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="2594809797-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2594809797-3">[</span><span class="p" data-group-id="2594809797-3">]</span><span class="p" data-group-id="2594809797-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2594809797-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="2594809797-5">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="2594809797-5">&gt;&gt;</span><span class="p">,</span><span class="p" data-group-id="2594809797-6">&lt;&lt;</span><span class="s">&quot;d&quot;</span><span class="p" data-group-id="2594809797-6">&gt;&gt;</span><span class="p" data-group-id="2594809797-4">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">decode_packet</span><span class="p" data-group-id="2594809797-7">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2594809797-8">&lt;&lt;</span><span class="mi">5</span><span class="p">,</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="2594809797-8">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2594809797-9">[</span><span class="p" data-group-id="2594809797-9">]</span><span class="p" data-group-id="2594809797-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2594809797-10">{</span><span class="ss">more</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2594809797-10">}</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="delete_element/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#delete_element/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -8725,16 +8725,16 @@
│ │ │  
│ │ │  <p>Returns a new tuple with element at <code class="inline">Index</code> removed from tuple <code class="inline">Tuple1</code>.</p><h2 id="delete_element/2-examples" class="section-heading">
│ │ │    <a href="#delete_element/2-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">delete_element</span><span class="p" data-group-id="6750103897-1">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6750103897-2">{</span><span class="ss">one</span><span class="p">,</span><span class="w"> </span><span class="ss">two</span><span class="p">,</span><span class="w"> </span><span class="ss">three</span><span class="p" data-group-id="6750103897-2">}</span><span class="p" data-group-id="6750103897-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6750103897-3">{</span><span class="ss">one</span><span class="p">,</span><span class="ss">three</span><span class="p" data-group-id="6750103897-3">}</span></code></pre>
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">delete_element</span><span class="p" data-group-id="4591696071-1">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4591696071-2">{</span><span class="ss">one</span><span class="p">,</span><span class="w"> </span><span class="ss">two</span><span class="p">,</span><span class="w"> </span><span class="ss">three</span><span class="p" data-group-id="4591696071-2">}</span><span class="p" data-group-id="4591696071-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4591696071-3">{</span><span class="ss">one</span><span class="p">,</span><span class="ss">three</span><span class="p" data-group-id="4591696071-3">}</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="delete_module/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#delete_module/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -8836,17 +8836,17 @@
│ │ │                     when MonitorRef :: <a href="#t:reference/0">reference</a>(), OptionList :: [Option], Option :: flush | info.</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>The returned value is <code class="inline">true</code> unless <code class="inline">info</code> is part of <code class="inline">OptionList</code>.</p><p><a href="#demonitor/2"><code class="inline">demonitor(MonitorRef, [])</code></a> is equivalent to
│ │ │  <a href="#demonitor/1"><code class="inline">demonitor(MonitorRef)</code></a>.</p><p><code class="inline">Option</code>s:</p><ul><li><p><strong><code class="inline">flush</code></strong> - Removes (one) <code class="inline">{_, MonitorRef, _, _, _}</code> message, if there is
│ │ │  one, from the caller message queue after monitoring has been stopped.</p><p>Calling <a href="#demonitor/2"><code class="inline">demonitor(MonitorRef, [flush])</code></a> is equivalent to the
│ │ │ -following, but more efficient:</p><pre><code class="makeup erlang" translate="no"><span class="nf">demonitor</span><span class="p" data-group-id="7749918645-1">(</span><span class="n">MonitorRef</span><span class="p" data-group-id="7749918645-1">)</span><span class="p">,</span><span class="w">
│ │ │ +following, but more efficient:</p><pre><code class="makeup erlang" translate="no"><span class="nf">demonitor</span><span class="p" data-group-id="1939170873-1">(</span><span class="n">MonitorRef</span><span class="p" data-group-id="1939170873-1">)</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7749918645-2">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">MonitorRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7749918645-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1939170873-2">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">MonitorRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="1939170873-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w">
│ │ │  </span><span class="k">after</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre></li><li><p><strong><code class="inline">info</code></strong> - The returned value is one of the following:</p><ul><li><p><strong><code class="inline">true</code></strong> - The monitor was found and removed. In this case, no <code class="inline">'DOWN'</code>
│ │ │  message corresponding to this monitor has been delivered and will not be
│ │ │  delivered.</p></li><li><p><strong><code class="inline">false</code></strong> - The monitor was not found and could not be removed. This
│ │ │  probably because someone already has placed a <code class="inline">'DOWN'</code> message corresponding
│ │ │ @@ -9178,15 +9178,15 @@
│ │ │  
│ │ │  <p>Returns the <code class="inline">N</code>th element (numbering from 1) of <code class="inline">Tuple</code>.</p><h2 id="element/2-examples" class="section-heading">
│ │ │    <a href="#element/2-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">element</span><span class="p" data-group-id="0004220309-1">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0004220309-2">{</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="0004220309-2">}</span><span class="p" data-group-id="0004220309-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">element</span><span class="p" data-group-id="3521246376-1">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3521246376-2">{</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="3521246376-2">}</span><span class="p" data-group-id="3521246376-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">b</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="erase/0">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#erase/0" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -9207,18 +9207,18 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> erase() -> [{Key, Val}] when Key :: <a href="#t:term/0">term</a>(), Val :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns the process dictionary and deletes it.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">put</span><span class="p" data-group-id="5898452770-1">(</span><span class="ss">key1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5898452770-2">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="5898452770-2">}</span><span class="p" data-group-id="5898452770-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nf">put</span><span class="p" data-group-id="5898452770-3">(</span><span class="ss">key2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5898452770-4">[</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="5898452770-4">]</span><span class="p" data-group-id="5898452770-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">sort</span><span class="p" data-group-id="5898452770-5">(</span><span class="nf">erase</span><span class="p" data-group-id="5898452770-6">(</span><span class="p" data-group-id="5898452770-6">)</span><span class="p" data-group-id="5898452770-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5898452770-7">[</span><span class="p" data-group-id="5898452770-8">{</span><span class="ss">key1</span><span class="p">,</span><span class="p" data-group-id="5898452770-9">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5898452770-9">}</span><span class="p" data-group-id="5898452770-8">}</span><span class="p">,</span><span class="p" data-group-id="5898452770-10">{</span><span class="ss">key2</span><span class="p">,</span><span class="p" data-group-id="5898452770-11">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5898452770-11">]</span><span class="p" data-group-id="5898452770-10">}</span><span class="p" data-group-id="5898452770-7">]</span></code></pre>
│ │ │ +<p>Returns the process dictionary and deletes it.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">put</span><span class="p" data-group-id="5367208863-1">(</span><span class="ss">key1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5367208863-2">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="5367208863-2">}</span><span class="p" data-group-id="5367208863-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nf">put</span><span class="p" data-group-id="5367208863-3">(</span><span class="ss">key2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5367208863-4">[</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="5367208863-4">]</span><span class="p" data-group-id="5367208863-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">sort</span><span class="p" data-group-id="5367208863-5">(</span><span class="nf">erase</span><span class="p" data-group-id="5367208863-6">(</span><span class="p" data-group-id="5367208863-6">)</span><span class="p" data-group-id="5367208863-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5367208863-7">[</span><span class="p" data-group-id="5367208863-8">{</span><span class="ss">key1</span><span class="p">,</span><span class="p" data-group-id="5367208863-9">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5367208863-9">}</span><span class="p" data-group-id="5367208863-8">}</span><span class="p">,</span><span class="p" data-group-id="5367208863-10">{</span><span class="ss">key2</span><span class="p">,</span><span class="p" data-group-id="5367208863-11">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5367208863-11">]</span><span class="p" data-group-id="5367208863-10">}</span><span class="p" data-group-id="5367208863-7">]</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="erase/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#erase/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -9241,18 +9241,18 @@
│ │ │            <pre translate="no"><span class="attribute">-spec</span> erase(Key) -> Val | undefined when Key :: <a href="#t:term/0">term</a>(), Val :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns the value <code class="inline">Val</code> associated with <code class="inline">Key</code> and deletes it from the process
│ │ │  dictionary. Returns <code class="inline">undefined</code> if no value is associated with <code class="inline">Key</code>.</p><p>The average time complexity for the current implementation of this function is
│ │ │  O(<code class="inline">1</code>) and the worst case time complexity is O(<code class="inline">N</code>), where <code class="inline">N</code> is the number of
│ │ │ -items in the process dictionary.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">put</span><span class="p" data-group-id="3227653619-1">(</span><span class="ss">key1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3227653619-2">{</span><span class="ss">merry</span><span class="p">,</span><span class="w"> </span><span class="ss">lambs</span><span class="p">,</span><span class="w"> </span><span class="ss">are</span><span class="p">,</span><span class="w"> </span><span class="ss">playing</span><span class="p" data-group-id="3227653619-2">}</span><span class="p" data-group-id="3227653619-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erase</span><span class="p" data-group-id="3227653619-3">(</span><span class="ss">key1</span><span class="p" data-group-id="3227653619-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3227653619-4">{</span><span class="ss">merry</span><span class="p">,</span><span class="ss">lambs</span><span class="p">,</span><span class="ss">are</span><span class="p">,</span><span class="ss">playing</span><span class="p" data-group-id="3227653619-4">}</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">erase</span><span class="p" data-group-id="3227653619-5">(</span><span class="ss">key1</span><span class="p" data-group-id="3227653619-5">)</span><span class="p">.</span><span class="w">
│ │ │ +items in the process dictionary.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">put</span><span class="p" data-group-id="9106562368-1">(</span><span class="ss">key1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9106562368-2">{</span><span class="ss">merry</span><span class="p">,</span><span class="w"> </span><span class="ss">lambs</span><span class="p">,</span><span class="w"> </span><span class="ss">are</span><span class="p">,</span><span class="w"> </span><span class="ss">playing</span><span class="p" data-group-id="9106562368-2">}</span><span class="p" data-group-id="9106562368-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erase</span><span class="p" data-group-id="9106562368-3">(</span><span class="ss">key1</span><span class="p" data-group-id="9106562368-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9106562368-4">{</span><span class="ss">merry</span><span class="p">,</span><span class="ss">lambs</span><span class="p">,</span><span class="ss">are</span><span class="p">,</span><span class="ss">playing</span><span class="p" data-group-id="9106562368-4">}</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">erase</span><span class="p" data-group-id="9106562368-5">(</span><span class="ss">key1</span><span class="p" data-group-id="9106562368-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">undefined</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="error/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#error/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -9277,16 +9277,16 @@
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Raises an exception of class <code class="inline">error</code> with the reason <code class="inline">Reason</code>.</p><p>As evaluating this function causes an exception to be thrown, it has no return value.</p><p>The intent of the exception class <code class="inline">error</code> is to signal that an unexpected error
│ │ │  has happened (for example, a function is called with a parameter that has an
│ │ │  incorrect type). See the guide about
│ │ │  <a href="../../../doc/system/errors.html">errors and error handling</a> for additional information.
│ │ │ -Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">error</span><span class="p" data-group-id="8750202022-1">(</span><span class="ss">foobar</span><span class="p" data-group-id="8750202022-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8750202022-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="8750202022-3">{</span><span class="ss">foobar</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">StackTrace</span><span class="p" data-group-id="8750202022-3">}</span><span class="p" data-group-id="8750202022-2">}</span></code></pre>
│ │ │ +Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">error</span><span class="p" data-group-id="8652931190-1">(</span><span class="ss">foobar</span><span class="p" data-group-id="8652931190-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8652931190-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="8652931190-3">{</span><span class="ss">foobar</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">StackTrace</span><span class="p" data-group-id="8652931190-3">}</span><span class="p" data-group-id="8652931190-2">}</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="error/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#error/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -9320,19 +9320,19 @@
│ │ │  incorrect type). See the guide about
│ │ │  <a href="../../../doc/system/errors.html">errors and error handling</a> for additional information.</p><h2 id="error/2-examples" class="section-heading">
│ │ │    <a href="#error/2-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<p><code class="inline">test.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7456406935-1">(</span><span class="ss">test</span><span class="p" data-group-id="7456406935-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7456406935-2">(</span><span class="p" data-group-id="7456406935-3">[</span><span class="ss">example_fun</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7456406935-3">]</span><span class="p" data-group-id="7456406935-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<p><code class="inline">test.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6415144204-1">(</span><span class="ss">test</span><span class="p" data-group-id="6415144204-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6415144204-2">(</span><span class="p" data-group-id="6415144204-3">[</span><span class="ss">example_fun</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6415144204-3">]</span><span class="p" data-group-id="6415144204-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">example_fun</span><span class="p" data-group-id="7456406935-4">(</span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="n">A2</span><span class="p" data-group-id="7456406935-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">error</span><span class="p" data-group-id="7456406935-5">(</span><span class="ss">my_error</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7456406935-6">[</span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="n">A2</span><span class="p" data-group-id="7456406935-6">]</span><span class="p" data-group-id="7456406935-5">)</span><span class="p">.</span></code></pre><p>Erlang shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">test</span><span class="p">:</span><span class="nf">example_fun</span><span class="p" data-group-id="8661240123-1">(</span><span class="ss">arg1</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;this is the second argument&quot;</span><span class="p" data-group-id="8661240123-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">example_fun</span><span class="p" data-group-id="6415144204-4">(</span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="n">A2</span><span class="p" data-group-id="6415144204-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">error</span><span class="p" data-group-id="6415144204-5">(</span><span class="ss">my_error</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6415144204-6">[</span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="n">A2</span><span class="p" data-group-id="6415144204-6">]</span><span class="p" data-group-id="6415144204-5">)</span><span class="p">.</span></code></pre><p>Erlang shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">test</span><span class="p">:</span><span class="nf">example_fun</span><span class="p" data-group-id="9198512323-1">(</span><span class="ss">arg1</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;this is the second argument&quot;</span><span class="p" data-group-id="9198512323-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: my_error
│ │ │       in function  test:example_fun/2
│ │ │          called as test:example_fun(arg1,&quot;this is the second argument&quot;)</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="error/3">
│ │ │  
│ │ │ @@ -9409,18 +9409,18 @@
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Raises an exception of class <code class="inline">exit</code> with exit reason <code class="inline">Reason</code>.</p><p>As evaluating this function causes an exception to be raised, it has no return value.</p><p>The intent of the exception class <code class="inline">exit</code> is that the current process should be
│ │ │  stopped (for example when a message telling a process to stop is received).</p><p>This function differ from <a href="#error/1"><code class="inline">error/1,2,3</code></a> by causing an exception of
│ │ │  a different class and by having a reason that does not include the list of
│ │ │  functions from the call stack.</p><p>See the guide about <a href="../../../doc/system/errors.html">errors and error handling</a> for
│ │ │ -additional information.</p><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">exit</span><span class="p" data-group-id="1518417498-1">(</span><span class="ss">foobar</span><span class="p" data-group-id="1518417498-1">)</span><span class="p">.</span><span class="w">
│ │ │ +additional information.</p><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">exit</span><span class="p" data-group-id="1618628575-1">(</span><span class="ss">foobar</span><span class="p" data-group-id="1618628575-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception exit: foobar</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="1518417498-2">(</span><span class="ss">foobar</span><span class="p" data-group-id="1518417498-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1518417498-3">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="ss">foobar</span><span class="p" data-group-id="1518417498-3">}</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>If a process calls <a href="#exit/1"><code class="inline">exit(kill)</code></a> and does not catch the exception,
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="1618628575-2">(</span><span class="ss">foobar</span><span class="p" data-group-id="1618628575-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1618628575-3">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="ss">foobar</span><span class="p" data-group-id="1618628575-3">}</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>If a process calls <a href="#exit/1"><code class="inline">exit(kill)</code></a> and does not catch the exception,
│ │ │  it will terminate with exit reason <code class="inline">kill</code> and also emit exit signals with exit
│ │ │  reason <code class="inline">kill</code> (not <code class="inline">killed</code>) to all linked processes. Such exit signals with
│ │ │  exit reason <code class="inline">kill</code> can be trapped by the linked processes. Note that this
│ │ │  means that signals with exit reason <code class="inline">kill</code> behave differently depending on how
│ │ │  they are sent because the signal will be untrappable if a process sends such a
│ │ │  signal to another process with <a href="#exit_signal/2"><code class="inline">erlang:exit_signal/2</code></a>.</p></section>
│ │ │    </section>
│ │ │ @@ -9541,26 +9541,26 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> external_size(Term) -> <a href="#t:non_neg_integer/0">non_neg_integer</a>() when Term :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Calculates, without doing the encoding, the maximum byte size for a term encoded
│ │ │ -in the Erlang external term format.</p><p>The following condition applies always:</p><pre><code class="makeup erlang" translate="no"><span class="n">Size1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">byte_size</span><span class="p" data-group-id="8029816933-1">(</span><span class="nf">term_to_binary</span><span class="p" data-group-id="8029816933-2">(</span><span class="n">Term</span><span class="p" data-group-id="8029816933-2">)</span><span class="p" data-group-id="8029816933-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Size2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">external_size</span><span class="p" data-group-id="8029816933-3">(</span><span class="n">Term</span><span class="p" data-group-id="8029816933-3">)</span><span class="p">,</span><span class="w">
│ │ │ +in the Erlang external term format.</p><p>The following condition applies always:</p><pre><code class="makeup erlang" translate="no"><span class="n">Size1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">byte_size</span><span class="p" data-group-id="7226438590-1">(</span><span class="nf">term_to_binary</span><span class="p" data-group-id="7226438590-2">(</span><span class="n">Term</span><span class="p" data-group-id="7226438590-2">)</span><span class="p" data-group-id="7226438590-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Size2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">external_size</span><span class="p" data-group-id="7226438590-3">(</span><span class="n">Term</span><span class="p" data-group-id="7226438590-3">)</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Size1</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">Size2</span><span class="p">.</span></code></pre><h2 id="external_size/1-examples" class="section-heading">
│ │ │    <a href="#external_size/1-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Term</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5864283731-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="5864283731-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gp unselectable">2&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">external_size</span><span class="p" data-group-id="5864283731-2">(</span><span class="n">Term</span><span class="p" data-group-id="5864283731-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Term</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9222412187-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="9222412187-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">2&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">external_size</span><span class="p" data-group-id="9222412187-2">(</span><span class="n">Term</span><span class="p" data-group-id="9222412187-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">13</span><span class="w">
│ │ │ -</span><span class="gp unselectable">3&gt; </span><span class="nf">byte_size</span><span class="p" data-group-id="5864283731-3">(</span><span class="nf">term_to_binary</span><span class="p" data-group-id="5864283731-4">(</span><span class="n">Term</span><span class="p" data-group-id="5864283731-4">)</span><span class="p" data-group-id="5864283731-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gp unselectable">3&gt; </span><span class="nf">byte_size</span><span class="p" data-group-id="9222412187-3">(</span><span class="nf">term_to_binary</span><span class="p" data-group-id="9222412187-4">(</span><span class="n">Term</span><span class="p" data-group-id="9222412187-4">)</span><span class="p" data-group-id="9222412187-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">13</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="external_size/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#external_size/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -9590,27 +9590,27 @@
│ │ │                                  deterministic |
│ │ │                                  {minor_version, Version :: 0..2} |
│ │ │                                  local].</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Calculates, without doing the encoding, the maximum byte size for a term encoded
│ │ │ -in the Erlang external term format.</p><p>The following condition applies always:</p><pre><code class="makeup erlang" translate="no"><span class="n">Size1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">byte_size</span><span class="p" data-group-id="1273937971-1">(</span><span class="nf">term_to_binary</span><span class="p" data-group-id="1273937971-2">(</span><span class="n">Term</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="1273937971-2">)</span><span class="p" data-group-id="1273937971-1">)</span><span class="p">,</span><span class="w">
�

TRUNCATED DUE TO SIZE LIMIT: 10485760 bytes